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Old 3rd March 2012, 02:40 AM   #1
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Default Buschhorn mkII issues

After reading so many good things about the Buschhorn, I built a pair of MKIIs using Fostex FE103En. I got them together yesterday afternoon and they really do disappear. Unfortunately, they sound bad. I mean not just bad, but terrible. Horns (ironically) sound great, but otherwise the closest thing they resemble is the sound of an old transistor radio, my radio alarm clock, speaker in a plastic box, etc.: it's a thin, hollowness with very little low frequency.

I have one side clamped tight to them while I play around with the sound. I've added polyfill damping in the compression chamber (which brought some instruments forward), the upper and lower voids, and added a bit in the throat as recommend by some. I even plugged them in out of phase with very little change. I've tried a variety of amplifiers and the speakers pretty much sound the same. Could this simply be a problem with the clamped seal? They have about 30 hours on them so do the drivers need to break in...a lot? This is my first DIY speaker project and any mods, tips, advice is welcome.
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Old 3rd March 2012, 03:41 AM   #2
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You have 100+ hrs on the driver's yet?

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Old 3rd March 2012, 02:25 PM   #3
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I just started playing them about two days ago and have about 25-30 hours on them. They sound so thin I wonder how much break-in will help; the change will have to be significant to enjoy anything but the most simple music. I'm curious too, if there is something I'm supposed to do to get rid of the hollowness or bring out a bit more low frequency (apart from adjusting tone controls)...Be patient?
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Old 3rd March 2012, 04:18 PM   #4
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I haven't looked at the Mk2 for a while, & certainly not with the 103En, but I have a nasty feeling that what applies to the Mk1 Buschorn also applies to its successor: viz. that (IMO) it's tuned too low for the given bulk / box size, with the result that the useful gain BW tends to be concentrated above ~100Hz. I could be wrong. Hope so. I've got some teaching to do this evening, but if I get chance, I'll take a look at it later & see what it's general behaviour is like / if I can make any suggestions.

Meantime: get some hours on the drivers. Those units were not anticipated by their designers to come on song until several hundred hours had passed (that's coming from a source in Fostex). Make of that what you will, but it should help a bit.

Last edited by Scottmoose; 3rd March 2012 at 04:21 PM.
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Old 3rd March 2012, 04:50 PM   #5
hm is offline hm  Europe
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Default MKIII

Hello,
if i see what they made in MKIII,
you cant read good things,
lin. stroke of 0,6 mm is also not the best,
press chamber to large,
did you saw measurements or impedanz?

my trombone would be a different solution.
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Old 3rd March 2012, 07:38 PM   #6
chrisb is offline chrisb  Canada
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Originally Posted by Scottmoose View Post
I haven't looked at the Mk2 for a while, & certainly not with the 103En, but I have a nasty feeling that what applies to the Mk1 Buschorn also applies to its successor: viz. that (IMO) it's tuned too low for the given bulk / box size, with the result that the useful gain BW tends to be concentrated above ~100Hz. I could be wrong. Hope so. I've got some teaching to do this evening, but if I get chance, I'll take a look at it later & see what it's general behaviour is like / if I can make any suggestions.

Meantime: get some hours on the drivers. Those units were not anticipated by their designers to come on song until several hundred hours had passed (that's coming from a source in Fostex). Make of that what you will, but it should help a bit.

Frankly even though it's smaller and might not model as well. I found the MkI far superior to the MkII - the latter definitely has issues with the driver chamber. When properly corner situated the MkI with FE126 is quite nice.
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Old 4th March 2012, 11:51 PM   #7
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Hey guys. Update: I let them play all weekend and I'm getting more low frequency now. I guess patience is a virtue...I played around a bit with the compression chamber based on what Scottmoose and hm mentioned, reducing the volume by about 2/3. What a change that made. I think I lost some openness (which was spooky) but the sound is now much more forward. Before (and in the one I have left unaltered) it seems as if instruments were buried in the cabinet somewhere and that high, nasal, hollowness has mostly been eliminated. As they break in, I'll cut some nice fitting pieces and continue to tune the CC. Since I put a fair amount of time into these, I'm still open to suggestions about mods to fine tune.

Last edited by fmjunkie; 4th March 2012 at 11:53 PM. Reason: typo
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Old 5th March 2012, 07:29 AM   #8
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Low pass chamber, the room is the compression chamber for a back-horn. I took a look the other night; in principle it's not too bad for what it is & reasonably flexible in terms of tweaking. FWIW, I'd concur in reducing the depth of the filter chamber to ~3.5in - 4in & then lightly damp. The box will be tuned a little higher since that long chamber is likely to be forming part of the horn expansion in practice (probably unintentionally), but it should result in a little more gain & probably kill some resonances without severely affecting the upper corner frequency (providing they're corner loaded, as intended). You might want to try adding a very light layer of damping as indicated in green lower down on this page: Serge's Home Page which should help kill any unwanted midrange that's still passing through the horn.

Last edited by Scottmoose; 5th March 2012 at 07:34 AM.
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Old 5th March 2012, 12:34 PM   #9
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Quote:
Originally Posted by Scottmoose View Post
Low pass chamber, the room is the compression chamber for a back-horn. I took a look the other night; in principle it's not too bad for what it is & reasonably flexible in terms of tweaking. FWIW, I'd concur in reducing the depth of the filter chamber to ~3.5in - 4in & then lightly damp. The box will be tuned a little higher since that long chamber is likely to be forming part of the horn expansion in practice (probably unintentionally), but it should result in a little more gain & probably kill some resonances without severely affecting the upper corner frequency (providing they're corner loaded, as intended). You might want to try adding a very light layer of damping as indicated in green lower down on this page: Serge's Home Page which should help kill any unwanted midrange that's still passing through the horn.
Thanks. I believe the chamber is right around 4" now which smoothed the sound considerably. I'll continue to tweak it. I noticed on Serge's Home Page he used a Notch Filter. Anybody have experiences with these on the B-horn?
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Old 5th March 2012, 03:59 PM   #10
DrBoar is offline DrBoar  Sweden
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The BH is a very small horn so do not expect it to beheave as horn below 100 Hz.Then there is the baffle step f(3) = 115/W(B) (where W(B) is the baffle width in meters) so below 700 Hz the driver has its front radiation going from 1/2 space radiation to full space and a 6 dB loss. In general increasing the lowpass chamber volume increse the low bass but also increase the amplitude of the peaks and "uneveness".

So you have a severly compromised horn more like a resonant quarter wave pipe with some horn features thrown in. It still can sound good but it is a juggling act of getting it right.
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