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Old 10th January 2006, 08:03 AM   #1
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Default BSC for MLTL-207E + tripath ?

I'm currently building a pair of MLTLs to match a tripath Amp-3. The speakers will be Martins MLTLs for the Fostex FE207E that I understands will be a good match for a tripath-based amp. I'll get the cabinets sometime next week (it's good to have a carpenter-brother-in-law with unlimited supply of MDF and tools) and am preparing to assemble them.
I need some help with the dimensioning of the BSC. What value should I use for the LBSC? According to the circuit description I should use a low value to match low damping factor (tubes) and higher to to match higher DF (solid state).
Does anyone know a good match for my tripath-amp?
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Old 10th January 2006, 12:16 PM   #2
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Try a 5 ohm resistor with 1.2mH inductor as approximate starting values. The Tripath have a much lower damping factor than most solid state, and though they sound lovely when only producing small amounts of power, at higher output distortion rises rapidly, so you'll want to go easy on the values to keep efficiency high.

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Old 10th January 2006, 07:30 PM   #3
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If you place the speakers near the back wall, you may find that they require no BSC at all. You'll still want maybe 2 to 3 ohms series resistance. That's what I have in my FE207E (simple vented 45L cabs), nice noninductive resistors, and that is just the ticket.

I've done the Decware-style phase plugs (wrench sockets), and I really liked what they did to the quality of treble.

The other recommendation would be to toe in the speakers so their axes cross in front of the listening position. IMO the 207E sound best slightly off-axis. The overtoeing yields a nice large sweet spot.

I use them with a gainclone -- I had to decrease the feedback resistance because they were too damned loud when I first built them. So I think they will work really well with the tripath. Also, I think Martin's design is great, that's what I would build if I could start all over.

Keep us posted on your progress. Photos?
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Old 11th January 2006, 06:18 AM   #4
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I know this may defeat the purpose of using fullrange drivers, but the top end of the 207E is a bit peaky, so I use tweeters from 4.5k and up. Then I amplify the 207E's and tweeters separately to maximize volume since the Tripath amps don't have too much headroom. Treble is much smoother as a result.
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Old 11th January 2006, 06:55 AM   #5
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A very worthwhile idea. Personally, I'd take the 207s up to around 10Khz to take greater advantage of the wideband capablilities (I did the same with a pair of FF225Ks recently), but whatever works best for you of course. What tweeters do you use BTW?

Best
Scott
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Old 11th January 2006, 08:34 AM   #6
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Quote:
Originally posted by Scottmoose
Try a 5 ohm resistor with 1.2mH inductor as approximate starting values. The Tripath /.../ at higher output distortion rises rapidly, so you'll want to go easy on the values to keep efficiency high.
Thanks, Scott. I'll start off with theese values and tune with the resistor. I'm aware of the tripath-clipping from my t-amp modding so i've moved to 41hz AMP3 that can run on a slightly higher supply voltage to give you a little more output power before clipping.

Quote:
Originally posted by Dumbass
/.../
I've done the Decware-style phase plugs (wrench sockets), and I really liked what they did to the quality of treble.
The other recommendation would be to toe in the speakers so their axes cross in front of the listening position. IMO the 207E sound best slightly off-axis. The overtoeing yields a nice large sweet spot.
/.../
Keep us posted on your progress. Photos?
I plan to let them break in before concidering cutting them up (but the reports on the decware-mods are intresting).
Regarding placement and toeing it will as usual be optimized as well as it can be within the WAF-spot for the speakers...
Sorry no photos so far, since the enclosures are still at my brother-in-law in Finland (I'm in Sweden) waiting for transport.
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Old 11th January 2006, 11:31 AM   #7
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Quote:
Originally posted by JWFokker
/.../ the top end of the 207E is a bit peaky, so I use tweeters from 4.5k and up./.../
Doesn't the BSC in the MLTL take care of that? Or phase-plugs?
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Old 11th January 2006, 12:17 PM   #8
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Quote:
Originally posted by Scottmoose
A very worthwhile idea. Personally, I'd take the 207s up to around 10Khz to take greater advantage of the wideband capablilities (I did the same with a pair of FF225Ks recently), but whatever works best for you of course. What tweeters do you use BTW?

Best
Scott
I ended up with the HiVi RT1C-A "Isodynamic" (ribbon) tweeter. I actually like the RT1L better but the RT1C is 6db more efficient so it was a better match for the 207E.

Quote:
Originally posted by fredricl


Doesn't the BSC in the MLTL take care of that? Or phase-plugs?
I understand the phase-plugs do smooth it out, but I'm unwilling to cut up my drivers to try it. And I can't believe the freq response is better than a good tweeter. That would be too good of an improvement for Fostex to ignore. Some people don't like crossovers at all, but I can live with one.
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