JBL 2268HPL as opossed to JBL2242H

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.

JBL 2268H specs.

FS - 33
QTS - 0.36
QMS - 3.8
QES - 0.39
VAS - 328
EFF - 2.8
PE - 800
XMAX - 23
RE - 5.3
LE - 1.85
SD - 0.1269
BI - 21.5
MMS - 168
FLUX - 0.6

All JBL pro driver info can be found here.http://www.jblproservice.com/pdf/Thiele Small Parameters/Theile Parameters.pdf

And you still don't have complete data, and if you believe that spec for x-max I have a bridge for sale....

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?

That was a joke, no one actually owns the bridge they are offering to sell you.

The data is obviously wrong.

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.

"I'm aware you were joking"

Never can tell, the joke is kind of specific to the US.

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.

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Wrong and wrong. There is a data sheet http://www.jblproservice.com/pdf/Thiele Small Parameters/Theile Parameters.pdf and it is available as a replacement part http://www.jblproservice.com/pdf/Transducer List/05 Transducer List.pdf

The data is obviously wrong.

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Can you present your factual evidence to show this? It's not so "obvious" to me. Thanks.


cheers,

AJ

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.

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

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.

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/VT4880A Spec Sheet.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

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.

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Correct. So where is your proof?

Guess you don't know as much about driver design as I do.

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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.

djk said:

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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If in mm it is perfectly acceptable. The 2242 has 2" of Xmax peak to peak before any mechanical damage!

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!

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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

Guess you don't know as much about driver design as I do.

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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