room treatment effectiveness

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.

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.

In a digital based system,the Z-Systems might do the trick:RDQ/RDP.