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Multi-Way Conventional loudspeakers with crossovers

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Old 10th January 2012, 05:11 PM   #1
bjuck57 is offline bjuck57  Sweden
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Default P-Audio BM15CX38 in MLTL cabinets

Dear fellow diy:ers,

Just wanted to post some photos of the MLTL cabinet I just finished for the P-Audio BM15CX38 coaxial drivers. The cabinet is designed by 'GM', who helpfully calculated the dimensions for me when I was inquiring at the yahoo MLTL group, if anyone had built such cabinets for those specific drivers. Many many thanks to GM!!
First impressions is that bass continues to improve after some
10 hours play time. The bass is now very powerful, and I can still hear improvements after each session. Big and dynamic soundstage from the coaxials. All in all, I am VERY impressed with GM's design and the MLTL type of enclosure. What I have to do now is build a proper crossover; I only use a 2.2uF capacitor for the tweeter right now.

Hans in Sweden.
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Old 10th January 2012, 05:50 PM   #3
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I have a pair I might try this build
Any plans?
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Old 10th January 2012, 05:53 PM   #4
Pano is offline Pano  United States
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Very nice. Thanks for posting!

I've heard all the P.Audio coax drivers except the 15". All very nice. I have heard the 18" on OB and in a big box. The box version used the single cap, OK, but it needs a better crossover to live up to its potential.

You've got a great speaker and box. Make a great crossover and there will be few that can touch it.
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Old 10th January 2012, 06:06 PM   #5
bjuck57 is offline bjuck57  Sweden
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Bigfishe:
Cool that you are interested in building!
Here are the dimensions GM calculated:
[~10 ft^3 net]

L = 54.25"
WxD [CSA] = 323"^2 [suggest 14.12" x 22.88"]
Zdriver = 18.93"
Zport = near/at bottom
rport = 4" min.

Pano:

Thank you! I am also using this driver in an open baffle build (standing next to the MLTLs in one of the photos above), very much inspired by John Busch's Altec 605 build. I am VERY intrigued by John Busch's 'Big Boys' as well as his Manzanitas. Especially his new Ultra floorstander.
Do you think the 'Christmas crossover' you designed for the BM15CX38 a couple of years ago (I've got a jpeg of this crossover) would work for both my MLTL and open baffle speakers? The coaxials in the ob are actively crossed over at 80 Hz to a pair of GW-1858 woofers.
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Old 10th January 2012, 06:24 PM   #6
Pano is offline Pano  United States
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I'll see if I can find the crossover. Post it if you have it.
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Old 10th January 2012, 06:30 PM   #7
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So whats the tuning on that bad boy?
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Old 10th January 2012, 06:33 PM   #8
bjuck57 is offline bjuck57  Sweden
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Pano here is the crossover you designed.
Attached Images
File Type: jpg BM15CX38_cc2.jpg (36.5 KB, 544 views)
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Old 10th January 2012, 06:40 PM   #9
bjuck57 is offline bjuck57  Sweden
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Bigfishe, I think GM was aiming tuning at somewhat below fs of 34Hz in his calculations.
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Old 10th January 2012, 06:48 PM   #10
Pano is offline Pano  United States
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Thanks for the reminder. No, that would not work well for an OB version as it does not take into account the rising response of the woofer on an open baffle. That fact that you are filling in with a helper woofer would make it a lot closer than without, but it would not be optimum.

John's crossover for the 18" would be a better place to start, but the crossover point would have to move up, considering the difference in the size of the "Horn" (the cone).

Do you have a way to measure the frequency response? That would be a big help.
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