LE14A magnet type

[Donald]

If my late 70's L222 LE14A are alnico, should I see about getting them re-gaussed? If I still can?

Bass response has changed. For lack of a better description, they can't take it. It is almost like the magnet is weak and lets the voice coil push/pull to an extreme point. They were re-foamed by OC Speaker 2 years ago. As were the PR15c.

Another question. Based on a pic I sent to him of the PR BEFORE I sent it for new foam, Steve G says they are missing the tuning discs. I just pulled one out of the cab. There are no extra discs mounted. To determine how much weight to use requires knowing the cube of the box. Since the L222 cross-section is a trapezoid the area is h/2 (b1 + b2). H = 13", b1 = 18" and b2 = 12". I calc 192 sq inches. The height of the bass box is 32.5". Times the area gives 6337.5 cubic inches. Divided by 1728 cubic inches in a cubic foot I get 3.66 cubic feet for the L222 bass box. Using the latest chart posted by Giskard (and rounding to 4 cubic feet, I should have 3 20g discs mounted.

Am I off base here? I assume a 60g metal disc would also work?

[Zilch]

PR15C:

[Donald]

The same but different. :-)

[Zilch]

Allegedly, factory tuning of L222 vs. L220 was done with the PR damping discs. I don't know which was intended to have fewer.

BUT, we now have two example L222's with no discs. I doubt that anybody "messed" with mine. They just cranked them until they smoked.

Early "assembled" Olympus came with instructions for tuning to taste by changing the number of discs. Perhaps the info is in the library here....

[4313B]

Some distant memory tells me the L222 didn't have any discs.
I know the L220 had the discs, I just can't remember how many.

[Steve Gonzales]

I am very puzzled at by this!, Don's L222's have LE14a's and a PR15 and no disc's and Giskard has some with LE14-H's(?), yet both are tuned without disc's!. We know that the internal volume is the same in both the 220 and 222 so why did JBL tune a L220 that had the LE14A with 2 100gram metal discs and then use the exact same drivers/internal vol and tune the early 222 with no discs at all?. All I can say is that Don seemed to like the performance of my 220's and 222's when he visited and they are both tuned with 2 100 gram metal discs. I removed the discs to hear what difference it made and the LACK of weighs caused both the LE14A and H's to flop around and bottom out. I wonder if this is what is happening to Don? I would make some weights out of metal and mock-up several values. The fiber discs are 20grams and the metal 100grams. I know with absolute certainty that the L220 was tuned with 2 metal discs as I have 2 pairs of them and they were untouched and also have a friend in Mich. who has L220's with LE14A's that are tuned with 2 metal discs. So Don, what you have is really an L220 set-up. I hope this helps you out.

[4313B]

Just to clear things up a little bit here. The L220 and L222 used the LE14A. The L220A and L222A used the LE14H when JBL moved from AlNiCo to SFG Ferrite in 1979-80.

I know for a fact the L222 was tuned higher to yield greater thump. I just can't remember the exact disc arrangement. Like I've posted before, two metal discs seem awfully heavy for the PR15C but that doesn't mean JBL didn't use them.

[4313B]

Ok, I'm wrong.

No discs would tune the ~ 4.2 cubic foot volume (system losses) to ~ 40 Hz and the two metal discs would tune the ~ 4.2 cu ft volume to ~ 26 Hz which sounds right.

[Zilch]

This disc-ussion is starting to make sense, now.

From the revised 1973 version of "Installation and Use of JBL Passive Radiators:"

"The tuning instructions should be used as a guide for best overall performance. However, you can experiment if you wish and use the number of discs which gives best performance in your particular installation ... using fewer discs will give stronger mid-bass at the expense of the very lowest tones."

SOOOO, if you want "punchier" bass (L222), remove discs. If you want "extended" bass (L220), add a cuppla fender washers.

I know some folks consider PR's to be crap, and the forum has probably debated them exhaustively. But from this discussion, they appear to have considerable utility as tools in the tuning arsenal here.

Altec literature had something to say about them, as well. Maybe I should pay more attention....

[4313B]

"I know some folks consider PR's to be crap, and the forum has probably debated them exhaustively."

I thought they were quite neat in the Lancer 44 and Lancer 77. That's pretty much where my interest in them for personal use ends.

[Steve Gonzales]

wow, I just cannot imagine what would make someone say that a passive is crap? I get such a wonderful, punchy low end respone that I am sold out to the idea. I have heard L300's and they don't seem to have much of an advantage if any over the LE14/PR15 set up in my L222/220's. opinions are like as*holes, everyone has one and most of them stink but I consider the 136A to be the best LF driver JBL made for use in a fullrange system but again I don't feel like like I am missing anything, if at all. I know the 2245 and 2235's are excellent too but I'll stick with the 136A. I realize room gain has alot to do with low end response and if anything my small room suffers from cancellation, but I can shake the house if I want to with the clean musical low end I get from this combination.

[Donald]

Well, the PR conversation is going well.

What about getting my LE14A de-re-gaussed? Does JBL still do it?

[Mr. Widget]

Yes.

I would go to Orange County Speaker. They charge $25 per woofer. They will do it while you wait.

http://www.speakerrepair.com/

Widget

[4313B]

"wow, I just cannot imagine what would make someone say that a passive is crap?"

I've heard a few people refer to them as crap, among other things. Who cares?

"I have heard L300's and they don't seem to have much of an advantage if any over the LE14/PR15 set up in my L222/220's."

The 136/2231 was a bit more efficient, could handle a bit more power from a mechanical perspective, and could move a bit more air than the LE14. It was the right choice for the 43xx Studio Monitors although the LE14 was generally considered to be the more "accurate" transducer.

"I consider the 136A to be the best LF driver JBL made for use in a fullrange system but again I don't feel like like I am missing anything, if at all."

Ok. I personally think it's great you like the L220's and L222's.

"I know the 2245 and 2235's are excellent too but I'll stick with the 136A."

Tough to do since the C8R2231 recone kit for the 136/2231 was discontinued and replaced by the C8R2235 many, many years ago.

[Steve Gonzales]

I am still amazed at the wealth of info here. I have a friend in NY that has 4 original 136A's, I better snap up a pair. I want Don to let us know how the re-gauss goes.