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Magnepan LRS Speaker Review

josh358

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I think people expect designs that just work out of the box, that behave nicely in the majority of rooms.

Also Amir has been quiet transparent with which part of the measurements are accurate.

So to say that the Klippel is 'wrong' is just garbage because it is measuring what's coming out of the speaker.

If the room will significantly alter the frequency response of the speaker to the point where anechoic measurments don't matter then that's not a great design either way.
I am not sure what people aren't getting about this.

Unless your definition of "room" doesn't require the presence of a floor, an open baffle speaker will work in any room, thank you.

If you measure a loudspeaker in a configuration in which it doesn't work right -- with a blanket thrown over the top, say, or at the bottom of a swimming pool -- your measurements will be meaningless, however accurate they are.

Unless, of course, you want to listen to your speaker at the bottom of a pool.
 

josh358

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Yes, and a monopole measured in free space will not correspond to the sound of a monopole sitting on the floor either. The point of measuring any speaker in free space is not to give you some kind of absolute ruling of what a speaker will sound like, but to tell you what the speaker's raw contribution is to the room/speaker sound field.
To be sure, but in a dipole the effects are so pronounced as to render such measurements useless.
What is it about a dipole that "doesn't work properly" in free space? Isn't the shortest panel dimension of more relevance than the longest?
Here's an illustration of the response of an open-baffle dipole:
1623430780909.png

Note that the response starts to fall off below a certain frequency, after which it declines at 6 dB/octave. That rolloff is called dipole cancellation. It has to be corrected either electronically or acoustically; most dipole speakers use tuned segments to do the latter. As you increase the size of the baffle, the point at which the rolloff begins slides down. If it slides down from 100 Hz to 50 Hz, say, you get 6 dB more output from the speaker.

Both the horizontal and vertical dimensions of a dipole baffle matter. The floor is particularly important because a) every speaker sits on one and b) in practice, the lowest frequency drivers or segments will be placed near the floor so that the vertical path length around the baffle is maximized.

This is a favorite illustration of mine:

1623431536631.png


This illustration is intended to demonstrate the effects of room reflections, but I'm using it to illustrate the effect of the floor on the acoustical size of a baffle. If you look at the real loudspeaker and its floor reflection, you can see that the effective size of the baffle is doubled.

You can talk about the raw contribution of the speaker to the room/sound field, but see my point about measuring a sealed woofer with the back of the cabinet removed. That's what you're doing when you measure a dipole in free space -- removing part of its baffle -- and the raw data in that case will be no more meaningful than the raw data from pulling the drivers out of a loudspeaker and measuring them without a cabinet at all.

Sure, given a knowledge of baffle shape and driver location you could mathematically transform the measurements to make them meaningful, but that hasn't been done, and I don't know of anyone who has done it. Even Siegfried Linkwitz, no slouch when it came to mathematical modeling, did a lot of baffle design by cut and paste.

So we're back to measurements that don't tell us as much as we would like to know about how the loudspeaker will measure or sound in a living room.
 
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Wes

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Magnepan can't build LRS fast enough to fulfill demand. I suspect that means that the used market will show elevated prices.

As you probably know, much of the sound quality from a Magneplanar design will depend on room placement and acoustic treatment (if any) Typically one also needs an amplifier capable of delivering faily high power into fairly low impedances.

Magnepan designs their speakers with the goal of providing an experience as close as possible to hearing an orchestra from a fairly close center seat at Minneapolis' Orchestra Hall. This design goal doesn't always result in a speaker that works well with- for example - heavy metal.

I have a pair of MG 3.6's that I have tri-amped using a DEQX, along with a pair of GR Research / Rhythmik open-baffle servo subs. The subs give more flexibility in the kind of music that "works" with the system, and the DSP allows for a more neutral overall "voice" as opposed to the Minneapolis orchestra hall type experience.

pics of your room and placement would be fun to see, too
 

No. 5

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So we're back to measurements that don't tell us as much as we would like to know about how the loudspeaker will measure or sound in a living room.
They may not tell us as much as we'd like, but do they tell us enough of the right information? Earlier you had said:
No, the 360 degree sound field of a dipole measured in free space will *not* correspond to the sound field of a dipole sitting on the floor.
and
Sure, but a dipole can't work properly in free space, so I'm not sure what the Klippel is measuring other than a dipole with most of its baffle removed.
I don't dispute that the floor reflection has an effect on the effective baffle size and therefore the low frequency roll-off, but it has to be said that changing the effective height of the baffle or placing a speaker in a room doesn't really change the horizontal dispersion or the listening axis response above mid and high frequency. Both of those attributes are unquestionable every bit as important to the sound field as the low frequency roll off and there's no reason they can not be measured in free field.
 

josh358

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They may not tell us as much as we'd like, but do they tell us enough of the right information? Earlier you had said:

and

I don't dispute that the floor reflection has an effect on the effective baffle size and therefore the low frequency roll-off, but it has to be said that changing the effective height of the baffle or placing a speaker in a room doesn't really change the horizontal dispersion or the listening axis response above mid and high frequency. Both of those attributes are unquestionable every bit as important to the sound field as the low frequency roll off and there's no reason they can not be measured in free field.

Agreed. It isn't that the raw measurements don't provide useful information, as that the bass and midbass measurements don't, and people are misled by that.
 

No. 5

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Agreed. It isn't that the raw measurements don't provide useful information, as that the bass and midbass measurements don't, and people are misled by that.
I can agree with that. After all, many people seem to just take a superficial look at available measurement data without digging into what the data is telling them.
 

richard12511

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Amir's method for measurements isn't really valid for dipole speakers. His method assumes a point source- a box speaker.

Actually, Amir's measurements are perfectly valid for dipole speakers. In fact, I'd say they're the best that exist for dipole speakers, as they fully capture the soundfield and show you how the speaker radiates into 3D space, forwards and backwards. From those measurements, you should be able to calculate the effect of the backwall at various differences.

What's not valid is the PIR estimate(I'm guessing it doesn't sum the back wave properly), and the interpretation of those measurements relative to the monopole standard. I'm not sure we know yet what SOTA dipole measurements should look like, which is why we need to measure many more dipoles on the NFS. The Olive score is also not valid at all for dipoles. Don't confuse that with the measurements themselves, though. The measurements are perfectly valid as long as the error is low enough.
 
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josh358

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Actually, Amir's measurements are perfectly valid for dipole speakers. In fact, I'd say they're the best that exist for dipole speakers, as they fully capture the soundfield and show you how the speaker radiates into 3D space, forwards and backwards. From those measurements, you should be able to calculate the effect of the backwall at various differences.

What's not valid is the PIR estimate(I'm guessing it doesn't sum the back wave properly), and the interpretation of those measurements relative to the monopole standard. I'm not sure we know yet what SOTA dipole measurements should look like, which is why we need to measure many more dipoles on the NFS. The Olive score is also not valid at all for dipoles. Don't confuse that with the measurements themselves, though. The measurements are perfectly valid as long as the error is low enough.
it isn't the front wall that's the concern -- boundary interaction works with dipoles just as it does with monopoles, except that the frequencies at which it occurs are different because the backwave is out of phase. Rather, it's the fact that the dipoles aren't on the ground plane that's the main (though not the only) problem. It seems to me that the best solution would be to write some code that calculates an adjusted response.

Another issue -- since dipoles don't excite the x and y axial room modes, the bass is smoother in an actual room than the bass of a monopole with identical response. And that of course is another effect that has to be superimposed on the measurements, although it can be mathematically inferred from them, as many other dipole traits can be.
 

richard12511

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it isn't the front wall that's the concern -- boundary interaction works with dipoles just as it does with monopoles, except that the frequencies at which it occurs are different because the backwave is out of phase. Rather, it's the fact that the dipoles aren't on the ground plane that's the main (though not the only) problem. It seems to me that the best solution would be to write some code that calculates an adjusted response.

I guess it depends on what you mean by "response". If you mean estimated in room response(ie PIR), I agree, as the currently generated PIR (I'm pretty sure) is incorrect for dipole speakers. If you mean the anechoic response, I disagree. You want to know how the speaker radiates in three dimensions free from all room interaction, which is what the NFS gives. From that, you can calculate room and boundary interactions at various distances with various wall/ceiling/floor reflectivity. If you measure in a non-anechoic environment, that measurement is only valid for that particular boundary distance, boundary reflectivity, and mlp distance combination.

If anything, anechoic measurements are even more important for speakers that interact with the room to a greater degree. They allow us to estimate the response in many different types of rooms.

The only exception to this is when the radiation pattern of the speaker itself is altered from its free form anechoic pattern(ie in wall/soffit mounted speakers). In that case, you want to measure it's "actual anechoic" configuration(ie on an IB). You wouldn't measure a normal monopole with the driver outside of the baffle.

You could argue that this is partly true with panel speakers(due to the floor interaction), and I think you'd be right, but luckily this speaker was measured on a solid platform(ie not suspended in air) and the error is in the vertical plane. The NFS measurements are still the gold standard for speakers like the LRS or any other panel speakers.

Where the error comes in, is in the interpretation. This is an area where my mind has changed. When first viewing these measurements, I judged them as horrible, but that's because I was judging them by what good(highly preferable) monopole measurements are supposed to look like. I was judging them by how close they came to that flat on axis, smoothing increasing directivity standard. This was (imo) wrong on my part. I don't think we really know what measurements of speakers like this are supposed to look like, so we really have no conclusive way to say whether or not these measurements are good or bad. Unfortunately, this means that measurements for speakers like this really aren't all that useful. Not useful doesn't mean wrong, though.

What we need is many more Klippel NFS measurements of speakers like this. Then we need many blind listening tests that we can use to start to understand what a SOTA panel speaker measurement should look like. This will also start to make these speakers even better, as designers will have a much clearer target to aim for. Until we have these measurements and listening tests though, these measurements don't have much value.

Another issue -- since dipoles don't excite the x and y axial room modes, the bass is smoother in an actual room than the bass of a monopole with identical response. And that of course is another effect that has to be superimposed on the measurements, although it can be mathematically inferred from them, as many other dipole traits can be.

This is not an issue with the anechoic measurements, though. This is an issue with trying to use those measurements to predict performance.
 

josh358

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I guess it depends on what you mean by "response". If you mean estimated in room response(ie PIR), I agree, as the currently generated PIR (I'm pretty sure) is incorrect for dipole speakers. If you mean the anechoic response, I disagree. You want to know how the speaker radiates in three dimensions free from all room interaction, which is what the NFS gives. From that, you can calculate room and boundary interactions at various distances with various wall/ceiling/floor reflectivity. If you measure in a non-anechoic environment, that measurement is only valid for that particular boundary distance, boundary reflectivity, and mlp distance combination.

If anything, anechoic measurements are even more important for speakers that interact with the room to a greater degree. They allow us to estimate the response in many different types of rooms.

The only exception to this is when the radiation pattern of the speaker itself is altered from its free form anechoic pattern(ie in wall/soffit mounted speakers). In that case, you want to measure it's "actual anechoic" configuration(ie on an IB). You wouldn't measure a normal monopole with the driver outside of the baffle.

You could argue that this is partly true with panel speakers(due to the floor interaction), and I think you'd be right, but luckily this speaker was measured on a solid platform(ie not suspended in air) and the error is in the vertical plane. The NFS measurements are still the gold standard for speakers like the LRS or any other panel speakers.

Where the error comes in, is in the interpretation. This is an area where my mind has changed. When first viewing these measurements, I judged them as horrible, but that's because I was judging them by what good(highly preferable) monopole measurements are supposed to look like. I was judging them by how close they came to that flat on axis, smoothing increasing directivity standard. This was (imo) wrong on my part. I don't think we really know what measurements of speakers like this are supposed to look like, so we really have no conclusive way to say whether or not these measurements are good or bad. Unfortunately, this means that measurements for speakers like this really aren't all that useful. Not useful doesn't mean wrong, though.

What we need is many more Klippel NFS measurements of speakers like this. Then we need many blind listening tests that we can use to start to understand what a SOTA panel speaker measurement should look like. This will also start to make these speakers even better, as designers will have a much clearer target to aim for. Until we have these measurements and listening tests though, these measurements don't have much value.



This is not an issue with the anechoic measurements, though. This is an issue with trying to use those measurements to predict performance.
I agree -- the anechoic measurements themselves, as opposed to some of the inferences made from them, are valid and potentially very useful. In fact, when Amir was first asked to measure the LRS, I said that I hoped the measurements would shed some light on the fact that planar dipoles typically sound a good deal better than the conventional measurements would suggest, which accords with your goal of finding better criterion by which to assess them.

There sure are some significant challenges here. How does one interpret the measurements of a speaker that (in the shorter models, anyway) is listened to partly in the near and partly in the far field, with the transition depending on listening distance?

How do you develop a quality metric for something like interaction with room modes, or the effect of polar pattern on the reverberant field and the fact that it shifts optimal RT60 to something closer to that of the typical living room?

How does the elimination of the baffle step and uniformity of the polar pattern (in the higher end models, anyway) affect subjective impressions? (Linkwitz felt that uniform dispersion was crucial to the sense of space.)

There are so many variables, as there wouldn't be if we were comparing loudspeakers within the same family, that I can often tell more about the sound of a loudspeaker from knowing whether it's a dynamic or planar magnetic or ESL or horn than I can by looking at the measurements. That I think makes it more challenging to develop metrics that apply across families, e.g., the tendency to excite room modes -- all monopoles are similar in that respect, and so are all dipoles, but they aren't similar to one another. (A related example -- both monopoles and dipoles suffer from boundary effects, but a monopole can be positioned with respect to the front and side wall to minimize the effect, while a dipole can't, but doesn't suffer from floor and ceiling bounce the way a monopole does -- in fact, a line source requires it.)

I've become close to the guys at Magnepan in recent years, to the point at which I've been collaborating on the design of their forthcoming speaker. In the course of that I've learned a lot about the measurement and listening methodologies that they use, which are the product of 50 years of experimentation and refinement, backed by a robust commitment to blind testing. There is so much lore there that I wouldn't know where to begin even if I were privy to it all.

Response measurements are an example of the issues that they've learned to overcome. It's difficult to make a gated quasi-anechoic measurement of a tall line source, and in any case, measuring in the near field would lead to an inaccurate measurement of bass response. So in practice, multiple measurements are made -- gated measurements to tune on-axis response, in-room measurements at the listening position to tune bass response, polar measurements to measure power response, etc. And then the known modal behavior of the room and the boundary reflection from the front wall has to be taken into account as well to yield a response that is less dependent on the specific room (and since it still remains somewhat dependent owing to acoustical baffle extension, measurements and listening have to be conducted in rooms of varying size as well). Needless to say, it would be a boon to be able to do that from anechoic measurements of the sound field!

So it's worthwhile but hard to bottle this, in part because they're beginning with empirical results (listening backed by blind A/B testing with non expert and expert listening panels) and working backwards to find the salient measurements and design techniques." But I think it would be wonderful if objective criteria could be established, as they have been for monopoles -- something that would probably require modifying the criteria for the assessment of monopoles as well, to account for factors such as their differing interactions with the room.
 

Wes

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anything we can hear about their forthcoming speaker?
 

josh358

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anything we can hear about their forthcoming speaker?
There isn't terribly much that isn't already known, since the lab prototype went on a brief road show so that they could get feedback on it. But for anyone who missed that, it's a "wife friendly" Maggie with panels that are only 12" wide and a couple of concealable dipole woofers that use multiple dynamic drivers to make the system full range without compromising quality or creating that old bugaboo, audible discontinuity between the dynamic woofers and planar panels. The woofers themselves are self powered and use DSP for dipole equalization and room tuning.

Otherwise, it's been christened the 30.7 C (that's what we're calling it, anyway), the cosmetic renders look amazing, and it involves a lot of innovations for Magnepan beyond the use of dynamic drivers and DSP. Many of these will make their way down market as newer models are released, including a new aluminum frame design. Right now, they're tuning that up so that the extrusion die can be made, and as always, that's an iterative process -- for example, yesterday we were trying to figure out how to position the ribbon tweeter on the beveled extrusion without causing diffraction issues or bringing it out of time with the midrange, or having to make two extrusion dies. And the day before that, it was a question of how to align the T-nuts in the channel of the extrusion for assembly, and in that case, it was an engineer at the extrusion company who came up with a simple and elegant solution.

Big on the list of things to do, and the most fun -- continue developing new configuration options for the concealable woofers. Since we haven't been able to get the laws of physics repealed, we've been kicking around a lot of innovative approaches, and I mean a lot.

Assuming this all goes without a hitch and the first DSP unit is delivered as expected, Wendell Diller will take the first pair on a tour so that everyone has a chance to hear it.
 

richard12511

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There isn't terribly much that isn't already known, since the lab prototype went on a brief road show so that they could get feedback on it. But for anyone who missed that, it's a "wife friendly" Maggie with panels that are only 12" wide and a couple of concealable dipole woofers that use multiple dynamic drivers to make the system full range without compromising quality or creating that old bugaboo, audible discontinuity between the dynamic woofers and planar panels. The woofers themselves are self powered and use DSP for dipole equalization and room tuning.

Otherwise, it's been christened the 30.7 C (that's what we're calling it, anyway), the cosmetic renders look amazing, and it involves a lot of innovations for Magnepan beyond the use of dynamic drivers and DSP. Many of these will make their way down market as newer models are released, including a new aluminum frame design. Right now, they're tuning that up so that the extrusion die can be made, and as always, that's an iterative process -- for example, yesterday we were trying to figure out how to position the ribbon tweeter on the beveled extrusion without causing diffraction issues or bringing it out of time with the midrange, or having to make two extrusion dies. And the day before that, it was a question of how to align the T-nuts in the channel of the extrusion for assembly, and in that case, it was an engineer at the extrusion company who came up with a simple and elegant solution.

Big on the list of things to do, and the most fun -- continue developing new configuration options for the concealable woofers. Since we haven't been able to get the laws of physics repealed, we've been kicking around a lot of innovative approaches, and I mean a lot.

Assuming this all goes without a hitch and the first DSP unit is delivered as expected, Wendell Diller will take the first pair on a tour so that everyone has a chance to hear it.

Really awesome that they are going active and with DSP. One of the common "complaints" I see with Magnepans is that they're difficult to drive(though I think that's overblown). Active takes that out of the picture :), and DSP to boot :D.
 

DonH56

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Really awesome that they are going active and with DSP. One of the common "complaints" I see with Magnepans is that they're difficult to drive(though I think that's overblown). Active takes that out of the picture :), and DSP to boot :D.

I don't know the impedance profile of the woofer array. The panels themselves are insensitive and low in impedance, but almost purely resistive, so are actually not a bad load. They do not have the wide swings in impedance (magnitude and phase) that many conventional speakers exhibit.

As for radiation and interaction with the room, at low frequencies they trend toward omnidirectional point sources like any speaker, and toward line arrays at high frequencies, so direct sound forward and back with less to the sides and top/bottom. Thus they are less sensitive to the room except for the wall behind over much of their range. I do not like comb filter effects so have always damped the back wave unless I was in a very large room and could get them far from the back wall. Damping gives a much more precise image and avoids all the frequency response ripples from the back wave but you do lose some "space" from the room. I prefer a dead room with space provided by the recording instead of my room layering on top of that, but I am in the minority. Damping the back wave also lets me place them closer to the rear wall.

Anechoic measurements are the standard so I have no quibbles with that. Trying to include a room would be folly since rooms differ widely and they are so sensitive to placement within the room. The room will provide a bit of bass boost, depending upon where they are placed and where you sit, but panels do not have great excursion and I have always rolled off the bass and sent it to a good sub anyway. Maggies distort heavily driven with large bass signals. It will be interesting to hear (I hope, I missed the tour) how the new dynamic woofer panels change that dynamic and how they integrate the system. DSP should make that fairly trivial; when I first integrated a sub with my MG-I's ca. 1979~1980 the resources and (analog) circuits I used were far less than what is available today.

FWIWFM - Don
 

josh358

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Really awesome that they are going active and with DSP. One of the common "complaints" I see with Magnepans is that they're difficult to drive(though I think that's overblown). Active takes that out of the picture :), and DSP to boot :D.
Unfortunately, active is only for the woofer. That isn't because it shouldn't be entirely active, but audiophiles want to buy their own fancy amp. It should be possible to use the DSP for the panel as well, though.

Yeah, I agree that the business about Maggies being difficult to drive has been overblown. They're a very easy resistive load. They are somewhat insensitive, but that just means you can't use your 60 watt amplifier on them (well, you can, but . . . ). They need maybe 200 watts to strut their stuff, more if you want to use them to the max (very few do, you'd go deaf listening at 110 or 115 dB, not to mention having some very pissed neighbors). Neodynium magnets would make them more efficient, but the added cost of the magnets would be significantly higher than the added cost of a bigger amp.
 

josh358

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I don't know the impedance profile of the woofer array. The panels themselves are insensitive and low in impedance, but almost purely resistive, so are actually not a bad load. They do not have the wide swings in impedance (magnitude and phase) that many conventional speakers exhibit.

As for radiation and interaction with the room, at low frequencies they trend toward omnidirectional point sources like any speaker, and toward line arrays at high frequencies, so direct sound forward and back with less to the sides and top/bottom. Thus they are less sensitive to the room except for the wall behind over much of their range. I do not like comb filter effects so have always damped the back wave unless I was in a very large room and could get them far from the back wall. Damping gives a much more precise image and avoids all the frequency response ripples from the back wave but you do lose some "space" from the room. I prefer a dead room with space provided by the recording instead of my room layering on top of that, but I am in the minority. Damping the back wave also lets me place them closer to the rear wall.

Anechoic measurements are the standard so I have no quibbles with that. Trying to include a room would be folly since rooms differ widely and they are so sensitive to placement within the room. The room will provide a bit of bass boost, depending upon where they are placed and where you sit, but panels do not have great excursion and I have always rolled off the bass and sent it to a good sub anyway. Maggies distort heavily driven with large bass signals. It will be interesting to hear (I hope, I missed the tour) how the new dynamic woofer panels change that dynamic and how they integrate the system. DSP should make that fairly trivial; when I first integrated a sub with my MG-I's ca. 1979~1980 the resources and (analog) circuits I used were far less than what is available today.

FWIWFM - Don
I think the compromise that most people settle on is to use diffusion in back. That way, you get the sense of space without the comb filtering and can as well use them closer to the wall with good results. I've also tried absorption, and found it did what you said, but personally preferred the space, in fact I haven't yet found a treatment that doesn't do more harm than good. But I'm probably in the minority on that one, too.

I disagree about the room, because we aren't talking about modal behavior that's specific to the room, just about sitting the speaker on the floor so that the effective baffle size is doubled. All dipoles are designed to work that way and all will lose a tremendous amount of bass if the baffle is more than about a foot above the floor. In the case of a full height line source, the ceiling is crucial as well, and again, most rooms have standard ceilings at about 8' (they don't work as well in rooms with an unusually high ceiling). A line source uses the floor and ceiling reflections to emulate an infinite line. (In practice, the effect is limited to about 2.5 times baffle height.) In the absence of a floor and ceiling, there will be a transition between near and far field as you say, but *with* the floor and ceiling you will always be within the far field. The only reason large Maggies stop short of the ceiling is that it would be unacceptable cosmetically -- they'd do it if they could.
 

DonH56

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I think the compromise that most people settle on is to use diffusion in back. That way, you get the sense of space without the comb filtering and can as well use them closer to the wall with good results. I've also tried absorption, and found it did what you said, but personally preferred the space, in fact I haven't yet found a treatment that doesn't do more harm than good. But I'm probably in the minority on that one, too.

I disagree about the room, because we aren't talking about modal behavior that's specific to the room, just about sitting the speaker on the floor so that the effective baffle size is doubled. All dipoles are designed to work that way and all will lose a tremendous amount of bass if the baffle is more than about a foot above the floor. In the case of a full height line source, the ceiling is crucial as well, and again, most rooms have standard ceilings at about 8' (they don't work as well in rooms with an unusually high ceiling). A line source uses the floor and ceiling reflections to emulate an infinite line. (In practice, the effect is limited to about 2.5 times baffle height.) In the absence of a floor and ceiling, there will be a transition between near and far field as you say, but *with* the floor and ceiling you will always be within the far field. The only reason large Maggies stop short of the ceiling is that it would be unacceptable cosmetically -- they'd do it if they could.

I would actually prefer diffusion but have rarely had it. Diffusors are more complex to make and/or more expensive to purchase, though there are reasonably priced options these days. I also like the idea of combination panels that diffuse the higher frequency and absorb some of the bass. Conventional stepped diffusors need to be really deep to do anything in the bass region, and problems can occur starting in the lower midrange or mid-bass.

I often wondered why they don't make a series of models with different heights. When I asked many, many years ago the answer (from Jim, I believe) was they had models to fit most people and did not have the resources to create such a broad line. I was thinking a series of frames would work to make it easier to assemble, but he or one of the others on the team also noted controlling a long panel presented some technical difficulties as well. I suggested something like Jansen with maybe a 18"~24" standard panel in a frame that they could stack to whatever height but it never went anywhere AFAIK. Impedance and crossover would be another challenge with a variety of sizes, of course.
 

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I would prefer rarely had it. Diffusors are more complex to make and/or more expensive to purchase, though there are reasonably priced options these days. I also like the idea of combination panels that diffuse the higher frequency and absorb some of the bass. Conventional stepped diffusors need to be really deep to do anything in the bass region, and problems can occur starting in the lower midrange or mid-bass.

I often wondered why they don't make a series of models with different heights. When I asked many, many years ago the answer (from Jim, I believe) was they had models to fit most people and did not have the resources to create such a broad line. I was thinking a series of frames would work to make it easier to assemble, but he or one of the others on the team also noted controlling a long panel presented some technical difficulties as well. I suggested something like Jansen with maybe a 18"~24" standard panel in a frame that they could stack to whatever height but it never went anywhere AFAIK. Impedance and crossover would be another challenge with a variety of sizes, of course.
You could always do a series/parallel arrangement with the tall ones -- impedance would oscillate from 4 to 6 to 8, but I think that's OK. A lot of guys have said they'd like a short version with a true ribbon, but now they'll be coming out with narrow ones instead, and that will likely include shorter narrow ones down market. I've lobbied them personally to make a Maggie mini monitor, a small point source dipole, but without success. (The Mini Maggies only work well in the near field because of power response issues.) I've though of throwing a couple together with a Neo 10 clone and a small true ribbon or a Neo 3 -- if it sounded good, I'd send it to them and order them to listen to it! In that case, you'd be listening in the far field. Chances are that It would need electronic dipole compensation. It would certainly need neodynium magnets.

As you say, diffusors have become cheaper. I have some IPS ones from GIK and Vicoustics, but they're very resonant and I've come to suspect that they color the sound as a result. I'm going to try damping to see if it makes a difference. My major issues, though, is that the QRD's and skylines that I've tried all seem to color the sound because of their frequency-dependent lobing. The image loses its precision and starts to sound uncomfortably confused -- real music does have less localization, but it never gives the impression of being anything but "out there" -- and when I move my head, everything seems to change. So I'm thinking of trying polycylindricals instead. They don't alter phase, but maybe that's a good thing.

Another thing about polys is that they naturally do what you suggested, work as bass absorbers, if you stuff some insulation in them. They're relatively easy to make. This guy built some with MDF and 1/8" ply:

https://www.canuckaudiomart.com/forum/viewtopic.php?t=8520

I wonder what he's doing with the slap echo, though, because it isn't doing anything if it isn't at the listening seat!

What I do find number theoretic diffusers good for is, as he says, using them up close. The rule of thumb is 1 foot of distance per 1 inch of depth, but I've found that doesn't matter for the rear wall -- I have to sit too close to mine and they do a great job there and absorb some bass too if they have some 703 behind them. (I just learned though that Owens-Corning changed the formula of 703 and it no longer absorbs as well as it used to, so rock wool is probably the thing now. Doesn't matter, I already have enough 703 to insulate a palace.
 

DonH56

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You could always do a series/parallel arrangement with the tall ones -- impedance would oscillate from 4 to 6 to 8, but I think that's OK. A lot of guys have said they'd like a short version with a true ribbon, but now they'll be coming out with narrow ones instead, and that will likely include shorter narrow ones down market. I've lobbied them personally to make a Maggie mini monitor, a small point source dipole, but without success. (The Mini Maggies only work well in the near field because of power response issues.) I've though of throwing a couple together with a Neo 10 clone and a small true ribbon or a Neo 3 -- if it sounded good, I'd send it to them and order them to listen to it! In that case, you'd be listening in the far field. Chances are that It would need electronic dipole compensation. It would certainly need neodynium magnets.

As you say, diffusors have become cheaper. I have some IPS ones from GIK and Vicoustics, but they're very resonant and I've come to suspect that they color the sound as a result. I'm going to try damping to see if it makes a difference. My major issues, though, is that the QRD's and skylines that I've tried all seem to color the sound because of their frequency-dependent lobing. The image loses its precision and starts to sound uncomfortably confused -- real music does have less localization, but it never gives the impression of being anything but "out there" -- and when I move my head, everything seems to change. So I'm thinking of trying polycylindricals instead. They don't alter phase, but maybe that's a good thing.

Another thing about polys is that they naturally do what you suggested, work as bass absorbers, if you stuff some insulation in them. They're relatively easy to make. This guy built some with MDF and 1/8" ply:

https://www.canuckaudiomart.com/forum/viewtopic.php?t=8520

I wonder what he's doing with the slap echo, though, because it isn't doing anything if it isn't at the listening seat!

What I do find number theoretic diffusers good for is, as he says, using them up close. The rule of thumb is 1 foot of distance per 1 inch of depth, but I've found that doesn't matter for the rear wall -- I have to sit too close to mine and they do a great job there and absorb some bass too if they have some 703 behind them. (I just learned though that Owens-Corning changed the formula of 703 and it no longer absorbs as well as it used to, so rock wool is probably the thing now. Doesn't matter, I already have enough 703 to insulate a palace.

Re. series-parallel combinations: yes, that what I was thinking, but you would have to design a different crossover for each impedance, and make sure the right crossover goes with the panel arrangement. I don't think that's hard to do, but does add to the manufacturing steps. Given they are way backordered on their current models, I imagine adding complexity is not high on their priority list.
 
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