What makes speakers "disappear " and can it be measured?

[Thomas_A]

With forward-firing loudspeakers the sound radiated to the rear is dominated by bass frequencies - as loudspeakers tend towards omnidirectIonality at low frequencies. This means that any absorbing material must be effective at long wavelengths, so "fluff" would need to be impractically deep, and membrane absorbers tend to be frequency selective, although a few commercial products are fairly broadband. Not simple. It turns out that

Section 9.2 in the 3rd edition addresses the issue of adjacent boundary effects. It is essentially an issue of radiated energy which is amenable to equalization based on a generous spatial average. But it cannot be completely eliminated. What remains seems to be accommodated by adaptation.

In-wall speakers? You can also use very near wall speakers to raise the frequency making it more essy to absorb. .

 

[Floyd Toole]

I still can't believe he's participating in a thread I started

Hey, I'm retired and now have some time to spare. I can't take it with me, so it is a pleasure to share some of my experiences and knowledge. However, from time to time I do take "holidays" from forums (smile).

 

[Floyd Toole]

yes aometimes it is not embedded in the recording. Sometimes it is. In either case, adding a new one is of no benefit IMO.

For classical concert recordings the microphones are not located in the audience. Normally they are close to and above the instruments, and there are several of them, some close to instruments, some farther away, and a small number much farther away to collect some hall sound. The final product is a mix of them all. Consequently any evidence of "floor bounce" that is in the recordings is not at all coherent or consistent, and none are as would be heard by an audience. Forget about it.

 

[Thomas_A]

For classical concert recordings the microphones are not located in the audience. Normally they are close to and above the instruments, and there are several of them, some close to instruments, some farther away, and a small number much farther away to collect some hall sound. The final product is a mix of them all. Consequently any evidence of "floor bounce" that is in the recordings is not at all coherent or consistent, and none are as would be heard by an audience. Forget about it.

But as mentioned sitting in the audience would not include floor bounce either. Just a bunch of seats and people. Where is the benefit to add one in your room?

 

[Floyd Toole]

In-wall speakers? You can also use very near wall speakers to raise the frequency making it more essy to absorb. .

In-wall/ in-ceiling loudspeakers can be excellent if designed properly. I have used them in very demanding applications with excellent results. On-wall speakers can also be excellent, but again, if the acoustic design includes the wall. These will be low-profile designs. Properly designed on-wall speakers are fundamentally different from conventional speakers on (or close to) a wall. See Section 9.3 in the 3rd edition for measurements of several boundary interface situations, and Section 9.4 for a discussion of "boundary-friendly loudspeaker designs".

 

[Newman]

I also recall @Floyd Toole in his first book, IIRC, concluding that all this talk about side wall reflections is really just for stereo reproduction, because of the inherent limitations of stereo at creating impressions of apparent source width and envelopment.…

If we want next-level experiences in soundscapes at home, then go multichannel, point the speakers at the listener(s), and give no regard to reflections off the near side walls, other than ensuring that they don't contribute negatively.

(And now I'm hoping I have not misrepresented Dr Toole.)

…With real surround channels and speakers all this chatter about listening room reflections suddenly becomes almost irrelevant. It is time to move on...

Good to see confirmation and that I have not misrepresented you! Because I have carried this message across various forums over the years.

Question, however. The committed “multichannel is for movies” stereophile has a couple of standard retorts to the above:-

• “Every time I have heard music in surround sound I have hated it. It is terribly unrealistic.” (And sometimes they can’t help adding a dig: “especially compared to LP”.)
• “For any given amount of dollars of speaker budget (and we all have a limit), one gets vastly better sound quality if it is all spent on 2 speakers than on 5, or, horrors, 11.”

What do you think of the second one? 2 Ultima2’s, or 5 F226Be’s, or 11 M126Be’s? For example.

cheers

 

[Blumlein 88]

Good to see confirmation and that I have not misrepresented you! Because I have carried this message across various forums over the years.

Question, however. The committed “multichannel is for movies” stereophile has a couple of standard retorts to the above:-

• “Every time I have heard music in surround sound I have hated it. It is terribly unrealistic.” (And sometimes they can’t help adding a dig: “especially compared to LP”.)
• “For any given amount of dollars of speaker budget (and we all have a limit), one gets vastly better sound quality if it is all spent on 2 speakers than on 5, or, horrors, 11.”

What do you think of the second one? 2 Ultima2’s, or 5 F226Be’s, or 11 M126Be’s? For example.

cheers

I'd go with 5 F226Be's if I get to add a sub as well.

 

[Kal Rubinson]

Question, however. The committed “multichannel is for movies” stereophile has a couple of standard retorts to the above:-

I had to dispute that statement to convince the (then) publisher to let me publish my (erstwhile) column, Music in the Round and I continue to review multichannel products. Unfortunately, most of the reviewers are less enthusiastic about multichannel than I am.

 

[Floyd Toole]

But as mentioned sitting in the audience would not include floor bounce either. Just a bunch of seats and people. Where is the benefit to add one in your room?

The "bunch of seats and people" do indeed corrupt a well organized floor reflection from the audience floor - but not the stage floor. The same seats and people do however create a strong and audible "seat dip effect" - a fairly wide and deep dip in the frequency response around 100-200 Hz. Which one is worse? I wonder. But my favorite seats have been within the first 3 rows of the front balcony, mezzanine, terrace (whatever the first elevated level is called) where the seat dip effect has not been able to develop. Perfection is hard to find. I also like the experience of looking slightly down on the orchestra.

 

[Doodski]

(whatever the first elevated level is called)

It's called the dress circle. Nowadays many people simply refer to it as the circle.

I also like the experience of looking slightly down on the orchestra.

I had the pleasure of attending Phantom of the Opera and sat in the left side first balcony overlooking the stage. What a great view. It was wonderful when the chandelier almost fell on the crowd. They apparently fake that chandelier falling at all theatres where The Phantom of the Opera goes.

 

[Floyd Toole]

Good to see confirmation and that I have not misrepresented you! Because I have carried this message across various forums over the years.

Question, however. The committed “multichannel is for movies” stereophile has a couple of standard retorts to the above:-

• “Every time I have heard music in surround sound I have hated it. It is terribly unrealistic.” (And sometimes they can’t help adding a dig: “especially compared to LP”.)
• “For any given amount of dollars of speaker budget (and we all have a limit), one gets vastly better sound quality if it is all spent on 2 speakers than on 5, or, horrors, 11.”

What do you think of the second one? 2 Ultima2’s, or 5 F226Be’s, or 11 M126Be’s? For example.

cheers

A great bang-for-the-buck question. First, there is good information that a 5 channel system can do an excellent job of replicating the perceived and measured envelopment of 12 and 24 surrounding channels - Section 15.7.1 in the 3rd edition. We also know that achieving truly good bass in small rooms is best done with 2 or 4 subwoofers in specific locations - not those locations that are optimum for the 5 satellite speakers - so why spend money on floor standers that are not as good at low frequencies as "real" subs. Consequently, my answer to your question is none that you suggested, but rather 5 M126Bes and 2 or 4 good subwoofers in a bass managed scheme. I have 7 base-channel speakers, 6 elevated speakers - all of which are high-pass filtered at 80 Hz - and 4 subwoofers in a "Sound Field Managed" (using digital processing in each sub feed) scheme (Section 8.2.8 in the 3rd edition). Simpler, lower cost solutions are possible as described in the same chapter. Multiple subs in one of these arrays can be small because as a group there are significant efficiency gains.

Anyone promoting LPs does not understand, or won't admit, that the signal that is extracted from an LP cannot be the same as the master recording. Cannot = can not! So, such people are content not to hear the art as it was created. This is provable fact, not my opinion. LPs are interesting as historical memorabilia, as are old cars, replicas of old cars, etc., which is absolutely fine - I would love to have an old Chevy to cruise around in on a sunny Sunday morning, but I have zero interest in LPs for enjoying music. Let the flames begin . . .

 

[Newman]

….and I will now scurry back to re-read the sections you have referenced in your books.

Y’know, more people really should be reading your books….slowly!

cheers

 

[Thomas_A]

The "bunch of seats and people" do indeed corrupt a well organized floor reflection from the audience floor - but not the stage floor. The same seats and people do however create a strong and audible "seat dip effect" - a fairly wide and deep dip in the frequency response around 100-200 Hz. Which one is worse? I wonder. But my favorite seats have been within the first 3 rows of the front balcony, mezzanine, terrace (whatever the first elevated level is called) where the seat dip effect has not been able to develop. Perfection is hard to find. I also like the experience of looking slightly down on the orchestra.

Thanks for the info. Siitting in a lounge or balcony will indeed be different so nowhere there is a consistent effect from the floor like that one at home. In addition, there are other excellent two-mic recordings e.g. Bertil Alvings Cantate Domino and others (BIS) that siimply do not use multi-microphones placed around orchestras. Putting thick absorbers on the floor is one thing which makes the room "floorless" making the room most probably an unpleasant environment as anechoic rooms tend to be. Having a table in front of the listening seats/sofa blocks the first reflection but leaves the rest of the floor intact, give or take a carpet absorbing high frequencies.. So, I am still not convinced that the primary floor reflection should be added at home. As I see it, it makes it just easier to localise the speakers.

http://audiogroup.web.th-koeln.de/PUBLIKATIONEN/Ebelt_DAGA2016.pdf

 

[Frgirard]

….and I will now scurry back to re-read the sections you have referenced in your books.

Y’know, more people really should be reading your books….slowly!

cheers

The Toole book is our Bible. We all read it. On Gearslutz it's a bestseller.

For me the 2008 edition.

 

[Frgirard]

Putting thick absorbers on the floor is one thing which makes the room "floorless" making the room most probably an unpleasant environment as anechoic rooms tend to be.

it's not my experience. The room at the listening position is quiet. Its a soothing sensation.

The studio designed with the non environmental design are not anechoic chamber.

 

[Thomas_A]

it's not my experience. The room at the listening position is quiet. Its a soothing sensation.

My experiience with too much absorption is howewver negative. Adding it at the spekaer wall side in moderate amount gives to me higher dynamics and quiteness in silent parts. Also, there is an feeling of needing more amplifier power, and to turn up the volume. The rest of the room has no special treatment. It sounds fine by me.

 

[Frgirard]

My experiience with too much absorption is howewver negative. Adding it at the spekaer wall side in moderate amount gives to me higher dynamics and quiteness in silent parts. Also, there is an feeling of needing more amplifier power, and to turn up the volume. The rest of the room has no special treatment. It sounds fine by me.

All studio (99% except the ambechoic) on the planet works with an heavy absorption.
The room sound against the speakers sound.
I choose the speakers sound.

 

[Tangband]

Thanks for the info. Siitting in a lounge or balcony will indeed be different so nowhere there is a consistent effect from the floor like that one at home. In addition, there are other excellent two-mic recordings e.g. Bertil Alvings Cantate Domino and others (BIS) that siimply do not use multi-microphones placed around orchestras. Putting thick absorbers on the floor is one thing which makes the room "floorless" making the room most probably an unpleasant environment as anechoic rooms tend to be. Having a table in front of the listening seats/sofa blocks the first reflection but leaves the rest of the floor intact, give or take a carpet absorbing high frequencies.. So, I am still not convinced that the primary floor reflection should be added at home. As I see it, it makes it just easier to localise the speakers.

http://audiogroup.web.th-koeln.de/PUBLIKATIONEN/Ebelt_DAGA2016.pdf

Thanks for the document. Very interesting reading.

My own recording tecnique with only 2 omni-mics ( done in almost the same way as Bertil Alvings, after his personal advice but at amateur level ) shows that the early reflections wall/floor/ to microphones, up to aprox. 5 ms indeed are disturbing and should be avoided. You have to have the two omni-mics at a certain hight above the floor, or away from the nearest wall . The early reflections 1-5 ms is disturbing both when recording real instruments with 2 microphones in the concert hall, and when you are listening at your loudspeakers in your home. Having your loudspeakers placed on a loudspeakerstand, a thick rug on the floor, and the sidewalls more than 5 ms away, is good practice.

Edit : When recording a cello, the floor-bounce is ofcourse a part of the cello sound and must be on the recording. But having a wall only 85 cm ( 85 *2 =170 cm = 5 ms ) or less away from the microphones, will make the recording sound less clear.

And the opposite happens - more than 20 ms delayed wall-reflexes from the cello/wall/microphones in the recording situation, is bringing depth and space to the 2-channel recording. The same happens in your listening room with two loudspeakers, with a bigger room.

 

[Frgirard]

Thanks for the document. Very interesting reading.

My own recording tecnique with only 2 omni-mics ( done in almost the same way as Bertil Alvings, after his personal advice but at amateur level ) shows that the early reflections wall/floor/ to microphones, up to aprox. 5 ms indeed are disturbing and should be avoided. You have to have the two omni-mics at a certain hight above the floor, or away from the nearest wall . The early reflections 1-5 ms is disturbing both when recording real instruments with 2 microphones in the concert hall, and when you are listening at your loudspeakers in your home. Having your loudspeakers placed on a loudspeakerstand, a thick rug on the floor, and the sidewalls more than 5 ms away, is good practice.

Edit : When recording a cello, the floor-bounce is ofcourse a part of the cello sound and must be on the recording. But having a wall only 85 cm ( 85 *2 =170 cm = 5 ms ) or less away from the microphones, will make the recording sound less clear.

And the opposite happens - more than 20 ms delayed wall-reflexes from the choir/wall/microphones in the recording situation, is bringing depth and space to the 2-channel recording. The same happens in your listening room with two loudspeakers, with a bigger room.

With a piano and the two mics in the piano?

 

[Tangband]

With a piano and the two mics in the piano?

I often record a classical grand-piano with two omni-mics at 52-42 cm appart, the two mics at the hight from the floor of 155 cm, and 90 cm from the strings. Piano lid entirely open. The critical distance in the room should then be about 50/50% depending on the room acoustic. The piano should be placed about 4-5 meters from nearest wall, ideally made of stone/concrete.

If you place the mics really near the pianostrings, for example 10 cm away, you only get direct sound from the piano, and no acoustics.