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Topic: Is there some way to limit the signal going to a speaker? |
Ethan Shaw
From:
Texas, USA
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Posted 17 Aug 2009 12:03 pm |
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I have a Fender Super Six that Red Rhodes chopped and put a 15" JBL in. It sounds amazing with that combination, but both the previous owner and I "froze" the speaker when we played some loud low notes on C6. (The repair guy said the middle of the speaker is stuck.)
Is there anything that would be easy to do that would act as a limiter between the amp and the speaker (that would preserve the tone of the amp)? I've tried running it with a Black Widow, but I'd really love to put the JBL back in there.
Alternately, is it possible to get the JBL reconed for a higer wattage, and will that affect the sound? |
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Jon Light (deceased)
From:
Saugerties, NY
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Posted 17 Aug 2009 2:09 pm Re: Is there some way to limit the signal going to a speaker
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| Ethan Shaw wrote: |
| Is there some way to limit the signal going to a speaker? |
A tube amp is very dependent on having the proper load on the output transformer. So the answer to your question is 'yes' but it can't just be a pot. There are speaker attenuators of various types that will reduce the signal to the speakers by substituting something else in the output path to simulate the resistance of a speaker---either big honking high-watt resistors or other more interactive methods.
Here's a place to learn a bit and to see a selection of options.
http://www.tedweber.com/atten.htm
Of course Weber is not the only attenuator option. There are a couple of other highly regarded ones. Not cheap.
Another option is......a Weber neo speaker that is modeled after the JBL. Its wattage rating is right on the edge---I've heard that it can handle it (without blowing up) but I've also heard that it has trouble handling loud clean steel. And yet another option is an Eminence Commonwealth----this was designed after the JBL and is rated for something like 200W---this is the Fender Steel King speaker. I've got one in a cab and so far I like it although I haven't put it through enough paces to outright recommend it yet. It is my preferred choice in the Steel King after trying a couple of others (including a BW.)
Personally, given that the attenuator is another thing to carry, I'd rather spend the time & money looking for the right speaker. And btw, yes, the JBL can be reconed as a hardier speaker but I don't know enough to say more....someone else can chime in.
-----edited for spelling
Last edited by Jon Light (deceased) on 17 Aug 2009 3:38 pm; edited 1 time in total |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 17 Aug 2009 3:10 pm
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| I stopped using JBL's for that reason. (They just won't take low-end punishment.) Get an EV-SRO15, or an EVM15. They have the dynamics of a JBL, but will handle a lot more power. |
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Rich Hlaves
From:
Wildomar, California, USA
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Posted 17 Aug 2009 3:25 pm
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I agree totally with Donny. Although I like the sound of JBLs, they can be fragile. I have twice cooked a pair of E120s in a Twin Reverb. I used a pair of Weber NEOs in my Showman so far with good results. I have never lost an EV in anything.
There is also something about the TR, Showman Reverb, Quad and Super 6 (all the same basic chassis) that JBLs don't like. Someday I'll figure that one out. My output tranny checks out as does the PT so I don't think it was DC to the output. I have C12N Jensens in it now that have seen harder use without failure.
Rich |
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chas smith R.I.P.
From:
Encino, CA, USA
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Posted 17 Aug 2009 4:55 pm
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Between the amp and the speaker, try a THD Hot plate:
http://www.thdelectronics.com/product_page_hotplate.html
I have one between my THD Sig:X and the speaker cabinet, so I can be in the same room when it's "cranked".
They come in different colors according to the resistance, mine's purple for 8Ω. They're not cheap, but you can find them on E-Bay. |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 17 Aug 2009 4:57 pm
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An attenuator will not solve this problem. It will merely cut your amp volume down. To get back to the playing volume you want, you will have to turn the amp up and/or stomp your volume pedal, and the speaker will distort or blow at the same speaker volume as before.
Twins and Duals were designed for two speakers (thus their names). If you want to use JBLs or JBL clones like Weber Neos (which handle about the same 60 watts apiece), you need to use two of them, whether you are using 12s or 15s. A Twin or Dual sounds glorious through two JBL 15s. And I have used two of them with my 180 watt Super Twin head with no problems (at least for pedal steel with a volume pedal).
The other solution is to use a single heavy duty speaker such as a Black Widow or Eminence. The sound is not quite as warm at low volumes, but is great at higher volumes.
Attenuators are designed to allow you to drive a tube amp to distortion at lower volumes. All they do is cut the volume going from the amp to the speaker. To get back to the same playing volume, you have to drive the amp and the speaker harder. |
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Ethan Shaw
From:
Texas, USA
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Posted 17 Aug 2009 5:08 pm
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| thanks for the replies--all good ideas. Just for further information, how good of an option is it to get the JBL reconed for a high wattage? Also, David, what you're saying makes sense, but wouldn't it be similar if you're running two lower-powered speakers or one higher-powered one? |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 17 Aug 2009 5:59 pm
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| Ethan Shaw wrote: |
| ...how good of an option is it to get the JBL reconed for a high wattage? |
Can you get a JBL "reconed" for higher wattage? Seems like that would require a complete redesign, probably altering not only the voice coil, but the cone material and shape, and the way it is attached to the frame. It wouldn't necessarily sound the same. You are better off buying a heavy duty speaker like a Black Widow or Eminence that is designed to sound similar.
| Ethan Shaw wrote: |
| ...wouldn't it be similar if you're running two lower-powered speakers or one higher-powered one? |
| David Doggett wrote: |
| The other solution is to use a single heavy duty speaker such as a Black Widow or Eminence. The sound is not quite as warm at low volumes, but is great at higher volumes. |
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Jim Dickinson
From:
Washington, USA
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Posted 18 Aug 2009 5:50 pm
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Yes, you can get a JBL reconed with higher power internals, especially the voice coils. They are made by Precision Coil Winding and marketed through MWA speaker repair. The Precision coils use voice coil supports and voice coils that will handle much more power and higher temperature before failing. The original JBLs were made with Kraft paper voice coil supports, held together with an equivalent of Duco cement and/or Bostik shoe glue. Modern voice coil supports are either made out of Kapton or nigh temperature fiberglass and Precision Coil uses a proprietary very high temperature glue. The Webers, Eminences, Peavey's etc. handle a lot of power because they use similar components. The Steel King speaker is quite similar to the JBL D130 internally, except for the use of the better glues in assembly.
However, all of the above drivers, with the exception of the Weber, which uses a JBL like cone, have a higher compliance cone surround (hinge) than the original D130. The D130 gooped paper roll surround will not allow the cone to move as far as the others and in very high power situations with lots of lower frequency excursion, this could be a factor. The Jerry Hubbard designed Steel King speaker took that into account and has a stiff linen surround that will allow more movement than the paper rolls of the JBL, while still keeping that D130 sound. If one is not really whacking it, a JBL reconed with new high power parts ought to work fine. Now there are those who claim to be able to hear grass grow, that will vehemently assert that nothing sounds like the original. I say BS, if the voice coil winding lengths, cone and other software is the same, it will sound the same, there is no magic in kraft paper and solvent based glues.
Now, MWA does not always get everything right, for example their 15" Altec repair kit is the same regardless of the driver's model or use. Their D130 kit is really close to the original in format. In some speakers, one has to recone them as you can, there are no original like parts.
Jim |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Lynn Oliver
From:
Redmond, Washington USA * R.I.P.
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Posted 18 Aug 2009 8:41 pm
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| Since nobody else mentioned it, there are speaker protection circuits around. A search will bring up both DIY designs as well as commercial products. |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 19 Aug 2009 1:17 pm
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Yeah, but my problem is that I don't want any punches held by a protection circuit. I want to hear all the volume of that E power chord that's gonna blow a single JBL.  |
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Jim Dickinson
From:
Washington, USA
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Posted 19 Aug 2009 10:32 pm
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| Then there is always the dreaded light bulb. Some limiting circuits used a light bulb in series with the speaker. Simply, at lower power levels, the light bulb acts as a simple reistor, as the power increases, the bulb filiment begins to heat up and as it does, the resistance increses, limiting the power to the speaker. If you really stoke it, the bulb lights, using up some of the power making light and further increasing the resistance to the speaker. Sometimes these things act as a crude compressor, they can really play hob with your dynamics. The bulbs are special bulbs built just for this although I knew one guy who used a car headlight bulb. Nasty things. Jim |
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