Designing x-overs - account for room effects?

[black300zx]

Some background on my projects:
Input on some MTM's

Right now I'm in college, commuting back and forth from my parent's house. The set of MTM's I'm designing I hope to keep for a long time, which is why I'm starting with higher end drivers, and why I'm setting the bar high for their performance. I don't want to "outgrow" these speakers in a year or two and get the urge to build something better. These will hopefully combine with the stereo substage (that do dual duty as stands for the MTM's, see pic in above thread) to be a full-range 2channel setup for a room in my house, once that time comes.

Now for the question/problem:

My room is pretty small, and has horrible acoustic properties. The only sound treatment I could really do is to put a couple foam wall tiles (likethis) on the side walls a few feet infront of the speakes to hopefully reduce early reflections. The room is obviously going to impact the f/r of the speakers greatly, and it's effects surely will be different from those of the room that they'll reside in in the future. I'm probably going to be living in this room for at least another year and a half, and up to maybe up to almost 3. Should I try to design the x-overs for these MTM's around my current room, in an attempt to get a smooth/flat in room response w/o equalization, then redesign the x-overs in the future when I move? Or would it be a better idea to design them to have a flat on/off-axis anechoic response, and simply use some equalization to correct the in-room response? The future room will likely be much bigger, and will have some acoustic treatments, so room effects shouldn't be as significant as they are in my room.

One thing to consider - I'm building these speakers with an external box for the x-overs, so the x-overs will be easily accessible for modification, or complete replacement.

[myhrrhleine]

Personally, I'd design the best crossover I could and use a cheap equaliser for a temporary fix.

Then, later, i'd upgrade the EQ inside parts.

[black300zx]

any other opinions?

[DSP_Geek]

What M. said. Correcting the room with the crossover is _not_ the way to go because you'll be tweaking endlessly. That might be fun to some folks (said the master of alligator clips), but when you move there's already enough aggravation that you don't need a week of fiddling with your crossover to enjoy music, especially since the new room is likely to have FR aberrations someplace else anyway!


Cheers,
Francois.

[lndm]

Just what sort of corrections are you talking about?

eg: I feel a gentle tonal skew across the spectrum can be fixed at the crossover. So can a compensation for a live/dead room sound, and bass integration with the size of the room and personal taste should, I feel, also be dealt with at speaker level where possible.

[infinia]

Hi
I would just add a couple DTDP switches with labels on the back wired to the crossover.

Examples of the 2 switch labels could be
Nearfield/ Far
Hot Room/ Normal Room

[black300zx]

Originally posted by lndm
Just what sort of corrections are you talking about?

Not really sure. This is my first real attempt at designing a set of speakers completely from scratch, and it's going to be a fairly long term project. I expect it to drag out probably until the fall, if not longer, due to me being in school and having to work. I don't have the speakers yet, so right now I'm just in the planning stage, trying to figure out how to approach designing them. Basically what I was asking was this:

If I wind up with an anomally in the response due to the interaction with the room, and it can be corrected by tweaking the crossover, or by eq'ing, which route is better? From the few replies I've gotten so far, it seems like it's just a narrow spike or dip in the response, then eq'ing would probably be the best approach. If it's over a wider range, and it can be corrected in the x-over, then that may be the better route.

Thanks for the input, it's appreciated. I'm sure once I get into the actual design phase I'll have plenty more questions.

[lndm]

The following is my opinion.

Spikes and dips that cover a very small frequency range can be safely ignored.

Speakers need to be chosen to suit the room vis-a-vis their 'size' or bass depth versus the room.

Speakers and listeners need to be positioned so as to avoid gross anomalies.

EQing, to suit anomalies is a matter of taste. It will alter the balance of sound in the room as a whole. I prefer not to use it myself for room dips and peaks, but I will EQ the bass contour if it suits a design, or the treble level if I feel the need.

[Cameron Glendin]

Perhaps just use a variable l pad (pot style) for the tweeter is all thats needed.
The acoustic tile idea will work very well from experience, it is also good to place damping material behind and if possible next to the box for the earliest reflections if close to the walls. This is in my experience the most dramatic improvement one can make.