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JBL D120's vs. E120's.

10/14/1998 3:07 AM
V. Gautam
JBL D120's vs. E120's.
I was wondering what the difference between JBL D120's and E120's are. If I'm not mistaken, the D120 is an older model, generally rated at 40-100 watts depending on the date manufactured. Is the E120 a newer model, and isn't it rated at 150 watts? How does the sound differ between the two models? Is there an appreciable difference?  
Thanks for any info.
10/14/1998 4:47 AM

I'm not nearly as well-informed as most of the contributors to this BBS, but I can offer a little lay-advice.  
"D" stands for initials of the self-proclaimed rock-amp pioneer that (according to legend) assisted Mr.'s Lansing and Fender in the devwelopment of the BF Dual Showman amp. That would be Mr. Dick Dale, King of the Surf Guitar. The sound of a D-140 is in accordance with His tone philosophy--relentlessly clean, extremely loud, and painfully bright. Humongous ceramic magnets and aluminum dustcaps, with a tone that stays absolutely positively clean right up until voicecoil meltdown. Peavey's Black Widow seems to be a copy of this design.  
I used to have a "fridge" Dual Showman 2x15 sealed cab with D-140's that I used for country bass gigs, that is before I realized I was going to get a hernia from lugging it, or else tinnitus from the Ginsu-knife high end.  
Bear in mind, when Dick Dale was playing at his club in SoCal to crowds of 2,000 or so in the 'sixties, he was using SIX 100watt Dual Showman Heads driving TWELVE D-140 fifteen inch speakers. Can you say "tympanic membrane hemmorrhage," kiddies?  
Enough nostalgic hystrionics. I have no personal empirical experience with the E line of JBL's. From word-of-mouth hearsay, I believe it is a "second choice" for, say, steel-guitar players who cannot find 4-ohm D-140's to put in their Session 400 amps. Still very loud and very clean tone. I also think E- series speakers are (or were) included in some of JBL's P.A. systems.  
Hopefully someone more knowledgeable will fill in the gaps I have left.  
10/14/1998 8:11 PM
Fred G.

The D-120 is an older model; there was a K-120 series which followed this, and then came the E-series, I believe.  
The D-120's aren't as bright as the K-120's. I have 2 K-120's I bought back in the '70's, when a Fender Twin Reverb loaded with JBL's was considered to be one version of "tone heaven". I personally don't think the JBL's are excessively bright - they just give you a little headroom in the high end ( heh, heh). A friend of mine has a couple of D-120's; they are warmer, with a little more midrange. Personaly, I like the sound of the D's a little better. I would guess that the E-120's are at least as bright as my K-120's. The K-120 series rated out at 150 watts, so the E's must be rated for at least that much.  
I have used my JBL's with Marshalls, Fenders, and Peaveys over the years, and have always found them to be an improvement over the stock speakers in those amps (except for the Greenbacks in a Marshall combo I had once). However, I have kind of outgrown them, and am currently looking into the Weber speaker products now available. But it seems that I always go back to the JBL's.  
Hope this helps,  
Fred G.
10/15/1998 12:17 AM

According to  
Manf/  Dia  Pwr   Z  SPLdB  Fs   Vas     xmax
Mod RMS ohm 1W/1m Hz cuft Qts inch  
D123 12" 50W 8 96dB 45 4.8 0.45 0.10  
K120 12" 100W 8 100dB 50 4.3 0.20 0.06  
E120-8 12" 150W 8 101dB 60 2.8 0.17 0.12  
E120-16 12" 150W 16 101dB 60 2.8 0.17 0.12
Don't ask me what all those parameters mean!  
You might also like to search for posts by Harvey Gerst (who designed the D series) and mail him.  
10/15/1998 7:28 PM
Reid Kneeland
Speaker Parameters 101 (was Re: JBL D120's vs. E120's. )
>Don't ask me what all those parameters mean!  
Ask me! (I rarely know enough to show off; please indulge me.)  
I assume that the first two columns are obvious to eveyone. The third is the maximum continuous power that the speaker can take without burning up the voice coil (note that this says nothing about distortion level, just damage!). Peak power handling is much higher than this number, of course. The next is the nomial impedance, "Z". It's "nominal" because speaker impedance actually varies with frequency - there's a resonant peak near the bottom of its frequency range where impedance is quite high; the impedance then falls off quickly, and slowly begins to rise again (as the inductive reactance of the voice coil comes into play). The next column is efficiency, or how loudly the speaker will play for a given input. Anything over 90 is a fairly efficient speaker, over 95 is very efficient, and over 100 is extremely efficient. (The units given here are decibels, measured from a distance of one meter, with an input of 1 Watt). Musical instrument speakers are almost always well over 90, HiFi speakers can be in the 80s, rarely lower.  
Still with me? Good! The next column, Fs, is the resonant frequency, at which the above-metioned impedance peak occurs. Since the lowest note on a guitar is around 82 Hz, the examples given would all be fine for a guitar amp (for bass, HiFi, or PA, it gets stickier). "Vas" refers to the compliance of the speaker, how "stiff" or "floppy" the suspension is, and its expressed as the equivalent volume of air that would have the same compliance (or compressability). That's why the units are cubic feet (sometimes given as liters). Qts is the total "Q" of the speaker, which is a little hard to explain, but LOOSELY speaking is the size of the impedance peak. Finally comes xmax, which is the maximum linear excursion, or how far back and forth the speaker can go without distorting (too badly). Usually it's a +/- number.  
So how do you use these numbers? The easiest way is with software (such as the shareware program PerfectBox). The numbers (assuming they are accurate!!!) allow you to predict what the frequency response and effiency of the speaker will be in a particular cabinet, especially the low bass performance, which is the range most affected by cabinet factors (but again, isn't as big an issue for guitar). The xmax number is especially useful for bass applications. because at the lowest part of its range, a speaker's output is usually limited more by this parameter than by its power-handling number (in other words, at low frequencies the speaker will bottom out and distort before the heat in the voice coil gets dangerously high).  
For guitar amps, as long as Fs is 60 or lower, you can pretty much ignore the last three columns.  
Conspicuously absent from this table is any indication of the *high* frequency response limts of these drivers!  
For more information, get a copy of The Loudspeaker Design Cookbook, by Vance Dickason.
10/15/1998 9:27 PM

I have been playing bass through one JBL D140 and one JBL K140 loaded in identical 1 - 15" cabs for several years. I have always preferred the D140 and now use it solo (less hauling at gig-time). I was told that the speakers are identical exept that the D series have Alnico magnets and the K and E's have ceramic. Anyone know if this is true?
10/16/1998 6:38 PM

When looking through published driver parameters, is there a rule-of-thumb range for Qts & Vas that would be a good indication the driver would be suitable for an open back enclosure, i.e., no air spring required to keep it in check?  
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