Soory duke... you missing nothing; I wasn't correct... but anyway i'd use a phenolic
First trials of active horn speaker
- Thread starter morricab
- Start date
The measured frequency response of a compression driver is highly dependent on the horn used. The most valuable plot would be the plane-wave-tube response, which reveals the shape of the power response curve, but almost nobody provides that. Since I prefer constant-directivity horns (assuming they don't rely on diffraction), I have yet to use a horn/driver combination that did not need a fair amount of equalization.
Imo, at the risk of over-generalizing, between polymer and aluminum and titanium, it's a juggling of tradeoffs. I can see arguments for each of them, and there are notable exceptions as well. For instance, the Celestion Axiperiodic Axi2050 looks like an exception, and I think the new Faital HF1440 is similar. These designs have the voice coil positioned exactly where it needs to be on the diaphragm to cancel out breakup modes, or at least some of them, so theoretically they should have really good clarity.
Imo the Radian PB475Be is a fantastic driver. I have used it often. However as with any horn/driver combination, the junction of compression driver to horn is critical - you want the exit angle of the compression driver to match the entry angle of the horn. And if you have to err, it's best to err on the side of the horn's entry angle being wider. Eyeballing that Iwata horn, I would expect its entry angle to be fairly narrow. Fortunately the PB475Be has a rather narrow exit angle, 13 degrees (6.5 degrees on either side).
I have also owned other Radian Beryllium diaphragm compression drivers and ime they are superb.
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I didn't see anything about the Iwata horn in there, but lots of great information. One can see that advanced horn design is a juggling of tradeoffs, informed by the designer's priorities.
... but anyway i'd use a phenolic
Who's making them today, aside from Selenium and PRV?
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This music, while pleasing to listen to, doesn’t tell much other thsn timing is pretty good.
The original Iwata is another type of exponential horn like Tractrix etc. This Horns Iwata is a derivative of that incorporating JMLC principles with regard to mouth termination.
Jean-Michel did many analysis of different horn design... this is his conclusion of designing horns.
To find horn drivers with phenolic diaphragma is quite a search for pellets. You must find the daiaphragmas and modify a driver or look for vintage stuff like the RCA-MI series.
I happen to be a fan of one of the horn designs Jean-Michel covered, the Oblate Spheroid, and it was nice to see it included. Unfortunately imo its depicted modelled response has unrealistic ripples because the model omitted the round-over at the mouth. Give it a Le Cleac'h-class roundover and it will have Le Cleac'h-class smoothness.
That's what I suspected. I'll have to leave the phenolics to the vintage horn and hard-core DIY guys.
Also I'm under the impression that a large-format (1.4" throat or larger) phenolic would need a separate tweeter to cover the top octave or so... is this correct?
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Hello Duke
Yes you certainly would need a tweeter above it case in point 2470 and especially 2480 2" large format. Drop off at 9K with 1" and 5K 2"
http://www.lansingheritage.org/html/jbl/specs/pro-comp/pro-comp.htm
Yes, that is why I went for a driver that can go low enough to be interesting and still get up close to 20khz.
beryllium drivers like Radian and TAD can go from 500 - 700 to 18k. Some would argue that you need tweeter or 1 inch compression driver anyway to avoid breakup modes.
Hello Bonzo
Quite the opposite. The Be are about as clean as you can get looking at a waterfall plot. You would add more issues if the tweeter wasn't Be as well.
Rob
Hello Bonzo
Quite the opposite. The Be are about as clean as you can get looking at a waterfall plot. You would add more issues if the tweeter wasn't Be as well.
Rob
Yes the 1 inch compression driver you add as tweeter would have to be Be. Like tad 2001 on 4001 or Radian 475Be on 950pb Be
My experience has been that the primary reason for adding a tweeter to large-format TAD or Radian Beryllium compression drivers is to get a bit more top-end energy and/or a bit better top-end dispersion. Imo the LACK of breakup modes in the top octave actually REDUCES the SPL of big Beryllium compression drivers in that region, as compared with many other compression drivers. And ime even the 1" throat Berylliums aren't terribly loud in their top octave, presumably for the same reason. (This is evident when comparing a Beryllium Radian with its Aluminum counterpart.)
And there is an argument to be made for having a single horn cover the region from the crossover point on up, from the standpoint of preserving the phase relationships in the overtones if nothing else. In other words, imo there is a valid argument for the path Morricab has been traveling.
I have heard two ways of TAD 4003 and of 2001, and I have heard both 4003 and 4001 crossed over to compression driver /dedicated tweeter. And in universum he crosses Radian.950 to 475. I like all approaches, don't really have a choice. The person who has the best Altec I heard prefers no tweeter.
I have found that the difference is not so much due to 16k or 27k or the 40k of ET 703. Some drivers are more nuanced in the violin range, like TAD and Radian and AER over the Altec, and that is where my choice preference for the highs goes, rather than just an increase in frequency
Agreed. Ime the execution matters more than the underlying philosophy; in other words a designer cannot take comfort in the belief that his way is the right way (which is what we all believe, n'est-ce pas?); he STILL has to get right every little thing that matters.
Yup! And in my experience a nuanced top end enables other desirable attributes.
I like a gently-downward-sloping response curve. But ime this sort of curve only works well when the top end is sufficiently nuanced; that is, when you can hear all the little inner details without the top end being loud. If the top end is not articulate then the speaker sounds boring; but if you make the top end louder so that it IS articulate then it's not as rich and warm and inviting and long-term relaxing. So imo an articulate top end is critical to letting you get away with using what I think is the ideal voicing.
Exactly, and I find that articulate voicing, and given we both like electrostats (i think it was you once gave away acoustats free to whoever could pick them up, long before you joined this forum, and I hated being so far away) that is what I see in the beryllium horn drivers. The nuance, the decay, and the staging is similar
I like his designs as well but have not so many experience with them... so many horns / drivers and so few time...
Yep, you're adoption is correct. But then I prefer more a 2" driver because in lower frequencies it has more authority.
A friend of mine has a quiet large collection of those old drivers and horns .... another good combination: old JBL drivers with the Klangfilm midrange horns - ok, not a JMMLC-design but very interesting
As well I prefer activating the system, Low-Level XO or active XO because of more variance choosing the matching amplifiers.
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