subwoofer discussion

[alex-z]

I have a Dayton RS 18" tuned to 18hz, and 9 cheap JBL 12s. All diy and EQ'ed flat. At reasonable to a little loud volumes it sounds great. If I try to 'show off', like make your eyes blurry, I haven't figured out how to tame the bass yet. I don't know if it's box resonance, room resonance or what. Since I rarely show off it hasn't been a big deal, but it does kind of suck when I'm like "check out what it can do!".. sound like butt, that's what. The clipping lights on the amp aren't going off and the subs aren't moving a ton.. anyways, those 5 minutes a year are just disappointing.

I bet your bass issue is easily fixable.

1. Flat bass is bad. Human hearing naturally prefers a downward trending slope, response at 25Hz should be at least 5dB louder than at 200Hz. I have an 8.5dB slope implemented.

2. Make sure your subs are properly located throughout the room. If you have 9 drivers located close together that defeats the purpose of multi-sub, which is balanced room interaction.

3. Check the distortion and decay times of your subs with a cheap measurement mic. Often you can find things like poor cabinet bracing, manufacturers lying about xmax, or just outright poor cone stiffness.

 

[Beershaun]

2. Make sure your subs are properly located throughout the room.

I want to see pictures of that!

 

[AudioSQ]

I bet your bass issue is easily fixable.

1. Flat bass is bad. Human hearing naturally prefers a downward trending slope, response at 25Hz should be at least 5dB louder than at 200Hz. I have an 8.5dB slope implemented.

2. Make sure your subs are properly located throughout the room. If you have 9 drivers located close together that defeats the purpose of multi-sub, which is balanced room interaction.

3. Check the distortion and decay times of your subs with a cheap measurement mic. Often you can find things like poor cabinet bracing, manufacturers lying about xmax, or just outright poor cone stiffness.

It's flat from 20-80, which is generally about 10db hotter than the rest of the curve. Although considerably hotter when showing off.

I'm pretty limited on location options, but they aren't all bunched together. The 18" is on the right side of the front wall, the 12s spread out over about 8' on the back wall starting from the left. They're hidden behind the couch.

I can measure, how do I interpret the results to know if it's the box resonating, poor cone stiffness or something else?

Thanks!

 

[alex-z]

It's flat from 20-80, which is generally about 10db hotter than the rest of the curve. Although considerably hotter when showing off.

I'm pretty limited on location options, but they aren't all bunched together. The 18" is on the right side of the front wall, the 12s spread out over about 8' on the back wall starting from the left. They're hidden behind the couch.

I can measure, how do I interpret the results to know if it's the box resonating, poor cone stiffness or something else?

Thanks!

Box resonances would be characterized by long decay times aka stored energy, particularly around areas corresponding to the internal length/width/height. My first ever subwoofer was 33" tall, and had a quarter wavelength peak at 110Hz. Adding a vertical brace noticeably cleaned up the first 50ms of impulse response.

Poor cone stiffness is harder to pinpoint, as it usually manifests as distortion across the whole spectrum. It is especially apparent in paper cones, where the lightweight = high efficiency approach is favoured over the stiffness provided by aluminium or polypropylene. Unfortunately the best way to determine a weak cone is comparing to other drivers in the same cabinet at the same SPL. Weak is relative though, cheap woofers can be forgiven.

Purely excursion related distortion is super easy if you have have measured the T/S parameters yourself and performed the cabinet design accordingly. Many manufacturers publish xmax as the distance before the voice coil leaves the magnet gap completely, however distortion will rise sharply as the flux density decreases. For the sake of comparing drivers fairly, I consider 10% distortion to be true xmax on woofers, and 25% on subwoofers. As you turn up SPL, you reach a point where distortion rises disproportionately, that is the voice coil entering non-linear behaviour.

If you put 2 of the 12" in each corner and used the 18" just to augment the bottom 15-30Hz region it would likely sound better. Fewer room mode issues to contend with.

 

[AudioSQ]

I'm limited on where the 9 12"s can go, they pretty much have to be behind the couch out of site. The 18" can go on either side of the TV, but that's about it.

I did a waterfall measurement, but I don't know if the setting of the graph are correct and I'm not really sure how to interpret this. I think I get the general idea, but need to educate myself some more. I did start reading up on it but didn't get very far before other obligations came up. I'll read more on it tonight. Graph below, appreciate any comments, and apologies if I just totally did it wrong.

 

[FrantzM]

Phase and crossover matter. Here is a good whitepaper on how you'd use them manually if you don't have an integrated amp or AVR that handles that upstream.

@carewser if you haven't tried the techniques in this whitepaper before try them out and see what you think and if any of your subs do better or worse than others. With 10 you are in a pretty interesting position to cross compare different features to see what the actual difference it.
https://www.soundoctor.com/whitepapers/subs.htm

Maybe pick up a umik-1 microphone and install REW on your laptop and start measuring the differences between them all in your particular room and share with the group. That would be a pretty cool set of findings.

Hi

I will stand corrected and will learn from this but it seems to me there are some flaws in Sound Doctors , explanations. Form the articles in the link he posit this:

The point is, the sound leaves both subs at exactly the same time. Notice in Fig 7 the R sub is closer to your face. Perhaps the L sub is 11 feet away and the R sub is 4 feet away. That's a 7msec time differential. So you hear the leading edge of the bass wave from the Right sub, then 7 msec later the leading edge of the L sub... then the note dies away from the R sub and then 7 msec later the note dies away from the L sub. What have you accomplished? Here comes the magic: YOU HAVE FATTENED UP THE LOUDNESS ENVELOPE IN TIME ! This is the magic that humans love. This is why someone says, "OMG, two subs are SO much better than one!" So you have a combination of the arrival time differential, and to a certain extent you have the separate room coupling issues such that each sub is its own entity coupling into the room with slightly differing standing waves.

Our hearing apparatus will not have recognized a bass signal in 6 or 7 msec. It takes much longer; from memory, according to Earl Geddes, it can take up to 50 msec for 50 Hz. That is the main reason why the room, in the low bass behaves as a minimum phase system. IOW the Frequency response becomes the determinant. Not the phase response.. I could dig some references, In the meantime, I would like to see studies that show the importance of phase in the bass when it seems to be inconsequential even in the midrange... One of the way to achieve a smooth FR in the bass is to , actually manipulate the time delay, thus phases between the different subwoofers... then you equalize to make it even smoother.

Also I don't get the notion of "fattening the bass enveloppe". To me it sounds nice until I try to make sense of it . What is the "bass enveloppe" and how do I "fatten" it? What does that actually mean in concrete, scientific terms?

Waiting for explanations and willing to learn more. For now Geddes and Welti multi-subs approach do not make of phase what I think I see, in the good doctor essay...

Peace

 

[Beershaun]

Hi

I will stand corrected and will learn from this but it seems to me there are some flaws in Sound Doctors , explanations. Form the articles in the link he posit this:



Our hearing apparatus will not have recognized a bass signal n 6 or 7 msec. It takes much longer according to those who know a bit. From memory according to Earl Geddes, it can take up to 50 msec. That is the main reason why the room in the low bass behaves as a minimum phase system. IOW the Frequency response become the determinant. Not the phase response.. I could dig some references and I would like to see studies that show the importance of phase in the bass when it seems to be inconsequential even in the midrange... One of the way to achieve a smooth FR in the bass is to , actually manipulate the time delay, thus phase between the different subwoofers... then you equalize to make it even smoother.
Also I don't get the notion of "fatttening the bass enveloppe". To me it sounds nice until I try to make sense of it . What is the "bass enveloppe" and how do I "fatten" it? What does that actually mean in concrete, even scientific terms?

Waiting for explanations and willing to learn more. For now Geddes and Welti multi-subs approach do not make of phase what I think I see, in the good doctor essay...

Peace

I think you are hitting on the right points. Phase gives you a knob to adjust the summed frequency response across multiple speakers operating in the same bandwidth (like crossover region) in a way that you can't with equalization. With equalization you can't do anything about wave cancellation or augmentation at the listening position for a given frequency (like nulls). Adding or taking away energy doesn't work because it's the phase of the two waves cancelling each other out. With phase adjustment you can. You only have one knob though so you have to determine the specific frequency response problem that is being caused by the final phase mis-alignment between your speakers and adjust the phase until you get the response level.

I only have one subwoofer so my experiment was at the 80hz crossover region between my subwoofer and main speakers. I set up a mic at the listening position, played an 80hz tone at ~75db spl. Then I twittled then phase knob while watching the volume level of the tone and set it where the volume was highest ( saw about 2-3db difference). What I should do next is (but haven't because effort), at the same volume setting, play a 70hz tone and 90hz tone and see what the spl is at the listening position and try to adjust the phase knob until I get the most consistent volume across each of the 3 tones. Now I know my phase alignment is in the best position to enable me to eq my speakers effectively and minimize cancellations between them.

 

[Jdunk54nl]

I think you are hitting on the right points. Phase gives you a knob to adjust the summed frequency response across multiple speakers operating in the same bandwidth (like crossover region) in a way that you can't with equalization. With equalization you can't do anything about wave cancellation or augmentation at the listening position for a given frequency (like nulls). Adding or taking away energy doesn't work because it's the phase of the two waves cancelling each other out. With phase adjustment you can. You only have one knob though so you have to determine the specific frequency response problem that is being caused by the final phase mis-alignment between your speakers and adjust the phase until you get the response level.

I only have one subwoofer so my experiment was at the 80hz crossover region between my subwoofer and main speakers. I set up a mic at the listening position, played an 80hz tone at ~75db spl. Then I twittled then phase knob while watching the volume level of the tone and set it where the volume was highest ( saw about 2-3db difference). What I should do next is (but haven't because effort), at the same volume setting, play a 70hz tone and 90hz tone and see what the spl is at the listening position and try to adjust the phase knob until I get the most consistent volume across each of the 3 tones. Now I know my phase alignment is in the best position to enable me to eq my speakers effectively and minimize cancellations between them.

Just use band limited pink periodic noise with a range through the crossover region. Much easier than tones. Set up rew’s RTA and set averages for like 1 sec worth of data.

 

[Beershaun]

Just use band limited pink periodic noise with a range through the crossover region. Much easier than tones. Set up rew’s RTA and set averages for like 1 sec worth of data.

That's a great idea!

 

[Duke]

Our hearing apparatus will not have recognized a bass signal n 6 or 7 msec. It takes much longer, from memory, according to Earl Geddes, it can take up to 50 msec. That is the main reason why the room in the low bass behaves as a minimum phase system. IOW the Frequency response become the determinant.

Yes.

The ear's time-domain resolution is too poor at low frequencies for a few milliseconds to matter. Below is Earl Geddes on the subject, taken from the previously-posted video. A key point is that the steady-state frequency response tells us everything we need to know in the modal region. (We cannot distinguish the arrivals of individual waves, and the decay behavior is already in the steady-state response, so when we fix the steady-state response we have fixed the decays).

The video should be cued up to start at 5:36; watch until about 8:20:

To the extent that adjusting phase or delay affects the steady-state bass response it does matter, but this is because the frequency response is what matters, not because waveform coherence and/or the arrival times themselves do, in the bass region.

 

[Jdunk54nl]

I did a quick little experiment last night. I changed (increased and decreased) the distance setting on my AVR for my subwoofer.

Here are the results that I heard using band limited pink noise and playing the sub (only 1) and mains (left and right) together. I encourage others to give this a go. This is also me sitting in a two seat area about 3 feet of total distance and not a whole lot of change with results from either seat (mains to each other there was but sub to mains there wasn't)

There was definitely a smaller range, about .5m worth, of settings that provided the best constructive interference and between those it wasn't noticeable. I choose the distance in the middle, which was also the distance I already had from previous tests and measurements (could be slight bias here due to knowing SMAART results already but I did this with my eyes closed for the most part).

This was tested two ways (I was too lazy to pull out a microphone and also didn't really want to):
First just listening to when it was loudest (this was harder then second way and had a bigger range of sweet spot).
Then flipping polarity on sub and listening for when it was quietest.
This was not 30ms of delay worth of change to notice a difference.
There was also obvious spots with sub and mains where they had pure cancellation from being 180 degrees out of phase (that was the whole second test objective).

Try it for yourself and see. There were obvious spots where the subs and mains blended best. I went from the minimum distance (0) to the max (I don't remember what that was). The distance on the sub ended up being set farther than physical distance. This agrees with the white-paper from sound doctor with the subs natural delay.

I will say, it is much easier to tell differences between mains, but I already knew that. Every distance change there I can hear the center image shift one way or another.

 

[abdo123]

I did a quick little experiment last night. I changed (increased and decreased) the distance setting on my AVR for my subwoofer.

Here are the results that I heard using band limited pink noise and playing the sub (only 1) and mains (left and right) together. I encourage others to give this a go. This is also me sitting in a two seat area about 3 feet of total distance and not a whole lot of change with results from either seat (mains to each other there was but sub to mains there wasn't)

There was definitely a smaller range, about .5m worth, of settings that provided the best constructive interference and between those it wasn't noticeable. I choose the distance in the middle, which was also the distance I already had from previous tests and measurements (could be slight bias here due to knowing SMAART results already but I did this with my eyes closed for the most part).

This was tested two ways (I was too lazy to pull out a microphone and also didn't really want to):
First just listening to when it was loudest (this was harder then second way and had a bigger range of sweet spot).
Then flipping polarity on sub and listening for when it was quietest.
This was not 30ms of delay worth of change to notice a difference.
There was also obvious spots with sub and mains where they had pure cancellation from being 180 degrees out of phase (that was the whole second test objective).

Try it for yourself and see. There were obvious spots where the subs and mains blended best. I went from the minimum distance (0) to the max (I don't remember what that was). The distance on the sub ended up being set farther than physical distance. This agrees with the white-paper from sound doctor with the subs natural delay.

I will say, it is much easier to tell differences between mains, but I already knew that. Every distance change there I can hear the center image shift one way or another.

I have had a totally different experience. For me delays don’t make that much of a difference.

But again my speakers and subs are sealed and are already almost phase coherent without doing anything.

 

[Jdunk54nl]

I have had a totally different experience. For me delays don’t make that much of a difference.

But again my speakers and subs are sealed and are already almost phase coherent without doing anything.

We also have an open concept floor plan and the width is 18’ 8” for a 6’ 10” length then opens up to 30’ to 39’ wide (depends on the exact spot) for a 12’ length. Before narrowing to 6’ in our kitchen for the remainder. Total Length is 31’ 5”. Ceilings are 8’ 11”.
I am sure room size will make a pretty significant difference on this and standing modes.
My speakers and subs are sealed too. I sealed my mains with port plugs and sub was always sealed

 

[King_Pin]

I've never bought subs always built them.
The first 3 pics are all 18" subs. I've always run duals.
I much preferred them in sealed boxes placed 1/3 the way up the wall between the speakers and the listening position.

Of course my dual 21's I now use which I've shown before.
They also started out ported but I had to move them out of my theater room to put my shop in there and they came upstairs in sealed boxes.

 

[Beershaun]

Wow!

 

[estuardo4]

I think you meant a 2.2 system. You want both subwoofers managed independently. Check how your ARC version handles bass. Since the Paradigm PW-AMP only has one sub output it can't manage your subwoofers independently. I mean you could plug in a Y-splitter and just "run what you brung" but your system isn't really able to tune it properly. So you'd get some combination of overly exaggerated frequencies where the two are augmenting each other and dropouts where the two are cancelling each other with no way for the system to understand that it's two different speakers.

I mean by all means plug it in and see what it sounds like. No one is going to get hurt.

Just my above and below neighbors if I don't know what I'm doing

And yeah, I meant 2.2, but using a Y connector and a lot of patience tuning both subs to my room.

 

[carewser]

I have 2 SVS-SB2000s. I love them. They are in 2 separate 2.1 systems but I would never want to go without a subwoofer in my system again. Even if I had Amir's setup.

I hope when you ordered them you insisted on the same deal you get with pizza-2 for the price of 1

 

[Spkrdctr]

All this and you still will not have enough bass. Your goal should be if an artillery piece goes off in a movie, you get slammed in the chest with the muzzle blast recreated from your sub. You all need chest thumping, bone vibrating OMG bass. Then you will have checked an item off your bucket list! But, I do want to warn you that when I had my system, it did cause light damage to the window seals, and light bulbs kept failing. Since mine was in the basement with a drop ceiling, it would lift the drop ceiling panels about an inch or so, they were like a giant pressure release valve that probably saved my eardrums. My wife had no appreciation of extreme bass at all. She threatened to have Goodwill come pick up the subs.

 

[Beershaun]

I hope when you ordered them you insisted on the same deal you get with pizza-2 for the price of 1

Yes! That's how I ended up with 2.
Buy one and get $100 off a second.