How would i modify a chang for BOFU MTM? - diyAudio
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Old 12th March 2017, 08:54 PM   #1
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Default How would i modify a chang for BOFU MTM?

I have 2 pairs of Pioneer B20 BOFUs!

Had originally intended to build a curvy chang (a while ago now). But not really happy with workmanship thus far and didn't finish them - did learn a few things for the next build.

Also figured 2 pairs must certainly be better than 1! Hence the MTM double BVR idea.

So thought about 2 half changs - one inverted on top the other without the divider. No curve also reduced size (both visually and timber requirements) but not sure at what cost sound-wise?

This would make it around 2.2m tall - a bit much maybe?
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Old 12th March 2017, 09:37 PM   #2
jimbro is offline jimbro  United States
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What tweeter for MTM? I have half-changs that I've used with bofu's and 206en's and the bass is very impressive with either driver. I would suggest a fast type arrangement with the bofu's crossing at about 300 hz to a smaller full range. How big is your room and how far will you be from the speakers? Unless you have a very large room, I think one pair per side is plenty.
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Old 16th March 2017, 04:12 AM   #3
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That's a sensible response!

I'll persevere with the changs I've half built. Was originally going with the curvy type but may build straight fronts instead.

re which tweeter - I have a couple to try (can't remember models off hand). Also have a pair of B3N and CHR70 for potential fast build.
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Old 17th March 2017, 01:09 AM   #4
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Originally Posted by microdub View Post
Had originally intended to build a curvy chang (a while ago now). But not really happy with workmanship thus far and didn't finish them - did learn a few things for the next build.
Was this what you were trying to build?

https://www.upload.ee/image/1173829/DSC06787.JPG

What went wrong?
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Old 17th March 2017, 01:32 AM   #5
chrisb is offline chrisb  Canada
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All of Scott's designs are carefully though out, and more is definitely not necessarily better.

It sounds like you've not even finished the first pair of Changs, so I'd say it's premature to assume a single driver per side as originally designed wouldn't be sufficient in terms of sensitivity and bass response. Not having heard a Bofu, it'd be presumptuous of me to make any suggestions as to how to improve upon them. If you eventually do find them needing help in the top end, remember that the CHRs - while being fine drivers- are open backed full range units, and would need to be isolated from the Bofu's main chamber, and that the volume lost in doing so could compromise the bass response. Id think a sealed back tweeter such as perhaps the FT17H would make more sense in such a case.
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Last edited by chrisb; 17th March 2017 at 01:40 AM.
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Old 18th March 2017, 06:22 PM   #6
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Maybe something like this?

20?????????????D-7MK??FE206En?FE208E? - ??????????ALTEC?JBL???????????
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Old 19th March 2017, 11:00 PM   #7
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Originally Posted by hollowboy View Post
Was this what you were trying to build?

https://www.upload.ee/image/1173829/DSC06787.JPG

What went wrong?
Yep, they are the ones. Nothing went wrong - just wasn't happy with my wordworking skills (relatively new to building speakers).

Coupled with home renovations, work, young family....I also got distracted with restoring a pair of (Australian) Axis LS88 and fishing, cycling....

So put them on the backburner, but I think I'll keep at them - tidy up whats there and finish them.
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Old 19th March 2017, 11:07 PM   #8
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Quote:
Originally Posted by chrisb View Post
All of Scott's designs are carefully though out, and more is definitely not necessarily better.

It sounds like you've not even finished the first pair of Changs, so I'd say it's premature to assume a single driver per side as originally designed wouldn't be sufficient in terms of sensitivity and bass response. Not having heard a Bofu, it'd be presumptuous of me to make any suggestions as to how to improve upon them. If you eventually do find them needing help in the top end, remember that the CHRs - while being fine drivers- are open backed full range units, and would need to be isolated from the Bofu's main chamber, and that the volume lost in doing so could compromise the bass response. Id think a sealed back tweeter such as perhaps the FT17H would make more sense in such a case.
Not so much improving the changs as they are (way beyond my abilities as my understanding of speaker theory and design is in its infancy) but just using the 2 sets of BOFUs I have in the one build.
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Old 19th March 2017, 11:13 PM   #9
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Originally Posted by Godzilla View Post
Nice! love the literal translation in google translate. Reminds me of instructions translated from Chinese.

I just moved on a large pair of BLH (similar in size to the ones in the link) which used a pair of 12" Plessey full range drivers. I also tried them with a pair of Philips AD12202 - but they both felt a bit strangled/constrained.

Anyway, my wife suggested strongly that it was time to let go of really big speakers...
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Old 19th March 2017, 11:19 PM   #10
chrisb is offline chrisb  Canada
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Gee, that sounds familiar - were the words "time to outgrow those childish things" anywhere in the conversation?
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