Jbl 1500al

[merlin]

Does anyone know where I can source a couple of these drivers for shipping to the UK.

I understand that they are available in Japan seperately, but I cannot find a supplier.

Any help would be much apreciated

[merlin]

Thanks for that Giskard,

A real shame that, as whilst I know they are big bucks, I really wanted to build with the best.

The plan was to utilise them in dedicated cabs, crossing over at 350hz. Do you have a recommendation for an alternative by chance?

[Earl K]

Hi Giskard

If you still have them , would you post the TS parameters for the ME150HS woofer ?
( You had in the last forum but being quite slow, I failed to store it - can you provide a link to that old post ? )

Thanks <. Earl K

[boputnam]

"The FE is used in the 4348"

What be a 4348...?

[Don McRitchie]

Current high end "Monitor" for Asian market. Replaces 4344MKII

[Earl K]

Thanks

- Didn't expect to see an Fs of 38 Hz for that ME150HS.........

regards <> Earl K

[GordonW]

Giskard, would you happen to have the Xmax spec, either from JBL or from any DUMAX or similar test anywhere, on these drivers? That's one other parameter, that the guy probably should have in order to compare that driver with others, for low bass reproduction purposes...

Regards,
Gordon.

[sa660]

A gentleman on Ebay.uk try to sell some very expensive JBL tweeter 045TI only available in Japan. He may be able to help
You could try to find a japonese shop that will buy and ship back to Uk these drivers.

Regards,

[merlin]

Thank you gentlemen for your advice.

It appears that I have been able to purchase a couple of 1500AL's (well they've taken the order and my money so here's hoping!)

Now I guess I should post over on the technical forum, but any ideas for the ideal cabinet design, along with recommended fillings etc would really be greatly apreciated. The cab will be intended for use up to 325hz, the maximum allowed using my digital setup, and I intend using a ported enclosure.

I hope you don't mind a newbie asking for such basic advice, but it appears that this place really is the oracle when it comes to completing this project.

Thanks once again

Michael

[GordonW]

Originally posted by merlin

Now I guess I should post over on the technical forum, but any ideas for the ideal cabinet design, along with recommended fillings etc would really be greatly apreciated. The cab will be intended for use up to 325hz, the maximum allowed using my digital setup, and I intend using a ported enclosure.

I don't know about recommended enclosures from JBL themselves, but I ran the driver through a standard box-modelling program, and came up with the following:

5 ft^3 box, with 3- 4-inch diameter, 14 1/4" long ports, with at least 4" thick fiberglass on all the walls Preferably, more than that on the bottom wall, and behind the driver itself.

This will give a very damped response, with an Fb (tuning frequency) of about 31 Hz, an f3 of about 37 Hz, an f6 (6 dB down) of about 28 Hz, and an f10 (pretty much where useful output stops) of about 25-26 Hz. This, in a reasonably normal size room in a home (say, 20x30 feet or less), should, with the normal gain of a room, give useful output down to 30 Hz or lower, easy.

If you want to use this as a "true subwoofer", ie output down to the lower 20s, check out using an active filter to boost the bass down low (the threads about the 4350/55, and some threads involving the 4343 around here, give some info on what can be done), and change the port frequency accordingly (will be lower port frequency, to match the boost filter frequency, basically). With the volume displacement available on this driver, I would see no problem boosting the response down to 25 Hz... a SINGLE woofer should be able to do close to 116 dB down there, before running into excursion limits and distortion... so a pair should be able to do close to 120 dB, in room @ 1m distance!!

Regards,
Gordon.

[merlin]

Thank you very much for that Gordon.

I had also run the specs through WinISD and come up with similar results. Looking at the 9800K2, this appears to be very close to the dimensions of the bass enclosure used by JBL themselves in the flagship. Reviews here in the UK give in room response of -3db at 20hz.

What confuses the issue for me is the use of the Tact RCS2.2X digital system, which equalises the bass. Should it prove neccessary to boost the low frequencies however, I would experience digital clipping from the processor. I need extension down to the low 20's which I had, given a lack of specifications and my stupidity, assumed would be simple with the 1500AL.

I will look into using an active filter, thanks for that. In the meantime, I have asked Peter Lyngdorf of Tact for some assistance and will be in touch with JBL. I will keep the forum posted.

Best regards

Michael

[merlin]

Well Gentlemen, I have been delighted with the speed of response from JBL.

My email query quickly reached Greg Timbers' inbox, and he was kind enough to offer advice. His comments are below

"I would recommend a larger enclosure than 72 L. I am using 110 L - 120 L.
The simulations show this as an over damped alignment, not optimally flat,
but I have had much better results with larger enclosures. I have the
system tuned to 27 Hz using a 100 mm vent with generous radii on either end
to reduce turbulence noise. It gives a response that looks very much like a
banana. There is a gentle curved roll off below 100 Hz and no sign of a
knee in the curve. This curve shape has much better group delay
characteristics and self equalizes due to room gain very nicely. I expect
you will only need a few dB of boost (less than 6) to get the LF level you
wish. The system is still very active at 20 Hz and extremely powerful
between 30 Hz and 40 Hz. The only problem you will have is leveling out the
climb above 100 Hz should you decide to crossover at 300 Hz. I also
strongly recommend a rear mounted port. I really like having the port
opening on an opposite side from the woofer. It will reduce the subjective
level of any port noise and it also reduces the impact of higher band
information which invariably comes out of the port.

As you are going to a rather high crossover frequency, avoid equal internal
dimensions. Brace the enclosure substantially and I like the idea of 1.5"
MDF baffle material. A 100 mm duct will need to be around 300 mm long to
get the tuning frequency."

So a big thanks to Greg, a true gentleman and a credit to JBL. He is using the 1500AL in a similar subwoofer for his home cinema setup and I think he expects to be the first of many. We will be building up a working model over the next month and I will report on progress.

Thanks once again for your input.

Regards

Michael