Dual triode,
Can you post pics of the newest pt waveguide ? Especialy slightly off axis ? Is it quite flat ? It looks like not much break from horn wall to baffle lip.
Audioheritage mentioned older pt, it can load easily to below 1.5khz Some mention snout in compression driver differences in 2431 and 2432, maybe 2431 work better with older while 2432 works better with newer pt 1010hf. 2432H- any data, measurements, or comparisons to 2431H?
I'm thinking 2431h (not too expensive new) with boost and 14k notch.
2432h looks smewhat hazy past 5khz, but 1/2 price of a new 2431h. Just purchased a pair of JBL 4722n speakers. - Page 203 - AVS Forum | Home Theater Discussions And Reviews
Can you post pics of the newest pt waveguide ? Especialy slightly off axis ? Is it quite flat ? It looks like not much break from horn wall to baffle lip.
Audioheritage mentioned older pt, it can load easily to below 1.5khz Some mention snout in compression driver differences in 2431 and 2432, maybe 2431 work better with older while 2432 works better with newer pt 1010hf. 2432H- any data, measurements, or comparisons to 2431H?
I'm thinking 2431h (not too expensive new) with boost and 14k notch.
2432h looks smewhat hazy past 5khz, but 1/2 price of a new 2431h. Just purchased a pair of JBL 4722n speakers. - Page 203 - AVS Forum | Home Theater Discussions And Reviews
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In the early days I did not do measurements above 10k because I did not think it so important and it added a lot of computer load. Later I went to 20k, but, to me, 10-20k is just not very important. In audiology, no one ever tests above 8 kHz because it is deemed "insignificant".
Earl,
Correct me if I am wrong, but when the throat is larger than 1 wavelength the horn / waveguide starts to have less affect on the wave front. For a 1" exit driver, that would happen on the order of 12 kHz. It would take a 1/2" driver to maintain pattern control above 20 kHz. At that point, it isn't worth the tradeoffs for existing drivers, which would be a 3 kHz LF crossover for the DE 5.
Correct me if I am wrong, but when the throat is larger than 1 wavelength the horn / waveguide starts to have less affect on the wave front. For a 1" exit driver, that would happen on the order of 12 kHz. It would take a 1/2" driver to maintain pattern control above 20 kHz. At that point, it isn't worth the tradeoffs for existing drivers, which would be a 3 kHz LF crossover for the DE 5.
Hello,
Okay 10-20K is not so critical, apparently doing a lot of stuff in the 1 ½ inch throat is not so critical to the listening experience either. Take a look at the M2 spins, Constant Dispersion takes a hike above 8-10K here too.
The snout of the JBL 2451 is short compared to others including the 2450. The shortening of the driver snout happened with the transition from 2 inch to 1 ½ inch throats, “distortion reduction” and the shift away the older 2 inch bi-radial horns.
Over on the other site other people have placed a ½ inch spacer between the JBL 2451 driver and the PT waveguides and smoothed the frequency response curves.
The PT H1010HF-1 bolt circle does not fit the bolt circle of the JBL 2351. The flange just fits inside the JBL 2451 bolt circle. You can see in the pic that nuts and washers sandwich the waveguide to the driver.
I do not teach (building trades stuff) next term, there will be more time to test some of these driver and horn combinations/variations.
Thanks DT
Okay 10-20K is not so critical, apparently doing a lot of stuff in the 1 ½ inch throat is not so critical to the listening experience either. Take a look at the M2 spins, Constant Dispersion takes a hike above 8-10K here too.
The snout of the JBL 2451 is short compared to others including the 2450. The shortening of the driver snout happened with the transition from 2 inch to 1 ½ inch throats, “distortion reduction” and the shift away the older 2 inch bi-radial horns.
Over on the other site other people have placed a ½ inch spacer between the JBL 2451 driver and the PT waveguides and smoothed the frequency response curves.
The PT H1010HF-1 bolt circle does not fit the bolt circle of the JBL 2351. The flange just fits inside the JBL 2451 bolt circle. You can see in the pic that nuts and washers sandwich the waveguide to the driver.
I do not teach (building trades stuff) next term, there will be more time to test some of these driver and horn combinations/variations.
Thanks DT
Attachments
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I got interested in this after I acquired some of their old, long snout drivers:
Vol.1, No.21 - JBL’s New Optimized Aperture Horns and Low Distortion Drivers
"When the JBL 375 compression driver was designed during the fifties, it was based on the exit geometry of the original Western Electric 594 driver.
Subsequent variations, such as the JBL 2441, 2445, and 2450 family all maintained the original exit geometry and were designed to work with four decades of horn hardware with 50 mm (2 in) throat diameter."
Subsequent variations, such as the JBL 2441, 2445, and 2450 family all maintained the original exit geometry and were designed to work with four decades of horn hardware with 50 mm (2 in) throat diameter."
...which means my 2445 drivers (made in the 80's) were updated copies of a 1930's driver. Their slowly flaring exit geometry is a great match for the big old Western Electric horns, or the Inlow horn (which is 90cm long) - and not a great match for most modern (short) horns.
Thus, the "four decades of horn hardware" bit is interesting:
The JBL 375 was originally mated to an adapter + fairly big radial horn (2350). Their combined depth was about 60cm. OK.
By the 80's, JBL was mating these drivers with much shorter horns, like the 2380 (only 23cm deep). That's a big mismatch between the flare rate built into the driver's snout, and the flare rate of the horn.
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That is not true, the waveguide always has an effect and in the case that you state (1") the waveguide would "pull-out" the polar pattern when compared to a 1" piston. But I wouldn't worry too much about creating serious pattern control above 10 kHz. Drive phase plug problems are probably more of a concern above 10 kHz than the waveguide.
I don't know about Earl but it looks like a copy of the old JBL 4660 to me. Based on the 2346 horn by DB Keele. Link http://www.jblpro.com/pub/obsolete/4660.pdf has the patent number.
A look at the patent should answer your questions.
Best wishes
David
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Hello Turk
This should help right off the DB Keele site.
http://www.xlrtechs.com/dbkeele.com...rint) - Horn Covers Flat Rectangular Area.pdf
Rob
This should help right off the DB Keele site.
http://www.xlrtechs.com/dbkeele.com...rint) - Horn Covers Flat Rectangular Area.pdf
Rob
These complex axial rotation patterns are very easy to do in a waveguide. The formula just now becomes a function of Psi the angle around the device. Then Theta(Psi) is just substituted for each desired Theta as Psi goes around the device. The directivity can then be set for any Psi desired. In theory this specification could be very complex, although sharp changes in Theta(Psi) should be avoided.
Hello All,
For optimized controlled dispersion we want to crossover from the woofer to the CD waveguide as low as possible. The GedLee approach is to crossover in the neighborhood of 600Hz, any lower the cost starts to increase rapidly. Also from my vantage the size of the waveguide begins to fill my “small space”.
Many of the smaller waveguides posted here crossover in the 1.5 to 2K range. For example the PT H1010HF-1 is 12 inches square and fits into my interior design plans much better.
Keeping an eye on directivity, looking at the overall dispersion of the speaker including the overlapping desperation patterns of the individual drivers at the crossover frequency, even with an optimized crossover there will be lobing or narrowing of the vertical directivity. The extent of the lobing will depend on the crossover frequency and the distance between the driver centers. Look at the attached figure taken from RaneNote 160.
Linkwitz-Riley Crossovers: A Primer
In my “small space”, sitting in the sweet spot how will the lobing at the crossover frequency effect sound perception? Or will it even have a perceptible effect?
Thank You DT
For optimized controlled dispersion we want to crossover from the woofer to the CD waveguide as low as possible. The GedLee approach is to crossover in the neighborhood of 600Hz, any lower the cost starts to increase rapidly. Also from my vantage the size of the waveguide begins to fill my “small space”.
Many of the smaller waveguides posted here crossover in the 1.5 to 2K range. For example the PT H1010HF-1 is 12 inches square and fits into my interior design plans much better.
Keeping an eye on directivity, looking at the overall dispersion of the speaker including the overlapping desperation patterns of the individual drivers at the crossover frequency, even with an optimized crossover there will be lobing or narrowing of the vertical directivity. The extent of the lobing will depend on the crossover frequency and the distance between the driver centers. Look at the attached figure taken from RaneNote 160.
Linkwitz-Riley Crossovers: A Primer
In my “small space”, sitting in the sweet spot how will the lobing at the crossover frequency effect sound perception? Or will it even have a perceptible effect?
Thank You DT
Attachments
This vertical lobing is a necessary evil. It would of course be better not to have it, but the tradeoffs in getting rid of it are not worth it IMO. The lobes happen over a fairly narrow range of frequencies and drop the power response a bit, but I can't say that I have ever noticed them as a significantly bad effect.
Its certainly a reason that I try and minimize the number of crossovers as each one will have this problem.
It would be a very hard thing to test!
Its certainly a reason that I try and minimize the number of crossovers as each one will have this problem.
It would be a very hard thing to test!
