There's some information here:
http://www.audioheritage.org/vbullet...ead.php?t=7991
There's some information here:
http://www.audioheritage.org/vbullet...ead.php?t=7991
Wow, what an incredible thread.
I am also restoring a Quad Reverb, a decided to have the (4) original oxford speakers reconed. I did see a Quad with D120Fs in it, but the thing was so heavy it took a hand truck to move it. Four E120s would add another 24 lbs to the mix.
My Quad Reverb has but one pair of secondary windings on the original output transformer. If you go with D120s, or D131s, be sure to get 16 ohm edgewound aluminum voicecoils so that four in parallel yield 4 ohms. 8 ohm voicecoils will yield 2 ohms that will stress your output tranny.
Also, check the baffleboard on your Quad. It is just 0.5" pressboard and mine was cracked in about six places. The load from four heavy speakers will certainly be higher.
I have D131s in my Twin Reverb and love them. Tried D123s and did not like the sound from a low-excursion driver.
As for the Blonde Showman - they originally came with a single D120 mounted in a tone ring. This is the rarest cabinet. Later, a single D130 was mounted in a tone ring, followed by the Dual Showman having a pair of D130s without tone rings.
For my kid, I am building a Blonde Showman combo using a 1968 chassis rewired to 6G14 spec feeding a D130F reconed to 4 ohms.
... watchman
Thanks Don! This site can be a little intimidating with all the articles/threads to search. For example, if I didn't type the right phrase or word in the search field then I might not have gotten the above thread. Thank you!Originally Posted by Don C
However, I still didn't see mentioned what I had hoped, what I need, which is the stuff that JBL used to dope their D131's (as one of the two things that were done to make them into D120's/120F's). What was mentioned was only the GE weather strip sealer or the PVA used by Electrovoice for cloth or foam surrounds as recommended to dope the 2205's. The speakers I would be doping are the JBL D131's and I believe the surrounds are paper, no? Also, the there was a PVA recommended for a "band-aid fix" mentioned which was elmer's glue diluted (mixed) with warm water.
Rick
A more correct doping material is #AA-75, from Waldom. It's "gooey", and stays somewhat sticky, pretty much forever. It won't overly stiffen the surrounds (in fact, it doesn't have much of a bending modulus whatsoever, so it really won't change the parameters at all, in any significant sense), and it's more permanent (ie, won't run/creep) than the Altec "goop".
Many reconing shops carry Waldom AA-75... it should be possible to get someone to treat the paper edges, in most metro areas.
Regards,
Gordon.
Usually something with the word reproduction in it will attract more attention than a thread that includes JBL's but not limited to JBL's being the final goal.
Where did you see a Quad with 4 JBL D120's? I was looking for that.
I've been advised by the guy I use as an amp technician here locally that the final speaker load in a fender quad reverb should equal 4 ohms. That's all the output transformer of the quad needs to do is match that. So in order to do that you should use 4x16 ohm speakers. And, he went on to say that the tube amps have less tolerance for output transformer/speaker load mismatching than solid state amplifiers. So I'll have to ask him why and get back to the group on it if it's worth getting back to the group on that, because that's opposite to what's been stated by at least a couple of group members so far - that tube amps are MORE tolerant of impedence mismatching than are transistor amps. He said tube amps are more forgiving for impedence mismatching where speaker impedences are too low for the output transformer than speaker impedences that are too high for the output transformer, and that the latter are more likely to overwork the tubes.
I'm not sure if I've already stated this in this thread, but I'm trying to go stereo with my dual showman reverb and the quad, but I'm not sure if I should be using a feder pro instead of the fender quad. Can anybody make a positive identification of the small amp on top of the extension speaker cabinet in the background on stage in the Yessongs video? And is the cabinet a 2x12" or a 2x15"?
Rick
Hey Rick,
I saw a 4xE120 Quad Reverb at a friends house. He took the four JBLs from a Fender transistor amp (Libra?) and bolted them into his QR. Talk about loud!
The impedance of the speaker should match the output transformer. For a QR, you get 4 ohms from 4x16 ohm speakers in parallel. For tube amps, you can always put a higher impedance speaker, with a corresponding reduction in power.
Tube amps have a problem in the other direction. 4x8 ohm speakers would have yield a 2 ohm load that would draw 1.4x the current (Power = I^2*R) to produce the same power (100W). This stresses the output transformer, which is old to begin with.
As for your stereo amps, the QR, Twin Reverb and Dual Showman Reverb all use identical circuits with 4x6L6GC tubes and 4 ohm output transformers. The Dual Showman Reverb cabinets were all 2x15" and 2x8 ohms for 4 ohm impedance.
The early blond showman amps were 8 ohms, and the double showman used a pair of 16 ohm 15" D130F speakers to get 8 ohms. The single cabinets had either an 8 ohm D120F or an 8 ohm D130F. Clever, huh?
The Fender Pro Reverb and Super Reverb would work in a stereo setup because they use identical 2x6L6GC circuits, but produce only half the power of the QR.
The QR is louder than the TR or Showman, and the Super Reverb is louder than the Pro. Do some math on the cone area of the 4 speakers vs. two and you will realize they move a lot more air.
... watchman
BTW - I am en engineer, not an amp tech.
And yet there was suppossed to be someone here on the forum who had once posted where one would be able to get a hold of the original goop that JBL used to dope their D120's/130's.
Rick
If you're referring to Airflex 510, it's no longer available, unless you can find some old stock on a shelf somewhere. It was made by Air Products. The Waldom dope referred to above is the closest substitute I'm aware of.
Dear Sirs,
This thread is getting silly.
Get out there and find 4 k-120 baskets and have them reconed with a current C16RE120 kit and let that Fender RIP your head off!!!
If not that...find 2202 baskets, which are always cheaper on ebay, and have them reconed as E-120s.
There is always another way to skin a cat.
As far the man on ebay with the reproduction foilcals, who cares. The white pencil marking on the cone from the person who glued it in is what is really important.
Willing to go out on a limb...for a second.
Scott.
Fine. I'll sell white pencils to guitar heads.
Maybe a little "Upgrade Kit."
Soon "F" will simply mean "Fraudulent."
I THINK we're here to PRESERVE the legacy....
That way my understanding, otherwise we would be faux-Lansing Heritage
Our esteemed colleague from SMKSoundPro ovbiously has not read very deep into the thread, where we discussed concerns with weight. Here is a hint: 4 E110 or K110 baskets sitting on a 1/2" of pressboard dado-d 1/8" and glued into the pint cabinet sounds great until it gets dropped.
Well, now we know where those silly pencil marks are coming from
... watchman
Again, as always with me, these should be fairly simple, straightforward questions - If I were to buy D131's and then dope their surrounds with Waldom AA-75, and also wire it up with a D131F which I presume is a D131 with a surround that has been doped with Airflex 510, would there sonically be a noticeable difference between the two speakers - the one speaker doped with one brand and the other speaker doped with the other brand?
Is it correct to say that the D131F is identical to the D131 except that it has been doped and with Airflex 510?
The gentleman from Standel has told me that doping the surround of a D131/120/130 changes the sound quite a bit as well as increasing the power handling because doping the surround stiffens the paper cone thereby changing the speaker's frequency characteristics. Because of this information as I have been told, I was thinking of doping the surrounds of my JBL single ring recone D120 (1957/58) reproductions. I had better check first with the reconer on this before even considering this.
Rick
Rick,
I understand your frustration, but I can't give the answer you seek, because I don't know it. I posted the reference to Airflex 510 because I knew it to be a preferred doping compound for a long time, though I doubt that it was available in '57-58, or that it was the compound originally used at that time. I also doubt that whatever dope was originally used (if known) is still available today. It's kind of like trying to match paint used back then, in that there's none of the original product around anymore, so the best we can do is get a close match.
Doping a surround does not increase power handling, as that is a function of the heat tolerance and breakdown temperature of the voice coil. Nor does doping a surround stiffen the cone, as it only alters the area it's applied to (the surround). It could however, alter the tone of a speaker by damping edge or rim resonances, in which case it would produce less distortion, or a 'cleaner' sound. Doping is also a permanent modification, once applied, there's no going back.
The characteristics we often find desireable in many classic instrument speakers ARE their distortion products, whether from cone breakup, rim resonances, or otherwise. Personally, I think it's highly unlikely that anyone can EXACTLY duplicate the sound of any 50 year old speaker when it was new. If you're a musician, find a tone you're happy with and go with it. If you're a collector.....well....they don't care what it sounds like anyway, as long as it's 'original'.
I am greatly sorry if I offended anyone by my earlier post.
Certainly, I am OUTRAGED that someone would sell aftermarket foilcals! I saw a pair listed on ebay that I would guess, the seller is part of this esteemed forum group.
My point was/is: That in the recone shop, we tore off foilcals, then reconed the basket into something else, then used our white pencil on the back of the cone to denote the cone kit installed. We were never naive enough to believe a guitar player knew more about the subtle differences of 12" JBL speakers.
This may seem like a harsh statement, but please believe that I found it to be the case on more than one occasion!
We had guys walk in not knowing a celestion greenback from a k120! Its as if they were just following some suggestion they found somewhere else. A friend, magazine article, or a new found buzzword.
Please accept my apology, and don't ever take away my white pencil!
Scott.
I think "doping" is probably a misleading term. The "goop" we used was a super high viscosity oil. It worked well to damp out any ringing from the edge of the cone. It was basically used on the D123 to seal the cloth surround without stiffening the surround.
No, that's not correct. The "F" series had the top plate opened slightly, to prevent rubbing and shorting in the coil from frame warpage.Is it correct to say that the D131F is identical to the D131 except that it has been doped and with Airflex 510?
The gentleman from Standel is incorrect. Coating the surround (correctly) neither increases the power handling nor does it stiffen the surround. The D120F is almost absolutely identical to the D131; the D130F is almost absolutely identical to the D130.The gentleman from Standel has told me that doping the surround of a D131/120/130 changes the sound quite a bit as well as increasing the power handling because doping the surround stiffens the paper cone thereby changing the speaker's frequency characteristics. Because of this information as I have been told, I was thinking of doping the surrounds of my JBL single ring recone D120 (1957/58) reproductions. I had better check first with the reconer on this before even considering this.
Rick
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