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Multi-Way Conventional loudspeakers with crossovers

4 midranges + 1 tweeter: do MTM or don't ?
4 midranges + 1 tweeter: do MTM or don't ?
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Old 19th May 2018, 08:44 AM   #1
Vortex is offline Vortex  Hungary
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Default 4 midranges + 1 tweeter: do MTM or don't ?

Hi all, I'm going to use 4 midranges with 1 AMT tweeter per side in my new build. All this as a "line array" on top of eachother and the whole section of course on top of the 1x 18" (maybe 21") woofer.

But I think I might ask you what you think about the arrangement of all these.

Considerations:

- Knowing the directional pattern of AMTs (narrow vertically), keeping tweeter at/around head height is crucial. I'll be sitting on the sofa most of the listening time. I try to imagine woofer height + box wall thicknesses + 4x 6" midranges on top of eachother as close as possible + tweeter. Tweeter might be a bit high, especially when the whole midrange section is on top of a 21" woofer (bigger diameter obviously than a 18" woofer).

- in this setup, the tweeter's VC plane will be shifted a bit to the back to be time-aligned with midrange voice coils to maintain a straight forward pointing lobe (active setup, 3-way 4th order LR).

- What do you think of going MTM with a flat front plate ? M-M-T-M-M ? Inspired by Status Acoustic's Titus 8T. I know MTMs have a straight forward pointing lobe as well, but more narrow vertically than a single M-T setup (or M-M-T).

- What do you think about doubling the tweeters ? (No sensitivity and impedance issues in an active setup). Like M-T-M-M-T-M. 2 lobes on top of eachother or do we have some nice advantages here ?

- 4 tweeters ? (Although cost is insane then). M-T-M-T-M-T-M-T. It might behave like a line array, a vertical cylindrical lobe. Inspired by PS Audio's Infinity IRS V (in a smaller form factor).

- Or nothing to do at all, staying with M-M-M-M-T as originally intended ? I won't sit very close to the speakers so despite tweeter being a very little bit above head position it still might be a good setup.

Any opinions are welcome.
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Last edited by Vortex; 19th May 2018 at 08:48 AM. Reason: typo
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Old 23rd May 2018, 09:34 PM   #2
DougL is offline DougL  United States
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I'm not a line array expert by any means, but I would put the tweeter next to the line of midranges at ear height.
Keeping the midranges in a line may have advantages in vertical dispersion to better match the tweeter.
I don't think that the crossover will be significantly harder side by side vs. the mmTmm, etc.
If you are doing a passive crossover, I would add enough tweeters to roughly match sensitivity. For active, not so much.
I would also look at a Chaucer Elliptical crossover. I understand you get less phase shift for the same target slope than the comparable Butterworth or Linkwitz Riley topologies. YMMV, LOL.

HTH
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Old 24th May 2018, 06:15 AM   #3
TMM is offline TMM  Australia
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Depends where you intend to cross, but MMMMT might alleviate some floor bounce effects compared to MMTMM, and the cabinet is shorter too.
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Old 24th May 2018, 06:20 AM   #4
adason is offline adason  United States
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How about this?
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Old 24th May 2018, 06:22 AM   #5
adason is offline adason  United States
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Other option would be Nola like short line array of mids. I would place tweeter in the middle but on the side, as not to break the line array.
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Last edited by adason; 24th May 2018 at 06:24 AM.
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Old 24th May 2018, 02:29 PM   #6
Vortex is offline Vortex  Hungary
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Send a message via ICQ to Vortex 4 midranges + 1 tweeter: do MTM or don't ?
Hmm now you all made me think ..thanks for the suggestions.

I know the most ideal source of sound is point-like and I'd like to be close to this at least on one plane: horizontally. Thats's why I wouldn't try to put tweeter next to the midranges but rather do MMTMM or MMMMT. However I haven't heard of any midranges put next to eachother this way (e.g. 4 midranges in a 2x2 setup) .. until (and below) a certain frequency and center to center distance they might behave as 1 midrange unit together.. hmm this is a white spot on my map, I'm a little bit afraid of it. But I might try this in 2x2 with the tweeter next to them, the M-T box is a separate one and I can have both versions made and listen to them for a while before painting.
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Old 24th May 2018, 02:37 PM   #7
Vortex is offline Vortex  Hungary
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Send a message via ICQ to Vortex 4 midranges + 1 tweeter: do MTM or don't ?
Quote:
Originally Posted by TMM View Post
Depends where you intend to cross, but MMMMT might alleviate some floor bounce effects compared to MMTMM, and the cabinet is shorter too.
Good argument, thanks.

Planned crossover points are 125 Hz and 2 kHz.

The tweeter's factory recommendation is 1000 Hz with 12dB/octave 2nd order so I might go a bit lower than 2k but for safety reasons and power handling I chose 2k (and the filter is 24dB/oct 4th order).
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Old 24th May 2018, 04:00 PM   #8
zmyrna is offline zmyrna  United Kingdom
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Has anyone tried these MMTMM configurations?
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Old 24th May 2018, 04:29 PM   #9
Patrick Bateman is offline Patrick Bateman  United States
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Adason is right, this is how you do it:

Click the image to open in full size.

You can find the patent online. The speaker was designed by the same dude who has the patent on the Aurasound Whisper.

A couple of forum members have published similar designs:

@melo theory : The Portal....a controlled dispersion tripole

@follgott : Pseudo-coaxial with narrow directivity (and Horbach-Keele filters)

If you build one, be careful with the spacing. If it becomes too large, you'll reach a point where you'll get a dip in the midrange that's impossible to fix. You want to keep that spacing tight.
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Old 24th May 2018, 06:35 PM   #10
Vortex is offline Vortex  Hungary
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Send a message via ICQ to Vortex 4 midranges + 1 tweeter: do MTM or don't ?
Great, re-considering. I'll try both versions with 2 raw mdf boxes.. this one on the pic and the MMMMT original one. Then the measurement mic will tell the rest.

Do you know a maximum center-to-center distance for a certain frequency where above that freq. they don't behave as one ? Something with 1/2 wavelength or so ? Dunno anymore.. :/
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