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Magnepan LRS Speaker Review

Shazb0t

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It absolutely is true
No, it's not. The Klippel NFS does a 360° measurement of a speaker to measure it's sound field. It doesn't matter where the sounds are coming from. It then uses those measurements of the sound field sphere to generate the speakers anechoic response on and off axis. These plotted frequency responses are just as accurate for the LRS as they are for any type of speaker. You don't have to like the measurement, and you could argue that it's designed to look the way it is, but this point source/dipole argument doesn't matter.

As far as reflections, they are calculated by mathematically taking that generated 360° sound field and calculating how the sound would propogate outwards and interact with walls, ceiling, floor in an "average" room as defined in the standard. You can argue that you don't like how the average room is defined, but again the method to determine this response is not wrong and has nothing to do with a point source or dipole bass.
 
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I have had 3 sets of MMG's, a set of MG1.6QR's and a set of .7's. Compared to the MMG and the 1.6, the .7 sounded (and measured) like it had a blanket thrown over it, plus it had an additional bass "hump" I did not experience with my other Maggies.

I'd say the 1.6's were my all time favorite speaker. They recently died of old age after many, many years of daily use.
 

josh358

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No, it's not. The Klippel NFS does a 360° measurement of a speaker to measure it's sound field. It doesn't matter where the sounds are coming from. It then uses those measurements of the sound field sphere to generate the speakers anechoic response on and off axis. These plotted frequency responses are just as accurate for the LRS as they are for any type of speaker. You don't have to like the measurement, and you could argue that it's designed to look the way it is, but this point source/dipole argument doesn't matter.

As far as reflections, they are calculated by mathematically taking that generated 360° sound field and calculating how the sound would propogate outwards and interact with walls, ceiling, floor in an "average" room as defined in the standard. You can argue that you don't like how the average room is defined, but again the method to determine this response is not wrong and has nothing to do with a point source or dipole bass.
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.

What you are apparently overlooking is the role of effective baffle side in dipole cancellation.

Fequal is determined by effective baffle size and shape. The effective baffle size and shape of a dipole in free space is not the same as the effective baffle size and shape of a dipole adjacent to one or more room boundaries. A small dipole on the floor, for example, will have twice the effective baffle area as a small dipole in free space, and that means Fequal will be higher and there will be significantly less dipole cancellation. The Klippel's sound field measurement has nothing to do with this phenomenon, and the calculations for room interaction for a monopole will fail when applied to a dipole, for more than one reason.
 

abdo123

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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.

What you are apparently overlooking is the role of effective baffle side in dipole cancellation.

Fequal is determined by effective baffle size and shape. The effective baffle size and shape of a dipole in free space is not the same as the effective baffle size and shape of a dipole adjacent to one or more room boundaries. A small dipole on the floor, for example, will have twice the effective baffle area as a small dipole in free space, and that means Fequal will be higher and there will be significantly less dipole cancellation. The Klippel's sound field measurement has nothing to do with this phenomenon, and the calculations for room interaction for a monopole will fail when applied to a dipole, for more than one reason.
the Klippel is perfectly capable of handling complex radiation patterns, it's things like the Olive preference score that cannot.
 

josh358

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the Klippel is perfectly capable of handling complex radiation patterns, it's things like the Olive preference score that cannot.
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.

To use an analogy, it would be like measuring a sealed woofer with the back of the cabinet removed. You'd get an accurate radiation pattern, but would it be useful without a fair amount of math?
 

DHT 845

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I'm curious whether it is a good idea to use LRS just for midrande 200 Hz - 2000 kHz in DIY project speakers and what tweeter to use for best integration... ?
 
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abdo123

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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.

To use an analogy, it would be like measuring a sealed woofer with the back of the cabinet removed. You'd get an accurate radiation pattern, but would it be useful without a fair amount of math?
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.
 
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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.
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.

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.

To use an analogy, it would be like measuring a sealed woofer with the back of the cabinet removed. You'd get an accurate radiation pattern, but would it be useful without a fair amount of math?
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?
 

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
 
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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.
 
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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.
 
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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.
 
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