Robh3606 said:Second plot of the 2435
Rob
The second plot is the JBL PTH1010 waveguide? Certainly a lot better than the first plot, that's for sure. Very good in the absolute sense, particularly if used with a supertweeter (and the higher than 10 kHz region gently rolled off to minimize the standing waves and/or resonances in the 12~15 kHz region).
Is this one of those secret handshake things or something?
I did a search for the JBL PT 1010 on the JBL Professional and came up with nothing. I repeated the search on Google, and on page 2 of the search, came up with a pointer to a discussion on the Audio Heritage forum.
What are the sources for these things, anyway? Please, not Fleabay, or double-secret official-supplier-only sources. Are there special insider-only part numbers for these things? If so, what do they cost in the real world, and where do you get them?
Still baffled by the JBL Professional site. No mention anywhere of different versions of Vertec and consumer horns - is this information available to the broader public? The JBL Professional website only shows the 2447 and 2451 1.5" exit compression drivers - are all the rest are obsolete, only sold into the Japanese high-end market, or available only as replacement parts for complete loudspeakers?
Are there versions of the 2447 or 2451 that use Aquaplas damping on the diaphragm? - It's not mentioned on the PDF's for the products.
Sorry for the peeved tone - but researching these things seems almost like JBL is trying to keep things under wraps, or as intentionally confusing as possible. Maybe their web program is just disorganized in typical big-corporate fashion.
I did a search for the JBL PT 1010 on the JBL Professional and came up with nothing. I repeated the search on Google, and on page 2 of the search, came up with a pointer to a discussion on the Audio Heritage forum.
What are the sources for these things, anyway? Please, not Fleabay, or double-secret official-supplier-only sources. Are there special insider-only part numbers for these things? If so, what do they cost in the real world, and where do you get them?
Still baffled by the JBL Professional site. No mention anywhere of different versions of Vertec and consumer horns - is this information available to the broader public? The JBL Professional website only shows the 2447 and 2451 1.5" exit compression drivers - are all the rest are obsolete, only sold into the Japanese high-end market, or available only as replacement parts for complete loudspeakers?
Are there versions of the 2447 or 2451 that use Aquaplas damping on the diaphragm? - It's not mentioned on the PDF's for the products.
Sorry for the peeved tone - but researching these things seems almost like JBL is trying to keep things under wraps, or as intentionally confusing as possible. Maybe their web program is just disorganized in typical big-corporate fashion.
Here ya go Lynn
JBL parts list
I've got a copy of the parts list including the PT waveguides at home - I'll see if I can track it down. From memory it was somewhere close to the link above.
Found it - P/N 338785, it's in the price list above.
Cheers,
Mike
JBL parts list
I've got a copy of the parts list including the PT waveguides at home - I'll see if I can track it down. From memory it was somewhere close to the link above.
Found it - P/N 338785, it's in the price list above.
Cheers,
Mike
Robh3606 said:
Yes, home listening levels are much lower than prosound, but I don't see how the method of CD compensation - passive or active, attenuation or boost - makes any difference to excursion. For any given listening volume, if the equalization curve and crossovers are same, the power profile the driver sees has to be the same.
Sheldon
Hello Lynn
Best way to find out about something is usually in The Technical Reference Library
http://www.jblpro.com/pages/tech_lib.htm
Vertec
http://www.jblpro.com/vertec1/new_vertec/index.html
PT Waveguide
http://www.jblpro.com/vertec1/new_vertec/index.html
AE Series, where they are used
http://www.jblpro.com/ae/index_B.html
Exploded diagrams for the AE Series to get part numbers
http://www.jblproservice.com/navigation/AE Series.html
Price Lists
http://www.jblproservice.com/navigation/pdf_nav_parts lists.html
So there you have it. Two secret handshakes, a nod and a wink.
All of this stuff is spares only directly from JBL Pro Service. I have never had a issue purchasing parts this way. All you need is the part number which you can easilly get from the Exploded Diagrams. This is how I purchased my waveguides.
None of this is marketed as seperate model or part numbers. The compression drivers off the list that have SL are aquaplas coated.
Rob
Best way to find out about something is usually in The Technical Reference Library
http://www.jblpro.com/pages/tech_lib.htm
Vertec
http://www.jblpro.com/vertec1/new_vertec/index.html
PT Waveguide
http://www.jblpro.com/vertec1/new_vertec/index.html
AE Series, where they are used
http://www.jblpro.com/ae/index_B.html
Exploded diagrams for the AE Series to get part numbers
http://www.jblproservice.com/navigation/AE Series.html
Price Lists
http://www.jblproservice.com/navigation/pdf_nav_parts lists.html
So there you have it. Two secret handshakes, a nod and a wink.
All of this stuff is spares only directly from JBL Pro Service. I have never had a issue purchasing parts this way. All you need is the part number which you can easilly get from the Exploded Diagrams. This is how I purchased my waveguides.
None of this is marketed as seperate model or part numbers. The compression drivers off the list that have SL are aquaplas coated.
Rob
Member
Joined 2003
"but I don't see how the method of CD compensation - passive or active, attenuation or boost - makes any difference to excursion. For any given listening volume, if the equalization curve and crossovers are same, the power profile the driver sees has to be the same."
Hello Sheldon
The power profiles are not the same here's why. When you use passive attenuation for compensation your are attenuating the midband response. Lets say for simplicity you need 10db of compensation and your crossover point is 1K. If you put 1 watt into the speaker system your power into the driver at 1K is 100mw because of the attenuation. At 15K where there is no attenuation the power input is 1 watt. The reason for the reduced excursion is due to the reduced power input in the drivers lower range where most of the diaphragm excursion occurs just like in a dynamic driver.
In an active SR set-ups SPL rules. You don't want to loose efficiency in this application. To flatten out the same driver response you would add +10 of drive at 15k. That means for every watt of power in you have 10 watts at 15K. Between the power distribution of music and the really small excursions at that high a frequency they can safely add the drive level.
The curves are the same but using attenuation it's a negative curve below your 0db reference line and an active curve is above the 0db line. The 0db line with our example speaker would be 100db which is the system sensitivity using a passive crossover.
Rob
Hello Sheldon
The power profiles are not the same here's why. When you use passive attenuation for compensation your are attenuating the midband response. Lets say for simplicity you need 10db of compensation and your crossover point is 1K. If you put 1 watt into the speaker system your power into the driver at 1K is 100mw because of the attenuation. At 15K where there is no attenuation the power input is 1 watt. The reason for the reduced excursion is due to the reduced power input in the drivers lower range where most of the diaphragm excursion occurs just like in a dynamic driver.
In an active SR set-ups SPL rules. You don't want to loose efficiency in this application. To flatten out the same driver response you would add +10 of drive at 15k. That means for every watt of power in you have 10 watts at 15K. Between the power distribution of music and the really small excursions at that high a frequency they can safely add the drive level.
The curves are the same but using attenuation it's a negative curve below your 0db reference line and an active curve is above the 0db line. The 0db line with our example speaker would be 100db which is the system sensitivity using a passive crossover.
Rob
Robh3606 said:"but I don't see how the method of CD compensation - passive or active, attenuation or boost - makes any difference to excursion. For any given listening volume, if the equalization curve and crossovers are same, the power profile the driver sees has to be the same."
Hello Sheldon
The power profiles are not the same here's why. When you use passive attenuation for compensation your are attenuating the midband response. Lets say for simplicity you need 10db of compensation and your crossover point is 1K. If you put 1 watt into the speaker system your power into the driver at 1K is 100mw because of the attenuation. At 15K where there is no attenuation the power input is 1 watt. The reason for the reduced excursion is due to the reduced power input in the drivers lower range where most of the diaphragm excursion occurs just like in a dynamic driver.
In an active SR set-ups SPL rules. You don't want to loose efficiency in this application. To flatten out the same driver response you would add +10 of drive at 15k. That means for every watt of power in you have 10 watts at 15K. Between the power distribution of music and the really small excursions at that high a frequency they can safely add the drive level.
The curves are the same but using attenuation it's a negative curve below your 0db reference line and an active curve is above the 0db line. The 0db line with our example speaker would be 100db which is the system sensitivity using a passive crossover.
Rob
Rob, I'm not talking about power into the speaker system, I'm talking about power to the driver. Sure, if your passive network eats up power in part of the range, you get less to the driver. But if you want a given acoustic output from the driver, at any frequency, it makes no difference to the driver whether it is delivered directly by the amp or through a passive network. You need exactly the same excursion. Yes, it does make a difference to the amp. With a passive network you adjust the output to deliver the high frequency you want, and burn the excess midrange in the network. With active (or passive line level, for that matter), you don't deliver it in the first place.
Sheldon
"But if you want a given acoustic output from the driver, at any frequency, it makes no difference to the driver whether it is delivered directly by the amp or through a passive network. You need exactly the same excursion."
Oh you mean a given, the same SPL, at say 1K you need to same power either way. Your right you would have the same power at the driver terminals.
OK but that's not the point I was making. I didn't say that the acoustic output was the same in both applications. It is clearly not. They get driven much harder used in SR applications and are used under worst case conditions with active CD comp in max SPL situations.
Using a passive network compensation that attenuates the midband is a much more benign enviornment in comparison. It does reduce excursion but the cost is reduced SPL/headroom which in home conditions we can afford to sacrafice.
I was comparing the conditions of use.
Rob
Oh you mean a given, the same SPL, at say 1K you need to same power either way. Your right you would have the same power at the driver terminals.
OK but that's not the point I was making. I didn't say that the acoustic output was the same in both applications. It is clearly not. They get driven much harder used in SR applications and are used under worst case conditions with active CD comp in max SPL situations.
Using a passive network compensation that attenuates the midband is a much more benign enviornment in comparison. It does reduce excursion but the cost is reduced SPL/headroom which in home conditions we can afford to sacrafice.
I was comparing the conditions of use.
Rob
Thanks to Robh3606
Robh3606, thanks for the links, and the parts-list and tech-notes in particular. I didn't know the 2435 and 435Be were so similar - the only difference seems to be the Aquaplas and the larger rear chamber for the 435Be consumer version. Apparently the Aquaplas is readily available from a US vendor under a different name, if I recall the AudioHeritage thread correctly, so it would be possible to convert a JBL 2435 to a 435Be, and save a fair amount of money, especially if the 2435 was bought second-hand from a vendor like Jammin' Jersey.
JBL almost certainly makes a lot more 2435's than 435Be's, and the difference is reflected in the price. Still not exactly cheap at US$765 each, but not as outlandish as the TAD pricing, and I suspect the diaphragm is better than the TAD as well.
The VT1010 waveguide looks a little weird but there's no arguing with the very impressive CSD plot you've posted for the 2435+VT1010 - frankly, the best I've ever seen for any horn system, from any vendor. That's an impulse response in the same league as very good direct-radiators - with the huge advantage of 20+ dB more headroom. I'm not thrilled about what's going on between 12~16 kHz, but I plan to use a supertweeter anyway, and gently roll off the medium-format compression driver with a lowpass network.
Robh3606, if you're still tuned in, I have a question about removing the rear chamber entirely. John Atwood mentioned that this as a favorite mod of his, along with removing the bug-screen. Now I know about the bug-screen removal - I heard it for myself, and the dramatic reduction of grain-and-grit (HF distortion) made it an obvious thing to do. The metal-mesh screen is only there for outdoor use as far as I could tell.
As for removing the rear chamber, OK, I can see the merit of getting rid of the reflection from the back of the rear chamber. The fairly thin felt damping is certainly not going to be 100% absorptive, and removing the rear chamber entirely is the only method to completely remove the reflection from the rear surface of the back chamber. Since this driver is not going to be mounted in a cabinet, LF pressure waves from the woofer are not going to be a problem, and a modest amount of rear-radiation directly from the diaphragm in this application is a plus, not a negative.
But removing the rear chamber has to have an effect on the LF response from the CD+horn, right? Does it all go away, for example? The compliance of the diaphragm must drop, since the mechanical compliance and rear-chamber compliance are in series with each other. This is probably a really dumb question, but that won't stop me from asking.
Robh3606 said:Hello Lynn
Best way to find out about something is usually in The Technical Reference Library
http://www.jblpro.com/pages/tech_lib.htm
Vertec
http://www.jblpro.com/vertec1/new_vertec/index.html
PT Waveguide
http://www.jblpro.com/vertec1/new_vertec/index.html
AE Series, where they are used
http://www.jblpro.com/ae/index_B.html
Exploded diagrams for the AE Series to get part numbers
http://www.jblproservice.com/navigation/AE Series.html
Price Lists
http://www.jblproservice.com/navigation/pdf_nav_parts lists.html
All of this stuff is spares only directly from JBL Pro Service. I have never had a issue purchasing parts this way. All you need is the part number which you can easilly get from the Exploded Diagrams. This is how I purchased my waveguides.
None of this is marketed as seperate model or part numbers. The compression drivers off the list that have SL are aquaplas coated.
Rob
Robh3606, thanks for the links, and the parts-list and tech-notes in particular. I didn't know the 2435 and 435Be were so similar - the only difference seems to be the Aquaplas and the larger rear chamber for the 435Be consumer version. Apparently the Aquaplas is readily available from a US vendor under a different name, if I recall the AudioHeritage thread correctly, so it would be possible to convert a JBL 2435 to a 435Be, and save a fair amount of money, especially if the 2435 was bought second-hand from a vendor like Jammin' Jersey.
JBL almost certainly makes a lot more 2435's than 435Be's, and the difference is reflected in the price. Still not exactly cheap at US$765 each, but not as outlandish as the TAD pricing, and I suspect the diaphragm is better than the TAD as well.
The VT1010 waveguide looks a little weird but there's no arguing with the very impressive CSD plot you've posted for the 2435+VT1010 - frankly, the best I've ever seen for any horn system, from any vendor. That's an impulse response in the same league as very good direct-radiators - with the huge advantage of 20+ dB more headroom. I'm not thrilled about what's going on between 12~16 kHz, but I plan to use a supertweeter anyway, and gently roll off the medium-format compression driver with a lowpass network.
Robh3606, if you're still tuned in, I have a question about removing the rear chamber entirely. John Atwood mentioned that this as a favorite mod of his, along with removing the bug-screen. Now I know about the bug-screen removal - I heard it for myself, and the dramatic reduction of grain-and-grit (HF distortion) made it an obvious thing to do. The metal-mesh screen is only there for outdoor use as far as I could tell.
As for removing the rear chamber, OK, I can see the merit of getting rid of the reflection from the back of the rear chamber. The fairly thin felt damping is certainly not going to be 100% absorptive, and removing the rear chamber entirely is the only method to completely remove the reflection from the rear surface of the back chamber. Since this driver is not going to be mounted in a cabinet, LF pressure waves from the woofer are not going to be a problem, and a modest amount of rear-radiation directly from the diaphragm in this application is a plus, not a negative.
But removing the rear chamber has to have an effect on the LF response from the CD+horn, right? Does it all go away, for example? The compliance of the diaphragm must drop, since the mechanical compliance and rear-chamber compliance are in series with each other. This is probably a really dumb question, but that won't stop me from asking.
Hello John
Attached is a crossection drawing from the reference Lynn posted in his previous post.
Hello Lynn
"if I recall the AudioHeritage thread correctly, so it would be possible to convert a JBL 2435 to a 435Be,"
Yes you should go back and have a look. There were some issues doing this. Just putting it on with a brush is not the same treatment they get at the factory. I had mine modified and the end result was good. That said adding any topical treatment to a driver is risky and you have to weigh for yourself if it's worth the risk. My drivers were purchased second hand at very reasonable prices. If you go into this with new drivers you would be better off just trying to source the 435Be from JBL Consumer.
By the way JBL's prices are just as high as TAD's. The $765 is for the replacement diaphram the driver lists at $1399. Take a look in the Transducer List not the Tranducer Parts List. The Parts List is what current recone kits are available.
Removing the back cap and screen??? The screen is very easy to remove but I am not sure it's a good idea. Many people simply don't realize just how small these drivers are. Because of the size of the driver and no throat the phase plug is less that an 1" from the magnet. I would be concerned about something ferrous potentialy finding it's way into the phase plug.
All you would have to do would be put it down on your work bench. With the shape of the back caps they are always going to rest on the the phase plug side.
To be honest I have not had much thought about removing the back cap. Same concern as with the phase plug a loose screw could ruin your day. I have seen compression drivers used as direct radiators but not with horns and the back cap off.
So you would be going additional ambience for a rear tweeter effect?? You obviously would be out of phase. You would not want any dipole like cancelation or increased excursion that could limit your power handling through your lower crossover point around what 800hz ?? I am not sure exactly what would happen.
"This is probably a really dumb question, but that won't stop me from asking."
LOL are you kidding you should see some of mine. Your not even a contendor.
Rob
Attached is a crossection drawing from the reference Lynn posted in his previous post.
Hello Lynn
"if I recall the AudioHeritage thread correctly, so it would be possible to convert a JBL 2435 to a 435Be,"
Yes you should go back and have a look. There were some issues doing this. Just putting it on with a brush is not the same treatment they get at the factory. I had mine modified and the end result was good. That said adding any topical treatment to a driver is risky and you have to weigh for yourself if it's worth the risk. My drivers were purchased second hand at very reasonable prices. If you go into this with new drivers you would be better off just trying to source the 435Be from JBL Consumer.
By the way JBL's prices are just as high as TAD's. The $765 is for the replacement diaphram the driver lists at $1399. Take a look in the Transducer List not the Tranducer Parts List. The Parts List is what current recone kits are available.
Removing the back cap and screen??? The screen is very easy to remove but I am not sure it's a good idea. Many people simply don't realize just how small these drivers are. Because of the size of the driver and no throat the phase plug is less that an 1" from the magnet. I would be concerned about something ferrous potentialy finding it's way into the phase plug.
All you would have to do would be put it down on your work bench. With the shape of the back caps they are always going to rest on the the phase plug side.
To be honest I have not had much thought about removing the back cap. Same concern as with the phase plug a loose screw could ruin your day. I have seen compression drivers used as direct radiators but not with horns and the back cap off.
So you would be going additional ambience for a rear tweeter effect?? You obviously would be out of phase. You would not want any dipole like cancelation or increased excursion that could limit your power handling through your lower crossover point around what 800hz ?? I am not sure exactly what would happen.
"This is probably a really dumb question, but that won't stop me from asking."
LOL are you kidding you should see some of mine. Your not even a contendor.
Rob
Attachments
Robh3606 said:
By the way JBL's prices are just as high as TAD's. The $765 is for the replacement diaphram the driver lists at $1399. Take a look in the Transducer List not the Tranducer Parts List. The Parts List is what current recone kits are available.
...
To be honest I have not had much thought about removing the back cap. Same concern as with the phase plug a loose screw could ruin your day. I have seen compression drivers used as direct radiators but not with horns and the back cap off.
So you would be going additional ambience for a rear tweeter effect?? You obviously would be out of phase. You would not want any dipole like cancelation or increased excursion that could limit your power handling through your lower crossover point around what 800hz ?? I am not sure exactly what would happen.
Rob
$1399 for either the 2435 or 435Be. Urk. That's starting to get into real money. The Great Plains Audio remake of the Altec 290 is looking more appealing the more I think about it, particularly since I'm content with a 800 Hz to 7 kHz bandwidth. Plus, I've really enjoyed the vivid tonality of other phenolic diaphragm drivers I've heard, while I've had rather mixed feelings about the HF quality of the large-format TAD systems. (I like the bass and midbass from the Alnico woofers, the HF - not so much.)
As for bug-screen removal, I'm not planning on using the compression driver in a wood-shop or anywhere metal shavings might be lying around - wouldn't be too healthy for my open-chassis tube amps with 550V B+ voltages, for one thing. I've heard the before-and-after and was pretty surprised at the improvement - way less grain-n-grit, more effortless dynamics, and a certain "obscured" quality went away. Efficiency went up about 1 dB, as I recall. All consistent with eliminating velocity effects around the tiny dimensions of the screen.
As for rear-chamber removal, although I dislike small chambers filled with felt on principle, the whole business of detuning the compression driver and leaving the diaphragm open to disaster if it is accidently touched makes it lose a certain amount of appeal. Kind of like those "nude" moving-coil cartridges that cost $5500 - just looking at one makes me a little nervous. The same feeling as being asked to pick up a friend's Leica or drive their Ferrari - umm, no thanks, not right now, not my thing, y'know.
Just to stir the pot a little, I've made a new posting on the Clarisonus blog run by John Atwood. I expect many readers will disagree with it.
With all due respect, seriously, prices are, have been, & always will be extremely high for the very best high-end products, the subject of this thread.
Decades ago, when I lusted after the then-excellent ADS/Braun commercial systems & JBL-Altec raw drivers, the prices were probably, adjusted for inflation, even higher than the ones quoted a few posts above this.
Decades ago, when I lusted after the then-excellent ADS/Braun commercial systems & JBL-Altec raw drivers, the prices were probably, adjusted for inflation, even higher than the ones quoted a few posts above this.
