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Charley Rummel
09-06-2003, 03:10 PM
Hi, Everyone:

As you fellow L65 owners may know, the duct tube on this enclosure isn't straight like other models, but instead, folds in such a way that the inside end directly faces the rear of the low frequency driver cone.

Does anyone know what the advantages of this design are, as opposed to a traditional straight duct tube?

Regards,
Charley Rummel

boputnam
09-06-2003, 03:26 PM
Originally posted by Charley Rummel
... the L65 duct tube ... isn't straight like other models, but instead, folds in such a way that the inside end directly faces the rear of the low frequency driver cone.

Does anyone know what the advantages of this design are, as opposed to a traditional straight duct tube? He, Charley...

Working on a near-copy of the L65's today myself.

First, there is a need to keep the rear-end of the duct at minimum 3-in off the cabinet back.

¿What is the port diameter?

¿What is the length of the duct, up-to the bend, and entire length with the bend?

¿What is the cabinet depth? Outer dimension is 13-1/8 in, right? So inner would be at most 11-5/8 in, maybe less.

boputnam
09-06-2003, 03:29 PM
Hey...

Also, which copy of the L65 is that? i.e., which network and woofer?

If it's the N65 and the 126A LF, I would trade a six-pack of Heinekens for a quick polarity test of the woofer... :yes:

Pretty Please? :)

Charley Rummel
09-06-2003, 05:11 PM
Hey, Bo:

Thanks for your reply; it makes a lot of sense. It's the version with the 126A woofer/N65 crossover network.

I like my Heineken ice cold from a chilled stein, served from the 12oz. bottle. Be sure to bring at least a 12-pack. So, what are you going to have???

Regards,
Charley

boputnam
09-06-2003, 06:10 PM
Originally posted by Charley Rummel
It's the version with the 126A woofer/N65 crossover network. Have you been able to do a polarity check? Even a quick 9-volt to the terminals would add THREE MORE six-packs to that commitment! I'm good for a WHOLE CASE SHIPPED TO YOUR DOOR for the polarity of that 126A....

Truly! :yes: :yes:

Robh3606
09-06-2003, 10:27 PM
Bo for what its worth the 122a in the L-65A is negative ie + to Red = Inward travel.

The 129H in the L65B is also negative compared to the now established norm.

All we need is the 126 info and we have them all :bouncy:

And if he gets a case what's my take???


Rob:)

boputnam
09-07-2003, 12:32 AM
Originally posted by Robh3606
All we need is the 126 info and we have them all :bouncy:

And if he gets a case what's my take??? Man if ANYBODY can get me this, I'll share plenty cases of Heineken! This is not so tough a question, but being so very close, I fear will reward with nothing.

Come on, Charley! I'll be so very appreciative!

Robh - your post is incredibly helpful :thmbsup: and inferentially suggest the 126A to be POSITIVE, since both the latter series N65 networks (thanks to Giskard!!) reversed the connection to the LF (they went to Red Binding post to GRN wire). All this assumes, of course that JBL did not decide to alter the inner-cabinet phasing. Possibly they did, but not likely.

In the absence of confirmation :mad: , I'm going with my deduction, which means that to honor the L65/N65 factory phasing, the LE14A I'm using with the N65 network needs be hooked-up reverse (GRN to Black LF terminal), making the cabinet:

HF (-)
MF (+)
LF (-)

*****

NB: In Orwellian style, I posthumously edited the attachment to include the note about the POSITIVE polarity of the 126A, due to it's importance to the Archives. :)

Robh3606
09-07-2003, 08:36 AM
Hey Bo

Which crossover are you using??

Rob:)

Charley Rummel
09-07-2003, 11:26 AM
Hi, everyone:

I don't mean to keep y'all in suspense:D ,but I have a busy day today. However, I'll see if I can get to testing one of them later this evening.

Regards,
Charley

John B
09-07-2003, 12:08 PM
I just checked 122A and 128H both moved negative, 126A moved positive. Surprised me, made me thirsty too!

boputnam
09-07-2003, 12:10 PM
Originally posted by Robh3606
Which crossover are you using?? The first "variant", the N65.


Originally posted by Charley Rummel
I'll see if I can get to testing one of them later this evening. :nutz: :dancin:

Robh3606
09-07-2003, 12:58 PM
What I always do is put a positive voltage on the Red + and then call it from there. Just trying to keep to the current standard. I think most people use this as the norm and to go JBL'S way + on Black just confusses the issue. A list sounds like a good idea we can add to the Polarity list that JBL Pro has.

Rob:)

Charley Rummel
09-07-2003, 05:40 PM
Aw, gee! I come back to the forum and somebody beat me to it!:(

I checked the 126A in one of my L65's and also got Positive to Red Terminal moves the cone outward, to confirm John B's findings.

Well, John B, enjoy your Heineken! :banghead:

Regards,
Charley

DavidF
09-07-2003, 07:16 PM
Does anyone know what the advantages of this design are, as opposed to a traditional straight duct tube?

_______________________________________________

There has to be some amount of change to the port effect because the airflow is having to push aroung the bend. Audible? Probably not. This is common where the straight port does not fit the dimensions of the box. The alternative is to narrow the diameter which will bring on some audible effects at high air pressures.

DavidF

4313B
09-07-2003, 07:34 PM
"Does anyone know what the advantages of this design are, as opposed to a traditional straight duct tube?"

http://www.lansingheritage.org/html/jbl/plans/1979-manual.htm

http://www.lansingheritage.org/images/jbl/plans/1979-manual/page30.jpg

http://www.lansingheritage.org/images/jbl/plans/1979-manual/page31.jpg

boputnam
09-07-2003, 07:39 PM
Originally posted by John B
I just checked 122A and 128H both moved negative, 126A moved positive. Surprised me, made me thirsty too! Whoa... Somehow, our posts crossed in the ether, and I totally missed this.

Well, as I suspected, and suggested by the schematic variants that Giskard originally posted.

So let's all remember, the 123A and 126A are both positive, contrary to JBL convention. There yet may be others lurking out there...

THAT is incredibly helpful to me. Thanks! Anybody needs Heinekens, pm me your emaill address, and I'll PayPal the due.

:cheers: