Knightcrawler,
You're talking apples and oranges and throwing a different driver into the discussion. Of course high excursion is possible, just not in combination with all the other parameters as DJK explained previously. No one is claiming that JBL is fudging the numbers. More than likely some dingbat just entered an Xmech number as the Xmax, and with pro drivers that difference is huge. The idea that you guys are just blindly accepting a number as fact despite very convincing evidence to the contrary, is beyond me.
DJK was kind enough to step in and share some valuable insight into driver operation and how some of the different parameters interact with each other. If these limitations didn't exist, then 20hz-20khz 100db/w/m 1000w pmax drivers would exist and our DIYspeakers hobbies would be limited to artistry. We should be thanking DJK for sharing and teaching those of us who want to learn instead of arguing based on a number in an obscure listing already proven to contain another gross typographical error. My money is on an Xmax of under +/- 11mm, with the most likely figure being 8mm.
You're talking apples and oranges and throwing a different driver into the discussion. Of course high excursion is possible, just not in combination with all the other parameters as DJK explained previously. No one is claiming that JBL is fudging the numbers. More than likely some dingbat just entered an Xmech number as the Xmax, and with pro drivers that difference is huge. The idea that you guys are just blindly accepting a number as fact despite very convincing evidence to the contrary, is beyond me.
DJK was kind enough to step in and share some valuable insight into driver operation and how some of the different parameters interact with each other. If these limitations didn't exist, then 20hz-20khz 100db/w/m 1000w pmax drivers would exist and our DIYspeakers hobbies would be limited to artistry. We should be thanking DJK for sharing and teaching those of us who want to learn instead of arguing based on a number in an obscure listing already proven to contain another gross typographical error. My money is on an Xmax of under +/- 11mm, with the most likely figure being 8mm.
johninCR said:
What would be the point in building a Subwoofer with the Ultra long throw won't bottom out at 89mm peak to peak suspension and then only have a 8mm Xmax ?
Seems like it would be a waste of time.
My money is on the 23mm xmax being dead on because JBL car audio just released a new model of it's DD model. The old one was 20mm so the new one having 23mm is a small improvement.
I'll help you out since you can't seem to read, the one with 3-1/2" peak-to-peak (mechanical damage limit) is NOT the 2268 under discussion, but rather the 2269(much bigger magnet, 4" coils, even less efficiency for longer travel, etc).
FWIW, i have both the 4719A cabinets (dual 2241) and srx728s (dual 2268) and the 2268 cabs blow them away with the same power applied. more output, more punchy, and just sound damn great!
I don't think we've discussed the 2241. 20+ years ago when it was designed it wasn't half bad. Of course it only has 5.475mm of coil overhang, not much by today's standards.
JBL still hasn't come through with any gap height and coil length measurements on the 2268, so we really don't know what it can really do. It would seem to be in the range of 8mm~11mm based on analysis of other similar JBL drivers with the new dual gap design. Of course 8mm vs the 5.475mm of the older 2241 would mean over 3dB more maximum output.
While the 2268 is actually less efficient than the 2241, at full power it has less power compression due to the newer design, and that is enough to account for what you peceive.
If you run both below clipping with an electronic crossover, and EQ for identical response, you will not notice much of a difference at lower volume levels. If you just A-B side-by-side and use a full range signal, the 2268 will seem to have a lot more 'punch' due to the 10dB peak in its response.
A system can be just pounding, and if you mute the mid-bass all the 'punch' will just seem to vanish.
JBL still hasn't come through with any gap height and coil length measurements on the 2268, so we really don't know what it can really do. It would seem to be in the range of 8mm~11mm based on analysis of other similar JBL drivers with the new dual gap design. Of course 8mm vs the 5.475mm of the older 2241 would mean over 3dB more maximum output.
While the 2268 is actually less efficient than the 2241, at full power it has less power compression due to the newer design, and that is enough to account for what you peceive.
If you run both below clipping with an electronic crossover, and EQ for identical response, you will not notice much of a difference at lower volume levels. If you just A-B side-by-side and use a full range signal, the 2268 will seem to have a lot more 'punch' due to the 10dB peak in its response.
A system can be just pounding, and if you mute the mid-bass all the 'punch' will just seem to vanish.
Let's be perfectly clear here. It's you , JohninCR and Rademakers who don't know what it can do.
We know that with 23mm of xmax, it can do plenty. Once again, your imagination/speculation doesn't change what JBL says.
BTW, are you sure they didn't reply. Or did you not like what their reply was LOL?
They have replied to all of my requests within days.
cheers,
AJ
Dear Dennis,
in post 35, you wrote:
QUOTE]For $120 I can have a driver compliment that in the same 8 cu ft box tuned to 31hz that will be about 1dB more efficient, and have about 2.5dB more output based on x-max limited displacement. The composite driver is actually a pair of 9.11mm x-max 15s mounted push-pull in a plenum that will fit over an opening for an 18" woofer.[/QUOTE]
Could you please provide a conceptual drawing of the mechanical arrangement, provided, of couse, that my request is not asking for a proprietary information.
Thank you,
M
in post 35, you wrote:
QUOTE]For $120 I can have a driver compliment that in the same 8 cu ft box tuned to 31hz that will be about 1dB more efficient, and have about 2.5dB more output based on x-max limited displacement. The composite driver is actually a pair of 9.11mm x-max 15s mounted push-pull in a plenum that will fit over an opening for an 18" woofer.[/QUOTE]
Could you please provide a conceptual drawing of the mechanical arrangement, provided, of couse, that my request is not asking for a proprietary information.
Thank you,
M
Why fight???? Wait for JBL's answer or contact them again and say you need the specs for a project you're working on. They are usually very helpful.
Ron
Ron
If it is a typo, it will be repeated there. It would be a good idea to have JBL do the research.
Ron
Ron
things JBL - may get more information here-
http://www.audioheritage.org/vbulletin
not likely, post and find out!
http://www.audioheritage.org/vbulletin
not likely, post and find out!
djk,
We may very well end up eating some crow on this one. In the LF cab descriptions where JBL uses these drivers, it says they use the Differential Drive. I have that on my JBL W15gti 15"er, and it consists of 2 VCs wound adjacent on the former and two magnetic gaps. The polarities are opposite, so once Xmax is reached the second coil operates as an electromagnetic brake helping prevent overexcursion.
It makes a lot of sense that this woofer will have significantly higher excursion than a typical pro woofer, however, the setup does increase the chance of a simple error in Xmax. For my GTI, the total VC length is 2.6" and gap height is 1", and JBL lists the Xmax at .80" http://manuals.harman.com/JBL/CAR/Boxes and Parameters/W15GTi_rev_f.pdf I believe the actual Xmax depends on the orientation of the gaps. JBL designed my driver for SPL competition, so it's 20mm Xmax make sense but 23mm Xmax on an 18" pro driver doesn't sound very durable.
We may very well end up eating some crow on this one. In the LF cab descriptions where JBL uses these drivers, it says they use the Differential Drive. I have that on my JBL W15gti 15"er, and it consists of 2 VCs wound adjacent on the former and two magnetic gaps. The polarities are opposite, so once Xmax is reached the second coil operates as an electromagnetic brake helping prevent overexcursion.
It makes a lot of sense that this woofer will have significantly higher excursion than a typical pro woofer, however, the setup does increase the chance of a simple error in Xmax. For my GTI, the total VC length is 2.6" and gap height is 1", and JBL lists the Xmax at .80" http://manuals.harman.com/JBL/CAR/Boxes and Parameters/W15GTi_rev_f.pdf I believe the actual Xmax depends on the orientation of the gaps. JBL designed my driver for SPL competition, so it's 20mm Xmax make sense but 23mm Xmax on an 18" pro driver doesn't sound very durable.
Perhaps lost in all of this is what a superb driver the 2268H is. Not only does it sweep huge volumes of air with it's 23mm of xmax and large Sd (not unusual for some car subwoofers), but it does so with very low levels of distortion (pg6)http://www.jblpro.com/pub/technote/JBL_TN 1-33 rev3.pdf and highish effeciency (something foreign to car subs).
It also does so at ($435) half the price of the Aura (itself a fabulous unit). If the 2269H is anywhere near that price, it may be hard to resist.
Of course, if space/weight isn't a premium, perhaps a dozen of these may do LOL: http://www.mach5audio.com/product_i...id=38&osCsid=f8ce1391a1fe5655bab5fda3922ce62a
I understand there are those who fear and loathe eq, but those would be some "cheap thrills" dipole subs if I ever saw some.
cheers,
AJ
It also does so at ($435) half the price of the Aura (itself a fabulous unit). If the 2269H is anywhere near that price, it may be hard to resist.
Of course, if space/weight isn't a premium, perhaps a dozen of these may do LOL: http://www.mach5audio.com/product_i...id=38&osCsid=f8ce1391a1fe5655bab5fda3922ce62a
I understand there are those who fear and loathe eq, but those would be some "cheap thrills" dipole subs if I ever saw some.
cheers,
AJ
"We may very well end up eating some crow on this one. "
We don't have to. The spec sheet from JBL shows it has a mechanical limit of 23mm, not an x-max of 23mm.
The W15gti woofer is a totally different animal, as I explained before. It does have 20mm X-max, the 2268 isn't even close to that. Because of the much higher efficiency it can't be.
The spec sheet for the 2262 shows two 0.7" coils with a gap of 0.55" between them, for a total one-way x-max of 8mm at 10%THD.
The spec sheet for the 2268 shows two 0.8" coils with a gap of 0.5" between them, for an estimated one-way x-max of 10mm~11mm.
No number is given on the five page data sheet for x-max, but it may be estimated from the other drivers in the series with the same 3" dual differential drive system. The confusion came from the 23mm number listed on this data sheet, which is clearly marked "Xmax, damage 23mm peak before spider bottoms on gap sleeve".
The flux density vs position chart is very interesting. It shows that there is virtually no coil overhang above or below the gaps, the overhang is between the two gaps. Almost as soon as the coil starts to move, fewer turns are in the gap. The flux drops considerably at about 6mm, and totally drops off a cliff at 12mm.
So we were right, and the others just don't have a feel for what is correct, and what is an obvious error.
Everet Watts at JBL wasn't of much help, he is overworked. The spec sheets had the name of Alex Salvatti (design engineer) on them.
Sorry, I don't have a scanner, but if anyone wants a photo-copy they can send me a self-addressed stamped envelope and I will be more than happy to copy the data sheets and drop them in the mail. If you want both sheets (ten pages) it will probably take two stamps.
We don't have to. The spec sheet from JBL shows it has a mechanical limit of 23mm, not an x-max of 23mm.
The W15gti woofer is a totally different animal, as I explained before. It does have 20mm X-max, the 2268 isn't even close to that. Because of the much higher efficiency it can't be.
The spec sheet for the 2262 shows two 0.7" coils with a gap of 0.55" between them, for a total one-way x-max of 8mm at 10%THD.
The spec sheet for the 2268 shows two 0.8" coils with a gap of 0.5" between them, for an estimated one-way x-max of 10mm~11mm.
No number is given on the five page data sheet for x-max, but it may be estimated from the other drivers in the series with the same 3" dual differential drive system. The confusion came from the 23mm number listed on this data sheet, which is clearly marked "Xmax, damage 23mm peak before spider bottoms on gap sleeve".
The flux density vs position chart is very interesting. It shows that there is virtually no coil overhang above or below the gaps, the overhang is between the two gaps. Almost as soon as the coil starts to move, fewer turns are in the gap. The flux drops considerably at about 6mm, and totally drops off a cliff at 12mm.
So we were right, and the others just don't have a feel for what is correct, and what is an obvious error.
Everet Watts at JBL wasn't of much help, he is overworked. The spec sheets had the name of Alex Salvatti (design engineer) on them.
Sorry, I don't have a scanner, but if anyone wants a photo-copy they can send me a self-addressed stamped envelope and I will be more than happy to copy the data sheets and drop them in the mail. If you want both sheets (ten pages) it will probably take two stamps.
DJK,
I should have known to stick with my gut feeling without backing off. I'm glad you stuck it out to the end. People like yourself are a small minority and often just stop sharing rather than go through the hassle. Then those of us who are here to learn lose out. Thank you.
It sure would be nice if high excursion and high sensitivity could go hand in hand. Imagine the speakers we'd have!
Can you speculate on the design some more, especially wrt the point you brought up about the flux density vs position? It sounds almost like one coil is pushing and the other pulling, otherwise the bigger the excursion the weaker the motor....why? How should that impact the cab design?
I should have known to stick with my gut feeling without backing off. I'm glad you stuck it out to the end. People like yourself are a small minority and often just stop sharing rather than go through the hassle. Then those of us who are here to learn lose out. Thank you.
It sure would be nice if high excursion and high sensitivity could go hand in hand. Imagine the speakers we'd have!
Can you speculate on the design some more, especially wrt the point you brought up about the flux density vs position? It sounds almost like one coil is pushing and the other pulling, otherwise the bigger the excursion the weaker the motor....why? How should that impact the cab design?
Xciterking said:AJ: Click here
http://www.performanceaudio.com/index.shtml
Call the 800 #, ask for Zack. Tell him, Kristopher King from Sacramento hooked you up. If you have any problems let me know. They were $339 for each JBL 2268HPL. I wanted your advice on which speaker; (if you had a choice) would you buy. The 2268's or the Eighteen Sound LW1400's. You know what cabs I will be using. The JBL 2241G's work OK for my band but if I start playing hp hop on the breaks things go wrong. The input levels from the original recordings are all out of whack. Some reasonable, others stupid. Hence, if I walk away from the rig, or don't pay real close attention, ect. In a heart beat a song will come on and pop the 2241G's. I need just a little more strength. Anyway that’s what I think. Might not be so. Anyhow, if you know something about the LW1400's or can recommend another speaker please respond, 1400's will be here 6/13/06. I could send them back and get the 2268's if you think that’s a better choice. I ran sound for a club where I installed four Bag Ends, I used two QSC 3402's in stereo and they were very strong. Don't want to pack more stuff. Thanks for your reply. Kris
Hi Kris,
I'm glad you're happy with the drivers that you ended up with. I was basing my experience with the 2268HPL's from personal experience, not on data sheets. I have replaced many 2241G's in the SR4718X's with the 2268HPL, and have been extremely happy with the results. You have to remove the center PVC post, but no big deal. The boxes wind up cleaner sounding with more low end extension than with the 2241G. I never really liked this box with the 2241G though. They always seemed to run out of punch at 4 ohms. Just adding the 8 ohm 2241H makes them sound better.
As for the 23mm excursion, it does seem a bit high. I've seen these woofers pumping on Crown iT8000's, and I still haven't seen them hit what looks like 23mm. This could also be due to the tuning of our SRX728S's and the settings on our processing as well.
Finally, who carees if these things can do 23mm anyway? They sound freakin' great and can take a huge amount of abuse. In the two years that my company has beeen using them, we haven't blown a single one due to thermal damage or over-excursion. We had a few cones tear after they got wet at an outdoor show and weren't allowed to dry completey before being used again. I have had the same success with the 2262HPL's in our VerTec and VRX rigs.
Cheers,
Zach
It's not important.
The 2268 looks like it should have about 3dB more maximum output than the 20+ year old driver design 2241 based on x-max. Considering what you can sell a used 2241 for, it makes a certain amount of sense to buy a 2268.
While it looks like a good driver, I will probably never own one.
I use pairs of 15s in push-pull configuration. The push-pull configuration reduces distortion even more than what can be done with the copper rings in the motor that JBL uses. Three pair per side have the same volume displacement that two pair of the JBL have, and at about 1/4th the cost. The JBL can handle more power, but are less efficient, so I don't need the extra power handling, and I don't have to buy the extra amplifier power either.
As they say with cars, your mileage may vary.
The 2268 looks like it should have about 3dB more maximum output than the 20+ year old driver design 2241 based on x-max. Considering what you can sell a used 2241 for, it makes a certain amount of sense to buy a 2268.
While it looks like a good driver, I will probably never own one.
I use pairs of 15s in push-pull configuration. The push-pull configuration reduces distortion even more than what can be done with the copper rings in the motor that JBL uses. Three pair per side have the same volume displacement that two pair of the JBL have, and at about 1/4th the cost. The JBL can handle more power, but are less efficient, so I don't need the extra power handling, and I don't have to buy the extra amplifier power either.
As they say with cars, your mileage may vary.
Are there any (more or less) exact figures you can talk about when it comes to reducing distortion with push pull? And/or how much of a noticeable difference (to the ear) are we talking about?
Always been told mechanical distortion is the least interesting compared to uneven order.
With kind regards Johan
Always been told mechanical distortion is the least interesting compared to uneven order.
With kind regards Johan
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