Improving horizontal dispersion on MTM

[FirebirdTN]

I'll start by saying I am probably going to be doing something very unique and probably not recommended, but the way I see it, I don't have anything to loose...

I have never been satisfied with the dialog from my setup. To make a long story short, it is most DEFINATELY due to the MTM design, and my seating positons are off-axis. This is a modest little living room setup, not a dedicated HT room.

For mainly asthetic reasons, and monitary reasons, I want to stick with the speakers I have now; however want to modify my center channel to provide a wider dispersion pattern.

So...In another thread of mine, rabbitz suggested I try angling the midbass drivers away from each other.

I was also thinking about moving the tweeter up as far as I can out from the middle of the midbass drivers.

These are inexpensive little speakers, so the way I figure, I don't have much to loose, and hopefully something to gain.

Some questions:

I am wondering how the response of a speaker will change, if I keep the drivers and crossovers the same, and not modifying them in any way and possibly do one (or more) of the following:

1) Driver placement (modify the MTM to move the tweeter from the middle of the midbass drivers)

2) Increasing enclosure size?

3) Changing from a rear-ported enclosure to a front ported enclosure? Also, how crucial is port placement on the baffle?

It just so happens that I have an extra set of midbass woofers, tweeter and crossover from the origional center that fell off my TV and hit the floor, which busted the cabinet. Is this fate? Luckily, I was able to obtain a replacement, so I have this "extra" to play with...

Another alternative I had thought about was instead of modifying the MTM design, is just put a single midbass/tweeter combination together in a vertical fashion the same as the satellites. My speakers just so happen to use the same tweeter and crossover in the center and main speakers. Only thing I would have to purchase if I did this was a new satellite driver (8ohm) vs the pair of extra center channel drivers I have now (16ohm).

This maybe crazy, but the way I see it, it won't cost me much if anything at all, will have the same visual appearance as the factory look with the grills on, and the way I would do the mod would not destory any of the factory parts, so that if disaster happens, I can always reassemble them and they still retain value.

If modifying the speakers changes the response a little, I am not too concerned. In my case, I am not after rurler flat response, nor do I expect perfection. On the other hand, if what I suggest is going to radically change the sound, let me know. I have a good electronics background, but ZERO speaker building/modding/acoustic background.

Thanks for input.

-Alan

[BerntR]

The closer you keep the drivers together the better dispersion you will get. Spacing them apart seems not like a good idea.

The easy - and sonically best(?) - solution would be to rotate the speaker 90 degrees. Then you will get good horisontal dispersion and limited vertical dispersion.

Bigger cabinets will probably give more output in the bass range.

Putting the speakers in a bigger cabinet is probably not a problem for the x-over etc. But you should be on top of speaker in cabinet response simulation before you do that.

Rear ported vs front ported. Ports tend to give out of phase response in certain frequencyes far above their intended working range. Backfiring or downfiring will attenuate this effects. But as you can see from a number of commercial speakers it is not a big issue.

A vertical MT design is a good idea, but then you will have to address the x-over to get a decent result.

[Dryseals]

You might try angling the speakers off center a few degrees. I had some old 4" Bose speakers I took out of the Corvette, 2.1 ohm each. They sat around for quite a while and where getting in the way. So one day I decided to build a little center channel for my sons room and rather than buy new speakers, I thought I would use these. I angled each just a few degrees to give me wider coverage and popped in a used AR metal dome tweeter. Cheap cap for a crossover and tried them out. They actually sounded great, enough so that I use them in my system. Now I need to build another for him.

I havent done any tests, but I think the few degrees of angle on each speaker really made a big difference, there is no dirrected sound from them so they fill the room.

Loosen the mounting screws and roll each off center a tad. Stuff some paper in the crack for a temporary plug and see if it makes a difference, can't hurt.

[infinia]

using MTM alignment
rotate Mids opposite 15-30 degress away from center.
Try to increase mid level a couple of dB to still get flat response on center. Something to try not sure if it'll work, depends on how anal you want to get.