room treatment effectiveness

Before I spend money on room treatment, I would like to hear of positve/negative experiences and whether the results are objectively measurable or merely subjective.

My local dealer had a sound room (now a storage room) with a pronounced 100hz boom and he said they installed 16 inch tube traps from floor to ceiling in each corner and the measured difference was only .5db which isn't much. I don't want to go down this road.

I have looked at GIK acoustic and their products are reasonable priced. I have read some favorable comments on their products. I'm sure there is a limit on what can be done with add on products. Are they all good for a few tenths of a db or can one expect to correct for 5 or 6 db?
Often the only way to decide after making a 'best solution' decision, is to try it. Find a dealer that will give you a return without stocking deal, or better yet maybe a loaner, that will take the stress out of the decision to move ahead.
In my opinion it strongly depends on what you are trying to accomplish and the problems that exist before beginning. My expience for best results is in addressing a very lively room with excessive echo/reverberation. This can be done with both application specific sound treatments, but frequently can be performed just effectively with some careful and tasteful decorating.

You comment specifically on a pronounced boom at a very specific frequency and report that their single solution only affected the "boom" by 0.5 db. What was the measuring of the "boom" to begin with? What other approaches did they pursue - speaker placement, listening position, toe in, etc. . . To me, it is not the end of the world having a slight excess at certain frequencies as achieving a perfectly dead flat room across the frequency range is near impossible/difficult and liveable at the same time.
I agree with Tiger but with a little twist. What exactly is it that you want to change? You wouldn't have asked the question if you didn't have an issue or two. Is it a bass issue or sound stage? Please provide more information because there are some relatively easy and inexpensive DIY treatments you can do on your own...all you have to do is purchase them and if they don't work, just return them.
My new speakers (ESP Boshran SE) produce an energy excess of 11 db at 200 hz in my room. The only placement that lowers this figure is with the speaker 8 inches from the wall and then there is no sound stage. The speakers are a sealed box design with two mids, two tweeters, and two bass drivers per speaker plus they are taller and wider than my B&W's.

I borrowed a Rives PARC and used a 7db cut at 195hz with a 3.8Q that worked well. If I can do the same thing with room treatment or make an appreciable improvement I would rather do that. Otherwise, I need to buy a PARC or bail on the speakers.

My old speakers which I set back up over the weekend are B&W N802's and they don't exhibit any response peaks like the ESP's. It is obvious from listening that the two different speaker's power response into the room is very different.

Would room treatment be beneficial for the B&W's if they stay? They certainly would not benefit from a PARC. I am contemplating my next move.
Do a drawing of your room with dimensions, furniture placement, etc and post this question on the Room Acoustics forum sponsored by Rives Audio. They will answer just about any question and are extremely helpful.

You really need to apply a methodical approach to treatment, otherwise you are simply shooting blind and and results, good or bad, will likely resemble that.

BTW, have you measured response with your listening position moved forward or backwards a few inches to a foot or so?
My new speakers (ESP Boshran SE) produce an energy excess of 11 db at 200 hz in my room. The only placement that lowers this figure is with the speaker 8 inches from the wall and then there is no sound stage

This is typical of quarter wave cancellation.

The fact that placing your speakers up against the wall fixed it tends to confirm this (according to the article).

Another alternative - if you don't like the soundstage from very close to the wall placement - is to go far away from the wall or at least 6 to 8 feet.

Broadband absorption from acoustic treatment will ameliorate these problems at specific frequencies but it won't fix them (a few db). If you have a small square room 8 foot by 8 foot by 8 foot then turning it into a storage space might be the only option....

What the salesman neglected to mention was that the broadband absorption fixes all kinds of nulls throughout the mid/bass and it makes lots of small improvements that can add up to a significant audible improvement.

IMHO a PARC is best for fixing things 120 Hz and below...and thick broadband acoustic absorption is best for 100 Hz and up.

At 200 Hz the wavelength is around 5 feet - trough to peak - so basically you can forget about fixing room modes with a PARC at these frequencies as what works at one position may be ineffective or make things worse a mere 2 feet away...
I agree with most of what Shadome said except the last statement. It turns out when you are dealing with modal characteristic it affects it everywhere except the null points, which you don't care about anyway. While you correct for a particular location it has a positive effect just about everywhere--though the most positive effect is at the point where it's measured.

The issue you described with the bass traps only lowering the bump 0.5 db is no surprise. This is basically lack of knowledge on how to use the bass traps properly and tune to the specific frequency. Shadome brings up the 1/4 wavelength cancellation principle. When you use the theory applied to traps--absorptive ones you realize the traps have to be signficantly out in the room to affect that frequency and you need a large trap. There are more effective traps for specific frequency. The NEW RPG modex traps are very effective. For broadband there are ways of building traps extremely effective.

The other aspect you bring up, which is a very good one, is how do you know what to buy. It's not easy and the other caveate is if 2 absorption panels are good, that doesn't mean 6 more will be better. This is why we provide the services we do. Our fees typically save the clients money on not buying unneeded acoustical treatment, or often saving a lot of money for clients that will build their own devices based on our designs.
The room is 14W x 14.75L with a vaulted ceiling that is 8' on the left to 11.6' on the right wall. The right wall is 7" tall with a soffit that sticks out into the room about 2' and then up for another 1.5' for a total height of 8.5'. Then the upper portion of the wall is open into an adjacent 10W x 25L room.

I tried moving the seating position out by a couple of feet and that made things worse. It seems like the 200 hz note is loudest centered between the speakers and several feet out from my listening position which is close to the wall. The corners of the room are less affected. I don't like the speakers in my face and having them positioned 8' into the room just won't work for me.

It's odd that one speaker has such a pronounced peak and the other does not even when placed relatively the same in the room.
It turns out when you are dealing with modal characteristic it affects it everywhere except the null points, which you don't care about anyway.

Thanks for correction. It illustrates your point about your services and their value.
I went the DIY route and I am very satisfied. I used Jon Risch's recipes on his site. The biggest improvement was in imaging and it was huge. I also treated my cathedral ceiling and that was huge. I have 7- 18" diameter 4' tall bass traps in corners and 4- 4' X 2' X 4" thick along the ceiling apex. My investment in time was around 10 hours and the money was less than $250. DIY doesn't take many tools, is not that difficult and has the rewarding factor plunking down the credit card does not. You comment regarding measurement differences a good bit. Since most people don't have the capability to properly measure before and after I'm not sure that's as important in the same way comparing specs of two $10K digital platforms means as much as the potential buyers choosing between the two by ear. If you are going to buy pre-made I too recommend using the Rives forum on AA to get opinions from those in the know like Ethan and David. Good luck!

I'm in the same position you are. I need to address some specific bass loading issues and I have been considering treating my room with bass traps. However, my audio dealer friend (whom I have great respect for) has informed me that, unless the traps are EXTREMELY large, they will have no effect on the lowest frequencies, which are, in my case, the frequencies that are causing the problem. The size of my room will not permit me to install very large traps (I'm talking about several feet or more in thickness) and traditional sized "bass" traps will only have an effect on the frequencies that are not an issue (the "upper-lower" frequencies). In layman terms, if I have a low frequency problem, I certainly don’t want to leave the low frequencies and reduce/tame the middle frequencies… This is disappointing to me, because I was all ready to order materials to build some DIY traps. If you haven’t already done so, you should test your room to find the specific “problem frequencies.” You may be able to solve your problems with broadband absorbers and traditional bass traps. However, it is the low frequencies that present the biggest problems. Make sure you know what frequencies the traps you plan to use will truly impact.

If anyone has read this far in my ramblings, I would like to take liberty with Rhljazz’s thread and inquire about room correction devices. I have searched these forums and I believe the consensus is that any equalization is undesirable. What about a custom devise specifically designed to filter the known problem frequency/frequencies? I think I know the answer, but just how, and to what extend do such a filtering device degrade the Sonics?? This may be beneficial to you too Rhljazz.

2chnlben, I did use a Rives PARC for a week and it did take the majority of my 200hz peak out and improve the sound. The room in general does not promote clarity and has a minor bump at 40hz and 80hz with suckouts at 50 and 60hz. I think I need to improve the room as much as possible and then go with the electronics.

My local dealer is going to build me a notch filter centered at the 195hz I really need. They, (AZ HiFi) already market a notch filter but it does not go high enough to fix my problem but it might be a solution for you. If that doesn't work out, I'll probably buy a PARC unless my room treament is really successful.

I've contacted the dealer that sold me the speakers and also sent in information to GIK Acoustics to see what they might recommend for room treatment.

However, my audio dealer friend (whom I have great respect for) has informed me that, unless the traps are EXTREMELY large, they will have no effect on the lowest frequencies, which are, in my case, the frequencies that are causing the problem.
Exactly what frequency range are you having trouble with?

ASC tube traps(.pdf) offer full wave bandwidth absorption down to:
9” 110Hz
11” 90Hz
13” 70Hz
16” 55Hz
20” 30Hz

Their fractional tube traps(1/4 & 1/2) take up even less room and can provide full bandwidth absorption down to 55Hz. The quarter rounds are perfect for corners.
Until my friend measures the room this weekend, I won't know the exact range(s). We both believe that the problem is near the 30-36Hz range. I did not have the same problem with my previous speakers that only went to 38Hz. My current speakers go below that down to 28Hz. I believe what my friend has tried to explain to me is that although a given product/material may be rated at absorbing a specific lower range of frequencies (i.e.: the 20" ASC Tube Trap), in order to effectively treat a given room, one would need specific quantities of that given material/product, and according to my friend, I would need more of that particular material/product than would fit reasonably into my room.

2chnben: You understand the problem well. Not only does the size increase as the frequency decreases and I do not agree with the diameters that the ASC describe--they need to be significantly larger. But the size increase AND the efficiency decreases. As the frequency gets lower, the problem gets tougher. Now 200 Hz is not that tough--that can be dealt with passively in most (not all) situations, unless there are some other serious restrictions (like no corners or space to work in). Usually the really problematic issues are 100 hz and lower.
I am fairly late in responding to this thread but here goes.

Before I spend money on room treatment, I would like to hear of positve/negative experiences and whether the results are objectively measurable or merely subjective.

We often hear that the room constitutes to about 50% to the sound apart from the equipment and speakers, and I totally agree with this statement. I've recently made a huge discovery in moving 4 pieces of RPG omnifussors to the front wall(behind the speakers). They were previously at the rear wall. Since I have a projector screen at the front wall, I can only squeeze in the diffusor panels at the side of the screen just behind the speakers. To my surprise, the sound suddenly takes on a realism so startling it's amazing. The struck of cymbals and percussion sound so real it's spooky. The sound is like coming from the side walls rather than from the speakers. Also, the highs are suddenly less piercing and it's wonderful to be able to crank up the volume higher without feeling any discomfort or strain on the ears. The differences are noticeable and you don't need "golden" ears to hear them. I don't need to strain my ears to perceive the differences unlike with cables and tweaks. My gut feeling tells me I will obtain greater improvements if I were to place another 2 pieces of omnifussors at the middle of the front wall. Unfortunately I can't do that since they will block the projector screen.

I have experimented quite a lot in my dedicated room and I now have absorption panels at both side and rear walls with some diffusion at the front wall. I have taken a look at your room and you do have a great system based around the N802. I guess placing treatments at the front portion(behind the speakers) is out since it's the doorway. In that sense I suppose you may be compromised at what you can achieve to improve your room acoustics. But one thing is for sure, room treatments have made a positive impact in my system as it would to any system. The question that remains is what treatment to get. From the way I see it, there are only two ways you can go about it which is either to buy and experiment yourself, or hire Rives services. :)

Now I need to figure out what to do next with the ceiling .........
For the listening room there is one rule: It should have good acoustic properties from the very beginning so you could optimize it with acoustic devices. If the room is bad, then you are in big trouble. There is no acoustic device that can turn your room into a good sounding one. Of course you can improve it somewhat but you'll need physically LARGE devices to overcome the problems, especially bass related problems.

I agree with Dazzdax to some extent, however, if you are fortunate enough to have the flexibility and options to rearrange your speakers and listening positions (which I don't), then you can reduce, or even eliminate many of the room issue - see this - I've used this method in every location I've ever lived with great results.

If, like me, your current room restrictions limit your ability to "tune" the room, then there is the option of utilizing parametric EQ. Like everyone else reading this, I too cringed at the thought of "degrading" the signal path. However, if the issue is low frequency standing waves, you have to ask yourself whether or not the compromise justifies the end results. To me, the bloated undefined bass is not a condition I can tolerate. I will try a single or 2-band customized filter, which is something you, Rhljazz, may need to consider depending on your success with absorption treatments. Do try the "Iron chef Speaker Setup" approach.

Good luc