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Multi-Way Conventional loudspeakers with crossovers

Modular active 3 way - work in progress
Modular active 3 way - work in progress
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Old 6th August 2019, 04:12 AM   #101
DonVK is offline DonVK  Canada
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Default two 8" woofers, two chambers

Two hours and $20 later I have a new woofer enclosure. This one was built for 2 SilverFlute W20RC3808 8" woofers to see if I can improve the bass/midbass response.

A quick run of HornResp provides Qtc=0.8 with about 20L/chamber (pic#1). So mine are actually 22L to account for the magnet and other material (acoustic tile + fiberglass) in the chamber (pic#2).

The measured individual woofer response is very close (pic#4) to HornResp. The THD (pic#5) is low and looks fine.

The system measured system response after level adjustment is show in pic#6, and #7. I've only had 1 hours to listen (@90dBc@1m) and it sounds good so far. I would prefer the woofers closer together and higher up near the midrange but I also don't want it any wider or deeper. Still thinking about how to do that.
Attached Images
File Type: jpg HornResp2x8in.jpg (70.7 KB, 171 views)
File Type: jpg DSCN7743r.jpg (147.2 KB, 171 views)
File Type: jpg DSCN7746r.jpg (411.8 KB, 171 views)
File Type: jpg SPL SilverFlute W20RC3808 nearfield.jpg (96.0 KB, 174 views)
File Type: jpg THD SilverFlute W20RC3808 nearfield.jpg (105.2 KB, 170 views)
File Type: jpg SPL System with 2x W20RC3808 @1.6M.jpg (99.0 KB, 34 views)
File Type: jpg THD System with 2x W20RC3808 @1.6M.jpg (98.1 KB, 32 views)
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Old 7th August 2019, 07:18 PM   #102
DonVK is offline DonVK  Canada
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I thought about it some more and and moved the woofers closer to the midrange. There are now two irregular chambers of equal volume (22L) that allow closer woofer spacing. Despite the different chamber shapes both woofers measure very close in the nearfield. Damping material is acoustic tile and fiberglass.
Attached Images
File Type: jpg DSCN7749r.jpg (149.2 KB, 27 views)
File Type: jpg DSCN7752r.jpg (522.3 KB, 41 views)
File Type: jpg SPL 2x W20RC3808.jpg (73.1 KB, 47 views)
File Type: jpg THD 2x W20RC3808.jpg (84.3 KB, 29 views)
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Old 7th August 2019, 10:02 PM   #103
Dave Bullet is offline Dave Bullet  New Zealand
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Are you planning a 3 or 3.5 way? With a midrange xo point @ 725Hz - I wonder for a 3 way what lobing / issues might result with the lower woofer that far away from the midrange? Of course the impact will lessen (?) the further away the listening distance.
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Old 7th August 2019, 10:53 PM   #104
DonVK is offline DonVK  Canada
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Hi Dave,

The speaker is a 3 way with a BP6 sub beside it. The 8" woofers are in parallel and the wood space between top woofer and midrange perimeter is 3cm. So that leaves 20cm C-C between the mid and top woofer. The two woofers need to be considered together not independently (see below).

I listen at approx 2m from the speaker and have not noticed a problem yet, but it's still early I did have issues with the initial version so I changed it to push both woofers up.

Yes you can get some nearfield lobing, compare the BEM sim of a single 6.5" in Modular active 3 way - work in progress to the dual 6.5" in Modular active 3 way - work in progress .
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Old 14th August 2019, 12:08 PM   #105
wintermute is offline wintermute  Australia
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Modular active 3 way - work in progress
looks good Don, Did you use a sloping baffle between the two volumes? I was trying to think of a way you could achieve what you wanted, and you obviously worked it out!

Tony.
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Old 14th August 2019, 12:47 PM   #106
DonVK is offline DonVK  Canada
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Hi Tony,
Yes, the box is split diagonally using a sloping internal partition. I was pleasantly surprised that the near field's measured so close given the different chamber shapes.
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Old 14th August 2019, 01:02 PM   #107
wintermute is offline wintermute  Australia
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I got as far as the sloping baffle and then started worrying about the asymmetry, it appears that it wasn't a problem! That's the great thing about doing actual experiments! Keep up the great work

Tony.
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