Using higher impedance speaker to reduce amp volume

[Dr. Lo]

Anyone have experience doing this with a Fender tube amp, like a Deluxe Reverb or a Princeton Reverb? I like cranking these kinds of amps but at that level the volume is sometimes way too loud. I'm thinking of using a 16 ohm speaker in my Princeton Reverb that's "expecting" an 8 ohm load. What will it do to my tone besides reduce the power output of the amp and thus its volume?

 

[Vasshu the humanoid typhoon]

Re: Using higher impedance speaker to reduce amp volume

On tubeamps, always match the impedance, otherwise the amp can be dammaged.
Better idea to get a powerbreak/soak for your amp.

 

[Rich_S]

Re: Using higher impedance speaker to reduce amp volume

+1. Mis-matching is bad. Mis-matching with the speaker higher than the amp is worse.

 

[Lewguitar]

Re: Using higher impedance speaker to reduce amp volume

I don't know...I've never injured a Fender tube amp by mismatching the impedance. But I've never mismatched it by more than using 4 ohms for a 8 ohm ideal load or 2 ohms for an ideal 4 ohms load.

My buddy has two 16 ohm Celestions in his Twin Reverb. That amp wants to see 4 ohms ideally but the speakers total 8 ohms and he's used it for at least 10 years like that with no problems.

In fact, anytime you plug a speaker into the external speaker jack of a Fender combo amp you're going to mismatch the impedance. Plug a 4 ohm speaker cab into the external speaker jack of a Twin Reverb or Pro Reverb (which wants to see the 4 ohm load of the two 12" speakers in the combo amp) and you're providing a 2 ohm load. I've done that many times with no bad results.

With Fender tubes amps, generally you can have a mismatch up or down and not hurt the amp.

Only amp I'd be especially careful of is the four 10" speaker models which want to see 2 ohms.

 

[PFDarkside]

Re: Using higher impedance speaker to reduce amp volume

Guys, I will admit upfront that I don't know much about Tube Output stages, but in the Mesa Boogie operation manual it gives a multitude of amp -> speaker connection options. The manual details how you can use a "safe mismatch" by using a speaker of higher impedance than the output impedance of the amplifier. Is Mesa Boogie doing something different than other manufacturers, or are tube amps really the same as solid state amps as far as output impedance is concerned? (With solid state amps, it is absolutely fine to connect a speaker of higher impedance than the output impedance of the amp, but a speaker of lower impedance will draw more current, and depending on the specs of the output circuitry may damage the amp)

Like I said, I have limited experience with different speakers, but I have heard that if you do use a higher impedance you don't affect the volume as much as the overall tone.

 

[Vasshu the humanoid typhoon]

Re: Using higher impedance speaker to reduce amp volume

Hmm explain my friend old Super Reverb that torched its output powersupply
Saw 16ohm and died after an hour of gigging.

 

[Karmadog777]

Re: Using higher impedance speaker to reduce amp volume

higher ohlm speaker than amp is safe and stated as so by different manufacturers, and will lower output (think resistors)
When you drop BELOW your amps ohlm load is when you fry your amp.
I have known more than one person who wired his cab parallel thinking that he would add up the ohlm load(wrong) thats series ,one resulted in a fried power amp.

 

[Lewguitar]

Re: Using higher impedance speaker to reduce amp volume

Hmm explain my friend old Super Reverb that torched its output powersupply
Saw 16ohm and died after an hour of gigging.

That's a huge mismatch and why I said:

Only amp I'd be especially careful of is the four 10" speaker models which want to see 2 ohms.

You could get away with a 4 ohm load when a Super wants to see 2 ohms...but 16 ohms is to big a mismatch. What would that be? Something like a 400% mistmatch? I forget how they figure that sort of thing.

 

[Rich_S]

Re: Using higher impedance speaker to reduce amp volume

Sorry, K-dog, but that is flat out wrong for tube amps. Solid state and tube amps are exactly opposite when it comes to impedance mismatch. It's better to match them, but if you have to mismatch with a tube amp, it's better to have the cab lower than the amp.

Most tube amps can withstand a 2:1 mismatch in either direction, although I'll be so bold as to say that Marshalls are less tolerant than Fenders or Mesas.

Back to original question, using a 16-ohm speaker on an 8-ohm amp is not an effective way to reduce the volume. It's hard on the amp, and the volume decrease will by minor.

The good news is that attenuators for small amps (for example the Weber Mini MASS) are cheap compared to those needed for 100-watters. I use a 25-watt Mini MASS on my 18 Watter clone and love it. I can't recall ever being able to crank that amp without it.

 

[Rich_S]

Re: Using higher impedance speaker to reduce amp volume

That's a huge mismatch and why I said:

You could get away with a 4 ohm load when a Super wants to see 2 ohms...but 16 ohms is to big a mismatch. What would that be? Something like a 400% mistmatch? I forget how they figure that sort of thing.

It's not only a huge mismatch, it's in the "wrong" direction for tube amps; higher than expected.

 

[PFDarkside]

Re: Using higher impedance speaker to reduce amp volume

It's not only a huge mismatch, it's in the "wrong" direction for tube amps; higher than expected.

I hear this, but then read in the Mesa manual about going the other way. Do you have some documentation? I'm very interested to get this settled once and for all. In Solid State, going higher is always safe, going lower may work but it's not correct and damage may occur depending on how robust everything is. Obviously matching is the best but I'd love to read the theory either way for tube amps.

 

[Vasshu the humanoid typhoon]

Re: Using higher impedance speaker to reduce amp volume

Dunno the theory, well I have heard it a few times...but I have so forgotten about it
Our resident tubeamp builder, old guy who has been doing this stuff since the 60's......he says: never mismatch impedance, ever.
Well I will get around the actual facts about this, hmm none of our resident builders around???
They should be able to answer this little thing
HAI!

 

[Lewguitar]

Re: Using higher impedance speaker to reduce amp volume

Dunno the theory, well I have heard it a few times...but I have so forgotten about it
Our resident tubeamp builder, old guy who has been doing this stuff since the 60's......he says: never mismatch impedance, ever.
Well I will get around the actual facts about this, hmm none of our resident builders around???
They should be able to answer this little thing
HAI!

Honest: with most quality tube amps (ie: Fender) you can mismatch one step up or one step down and get away just fine with it. That means 8 ohms or 2 ohms will work fine with an amp that wants to see 4 ohms ideally. But I would not use a 16 ohm load with an amp that wants to see 2 ohms...that's to big of a mismatch.

In the old days (1970 and before I knew better) I used to sit my brownface Fender Concert (a 2 ohm amp like a Super Reverb) on top of my 16 ohm Marshall bottem and plug the bottem into the external speaker output so I'd have four 10's and four 12's going. Never hurt it at all...and I used to play with that thing cranked. Just to play it safe, I would never do that these days...but the fact remains that I did do that back then and it did the amp no harm.

And like I said, my buddy Duane has been using two 16 ohm Celestions (8 ohms total) in his Twin Reverb amp for the last 10 years or more with no problems, despite the fact that that amp likes to see a 4 ohm load.

Lew

 

[Vasshu the humanoid typhoon]

Re: Using higher impedance speaker to reduce amp volume

Hehe yeah some of those can take it
I am just cautious with tubeamps these days, especially old ones, can't get them like that anymore.

 

[LJ King]

Re: Using higher impedance speaker to reduce amp volume

Tube and solid state amps are not alike in this regard.

Tube amps cannot take an open speaker load, but they can survive a direct short. Solid state amps can deal with an open speaker load all day but cannot survive a direct short.

If you have to mismatch with a tube amp, always mismatch downward - meaning a lower impedance speaker with a higher impedance amp.

Reducing impedance with a tube amp doesn't mean it will put out more power the way a solid state amp will. A tube amp will always put out less power when any deviation from the norminal output impedance is made - either up or down.

Matching is always best for a tube amp, and never going below the minimum for a solid state amp is best for it.

But if you have to mismatch a tube amp, always go for a lower speaker impedance. If you have to mismatch a solid state amp, always keep the speaker impedance above the minimum.

 

[doveman]

Re: Using higher impedance speaker to reduce amp volume

Guys, I will admit upfront that I don't know much about Tube Output stages, but in the Mesa Boogie operation manual it gives a multitude of amp -> speaker connection options. The manual details how you can use a "safe mismatch" by using a speaker of higher impedance than the output impedance of the amplifier. Is Mesa Boogie doing something different than other manufacturers, or are tube amps really the same as solid state amps as far as output impedance is concerned? (With solid state amps, it is absolutely fine to connect a speaker of higher impedance than the output impedance of the amp, but a speaker of lower impedance will draw more current, and depending on the specs of the output circuitry may damage the amp)

Like I said, I have limited experience with different speakers, but I have heard that if you do use a higher impedance you don't affect the volume as much as the overall tone.

He's right ... from page 7 of the manual. http://www.mesaboogie.com/manuals/Mark1 Reissue.pdf

NOTE: Power and tone differences can be achieved through matching or mismatching speaker impedances. This can not hurt your amplifier and is an interesting experiment that we encourage you to try. For example: with the 60 / 100 switch up ( 100 watt position ) and the speaker connected to the 8 Ohm speaker jack, the amplifier will sound and feel very bold and punchy. ( Perfect for loud clean playing, or cutting through a loud stage mix. ) Some players, however, find this sound and feel too stiff and revealing of mistakes. If you encounter this, no problem. Simply connect the speaker to the 4 Ohm speaker jack and you have reduced your overall power to about 75 watts, while softening the sound and feel substantially. By using the 60 watt position ( toggle switch down ) with the speaker connected to the 8 Ohm speaker jack, a different sound and feel can be achieved. Somewhat less “midrangey” and more hollow sounding, this set-up works whenever a clean sound is desired that has a little different personality. Keep in mind that this mismatch ( 60 watt position - 8 Ohm speaker jack ) is a mismatch in the lower than proper match direction. This causes the 6L6 power tubes to wear faster, and produces a much “harder” clip. Again, we encourage you to experiment and find the tonality that suits you best.

Also note that pages 16-21 show many safe mis-matches ... works on my '78 boogie ... occasionally run a 16 ohms speaker load from the 8 ohm output. Anyway ... I'd follow the specific manual.

 

[Karmadog777]

Re: Using higher impedance speaker to reduce amp volume

:wall:Is Mesa different than other tube amps?
Look at the Mesa manual link in Dovemans post pages 16-21
My amp in Tube pre only so that may explain MY misunderstanding , I would like to understand this too. But with facts from manufacturers not hersay,plus I dont want someone to smoke their transformer because of something I said:smack:


At any rate the original poster is asking about a 16ohlm load on a 8 ohlm output...that is a 2:1 mismatch and should be safe with any amp .....right?

then again as someone already said, a power soak or hotplate would give best results for playing cranked at lower volumes

 

[muttonchopsrule]

Re: Using higher impedance speaker to reduce amp volume

i've run a single rectifier through a 16 ohm cabinet when it was expecting to see 8 ohms, and it handled it just fine. however, i've seen other amps blow power tubes in a similar situation. the impedences on amplifiers and cabiinets are labeled for a reason, and it's best to match them for the sake of prolonging the life of your gear.

i'd suggest getting an attenuator, or a less powerful amp.

 

[the guy who invented fire]

Re: Using higher impedance speaker to reduce amp volume

You CAN mismatch the impedence of a tube amp ujp to 100% in EITHER direction and still be safe...I wouldn't do it for long periods with a cheeply built amp but well made amps can take it.

Now, I wouldn't run an amp set for 8 ohms at 2 ohms and I wouldn't run an amp set at 2 ohms at 16 or other such big mismatches...NO MORE THAN 100% mismatch.

However, all that said...the volume difference in volume you're going to get from running an 8 ohm deluxe reverb at 16 ohms is not worth talking about to be honest...if your Deluxe is too loud get an attenuator or get a smaller amp.

 

[mad dog]

Re: Using higher impedance speaker to reduce amp volume

An interesting thread. Which leads to a practical question. I have a tweed bandmaster type amp, 3x10 format, in this case, with the OT exactly matching the 2.6 ohm speaker load. Let's say I want to get a new baffle for a 15" speaker, make it into a tweed pro. Where would the best sound lie: Get a 2 ohm speaker, or a 4 ohm speaker? I'm guessing safety would not be a problem at this level of mismatch. But what about sound. What are the trade-offs?