room treatment effectiveness

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 midrange...so 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.