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Posted by Horn Savant on
08-15-2010
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fiogf49gjkf0d Hello
I've always wanted to try an ESL as a horn driver:
So I employed a hi power Koss 3-layer bass module cut from Koss "model 2" spkr.
Polarizing voltage was low on Koss design so it was upped to 3kv w/ custom PS.
Horn is old closet that had a trapdoor to basement (to an old stairway - long removed).
A heavy baffle board replaces the trapdoor. Rear sound is dissipated to basement so there
is no out-of-phase cancellation (and no rear pressure loading of diaphragms)(inf baffle).
Horn has one fold before emerging as corner loading (down to 20hz one hopes)
The sound is very deep with no apparent resonant peak like w/ dynamic drivers.
So I notice good slew-rate performance with detail and absence of the "overhang"
and "ringing" that can smear the sound w/ dynamics - especially those with taut
hi power suspensions.
Next experiment will be with a single diaphragm module (no sandwiched layers) as
I believe this can be problematic
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Posted by Romy the Cat on
08-15-2010
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fiogf49gjkf0d Interestng, I did not near horn load Electrostats. What the profile and what the mouth rate of your horn? What the resonant frequency of Electrostats you have before and after loading? Are you driving the Electrostats direct from plate or via a transformer? What the sensitivity of your ESL panel? Where are you crossover the Electrostats?
Rgs, the Cat
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Posted by Horn Savant on
08-16-2010
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fiogf49gjkf0d Up to the first fold the horn is somewhat conical as seen in post #1 picture.
This picture shows the exit w/ additional angle wall (making for "corner" loading).
This has a greater (uncalculated) flare something like a compound CD horn.
Resonant F unknown but must be above operating point (used below 80hz from
an AV receiver). Resonance sounds above 100hz when you tap a Koss module
(and hear the diaphragm ring). Would be slightly different for each diaphragm element
as it varies with tension and these are old units.
Units are driven from 2 large xformers seen in pix #1 (Koss uses 2 with series secondaries
to achieve center-tapped P/P drive). I have seen the schematic for that Acoustat direct Tube drive
(uses high voltages and big P/P tubes - a bit dangerous like radio transmitter equip)
Sensitivity is still low even with increased Polarizing HV - so much so that I run it with regular LCR
spkrs (and not with the horn spkrs as the matching adj of the AV unit doesn't have enuf span
w/out a booster amp for SW signal)
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Posted by Romy the Cat on
08-17-2010
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fiogf49gjkf0d About the resonance. This was exactly why I asked. The electrostats drivers have very light diaphragm and through react of those diaphragm from a large horn will have much more critical effect then with a driver that would have heavier rand more rigid cone.
It is hard to say what theoretical advantage electrostats would have in bass driver. I do not see any advantages but I do not see anything prohibitive as well. Intuitively I would be happier to see MF electrostats driver loaded into a horn but you use it for bass… It is hard to say. Take care about the resonance and make sure that you horn work properly, regardless of the driver you use….
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Posted by Horn Savant on
08-17-2010
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fiogf49gjkf0d I note English Mfgrs tried low power ribbon Midrange horns in the 50's (Decca, Kelly & Quad also made one!).
These were probably inspired by the hi pwr prewar? Klangfilm ribbon horn (would like to hear one of those!)
But, after Peter Walker moved on to ESL & even experimented with sealed box to eliminate bass cancellation,
he never made the leap to horn ESL.
ESL amateur builder Sanders doesn't like using ESL for bass frequencies. Sanders also tried sealed box
and rejected the idea (one can intuitively sense that this wouldn't work for ESL - unless the "box"
was another room or basement)
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