I have a set of them in Webb cabs and I'm getting ready to pick up a Stewert power amp from Wally's Sales & Service and put a stereo rig together.

This resource indicates that K130's were available in 8 or 16 ohm versions... 125W RMS.

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Thanks for your reply, but I know they were produced as 4 ohm speakers. Both of mine say 4 ohm on their factory original name plates.

One of them I purchased "blown". I had to get it reconed with a generic kit because JBL stopped making the 4 ohm recone kit.

125 watt rating scares me. If so, I'm in trouble. But I think they are rated to handle more than that.

Anybody know?

I have some K130s and have never had a problem using them with my Peavey DPC 1400 0r Stewart 1.2.

Bob

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Bob

[This message was edited by Bob Knight on 29 May 2001 at 09:02 PM.]

I'm getting the Pro Reference 1000. I maybe should have gotten the 500 model, but my dealer advised me to get the 1000 and has already ordered it and has it in stock and indicated that he doesen't want me to leave him stuck with it.

The 1000 puts out 400+ watts per side into 4 ohms.

Reference amps in studios are traditionally run wide open. You usually set your mixer, preamps, etc. to the appropriate volume. In my studio, I run my Hafler Reference amp that way.

I guess I'll just have to run this amp at 1/4 or 1/2 volume.

How much wattage do you think my 4 ohm K-130's (15") can handle?

In my past experience with PA, I've found that the signal content has some impact on power handling capability. I've seen high power rated speakers and drivers blown with a relatively a low power clipped signal, yet handle a clean signal with power in excess of the rating without problems. Horn drivers seem to be particularly susceptible.

I believe it has something to do with the cone (or diaphragm) trying to track those ugly non-linearities and square wave components that are generated by clipping a power amp. That type of signal tends to cause the cone to start and stop rapidly at the ends of the excursion, rather than move smoothly in and out. This is not the same type of "musical" distortion that an instrument amp generates, it's ugly.

Just MHO...

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UNLESS you are driving your power stages to continuous maximum power, I believe you will be ok.

Some trivial facts:

1. Because a power amp is rated at 400 Watts does NOT mean it will put out that much. Most listening levels are FAR lower than that.

2. Unless that 400 watts is true RMS power. the actual power could be considerably less.

Let me explain.

Prior to the "truth in advertising" laws clamping down on amplifier manufacturers, it was a joke when reading what a given amplifier would do.

This is becuase of the way in which an amplifier is rated. There are several ratings that can be rationlized:

1. True RMS

2. RMS

3. Music Power

4. Peak Power

5. Peak to Peak Music power

Of these ONLY one (true RMS) is considered by most engineers to be realistic.

And it always ends up with a rated power of less than the others. In some cases incredibly less.

Example:

A 60's Fender amp rated using "true RMS" power of 55 Watts can be:

1. 75 watts RMS

2. 110 watts music power

3. 150 watts Peak power

4. 300 watts Peak to Peak music power

But in all the above cases the thing that blows a speaker is the true RMS power. With this one caveat:

For a very brief micro second a signal of extremely sharp peaks could, I repeat could, damage ANY speaker, EVEN at much less than its rated power.

There are basically two things that blows a speaker:

1. The high current flowing through the voice coil melts the insulation causing it to either rub against the magnet walls. Or shorting out of some of the windings, lessening its efficiency.

2. The signal is so large it causes the cone to move too far and tears (or permanently distorts) the cone.

So I would go along with b0b on this one. You are probably going to be quite safe. As long as you remember that ANY speaker can be damaged by a plectrum type instrument such as picking a bass string real hard.

God bless you in your quest,

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So I would go along with b0b on this one. You are probably going to be quite safe.

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I NEVER meant what you thought I said.

I meant I agreed with your post.

Then,,.,,,,,,, I should have made a new paragraph with my suggestion.

Sorry bout that!

Yes my Webb cabs are open back. My 1st K-130 is original to my Webb 6-14-E. I had bought the amp used and sent it to Mr. Webb to service (it had a minor distortion at low volume). He went over it and it works great now.

I asked him to make it into a piggy back amp and make me an extra cab. I kept my eye open for another K-130 and found one.

Yes, wattage ratings are very confusing.

For example with regular six string guitar amps, the Vox AC-15 kicks ass. It's rated as 15 watts, but those must be English watts, 'cause it will keep up with any 40 watt Fender no sweat. And the AC-30 (supposedly 30 watts) is too loud for your average club gig, unless you're in a metal band.

It's true that a lower volume but distorted signal will blow a speaker where a louder, clean signal will not.

So how do I approach setting the volume level regarding power amp vrs preamp?

In my studio, I run my Hafler Reference amp wide open and adjust my levels via my Mackie mixer.

Should I run the Stewart Pro Reference 1000 wide open and back way down on my Mesa Stereo Tube Preamp?

Or should I run the Stewart at about 1/2 volume and bring the Mesa volume up?

BTW, I'm gonna have to run the stereo outs of the Boogie into the stereo ins of the Lexicon MPX-1 and go from it's stereo outs to the stereo ins of the Stewart. Maybe I can run the Boogie as hot as possible without over driving the Lexicon and bring the signal level down coming out of the Lexicon.

In any event, I wanna hear the "tube tone" as much as possible.

At the price I'm gonna end up having in all this stuff, I could have bought one of those Fender Custom Shop "Dual Professional" amps and put JBL's in it.

This is reminding me of my recording studio..... "I bought it one piece at a time" like Johnny's Cad. Now I have different software and hardware conflicts. But if I had had all of the money at once, I could have bought a top of the line Pro Tools system.

I welcome further advise from you guys, and I appreciate your help very much. Gear is getting pretty damn complicated these days. I'm still not sure how to handle this situation.

I'm not sure that I know what you mean by "drive". What specifically are you refering to?

That's a word used a lot of different ways by different folks these days.

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I've seen high power rated speakers and drivers blown with a relatively a low power clipped signal, yet handle a clean signal with power in excess of the rating without problems.

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Great point Terry, it is the heat generated by clipping that almost always blows the speakers, very rarely does an amp cause the speaker to jump out of its gap from plain old too much power - it usually hurts our ears with high SPL before we get to that point.

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...the Vox AC-15 kicks ass. It's rated as 15 watts, but those must be English watts, 'cause it will keep up with any 40 watt Fender no sweat. And the AC-30 (supposedly 30 watts) is too loud for your average club gig, unless you're in a metal band.

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Those "English watts" are the same old volts time current that the rest of the world uses, the difference being that as those old tube amps (actually anything with lots of overdrive) push the waveform into clipping the fundamental signal becomes proportionally more of the total waveform, essentially a form of extreme compression you might say, thus the perceived high volume - it IS "loud!" The issue for most of us playing pSG is we don't want distortion, thus the need for the high HEADROOM provided by these powerful amps - they sound much cleaner at volume but maybe not as loud.

I have heard guitar players with little Fender DeLuxe amps on big outdoor stages punch over the top of the PA and actually be TOO loud for those folks exactly on axis - that is directly in front of the amp - while the guitar player standing beside and above it couldn't seem to hear sqwat.

Hope this is helpful. Also bear in mind that if someone provides you with a generic cone/voice coil for your JBL basket it probably isn't made to the same specs and will most likely not stand up as well.

dg

[This message was edited by Dave Grafe on 18 November 2004 at 11:52 AM.]

From Larry Clark's 2001 post (above) quoting the JBL Enclosure Information Manual:

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If a K Series loudspeaker is installed in an open-back enclosure,the maximum power applied to the speaker should not exceed 50% of it's RMS rating. For example,a K130 which is rated at 125 Watts RMS,should not have more than approximately 60 Watts RMS applied to it when mounted in an open-back box.

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Thus the reason that most people that had a Session 400 from '77 and earlier have blown their speaker. The JBL's just can't handle the wattage the Session puts out....the 125W rating was obviously with JBL's assumption that the speaker would be used in a bass amp with a closed back. 60W is what Ted told me....and that's also what Larry came up with as well.

No way around this, folks....JBL's are NOT meant for today's amps and applications where you occassionally lots of power on stage.

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the 125W rating was obviously with JBL's assumption that the speaker would be used in a bass amp with a closed back

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Joe, far from being obvious, JBL has NEVER endorsed using a D, K or E 130 with a bass in any kind of cabinet, that's why they make the -140 and -145 15" speakers for such applications.

What we do know for a fact is that PSG signal is big, covers an extremely wide frequency range and includes lots of sustained program, thus tending more towards the "continuous sine wave" than the so-called "continuous program" conditions that they test and design them for.

I have not used a 4 ohm speaker (other than the stock BW in the NV400 when supplied by backline rental companies) but I have hammered the living hell out of 8 and 16 ohm JBL D130F, K130, K140, K151, 2220, 2205, 2225, 2240 and 2245 speakers for longer than some of our newer forum members have been walking and they have always taken MORE, not less, than JBL says they are rated for. I have never blown a JBL that was used as intended by the manufacturer.

I don't know where this 60 watt figure comes from (it's nowhere in my library of JBL tech material and I have the K series manual right here in front of me) but the 8-ohm D130F in my own open-back cabinet is going on twenty years now at >200 watts and still does the job just fine, with more output per watt than anything out there but the TAD speakers that I just plain can't afford. I'm not saying that it's the answer for anybody else but I'm stickin' with it.

Good luck in your search for the solution to your problem.

Dave

[This message was edited by Dave Grafe on 18 November 2004 at 03:50 PM.]