Replacing a speaker with a capacitor

[white.space]

I have a '57 Tweed Twin reissue. A friend who is savvy with amps I could try wiring a capacitor with the same value (50w, 8ohms) in place of one of the speakers to reduce output volume.
Anyone have thoughts on this?

I conducted a fruitless search for this topic in the forum, so if it's been covered, I apologize.

 

[rockon1]

That would be a resistor not capacitor. Its a "dummy" load and not exactly the same as a speaker. It should work but it will also get hot. Bob

 

[Guinness Lad]

Resistors dissapate energy in the form of heat. If I was to guess I would think a speaker would be roughly the same capacity as a 50 watt resistor, which would be huge. I tiny resistor would probably just burn up, but I have never done this.

 

[WesKuhnley]

Please replace one of your speakers with a cap and post pictures of the results....

Just kidding.

Just a little tip here: if you don't know the difference between a resistor and cap, you shouldn't be replacing anything in your amp with anything else. That will lead to expensive repair bills.

 

[white.space]

forgive my mistake, i do know the difference and have worked on my own amps successfully.
i've been meaning to post this question for a while, for more opinions, and waited until the end of a lonnnng work day to do so.

 

[rockon1]

Resistors dissapate energy in the form of heat. If I was to guess I would think a speaker would be roughly the same capacity as a 50 watt resistor, which would be huge. I tiny resistor would probably just burn up, but I have never done this.

Yeah it would be.

 

[doctorx]

Ok. Back away from the amp, and keep your hands where we can see them.

Adding a resistor or a capacitor like this is not a good idea. If you want lower volume, use an attenuator.

 

[mike shaw]

Why not attach a suitable power resistor to your etension speaker jack? That'll cut your power by half right there.

 

[hasserl]

Yeah it would be.

Actually that is probably about a 200 watt resistor, 50 watt resistors are not that uncommon.

Here's one from Mouser.com

Part # 71-RH0508R000FE02 $3.76

Note that it will effect the tone of the amp, it is not totally transparent. I believe Aiken has a paper on this on his site.

 

[WesKuhnley]

Why not attach a suitable power resistor to your etension speaker jack? That'll cut your power by half right there.

If you wish to maintain a load that remotely resembles the two speakers together, you must replace one with a resistor. Otherwise you'll change the refected primary impedence and in many instances, that's not a good thing.

 

[RocksOff]

Pull one of the speakers, have your buddy rewire the speakers and plug into the proper impedance output?

 

[walterw]

that just puts the full amp power into one speaker instead of two. (it will be a little quieter, though.)

the resistor idea is no good because it's not a reactive load like a speaker, meaning it's the same resistance at every frequency, unlike speakers.

therefore, at some frequencies it will be a lower impedance than its companion speaker while at others it will be higher; this means it will either take volume from the speaker or leave more volume for it at a totally different set of frequencies than the speaker normally creates, changing its tone.

 

[white.space]

thanks for the input, fellas, much appreciated!
i'm getting that this isn't something that was figured out decades ago as a simple multi-speaker amp-quieting solution. on that tip, if someone hadn't already done it successfully, spreading the idea to other bros with loud combo amps over the years, it's probably not a real good idea. i love my amp, it's just really loud. the sonic spread is incredible on stage, despite its acceptable band-practice volume. so i don't want to fry the Mercury OT or anything. Just wanted some ideas on this hypothesis.
if anyone wants to keep chiming in, more input is more than welcome.

 

[hasserl]

thanks for the input, fellas, much appreciated!
i'm getting that this isn't something that was figured out decades ago as a simple multi-speaker amp-quieting solution. on that tip, if someone hadn't already done it successfully, spreading the idea to other bros with loud combo amps over the years, it's probably not a real good idea. i love my amp, it's just really loud. the sonic spread is incredible on stage, despite its acceptable band-practice volume. so i don't want to fry the Mercury OT or anything. Just wanted some ideas on this hypothesis.
if anyone wants to keep chiming in, more input is more than welcome.

You won't fry the output transformer or anything else by replacing one of the speakers with a power resistor, as long as it is the right nominal value and high enough wattage, it will be fine. As I mentioned above and as Walter did there is an effect on the tone, it is not totally transparent, but it's not toally bad or worthless either. Give it a try, it's certainly cheap enough and it won't hurt anything. If it doesn't work for you, you won't have lost much trying.

 

[hasserl]

does an amp's output transformer still see a blown speaker as a "load" with the same impedance as it had when it was healthy? (assuming that just the cone is bad, not the internals)

I.e., if you took an x-acto knife and cut the paper cone away, but left the coil/magnet intact, couldn't that serve as the "resistor"?

probably a dumb question... I realize.

It depends on what blows, if the voice coil opens it won't present any load at all to the OT.

You could do what you suggest about cutting away the cone of a speaker to make a reactive load, if you can figure out a way to keep the voice coil assy together. But Ted Weber already did that for you, it's call a MASS. They used to sell the motor's separately to those wanting to build their own attenuators, but due to product liability issues with people that aren't quite as smart as they think they are they quit doing that.

 

[pula58]

Why not just get a pair of inefficient speakers? That could cut down the volume quite a bit!

 

[TubeLuvr]

does an amp's output transformer still see a blown speaker as a "load" with the same impedance as it had when it was healthy? (assuming that just the cone is bad, not the internals)

I.e., if you took an x-acto knife and cut the paper cone away, but left the coil/magnet intact, couldn't that serve as the "resistor"?

probably a dumb question... I realize.

That is what the Weber 'Mass' attenuators are, they call it a Speaker Motor.
http://www.tedweber.com/atten.htm

 

[pgissi]

If you don't go with a Mass there is this and they are now available-

http://eminence.com/fdm.asp

 

[tommytomcat]

If it were mine.. I would unhook one of the speakers.. pull one of the 5U4G's, leaving just one in there.. Install 6V6's or 5881's and rebias. See if you can get the plate voltage down in the 430vDC's (or even a little less) with bias while still staying within the tube's operating parameters. I'd buy an attenuator before I installed a resistor as a replacement of one of the speakers.

 

[white.space]

Thanks for the vote of confidence, Hasserl and everyone else.

If it were mine.. I would unhook one of the speakers.. pull one of the 5U4G's, leaving just one in there.. Install 6V6's or 5881's and rebias. See if you can get the plate voltage down in the 430vDC's (or even a little less) with bias while still staying within the tube's operating parameters. I'd buy an attenuator before I installed a resistor as a replacement of one of the speakers.

I currently run a single rectifier and have 5881's in there! Never considered 6V6s...

Incidentally, I live in Denton, listen the The Ticket and you're in Lizard Larceny... awesome!