Treating the entire front wall - Bob/Z?

Posted: Wed Mar 30, 2005 3:30 pm

Since the sweet spots in a control room and a home theater are different sizes, a control room--especially for stereo--can be more live (and therefore more natural), I would think, no? But the only way you could hope for a home theater to accomodate good listening in 8 different chairs, I would think you'd need to deaden the room more to allow the direct sound from the speakers to be more determinant of what you hear at any given point. Or am I forgetting something here?

Lee

Posted: Wed Mar 30, 2005 3:53 pm

The idea of a HT being the same as a surround sound control room is perfect in my mind. Just reproduce the conditions that the recording/mastering engineer had and the original creative intent should shine.
The problems start in HT when people let aesthetics affect things. They rarely are happy with 5 speakers on an equal radius from the listening position as it puts all but the centre speaker out in the floor somewhere. This leads to wall mounted speakers, ceiling mounted etc. Dipoles etc then pop up to try to create some envelopment that is even even if a lot of the steering capability has gone.
Now there are speakers everywhere and often some are facing the front wall. I think the treat the front wall idea is to reduce reflections from rear speakers interfering with the front speaker radiated sound.
1" glasswool may not be broadband or balanced but it sure beats a hard front wall sending rear speaker reflections straight back.

Posted: Wed Mar 30, 2005 3:59 pm

Paul wrote:
Once I've finished my studio and have some leisure time again, I'm gonna do something similar again. Great entertainment.

You shouldn't make fun of stupid people, Paul Wink

And everybody knows that straight speaker cables sound better than bended ones, as long as the current flows in the right direction!

Posted: Wed Mar 30, 2005 4:32 pm

Paul,

I'm really sorry, but you make your believes as well truths.

Yours and Mark's control room is one type of room, not THE only possible room.

I have been invited to listen to speaker cables with blind tests, and they could recognize significant part of them.
I don't judge good, better or bad. I only know they did.

I have been involved in tests were speakers were set on top of decouplers to hear this possible phase shift (the thing you tell because you heard it from others).

And I'm a dry NON-believer when I hear such stories.

I even thought people were crazy when they invited me to listen to cables. I thought I misunderstood their invitation.
I WAS there, and was VERY attentive that this blind test really was a blind test.

So while being not an expert at all, I am a critical bystander, almost more busy checking that they don't cheat me nor themselves.

Posted: Wed Mar 30, 2005 5:34 pm

Again, Some speaker designs are meant to reflect sound off of the front wall (L/C/R not rear surronds) if you add absorbtion to that wall you destroy the speakers sound. Bi/Dipole designs like Def Tech and electrostatic designs like Martin Logan (thanks Z) would sound lifeless in such a room. These are not nearfield monitors and can't be treated as such.

A HT is not a control room with one person sitting in the sweet spot. It has many seating positions that must be taken into account when dealing with accoustics. The statement that a HT buff would love a control room may be true if he's seated in the engineers seat but I doubt he'd prefer it from any other position.

It was also stated that the reason for treating the front wall is to avoid reflections from the surrounds. Are you kidding? First in a 5.1 system the surrounds face left/right not front/back so reflections off of the front wall wouldn't even be an issue. In 6.1 and 7.1 systems you do have 1 or 2 front facing speakers but these shouldn't be an issue either, if it is your playing them TOO DAMN LOUD.

In a proper HT set up the speaker volumes are set from the listening position (mine are within 1/2 db of each other), this makes the surrounds considerably quieter than the L/C/R since they are positioned within a few feet or less of your ears.

I really doubt you would hear the reflections at such low volume but if it really is a problem why not just treat the upper half of the front wall since surrounds should be placed around 6 feet or higher above the floor. You could also treat only the lower half of the rear wall to avoid reflections from the L/C/R. This would preserve the characteristics of Bi/Dipole designs and still prevent undesireable reflections from reaching your ears.

Apples and Oranges, Control Rooms and Home Theater, I see very little that they have in common.

JMO

Posted: Wed Mar 30, 2005 6:21 pm

Ethan Winer wrote:

Quote:

> So what's wrong with a school of thought that says make your listening room like a control room? <

That's exactly what I think too. Some/many/most audiophiles and home theater designers dispute this vehemently.

????
Waleters Storyk Desigb Group?
Francis Manzella Design?
Pilchner-Schoustal Associates?
Sound Control Room?
Tom Hidley?

The only significant difference I knoe of consisitently between professional and home room acoustic design is that home rooms will have a greater significance on a listening area as opposed to a listening sweet spot.

The rest of belongs wiith people who think horizontally straight wires are important. (Ever try to watch a show with no
vertical?) Very Happy

Polarized speaker wires away;
Andre

(edit): Corrected html code

Posted: Wed Mar 30, 2005 7:37 pm

I had another thought, and it's less than an opinion and just a thought.
Here' goes.
a) we know that 1" of absorbtion isn't going to drop the sound by 20db in a single bounce. I think for 10dB we need 99.9% absorbtion and for 20dB we need 99.99% absorbtion which we don't have (% vs dB is probably wrong - I could probably work it out but I'm being lazy).
b) for a sense of spaciousness we need a few reflections (not mirror points, I mean it has to bounce completely around the room 30 times to build up a sound field)
c) a bunch of spaciousness in HT is provided by the surrounds
SO
what if the thinner material up front also contributes to the overall room sound, by allowing a few reflections over 1 whole second from the surrounds.
What if it's really a balanced approach to getting lots of things done in the sound field?

In other words, what if we don't want to kill the sound, but rather we just want to beat it down a bit each reflection.
Keep in mind that the entire room, taken as a whole, as an even RT60 -- so even if the front wall is absorbing more highs than lows, elsewhere in the room something else is absorbing more lows than highs. So this front wall isn't going to affect the frequency of the spacious sound.

AndrewSteel: 5.1 control room vs HT.
I agree, they're close enough that they're worth studying together, and anything written about one is worth reading about IMO even if one is doing the other. But some differences come to mind. So I'm merely nitpicking Smile

5.1 control room - one listener (one material chair absorbs highs but few sabins), small screen for syncronization with audio track (e.g. 14" monitor), circular placement of 5 speakers equadistant from listener, the HVAC has to be running for 8 hours, there's a THX standard room size for mixing movies in if one wants a THX certified DVD.

Home Theater - several listeners (often with a dozen unused yet absorbing leather covered seats -- leather reflects highs a bit acts as a membrane trap - lots of sabins due to large total surface area of seating for 12), asthetic treatments and placements and objects, large screen (my personal bias!), the HVAC has to be running for 2 hours, non-standard room dimensions.

Posted: Thu Mar 31, 2005 6:21 am

I agree with Big D.

If only it were that easy. I WISH I could treat HTs like control rooms! If I only had one seat to deal with, life would be MUCH easier. If I only had to deal with 2 channels, life would be much easier. If I didn't have to worry about that big reflective screen in the middle, not putting speakers in front of it, not getting them in sight lines of 2 rows of 4 people, etc....

I also agree about having even absorbtion at all frequencies IF that's what the room needs. I'll treat it so that the RT is even for all frequencies - not necessarily with the same amount of absorbtion at all frequencies with my treatments - 2 different things. As for people and overstuffed chairs, from all the numbers I've seen, they're not nearly as effective at absorbtion in the upper mids and highs as they are down lower.

Posted: Thu Mar 31, 2005 10:11 am

eric_desart wrote:

Paul,

I'm really sorry, but you make your believes as well truths.

Yours and Mark's control room is one type of room, not THE only possible room.

yse, of course Smile

Quote:

I have been invited to listen to speaker cables with blind tests, and they could recognize significant part of them.
I don't judge good, better or bad. I only know they did.

I have been involved in tests were speakers were set on top of decouplers to hear this possible phase shift (the thing you tell because you heard it from others).

Yup, 'others' was you Smile

Quote:

And I'm a dry NON-believer when I hear such stories.

I even thought people were crazy when they invited me to listen to cables. I thought I misunderstood their invitation.
I WAS there, and was VERY attentive that this blind test really was a blind test.

So while being not an expert at all, I am a critical bystander, almost more busy checking that they don't cheat me nor themselves.

Did they test straight cables against cables tied in a knot? Smile

Paul

Posted: Thu Mar 31, 2005 11:12 am

BobZ,

> I think for 10dB we need 99.9% absorbtion and for 20dB we need 99.99% absorbtion <

With 99.9 percent absorption (0.1 percent reflected) the reflection will be 60 dB softer than the original. If a surface absorbs 90 percent and reflects 10 percent the reflection will be 20 dB softer. In other words, every time you divide by ten the signal is reduced by 20 dB.

--Ethan

Posted: Thu Mar 31, 2005 11:15 am

Eric wrote:
I have been invited to listen to speaker cables with blind tests, and they could recognize significant part of them.

Hey Eric,
You know I consider you like a kind of intellectual dad Smile

But when you write this I react the same as you would when I write that I have hard proof about damping 100 dB of music with 1.2 inch of gipskartonplaat and some green glue or whatever.

Twisted Evil

Posted: Thu Mar 31, 2005 11:28 am

proudtower wrote:

Eric wrote:
I have been invited to listen to speaker cables with blind tests, and they could recognize significant part of them.

Hey Eric,
You know I consider you like a kind of intellectual dad Smile

But when you write this I react the same as you would when I write that I have hard proof about damping 100 dB of music with 1.2 inch of gipskartonplaat and some green glue or whatever.

Twisted Evil

hey, leave me out of these cable controversies. i've seen how ugly those can get...

hee hee

Posted: Thu Mar 31, 2005 2:48 pm

proudtower wrote:

But when you write this I react the same as you would when I write that I have hard proof about damping 100 dB of music with 1.2 inch of gipskartonplaat and some green glue or whatever.
Twisted Evil

I only report what I witnessed with my own eyes and ears, with a critical mind in function of the correctness and objective of the test which was specially organised by people WITH experience in order to check if described differences could be judged or not.
Those people, with highly qualified musicians and studio/recording experience organized this in a rather professional/serious manner, not to prove whatever, but to know.

And the manner they relate unknown cables, with quality and rating was not acoustics but statistical logic.

Whether one chooses to ignore or doubt my words is other one's choise. I'm not interested in Yes/No games.

While I'm more than aware of snobisme in this world, I have a rather critical mind. So whether those expensive prices are worth it or not, I refuse to judge or express an opinion since I'm not qualified to do so, in the same manner that I have no idea that the close to 20000 $ A PIECE speakers I listened to are worth their money or not.

Snobism exist in 2 directions. One can want the best as a BMW or one can want a 2PK resisting this consumers hype.

So I believe as well that people can have strong opinions without EVER have witnessed a comparative test as I described.

Posted: Thu Mar 31, 2005 3:07 pm

Eric, your testimony on this topic (cables) is, by far, the most interesting that i have ever encountered.

You ARE, as you say, not prone to bouts of fantasy.

there are speaks up to $150k/each (Wilson WAMM), and the last incarnation used (i believe) Bextrene (an archaic form of plastic not used in decades, but popular in the 70's for speaker cones) cone 6x9's dating back to the late 70's (a KEF design).

for $150k/each, i wonder if they come with a movie starlett's services?

Posted: Thu Mar 31, 2005 3:09 pm

and if you fellas can allow a wall junkie this intrusion into the already off-topic discussion:

do the nay-sayers about cables also suggest that all amps sound the same? after all, they measure identically, or so close to identically perfect that ...

well i've heard many-a-man claim they can't be all that different.

what say ye?

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