Room Acoustics with "exotic" speakers - AVS Forum
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post #1 of 18 Old 03-24-2012, 09:17 PM - Thread Starter
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This is a somewhat random question I've had rattling around for a while, and haven't found anything conclusive to answer it. Before you read further: this thread will mention a certain un-popular speaker manufacturer (Bose), and is not meant to be a discussion of the merits or value proposition of that manufacturer's products.

So what I'm curious about is:
There's lots of nice articles, videos, demos, books, etc that deal with placement and treatment for listening spaces, but they usually all assume you've got a conventional pair (or quartet or whatever) of speakers; like (to pick a random example) the Polk Monitor 50. But what about when you get into speakers that are a lot less conventional, like the Bose 901 and 301, Sansui SF, Mirage OMD, B&O BeoLab 5, MartinLogan and Quad stats, Sony NSA-PF1, some of the Technics Linear Phase models, Klipschorns, and other "oddlings" that do not fit the "box with some drivers in the face" design. And before anyone gets bothered - no I am not insisting that all of the above are equals or equivalent in ability or design, they're just examples of "exotic" designs that (probably with the exception of the BeoLab 5) are not cost prohibitive to many users.

My "best educated guess" is that diffusers are probably the name of the game, but I could be entirely off base. Thoughts?
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post #2 of 18 Old 03-24-2012, 09:36 PM
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The starting point is to know the free space polar response of the speaker in question. From there you can decide whether to buy or I suppose in your version as posed to keep it. And/or if you must keep it to have some idea of what to expect in room. This may, perhaps, also guide how you choose to design the room to either complement or try to correct for the speaker. For instance a quad stat may need stronger front wall absorption or diffusion and less side wall. You might decide to leverage the beolab to create an extremely dense diffused soundfield while a klipsch might prompt you to consider a more damped environment with 22 channels of very directional speakers and quite a bit of hefty surround processing.

In any case, no matter the speaker, the next step is measure in room, see what you've got, compared to what you expected, and start chipping away from there as best as possible.

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post #3 of 18 Old 03-24-2012, 09:43 PM
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It's going to depend upon the speaker's dispersion characteristics, listening position and placement in the room, and of course the room.

Khorns (and LS and H) as well as my own design controlled directivity designs I can comment some on. Correctly placed in a room Khorns need very little as they don't illuminate the side walls or floor/ceiling much, and same, to a lesser extent with the CD types. Placed and angled correctly so the axes cross in front of the LP most reflections should be outside the precedence thresholds, but some damping will help control flutter echo etc. Rear wall dispersion could likely help depending upon how far from the rear wall you are and the diffuser chosen.

All 6 of my speakers are CD designs (no C, multiple subs) and the above is the general approach I will take, once they are in situ and I can take some measurements. Some sidewall damping, a rear wall diffuser (I'm about 3m away), probably PRD some bass trapping and a thick futon day lounge as an ottoman/footrest to reduce floor bounce from the mains.

None of the other designs you mention interest me in the least, so I haven't considered what I might do if I had them.
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post #4 of 18 Old 03-24-2012, 09:48 PM - Thread Starter
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Quote:
Originally Posted by Bigus View Post

In any case, no matter the speaker, the next step is measure in room, see what you've got, compared to what you expected, and start chipping away from there as best as possible.

That's about what I was figuring in a generalistic sense.

Also - Khorns and 22 channels of audio...
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post #5 of 18 Old 03-25-2012, 04:26 AM
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Quote:
Originally Posted by walbert View Post

There's lots of nice articles, videos, demos, books, etc that deal with placement and treatment for listening spaces, but they usually all assume you've got a conventional pair (or quartet or whatever) of speakers; like (to pick a random example) the Polk Monitor 50. But what about when you get into speakers that are a lot less conventional, like the Bose 901 and 301, Sansui SF, Mirage OMD, B&O BeoLab 5, MartinLogan and Quad stats, Sony NSA-PF1, some of the Technics Linear Phase models, Klipschorns, and other "oddlings" that do not fit the "box with some drivers in the face" design. And before anyone gets bothered - no I am not insisting that all of the above are equals or equivalent in ability or design, they're just examples of "exotic" designs that (probably with the exception of the BeoLab 5) are not cost prohibitive to many users.

These speakers aren't all that different below say, 200-500 Hz where you get a lot of the benefits of some common kinds of treatments such as bass traps. They are all essentially omnidirectional. I wouldn't expect a lot of difference in how sound treatments targeting the lower ranges work with them.

Your list of speakers is a mixed bag. Some are less directional than average and some are more.

The less directional or more omnidirectional speakers are going to be more affected by treatments on back and side walls, in all liklihood. But again these speakers may be somewhat omnidirectional, but they still throw a lot sound forward, and that what treatments to the back wall target.

The more directional speakers are going to be less affected by the same kinds of room treatments as I mentioned in the previous paragraph.

Probably your biggest advantage for typical sound treatments will probably come with speakers whose directivity changes the most, such as 2-way speakers with large lower range drivers, and any speaker whose lower range speaker is smallish - less than 6-8 inches. This is because their pattern changes with frequency, or lack of directional control in the midrange and below are probably disadvantages.
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post #6 of 18 Old 03-25-2012, 07:28 AM
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It all depends on what speakers you are using-what "theory" they are trying to use-and what you are trying to accomplish in the room.

You FIRST have to ask yourself these questions.
1: Am I trying to have an experience the same as the engineer that recorded the material did? Ie accuracy to the origional recording.

OR 2: Am I trying to have a "different" experience than the origional. For example "being surrounded by sound" and engulfed in the experience?

Those are 2 VERY different situations-that require 2 very different approaches-both in the choice of loudspaker and choice of room treatments-speaker layout etc.

You CANNOT accurately reproduce the material AND have a different experience at the same time.

I love the old Paul Harvey Bose commericials. He says that he and his wife just love to go to the symphony. But they like even more to listen to the symphony at home on their Bose system-because of the way it sounds.

Excuse me-but a LIVE symphony in a concert hall is as real as it gets. It is THE MOST accurate-because it is itself.

If he likes the "sound" better at home-then that is a statement that the Bose is not accurate.

I know that is not the idea he is trying to get across-and most people simply ignore the facts-but you can't get any more real or accurate than the origional thing. You can only change it. You may like it better-that is up to you-but it is no longer accurate.

Take for example a "normal" loudspeaker and treat to the room so as to get rid of reflections (specifically behind and beside the loudspeaker) so that the sound that comes from the loudspeaker is not (or minimally) affected by the room. You mostly hear the direct sound from the loudspeaker.

Now put a Bose 901 (in the proper intended position) with the single speaker facing forward and the other 8 facing the rear.

Since the room is treated (the walls behind and beside the loudspeaker) the whole "idea" of the 901 falls apart-since the energy that is "supposed" to bounce around the room and "surround you" is now being absorbed by the room treatments.

So think about what you want out of a system (and the system is the loudspeakers AND the room)-THEN go about getting it.

Most people don't think about what they are trying to "accomplish" with a sound system-they just go and "get stuff" that is recommended by somebody who may have a different idea in mind.

You may not like what I like-but that does not mean it is right or wrong.

Accuracy or experience-THAT is the question.

Danley Sound Labs

Physics-not fads
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post #7 of 18 Old 03-25-2012, 11:25 AM
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Quote:
Originally Posted by Ivan Beaver View Post

Now put a Bose 901 (in the proper intended position) with the single speaker facing forward and the other 8 facing the rear.

Since the room is treated (the walls behind and beside the loudspeaker) the whole "idea" of the 901 falls apart-since the energy that is "supposed" to bounce around the room and "surround you" is now being absorbed by the room treatments.

Your assumptions seems to be absorption. If the room treatment consisted of lots of PRDs placed around the room, especially behind and beside (outer walls) 901's then that would seem to be the best approach for these speakers than simply hoping the basic walls will do the job adequately.
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post #8 of 18 Old 03-25-2012, 12:31 PM
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Quote:
Originally Posted by A9X-308 View Post

Your assumptions seems to be absorption. If the room treatment consisted of lots of PRDs placed around the room, especially behind and beside (outer walls) 901's then that would seem to be the best approach for these speakers than simply hoping the basic walls will do the job adequately.

what size PRDs are we talking here? are they effective to the lower specular cut-off, or would they merely alter the spectral balance of the reflection?
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post #9 of 18 Old 03-25-2012, 12:59 PM
 
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Quote:
Originally Posted by localhost127 View Post

what size PRDs are we talking here? are they effective to the lower specular cut-off, or would they merely alter the spectral balance of the reflection?

Suppose they were PRDs big enough for little JBL Studio wallmounts. How would that affect the measurements? Localhost, you could show us by posting your ETC, ETC, ETC, ETCs in your room and then explain the perceptual relevance in terms of accuracy to the recording made with UREIs
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post #10 of 18 Old 03-25-2012, 01:05 PM
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i must have really struck a nerve, emotionally. he's following me into other threads now!
quite the professional, albeit at 1/6 smoothing.
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post #11 of 18 Old 03-25-2012, 01:24 PM
 
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Quote:
Originally Posted by localhost127 View Post

i must have really struck a nerve, emotionally. he's following me into other threads now!
quite the professional, albeit at 1/6 smoothing.

So you don't have any measurements whatsoever? None? You don't know how and have never done any ETCs like you preach? Hmmm.
So your opinion that you are getting accuracy from your JBL wallmounts in your "critical listening" environment is completely subjective, no objective data whatsoever?
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post #12 of 18 Old 03-25-2012, 01:49 PM
 
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Quote:
Originally Posted by walbert View Post

But what about when you get into speakers that are a lot less conventional, like the Bose 901....

http://www.tonepublications.com/revi...-the-bose-901/
Did a double take when I saw it, but yep, there it is in all it's reviled glory...

cheers,

AJ
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post #13 of 18 Old 03-25-2012, 02:56 PM
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Ya know...

Some self proclaimed hi-end speaker "manufactures" spend a *lot* of time in different forums implying and flat out stating that the room, and adjusting the room's acoustical parameters such as standing wave behaviour and reflective surfaces to balance out the the speaker behaviour and how it interacts with the room to achieve a better listening experience, is completely unimportant and wrong.

They seem to often state that "room treatment" it is a seriously bad approach for good sound reproduction -in fact some of them somewhat naiively state nonsense in forums like this along the lines that "Bandaids and gauze can't cure cancer. Only ease the pain and other such symptoms. Treating the source can."

Their belief, it seems, is that they've (naturally )found a divine way of creating a divine speaker design that will in some *magical* way will be able to take full advantage of each lsitening rooms's positive contributions to the listening experience and stereo illusion, and at the same time remove every single negative contribution that there has ever been from a pair of speakers placed in *any* room. All this without any sort of adjustment, other than perhaps *placement* of their oh, so "divine" one-fits-all speaker design (I whish they'd been in the shoe buissness instead of speakers ).

Now, sometimes I like to beleave I have a pretty decent understanding on what different dispersion patterns do to the stereo illusion, with several dynamic dipole designs including Linkwitz Orion's passing by my listening space, as well as a couple of cardio-designs from Gradient, the occational transmission audio baffles etc, and my personal experience is that it all boils down to speaker room combination and what parameters you think is important.

So, I'm allways laughing (andI bet a fair amount of knowledgable people laugh with me) when "manufacturers" claim they have the sealed the "golden nugget" in forums like this with the right sound for any room, and they still, somehow need to produce speakers that are of completely different designs depending on price tag!?!

Does this devine speaker have to change design to work in different rooms if the buyer have more money to spend?!? Sounds strange to me...

Like, for example, some manufacturers that promote a semi-expensive coax+actively powered bass design that is semi-omnipolar and at the same time they push a coax/cardio-bass (=a ripp of, of Gradient Speakers)?

There's no way in hell tose two will sound even remotely alike in every room at the same listeing level regardless of placement! What's up with that!?!

Go figure.

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post #14 of 18 Old 03-25-2012, 03:39 PM
 
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This looks like a nice, appealing living room environment for "critical listening":



Perfect
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post #15 of 18 Old 03-25-2012, 04:27 PM
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Quote:
Originally Posted by AJinFLA View Post

This looks like a nice, appealing living room environment for "critical listening":


To me it looks like a decent environment created at a hifi-fare or other type of Commercial venue to approach the sonic fidelity and other design goals that the designer of this particual speaker set out to achieve *combining* the speakers and the room interaction.

But that's just me (and, it seems, my view aligns pretty well with the majority of other forum members...). Anyone care to take a shot at this other than AJ? Anyone? No? No...

So, what about your designs, then? You seem to need to use fundamentally different speaker designs approaches/radiation patterns depending on the customers' wallet? Does the room contribution change with the custmers wallet? What's the physichs behind that? Care to share or is it your Little secret?

Is it perhaps the redicilous silver wires or perhaps the Power Conditioner you used at the demo that equalizes the room's detrimental contributions and enhances each rooms positive contributions. Yes?!?

Quote:
Originally Posted by AJinFLA View Post

All cabling was WyWires Silver series (USB, ICs, power and speaker wires). Power conditioner was a Pi Audio Group MajikBUSS (RevB).

You really crack me up, man!

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post #16 of 18 Old 03-25-2012, 05:29 PM - Thread Starter
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Ivan, A9X, Local, Arny, and Hevi:

Thanks for the replies .

So based on what's been said about the Khorns and 901s (and remember, this is nothing I'm building!), and Arny's post (I was assuming handling LF was more or less uniform for all of them, but thanks for confirming), if you picked up something like the Sony or the Sansuis, I'm assuming damping *and* PRDs would be needed (diffusion beside/behind the speakers, and damping/absorption on the backwall?); I haven't seen polar plots for the Sony, but the Sansui SF polar plot is almost a complete circle (as published by Sansui, who knows how much they smoothed it or milked it though - they're spec'ing that 400-20k, and the speaker is +/- 3 50-20k (they are *odd* speakers, I've had a chance to hear them in a domestic setting before)).
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post #17 of 18 Old 03-26-2012, 02:53 AM
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Quote:
Originally Posted by localhost127 View Post

what size PRDs are we talking here? are they effective to the lower specular cut-off, or would they merely alter the spectral balance of the reflection?

At 525am as I was getting ready to leave for work, I hadn't worked out any detail. I was merely thinking out loud on whether a diffusive approach (vs absorption) might be of benefit to these speakers. I hadn't thought out specifics, but anything from a thin 50mm well depth commercial unit to Blackbird Control Room, and would be interested to hear your take on either approach for these.
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post #18 of 18 Old 03-26-2012, 05:37 AM
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Quote:
Originally Posted by AJinFLA View Post

This looks like a nice, appealing living room environment for "critical listening":



Perfect

Looks to me like heavy curtains, which are better than a kick in the head sometimes, but pretty wimpy as broadband absorbers.

Here's a reasonably concise table that covers a lot of relevant materials:

http://www.sae.edu/reference_materia...nt%20Chart.htm]


Here is glass fiber board (4")

125 250 500 1000 2000 5000

0.99 0.99 0.99 0.99 0.99 0.97

Here is the heaviest curtain material listed:

125 250 500 1000 2000 5000

0.14 0.35 0.53 0.75 0.79 0.60
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