Need qualified room acoustician

[audioguy]

This thread should have been titled "Need qualified room acoustician to work for free."

I was not looking for free but I was looking for a "guarantee" that my "glare" problem would be resolved and no company would give me that. I was willing to spend the $6K to $10k (the two estimates I got) to get there but had no intention of spending that kind of money and being no better off than before I started.

And by just trying some different things, I have made huge progress and my out of pocket expenses have been SUBSTANTIALLY less than those numbers. Ethan's idea of absorption on the ceiling seems to have really tamed things down which was an idea given to me by GIK Acoustics (for which they were paid for by me purchasing additional room treatment products).

I have not measured it yet but I'm sure my RT60 is still way too low. Once I get the "glare" issue completely fixed, I can begin to add back more reflective and/or diffusive treatment to liven things up a bit.

 

[Nyal Mellor]

Audioguy, glad you are making progress! Of course like most things in audio, one can DIY a quite good approximation for state of the art, presuming one is willing to invest some time and effort into it.

 

[The Bogg]

180ms is a very dead room! Like Ethan said, putting some particleboard over the existing absorption on the ceiling, but not at mirror points, is probably the best way to proceed. You going to need quite a few boards to have an effect and try and spread them out a little rather than covering one area totally. You would be doing yourself a favor by getting REQ Wizard or XTZ Room Analyzer or Fuzzmeasure. Start by aiming for a single figure RT60 of 0.4s.

I have REW software. I'm not sure how I'll get the particleboard or whatever onto the ceiling since it's a finished ceiling with cloth on it. Perhaps I'll try the walls first (where there is absorption).

 

[The Bogg]

This thread should have been titled "Need qualified room acoustician to work for free."

Kind of a cheap shot and not entirely accurate. Chuck has answered for himself. From my point of view, I've already spent 5 figures with Rives and a few thousand on Adam Pelz. I'd happily part with a bit more money if someone would "guarantee" a solution but so far no-one has committed to that. Sure, it might be worth having Dennis and Adam work on Chuck's room for 6000 bucks but if it doesn't help then they'll just say "I told you it might not solve the issue". Absolute crap in my opinion.

I have a rectangular room, surely it can't be THAT hard to define a treatment plan that would lead to a "balanced" room. I can live with what I've got but since we have some bright guys on the forum here I thought it would be worthwhile to ask some questions, and I appreciate the responses. Chuck, I'm not trying to hijack your thread!

 

[audioguy]

Chuck, I'm not trying to hijack your thread!

You are not hijacking the thread. I appreciate your support.

It would seem to me that, in reference to another comment about expectations, that a contract for room design should commit to things like frequency response plus or minus; and RT60 at all frequencies between x and y; and bass ringing of no more than z, etc. I don't know if there is a list of metrics that would cover all bases but there should be some kind of measurable results.

I suspect it may be more complex than my simple idea but neither The Bog nor I and (according to Mark Seaton) lots of others have designed rooms they are actually totally satisfied with - even those that are designed by reasonably well respected designers !!

 

[Bruce B]

FWIW when I started searching for designers/acousticians, even for a ground-up build, I could not get any guarantees that it would be perfect. This is not an exact science and that's why I got 2 different people involved in our build. There are rules of thumb and calculations you can make to start the ground work and give you a fighting chance as far as acoustics go. One thing that was stressed continuously throughout the build was symmetry. No room is perfect, but no one will give you any guarantees either.

Good-luck!

 

[mep]

FWIW when I started searching for designers/acousticians, even for a ground-up build, I could not get any guarantees that it would be perfect. This is not an exact science and that's why I got 2 different people involved in our build. There are rules of thumb and calculations you can make to start the ground work and give you a fighting chance as far as acoustics go. One thing that was stressed continuously throughout the build was symmetry. No room is perfect, but no one will give you any guarantees either.

Good-luck!

Thank you Bruce for answering the question that I was going to ask-and that is does anyone give a guarantee? I didn't think they did because whether you like the results can be very subjective and the costs of ripping out and reinstalling are very expensive.

 

[microstrip]

Sometimes I feel that this the problem is like the egg and the hen, which of them came first?

Should you first build the listening room acoustics or buy first the whole reproduction system, speakers included, and built a room for it?

I have owned two very different speakers (Krell LAT1000 and SoundLab A1 PX) and their requirements for room sound treatments were quite different. As I use mainly RPG modular elements - Diffractals , FlutterFree and Abbfusors I was able to change their positions when I swapped the spealers. Otherwise, I would prefer the sound of the room without acoustic treatment.

 

[Bruce B]

Should you first build the listening room acoustics or buy first the whole reproduction system, speakers included, and built a room for it?

Well some room designs definitely limit your choices of equipment/speakers. Ours for example, the whole front wall is a bass trap. We can not have any dipole/bipole speakers in here because it sucks the life right out of them. Our designers did ask what type of speakers we will be using though.

 

[Ethan Winer]

This is not an exact science and that's why I got 2 different people involved in our build ... No room is perfect, but no one will give you any guarantees either ... Our designers did ask what type of speakers we will be using

That's a great point Bruce. Room acoustics is not unlike medicine, where the exact same treatment that worked in one room doesn't work the same in another. Even when rooms have identical dimensions, if the wall, floor, and ceiling materials are not identical too, the result will be different. As you also pointed out, which loudspeakers are used has a huge impact too. Add a sub into the equation and it's even more difficult to promise a specific result.

As an OT aside, a few months ago I went to a dermatologist to have a small wart removed. She said she'd freeze it with liquid nitrogen, and promised me it will fall off in a few days. Well, it did fall off, but part remained. That 4 minutes in her office cost me a $45 co-pay! So I called and asked if I could get a follow-up freeze for no additional charge. Guess what I was told?

--Ethan

 

[Jeff Hedback]

Maybe I'm just a softy, but I recently assisted a client in Germany (a recording/mix/post suite) who had hired a designer and was left with a horrible result. I offered an agreement, once I had a good understanding of his factors, of 50% to engage the process and 50% on success (and we defined what the exact acoustical goals were).

Guarantees are tough to offer, but real expectations aren't. I always want to feel that the "trust exchange" is an equal relationship between myself and my clients.

As for markers, some of this is relative to the background noise level. If the room is has low noise floor, NC25 or lower, I feel that a lower RT60 like the .2s mentioned can feel very comfortable providing you have "preserved" upper mid/hi energy (through strategic use of reflections and diffusion). If the room has a more typical background noise level, I agree with Nyal that .4s is right on target.
- LF resonances above 30Hz should not exceed 400ms (300ms preferred)
- Early reflections should be down 15dB from direct arrival for as long as possible (10ms absolutely minimum) to allow the source content to reach the listener without coloration.

Room shape/dimensions, construction systems, HVAC, speaker type/location, listener location, room finishes (which include absorption, diffusion and reflection) are ALL part of the acoustical factors that should evaluated to reach a desired response.

 

[DaveyF]

Not sure if anybody has bought this to your attention audioguy, but it seems to me that you have two areas of glare in your room....1) the very large screen between your speakers, which although you say you cover this, is possibly still a factor and 2) your wooden floors that are beneath the speakers.
One thought that occurs to me is that your room is treated well enough that even a small amount of glare, from example the floors, will be very obvious. BTW, your gear could be introducing some brightness into the sound...what are you using as a front end now?

 

[audioguy]

Not sure if anybody has bought this to your attention audioguy, but it seems to me that you have two areas of glare in your room....1) the very large screen between your speakers, which although you say you cover this, is possibly still a factor and 2) your wooden floors that are beneath the speakers.
One thought that occurs to me is that your room is treated well enough that even a small amount of glare, from example the floors, will be very obvious. BTW, your gear could be introducing some brightness into the sound...what are you using as a front end now?

I tried temporary fixes for both of those and neither helped. I covered the entire floor area with about 4 inches of 703 and it did nothing. I also covered the entire screen area with 2 inch 703 and it did nothing.

At this point, I am focusing on some other portions of the ceiling and rear wall. In a week or so when I have some time, I am going to temporarily put some old 2 inch acoustic panels and cover them with addtional 2 inch 703 right behind the listening position (which is probably 8 feet from the rear wall) and see if that does anything. So about an 8 foot wide x 4 foot tall area will basically sonically separate me from the rear wall (at least for those frequencies I am dealing with) and that should tell me if the rear wall is playing any sort of role in this glare issue. AS noted previously, the ceiling "cloud" I hung has fixed the null problem and greatly reduced the "glare".

Going back to my questions about guarantees, I understand that no one wants to provide that. But if the purchaser and acoustical engineer could agree on some measurable quantities (RT60, etc) , that would at least get both partied aligned. But in any agreement, I would expect the designer to address any obvious issues (like my glare problem) after the room was completed. And that requirment would eliiminate the "remote design" options that Rives provides OR, have a clause that at some fixed additional price, the designer would visit the site and fix the problem. As stated multiple times, my issue with Rives was/is his refusal to admit the room played any role in the problem.

 

[keithyates]

If the room is has low noise floor, NC25 or lower, I feel that a lower RT60 like the .2s mentioned can feel very comfortable providing you have "preserved" upper mid/hi energy (through strategic use of reflections and diffusion). If the room has a more typical background noise level, I agree with Nyal that .4s is right on target.

Agree that low background noise is relevant, even critical. But NC25? Is that a typo? We consider NC15 borderline acceptable for dedicated playback spaces. Our typical spec is NC10, with ambitious facilities spec'd at NC5. These are with the HVAC system operating at the design flow-rate (CFM or air changes/hr) which for our venues amounts to 2-3 x "standard" flow-rates in residences in the US.

Room shape/dimensions, construction systems, HVAC, speaker type/location, listener location, room finishes (which include absorption, diffusion and reflection) are ALL part of the acoustical factors that should evaluated to reach a desired response.

Amen!

 

[Jeff Hedback]

Hello Keith,

I have a tremendous appreciation for your work! My dear friend Remi works for you (at least as of the last time we spoke).

The NC25 was not a type-O nor an endorsement of that being the target for an optimized situation. In fact I almost stated NC30. My point is that beyond just the room volume, the noise level should be part of the discovery process when establishing a decay time target (and not to get way off topic, but T30 would make a lot more sense to use than RT60 in typical residential size spaces). In a conversation with Nyal, he in fact wondered if NC25 is too unrealistic to even state as a target (as NC40 is reality of most existing spaces) and I don't fully disagree. The overall point would have to go back to the goals and expectations of the client.

I fully agree that NC10 and the eighth wonder of the world- NC5 have real benefits to the experience. ...just not possible or practical in most budgets (at least with my clients).

I look forward to your knowledge and experience here at WBF.

 

[Bruce B]

Typically I don't think you could get a NC15 or below without having to build a room within a room and with strict adherence to details. We told our contractor to pretend they were building an aquarium or submarine. If air got in/out, sound could too.

 

[keithyates]

Yes, a room within a room is almost always required to get to NC-10 or below. Up at NC15, if the listening room or theater is in the basement, well away from HVAC equipment, footfalls from above, etc., the room-within-a-room requirement can sometimes be eased to just carefully and resiliently attaching the interior envelope to the existing structure (via RSICs, Isomax, good ol' RC-1, etc.). Such rooms also need a dedicated, noise-engineered HVAC system. Also costs $$$ for a special-purpose measurement mic that'll give you clean data down to NC5 and NC10. (IMO, if you can't DESIGN a room and mechanical system to hit, say, NC10, and then VERIFY that it hit the spec, you have no business SPEC'ing anything below NC20.

All this noise management costs dough. That's not the shame or pity of it. IMO, the shame and pity are when music & movie lovers shell out $$$ for stuff that doesn't actually increase the probability they'll get goosebumps when they turn the lights out and hit Play. Pushing the noise level down, way down, does.

 

[Bruce B]

This is what is needed for a NC10

 

[vinylphilemag]

This is what is needed for a NC10

Quick question: Is NC10 more quiet than NC20, or less? (My impression is that the lower the NC number, the more quiet--or better, the more acoustically insulated--a room is.)

 

[Bruce B]

Quick question: Is NC10 more quiet than NC20, or less? (My impression is that the lower the NC number, the more quiet--or better, the more acoustically insulated--a room is.)

That is correct. The lower the number, the quieter the background.