Can you correct nulls with acoustic treatments.

BTW: 128+64 = 192 HZ may also be another problem null area with speakers at 53" from rear wall...of course given other room modes/rear wall effects you may not clearly see every one of these dips, as the rear wall quarter wave cancellation effect, as seen by your microphone/SPL meter, is already combined with lots of other reverberant effects in the room.

Disclaimer: Fixing rear wall quarter wavelength may then lead you to see other problems more distinctly. So it is no cure all. For example it won't eliminate the problem of very bad room dimensions or lack of absorptive surfaces/furnture and acoustic treatment. In my experience it improves imaging and clarity in the lower midrange but does nothing for what are often huge room modal bumps below 60 HZ.

Acoustat6,
I have read through the Real Traps site and a lot of Ethan Winer's posts on AA. Learning a lot.

Thanks,
Jim S.

Shadorne,

Thanks for your input again. I have read your suggested links and am trying to assimilate the info. I would like to make a couple of smart changes and not a couple of hundred dumb ones. But, to be honest, I am something of a slow study.

As I see it, I have a room mode boost peaking at around 75hz., and a set of cancelation nulls peaking at 127hz and 250hz., with a few anomalies thrown in to confuse the uninitiated (me). Makes me wish I hadn't cut most of Senior year in High school.

It fits what you have described. I keep trying to figure out how the angled walls off to the sides of the speakers fit in. Maybe they really don't change the equations!

If the analysis is that straight forward, surely there is some corollary that dictates the solution is going to be complex!!!!!

I have unknowingly played with positioning that would significantly change quarter wave cancelation when I first got the 1.6's, 6 yrs. ago, and was trying to optimize bass output. At the time I didn't like it, but now I am wondering if it wasn't reinforcing the bass (or more accurately covering up for lack of bass) of the Maggies with a room mode and cancelations.

Anyway, more food for thought. THANKS for the info and analysis. I will try to post meaningful information and conclusions as things go forward.

P.S. I can mount the 1.6's into the wall behind them (soffet mounting taken to the extreme). It opens into a laundry room. Might try that someday.

Best Regards,
Jim S.

OK, this is not supposed to work with Magnepans but you have to follow the trail and see where it leads, if that makes sense.

I try what is written in the Genelec sites, that Shadorne has lead me to, about positioning to avoid 1/4 wave cancelations. According to everything written (their manual and everywhere else I have read) about positioning Maggies, they should be as far out from the back wall as possible.

Well shoot.... I do the calculations on the site, follow their recommendation to keep back wall distance 1 meter or less, and figure I am trading one set of cancelations for another. Low and behold, I move the speakers back from 50 some odd inches to about 30" from the back wall and play Patti Smith's Gung Ho, (not exactly an Audiophile recording but what the hey). OMG, the bass is up a notch and very clear! I mean, it is not subtle.

Ok, so I measure with my limited means and where I thought I would have traded an 60 or 90hz. null for a 110hz. null. the 60 was still there, the 90 wasn't as deep and the broad 100hz. to 160 hz. deep null was just gone. Replaced by a slight bump.

Ok, what is going on? I do the calculations for a 1/2 wave and it should be close to the 1/4 wave but instead there is a null at 230-240hz. Back to reading!

Anyway, what shouldn't work with Maggies does. At least in my room.

In all fairness it does generate some other issues. The tweeters are now close enough to the back wall and directionally pointed at the listening position to beam. Also brings into play reflections from a patio door behind and to the left of the LP that wasn't a concern before. Lessened those effects by tilting the speakers back a little.

FWIW,
Jim S.

Jim,

The Maggies should still respond to the same physics in the bass as Genelec describes, however, they radiate front and back in ALL frequencies (not just the LF below 500 Hz) and, therefore it will be recommended to have them as far out as possible - say in the middle of the room. (Soffit mount is not an option and will kill that beautiful atmospheric/ambient sound from the higher frequencies going in all directions). I have not owned these kind of speakers, however, the best demo I have heard was with these type speakers towards the middle of the room.