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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 10:09 am 
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Joined: July 8th, 2016, 4:34 pm
Posts: 570
If you are rich this driver would probably work fine -

http://www.parts-express.com/jbl-2446h- ... t--294-415

An old audio nut (he built his version of the Klipschorn) I knew in the 1970's though JBL made the best 2 inch horn drivers (to go with their horns with the slant plate lenses).


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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 10:16 am 
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Joined: July 9th, 2016, 7:23 pm
Posts: 30
Location: Fairfax Station, VA
Not a lot of difference between a Tractrix, Exponential or LeCleach 3/4's of the way down the pipe. It's mostly the mouth termination differences. The Kugellwellen also gets good press, but is almost identical to the LeCleach out to the final lip.

I have a spare pair of JBL 2440's, but they still have titaniums in them. When I eventually get around to replacing the aluminum ones in my system with TruExtents, I intend to put them into the 2440s.


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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 10:32 am 
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Joined: July 9th, 2016, 7:23 pm
Posts: 30
Location: Fairfax Station, VA
brombo wrote:
If you are rich this driver would probably work fine -

http://www.parts-express.com/jbl-2446h- ... t--294-415

An old audio nut (he built his version of the Klipschorn) I knew in the 1970's though JBL made the best 2 inch horn drivers (to go with their horns with the slant plate lenses).


The phase plug is good, but you have to realize that there is no throat to speak of in the driver itself. Not a bad thing, necessarily, but there could be discontinuity at the interface to the horn throat if the horn throat walls have an initial angle that is not parallel to the axis of the horn. Titanium, yuck!


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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 10:46 am 
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I think the 2440 or 2441 Al diaphragms will drop right in....

Roscoe

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I can explain it to you, but I can’t understand it for you.


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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 12:34 pm 
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Joined: April 20th, 2014, 5:21 pm
Posts: 233
JBLs are 2" because they initially presented the 375 as an update of the WE594A, same as the D123 was an update of the 728B...yeah, right! They wish!!

The Renkus 2" is pretty good for a now reasonably priced ferrite driver...lives on as the Radian, I suppose. Good for those who like a clean and dry tone. I prefer a clean and juicy tone, myself...


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 Post subject: Re: Hello
PostPosted: August 9th, 2016, 1:02 pm 
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Posts: 233
Also, I would be wary of choosing horns by equation.

I had several tractrix horns and they had little in common. The Edgar salad bowls were like a laser. The klangfilm are very nice off axis and generally more comfortable to listen to.

Aside from tractrix expansion, they share nothing, really.

Materials and constructional details such as throat design and who knows what else play a large role in the subjective performance of horns.

I daresay a horn that might have little audioforum buzz appeal can outperform many that are techno-faves.

This doesn't make choosing any easier, but that's the way it is in my experience.

One of the best tractrix horns I've heard were those fugly original Edgar midrange horns for cone drivers from Audio Amateur. I dumped mine on Gary Gill because I was sick of looking at them, but they did sound fabulous.

Boarding call for Korean Air...gotta go.


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 Post subject: Re: Hello
PostPosted: August 10th, 2016, 8:54 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 1099
Cogito wrote:
Roscoe Primrose wrote:
I think you're missing the point. Exponential horns are a fine thing. The 511 departs from being an exponential horn in the throat area. That's not opinion or hearsay, that's plain measurable geometry. No amount of damping can change that.

Roscoe


That sudden transition in the throat area seems to be a design feature, not a flaw.

Here is the excerpt from Altec literature:

511B/811B:
Exponential expansion and straight throat configuration ensure uniform control of the sound dispersion pattern -- 90 degrees horizontal by 40 degrees vertical -- and exacting reproduction of the middle and high frequencies.

http://alteclansingunofficial.nlenet.net/proloudspeakers/sectoralhorns/511B&811B-Data.pdf


After some reading, there is some misunderstand -- at least on my part -- about 511s.

Altec 511Bs are not exponential horns. They are Radial/Sectorial horns, ie, exponential vertical axis and canonical horizontal axis. No part of the horn is strict circular except for the start of the throat.

The quote above from Altec, "Exponential expansion and straight throat", gave me the impression that throat is straight like a tube which suddenly flares into a canonical horn causing diffraction. If I look at the horn closely (see pics below), the throat quickly becomes a rectangle and slowly flares until the a point where exponential and canonical geometries kick in. The "straight throat" in Altec specs is referring to the vertical walls of the throat, which are supposed to be straight because of the canonical geometry on the horizontal axis.

The flare looks too steep from outside, but it is similar to that of Emilar EH500. Inside of the horn, the transition from throat to mouth is nicely curved.

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The horizontal walls of the throat follow the exponential curve and they condense at the beginning of the mouth to start a new exponential pattern. This also looks to be very similar to the pic of Emilar EH500 (J-ROB, can you post the horizontal axis pic when you get back?)

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Since the throat is the sectoral horns is expanding and there are no sharp edges, I now do not believe that our hypothesis of simple diffraction does not apply here, that is not to say there will be no diffraction in the horns. What ever little diffraction is present in the sectoral horns is inherent part of the geometry.


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 Post subject: Re: Hello
PostPosted: August 10th, 2016, 10:18 pm 
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The situation looks a lot different from the inside of the horn. External measurements are going to be misleading.

The EH500 is actually quite a smooth expansion inside, with a lot of thick metal around it.

One thing that give me cause to worry with the 511 is the extremely rough casting and welds inside the throat of 511s. This can't be good. Seems they got worse over time. These rough spots will give rise to classic sharp-edge diffraction it seems to me. Maybe no big deal for PA but for nearfield hifi?

I should qualify this by mentioning that SOME 511s are much nicer than others. The gold ones that were intended for hifi systems were much more nicely finished than many of the generic black ones, especially late production. But even the gold ones have a very rough texture inside the throat where it should be as smooth as possible.

Aside from the mathematical design, there is always the question of implementation.

I'm in a room in the Silbatone factory with at least 100 horns around me, from 2" mouth to walk-in sized! No 511s or Emilars here to look at however.


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