2x15 Help?

[tabasco]

Riddle me this Batman,
On this web site in the heading called Catalogs, under the listing index of/site/brochures, under 100s 200s gif it states: 250 watts/ 2 D140F JBL's
Is the  Ampeg  SVT at 300 watts really that much superior to the Sunn 200s at 250 Watts?
What happens when you turn up the 200s through the 2 D140F's that came with the package?
I got it! Maybe he should sell those crummy Jbl speakers real cheap to me
I am having fun with this, Hope you are also

[tabasco]

SORRY Brochures not catalogs

[EdBass]

Sorry, can't let this go. 

Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) do not.

Not true - both tube and solid state amps vary their output power based on the impedance of the load - the instantaneous value of the load impedance, NOT the "nominal" impedance rating.

Despite what some may believe, even tube amps do not violate Ohm's law.

Alright smartypants, I'll ammend this statement to read "Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) output are not effected by nominal impedance.
But, of course that is also a generalization, as I alluded to with this statement; "Tube amps output (pretty much) the same watts at any impedance"

However, even solid state amps don't have "ohms", i.e.;

What ohm is your Ampeg head?

Again, ohms are a measure of resistance/impedance and do not correlate to an amplifiers output other than the effect the load (which is rated in “ohms”) has on the output potential. A solid state amp can be rated for X watts at a specific load, a load measured in ohms, but an amp is not rated as being any specific “ohms”.

This is the start of a circular argument.

Believe it or not, this was actually intended to avert a circular argument. I'm sure you're familiar with the KISS theory? (Keep It Simple, Stupid) For the purposes of this disertation, I kind of chose to ignore output stage impedance to emphasize (i.e. over emphasize) the error of using "ohms" as a general rating for an amplifier in the context of the original question.

Tube amps output (pretty much) the same watts at any impedance, but you need to match the load impedance with the output stage impedance using a transformer. That’s why most tube amps have switchable transformer taps, as in the selector on an SVT for either a 2 or 4 ohm speaker load.

And this directly contradicts the circular argument you started above.

Ohms is simply a quantity of measurement, just the same as "Watts" is a quantity of measurement.

Question: If a tube amplifier doesn't have an "Ohms" output then what exactly is being matched by those switchable transformer taps? Answer: The output impedance of the amplifier to the load impedance.

Both impedance values are measured in Ohms. So, if an amplifier has an output impedance there would have to have some specific "Ohms" measurement to that impedance. Doesn't matter if you call it a rating or not, there is still an ohms measurement for the output impedance of the amp.

Again, I plead KISS. Of course you are technically correct, but in the generalized ambience of the original thread it seemed to me to be a reasonable analogy.

Obviously... I am totally confused what point you are trying to make. Chalk it up to old age.  But if you used new D140F's... you ain't no spring chicken either!! 

Yeah, you old folks do get confused easily!  As far as the "spring chicken" remark; Firstly, you show your age by even using the term "spring chicken", and second, I admit that I do in fact qualify for AARP benefits.

[EdBass]

Riddle me this Batman,
On this web site in the heading called Catalogs, under the listing index of/site/brochures, under 100s 200s gif it states: 250 watts/ 2 D140F JBL's
Is the  Ampeg  SVT at 300 watts really that much superior to the Sunn 200s at 250 Watts?
What happens when you turn up the 200s through the 2 D140F's that came with the package?
I got it! Maybe he should sell those crummy Jbl speakers real cheap to me
I am having fun with this, Hope you are also

Are you the Frank Gorshin Riddler or the Jim Carrey Riddler? And how do you know some of my friends call me Batman?
As far as the 200S, 100S, or for that manner any 2 X KT88/6550 amp, 250 watts ain't gonna happen. The amps you refer to are rated at 60 watts.
I personally like AlNiCo magnet drivers (such as the D series JBL's) for tube amps, but they are very limited by modern standards.
I'll wait for Joe's explanation of "peak" watts so he doesn't get his panties in a wad by one of my versions.

[tabasco]

Edbass, Just lucky on the Batman thing. I found another article that says the 200s is 100 watts. Ok I believe ya on the power thing. 60,100,250, must be the ohm thing! Ha Just kidding don't go there. I have had the concert rig for years and it is my sons favorite amp for his Punk band. I also have Acoustic, Randall, and Peavey gear I will be taking to the grave. That 600 Watt amp, That's what the guy that made it said, burned up on stage. It lit up the room with a really nice shade of blue before it smoked the board. I think it was a ohm thing, Ha Don't go there. I am sure I will get the technical   
answer on why the brochure says 250. Maybe it's the ohms. Ha, Just kidding.
Thanks to all.

[JoeArthur]

Alright smartypants, I'll ammend this statement to read "Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) output are not effected by nominal impedance.
But, of course that is also a generalization, as I alluded to with this statement; "Tube amps output (pretty much) the same watts at any impedance"

You are claiming that tube amps are not affected by the load impedance (nominal or otherwise) and at the same time claiming impedance matching is necessary for tube amps. Do you not see this as a contradiction? 

I'm thinking that what you might be trying to say is something like: if the tube amp and load are matched at 4 ohms the same power will be transferred to the load as when the same tube amp is matched to a 16 ohm load.

Example: Assume I have a tube amp with a fixed output impedance of 4 ohms. With a 4 ohm load impedance,  the tube amp will produce the most power.  The power output of the tube amp will be reduced at load impedances of 8 ohms, or even more at 16 ohms (since it cannot be matched to those impedances).

My point: The key to producing the maximum amount of power is the matching of the source (amplifier) and destination (load/speaker) impedances.

And this is equally true for both solid state and tube amplifiers.

A solid state power amp has a much lower output impedance compared to the load impedance than a tube amp. When the load impedance is reduced for a solid state amp, more power may be produced. The real cause of this power increase is an improved matching between the amplifier output and load impedance.

Take the tube amp with the fixed (4ohm) output impedance mentioned before. If we start with a 16 ohm load and measure the output power... the reduce the load to an 8 ohm impedance and measure the output power... we will observe that the tube amp produces more power. Repeating with a 4 ohm load, the tube amp will now produce even more power.

Exactly the same observed behavior as the solid state amp. 

Only no mysticism necessary for an explanation. 

Yeah, you old folks do get confused easily!  As far as the "spring chicken" remark; Firstly, you show your age by even using the term "spring chicken", and second, I admit that I do in fact qualify for AARP benefits.

Yep, "Smartypants" is a much older term than "spring chicken". 

[Soundmasterg]

Well obviously Greg <sigh> - an ex-spurt like "Ted Weber" is going to have much better knowledge of JBL D140F power ratings than anyone fresh off the street... like say, a "Harvey Gerst". 

Joe, I know Harvey Gerst designed the D series JBL's, and I've read quite a few of his postings on the web. Obviously he is going to be the best expert out there for this particular speaker. What I was getting at with what Ted Weber rates them at is that he rates his speakers quite conservatively, and especially for bass frequencies since they are harder for a speaker to deal with, it is a good idea to treat your speakers conservatively if you want them to hold up under high power demands. The fact that so many JBL D series speakers seem to need recones over the years would lead me to believe that perhaps they may have had a bit too high of a power rating attached to them. Moreoever, you have to wonder what JBL was using to rate their speakers at that power output. What was their test setup? I've seen some posts in the past where Harvey talked about the D series JBL's and said that with bass frequencies, the power the speakers could take wasn't quite as high as the ratings. Don't ask me to post it though because it has been quite awhile since I read it and don't know where it was since I didn't book mark it. You seem to have a "thing" against Ted Weber btw though I could be wrong.....

Oh... an SVT has 300 "tube" watts? Dang, I forgot about that - I though they were ordinary watts. 

 

Ok, now you're just nitpicking. I could have easily said transistor SVT, though perhaps I should have just said a 300W SVT. A 300W amp will not get along very well with a pair of D140's unless played quietly. How about that? Does that fit your perception of perfectly correct grammar Joe?

Sorry... I can't resist - I REALLY NEED A LINK for your "BEFORE the onset of distortion" qualification for the measurement of the power output of an SVT ("tube" or otherwise... wattage measurement).

   

When you are measuring the output power of an amplifier, you input a sine wave and hook a scope up to the output. You turn up the amp until the wave just starts to clip, and then you back the volume off a tad and figure your output power from the voltage and impedance on the output. If you are smart you use a fixed resistor instead of a speaker so it makes the equation much easier. This would be the RMS power measurement, and the 300W RMS is what the SVT is often quoted at, though the 6146B amps put out more than 300W, and the MTI era SVT's put out less than 300W. If you turn the amp up all the way and measure the power level at the output, this is the peak output power. If this isn't how they should be measured, then why don't you elaborate on what you're talking about Joe. You seem so eager to point out everyone's failings except for your own.

Greg

[JoeArthur]

Well obviously Greg <sigh> - an ex-spurt like "Ted Weber" is going to have much better knowledge of JBL D140F power ratings than anyone fresh off the street... like say, a "Harvey Gerst". 

Joe, I know Harvey Gerst designed the D series JBL's, and I've read quite a few of his postings on the web. Obviously he is going to be the best expert out there for this particular speaker. What I was getting at with what Ted Weber rates them at is that he rates his speakers quite conservatively, and especially for bass frequencies since they are harder for a speaker to deal with, it is a good idea to treat your speakers conservatively if you want them to hold up under high power demands. The fact that so many JBL D series speakers seem to need recones over the years would lead me to believe that perhaps they may have had a bit too high of a power rating attached to them. Moreoever, you have to wonder what JBL was using to rate their speakers at that power output. What was their test setup? I've seen some posts in the past where Harvey talked about the D series JBL's and said that with bass frequencies, the power the speakers could take wasn't quite as high as the ratings. Don't ask me to post it though because it has been quite awhile since I read it and don't know where it was since I didn't book mark it. You seem to have a "thing" against Ted Weber btw though I could be wrong.....

Oh... an SVT has 300 "tube" watts? Dang, I forgot about that - I though they were ordinary watts. 

 

Ok, now you're just nitpicking. I could have easily said transistor SVT, though perhaps I should have just said a 300W SVT. A 300W amp will not get along very well with a pair of D140's unless played quietly. How about that? Does that fit your perception of perfectly correct grammar Joe?

Sorry... I can't resist - I REALLY NEED A LINK for your "BEFORE the onset of distortion" qualification for the measurement of the power output of an SVT ("tube" or otherwise... wattage measurement).

   

When you are measuring the output power of an amplifier, you input a sine wave and hook a scope up to the output. You turn up the amp until the wave just starts to clip, and then you back the volume off a tad and figure your output power from the voltage and impedance on the output. If you are smart you use a fixed resistor instead of a speaker so it makes the equation much easier. This would be the RMS power measurement, and the 300W RMS is what the SVT is often quoted at, though the 6146B amps put out more than 300W, and the MTI era SVT's put out less than 300W. If you turn the amp up all the way and measure the power level at the output, this is the peak output power. If this isn't how they should be measured, then why don't you elaborate on what you're talking about Joe. You seem so eager to point out everyone's failings except for your own.

Greg

Just curious... Thanks!!

[EdBass]

Alright smartypants, I'll ammend this statement to read "Transistor amps vary output by impedance, tube amps (such as the SVT being discussed in this thread) output are not effected by nominal impedance.
But, of course that is also a generalization, as I alluded to with this statement; "Tube amps output (pretty much) the same watts at any impedance"

You are claiming that tube amps are not affected by the load impedance (nominal or otherwise) and at the same time claiming impedance matching is necessary for tube amps. Do you not see this as a contradiction? 

I'm thinking that what you might be trying to say is something like: if the tube amp and load are matched at 4 ohms the same power will be transferred to the load as when the same tube amp is matched to a 16 ohm load.

Correct! But...in the interest of simplicity, I'm assuming a matched load. I've personally always thought it important with a tube amp to try to match the output impedance, at least pretty close.

Example: Assume I have a tube amp with a fixed output impedance of 4 ohms. With a 4 ohm load impedance,  the tube amp will produce the most power.  The power output of the tube amp will be reduced at load impedances of 8 ohms, or even more at 16 ohms (since it cannot be matched to those impedances).

My point: The key to producing the maximum amount of power is the matching of the source (amplifier) and destination (load/speaker) impedances.

And this is equally true for both solid state and tube amplifiers.

So then it's OK to use any load on any tap with a tube amp? Is it just a matter of how many watts you need, or using whatever impedance cabinet you might have available and wail away? Careful, some non "trained professional" reader might "try this at home".

A solid state power amp has a much lower output impedance compared to the load impedance than a tube amp. When the load impedance is reduced for a solid state amp, more power may be produced. The real cause of this power increase is an improved matching between the amplifier output and load impedance.

Take the tube amp with the fixed (4ohm) output impedance mentioned before. If we start with a 16 ohm load and measure the output power... the reduce the load to an 8 ohm impedance and measure the output power... we will observe that the tube amp produces more power. Repeating with a 4 ohm load, the tube amp will now produce even more power.

Exactly the same observed behavior as the solid state amp. 

Except... I can't imagine you intentionally running a blackface Fender (fixed 4 ohm output right?) with a 16 ohm load, whereas the only thing the big load would do to a SS amp is reduce the output.

Only no mysticism necessary for an explanation. 

What about magic smoke then? How do explain that without mysticism?

Yeah, you old folks do get confused easily!  As far as the "spring chicken" remark; Firstly, you show your age by even using the term "spring chicken", and second, I admit that I do in fact qualify for AARP benefits.

Yep, "Smartypants" is a much older term than "spring chicken". 

Well, I'll have to defer to your call on which term is older, I wasn't around yet when those terms were commonly used!

Alright, It's been a slice of heaven, but I'm tired of this one. Mea culpa for "newbie-izing" a response, no more simplifying while you're on watch o technoguru!

[basiklybass]

[The fact that so many JBL D series speakers seem to need recones over the years would lead me to believe that perhaps they may have had a bit too high of a power rating attached to them/quote]


Referring to why so many JBL's have had to be reconed over the years...I would suggest that the reason is because they are such great speakers and work so well that it is worth it to keep them running. I don't see many EV's, Altecs, Jensens, CTS's..that are all scratched up, that obviously have been heavily used, some but not a lot.... I see those all the time in JBL's. While agreeing that possibly the power ratings may have been a bit overstated....it proves the durability of the speakers that they are worth reconing. All the other stuff was just tossed away.


BTW...I sleep with my JBL's too! .

[JoeArthur]

[The fact that so many JBL D series speakers seem to need recones over the years would lead me to believe that perhaps they may have had a bit too high of a power rating attached to them

Referring to why so many JBL's have had to be reconed over the years...I would suggest that the reason is because they are such great speakers and work so well that it is worth it to keep them running. I don't see many EV's, Altecs, Jensens, CTS's..that are all scratched up, that obviously have been heavily used, some but not a lot.... I see those all the time in JBL's. While agreeing that possibly the power ratings may have been a bit overstated....it proves the durability of the speakers that they are worth reconing. All the other stuff was just tossed away.


BTW...I sleep with my JBL's too! .

Sorry, I had to correct your cut and paste... 

Of course I agree with you - the reason is definitely because of their original quality. It would be a no-brainer, given a choice of all of those speaker types as to which one to invest in a recone - JBL first and foremost.

It is absolutely moronic to believe that a "high power rating" destroys speakers. Seriously... Does anyone actually think that simply believing your current speakers will handle... uh... twice... or 10, 100 or even 1000 times whatever power you think they will handle... will automagically make them blow?

Not me. I've always had to actually turn on the amp, turn it waaaay up high... and really work at it before I ever blew a speaker. And each and every one of those speakers I blew - they always "complained" to me long before it blew.

I chose to ignore it.   

And for that reason, it can't be the fault of the speaker, or the manufacturer. 

[Soundmasterg]

Oh I agree completely that when the speakers blow, its the fault of the operator!  You can hear it when you're stressing your speakers before they actually destroy themselves to the point of not operating anymore.

[basiklybass]

Thanks for the correction Joe...still trying to figure out all the aspects of how this forum operates.

Agreement on operator error and being warned...nearly. I still can't figure out what cause my Altec 421's to burn up with my SVT head way back when. Issac or SMG or someone had some very good points before about it. Only thing I can figure is it was the pre-amp tubes introducing high frequencies which while playing loudly through them...just melted the coils. Replaced the tubes and never had another problem. I do not recall hearing anything leading up to it. Mind you it was 2  Ampeg 2X15 bottoms with the 421's in them. And mind you , we were playing kind of loud. But I have heard my speakers start to scratch and rub before the fail. Both times they blew it was just .........yep, like that...nothing. And all 4 went at the same time. I didn't do anything else but change the pre-amp tube...on the advice of a tech in Chicago..where I had to drive from Lake Geneva to get new speakers.

Gremlins maybe. It was in '74 or '75...right about the time AMC was making those rude little cars.

Funny thing is, now I play with some guys in a basement, through a Bose stick system and I use my Line-6 bass pod...and guess what...they love it when I crank the fuzz on...just like how a speaker sounds just before it blows. Aaaannnddd I do remember cutting radial lines in an old 15" speaker and painting it with varnish....back in '66...to get a fuzz sound...ahhhh..the good old days.

Ahhh what the heck...let 'er rip. You can always fix the JBL's.

[djc]

Ha, Ha!  "automagically"  that's a great word.  might of been intentional too!

I personally have never blown a speaker matching loads and playing my amps on 10.
ok.  maybe that's not entirely true