speaker/room bass modes

place them in pretty much identical postions within the room, will the suckout remain?

More or less - YES (changing the height of the woofers will only affect reflections from off the floor and ceiling - the excitation of one mode only).

Does the room have the final influence on reproducing the frequecy or can it be overcome with a different delivery from the speaker?

No - you can actually change somewhat the severity of suckouts and peaks by moving the speakers around and changing your listening position (affects two modes). Don't place speakers in the corner and don't sit in the exact middle of the room, for example.

However the fundamental room modes do not change as they are related to room dimensions that cause reinforcement or cancellations. What you change is the degree to which they may be excited and the degree to which they are audible.

Looks like Shadorne has already given you all the bad news. You can only reduce the effect but it won't go away entirely.

In many of the audio rooms I have measured, a suckout between 55 and 80Hz is very common but can be reduced by sitting closer to the back wall (i.e., farther from the speakers). Give that a try first since it is generally easier than moving speakers. Sometimes it only takes a few inches to make a noticible difference. The downside to doing this is that lower bass will get amplified but that may not be a problem - or at least not as much as the suckout. Can't win them all anyway.

Arthur

The two answers already posed are correct. However, there is a third answer (not direct at what you said, but it works). Bass traps. Most people think of bass traps as taking bass energy away, however, there are types of designs that actually change the phase of the bass energy and thus create different interference patterns. The result is both a reduction in the peaks and an increase in the nulls. Will it solve the problem? Don't know without a lot more information, but there's a good chance it would.

I am using a digital Radio Shack meter and Stereophile test cd3 which I've been told is not very accurate in the bass. I know Rives has a test cd calibrated for the analog Radio Shack meter. I only have the digital meter and wonder if the Rives disc would be a better source for making measurements than the Stereophile tracks? Using my current test equipment, I referenced 80db at 1khz and my greatest variation is -7db at 63hz and +4db at 40hz.

The system sounds good but lacks some punch. I'm always looking for improvements.

That is not bad freq response - probably better than average. I see you have some acoustic treatments already. Have you considered a PARC?

The Rives CD works with the digital meter as well, though it's calibration was done with the analog. The digital is within 1 to 1.5 db the same response as the analog in all the tests we've done.

I agree with everything said so far; however, I'd like to add that interaction with the wall behind the speakers is hypercritical, particularly if the speakers have rear-firing ports. You can excite a node and then attenuate it by moving a speaker fractions of an inch. See the thread about the Sumiko speaker set for details of the successful experience I just went through.

I think that optimizing the set, given your speakers, room and seating position is a first step, then work with room treatment.

Dave

Using my current test equipment, I referenced 80db at 1khz and my greatest variation is -7db at 63hz and +4db at 40hz.

I would be thrilled with that result.

I ordered the test cd from Rives and will see how that compares with the Stereophile cd. I do not suffer from any bass boom at all. It's just a general feeling that I get more thud than thump.