Results from acoustically treated room

[Vaughan Odendaa]

Hi there,

A client of mine just had his room acoustically treated with Auralex treatments (I won't name the company who built his room or did the acoustic modeling and measurements) but the results are not great.

I went to my clients home a few days back and he has well above entry level equipment. All THX Ultra 2 certified. His room size is small. Around 1500 cubic foot sealed.

All speakers are hidden from view. A substantial amount of bass trapping was utilized, supposedly. Diffusion was also used on the ceiling. This is not a run-of-the-mill cinema. It's supposed to be excellent from an acoustics perspective.

My listening tests do not mirror this. My listening results were based with THX processing turned off. As soon as I fired the system up, I popped in Lord of the Rings, FOTR. The first thing I noticed was that there was a substantial drop in high frequency energy in the room.

I first thought that perhaps the treble controls were set too low (as opposed to neutral) and this was not the case. Dialog sounds weird. It sounds muffled but the high frequency components do not come out clearly. Those energetic moments that have kick do not seem dynamic at all.

And no, DRC was turned off (both in AVR and in the DVD player). THX standardized settings, 80 hz crossover, small settings for each main speaker. I tried different chapters in LOTR and each time I was just left there wondering what how a "well treated" room could sound so horribly bad.

I mean, I have nice equipment myself (in my humble opinion) and my system sounds far far better. In every aspect. Dialog clarity is better, high frequencies are not jarring or have excessive sibilance and my room is not acoustically treated.

Bass is a different story. There was no apparent boom whatsoever. At all. The bass levels were calibrated to 72 to 73 dB's and all the big moments were extremely impressive. I could feel the bass unlike I've heard before even with scenes that I never thought would have that much sonic impact.

So I'm assuming the bass trapping had something to do with this. What I did find strange was that when there was a bass heavy scene and I paused the action, the whole room seemed to reverberate for about half second.

Almost as if there was a delay of some sort. I'll say it again, the bass quality itself was fantastic. No apparent boom and this was impressive. So I'm wondering if the treble issues are perhaps in part due to the material that is being used to cover the speakers ?

I have no idea. But if it did affect the sound of the speakers, how could the guys put it in without measuring the effects before hand ? Doesn't sound right to me. Lastly, Clapping my hands at ear level height also revealed flutter echo. A metallic sounding ring. Funny because the room itself is treated with a lot of absorption.

The exact details on the absorption and diffusion is not known (by me) but I'm told that all early reflection points were covered.

Acoustic experts, what are your thoughts on this ?

--Regards,

 

[Glenn Kuras]

Without seeing a diagram, pictures and or a test graph of the room then it is impossible to REALLY comment..

Any way you can test the room and post the graphs? Also post a layout of system and acoustics in the room?

Glenn

 

[Vaughan Odendaa]

Hello Glenn,

My client has a Jamo D6 6.1 THX speaker system. An Onkyo 805 AV receiver and an Onkyo 504 dvd player. It will be a bit difficult for me to ascertain the amount of absorption and diffusion present.

Also, the lights were not working 100 % so it wasn't as bright as I would have liked it. When you mean test the room, what kind of measurements are you implying ? RT60 ? Modal ringing decay ?

Unfortunately I don't have a laptop at present to do the testing but I do have an SMS-1 real time analyser that I could use to evaluate the peaks and nulls in the frequency response.

The high frequency response seems off in my opinion. I don't think it has anything to do with accuracy either. I have a demo room that is overdamped and still sounds much better. Same equipment too but the speakers are not hidden behind paneling.

--Regards,

 

[bpape]

Sounds to me like a combination of issues:

- Potentially poor choice of cloth for in front of speakers impacting HF response.
- Generally too much mid/high frequency absorbtion in the room without enough EFFECTIVE absorbtion down below 60Hz in the subwoofer range. This is very typical of foam installations.

I'll agree with Glenn that without knowing more specifics of the installation, it's pure speculation. If measurements could be taken that would allow us to look at not only frequency response - but also impulse response and the waterfall charts of the decay time - that would shot it pretty clearly most likely.

Bryan

 

[Vaughan Odendaa]

More bass trapping was employed recently in the room in the two front corners. The traps used are the Lenards. I'm not sure how effective the foam traps are.

But what I know so far is that bass trapping in each vertical corner has been utilized. Like I said the bass itself is clean and free of apparent boom which is great. But it sounds as if the treble has been reduced by 6-8 dB's.

My own demo room at work has almost 100 % of the room covered with absorption material. There is zero bass trapping whatsoever. Just mid to high frequency absorption. And even then, it doesn't sound nearly as bad. The treble still has some bite. Not so in my clients room.

It sounds like mud. It sounds really muffled. Sometimes the dialog even booms a little bit. It stresses my ears a little bit. And I know that that is a bass problem. Which is strange given all the bass trapping that is used. I'm assuming that the traps used are at least effective to 80 hz (at a minimum).

I could be wrong though. I agree with you bpape that measurements need to be done to ascertain the nature of the problem. The guys who built the room and installed the acoustical treatement promised me hard data as well.

So I can expect measurements on the room soon. Until then I won't be able to give you any more information.

Sorry.

--Regards,