General question about speakers and their VOLUME

Joe Alterio · From: Irvington, Indiana

I recently strained my JBL K-130 to the point of needing a new speaker for my Session 400. I purchased a Peavey BW 1501 15" 4-ohm speaker and the first thing I noticed was how much LOUDER it was, even with nothing plugged in (in other words, all volume & treble settings turned down/off, leaving just the normal amp "hiss"). I thought this was odd, so I had my friend bring over his amp (same as my amp, but his has the BW, not a JBL) to see how his speaker would respond......and his BW responded the same as my new one.

When I plugged in my guitar, I expected the JBL to come out with less power than the BW's at the same volume levels.....and I was right.

Is there something about the JBL's design (magnet?) that allows it to draw from the amp at a lower level of volume? It seems odd that the speaker would do anything but reproduce the sound being delivered to it....yet the JBL most definitely reproduces sound at a lower volume.

Certainly not a complaint on my part (less amp hiss is GOOD!)......but I am curious as to what is occuring and why.

Joe

Jon Light (deceased) · From: Saugerties, NY

I don't know the definitions or the where's & why's but, quite simply, you are describing speaker efficiency.

Bob Knight · From: Bowling Green KY

Impedance differential? Was the JBL 8 Ohms by any chance?

[This message was edited by Bob Knight on 04 December 2004 at 01:07 PM.]

Joe Alterio · From: Irvington, Indiana

Both speakers are 4 ohms....I believe Jon may be on to something about efficiency.

I posed the above question to Ted Weber of Weber speakers, as he did a fantastic job of reconing my K130 to factory spec, voice coil and all. Here is what he had to say:

quote:

I can't remember if we have reconed those Peavey's, but I believe we have. I am certain, though, that they have more energy in the gap than the K130 and that would account for the extra sensitivity. Also, JBL's have always had a rather tight spider. If the Peavey has a loose spider, it would be easier to move and therefore would be more sensitive. However, it would 'hit the wall' at a lower volume than the JBL and would sound hard and clipped, while the JBL would compress smoothly.

A bit of this is a bit too technical for me to understand (spider? energy in the gap?) so I was a bit too embarrased to send him an e-mail for further explanation. But his last sentence stuck out, to me, since I always noticed that my old Nashville 400 and 1000 amps would "sound hard and clipped" when I would really drive them loud, while my current JBL in the Session 400 does not do this.....the tradeoff, of course, is that the JBL is really not all that powerful and tends to blow easily.

If anyone can help me to better understand Mr. Weber's explanation, it would be appreciated!

Joe

Jim Peters · From: St. Louis, Missouri, USA, R.I.P.

Joe, speakers are rated in efficiency by decibels per meter. A one watt tone is put into a speaker, the volume is measured one meter away. The resulting number would be the efficiency rating. The PV speakers might be putting out 101 dec,at1 meter away, with 1 watt of power, while the JBL might be 96 dec. It is common to use a more efficient speaker to make your amp louder, Deluxe Reverbs are prime examples. Maybe Brad Sarno could chime in with more expertise. JP

Dave Grafe · From: Hudson River Valley NY

I'll try to help out here, Joe,

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Different speakers have different efficiencies, and the efficiency is determined by the design and materials used in the speaker. JBL's were, at one time, considered very efficient, but others now are far better. (Manufacturers will often forego a little efficiency for a better sound, I suppose that's JBL's approach.) If you look at speaker specs, there will sometimes be a factor of "sensitivity" given. That's the speaker's efficiency, and it generally ranges from about 90db to a little over 100db. Though that only seems like a small amount of difference, it's actually quite significant. Using the same amp settings, a speaker with a sensitivity of 97db will sound about twice as loud as a speaker with a sensitivity of 93db! Now, If you have plenty of power available from the amp, efficiency isn't a big concern. But with small-wattage amps, it becomes very important.

As a general rule, big heavy magnets give better speaker efficiency. However, it's the magnet strength (flux density) that actually determines how powerful the magnet is. New smaller, lighter magnets (like the new neodymium ones) have fantastic flux densities, so size and weight will not be as big a factor in the future.

As with a strong magnet, a small voice-coil gap also enhances efficiency. The narrower the gap, the more flux density the coil "sees", but there is a limit, since the voice coil must have room to move, and to "warp" a little as the power is transformed into heat.

A thin cone and suspension ring, along with a flexible spider, will also help efficiency, as will a properly designed cabinet, but remember...everything is a trade-off. Most of the time, what you're looking for first is durability! The best sounding speaker ain't worth a hoot if you have to repair/replace it too often!

Joe Alterio · From: Irvington, Indiana

Thanks, guys.....I think I understand it now

This is great info!!!!

David Doggett · Posted 6 Dec 2004 6:50 am

Flux density was mentioned above, but I don't believe anyone mentioned the obvious - that bigger heavier magnets create greater flux density, and so are more efficient and louder. Simply caomparing the weight of the two speakers tells a lot. Different frame structures also contribute to weight, so the most accurate assessment is to look up the specs on the magnet weight.

Brad Sarno · From: St. Louis, MO USA

I always thought that the JBL K130 was more sensitive than the BW. The D130 is up around 102 or 103dB (1W/1M) sensitivity. I think the K130 is also up around there. I was under the impression that the BW is around 98 or 99dB. I can't find the specs anywhere though. My first thought was that his K130 may have been reconed at one point with an 8 ohm cone while the magnet still read 4 ohms. Usually when you notice a dramatic difference like that it's due to the impedance mismatch which can account for a very wide power difference. With the sensitivity issue, we're looking at maybe a spread of about 3-4dB, noticable, but not huge.

Brad Sarno

Dave Grafe · From: Hudson River Valley NY

Bravo Donny!
Brad, I'm with you in your belief of this paradigm. I have never had the cold hard facts all in my hands at the same time yet.

[This message was edited by Dave Grafe on 06 December 2004 at 02:20 PM.]

Dan Dowd · From: Paducah, KY, R.I.P.

The info on the JBL K 130 15 inch speaker is Power Capacity cont. 250 watts, 125W cont Sine Wave Sweep at 500-2500 hz within 1 db measured at 3.3 ft from speaker, freq range 50-6000hz, magnet 12 lbs, net weight 15 1/2 lbs, flux density 12,000 gauss, sentivity 103 db SPL. I used to have the specs on the BW but can't find them. Maybe on the Peavy Web Site.

[This message was edited by Dan Dowd on 06 December 2004 at 07:25 PM.]

Joe Alterio · From: Irvington, Indiana

I know that JBL claimed the K130 speaker could handle over 100W.....but there is just no way that is true.

I know when Ted Weber reconed mine, he laughed when I told him I was putting it into the 200+ Watt Session 400! He said I'd be lucky if it handled more than 60-70 watts. Mike Brown's comments about all the blown JBL's in the early Session 400s back that fact up......as have many other Forumites in past threads who have blown their JBL.

So....how about this question, speaker experts: How could JBL claim a much higher power handling capacity than was really true in practice? Faulty/outdated measurement techniques?

This also makes me question JBL's sensitivity measurement of 103db since that would go against what everyone said above about why the JBL would be QUIETER than the Peavey. Hmmmmmm.........

Joe

Jon Light (deceased) · From: Saugerties, NY

The following is copied from an old Amp Workshop BB thread. I've posted it here on the forum before. It is a collection of postings by Harvey Gerst, designer of the JBL speakers. It is not necessarily germane to this discussion but it sure covers some ground.
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9/20/97 alt.guitar.amps

…let me take you back to the late 50s, early 60s. JBL was a small company with their main offices above a candy store, and the manufacturing scattered in a number of buildings up and down the street, near Glendale, on Fletcher Drive.

They made the following speakers;
the D130 a full range 15",
the D131 a full range 12",
the 130A a 15" woofer,
the 130B (same as the 130A, but 16 ohms),
and the 150 - a 15" woofer with a heavier cone.

The D stood for a metal dome and the A and B were for woofers of different impedances. I don't remember if we made a 131A. We also made a D123 (full range pancake 12" speaker) and the D208 and D216 (both 8" speakers but with 8 and 16 ohm voice coils).

Fender was buying D130s for use in their Dual Showman systems, but they were experiencing problems in surrounds drying out from outdoor use, and burnouts from improper mounting techniques. I wrote a memo to the president of JBL, outlining a plan to let me design a series of speakers made specifically for musical use and he agreed. My plan called for modifications to the D130 and D131, plus an all new bass 15" speaker, and a new 10" speaker.

Since Fender was our largest purchaser, I did not want the headache of trying to re-introduce a whole new series so I kept the D130 name for the 15" and simply added an F (yes, the "F" is for Fender - don't know why to this day I did that, but I did). Since I was making up new model numbers, I decided where possible to keep it simple, so the 12" (originally the D131) became the D120F, and the new 10" became the D110F.

That left the new bass speaker. I didn't want to leave it in the 13x range because it was different and the 150 was already being used by our theater woofer. The 140 was not being used, so I named the new bass speaker the D140F.

After I left JBL, I understand they came out with the black crinkle finish and renamed them E series. The first major modifications were made in the K series, as I understand it.”

Harvey Gerst

9/19/97 alt.guitar.amps

the F is more rugged for portable use as a musical instrument speaker as compared to home use only on a fixed environment.

The "F" originally stood for Fender, since they were the largest purchasers, and at one time, the distributor for all the JBL guitar speakers. But the D130F speaker was not designed specifically by, or for them and the F eventually came to be just an indicator for all of the JBL musical instrument series speakers. The D130F did not have any significant frequency range differences, compared to the home version - the D130.
I feel I must tell you there is slightly more relief on the D130F top plate to accomodate a wider variety of mounting techniques (i.e., idiots who use torque wrenches to flatten these frames onto a warped baffle board).

Harvey Gerst

9/7/96 alt.guitar.amps

I saw a lot of D130's come through with fried voice coils that were running off a 12 Watt Williamson amp during the 50's and 60's. Integrated music from HiFi systems caused one kind of problem - using the D130 as a musical instrument speaker created other problems.

That's why I suggested the D130F (which was a redesigned D130), made expressly for musical instrument amps, as were the D110F (a totally new design), the D120F (a redesign of the D131), and the D140F (a new design using existing parts).

Power specifications for the F series were nominally 35 to about 60 Watts. How did I arrive at these figures? Pretty simple, I played guitar and bass through them and kept increasing the power till they blew. Then I downrated them from the power that fried them. Pretty hi-tech, huh? It seemed to work pretty well (of course we didn't have synth players back then).

The major amp manufacturers back then were Fender, Sunn, Kustom, and Ampeg. Rickenbacher and Mosrite also bought some, but nowhere near the volume of the other amp makers. All had JBL speaker options.

And yes, the "F" stood for Fender, since they were the largest single buyer, and also distributed the F series to music stores. They had no part in the design or the idea for the new series, I am solely to blame
for that.

Harvey Gerst

9/11/96 alt.guitar.amps

Q. Dick Dale seems to be the one claiming Fender went to JBL on behalf of him. In "Fender Sound Heard Around the World" he's quoted as saying the "F was invented as a result of melting voice coils & destroying surrounds". It's also stated that "the aluminum dust cover was Leo's idea". In his 9/96 GP interview he talks of the 'Dick Dale' kit available from JBL which includes a larger magnet, larger voice coil, thicker wires, aluminum dust cover, & rubberized front rim which brings the speaker (presumably a D130) up to Dick Dale & Fender specs! I'll be 'kind' and say that he comes off as 'a bit arrogant' in the interview!

A. I never had the honor of meeting or talking to Dick Dale, so I'd have to say that perhaps his memory has been clouded by the passing years. It's true that the JBL F series was partly about improving the current 2 models being used by Fender and others, namely the D130 and D131. It was my proposal to expand the line of speakers and at the same time, make some refinements to those speakers to make them more suitable to the guitar market. Here's what I did and why:

Opened the voice coil gap slightly on the D130F to allow more tolerance in mounting. Most people didn't realize that even though 8 mounting holes were available, only using four is the recommended mounting. And you don't screw them down tight to the board - that warps the frame. You use two fingers to do the final tightening - the casket will them complete the seal. When you warp the frame by overtightening, the voice coil can go out of round and eventually drag and short out. I opened the gap slightly to allow for this problem with just a very slight loss in efficiency - less than 1 dB.

Did the same thing on the D131 (and renamed as the D120F).

Using parts from the D130A and D150 woofers, I created a new woofer designed for bass guitar applications called the D140F. This had a copper voice coil and an aluminum dome.

Using the magnet assembly from the D123 and the basket from an LE-10, I added the D110F to complete the line of musical instrument speakers.

The surrounds were NOT "rubberized". JBL had developed a high viscosity coating to add to the existing hifi line of speakers that reduced ringing. I used it for a different reason. The hifi speaker surrounds dried out when exposed to excessive sunlight and heat, and I reasoned the viscose coating (we called it "goop" back then) would help prevent that.

Q. The other reference to Fender going to JBL was in conjunction with the development of the 1959 Vibrasonic. In Morrish's Fender amp book - Bill Carson recalls testing a protype JBL with a copper instead of aluminum voice coil & a thin paper cone? Can you shed some light on this obscure piece of JBL history?

A. Bill's probably refering to the D130A which was simply a standard JBL woofer at the time - all the woofers had copper voice coils. The 130A was basically a D130 with a copper voice coil and a paper dome and was used in the 001 system primarily (D130A, N1200 xover, and 175DLH driver/horm assembly). I felt the cone was too light for bass guitar and we wound up using the cone from the 150 woofer, a heavier unit. The duraluminum dome was added to the D140F, instead of the paper dome for cosmetic reasons at first, but later proved useful in adding a little more top end to the bass (not much though).

Q. regarding power ratings, I checked my official(3/70) JBL spec sheet for the F models and the 110F, 120F, & 130F are all rated at 100W continuous, the 140F @ 150W continuous. JBL defines 'continuous power' in my 4311B spec sheet as 3dB greater than RMS which would put the RMS rating of a D130F at 50W. On the other hand, D120Fs & D130Fs ran reliably in Showman 12s, Showman 15s, and early Boogies at considerably more power, so Mr. Gerst's & JBL's ratings are not marketing hype! It also appears that the 120F & 130F use identical magnet structures @ 11 pounds, 12,000 gauss flux density, and 275,000 maxwells total flux.

A. The D120F and the D130F, like their close cousins, the D130 and D131, all shared the same voice coil, dome, spider, and magnet assembies, except for the slightly wider gap on the top plate. I think the flux density was really around 11,700 gauss or so on the 120F & 130F because of the slightly enlarged gap, mentioned earlier.

Power handling was always a touchy subject and I just basically guessed at what I thought it could handle, based on normal playing. It was a little tricky since we were dealing with rock, country, jazz, and blues players and the power handling figures were just suggestions, regardless of how official the spec sheet looked.

The D130 and the D130F were essentially the SAME speaker. Exactly the same voice coil, cone, spider assembly, magnet, basket. The only things I did to the F are listed in a previous post, along with my reasons for doing them.

I revised the guitar ratings since those D130 ratings were for INTEGRATED music, like a symphony or a full band playing from the radio, tape or a record. The rating for a single live instrument like a guitar is much different, since there is nothing below 80 Hz or above 5 or 6 KHz coming out of a guitar (at least back then). A D130F (or a D130) could easily live with a higher power rating and we/JBL/I adjusted the rating accordingly. The new rating would also apply to a JBL D130 if used for that purpose.

If you had called JBL back then, you would have been transferred to me and that is what I would have told you. Since I was in charge of that division, I was responsible for creating those ratings and that was
our/my official position on the subject. As far as power handling, there was no difference - the rating was changed to more accurately reflect what the D130 or D130F could handle if used with a guitar as the source.

The lower rating also still applied if either speaker was used for full range music reproduction. These were my "babies" and if you want to disagree with me, that's fine. If you were at JBL at the time I was designing these, we could have had some rousing discussions about it. And besides, I think I also wrote those spec sheets for the D130 as well.

Q. A couple more Q's & I'll leave you alone

- Didn't know the D140F has a copper voice coil - is it an edgewound ribbon like the aluminum coils? What were the reason(s) for using copper (vs. aluminum) in the D140F?

A. Yes, the D140F had an edgewound copper ribbon voice coil. Copper has better heat conductivity than aluminum (think pots and pans) but it's heavier and not as responsive to high frequencies, due to it's weight. For use in woofers, copper is the wire of choice.

Actually, had I thought about it some more, I should have probably made the D140F more of a full range speaker, but it was basically designed as a replacement for people using D130A woofers for live music.

Harvey Gerst

[This message was edited by Jon Light on 07 December 2004 at 06:21 PM.]

Joe Alterio · From: Irvington, Indiana

quote:
Power handling was always a touchy subject and I just basically guessed at what I thought it could handle....the power handling figures were just suggestions, regardless of how official the spec sheet looked.

Well, there we have it!

Thanks for posting this Jon!

[This message was edited by Joe Alterio on 07 December 2004 at 07:33 PM.]

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