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.
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.
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.
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.
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.
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.
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.
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.
)
The 4" radius minimum vent x 3/4" thick baffle sims ~39 Hz in MJK's original PORTED MathCad worksheet, so would need to either be longer and/or damped to near aperiodic as required for lower tunings.
Sim uses published T/S specs with minimal damping, 0.1 ohms series resistance [will be more if a passive XO is used], so would need some form of EQ to tonally balance it out over a wide BW in larger, more open rooms and/or if positioned well away from any wall boundaries.
FWIW, I use a couple of cheap ~25 ohm pots to experiment with differing series resistance to dial in the basic shelving if required. Note that IME the resistance required isn't the same for both speakers for best overall in-room balance at the listening position [Lp].
GM
Attachments
Ohm sweet ohm!
Just finished building the crossover designed by Pano. A fun build with parts I ordered from Parts Express. After replacing the 2.2 uF caps with the crossovers I immediately concluded that the PA midrange shout was gone (I can't hear it anymore). A funny thing is that I can't detect any similar PA midrange shout with the same cap and drivers mounted in open baffle. I'm very pleased with the improvement the x-over has made in my MLTLs, and want to thank you Pano for designing and sharing the x-over and GM for designing the MLTLs. This has been a fun build from start to end! I currently use a Cambridge 840V integrated solid state amp for the speakers, but will soon hook up a SE300B tube amp instead.
Just finished building the crossover designed by Pano. A fun build with parts I ordered from Parts Express. After replacing the 2.2 uF caps with the crossovers I immediately concluded that the PA midrange shout was gone (I can't hear it anymore). A funny thing is that I can't detect any similar PA midrange shout with the same cap and drivers mounted in open baffle. I'm very pleased with the improvement the x-over has made in my MLTLs, and want to thank you Pano for designing and sharing the x-over and GM for designing the MLTLs. This has been a fun build from start to end! I currently use a Cambridge 840V integrated solid state amp for the speakers, but will soon hook up a SE300B tube amp instead.
Attachments
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P-AUDIO BM15CX38 COAXIALS IN MLTL CABINET BY GREG MONFORT CROSSOVER BY PANO PIC6 small.jpg -
P-AUDIO BM15CX38 COAXIALS IN MLTL CABINET BY GREG MONFORT CROSSOVER BY PANO PIC7 small.jpg -
P-AUDIO BM15CX38 COAXIALS IN MLTL CABINET BY GREG MONFORT CROSSOVER BY PANO PIC10 small.jpg -
P-AUDIO BM15CX38 COAXIALS IN MLTL CABINET BY GREG MONFORT CROSSOVER BY PANO PIC11 small.jpg
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