Installing 15" Speaker in a Twin

Chris LeDrew · From: Canada

I plugged my Session 400 JBL speaker into my '71 Silverface Twin today (unplugging the two 12's), and the sound was unreal. I'm toying with the idea of putting the JBL in the Twin, and taking out the Oxfords which have now proven to be inferior in a big way. I like the Twin better than the Session, although the JBL kicks butt.
Anybody have any thoughts about this move? How hard is it to install a 15 in place of the 12's? I saw a recent sale here on the forum of a 15" baffle. I'm going to need one of those, I guess. Any other particulars? Anybody wanna talk me out of it?

Jon Light · From: Saugerties, NY

I certainly won't talk you out of it (although my own preference depends on what day of the week it is). The question of how hard/easy depends on whther the 2 X 12 baffle is screwed to cleats as in the early models or if it is dadoed & glued in, as in the later models. I forget what year the change was. The later ones present hassles, though not insurmountable. You can get a baffle made for reasonable $$--I suggest seeking out forum member Rick Johnson.
If you've got the JBL and you've got the itch, go for it. Right there is one of the classic steel sounds--Twin into a D130.

Darvin Willhoite · From: Roxton, Tx. USA

Here's pics of my Twin with a 15" JBL. This was done before I bought it, but if you have basic woodworking skills and patience, it shouldn't be too hard. This is a great sounding amp.

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Darvin Willhoite
Riva Ridge Recording

David Doggett · Posted 1 Mar 2006 6:51 pm

Putting a 15" JBL in a Twin converts it to a Vibrosonic. That tone is as good as it gets. However, the JBL is probably an 8 ohm speaker. The Vibrosonic was 8 ohms to match that speaker; but the Twin internal speaker jack is for 4 ohms. You will only get about 2/3 of the Twin volume with an 8 ohm speaker. If you want the full potential of the Twin, your options are: 1) to get an additional 15" 8 ohm speaker and run it in an extension cabinet (use a Y adaptor to run both 8 ohm speakers in parallel from the internal speaker jack for 4 ohms); 2) get an 8 ohm transformer; 3) get the speaker rewound to 4 ohms. It may work to plug another 8 ohm speaker into the external speaker jack - the external speaker jack ran in series or parallel in different model Fenders. There is also the possibility that the JBL in the Peavey is already 4 ohms, but I don't think so (check the specs).

The Twin is 100 watts, but a JBL 15 really only handles about 60 watts safely. If you are playing steel with a volume pedal, you are probably safe, because you will mostly be attacking notes with the volume pedal backed off a ways. But be aware that you can blow that speaker if you attack low notes with the volume pedal maxed out. Two JBLs can handle 120 watts, so are safe at any volume with that amp. Also, two JBL 15s will kick butt compared to any two 12s you put in that Twin.

Another option (Lloyd Green's solution, and my favorite) is to buy a head cabinet for the Twin chassis, and two 1x15 extention cabinets.

If the baffle is glued in, I wouldn't cut it out. That will ruin the resale value of the Twin, unless you sell it to another steeler. If you want to keep the combo configuration, get a custom 1x15 combo cabinet made, and save the original and speakers for resale.

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Student of the Steel: Zum uni, Fender tube amps, squareneck and roundneck resos, tenor sax, keyboards

[This message was edited by David Doggett on 01 March 2006 at 07:01 PM.]

Al Sato · From: Texas Hill Country

You can also buy baffle boards from a cabinet maker. For example, www.mojotone.com makes baffle boards. I think the one for the Twin that they stock is a 2x12 but they will do custom. I got a new baffle for my Deluxe Reverb from them.

Al

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So many stringed instruments, so little time...

Jon Graboff · From: Santa Fe, New Mexico

I got a baffle for my original '65 Twin cut for a single 15" speaker from Mojo guitar parts a while back. It had the bolts for mounting the speaker pre-installed and I had them attach the right style grille cloth at the same time. It was a beautiful job and the installation was a snap. It'll save you a lot of time and the results will look like the amp came from the factory that way.

Their web site doesn't list this job specifically but I called them and they knew just what I wanted.
http://www.mojomusicalsupply.com/cgi-bin/mojotone/

Henry Nagle · From: Santa Rosa, California

Look out.... In my experience a D130 can be pretty easily blown by a Twin.

Jack Stoner · From: Kansas City, MO

I converted the Twin I had to a 15" K130 (4 ohm model). Not a real big problem. Just have to make a new speaker baffle board and position the speaker so the transformers, etc do not touch. I got some Fender grill cloth and after it was done it looked "factory". Improved the Twin's sound for a steel 100%.

The baffle board is screwed in one some models (like the AB768 chassis model I had) and on other's (I think later models) the baffle board was glued on according to what has been posted here in the past.

Tim Whitlock · From: Colorado, USA

You may like the sound of the JBL even better, once you have it installed in the open-backed Twin. A closed back cabinet compresses the sound a bit, whereas the open backed cabinet allows it to spread out and you get that great 3-D Fender sound. The project can easily be done in a day, or even an afternoon, with basic woodworking skills (assuming you have the screw-in baffle). According to another thread on the same topic, 1/2" plywood is the material of choice, although I had great results with particle board. Careful positioning of the speaker (off center) is essential. You may find that your transformer just fits between the spokes. If you are careful, you can unstaple the grill cloth and peel it off the old baffle for use on the new one. Good luck!

thurlon hopper · From: Elizabethtown Pa. USA

Just put a JBL E-130 in my 1969 Twin and it souds really nice. I believe that although the D-130 has the sweeter sound, the E series has more power handling capability
The E-130 totally blows away the Pyle Driver that oi took out of the Twin. Right now i'm having a box made fotr a newly reconed Altec 416B, which is a 16 inch speaker. You will like the JBL much better than two 12's. TJH

Darvin Willhoite · From: Roxton, Tx. USA

The JBL in my Twin in the pictures above has been reconed with a 4 ohm kit. I use it very little and when I do use it, it is at low volume so I haven't had any problems with the speaker. I hear that a Black Widow sounds good with a Twin also, but I haven't tried one with mine.

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Darvin Willhoite
Riva Ridge Recording

Dave Van Allen · From: Doylestown, PA , US , Earth

the plan of mounting the speaker off center is wise-see the above picture...

My '68 Twin Reverb was fitted with a JBL D130f 15" before I got it... whoever did the job CENTERED the speaker... which makes for a VERY tight fit with the Transformer actually invading the space twixt the spokes of the speaker frame... if the speaker isn't turned "just so" it wouldn't fit at all... but it sounds great!

I have since installed a Weber California 15" 4 ohm ( a modern JBL style ) which gives me the correct impedance match,slightly more percieved volume and the peace of mind that I am not likely to blow the JBL-which I have since mounted in an old Fender closed-back 2x12 cab for whichI made my own 15 baffle.. I use that with my SF Vibrolux which sounds great for practice and is not powerful enough to kill the JBL.

The Weber has broken in nicely over the last couple of years of use... It is a very good "approximation" of the cleanness of the D130- but it still hasn't quite got the "mellow-roonie" that the contemporary (with the amp) JBL does after 30+ years in bars.

it's a classic sound!

Chris LeDrew · From: Canada

It has no distinctive markings that I can see, but I believe my JBL is a K130 according to past descriptions of that speaker here on the forum. It's just black and says "Peavy", model 70777022 and "James B Lansing Sound Inc." And it's 4 ohms. Sombody here once described this as the K130 found in a lot of the late 70's Sessions.

I'm no speaker expert. Is this correct?

David D., if this speaker is able to handle 200 watts in the Session, can't it handle 100 watts in the Twin?

Jon G., did you reinstall the original Fender logo on your new grill? If so, how'd you do it?

[This message was edited by Chris LeDrew on 02 March 2006 at 07:23 AM.]

Bill Terry · From: Bastrop, TX

David Doggett · Posted 2 Mar 2006 8:26 am

As Bill says, a JBL 15 cannot handle the 200 watts of a Session. They blew all the time. JBL refused to improve them for more power handling, and that's why Peavey developed the Black Widow (according to something I read by Harvey Peavey). Even the Weber California 15 copy of the JBL is rated at only 60 watts (80 watts for the ceramic model).

For pedal steel, you can get by with a JBL 15 (or Weber California) in a Session or Twin, IF you use a volume pedal, and always have it backed off around half or less as you attack notes (this is the normal way most steelers operate - you're cutting the amp to about 50 watts for attacks, and only approaching the full 100 watts for sustain as the string signal dies out). Even if the amp is cranked to 10, you will usually just be using that amplification to sustain your long notes. The only time your volume pedal will approach all the way down is when your string sustain is dieing off. If you ever get in a loud volume situation where your amp is dimed and your volume pedal is close to bumping as you attack your notes, the speaker is in serious danger.

Also, for technical reasons I don't fully understand, a 200 watt solid-state amp is not twice as loud as a 100 watt tube amp. My 135 watt '70s Twin was easily as loud as my 200 watt NV400. So I'm thinking a Session is only a couple of clicks louder than a 100 watt Twin.

The Twin was designed to play through TWO JBL 12s. Two of those can handle over 100 watts, and so are safe with a Twin. Likewise, two 15s are plenty safe. You can use one 15 up to moderate volume, and plug in a second one for loud volume. I use two JBL 15s in Marrs cabinets with my Dual Showman 100 watt head. For the occassionally really loud venue with no amp mikes, I use a 180 watt Super Twin Reverb (in a head cab) with those same two speakers. For that, my speakers are a little underated (about like a single JBL 15 with a regular Twin), but I feel safe, because of my use of the volume pedal, as explained above. I am aware I could blow the speakers if the amp is dimed and I am attacking notes with my volume pedal close to maximum - but then, I don't think I would want to be in the same room with that much volume from a Super Twin. I also have a single 4 ohm 15" Eminence rated at 200 watts (Fender put these in the 100 watt '90s Vibrasonics), that I can use with either amp head. But the JBLs sound better, and being able to aim two separate speakers gives more versatility for covering the odd shaped dives I play in.

So I'd say that if you use your volume pedal appropriately, you'll be fine with the one K130 up to moderate volumes. Beyond that, you need a second speaker.

[This message was edited by David Doggett on 02 March 2006 at 08:32 AM.]

Brad Sarno · From: St. Louis, MO USA

I believe that the frequent blowing of the D130's in the Session amps was the impetus to create the BW. If you notice, the BW 1501 is nearly an exact clone of the JBL's cone with the same sized voice coil and the identical curvillinear cone shape. But Peavey knew how to make the speaker more rugged and with a voice coil that could handle the heat. Actually, those early BW 1501's had much thinner paper and were more delicate than today's 1501 which more closely resembles the JBL E130 cone. The old spider web BW's sound real sweet and very much like a JBL, but they don't deliver or handle the power as well as today's BW's. The old Spider Web BW's sound great in a Twin. The new BW's sound great too, but with the thicker paper, they take a lot longer to break an and start singing. A brand new BW 1501 compared to one that's been played hard for a year or so sound like completely different speakers. But that's true too for a new JBL recone too. Really any speaker needs to break in.

Whoever came up with the user-replaceable basket for the BW is a total genius in my book.

Brad

David Doggett · Posted 2 Mar 2006 8:36 am

BTW, the black-face Twins (like Darwin's) and reissues are only about 85 watts, and so are a little safer with a single JBL than the silver-face Twins.

[This message was edited by David Doggett on 02 March 2006 at 08:37 AM.]

Bill Terry · From: Bastrop, TX

David,
Generally speaking, double the power and you get 3dB more SPL, that's why 200W doesn't necessarily seem that much louder than 100W.

David Doggett · Posted 2 Mar 2006 12:20 pm

Right, Bill, the different ways to measure power, volume and loudness perception can be confusing. When I said doubling, I meant like the difference between 5 and 10 on a linear volume knob (Fenders do not have linear volume knobs). The fact that a Twin is 100 watts, and a Session or NV400 is 200 watts, seems to indicate that a Session on 5 would sound as loud as a Twin on 10. That just isn't the case. A 100 watt Twin on 10 sounds like a Session on about 8 or 9. And a 135 watt Twin on 10 sounds as loud as a Session on 10. I have read explanations for this that have to do with relationships of various harmonics to fundamentals, etc., but I still don't understand it technically. I just know that in my experience, my 135 watt Twin sounded as loud as my 200 watt NV400. And my 180 watt Super Twin blows away the NV400. I would imaging the Super Twin would match a 300 watt NV1000. But I wouldn't want to be in the same room with either one of those on 10 - well, maybe if the room was a coliseum, and I was at the far end.

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Student of the Steel: Zum uni, Fender tube amps, squareneck and roundneck resos, tenor sax, keyboards

Jon Light · From: Saugerties, NY

Doesn't K130 handle more power than D130?

Mark Herrick · From: Bakersfield, CA

Spec sheets on "K" series...
http://www.jblpro.com/pub/obsolete/k_series.pdf

And "E" series...
http://www.jblpro.com/pub/components/eseries.pdf

I think, and I may be wrong, but wasn't the original design the D-1XX and then came the D-1XX-F with a wider voice coil gap and better power handling, then the "K" series which had (maybe) a different surround but essentially the same specs, then the "E" series with a ceramic magnet and even higher power handling capabilities...

And I got a kick out of this:

Chris LeDrew · From: Canada

Glad you got a kick out of that, Mark. "Unreal" must be regional slang for "wicked".

What type of JBL is this?

Mark Herrick · From: Bakersfield, CA

I bought the same JBL/Peavey speaker recently. It is the equivalent of the K-130. The JBL-labeled K-130 has the same black magnet cover with a round aluminum label...

I believe the one I have is in my storage locker at the moment, but if I can get to it and check the model number I'll post it on this thread.

One thing to note, because the Vibrasonic had the 15" speaker I believe the cabinet was actually a little taller. (At least it is on the '90s era Custom Vibrasonic I have.) I happened to find a brand new cabinet for a '65 Twin Custom 15 for sale here on the Forum and put my '74 Silverface chassis and the JBL K-130 speaker in that. Fits perfectly!

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[This message was edited by Mark Herrick on 02 March 2006 at 06:16 PM.]

Chris LeDrew · From: Canada

Thanks, Mark. Sounds like you have a nice rig.

Marlin Smoot · From: Kansas

Chris,
With all due respect; I would leave your 1971 Fender Twin as is and put the 15 back into the Session. For the reasons you stated...it should give you a very good reason to buy another amp!

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