| Xciterking |
| Anybody know anything about these two speakers who might help with the difference? JBL 2268HPL or JBL 2242H ?:D |
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| djk |
I haven't heard the 2268.
JBL does not publish a complete data sheet on this woofer as they do not sell it other than as a part of a complete syatem in a cabinet.
However, according to JBL it does not have as much maximum output as the 2242, and is less efficient (about 2dB).
While both are rated at 800W, the 2268 has only a 3" coil vs the 2242 with a 4" coil. |
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| djk |
| And you still don't have complete data, and if you believe that spec for x-max I have a bridge for sale.... |
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| Mikey p |
| The data is what is available from JBL. If you're selling a bridge, how did you get stuck with it in the first place?:D |
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| djk |
That was a joke, no one actually owns the bridge they are offering to sell you.
The data is obviously wrong. |
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| Mikey p |
| I'm aware you were joking. I was joking back at you. As for data accuracy, whoever is interested can verify it with JBL support. I'll stick with my Adire products.:) |
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| djk |
"I'm aware you were joking"
Never can tell, the joke is kind of specific to the US. |
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| djk |
Guess you don't know as much about driver design as I do.
The x-max spec is bogus.
JBL states it has 2dB less maximum output that the 2242, which has an x-max of less than 8mm, yet the T/S for the 2268 says 23mm, figure it out. |
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| ralphs99 |
While you may know more about driver design than the rest of us djk....
I would like to point out that JBL's maximum output specs are done at midband frequencies and represent a thermal limit. They are not based on X-max limitations.
The published X-max is probably accurate. JBL were one of the first companies to publish X-max figures as well as state the conditions under which they are achieved.
Of course a typographical error is always possible, but the sub woofer system the driver is used in also gives a similar figure for X-max.
I personally believe the published value as I have no reason to doubt it.
Regarding the voicecoil diameter. The smaller diameters used in the newer JBL drivers seems to be a trend brought about by the use of neo magnets and longer coil winding depths.
Of itself a smaller diameter voicecoil is not a deficiency but merely represents a different set of compromises brought about by new materials and construction techniques.
Cheers,
Ralph |
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| djk |
No where in the literature for any product using that driver do I find an x-max spec.
No where do I find a spec for the coil lengths and gap heights.
There is a press release on the new 2269G that states the mecanical damage limit is 44.4mm, but that is a very different driver than a 2268H.
Perhaps you could link to any sort of page that would give some hard data. |
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| ralphs99 |
Hmmm,
It seems I was looking at the cut sheet for the VT4880A which uses the 2269 rather than the '68.
http://www.jblpro.com/vertec1/VT488...pec%20Sheet.pdf
None the less, I still don't see a reason to doubt the published in data for thr '68 in the absence of any evidence to the contrary.
Cheers,
Ralph |
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| AJinFLA |
| quote: | No where in the literature for any product using that driver do I find an x-max spec.
No where do I find a spec for the coil lengths and gap heights. |
Correct. So where is your proof?| quote: | | Guess you don't know as much about driver design as I do. |
JBL states the xmax as 23mm on their T/S page. Your vast knowledge of driver design notwithstanding, you have presented zero data to refute this.
You claim it is bogus. Please present your evidence. Thanks.
Cheers,
AJ
FYI, my Vifa XT25 has Xdb more maximum output than the JBL2268....@ 20K. It sure has less xmax than the JBL. |
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| short_circutz |
| quote: | Originally posted by djk
And you still don't have complete data, and if you believe that spec for x-max I have a bridge for sale.... |
If in mm it is perfectly acceptable. The 2242 has 2" of Xmax peak to peak before any mechanical damage! |
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| Rademakers |
| quote: | | This should settle the Xmax debut. I just talked to JBL and it is 23mm for the 2268.....If in mm it is perfectly acceptable. The 2242 has 2" of Xmax peak to peak before any mechanical damage! |
I would still doubt it...
If you're well familiar with the T/S-parameters of most PA-drivers you will notice that Xmax exceeding 10 mm is already quite an outstanding feature that is seldom accomplished.
Even the modern 18" drivers of today with very similar No (zeta), Qes, Qts, Fs, Vas, Mms have Xmax between 5 -10 mm.
You don't have to believe, you can look it up.
Large Xmax requires a large VC winding depth, thus adding mass to the Mms. The Mms on the contrary is around or below moderate for the given Sd (compared to regular 18" PA-drivers).
So either the gap depth is just a few mm (never seen) or a very, very light VC and winding is used (not likely). The VC diameter could be very small but that would be unlikely just looking at the power handling.
AFAIK JBL uses gap heights of 7 mm+ resulting in a VC winding depth of (23 x 2) + 7 = 46 mm. With 25 mm being already quite large for modern 18" PA-drivers. Other Xmax calculations are available (like adding 1/4 gap depth) but would be out of the question for such small gap depth or still not not coming close to the stated Xmax.
For PA-driver it's very common to have a Xmech about 2 times Xmax. 2" (51 mm) p-p Xmech would indicate 25,4 mm (1") Xmax p-p. Xmax is stated as 0-p so 25,4/2 = 12-13 mm.
Note that the VC winding depth would be 46 mm p-p so Xvar would be 2 mm (Xvar = Xmech -Xmax).
For illustratively purpose:
The 18LW1400 (18sound) has also 2" p-p Xmech however just 5-9 mm Xmax according to different Xmax calculations.
The SD-18 (P audio) has an Xmech of 60 mm p-p and still has 5-9 mm Xmax. Both drivers are good drivers for modern standards.
The V18 1000 (Void Acoustics) is excellent for modern standards, so is the P1850 (Precision Devices), still both drivers have Xmax around 10 mm and Xmech around 2" p-p.
If the Xmax for the JBL is true with such stated efficiency it would swamp all the other 18" drivers mentioned/ I know of. How come a killer driver like that isn't at the ultimate top where it belongs unless stated Xmax is indeed false?
Note: The Xmax as spec'd is by far the most unreliable parameter. From all brands out there I can count the ones that stated Xmax without any form of misguiding on one hand. This includes the top brands of today's market.
Btw: I do believe that I know what I'm talking about. Looking at other posts by djk on various forums I do think that he knows what he's talking about. Still you can choose not to believe my claims but what reason would I have to give false information on this forum?
I can think of several reasons why even a direct contact with JBL would not be as effective as one might think. Intention of marketing being the most important.
A similair case happend with the RCF L18P300, where 12 mm was finally reduced after long time to the rightfull 7-8 mm Xmax.
With kind regards Johan |
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| AJinFLA |
| quote: | | Guess you don't know as much about driver design as I do. |
There goes that theory I suppose :). Perhaps just a bit too much speculation on DJ's part.
Now, returning to the original thread question, I'd take the 2268HPL over the 2242H any day.
cheers,
AJ |
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| Rademakers |
Could you react on my post first? It was a lot of typing you know ;)
With kind regards Johan |
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| AJinFLA |
| quote: | I would still doubt it...
If you're well familiar with the T/S-parameters of most PA-drivers you will notice that Xmax exceeding 10 mm is already quite an outstanding feature that is seldomly accomplished.
Even the modern 18" drivers of today with very similair No (zeta), Qes, Qts, Fs, Vas, Mms have Xmax between 5 -10 mm.
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You are obviously still in the dark ages of PA design
http://www.madisound.com/pdf/aurasound/nrt18-8.pdf
or simply speculating like DJ rather than presenting facts.
I take it you know nothing of the new TC sounds drivers either
http://www.tcsounds.com.unixweb-7.n...net/news_pa.htm
Welcome to the 21st century. Johan, gotta run
cheers,
AJ |
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| Rademakers |
Instead of reacting with lots of sarcasm, could you react with little bit more scientific or respectfull approach?
Sarcasm seems to be quite often used if there is lack of knowledge to the actual subject itself.
1. Reading the site of TCsounds and others it appears that such large Xmax requires different approach when it comes to the spider. Spiders other than ussual PA-drivers incluiding the 2268H use.
2. Also the use of neodymium opposed to ferrite is acuired to keep the weight down (relative as the neo versions weigh as much as populair ferrite drivers).
3. Efficiency stated for all drivers on both sites is still low compared to PA-drivers. TC seems to be doing a better job than expected but still not like the JBL states.
4. It would be strange to compare the performance of overhung designs directly to underhung designs like the TC and Madisound. The structure of the magnet is of course very different.
With kind regards Johan |
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| AJinFLA |
| quote: | | there is lack of knowledge to the actual subject itself |
Hi Johan,
ok, you and DJ are both right. In the face of your overwhelming amount of evidence to the contrary, there are no PA woofers with 18mm, 23mm or 30+mm xmax. 5-10mm sounds just about right.
The xmax specs of JBL, Aura and TC are all wrong or simply outright lies.
I'll take your and DJ's words as fact. I apologize for doubting you guys and intruding upon your reality. Take care.
cheers,
AJ |
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| Rademakers |
| quote: | | OK, well I bought two of these today, hope it was a good choice? |
Yes it was (imo),
So what are your plans with these?
With kind regards Johan |
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| Xciterking |
| I know this is could be wrong but I'm going to replace my 2241G JBL's in my SR4718A cabs. :scratch: I don't want to pack a bunch of cabs around and I don't like lifting heavy stuff anymore. |
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| Rademakers |
The 18LW1400 works in most reflex cabs so I don't expect a problem there. The port looks a bit small tho, especially due to higher powerhandling.
Gonna post some pics?
With kind regards Johan |
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| Xciterking |
Infact, yes I will. Maybe I could borrow a few ideas.
My other problem is, for now I plan to keep using my same amps. One QSC 1602 for each sub. I'm worried there won't be enough power. Bridged will then only bring me 1100w |
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| Magnetar |
| quote: | Originally posted by AJinFLA
There goes that theory I suppose :). Perhaps just a bit too much speculation on DJ's part.
Now, returning to the original thread question, I'd take the 2268HPL over the 2242H any day.
cheers,
AJ |
Really? Why?
Not to start an argument but Dennis (djk) is of course the man with the knowledge here - he has extensive experiance with pro drivers and horns. I'd say more than anyone that has ever posted on this forum. He is a man to be trusted. These drivers are EXPENSIVE - It's your money.
2242's? They are AWESOME. I use three of them in horn subs - Just about right, maybe a bit of an over kill, for realistic bass in a typical home listening room. Two of of them in corner horns is probably enough.
2268? Three inch voice coil - That's what JBL uses on their cheap bass drivers. |
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| AJinFLA |
DJK and Johan may know the world about PA drivers, but they knew nothing about the JBL2268H - and proved it with their ignorance of the facts.
Neither has admitted to being flat wrong about the JBLs spec'd xmax of 23mm.
That is one of the reasons I would prefer it. The 2242H is a woofer. The 2268HPL is a sub woofer that will play much lower and louder (except at midbass frequencies).
| quote: | | 2268? Three inch voice coil - That's what JBL uses on their cheap bass drivers. |
You have now joined them in commenting on a driver you know little about. The DD motor uses two coils on a single former operating in seperate gaps. Believe it or not, if JBL thought there would be an advantage to using a larger diameter coil for the dual coil design - they would.
Again, DJK, Johan and possibly yourself, may think you know more about driver design than JBL, but you don't.
Speculation won't change that.
Do yourselves a favor and read up on the 2268HPL's technology before casting judgement and stating facts about this driver http://www.jblpro.com/pub/technote/...1-33%20rev3.pdf
Or better yet, work with it in the field and hear it like I have ;).
Then tell me it doesn't have 23mm xmax or sucks compared to the 2242 with its 3"vs 4" coil, etc, etc.
cheers,
AJ |
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| Xciterking |
| So AJ, it sounds like you got it right. My problem now is to make the decision to get two 2268's for $720 or the Eighteen Sound LW1400's for $660. I will be installing them into two SR4718A cabs. 8ohms @ 1100w. I have two QSC 1602's. I still can send back the 1400's, they will be here any day. I might need more power?:xeye: |
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| Magnetar |
| quote: | Originally posted by AJinFLA ;).
[I]Then tell me it doesn't have 23mm xmax or sucks compared to the 2242 with its 3"vs 4" coil, etc, etc.
cheers,
AJ [/B] |
Thanks for the link - those look KILLER
Not sure about the sound or xmax - the technology seems like it's the **** |
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| djk |
Hey AJinFLA , why don't you see if you can get some hard data from JBL on those drivers. I had already seen every word in print at JBL before you ever posted a single comment. No where do they list the gap height or coil length.
Considering that there are many small errors in the pdf of the drivers that they publish, when I see something that looks wrong, it's wrong.
People that aren't familiar with what a driver can and cannot do are welcome to use a computer program. I have one that JBL used to sell. You enter all the T/S parameters in and push calculate. Guess what? If something doesn't add up, it red flags it.
One thing the wise guys haven't noticed about the dual coil drive from JBL is that as the coil starts to move, there are fewer turns in the gap after the half x-max point. This means that the coil is still in one of the gaps, but not in the other. So at loud volumes the driver force decreases considereably. The dual gaps design is also only specified as having half the flux density of their older drivers.
This is obvious, the more gap volume for a fixed amount of energy, the less force over the coil. This is one reason EV always used a 2-1/2" coil even though the magnets were 4" in diameter (same alnico slug JBL used with the 4" coil).
It used to cost $100 to have a driver Du-Max tested. In the absence of any such data from JBL, I would spend my own money and have the thing independently tested before buying a bunch of these for any large PA company that I owned. |
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| short_circutz |
| quote: | Originally posted by AJinFLA
<snip> 5-10mm sounds just about right.
The xmax specs of JBL, Aura and TC are all wrong or simply outright lies.<snip> |
I own two of these. I've seen them running. I know what the excursion capabilities of the speaker are. I've seen it first hand.
And also they are capable of -3dB response to 20 hz when using extended bass shelf loading. |
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| djk |
"I own two of these. I've seen them running. I know what the excursion capabilities of the speaker are. I've seen it first hand."
And what does this prove?
I built some 8 cu ft boxes with the K151 tuned to 31hz (30 years ago). This driver has a paper edge. That's right, not cloth, foam or rubber, but paper. When driven with a 150W amplifer it could be seen to move about 2" peak to peak. The stated x-max on that driver is only 2.54mm!!!
Driving the speaker below cabinet tuning to the limits of suspension travel produces no audible output.
Those of you that have box programs can follow this design excercise.
Plug in the published parameters for the 2242, use 8 cu ft and tune to 31hz. This is a reasonable box size and the modeling program distributed by JBL suggests it for this driver.
Plug in the published parameters for the 2268 in the same exact box.
Plot and overlay the response, and cone excursion at 800W, examine.
What you will find is the identical 9mm excursion at about 50hz, this is the worst case for this box tuning. At 1W the 2.83V sensitivity is the same at 96dB, ±.2dB. At 31hz the 2242 has about 1.5dB more output!
If the 2268 was capable of 23mm x-max (which I doubt), it is thermal limited to 9mm. That's right, it would burn up. Acording to the program, it would take 20KW to drive it to 23mm at 31hz!!!
That's why I said I didn't believe the x-max spec. No one in their right mind would design a speaker that needed 20KW to reach that full 23mm excursion and would only handle 0.8KW !!!
I'm sure the 2268 is a good driver, and so is the 2242. Only you can decide if the reduction in weight is worth the cost difference to trade.
I use JBL high frequency, but have my woofers custom made. 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. So I get 2.5dB more maximum output, less distortion (due to the push-pull mounting), and for 1/3 the cost of the JBL drivers. |
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| ralphs99 |
Hi Magnetar,
The 2242 is a great driver, no dispute. For horn loading, a better choice than the 2268 due to it's lower Qts and higer efficiency.
Cheers,
Ralph |
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| ralphs99 |
Hi DJK,
This analysis of yours just doesn't hold water. The 'evidence' you present against the 2268 having it's claimed Xmax is purely circumstantial based on gross assumptions. You cannot guess what was in the mind of the driver's designer anymore than anyone else.
Your assumption that this driver would only be useable in reflex alignment is baseless. It could just a easily be used in a sealed box.
The 2269, which you agree is capable of large Xmax, is similarly capable. Looking at the impedance plot of the VT4880A sub which employs the 2269, it appears that this design is in fact a sealed enclosure. Interestingly the text describes it as 'centrally vented' whatever that means.
I am still to hear of any evidence that shows the published Xmax data for the 2268 is in error.
Cheers,
Ralph |
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| AJinFLA |
To be honest with you DJ (and Johan), the onus isn't on me to prove that JBL is right. Rather, it on you to prove that they are wrong.
I find no reason to doubt the JBL spec sheet. You both do. Prove it with data from an actual 2268 if so inclined. I have greater worries in life than to spend time on such frivolous endeavors.
I wonder why it is that you don't take issue with the (Pro) Aura's 18mm or TC's 30+ ? Somehow, in your minds, 23mm makes no sense. Go figure.
Anyhow, I done with this (non) issue. Time to move on.
Xciterking,
you should not base your decision on anything I or anyone else on an internet forum says. Base it on your exact needs that you should know best. If you need a sub look no further. The SR4718 cab should work, but for the ideal enclosure, either use the T/S parameters to tune it to your liking or copy the http://www.jblproservice.com/pdf/SR...ies/SRX718S.pdf .
My only question is where the heck do you get a pair of 2268H's for $720?
cheers,
AJ |
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| Xciterking |
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
:scratch1: |
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| Magnetar |
| quote: | Originally posted by Xciterking
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. |
Hello, how much are the 2242H's?
Thanks |
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| Xciterking |
| I’m not sure. I found the 2242 idea after had already ordered the 2268's. Then someone blew air up my *** that 2268's have sort of a strange or different sound because of the neo-magnets and might not be the right choice for me. I think the 2242's listed for around $600 each. I got nervous about my choice. That's when I sort of talked myself into the LW1400's. Guessing, I get the idea you like the 2242's and AJ likes the 68's. Kris |
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| Xciterking |
| I can get them for around $400 I think. I will check if you want me to. |
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| djk |
To the person that believes in the Easter Bunney and thinks the JBL 2268 has 23mm x-max.
Yes a sealed box would eat up all that x-max. A 2268 in a Qtc=0.707 (maximally flat) box would be 3dB down at 75hz. Compared to the reflex box at 31hz it would hit 23mm x-max with only 5.5KW
Why would JBL build a driver that took almost 7X its maximum power rating to take advantage of its x-max?
IF it did have 23mm x-max, AND could handle 5.5KW, then it could play about 120.5dB at 31hz, assuming NO power compression (we must believe in the tooth fairy too). The vented box under the same impossible 5.5KW input and no compression would be playing 130.1dB, but only moving about 11mm.
As regards the Aura 1808, the radially polarized gap is about 2" long, and the coil is underhung. It does have a real x-max of 3/4" (18mm).
Drivers like the TC Sounds are a different kettle of fish. Being overhung they are less efficient, about 7dB~9dB less than the PA drivers under discussion (not to mention tipping the scale at over 45 pounds). I'm sure they can handle the 3KW they're rated at for car stereo 'burps' and typical home theater use, but if you try that kind of power long-term at a dance party I think you will be in for a surprise. |
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| Magnetar |
| quote: | Originally posted by Xciterking
That's when I sort of talked myself into the LW1400's. Guessing, I get the idea you like the 2242's and AJ likes the 68's. Kris |
All I can say is what I said previosly - the 2242's in the horns are extemely low compromise. I could probably write a 5 page of 'review' of audiophile superlatives ;) but that kind of stuff gaggs me- I've built/owned many bass systems and this is the one I listen to below 80 cycles and have not had the urge to replace - ever. It's a fact it will 'keep up' (low compression, high efficiency, low distortion) with any horn speaker system that will fit in my room. |
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| Mikey p |
| quote: | Originally posted by djk
To the person that believes in the Easter Bunney and thinks the JBL 2268 has 23mm x-max. |
 
Meet the WOOFER-BUNNY !!:) |
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| djk |
| All the drivers discussed are good, with the possible exception of the 2241, it has mechanical damage issues. |
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| AJinFLA |
| quote: | | I wanted your advice on which speaker; (if you had a choice) would you buy. |
The 2268 Kris. It is the superior driver, comparable only to the Aura/Seismic (very expensive) and the upcoming TC.
Be prepared for some serious bass when your intermission hip-hop comes on. You won't bottom these like that. You'll see ;).
Cheers,
AJ |
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| djk |
"Looking at the impedance plot of the VT4880A sub which employs the 2269, it appears that this design is in fact a sealed enclosure."
Blind as a bat, I see. The impedance plot shows a vented box with an impedance minima at ~29hz and the traditional double hump, the upper one ~53hz and the lower one around 15hz.
Ohh, you say? The plot cuts of at 20hz? How do you know?
The same way I know the other things I have expressed. The clues are there to someone with more experience. |
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| Magnetar |
In my experiance long excursion, low efficiency drivers like the TC sounds are prone to power compression and high distortion (poor sound) . I don't see those specs at the website linked.
High efficiency drivers (like JBL 2242) loaded in a horn is a whole different animal. It would take like 16 of the TC sound 15" woofers to equal the output of one of the 2242's in a corner horn - Xmax means little when you are @ 106 db with a watt in a horn.
It's been said for decades the longer the stroke and cone movement the higher the distortion. Also think about all those 'watts' being lost with the TC' low efficiency conversion - heat & compression are bad not good. |
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| Xciterking |
I have decided to just keep the Eighteen Sound LW1400's for today. I'm up early today to go out there and install one in one of my cabs and hook up the system to hear for myself the difference between (at least) the 2241G and the LW1400 in person. People were telling me that the LW's are installed in some of the high end EAW's. Might not be true, crossing my fingers. I will take some pics to post later today. I’m just not sure if I like the looks of these things. They are very large; I must be used to JBL.
Another engineer called last night and has offered up two 4718's with covers in perfect condition for $1000. I might just get those also, leave no doubt of satisfaction. Then if I like the LW's that much, I could pick up a couple more, grabs some power and Walla, case closed. Thanks for all of your help guys!
:) |
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| Xciterking |
| Grab some power is right, and lots of it. LW's won't work well with the 1602's.:bawling: |
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| djk |
Ho-hum, another driver with no datasheet.
The only thing they say about that driver is that it can move 1-3/4" one-way before something slams into the frame or magnet.
As regards the 2268:
I really don't care, if you want to believe the bogus numbers, go right ahead.
I will stand corrected when you have a JBL engineer e-mail me with the gap height and coil lengths.
JBL claims 23mm x-max on the 2268H in their line listing of T/S parameters. If you look closely the other two drivers with the same basic motor are only 8mm and 11mm respectivly. The 8mm driver is the same efficiency as the 2268, the other is lower efficiency, hence the longer x-max (it also has higher Le than the 2268 indicating a longer coil,m and az higher Bl, indicating a longe coil too). On a line right above that is a driver with the efficiency listed as 700%, I suppose he believes that too.
JBL has not published a full data sheet on these drivers, so we don't really know. But the Le and Bl tell the story in their own way, as does comparing it with its siblings.
The completely different W15GTi has two 0.5" gaps, and two 1.3" coils. The x-max claim of 0.8" is proven by these measurements. The W15GTi needs over 3KW to make it hit its x-max. Its only 92dB/2.83V, and its 3 ohms, so it is 87.74dB/W/1M
The 2268 is 2.8% efficient, that's 96.5dB/W/1M
Do you suppose it's almost 9dB more efficient because it has a much shorter coil?
No such thing as a free lunch.
Again, I will stand corrected when you have a JBL engineer e-mail me with the gap height and coil lengths (like they provide for the W15GTi). |
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| djk |
Look what I found:
Re = 5.3 ohms
Fs = 33 Hz
Qts = 0.36
Qms = 3.8
Qes = 0.39
Vas = 328 liters
no = 2.8 %
Sd = 0.1269 sq m
Mms = 168 grams
Bl = 21.5 T*m
Pe = 800 W
Xmech = 23 mm (spider bottoms on gap sleeve)
(Still no spec for x-max though) |
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| johninCR |
DJK,
I'm surprised you're still wasting your time with this. The 23mm xmax is obviously an error, probably an error by a secretary entering technical data instead of an intent to mislead. You've already explained quite well why it must be an error and even pointed out another typo in the same listing. You tried, but "You can lead a horse to water...". |
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| knightcrawler |
| quote: | FRANKFURT, GERMANY, 29 March 2006 — In an engineering breakthrough that adds to the power and versatility of JBL Professional’s VERTEC® line array series, the company has developed an innovative Ultra Long Excursion 460mm (18”) transducer with 2000 watts continuous (AES), 8000 watts peak power handling capacity. The model 2269 is the latest example of JBL’s patented Differential Drive® dual voice-coil loudspeaker technology, and is fitted with dual voice coils and magnetic gaps, and an ultra-robust composite cone. It provides high output capabilities with an extremely advantageous power-to-weight ratio and is available only in JBL’s two newest VERTEC subwoofers, the VT4881ADP compact powered subwoofer and VT4880A full-size passive subwoofer system products.
“The VERTEC series has established itself as the leading line array option through its power, fidelity and versatility,” said David Scheirman, Vice President of Tour Sound, JBL Professional. “By incorporating the new 2269 transducers, the VT4881ADP and VT4880A provide audio professionals with enhanced subwoofer capabilities in areas such as concert audio and multimedia presentations where extended low-frequency performance is desired.”
The new Ultra Long Excursion 18” transducer features dual neodymium magnets, JBL’s exclusive Vented Gap Cooling™, and robust suspension elements for high excursion and extra long life. The new woofer is capable of a peak-to-peak maximum excursion of 89 mm (3.5”).
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Seems like it's built for long excursion. |
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| djk |
At the risk of repeating myself:
"The only thing they say about that driver is that it can move 1-3/4" one-way before something slams into the frame or magnet."
"I'm surprised you're still wasting your time with this. The 23mm xmax is obviously an error, probably an error by a secretary entering technical data instead of an intent to mislead. You've already explained quite well why it must be an error and even pointed out another typo in the same listing. You tried, but "You can lead a horse to water..."."
John, you're absolutely correct. I've sent JBL some mail as regards this, we'll see if they reply. |
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| noah katz |
I wouldn't expect a reply if you used the same pugnaciousness tone you're using here.
The whole thing is puzzling, though.
I've never seen an accordian suspension with as much excursion as they're claiming.
I wonder if by x(mech) they mean x(sus), which is a measure of suspension stiffness nonlinearity, not max mechanical excursion. |
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| knightcrawler |
| quote: | Originally posted by djk
At the risk of repeating myself:
"The only thing they say about that driver is that it can move 1-3/4" one-way before something slams into the frame or magnet."
"I'm surprised you're still wasting your time with this. The 23mm xmax is obviously an error, probably an error by a secretary entering technical data instead of an intent to mislead. You've already explained quite well why it must be an error and even pointed out another typo in the same listing. You tried, but "You can lead a horse to water..."."
John, you're absolutely correct. I've sent JBL some mail as regards this, we'll see if they reply. |
Yes but will you believe them when they tell you that the xmax is 23mm ?
I don't know what the problem is here, JBL is not known to fudge the numbers. I have used them for years.
The differental drive system that JBL developed is a bit different from the conventional. |
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| johninCR |
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. |
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| knightcrawler |
| quote: | Originally posted by johninCR
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. |
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. |
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| djk |
| 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). |
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| though |
| 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! |
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| djk |
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. |
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| AJinFLA |
| quote: | | so we really don't know what it can really do. |
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 |
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| mefistofelez |
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 |
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| jblmar |
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 |
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| jblmar |
If it is a typo, it will be repeated there. It would be a good idea to have JBL do the research.
Ron |
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| jblmar |
That site is very good!
Ron |
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| johninCR |
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/B...15GTi_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. |
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| AJinFLA |
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/...1-33%20rev3.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...ab5fda3922ce62a
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 |
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| djk |
"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. |
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| johninCR |
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? |
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| usekgb |
| quote: | Originally posted by Xciterking
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
:scratch1: |
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 |
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| johninCR |
| AAAAAAJJJJJJJJ, where rrrrrrrrr uuuuuu ? Be a man and apologize to DJK. |
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| djk |
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. |
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| Rademakers |
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 |
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| johninCR |
Johan,
My only direct comparison with push/pull and non-push/pull pairs was using cheap 12" drivers. The audible difference was more than subtle even at only moderate volumes, where distortion should be low. I speculate that more than just linear operation of the cone is involved, and the sound from the back of the driver is different due to influences of the basket and magnet structure, plus even the Sd is different. A push/pull alignment ensures that these differences are balanced out. |
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| djk |
"My only direct comparison with push/pull and non-push/pull pairs was using cheap 12" drivers."
The cheaper the drivers, the more push-pull will help them.
"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?"
Some old comments cut&pasted from elsewhere(sorry, the link is dead):
Kind of like this:
http://cgi.ebay.com/ws/eBayISAPI.dl...Item&item=73392 75215&category=47094&rd=1
This was a box EV came out with after I talked with one of their engineers at a trade show about 20 years ago.
EV showed me the light in 1974 with the Interface A, an SBB4 alignment with a Q=2 filter ahead of the amplifier, so it became a B6.
All my best vented designs were assisted B6 or C6 after that.
Around 1980 a friend of mine that was a FOH engineer with dB Sound turned me on to the (then) unreleased MTL4 design. I thought it was cool, but didn't like the short x-max 18s (I don't like 18s in general), and didn't want to have to use a fork lift to move it.
I built a half-height design with two 15s facing each other on a narrow slot. On one of the pair I mounted the drivers push-pull (the reversed driver hooked up out-of-phase electrically).
This sounded so different I thought it sounded funny (at first).
It sounded funny because it had no distortion. It made a large 40hz bass horn sound distorted in comparison. I had Eminence custom make me a large x-max 15 that had the same volume displacement as a good 18 (and went lower).
Now, of course, we see push-pull boxes from EAW, TAD, etc, although I have not seen any exactly the same as the ones I made.
I took an engineering type job (doing L-band RF stuff for the military) about seven years ago and haven't really made anything much since then. I've been thinking it may be time for another production run as some of my old used boxes are trading hands for more than I sold them for new.
and:
The EV MTL4 has a 6dB peak at 160hz that they eq
out in the crossover. The djk slot loaded
enclosure exibited the same peak when the woofers were
mounted face to face leaving a good sized
cavity. Mounting the drivers in push-pull fashion
reduced the cavity to virtually zero and the peak went
away. As well as the second harmonic distortion.Third
harmonic distortion is reduced by the low pass action
of the slot. Doppler distortion is reduced by the
drivers being at a right angle to the listener. Box
size is reduced by equalized sixth order techniques. I
find a Qts of .312 to be optimum for this purpose. The
slot for 15's limits the HF response to 200 hz. There
is a peak around 800 hz. This is completely determined
by the depth of the slot. There is no increase in
efficency over a regular box. djk
Posted by Jon Risch ( B ) on August 08, 2002 at 20:00:23
In Reply to: Push-pull woofers - how much real distortion reduction happens? posted by freddyi on August 08, 2002 at 12:21:23:
A lot depends on the quality of the drivers, however, even very linear woofers will usually show a 6 dB reduction. It is also more noticable at high drive levels, where the woofers are nearing the suspension limits, and the non-linearities are greater anyway.
Jon Risch (Peavey)
PPSL
Posted by djk ( M ) on May 15, 2003 at 00:39:25
In Reply to: Re: Push-pull slot loaded duel 15's posted by bmar on May 14, 2003 at 20:10:52:
This is how the woofers are mounted. The rear volume is sized and ported for the driver TS parameters, with long slot ports on the sides ala Onken/Jensen.
http://www.linkwitzlab.com/images/graphics/d_woof1.gif
PPSL
Posted by djk ( M ) on May 16, 2003 at 17:26:18
In Reply to: Subwoofer configurations posted by Wayne Parham on May 16, 2003 at 02:49:27:
The reductions in 2nd harmonic distortion from PP mounting on a flat baffle are well known, the non-linearities are equal and opposite and thus the 2nd harmonic is canceled. Because of the driver spacing it only happens in the bottom octaves. The cheaper the driver, the bigger the improvement. I have measured as much as a 20dB change.
By mounting in a plenum several things change. The spacing becomes much tighter so the cancellation will work at higher frequencies, and a cavity is formed.
The cavity does several things, in no particular order:
The size, especially the depth, acts like a low pass filter. This can reduce 3rd harmonic distortion products near the top end of the passband, the effect is small, but audible. The cavity sizes I use have to be crossed in the 150hz~250hz region. It gives a slope of roughly 12dB/oct that must be taken into consideration in the design of the crossover. There is a small peak about two octaves above this point, ~800hz on many that I have done. By varying the Q of the 12dB/oct lowpass filter a LR4 I can get a LR4 transfer function. This filter also reduces the out-of-band peak to -30dB or better. There is also a big reduction in FMD, on the order of 6dB. The air mass at the exit of the plenum seems to act like a point source with no doppler, the cones are moving back-and-forth sideways rather than towards-and-away from you. At first glance this would seem to eliminate the FMD, in practice the reduction is on the order of 4dB~10dB depending on the frequencies.
I mounted a pair of drivers in another cabinet in a face-to-face, push-push mode. The box became very 'thick' sounding and had a broad peak centered at 160hz, just like the EV MTL4. In room the response of the push-pull was 6dB smoother in the 100hz~200hz octave.
Being compared side-by-side with the Klipschorn and Cornwall was interesting. At first the push-pull sounded 'funny'. Couldn't put my finger on it. Went back to the push-push cabinet. The push-push cabinet had that 'hi-fi' sound, similar to the Cornwall, but a bit 'thicker'. Klipschorn, much cleaner sounding. Back to the push-pull.
The reason the push-pull sounded 'funny' was the total lack of distortion. Much less than the Klipschorn.
I have not built a basshorn since.
I still use horns, but only above 150hz.
There are some drivers that are not suitble for home hi-fi, mainly those with small magnet vents that can make 'chuffing' sounds when up close.
If enough interest, I can discuss other practical points related to construction and use. |
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| jamikl |
Hi djk, I'm interested in hearing more about dimensioning the cavity.
In the case you mention the speakers are still mounted in a box of some type??? Not like the open baffles with similar cavity? I am looking for something to mate to a horn like the Oris or the Pi or one of the other horns of this frequency range that have been covered in the forum. I don't have room for bass horns. thanks for any information you may think is relevant. Mike
jamikl |
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| mefistofelez |
Dear Dennis,
assuming a 15 inch driver, could the cavity between the drivers be dimmentioned to support operation in 40 Hz to 300-350 Hz?
Thank you,
M |
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| johninCR |
M,
To go that high, I think you'll need to eliminate the parallel panels inside the cavity to avoid resonances, including the driver mounting panels. The opening would be taller and wider than the panel at the back. |
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| 454Casull |
| quote: | Originally posted by knightcrawler
Seems like it's built for long excursion. |
No spider venting? |
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| djk |
"I'm interested in hearing more about dimensioning the cavity."
It's mainly a plenum to mount the drivers in, I generally make it as small as I can and have it all fit together properly.
"To go that high, I think you'll need to eliminate the parallel panels inside the cavity to avoid resonances, including the driver mounting panels. The opening would be taller and wider than the panel at the back."
The parallel resonance is high enough to be out-of-band. The dominant one is the depth, and the height, if close to the same dimension.
The mounting of the magnet structure of the one driver in the face of the other driver cone makes it very irregular in any event. Wayne Parham makes a horn with push-pull 12s. Wayne investigated push-pull mounting after a discussion we had on AA years ago. He says it makes a very audible difference compared to traditional mounting (as in) the Lab-12. Wayne used corner blocks to reduce cavity volume, mainly because the cavity inbetween the drivers and the main horn affects the resopnse of a bass horn a lot in the bottom octave (try it in McBean), not because of higher frequency modes.
I use parallel walls in the mounting plenum area. It does the job, is simple to build, and is strong. An easy way to shape the rear cavity corners is to use 703 fiberglass, trim to fit around the frame with an electric carving knife. If you do this, and make the cavity as shallow as possible (only large enough for mounting purposes), it should yield maximum bandwidth. Remember, we are not trying for a bandpass type resonant cavity.
The EV MTS1 is worth a mention. The cavity on this was paralled walls and push-pull mounted 15s, but instead of the plenum mounted at a right-angle to the front of the cabinet, it was horizontal and hung at an angle, maybe 45°. You would see the front of the plenum and look at the front of the woofer cone of the top driver (at an angle to you), and just a part of the magnet structure of the lower woofer (also at an angle to you). It looked a bit more complicated to build, but it must of had the mid-frequency response because it was mated to a HF compression driver at 500hz. I no longer can find a clear photo (of the plenum) of this product, although the data sheet is archived at EV.
"In the case you mention the speakers are still mounted in a box of some type??? Not like the open baffles with similar cavity? "
You can make it work with any type of loading suitable for your drivers. Mine have mostly been vented, and I use a regular box volumes and port tunings. Sealed volumes work well too. Wayne Parham uses a horn. Linkwitz uses open baffle, as long as you can like with its limitations that's fine too.
"I don't have room for bass horns."
Most people don't. For peoples' with size limitations this is a vey good option. I have a friend that has twelve of the 31hz PPSL enclosures that I designed and had the drivers custom made for. My brother built them. For the total bulk of the system, a horn would have been better, but you can't use just one small bass horn. One of the PPSL will eat any bass horn of similar bulk in the bottom octave. The tapped-horn from Danley might be an exception, but it doesn't have the bandwidth that you can get out of the PPSL, and driver requirements and cabinet details are a bit sketchy at best.
"I am looking for something to mate to a horn like the Oris or the Pi or one of the other horns of this frequency range that have been covered in the forum. "
It should work very well in this application.
I use some custom drivers that will do 31hz to 200hz in a 15 cu ft (gross) box that are about 104dB/2.83V in their passband. This could be a 30" cube form factor for minimum footprint size, although virtually any shape and size can be made to work within the limits of the T/S parameters of the drivers you choose.
Various other box combo's tried:
Dual 8s shielded for a HT system (28hz)
Quad 12s for a car stereo (31hz)
Dual 12s for portable DJ use in a 2' cube form factor (40hz)
Dual 18s for dance club install in a 3' cube form factor (28hz)
Except for the dual 8 design, these were all for rot-your-face-off levels and trade-offs were made for maximum bass extension and minimum size.
The friend mentioned above with twelve dual 15 PPSL boxes used to work for JBL, and now only uses JBL for HF. Steve started out with eight, and only used all eight one gig (not counting a rave). Later he added another four, and has the ability to do multiple jobs of various sizes. Steve only takes one PPSL into small clubs, and seldom does four (two per side). Twice last year three per side were taken out, both were college home-coming dances, one being in a 4,500 capacity auditorium (festival seating, ie: standing room only).
Another sound company about 20 miles away has a similar modular system. A link-up for a huge show may be in the works.
Horn loading is employed above about 150hz (100hz~250hz) depending on requirements. |
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| johninCR |
DJK,
Great info. I can't believe that I haven't thought of filling in the rear corners of the cavities in my manifolds. So even in high performance cabs there isn't a big concern about the area at the mouth? ie Big enough to get the drivers through is sufficient? |
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| AJinFLA |
Mmmm, yummy, crrrowww.
Looks like they should have it listed as Xmech.
Which brings me to the 2269, with its 89mm p-p Xmech.
I don't see it on the T/S list, but it is listed on the Parts List.
http://www.jblproservice.com/pdf/Tr...ucer%20List.pdf (bottom pg1)
For $2250 :eek: . Ouch.
I guess there goes that idea for using either as a dipole sub.
cheers,
AJ |
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| thoriated |
| Hey, if it's Monday morning and you're looking at the data sheet sideways, Xmech can be mistaken for Xmax. |
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