Archived from groups: rec.audio.tech (More info?)

Hello,

I am in the process of acoustically treating my room and moving my
speakers around. Are there a series of test signals that would work to
help determine "imaging", "clarity", "soundstage", etc? I think it is
too fatiguing to try to listen to music to determine these factors,
since it is sometimes hard to tell what exactly I am listening for.

Archived from groups: rec.audio.tech (More info?)

Alan,

> Are there a series of test signals that would work to help determine
"imaging", "clarity", "soundstage", etc? <

No, though you can measure the effect of early reflections using room
analysis software such as ETF:

www.acoustisoft.com

Or just treat the first reflection points, which are easily calculated
and/or identified using a mirror.

> Bass trapping ... I might leave this area alone since I don't want to play
around with fiberglass <

In my experience bass trapping is what all rooms need most. Yes, an
inexperienced listener usually notices echoes and excess ambience first, but
those are easily treated with inexpensive "thin" absorption. Then the real
problems are revealed - one-note bass, boominess, lack of articulation,
muddy low end, etc.

> or pay a lot for low frequency absorption. <

How much did you pay for your Martin Logans? :-> )

It always amazes me that people will spend thousands of dollars on gear,
then cheap out on their room even though the room affects sound quality more
than anything else including speakers.

> Does their technique seem sound? <

I don't think so, but I admit I'm biased. Maybe you noticed they can't even
be bothered to provide data for their own products? How much absorption do
you think is possible from a diaper sized piece of cloth?

> use diffusion behind the speakers <

This is less useful in a room the size of yours. Especially with diffusors,
the cheap ones are ineffective and the good ones are very expensive. In your
case I suggest you focus on bass traps and first reflection control. That
will give you the most bang for the buck.

--Ethan

Archived from groups: rec.audio.tech (More info?)

Ethan Winer wrote:
> Alan,
>
>
>>Are there a series of test signals that would work to help determine
>
> "imaging", "clarity", "soundstage", etc? <
>
> No, though you can measure the effect of early reflections using room
> analysis software such as ETF:
>
> www.acoustisoft.com
>
> Or just treat the first reflection points, which are easily calculated
> and/or identified using a mirror.
>
>
>>Bass trapping ... I might leave this area alone since I don't want to play
>
> around with fiberglass <
>
> In my experience bass trapping is what all rooms need most. Yes, an
> inexperienced listener usually notices echoes and excess ambience first, but
> those are easily treated with inexpensive "thin" absorption. Then the real
> problems are revealed - one-note bass, boominess, lack of articulation,
> muddy low end, etc.
>
>
>>or pay a lot for low frequency absorption. <
>
>
> How much did you pay for your Martin Logans? :-> )

$900 used. Then I built my own amp ($100). Source is a DAC-in-a-box
from M-Audio ($70). So the total cost is about $1100. You can see why
I'm resistant to pay $800 for a set of bass traps.

I haven't measured the room yet, but I'm hoping the two big openings on
the side of the room will help smooth out the bass response.


>>Does their technique seem sound? <
>
>
> I don't think so, but I admit I'm biased. Maybe you noticed they can't even
> be bothered to provide data for their own products? How much absorption do
> you think is possible from a diaper sized piece of cloth?

>>use diffusion behind the speakers <
>
>
> This is less useful in a room the size of yours. Especially with diffusors,
> the cheap ones are ineffective and the good ones are very expensive. In your

Can you elaborate on which diffusors are "cheap" and why they are
ineffective? And which ones are good?

> case I suggest you focus on bass traps and first reflection control. That
> will give you the most bang for the buck.
>

For the first reflection control, should I focus solely on absorption,
or attempt to diffuse as well?

Thanks for the suggestions.

Archived from groups: rec.audio.tech (More info?)

On Wed, 28 Sep 2005 20:06:16 GMT, alan <no-longer-valid@yahoo.com>
wrote:

>$900 used. Then I built my own amp ($100). Source is a DAC-in-a-box
>from M-Audio ($70). So the total cost is about $1100. You can see why
>I'm resistant to pay $800 for a set of bass traps.

You can build them cheaply from compressed fiberglas (which doesn't
have all those loose fibers) or mineral wool.

Of course, first you need to measure.

Kal

Archived from groups: rec.audio.tech (More info?)

On Wed, 28 Sep 2005 09:45:49 -0400, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

>It always amazes me that people will spend thousands of dollars on gear,
>then cheap out on their room even though the room affects sound quality more
>than anything else including speakers.

Exactly. I built my own sound-absorbtive panels, using 2"-thick
compressed fiberglass (Johns-Mansville IS300). My panels total 120
square-feet, and are arranged to achieve something of a "live end/dead
end" room.

Made a HUGE difference in the sound, all for the better.

Archived from groups: rec.audio.tech (More info?)

Alan,

> $900 used. Then I built my own amp ($100) <

Well, okay, in that case you're forgiven. :-> )

> I'm hoping the two big openings on the side of the room will help smooth
out the bass response. <

Help, yes, but I'm sure you'll still benefit from bass traps.

> Can you elaborate on which diffusors are "cheap" and why they are
ineffective? And which ones are good? <

The cheap type I have in mind are made of thin stamped plastic or styrofoam.
The cheap ones I've heard sounded worse even than a bare wall. Good
diffusors are of necessity deep. For example, the QRD and Skyline diffusors
from RPG are excellent. But they're complex and expensive.

> For the first reflection control, should I focus solely on absorption, or
attempt to diffuse as well? <

How big is your room, and how far away are you from the reflection points?
Most smallish rooms benefit more from absorption than diffusion. Unless
you're 8 to 10 feet away from them, they won't do what you want. And most
rooms have too much ambience anyway. The point of diffusion is to avoid
reflections and blatant echoes but without making the room more dead
sounding. Most rooms are already too live sounding, which is why I usually
recommend absorption.

--Ethan

Archived from groups: rec.audio.tech (More info?)

Thanks again for the responses.

Ethan Winer wrote:

>
>>Can you elaborate on which diffusors are "cheap" and why they are
>> ineffective? And which ones are good? <
>
> The cheap type I have in mind are made of thin stamped plastic or styrofoam.

Would an example be the diffusors made by Auralex? According to some of
their data (polar plots), they are pretty reasonable about spreading
sound out, even at low frequencies. They seem to work on the principle
that a "beam" of sound hitting a convex surface spreads out. I don't
know if this principle is effectively different than the phase offsets
used by the other diffusors.

> The cheap ones I've heard sounded worse even than a bare wall.

Is that because they were improperly filled and thus had a hollow
resonant sound?

> Good
> diffusors are of necessity deep. For example, the QRD and Skyline diffusors
> from RPG are excellent. But they're complex and expensive.

Well, the BAD diffusors from RPG are not deep.

>
>>For the first reflection control, should I focus solely on absorption, or
> > attempt to diffuse as well? <
>
> How big is your room, and how far away are you from the reflection points?

The room is 12 x 14 or so, so I am only about 7' and 9' from the side
and front wall (behind the speakers) first reflection.

> Most smallish rooms benefit more from absorption than diffusion. Unless
> you're 8 to 10 feet away from them, they won't do what you want.

It seems that at higher frequencies, the sound has already "diffused by
now".

> And most
> rooms have too much ambience anyway. The point of diffusion is to avoid
> reflections and blatant echoes but without making the room more dead
> sounding. Most rooms are already too live sounding, which is why I usually
> recommend absorption.
>
> --Ethan
>
>