Placing a vertical MTM horizontal?

MarkRoberts · 07-19-2004, 07:03 PM

I have built a set of Dayton 8's from speakerbuilder.net
I would like to build a matching center channel when I go front projection and was wondering if there are changes required to the crossover to place it horizontally? I have emailed Wayne J. at speakerbuilder.net and haven't heard anything. I am also going to email Dave Tenney since I believe this was his idea and wayne did the crossover modeling for him. Yes I realize we are talking about a very large center channel I may modify the box size and use pr's instead of ports I dont know yet. Main concern now is the crossover.

Patrick Sun · 07-19-2004, 09:34 PM

If the screen was sufficiently acoustically transparent, it might be a better idea to just build another MTM and keep it in its vertical orientation and place it behind the screen.

If you turn the MTM on its side, you may notice some lobing issues in its dispersion from the center channel position. The only way to find out is to just wire one of the MTMs as the center and listen to it on-axis and off-axis (how far off-axis is up to you).

Just recently this topic was brought up, here's page 2 of the thread:

http://www.hometheaterforum.com/htfo...=&pagenumber=2

ThomasW · 07-19-2004, 09:50 PM

The short version is that they need to be built with the tweeter mounted off center and the crossover needs to be redesigned.

MarkRoberts · 07-20-2004, 06:59 AM

They are already designed with the tweeter offset 3/4" from the mid's. I figured it would be okay as long as it is offset towards the top? yes,no maybe

MarkRoberts · 07-20-2004, 07:09 AM

Patrick thanks for the link interesting stuff. Although I don't understand why such a great debate over off-axis performance? To me it seems a moot point, why on earth would you sit off-axis in your own home theater? It just doesn't make sense to me. Obviously if you have an absurdly large home theater say 20'-40' wide I can see the point but the average home theater is probably more like 10'-14' wide.

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ThomasW · 07-20-2004, 11:24 AM

The offset direction is only important if the box is above or below the TV. And usually the offset is more than 3/4" of an inch

The lobing and comb filter effects are noticable at narrower distances IF the crossover hasn't been 'adjusted' for the box sitting horizontally.

MarkRoberts · 07-20-2004, 01:22 PM

ThomasW,
How does one determine how to 'adjust' the crossover, so the box can be horizontal? The towers were only my 2nd diy project. So please excuse me if it is a dumb question:b .

ThomasW · 07-21-2004, 12:06 AM

Basically one completely re-engineers the crossover to use the tweeter at the lowest possible frequency. This means steep XO slopes for both the tweeter and woofers.

RodN · 07-21-2004, 09:19 AM

To define whether you think horizontal placement is desirable just try what you have horizontally. SIt in your listening position and get someone to sit the speakers you have horizontal, then vertical. You'll be surprised at the difference in sound and it might change your priorities.

For me front projection was an opportunity to return my center speaker to its correct vertical position because there was no TV box to have to sit it on anymore.

Rory Buszka · 07-25-2004, 12:15 PM

There is a good chance that the crossover of the Dayton 8's is already optimized to use the tweeter to the lowest possible frequency, because such special crossovers were already needed to ensure that the tweeter would mate well with the woofers, which are not known for clear and detailed midrange (which necessitated such a crosover design).

Dan Wesnor · 07-28-2004, 08:33 PM

I'm also curious as to what would need to be done to the crossover, and why. Assuming the XO was designed properly to begin with, I can't think of anything. Nothing can be done about the lobing, it's the same if the speaker is horizontal or vertical, the axis just changes. And comb filtering occurs if the XO is too high, even in an MT. (Comb filtering is just another form of lobing.)

Turning an MTM sideways is never a good idea, simply because your more likely to hear the problems of an MTM with it oriented that way. But those problems exist vertically, you're just not very likely to be standing up when you're watching a movie.