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Multi-Way Conventional loudspeakers with crossovers

Does changing the enclosure shape from rectangle -> curved modify the sound?
Does changing the enclosure shape from rectangle -> curved modify the sound?
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Old 8th November 2018, 09:17 PM   #1
scone is offline scone  United States
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Default Does changing the enclosure shape from rectangle -> curved modify the sound?

I'm considering (very early stages) of building an dual purpose MTM speaker (for music and home theater) and I'm very much drawn to the aesthetics of curved enclosures done by transverse laminated birch plywood. I'm imagining something similar to this design but without any of the metal: Cross-post from r/DIY-- I built some really nice speakers : diysound

There are TONS more well established MTM designs out there for standard rectangular enclosures than for curved ones (in fact I can't really find a single documented curved design MTM that's been built more than once... someone please link a design if you know of one!) Can I borrow a design using a rectangular enclosure and build it using a curved enclosure so long as I keep the same internal volume? Will the curvature itself and the intentional narrowing near the back effect the sound or response in any way?
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Old 8th November 2018, 09:53 PM   #2
DougL is offline DougL  United States
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The curved surface will reduce diffraction, which could affect voicing.
The curved surface could also change the baffle step frequency, depending on the shape.
IMHO, it's a different speaker.
It may have the potential to be a better speaker, but you will need to voice it.
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Old 9th November 2018, 12:31 AM   #3
Soldermizer is offline Soldermizer  United States
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Likely some acoustical changes. Some simple, like changing (spreading out = good?) the interior resonances. But mainly, I imagine it shows off your woodworking skill
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Old 9th November 2018, 12:18 PM   #4
AllenB is offline AllenB  Australia
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Rounding might be more effective on the front.
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Old 9th November 2018, 04:23 PM   #5
jReave is offline jReave  Canada
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I have done exactly what you are proposing with excellent results.

The key is to keep the cabinet width and height and the driver positions on the front baffle as close as possible to the original. No more than a 10% deviation will keep any baffle diffraction changes to a minimum. Adding the large radius curves to the front probably means that the width must be increased so that's the one you need to watch out for. And given the change from rectangular to curved sides probably also means that you will need to increase the depth to maintain the same original internal volume. Not a problem to change that one. In fact a curved internal inverted horn type of shape offers a couple of design benefits - less internal standing waves and better attenuation of the rear sound energy.
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Old 9th November 2018, 05:56 PM   #6
LineSource is offline LineSource  United States
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1) A cabinet of the spec volume with curved sides and rear can modestly reduce resonance effects. A standard rectangular cabinet with a "V-shaped" internal brace behind the midwoofers, plus rear absorption material, can be more effective at resonance reduction.
2) One example of MTM with large radius edge rounds on the front baffle to reduce distortion.
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3) The MTM topology produces a center lobe radiation pattern which favors seated couch listeners.

4) Would a floor standing TMW 3-way fit your room plans? More uniform radiation pattern. Cleaner midrange. Real stereo bass.
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Old 14th November 2018, 12:19 PM   #7
Mattes is offline Mattes  Germany
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Hi Scone,

you´ve asked about the sonic improvements, and I might add my experience along the way with my speakers, although of a quite different conception.
I found that minimising diffraction (and in the same way, minimising baffle effects in my dipole OB system) will lead to
- a more precise system with less "hash" will give you a better insight and a clearer view onto the music (sorry if I sound not precise, English is not my mother language). This can actually distract your musical joy, as you´ll hear more of the problems inherent in either recording and design... but if all else is right, a good thing in my book.
- a better localisation of instruments in 3-D space, given all else is right.
- less listening fatigue, given all else is right.

So, if you´re able to invest time and money in diffraction control, this is a good thing in my opinion. For all technical matters and a lot more input there are several threads here on this forum, like this one

Baffle Diffraction

It all depends on how much efforts you´re willing to invest - for cheap systems there´s a barrier somewhere - but it will pay out in the end.

All the best

Mattes
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Old 15th November 2018, 08:45 PM   #8
scone is offline scone  United States
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Thanks for the answers all, this is very helpful. I don't anticipate wanting to change the shape (or amount of rounding) of the baffle, so I guess I shouldn't see too many differences? I have to clarify that this is 100% for visual aesthetics, I'm not hoping to improve upon any speaker designs, I just don't want to audibly detract from them either.

As far as changing the voicing, will this be something that can I address after the cabinet is built by tweaking the components in the cross-over? I just don't want to build myself into a hole after having spent $100s on components and many hours on a cabinet only to discover there's no way to make it sound good.
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Old 15th November 2018, 08:49 PM   #9
scone is offline scone  United States
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Quote:
Originally Posted by LineSource View Post
2) One example of MTM with large radius edge rounds on the front baffle to reduce distortion.
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Yeah this is one of things I learned *after* building my first set of speakers (also an MTM) way back in 2004. I'm still listening to them and still enjoy them but I would definitely round the baffles a LOT more next time.

Quote:
3) The MTM topology produces a center lobe radiation pattern which favors seated couch listeners.

4) Would a floor standing TMW 3-way fit your room plans? More uniform radiation pattern. Cleaner midrange. Real stereo bass.
I don't mind that it favors couch listeners. That's precisely where I'll be sitting when I listen to them.
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Old 15th November 2018, 08:52 PM   #10
AllenB is offline AllenB  Australia
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Yes, you could do that.
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