Why don't all speaker manufacturers design for flat on-axis and smooth off-axis?

[Juhazi]

In JBL style, here is comparison of 208 vs M2 spinoramas http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor/page44

M2 measurements copied here. Two lowest lines are DI with different scale, not directly comparable to 208 above. M2 achieves higher DI by using a 15" woofer and a wide and moderately deep waveguide/horn for the compression driver. Deeper horrns give even higher DI, typical for PA speakers intended to be used in large spaces and long distance. High DI sort of means that radiated sound power is focused to a narrow beam and give higher efficiency on-axis.

 

[617]

You could, indeed. And I'm pretty sure that happened. But let's not forget that there's some serious technology in those drivers as well.

I mean it's a passive speaker with pretty conventional if high quality drivers in a wooden box. Nothing you can't get at Solen or Madisound. I think it's pretty well established Revel was using SB Acoustics for their ceramic cones and aluminum woofers although that may have changed. It's a carefully designed and marketed speaker but not fundamentally different from many others. That's a good thing in my book.

 

[617]

In JBL style, here is comparison of 208 vs M2 spinoramas http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor/page44

M2 measurements copied here. Two lowest lines are DI with different parameters and scale, not directly comparable to 208 above. M2 achives higher DI by using a 15" wooger and a wide and moderately doop waveguide/horn for the compression driver. Deeper horrns give even higher DI, typical for PA speakers intended to be used in large spaces and long distance. High DI sort of means that radiated sound power is focused to a narrow beam and give higher efficiency on-axis.

This is a really interesting comparison. To my eye the 208 looks better due to the greater continuity of the DI. The DI curve varies less with regards to frequency. The M2 has a tighter pattern down to a lower frequency but the DI transition is slightly more sudden. Both are excellent, however, and I can tell you that although it's easy to make a 3 way passive speaker that's pretty good, making one this smooth is a serious accomplishment.

 

[Krunok]

Two lowest lines are DI with different parameters and scale, not directly comparable to 208 above.

Why wouldn't they be comparable? They are in the same scale (5dB per line). And F208 DI lines look better to me.

Let's also not forget those 2 speakers are not in the same price range.

 

[Krunok]

M2 graph without watermark:

Looking at both graphs on the same page I can easilly imagine myself voting for F208 in a blind test.

M2's listening windows is more linear, but first reflections and total sound power looks smoother with F208. DI graphs as well.

 

[Juhazi]

The kind of DI curve that one aims for, is an importand design criterion/choice. It depends on the intended use of the speaker. It also gives typical sound character - it affects how on-axis and room response relate. It is a generally accepted thing, that sharp variations in DI are for bad. They can be compensated in on-axis response, but you should never look at one measurement only!

An educated listener knows what he wants and it is a modern trend to favor high and even deeply rising DI, because that gives you better stereo imaging and more tolerance to room reflections/speaker positioning.

Krunok - look at the response curves, there you can see the difference easier, below 1kHz (woofer range). The M2 doesn't show high DI even at high freq, that is exactly why it can be used at home with success.

Here is a good example of three high-end speakers with different DI curve, designed by kimmosto for a small company. They all are excellent but different. I sadly haven't heard them myself. (I couldn't link the response curves and spinoramas)
https://taipuuspeakers.fi/en/taipuu-speakers-dsp-active-speakers/

 

[Krunok]

The kind of DI curve that one aims for, is an importand design criterion/choice. It depends on the intended use of the speaker. It also gives typical sound character - it affects how on-axis and room response relate. It is a generally accepted thing, that sharp variations in DI are for bad. They can be compensated in on-axis response, but you should never look at one measurement only!

An educated listener knows what he wants and it is a modern trend to favor high and even deeply rising DI, because that gives you better stereo imaging and more tolerance to room reflections/speaker positioning.

I believe we all know that general stuff, so how about pointing exactly to the differences in graphs to make your point?
Btw, can we agree that DI graphs are comparable as the scales are identical?

 

[Krunok]

Here is a good example of three high-end speakers with different DI curve, designed by kimmosto for a small company. They all are excellent but different. I sadly haven't heard them myself. (I couldn't link the response curves and spinoramas)
https://taipuuspeakers.fi/en/taipuu-speakers-dsp-active-speakers/

Nice.. But again I don't really see that for example 4 way puts F208 to shame. Btw, what is the price of that 4-way?

4-way graphs:

 

[Krunok]

Krunok - look at the response curves, there you can see the difference easier, below 1kHz (woofer range). The M2 doesn't show high DI even at high freq, that is exactly why it can be used at home with success.

Heh.. I'm not sure I get what you mean. If I look at DI graphs at say 10kHz then F208 has both DI's lower than M2.

M2:
sound power DI: 9.5dB
early reflections DI: 5dB

F208:
sound power DI: 7.5dB
early reflections DI: 4dB

 

[Juhazi]

I guess that others read this thread too. One must understand a bit of the basic principles behind directivity of sound radiation, the influence of driver diameter and wavelength mainly. Price tag has zero effect to this!

Some material to study
https://www.sciencedirect.com/topics/engineering/directivity-index
http://www.mcsquared.com/speakers1.htm
http://www.linkwitzlab.com/Constant_directivity_louds.htm
https://www.holosonics.com/fundamental-limitations-of-loudspeaker-directivity
http://www.gedlee.com/Papers/directivity.pdf
https://pdfs.semanticscholar.org/1597/4783bbbbac11c8a864dcc9bee0a25af1c97d.pdf

Earlier I linked the Princeton 3D3a page, ther one can study how some 20 different speakers behave, and try to figure out what factors are causing those differencies.

Dr. Toole's book is a good collection of basics and examples of how directivity alters the perceived sound in a room. Here is a short article by him
https://www.audioholics.com/room-acoustics/sound-reproduction

 

[napilopez]

While we're talking about directivity/dispersion what do you guys personally prefer - narrow or wide? Toole prefers wide, geddess narrow.

I can go both ways... I think I once saw someone describe narrow directivity as transporting you to the recording location, and wide as inviting he musicians to your home. What say you?

 

[Juhazi]

Heh.. I'm not sure I get what you mean. If I look at DI graphs at say 10kHz then F208 has both DI's lower than M2.

M2:
sound power DI: 9.5dB
early reflections DI: 5dB

F208:
sound power DI: 7.5dB
early reflections DI: 4dB

Yes M2 has higher DI at 10kHz than F208, but not high at all compared to a deep horn or a panel speaker.

 

[Juhazi]

While we're talking about directivity/dispersion what do you guys personally prefer - narrow or wide? Toole prefers wide, geddess narrow.

I can go both ways... I think I once saw someone describe narrow directivity as transporting you to the recording location, and wide as inviting he musicians to your home. What say you?

I prefer dipole radiation pattern! But for monopoles I prefer low and smooth DI like Revel F208 over high DI and specially over highly rising DI like GedLee speakers had. And I listen most critically classical and live acoustic jazz. I want to feel like being in a large space rather than in the damped monitoring booth at studio.

 

[Bjorn]

B&Ws are a fixture in Harman studies. It is often disguised as speaker "B." Indeed it was among the pool of speakers when I participated in the blind tests:

View attachment 29538

It is the one to the left.

I scored the JBL the highest (on the right), then B&W and finally Martin Logan in the center.

Dipoles normally need a very different placement than monopoles to measure and sound the best. So Harman's research here may be seriously lacking. Another question that raises with a dipole is whether one should treat the front wall or not as this will have a great effect on the outcome.

Therefore I think we need to be very careful what we call absolutely science here. IMO too many are easily drawing conclusions based on these studies.

 

[napilopez]

Dipoles normally need a very different placement than monopoles to measure and sound the best. So Harman's research here may be seriously lacking. Another question that raises with a dipole is whether one should treat the front wall or not as this will have a great effect on the outcome.

Therefore I think we need to be very careful what we call absolutely science here. IMO too many are easily drawing conclusions based on these studies.

I do think the research on dipoles and other configurations is lacking, certainly relative to box speakers, and it's best if speakers that don't have the typical box radiation patterns are provided some leeway.

That said, I found the small section of Toole's book where he talks about non-traditional speaker designs and one particular model that performed well in blind listening tests: it was the Mirage M1 (a bipole, not a dipole as I'd thought earlier). Here's the relevant quote, from section 12.2.1 of the latest edition:

What about other designs, like dipoles, bipoles, and omnidirectional? Do the rules change? From what has been learned it seems that a flat direct sound followed by similar sounding reflected sounds (i.e., smoothly changing or constant directivity) produces sound that is highly rated by listeners. There is no stated requirement for any specific directivity, only that it be relatively constant across the frequency range above the transition frequency.

Unfortunately I do not have data to provide a comprehensive answer, but there is a piece of relevant data. As described in Section 7.4.6, the Mirage M1 was a bipole (bidirectional-in-phase) design that was very flat on-axis and, over much of its frequency range, approached horizontal omnidirectionality. In the NRCC double-blind listening tests it was very highly rated. Figure 12.5 shows the essential measurements.

As was found for forward-firing loudspeakers, a flat direct sound and relatively uniform directivity is sufficient to create a steady-state room curve that follows the trend of the idealized room curve. These data show that this conclusion applies also to a bipole loudspeaker measured in two rooms by two people. The downward slope of the room curve is therefore significantly attributable to rising room reflectivity at low frequencies and air attenuation at high frequencies.

Nonetheless, the fact he mentions he does not have the data to provide a comprehensive answer suggests there is more research to be done. As there always is .

 

[amirm]

Dipoles normally need a very different placement than monopoles to measure and sound the best.

I always see them placed just like normal box speakers. Here is their suite at CES 2017 I attended:

This is like every other speaker company at the show. Nothing special about them.

Here is RMAF 2017 show:

Again, just like any other speaker.

Axpona 2017:

Again, ordinary setup.

AXPONA 2016:

On and on. If the company doesn't do anything special with them, then it reasons that nothing special is required.

What I heard in double blind tests at Harman, I hear in all the demos of ML speakers ever since.

So while your argument is often made, I don't see it being relevant in my experience.

 

[amirm]

I should add that the powered subs with room correction has substantially improved the low-end of the ML speakers.

 

[MattHooper]

I should add that the powered subs with room correction has substantially improved the low-end of the ML speakers.

amirm,

I'm curious: When you listen to electrostatic hybrid designs, like those Martin Logan speakers, do you find yourself noticing any form of discontinuity between the woofer section and the panel section?

Personally I have never been able to get along with any hybrid I've ever heard, which includes many MLs, as I perceive a different type of quality between the bass/dynamic driver section and the panel section. The panel, like every electrostatic I've heard (I owned Quad ESL 63s) have a ghostly lack of "body" where the dynamic driver/woofer has that sense of body. So for instance a bass guitar in the lower range can sound like a solid air-moving object but, say, a flute, alto sax, or whatever just doesn't have that sense of dense, air-moving presence.

(It's why I gave up on electrostatics). So I'm just curious if you perceive things differently.

 

[MZKM]

It's an interesting point. When does a dipole work well?
I will be the first to admit that I have next to no experience of dipoles. Being devil's advocate, do they work well when the negative effects of being a dipole are mitigated by the room and position.? What I mean by that is when they are prevented from behaving too much like dipoles and more like conventional box speakers

All I can say is that the notions of a minuscule sweet spot are very true. I was at an audio show and in one of the large rooms (much larger than the hotel suites, but not as large as a banquet hall) were the $80,000 MartinLogan Neolith’s, I was with my father and when we sat down to listen to them (me being in the sweet spot), my father said that he only heard one speaker playing and asked why, me knowing the stereotype, we switched places and the difference was indeed large.

Edit: photo:

The other half (behind us) they were showing of their box speakers.

 

[MattHooper]

All I can say is that the notions of a minuscule sweet spot is very true. I was at an audio show and in one of the large rooms (much larger than the hotel suites, but not as large as a banquet hall ) were the $80,000 MartinLogan Neolith’s, I was with my father and when we sat down to listen to them (me being in the sweet spot), my father said that he only heard one speaker playing and asked why, me knowing the stereotype, we switched places and the difference was indeed large.

Yeah, it's amazing how long I've heard "ML used to be more sweet-spot finicky, but curving those panels really helps widen the sweet spot."

Nope..nope...nope. Not once have I encountered a ML speaker that didn't have a super picky, narrow sweet spot, including their flagship. Nature of the beast. Looks like one has to do something more radical like Muraudio. (Or, actually, I seem to remember my Quad 63s had a slightly wider sweet spot for a panel speaker, presumably due to the concentric radiator "point source" design of the panel).