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Heaven_4u
01-05-2006, 03:01 PM
Hello, I am new to this forum.

When I was DJ some years ago I had a set of JBL speakers K140 with double reflex cabinet.

I still have in my possesion 2 K140, 2 passive crossover and 8 tweeters.

I am wondering if I could use those speakers to build a subwoofer. I am looking for specification to built such a box and what type of amp I could us to drive it.

This sub will be use as part of a pro audio set up.

Thanks for any help.

Richard

jim campbell
01-09-2006, 10:46 PM
K140 are much happier in bass guitar cabs,especially mine

doctordata
07-06-2006, 10:52 PM
I build a K140 sub with one driver in a 57 litres ported box , tuned to 20 Hz combined with a electronic filter as published in "Luidsprekers fabels en feiten"
( That's Dutch for "loudspeakers Myths and facts" ) ISBN 90-70160-46-3 The electronic filter contains only three Op-Amps , 9 resistors and one capacitor and is based on the patented "ACE" principle by K.E.Stahl . I use the system for 4 years now, combined with a 150W RMS amp module in my Denon and Tannoy Home theatre and I'm still impressed with the stunning performance of this combinaton , down to 20 Hz - 3dB and loud enough for my 10 x 6 metres living room .

Happy converting ,
Cheers ,
Rens
Brisbane

edgewound
07-07-2006, 10:36 AM
I build a K140 sub with one driver in a 57 litres ported box , tuned to 20 Hz combined with a electronic filter as published in "Luidsprekers fabels en feiten"
( That's Dutch for "loudspeakers Myths and facts" ) ISBN 90-70160-46-3 The electronic filter contains only three Op-Amps , 9 resistors and one capacitor and is based on the patented "ACE" principle by K.E.Stahl . I use the system for 4 years now, combined with a 150W RMS amp module in my Denon and Tannoy Home theatre and I'm still impressed with the stunning performance of this combinaton , down to 20 Hz - 3dB and loud enough for my 10 x 6 metres living room .

Happy converting ,
Cheers ,
Rens
Brisbane

That's amazing....20Hz @ -3dB with a K140 in a 2 cubic foot box!

Zilch
07-07-2006, 10:43 AM
We want the details! :D

[Patent number would be good....]

tomt
09-01-2011, 03:53 PM
http://translate.google.com/translate?hl=en&sl=nl&u=http://boeken.marktplaats.nl/techniek/473788844-geluidstechniek-luidsprekers-fabels-en-feiten-speakers.html&ei=yvtfTqTdB-fSiAL_kcTNDg&sa=X&oi=translate&ct=result&resnum=4&ved=0CDcQ7gEwAw&prev=/search%3Fq%3D%2522Luidsprekers%2Bfabels%2Ben%2Bfei ten%2522%26hl%3Den%26rls%3Dcom.microsoft:en-us%26prmd%3Divns


http://img198.imageshack.us/img198/1889/85804632luidsprekersfab.jpg (http://imageshack.us/photo/my-images/198/85804632luidsprekersfab.jpg/)

Eaulive
09-01-2011, 04:04 PM
That's amazing....20Hz @ -3dB with a K140 in a 2 cubic foot box!

If he has a low shelving filter that can give him 20dB boost starting at 50Hz.... it may work.
Although not very loud :D

Lee in Montreal
09-01-2011, 04:14 PM
I have on my shelves a Kef Kube 200. It is a Linkwitz transformer that adds about 24db at 10Hz. Just be carefull when you play film soundtracks. ;) But a lower level the sound is incredible. It transforms any decent speaker into a grunty subwoofer.

It does something like that.

Basic transformer
52717

Marchand WM8
52718

maxserg
09-01-2011, 07:17 PM
Never maid to be subs and won't play at medium to loud levels beleive me!:blink:

Tiger
12-16-2011, 08:08 AM
I recently discovered some old pa speakers my dad has are K140's. Checking them to see if they still worked I, noticed they were "pulling", instead of "pushing". The polarity is correct, I was just wondering if they were designed this way, or if there is a problem. I tried to find info online but I couldn't get any good answers. The two speakers are used in two seperate boxes as "mids" for his pa system. I hope some of the pros here can help.


Thanks

My bad I posted in the wrong topic...

Lee in Montreal
12-16-2011, 08:45 AM
While the universal norm was that the red post was positive,for reasons that evade me, JBL had decided at the time that the black one was the positive one. Therefore, if you use a battery with the + side into the black post, then the cone should more forward.

Tiger
12-16-2011, 10:37 AM
Aaahhh, that would explain it. Has JBL always done this with all their speakers past, and present?

Lee in Montreal
12-16-2011, 10:49 AM
Aaahhh, that would explain it. Has JBL always done this with all their speakers past, and present?

http://reconingspeakers.com/2010/06/jbl-reverse-polarity/

paragon
12-16-2011, 11:03 AM
;)

paragon
12-16-2011, 11:14 AM
On more :

Ruediger
12-16-2011, 11:27 AM
K. E. Stahl, “Synthesis of Loudspeaker Mechanical Parameters by Electrical Means: A New Method for Controlling Low-Frequency Loudspeaker Behavior,” Journal of The Audio Engineering Society, vol. 29, no. 9, pp. 587-596, (1981 Sept.).

Tiger
12-16-2011, 02:54 PM
http://reconingspeakers.com/2010/06/jbl-reverse-polarity/

Thats very informative. Now the next thing would be, should I continue to plug them in reverse (original), or should I go with the modern (push) method? Would there be any sound quality difference, and could it damage the speaker? Inside the cone on one of them theres a date of May 1982. I, assume they're both original, I'd hate to damage them after having them for so long.

paragon
12-17-2011, 01:23 PM
A method for extending bass response and lowering distortion in loudspeaker systems, which differs from both equalized and servo or feedback systems, is described. It can be seen as an extension of the technique to increase loudspeaker damping by giving the driving amplifier a negative output resistance. However, this method also controls the moving mass and compliance. Very good results, such as flat frequency response down to 20 Hz and excellent distortion data, have been achieved with moderately sized bass-reflex enclosures.

Eaulive
12-18-2011, 05:37 PM
Thats very informative. Now the next thing would be, should I continue to plug them in reverse (original), or should I go with the modern (push) method? Would there be any sound quality difference, and could it damage the speaker? Inside the cone on one of them theres a date of May 1982. I, assume they're both original, I'd hate to damage them after having them for so long.

Sound is AC so the speaker will be pushing and puliing alternately anyways. It changes nothing on the sound and it won't damage it if you connect it one way or the other, the thing is you have to get the proper polarity if you want to match this speaker in a multiple driver setup.

If you use only one driver, no difference, if you have two or more, then you want them to be "pushing and pulling" together, not one against the other. (it's really more complicated than that but you get the idea ;-)