[jtwrace]

As the tittle asks. 

I come from a world of data but at the same time there are times that you just can't prove or disprove something but we know in theory it's better and I need to go off of life experience. 

My example:
If I place more absorbers in my room and can't see a change in the measurements does this mean I will NOT hear a difference? 

Of course let's say that the instruments being used have a high enough resolution.

I would like some professional acoustic advice as to what you and your company do.

[Ethan Winer]

If I place more absorbers in my room and can't see a change in the measurements does this mean I will NOT hear a difference? Of course let's say that the instruments being used have a high enough resolution.

If you add absorbers to a room you will surely measure and hear a difference. This assumes a "real" measuring system such as Room EQ Wizard, and also assumes the amount added is significant. That is, if you already have 100 square feet of absorbing surface, adding only 1 square foot more may not be measured or heard. Then again, it also depends on where you add it. If you have a bunch of bass traps but no absorbers at the side-wall or ceiling reflection points, adding even small absorbers there will be noticed. But the key point is that anything audible can be measured, if not vice versa.

I would like some professional acoustic advice as to what you and your company do.

See this: The Acoustic Treatment Experts

--Ethan

[bpape]

I would agree with Ethan in terms of how much you're doing compared to what you already have as well as where you place it.

If you, for instance, put a diffuser at the ceiling reflection points, you're not going to measure any difference in frequency response or decay time but you'll hear the results.  Where you would see the difference would be in the impulse response - but even then it may still be swamped by other things with times approximately the same.

Bryan

[Ethan Winer]

Bryan, why would a change in impulse response not also show as a change in frequency response? I've measured reflections off a diffusor from a few feet in front, and it's always different from a bare reflecting surface the same distance away. Now, if you said the change measured might not seem to agree with the change heard, I could agree with that. I've scratched my head over that a few times myself!

--Ethan

[Bjorn]

My experience is that you often don't see much of a difference in the FRS using porous material. But you will see the difference looking at the ETC, and also at the decay if you use a good amount.

[Nyal Mellor]

Bryan, why would a change in impulse response not also show as a change in frequency response? I've measured reflections off a diffusor from a few feet in front, and it's always different from a bare reflecting surface the same distance away. Now, if you said the change measured might not seem to agree with the change heard, I could agree with that. I've scratched my head over that a few times myself!

--Ethan

It should always show a change but the change may be very small e.g. on the order of 1-3 dB. It depends where you are measuring in the room, in particular distance from speakers and distance from the boundary you have treated.

[jtwrace]

If you, for instance, put a diffuser at the ceiling reflection points, you're not going to measure any difference in frequency response or decay time but you'll hear the results.  Where you would see the difference would be in the impulse response - but even then it may still be swamped by other things with times approximately the same.

Bryan

Should I go diffusion or absorbtion in your opinion?

[NekoAudio]

I prefer absorption over diffusion in general. But it really depends what your goals are. Absorption will tend to bring you closer to the ideal, but it may narrow your soundstage or make things sound deader than you prefer.

[srlaudio]

So I suppose we should all strive to make our listening rooms as close as possible to an anechoic chamber?  I think not, the standard back in the 70's was to make control rooms as dead as possible, that proved to be not the best, and diffusion of one sort or another as been put in ever since.  Always remember, the best test of a room and system in the low range is a 30 hz test tone at 0 level.  After you get your amplifier and speakers up to the task, then you attack all the buzzing things in the room, such as loose small objects and various pictures (or acoustic treatments) hung on the wall with picture hanging wire.  Solidity is a must, unless you want your room singing along with the audio system.

[bpape]

Should I go diffusion or absorbtion in your opinion?

Either can work depending on what you're trying to accomplish and what the off axis response of the speaker looks like.

Bryan

[jtwrace]

Either can work depending on what you're trying to accomplish and what the off axis response of the speaker looks like.

Bryan

Well, I can't find the reflection that is in my data so I don't know.  I just want to kill that refelection. 

[NekoAudio]

Well, I can't find the reflection that is in my data so I don't know.  I just want to kill that refelection.

Have you addressed your first reflection points? That's a good place to start.

[jtwrace]

Have you addressed your first reflection points? That's a good place to start.

As I said, nothing is making a difference.

[JohnR]

Are you referring to the peaks at 5, 7, and 17 ms in this plot?

[jtwrace]

yes

[DougSmith]

Those kind of early reflections are generally caused by nearby surfaces or things like coffee tables. Just think about it in terms of approximately 1 foot per millisecond for the path length of the reflected sound compared to the direct sound.  You can try placing absorbers in various locations, or try moving the mic to see how the delays change.  Then you can figure out where they are coming from.

- Doug

[JohnR]

I was wondering if perhaps it would be worth moving the speaker and see if the reflections move. E.g. move one foot further away from the side wall - does one move by ~ 2 ms? Move one foot closer - does one move ~ 3 ms? Elevate it a foot off the floor...

I haven't tried anything like that myself but I'm happy to think up things for you to do 

[richidoo]

jtwrace, your FR looks awesome. You have accomplished a lot already. 

The 7mS impulse is a 3.5 foot round trip detour from the direct sound's path, and is coincidentally the typical tweeter height above the floor. Try laying absorber panels on the floor reflection point. Carpets don't absorb it all.

An absorber placed right close to the front of the speaker on the side or above will cast a sound shadow on the wall it is blocking, making finding the reflection point easier because you can shadow a whole wall at once.

The quick damping impulses are higher frequency >1kHz, so check distances to boundaries from the tweet/mid - to front wall or side walls, or mic distance to rear wall.  The 5mS reflection happens only 2.5 feet from the direct path - maybe a coffee table, or a wall close to your test mic? Leather listening chair?  Good luck