Revel M106 Bookshelf Speaker Review

[Newman]

I always think of it this way: the optimal number and location of deep bass reproducers is not the same as the optimal number and location of mid-and-treble reproducers. So, any all-in-one speaker simply cannot be optimal.

 

[KaiserSoze]

I haven't switched context. If you think that, it's probably due to a failure to communicate clearly on my part. Just to be clear, when I'm talking about the benefits of multiple separate subs, I'm strictly speaking of situations where you have full control of where those subs will go. Otherwise, you might as well just attach them to the mains and live with the sound that results.

You posted a reply to something I wrote, which is perfectly okay, however it was a little odd, and I thought it appropriate to say so and explain why. It isn't worth further elaboration, however I would like very much for you to understand why I thought that what you wrote was a little odd. Admittedly I did a lousy job of explaining it (I really did), so I have to try again, and if I fail this time, I'll be content that I've given it my best try.

The comment of mine to which you replied was a reply to a comment made by Bear123, which he made in reply to one of my comments. I had written about difficulties that are due to the bass limitation of small speakers. He wrote that proper integration of a subwoofer is easy thanks to modern A/V receivers. I replied that he may have been just as happy with a pair of stereo speakers with powered subs built-in. My point, which I thought should have been readily apparent to anyone reading what I wrote, was that the absence of difficulty in integrating the sub is a moot advantage when the alternative setup against which the 2.1 setup is compared is a 2.0 system where the same quality of bass is achieved without any need to do any integration. Then you arrived and said in essence that stereo speakers with full-bass capability aren't any good because they don't allow the low-frequency drivers to be positioned for the best effect at mitigating standing waves and nulls within the room. That struck me as terribly peculiar, and still does, because I cannot understand what it is supposed to say about whether a subwoofer setup where integration is trivial is or isn't an advantage over a setup where no integration is needed.

I do not think you failed to communicate clearly. I do think that you did not bother to make an appropriate effort to understand what another person had said, and their reason for saying it.

I'm sure those are fantastic speakers. The problem is, sound quality at those frequencies isn't about the speakers, it's about the room, and the speakers position within that room. Remember, you're hearing the room, not the speakers. The speakers themselves are somewhat irrelevant. Once you have sufficient output, the best bass speaker will be the speaker with the most placement flexibility, hence why attached subs are at a huge disadvantage.

Ugh. First, I don't honestly don't give a crap because what you're saying has absolutely no bearing on the veracity of what I had written, as I explained above. Second, why would it be important for me to remember something that is patently absurd? You are in fact saying that the quality of deep bass in a room doesn't have anything to do with the speakers. To test your theory, you can remove your subwoofers from the room and then listen to see if this has any affect on the quality of the bass.

Now, that's not to say you can't get good bass out of full range towers, but it's gonna take a lot of luck(with the room), and a ton of EQ(which limits headroom). I can guarantee that those Mythos towers would have terrible bass, compared to what I have now with separate subs in two of my rooms.

I am very happy for you that you have two rooms with two subs in each room. But even if you had bought a pair of Mythos ST-L SuperTowers and placed them in one of your two rooms so that you could confirm for yourself that they don't compare to the setup you own, the likelihood is vanishingly small that you would be able to make an objective assessment of any difference in the sound quality.

By the way, I had hoped to avoid mention of this, but there is no way that your setup can possibly sound good, because good-sounding bass is only possible if the walls and the ceiling are completely covered with 18" subwoofers. As it would happen, this is what I have in each of two rooms, and I can guarantee you that the dual sub setup of yours has terrible bass, compared to what I have now with my walls and ceiling covered with 18" subwoofers in two of my rooms.

Not sure what point you think I was trying to make here. I'm not trying to obfuscate anything or be disingenuous. Can you quote the part of my text you thought was disingenuous? May have just been a mistake on my part.

I already stated what it was that you obfuscated, but I'll try again. By writing what you wrote in the context in which you wrote it, you obfuscated the fact that a setup with subwoofers incorporated into each of two stereo speakers has an advantage in mitigation of room modes, compared to a single-subwoofer setup. Given the particulars of the discussion you joined, it would have been fully appropriate for you to have made this point, but instead you made a point that didn't bear on anything that had been said and that had the actual effect of obfuscating the point that would have been appropriate for you to have made.

All other things held constant(usually price is something that's not) having real bass capability in your mains is always a positive. Not sure why you think I disagree with that.

It might have something to do with your having written, "In most rooms, subs need to be placed in different physical locations than the mains in order to sound good."

My point was simply that attached subs are "less good" than separate subs(with placement flexibility), but given the choice between full range mains and bookshelves, I'll always go for the full range mains(if everything else is the same).

Okay, but that's not really the same as what you previously wrote. And even given this statement which is much better, the point that you wanted to make and that you made has no bearing on anything that had been put into question in the discussion that preceded your having joined. But it doesn't matter. I thought it appropriate to point this out, but you did not understand it, so I tried again, and now that I have done my devil best at trying to make this understandable to you, I will say no more about it. Even if you reply to this by asserting the advantages of one type of amplifier vs. another.

 

[KaiserSoze]

I always think of it this way: the optimal number and location of deep bass reproducers is not the same as the optimal number and location of mid-and-treble reproducers. So, any all-in-one speaker simply cannot be optimal.

And no one here has claimed that an all-in-one speaker is "optimal". If it seemed to you that someone had made this claim, it is only because of what Richard12511 wrote. This is a perfect example of what I despise about web forums. One person says that it is hot outside. Another person joins and says that it can't be hot outside because the Sahara is where it is hot. A third person then joins and says that they have proof that it can't be hot outside because they have been to the Sahara and they know for a fact that the Sahara is where it is hot, not here.

 

[richard12511]

You posted a reply to something I wrote, which is perfectly okay, however it was a little odd, and I thought it appropriate to say so and explain why. It isn't worth further elaboration, however I would like very much for you to understand why I thought that what you wrote was a little odd. Admittedly I did a lousy job of explaining it (I really did), so I have to try again, and if I fail this time, I'll be content that I've given it my best try.

The comment of mine to which you replied was a reply to a comment made by Bear123, which he made in reply to one of my comments. I had written about difficulties that are due to the bass limitation of small speakers. He wrote that proper integration of a subwoofer is easy thanks to modern A/V receivers. I replied that he may have been just as happy with a pair of stereo speakers with powered subs built-in. My point, which I thought should have been readily apparent to anyone reading what I wrote, was that the absence of difficulty in integrating the sub is a moot advantage when the alternative setup against which the 2.1 setup is compared is a 2.0 system where the same quality of bass is achieved without any need to do any integration. Then you arrived and said in essence that stereo speakers with full-bass capability aren't any good because they don't allow the low-frequency drivers to be positioned for the best effect at mitigating standing waves and nulls within the room. That struck me as terribly peculiar, and still does, because I cannot understand what it is supposed to say about whether a subwoofer setup where integration is trivial is or isn't an advantage over a setup where no integration is needed.

I do not think you failed to communicate clearly. I do think that you did not bother to make an appropriate effort to understand what another person had said, and their reason for saying it.



Ugh. First, I don't honestly don't give a crap because what you're saying has absolutely no bearing on the veracity of what I had written, as I explained above. Second, why would it be important for me to remember something that is patently absurd? You are in fact saying that the quality of deep bass in a room doesn't have anything to do with the speakers. To test your theory, you can remove your subwoofers from the room and then listen to see if this has any affect on the quality of the bass.



I am very happy for you that you have two rooms with two subs in each room. But even if you had bought a pair of Mythos ST-L SuperTowers and placed them in one of your two rooms so that you could confirm for yourself that they don't compare to the setup you own, the likelihood is vanishingly small that you would be able to make an objective assessment of any difference in the sound quality.

By the way, I had hoped to avoid mention of this, but there is no way that your setup can possibly sound good, because good-sounding bass is only possible if the walls and the ceiling are completely covered with 18" subwoofers. As it would happen, this is what I have in each of two rooms, and I can guarantee you that the dual sub setup of yours has terrible bass, compared to what I have now with my walls and ceiling covered with 18" subwoofers in two of my rooms.



I already stated what it was that you obfuscated, but I'll try again. By writing what you wrote in the context in which you wrote it, you obfuscated the fact that a setup with subwoofers incorporated into each of two stereo speakers has an advantage in mitigation of room modes, compared to a single-subwoofer setup. Given the particulars of the discussion you joined, it would have been fully appropriate for you to have made this point, but instead you made a point that didn't bear on anything that had been said and that had the actual effect of obfuscating the point that would have been appropriate for you to have made.



It might have something to do with your having written, "In most rooms, subs need to be placed in different physical locations than the mains in order to sound good."



Okay, but that's not really the same as what you previously wrote. And even given this statement which is much better, the point that you wanted to make and that you made has no bearing on anything that had been put into question in the discussion that preceded your having joined. But it doesn't matter. I thought it appropriate to point this out, but you did not understand it, so I tried again, and now that I have done my devil best at trying to make this understandable to you, I will say no more about it. Even if you reply to this by asserting the advantages of one type of amplifier vs. another.

Yeah, it seems we just misunderstood each other. Probably my fault.

I never meant to imply that built in subs is a bad thing. Having them is definitely better than not having them. My only point was that it's less good than having separate subs that can be placed individually.

 

[Newman]

Excellent integration is easy so long as your main stereo speakers can play cleaning at adequate volume at the requisite low frequency.

And no one here has claimed that an all-in-one speaker is "optimal".

See your own words, above. The word 'optimal' is not necessary: it means much the same thing as "excellent integration" for the purpose of this particular discussion.

If it seemed to you that someone had made this claim, it is only because of what Richard12511 wrote. This is a perfect example of what I despise about web forums. One person says that it is hot outside. Another person joins and says that it can't be hot outside because the Sahara is where it is hot. A third person then joins and says that they have proof that it can't be hot outside because they have been to the Sahara and they know for a fact that the Sahara is where it is hot, not here.

You are thrashing around in a bear trap. You will gain respect if you give an inch. Specifically, stereo full-range main speakers will always have second-level bass, because they are restrained by being only two sources and in the wrong locations, no matter how well they are executed or equalized. Multi-subs can solve this and bring top-level bass.

cheers

 

[KaiserSoze]

Separate subs that can be placed in optimal locations will always achieve better sound quality, higher SPL capability, lower distortion, and lower extension. No matter how good, how large, and how low a speaker attempts to play, they are better with subs.

Fact is, if one is after the best sound quality possible, speakers crossed to good quality well placed subs is the most optimal solution. I wouldn't therefore waste money on "subwoofer" capability that is limited to the same placement as the speakers.

I suppose another way to look at it is, given the choice of tower speakers with solid 40 Hz extension that can be effectively crossed at 80 Hz to good subs, or tower speakers spec'd to 20 Hz extension but no subs, I'd gladly pass on the 20 Hz speakers.

The thing I don't understand about this is why it was posted as a reply to a post of mine. I think it is appropriate to run the instant replay to see how we ended up here.

I had posted a comment to the effect that it can be difficult to properly integrate a subwoofer to small bookshelf speakers with inadequate bass capability. You responded to that by saying that modern A/V receivers make it easy to integrate a subwoofer. Implicitly you argued that a modern A/V receiver can overcome the limitations of the small bookshelf speaker. It might not be apparent to you why this is implied by what you wrote, but the reason is that this is the only way it would have been logically sensible for you to have made that comment in reply to my lament about many speakers being too small for proper integration with a subwoofer.

For the life of me I do not know why I responded to your comment in the manner that I did. It was never my intent to advocate for stereo speakers with subwoofers built in. I merely meant to point out that the lack of difficulty you had with the integration of your subwoofer is not a lesser difficulty than the difficulty encountered by people who buy stereo speakers with built-in subwoofers. That's the full extent of what I intended to say, and presently I have no idea why I thought it appropriate to say that. I have since realized that I should have said something along the lines of, "A/V receivers do not make small speakers play lower or louder with lower distortion, and as such it is manifest that A/V receivers cannot possibly make it easy to properly integrate a sub with small speakers that lack adequate bass capability to properly integrate with a subwoofer."

But now that we are here, I want to say that the circumstances when purchases are made vary quite a bit, and that as such it is kind of silly to assert so boldly that it would be a waste of money for anyone to buy a pair of stereo speakers with subwoofers built in.

I want further to point again to two advantages of speakers of this variety, which advantages are absolutely real notwithstanding your lack of appreciation for them. The first advantage is that with this kind of speaker the low-frequency driver (that can be as good as any other at 30 Hz or wherever) can be well-suited to being operated into the midrange. This can be leveraged to make the higher-frequency drivers smaller than they would need to be if the largest among them were required to operate down to, say, 80 Hz. The use of smaller drivers leads to better directivity matching at each of the crossover points. The second advantage is with more efficient use of room space. This is an absolutely real advantage, that very many people understand perfectly well, even if they've only ever tired to figure out where to put a single subwoofer, much less two.

 

[Bear123]

I concede. If someone held a gun to my head and told me I couldn't use subwoofers but had to make due with only tower speakers that play low, then yes, I would take all the extension I could get.

My room isn't huge, its about 2525 ft^3. I somehow managed to use about 15 of those for a pair of good subs.

 

[KaiserSoze]

See your own words, above. The word 'optimal' is not necessary: it means much the same thing as "excellent integration" for the purpose of this particular discussion.

You are thrashing around in a bear trap. You will gain respect if you give an inch. Specifically, stereo full-range main speakers will always have second-level bass, because they are restrained by being only two sources and in the wrong locations, no matter how well they are executed or equalized. Multi-subs can solve this and bring top-level bass.

cheers

Oh, HELL no!!! What I said was that with small speakers that have poor bass capability it can be difficult to integrate a subwoofer. Then Bear123 said that modern A/V receivers make it easy to integrate a subwoofer, which is sort of a red herring, only worse. In order for that comment to have been a logically sensible and appropriate reply to what I said, he would need to have been arguing that a modern A/V receiver can somehow compensate for the inadequate bass capability of small speakers. You now join and talk about "the purpose of this particular discussion", but it is obvious that you don't even have a clue how this utterly ridiculous discussion ended up in this ludicrous place, or how it began. You really, really, really do not. And for the purpose of no discussion would it make even a whit of sense to argue that "excellent integration" has meaning equivalent to "optimal". That is without question one of the most patently bogus, risible argumentative attempts I've ever observed.

I never, ever, ever, ever said that stereo speakers with built-in subwoofers are superior to separate subs. I said no such thing.

I am intimately familiar with the concept that you and the two others are saying. What I actually did do, as a sort of aside that to my way of thinking wasn't the least bit important and certainly had no relevance to the matter of the difficulty in integrating subwoofers with tiny speakers, was to point out that there are in fact some advantages of stereo speakers with built-in subwoofers. I made this comment only because richard12511 joined the discussion and made a big deal about this, which was rather bizarre from my perspective, because what did this have to do with the question of whether it can be difficult to integrate a subwoofer with small speakers that have inadequate bass? So how did this all come about? It all came about because (a) of the comment that Bear123 made, which was a bit bizarre for the reason that I explained above, i.e., it would only have been logically sensible if his intent were to say that A/V receivers overcome the bass limitation of small speakers, and because (b) I responded to his peculiar comment in a way that I now regret, by pointing out that his lack of difficulty in integrating his subwoofer was not a lesser difficulty than what is encountered by people who have bought stereo speakers with subwoofers built in. It would never have occurred to me that someone else would then join in and throw another kink into the mix by strongly asserting that subwoofers that are built in to stereo speakers are entirely worthless. That never occurred to me because it isn't the sort of thing that I myself would do. I did not care one rat's ass about that question, and had not said anything that in any way implied that stereo speakers with subwoofers built in are better than a pair of separate subs. Not in any way, shape or form did I ever say anything of that sort, either before richard12511 joined and expressed his strong opinion on that question about which I couldn't have cared less, or afterward. What I did do, afterward, is point out, appropriately, that there are in fact some very real advantages of the kind of speaker that he characterized as being worthless. Those advantages that I pointed out really didn't need to be pointed out because they are entirely obvious. They are so obvious in fact that one of the things here that continues to expose disingenuousness is that no one has acknowledged that these advantages are genuine and meaningful. Anyone who was conducting themselves in a fully genuine manner and acting in good faith would surely have acknowledged this by this point. Yet, no one has, and this speaks volumes about the nature of what is going on here.

 

[KaiserSoze]

I concede. If someone held a gun to my head and told me I couldn't use subwoofers but had to make due with only tower speakers that play low, then yes, I would take all the extension I could get.

My room isn't huge, its about 2525 ft^3. I somehow managed to use about 15 of those for a pair of good subs.

That's nice, but for the record it's not something that I care much about or indicated that I did. As I have tried to explain, my having mentioned stereo speakers with built-in subwoofers was only for the purpose of saying that people who buy this kind of speaker have it just as easy as you, with respect to integration of the sub. That was all. In retrospect I have no idea why I thought that was something worth pointing out, but I never once said or implied that this kind of speaker is superior to having two subs that you can put wherever you like. I am sorry if you or richard12511 (or Newman) thought that I had said that, but I didn't. I did point out some of the patently obvious advantages of that type of speaker. I did that only after richard12511 put the second kink into the evolutionary path of this nowhere discussion by expressing a strong opinion on that other question about which I did not care and had said nothing beyond stating that which was obvious. I did not ever say or imply, not in any way whatsoever, that stereo speakers with subwoofers built in are superior to the setup that you and he prefer. To my way of thinking it would have been more genuine, rather than for you to have acted in way that insinuated that I had said something that I never said, for you or him to have acknowledged that there are in fact some advantages of stereo speakers with subwoofers built. I honestly do not understand why it was difficult to do that. I certainly did not have any difficulty acknowledging the advantages of separate subwoofers that you can place wherever you like. In fact I did acknowledge that plainly, at least once in a plain way, maybe twice in a plain way, but neither you nor he seemed to have noticed.

 

[Bear123]

If people have the space for them(I think they often do, given the prevalence of using bookshelf speakers on stands), I agree that tower speakers with lower extension and greater capability have advantages over small, single woofer speakers. As shown by most of the speakers tested here, distortion below 300 Hz creeps in rather early and at lower volumes than most realize imo, which is only exacerbated by room eq in this most demanding region.

It *seemed* as though you were trying very hard to argue for the merits of speakers with built in subs. Perhaps I took you the wrong way. No worries.

 

[aac]

You can wall mount bookshelves which has a great space-saving effect and is really convenient for small spaces.
For some reason manufacturers like to ignore this fact and there are no mounting points on the most of bookshelf "domestic" speakers.

 

[tuga]

At my seat in front of the screen I just measured 36dBA

How is the spectrum of that noise distributed, it's surely not even level at all frequencies?

 

[ctrl]

How is the spectrum of that noise distributed, it's surely not even level at all frequencies?

Certainly not, I think I would notice if white noise appeared as background noise in my listening room.

As already mentioned, the 36dBA were measured with an A-weighted sound level meter.

 

[Absolute]

I agree with that except not entirely with the last sentence. My reason, as I have previously discussed, is that there are lots of speakers being sold nowadays, for considerably more than mere pocket change, that do not have the bass capability needed for proper integratiion with a subwoofer at some frequency below 100 Hz, unless they are played at volume that is probably lower than the typical volume at which most people probably play their systems.

Agree. Most speakers have far too little capacity in the critical area between 100-400 hz. Here is from my experiments with Kii Three with low and high crossover to the subs;

A look at Kii Three Three anechoic measurements to confirm distortion around 200 hz;

Sorry for differences in the graphs, I can't find the mdat files and fix it. The first graph show Kii Three + subs crossed at 80 hz and room-corrected with Audiolense to fix the around 10 dB dip around 150-250 hz. Which is why the SPL doesn't show the actual speaker output, but it clearly shows the distortion shooting through the roof due to high stress on the speakers.
The second graph shows the subs crossed over at 200 hz to see if the capacity increase helps distortion. Can't remember if I had activated Audiolense or just manually EQ'd it with minidsp.

Here's how it looked;

Not claiming scientifical evidence here, just showing the results during a tuning-process while experimenting.

There has been a lot of discussion on this, which discussion has mostly concerned itself with audibility of distortion, but it has also been pointed out that depending on the steepness of the filter slopes, a 100 Hz crossover point will still allow the sub, typically, to emit sound at an audible level in the upper bass and even lower midrange, again depending on the particulars, but generally this concern is valid and is easily evidenced in many setups that employ subwoofers. Which is to say, it is manifest that there is no bass coming from those small bookshelf speakers using drivers that are claimed to be 6.5" but that are actually less than 5", and it is further not difficult to identify the location of the subwoofer just by moving your head a little.

Agree, one sub placed away from the speakers will become audible when crossed over above 40-50 hz.
You need more subs and you always need the fronts to play at the same time so that the directional ques will come from the higher frequencies played by the fronts. Otherwise you will hear where the subs are because there's no brick-wall crossover filter.

And in the off-axis response you get destructive interference for the frequency range one or two octaves above the crossover point, which means that you hear a dip in that area of frequency. You may beg to differ based on your personal experiences, in which case you and I have had different experiences from which we obtain our individual perspectives on this question. From my experience, and to sum it up, the only stereo speakers that easily integrate properly with a subwoofer at frequency as low as it needs to be are speakers that have sufficient bass capability that many people wouldn't bother with the subwoofer.

One subwoofer = difficult to integrate if it isn't placed near the fronts.
In my experience there's almost no speaker on the market with sufficiently high bass capability to rid itself of the need for a subwoofer. Thumb-rule is that any and every speaker without dedicated sub-drivers can and will benefit from avoiding the taxing load of sub-duty. Lower IMD, better capacity and the benefit of avoiding a great deal of thermal heating in the voice coils due to massive power needed for low frequencies at higher spl will always be good stuffs. But subs are not for entry-level audiophiles without microphones and know-how or patience.

 

[KaiserSoze]

Agree. Most speakers have far too little capacity in the critical area between 100-400 hz. ...
Agree, one sub placed away from the speakers will become audible when crossed over above 40-50 hz.
You need more subs and you always need the fronts to play at the same time so that the directional ques will come from the higher frequencies played by the fronts. Otherwise you will hear where the subs are because there's no brick-wall crossover filter.

One subwoofer = difficult to integrate if it isn't placed near the fronts.
In my experience there's almost no speaker on the market with sufficiently high bass capability to rid itself of the need for a subwoofer. Thumb-rule is that any and every speaker without dedicated sub-drivers can and will benefit from avoiding the taxing load of sub-duty. Lower IMD, better capacity and the benefit of avoiding a great deal of thermal heating in the voice coils due to massive power needed for low frequencies at higher spl will always be good stuffs. But subs are not for entry-level audiophiles without microphones and know-how or patience.

Of course the reasons for augmenting stereo speakers with a subwoofer (or two) are very strong. And as you indicate, the only sort of stereo speakers that are an exception to this are the kind with high-quality subwoofers built in. But I don't dare suggest that this type of speaker is desirable, because it is blasphemy to speak favorably of this type of speaker.

Using more than one sub (the kind not attached to the stereo speakers) can certainly help to mitigate the room modes, however it is not altogether apparent to me that using two subs (placed far from the main stereo speakers) will make proper integration of the subwoofers with the main speakers less difficult.

Hypothetically, what "proper integration" means is that for all frequency range where the subwoofers' contribution to the acoustic output is significant, the individual wavefronts from the main stereo speakers and from all of the subwoofers is reasonably coherent, spread out in phase by no more than 90 degrees. In order to achieve this modest degree of coherence, allowing that the crossover restricts the subwoofers from contributing significantly to the output above 100 Hz (a very generous allowance given that with common practice it is probably more like 300 Hz), it would be necessary to keep the subwoofers very close to the main stereo speakers, such that for any point in the room, the distance to any of the subwoofers is within +/- 3 feet of the distance to either of the main stereo speakers. Since it isn't easy for this to be satisfied even when using a single subwoofer located between the two main speakers, the implication is that either (a.) the crossover point should be low enough such that the subwoofers do not contribute significant output above about 25 Hz for the case where the subwoofers are scattered about a typical home listening room, or else (b) the two subwoofers should be positioned right up next to the main stereo speakers and should operate in stereo, i.e., each of them fully integrated with one of the two stereo speakers.

Perhaps this view is not realistic or reasonable. If it isn't, then the question becomes that of what "proper integration" means. Evidently all this means is that the owner isn't dissatisfied with the setup. Or maybe what it means is that somewhere in the room there is a special location where the response heard by the listener is the same within the overlap region as below or above the overlap region.

 

[JustIntonation]

Didn't follow the whole conversation on subs, but I can add my 2 cents.

Subs placed away from speakers can fix some things but also gives other problems. Even when crossed at 80Hz.
Subs should ideally not be further away than quarter wavelength of the crossover freq. Otherwise you will get off-axis dips (and cancellation at half wavelength distance of the crossover freq along the line of the sub<->speaker).
Subs do not cross entirely well with ported speakers because the sub will have different phase behavior than the speaker around port area.
Subs should ideally also be placed at the same distance from the listening position as the speakers.
And lastly, if it's for music then you usually don't need a lot of SPL capability at 20-30Hz. (for movies you do want that) You can still make it flat to 20Hz but music won't ususually actually contain such low frequencies at high levels so you won't need SPL capability down that low.
Best way to have great lows is by first of all having a large room and secondly having good deep low AFr bass traps, and then by proper placement of your speakers in the room, not too far away from the front wall.

 

[KaiserSoze]

Didn't follow the whole conversation on subs, but I can add my 2 cents.

Subs placed away from speakers can fix some things but also gives other problems. Even when crossed at 80Hz.
Subs should ideally not be further away than quarter wavelength of the crossover freq. Otherwise you will get off-axis dips (and cancellation at half wavelength distance of the crossover freq along the line of the sub<->speaker).
Subs do not cross entirely well with ported speakers because the sub will have different phase behavior than the speaker around port area.
Subs should ideally also be placed at the same distance from the listening position as the speakers.
And lastly, if it's for music then you usually don't need a lot of SPL capability at 20-30Hz. (for movies you do want that) You can still make it flat to 20Hz but music won't ususually actually contain such low frequencies at high levels so you won't need SPL capability down that low.
Best way to have great lows is by first of all having a large room and secondly having good deep low AFr bass traps, and then by proper placement of your speakers in the room, not too far away from the front wall.

Those are all very good points, some of which I hadn't thought about.

The lament that I had expressed was with little bookshelf speakers that lack adequate bass capability to properly cross over to a subwoofer. From there a quantum leap of sorts took place, such that there was a discussion, very one-sided and with tenacity on that one side, concerned with the question of whether stereo speakers with built-in subs are worthless junk. I thought it appropriate to mention that there are some advantages to having subwoofers incorporated into the main stereo speakers. It didn't know that it would be blasphemy to talk about those advantages.

But now that we have been brought here, there are some questions that deserve to be explored, concerning proper integration of subwoofers with the main speakers. Unfortunately there is no generally accepted agreement for what constitutes "proper integration".

One of the things you mentioned is the difficulty crossing a subwoofer with ported speakers owing to the phase behavior of ported speakers. With ported speakers there is an abrupt rotation in phase at the Helmholtz frequency, i.e., the peak in the port output. Below this frequency, phase changes rapidly with decreasing frequency, such that the lack of phase coherency between the port and the woofer is one way to explain the sharper rolloff of a ported speaker vs. a sealed enclosure. Given this rapid rotation in phase, the only way that a subwoofer could be coherent with the main stereo speaker in the overlapping frequency range would be for the subwoofer to exhibit the same rapid rotation in phase. In general when a subwoofer is crossed to ported speakers, the sub and the ported speakers can be coherent for a small frequency range but will necessarily be phase-incoherent at frequencies not very distant from the frequency where they are phase-coherent. This is a pretty strong argument to the effect that when a subwoofer is used, it is best for the main stereo speakers to be sealed.

Buy why does phase coherency even matter? It matters for the same reason that it matters with the other crossover points, i.e., the same reason that Linkwitz-Riley crossover slopes are widely preferred. It matters in order that the amount of destructive interference and phase cancellation between the two drivers will be constant throughout the crossover region, so that the response will be flat through the crossover region. Should the same expectation apply to the interface between a subwoofer (or a pair of them) and the main stereo speakers? Why should this crossover be an exception?

You mentioned the quarter-wavelength rule. If there are two or more sources of acoustic output overlapping in frequency and they are at different distances from the listener, the different distances should not differ from one another by an amount greater than 1/4 of the wavelength, where the wavelength is the wavelength for the highest frequency at which the sources are contributing significantly to the output. It becomes somewhat fuzzy, but it is probably appropriate to identify the frequency two octaves above the crossover point, as the important frequency. If we suppose that the crossover point is 100 Hz, then two octaves above this frequency is 400 Hz, where the corresponding wavelength is 2.8', and according to the quarter-wavelength rule the distances (from the listener to the main speakers, and from the listener to the subwoofers) should not differ by more than nine inches. If are less of a stickler for rules and apply the rule to frequency just one octave above the crossover point we get 17", and if we apply it to the 100 Hz crossover point we still get 2.8' for the quarter-wavelength. Clearly the crossover point will need to be a good deal lower if phase coherency is expected to be achieved with two subwoofers at locations far removed from the locations of the main stereo speakers. A choice has to be made. You can position the dual subwoofers so as to mitigate the standing waves and nulls for specific wavelengths at specific locations, or you position them so that phase coherency between the subs and the main speakers will be achieved, to a strong extent that still will depend on the phase behavior of the main stereo speakers. The only way to have it both ways (other than extensive application of room treatment) is for the crossover point to be down close to 20 Hz, in which case it becomes a true subwoofer in the sense of infrasonic output augmenting a pair of stereo speakers that each incorporate a conventional subwoofer.

I don't know what the answer is. I suppose that if my listening room did not have irregular dimensions, i.e., if it were a cube, I would be more concerned about the room modes, because in this case there would be one particular frequency that would be conspicuously too loud at specific locations and practically inaudible at other locations. A room of this sort would demand extensive room treatment. But the very same thing happens with the harmonics of that particular frequency, right on up through the midrange and treble, and is accepted as a fact of life and regarded as something that you aren't likely to notice unless you go looking for it, using a microphone and a measuring system. There is evidently some reason why we do not take the same attitude of indifference with respect to the longest wavelengths where a quarter of a wavelength can be equal to the room dimension.

 

[JustIntonation]

Those are all very good points, some of which I hadn't thought about.

The lament that I had expressed was with little bookshelf speakers that lack adequate bass capability to properly cross over to a subwoofer. From there a quantum leap of sorts took place, such that there was a discussion, very one-sided and with tenacity on that one side, concerned with the question of whether stereo speakers with built-in subs are worthless junk. I thought it appropriate to mention that there are some advantages to having subwoofers incorporated into the main stereo speakers. It didn't know that it would be blasphemy to talk about those advantages.

But now that we have been brought here, there are some questions that deserve to be explored, concerning proper integration of subwoofers with the main speakers. Unfortunately there is no generally accepted agreement for what constitutes "proper integration".

One of the things you mentioned is the difficulty crossing a subwoofer with ported speakers owing to the phase behavior of ported speakers. With ported speakers there is an abrupt rotation in phase at the Helmholtz frequency, i.e., the peak in the port output. Below this frequency, phase changes rapidly with decreasing frequency, such that the lack of phase coherency between the port and the woofer is one way to explain the sharper rolloff of a ported speaker vs. a sealed enclosure. Given this rapid rotation in phase, the only way that a subwoofer could be coherent with the main stereo speaker in the overlapping frequency range would be for the subwoofer to exhibit the same rapid rotation in phase. In general when a subwoofer is crossed to ported speakers, the sub and the ported speakers can be coherent for a small frequency range but will necessarily be phase-incoherent at frequencies not very distant from the frequency where they are phase-coherent. This is a pretty strong argument to the effect that when a subwoofer is used, it is best for the main stereo speakers to be sealed.

Buy why does phase coherency even matter? It matters for the same reason that it matters with the other crossover points, i.e., the same reason that Linkwitz-Riley crossover slopes are widely preferred. It matters in order that the amount of destructive interference and phase cancellation between the two drivers will be constant throughout the crossover region, so that the response will be flat through the crossover region. Should the same expectation apply to the interface between a subwoofer (or a pair of them) and the main stereo speakers? Why should this crossover be an exception?

You mentioned the quarter-wavelength rule. If there are two or more sources of acoustic output overlapping in frequency and they are at different distances from the listener, the different distances should not differ from one another by an amount greater than 1/4 of the wavelength, where the wavelength is the wavelength for the highest frequency at which the sources are contributing significantly to the output. It becomes somewhat fuzzy, but it is probably appropriate to identify the frequency two octaves above the crossover point, as the important frequency. If we suppose that the crossover point is 100 Hz, then two octaves above this frequency is 400 Hz, where the corresponding wavelength is 2.8', and according to the quarter-wavelength rule the distances (from the listener to the main speakers, and from the listener to the subwoofers) should not differ by more than nine inches. If are less of a stickler for rules and apply the rule to frequency just one octave above the crossover point we get 17", and if we apply it to the 100 Hz crossover point we still get 2.8' for the quarter-wavelength. Clearly the crossover point will need to be a good deal lower if phase coherency is expected to be achieved with two subwoofers at locations far removed from the locations of the main stereo speakers. A choice has to be made. You can position the dual subwoofers so as to mitigate the standing waves and nulls for specific wavelengths at specific locations, or you position them so that phase coherency between the subs and the main speakers will be achieved, to a strong extent that still will depend on the phase behavior of the main stereo speakers. The only way to have it both ways (other than extensive application of room treatment) is for the crossover point to be down close to 20 Hz, in which case it becomes a true subwoofer in the sense of infrasonic output augmenting a pair of stereo speakers that each incorporate a conventional subwoofer.

I don't know what the answer is. I suppose that if my listening room did not have irregular dimensions, i.e., if it were a cube, I would be more concerned about the room modes, because in this case there would be one particular frequency that would be conspicuously too loud at specific locations and practically inaudible at other locations. A room of this sort would demand extensive room treatment. But the very same thing happens with the harmonics of that particular frequency, right on up through the midrange and treble, and is accepted as a fact of life and regarded as something that you aren't likely to notice unless you go looking for it, using a microphone and a measuring system. There is evidently some reason why we do not take the same attitude of indifference with respect to the longest wavelengths where a quarter of a wavelength can be equal to the room dimension.

Yes, and you can add to that the difficulty for many of getting a sub in phase even above the port freq in the first place.
As for the 4 times the crossover freq and then again taking 1/4 wavelength distance I'm not really following you.. We don't need 1/4 wavelength of 4 times the crossover freq as the signal will be way down already there (48dB for LR4 crossover) and in reality most subs will have problems in that region already anyhow (usually this would be 320Hz, 4 * 80Hz).
Ports will indeed mess up a perfect crossover, though the effect of this error will in many rooms be much smaller than room problems / modes. Same goes for 1/4 wavelength rule effect vs room modes. Hell many rooms are such an incredible mess in the bass many feel it's better to not excite those modes at all and simply not use a sub at all. Much given advice for small amateur studios with small rooms is to not get big speakers but small ones which cut off high to not give distracting bad bass. Good bass really starts with the room, no substitute for that.

Yes agreed on many small bookshelf speakers having problems reaching an 80Hz sub with quality output. Especially most 5" bookshelves, though some quality ones which have 6"or 7" (or better yet 8") midwoofers should be able to do it reasonably well (though the bigger the midwoofer the more often it'll have more problems with directivity and their crossover to the tweeter). All 2-way bookshelf designs will have their midwoofer have to deal with the baffle step, that means it has to put out an extra 6dB of low mids & bass. The smaller the speaker the higher the baffle step starts. Another good argument for 3-way speakers.

 

[KaiserSoze]

Yes, and you can add to that the difficulty for many of getting a sub in phase even above the port freq in the first place.
As for the 4 times the crossover freq and then again taking 1/4 wavelength distance I'm not really following you.. We don't need 1/4 wavelength of 4 times the crossover freq as the signal will be way down already there (48dB for LR4 crossover) and in reality most subs will have problems in that region already anyhow (usually this would be 320Hz, 4 * 80Hz). ....

The reason is that, presumptively, the output of the subwoofer will be significant two octaves above the crossover point. The 1/4 wavelength rule derives from the fundamental, non-fuzzy fact that when two waves are offset in phase by 1/4 wavelength the destructive interference begins to be important. I find no reason why this rule should be applied at the crossover point as opposed to frequency at least one octave higher, maybe two octaves higher, depending of course on the steepness of the filter slopes.

As you point out, the output of the subwoofer will be -48 dB for 4th-order filtering, and beyond this, a typical sub may roll off naturally before reaching this higher frequency. These reasons are partly why I then did the analysis by applying the quarter-wavelength rule at the crossover point, in which case the bottom line is still that coherency will be decidedly poor when the subs are distributed around the room, even with the crossover point located at 80 Hz. It isn't at all difficult to discover this, because if the difference in the distances is as small as 5' (which is less than what is likely encountered in a room where two or more subs are distributed around the room), then at 112 Hz (which is easily a frequency low enough such that the quarter-wavelength rule should apply even for an 80 Hz crossover point and even using 4th-order slopes, because it is only 1/2 octave above the crossover point), 5' is 1/2 of the wavelength.

It further occurs to me that typical crossover slopes for the subwoofer-main speaker interface are not 4th-order, not even acoustically. And even though most subwoofers use high Q values to improve efficiency, which results in a peaky response, the drivers themselves typically are crudely flat up to a much higher frequency, 1kHz or even higher, and as such the only appreciable attenuation in the subwoofer's output at 320 Hz (for example) is ordinarily the attenuation due to the low-pass filter.

The bottom line is just what I said, i.e., that you must choose between two incompatible strategies. To paraphrase Rush, even if you choose not to choose, you still have made a choice. You can choose to position the subwoofers to mitigate the room modes, or you can choose to position them for coherency in the interface between the subwoofers and the main speakers. Of course in theory these two strategies are not inherently incompatible. All that is required, in order for them to become best buddies, is for the crossover point to be adequately low, i.e., not much higher than 20 Hz. When the variation in the distances to the different acoustic sources is a half wavelength at frequency only a half an octave higher than the precise crossover point, it is patently silly for anyone to think that the subwoofers and the main speakers operate coherently in the overlap.

 

[Newman]

Didn't follow the whole conversation on subs, but I can add my 2 cents.

Subs placed away from speakers can fix some things but also gives other problems. Even when crossed at 80Hz.
Subs should ideally not be further away than quarter wavelength of the crossover freq. Otherwise you will get off-axis dips (and cancellation at half wavelength distance of the crossover freq along the line of the sub<->speaker).
....

Just add more subs.

Not to mention the fact that full-range speakers would also need to be spaced less than λ/4, for every frequency in the room-mode range (say below 200 Hz -- whoops, λ/4 is now only 0.4m), so it is not really a sub vs full-range argument. In fact, maybe it is actually nothing more than another point in favour of multiple bass sources, and the freedom to place them where needed for best overall compromise result. That means satellites and add more subs, oh no!

cheers