View Full Version : Amp for bass driver

Ken Schwarz
08-24-2003, 08:40 PM

I am planning to try bi-amping my 4344 Mk2's. JBL recommends an external crossover at 290Hz. Everything below that goes to an ME-150, which is a proprietary driver that replaced the 2235 in the original 4344.

I will be using a 10W SET on upper three drivers. The output impedance of my particular amp is 1.5 Ohms.

What should I look for in the amp for the bass? Should I try to find one with a comparable output impedance to the upper range amp? Should I get an inexpensive/used pro amp with plenty of power? Suggestions?


- Ken

08-24-2003, 09:12 PM
Uh, oh...

You should, if you haven't already, peruse this most interesting Thread: "Amplifiers are more significant than you think" Thread (http://www.audioheritage.org/vbulletin/showthread.php?s=&threadid=347). Yuri and others will likely come through with some useful "first hand opinions" (hmmm... I LIKE that one ;) ), too.

08-24-2003, 10:28 PM
Hi Ken,

"What should I look for in the amp for the bass?"

As with any large JBL LF transducer having a 4" voice coil - an amp that can dump a lot of current and can handle low impedance loads.

"Should I try to find one with a comparable output impedance to the upper range amp?"

Not unless you like that particular effect.

"Should I get an inexpensive/used pro amp with plenty of power?"

Plenty of power, plenty of current capacity.

08-26-2003, 08:22 AM
I would recommend you check out the older Yamahas (PC2002M, PC2602, etc) or Carver (PM 175,PM350, PM700). I've had exellent luck with both. I drive my L250's with a PC2002M and my home theater sub with a (bridged) PM175. Others here could recommend similar QCS or Crown units I'm sure....

I'd say that in general, a good used pro amp will deliver everything you're looking for at 1/10 the price of an "audiophile" amplifier. They are built tough and they will likely last a lifetime if well cared for.


08-26-2003, 04:29 PM
In case anyone cares, here's the latest blurb from JBL:

Tom Loizeaux
08-26-2003, 06:50 PM
Adcom and B&K make quality high current power amps that are quite affordable and a good value. These will drive your JBL woofers to optimum performance. ( You can always go bigger and better ie: Mark Levinson, etc.) I feel 100 watts per channel is the MINIMUM you should go with. Remember, JBL said that your power amp should be able to deliver double the wattage capacity of your speaker if you want high level, monitor type playback.


08-26-2003, 07:01 PM
On the jbls woofers maybe try a good fast maybe a bit dry sounding Lf amp. Adcom 555II will suprise you. Thats agreat Bi amp amp. the highs and mids are very forward.The 5802 and 5500 sound VERY diffrent and dont havr quite the speed. I had a 565 mon block pair side by side to a krell ksa300S and the adcom sounded 90% the same on control and slam ( No Kidding ) On B&W 801. Bryston makes some nice amps too. Im now using ( Soon to Be Replaced ) crown XLS 602 that sounds just great. Its very dry sounding so some recordings sound anemic but then some have much greater sounding lowend. For the money the 565 will do great.

scott fitlin
08-26-2003, 07:30 PM
Bryston makes great stuff, the 4B SST would be nice on your bottom!

Another amp you might want to try is a McIntosh! Yes, Mc! Seek out an older MC 2200 or a MC 2300! You would be surprised at the way these things sound!

08-26-2003, 08:57 PM
It's an interesting suggestion. I use the MC2200 to drive my Jubals. It's a very musical amp. I can listen to it for hours while working at the computer, etc, but I know if a plug in my Audio Research VT60 I will stop work and go sit in the sweet spot for who knows how long.
It is one of the second generation of McIntosh sand amps which have output transformers. The company used to tout them as a method of protecting speakers from solid states amps that can get into thermal runaway, which McIntosh rarely do if ever, but I think they also contribute to the smoothness of sound because they tend to smooth the load impedance. What is sacrificed is the super low output impedance that transformerless amps can have. The damping ratio is rated at 16 to 30 depending on the output tap used. It seems to give solid, competent bass, but tight or punchy I can't really judge because I use a classic tube preamp which I know is a little soft.

Before I got this amp I used the MC250, which is first generation solid state, also with transformers, for years. The MC2200 is a clear improvement. There is a smaller amp of the same generation called, I think, the MC2125, which you may find more appropriate. With a 10 watt SE amp on top you may not be driving the midrange and treble to a level that would require full power on the lows. Still the reserve power never hurts.



Ken Schwarz
08-26-2003, 09:32 PM
Thanks very much for the replies and suggestions!

One thing that still concerns me is a possible discontinuity in response if the output impedances of the bass and treble amps is very different. Do folks have experience using solid state on the bass crossing over to SET on the treble at around 300 Hz? Does adjustment of overall level of the amps give you enough control to make the transition seamless?

scott fitlin
08-26-2003, 11:14 PM
As long as your active crossover has output level controls that would be where you adjust separate bass/mid/high levels to balance your system!

If you xover doesnt have this, then you need to use the amplifier front panel gain controls, but if you can its best to do it at the xover and run your amp gains wide open! You get the best signal to noise ratio this way! But, yes, the amps gain controls will be sufficient to balance your setup!

Funny that the McIntosh MC-2125 was mentioned! Thats exactly the amp Im going to use to run my 16 JBL 2402,s! However, i would think the slightly higher power of the MC-2200 would be somewhat better to run the low end of Kens speakers!

The output impedance of your SET amp shouldnt be a problem unless the amps output impedance is really high! Say 2 ohms! I think as long as its under an ohm you will be OK.

BTW, SpeakerDave, I thought about getting an Audio Research to run my tweeters! They are nice sounding amps!

Alex Lancaster
08-27-2003, 07:22 AM

How is Your setup with 16 2402's, and what is the rest of the setup?

Really curious,


scott fitlin
08-27-2003, 11:32 AM
the 2402,s are mounted in circular arrays of 4, and wired in series parallel. I am currently using two Crown power line 2 amps to run the tweeters. This is 50wpc at 8 ohms! A nominal 12.5 watts per bullet! I cross them over at 7K 18DB Butterworth!

With the MC I will parallel two arrays per channel, yeilding a nominal impedance of 4 ohms! The MC should sound sweeter on the highs! And this will be a nominal 15 watts per tweeter!

BTW, It has been my experience with JBL slots and bullets, that they dont like alot of power! They were designed when amp power was much smaller, and the power ratios I have described work really well with these tweeters. No harshness, and they make plenty of sound with this little bit of power!

08-27-2003, 01:23 PM
"One thing that still concerns me is a possible discontinuity in response if the output impedances of the bass and treble amps is very different. Do folks have experience using solid state on the bass crossing over to SET on the treble at around 300 Hz? Does adjustment of overall level of the amps give you enough control to make the transition seamless?"


I don't know if anyone else can answer these questions for you, and you may be at the point when it's time to start trying things if you can get your hands on some amps. As for trying to predict a match based on some technical description of an amp--I'm doubtful. On that basis you might choose a McIntosh amp with output transformers because it has a damping factor that is close to that of a lot of tube amps. But the result may not be as you predict.

I would pay more attention to what people have to say about the sonic character of the amps they have experience with. If what you like about your tube amps is their detailed, life-like presentation, then you would want to look for the same qualities in a bass amp, no matter how it is achieved technically. I think in a bass amp these qualities are achieved with high damping factor and high current capability and I would go so far as to make a specific recommendation within your power requirements, and that is the Crown D150 which you can get for about $200, plus or minus $30-40. A lot of people on this forum will say that is too small, and if you agree with them, go for the Crown D300 for about $100 more. I'm sure there are many other suitable amps; these are the ones I'm familiar with.

As I've said, I use the early McIntosh solid state amps myself, but frankly, I see them only as a decent compromise for full range.


"BTW, SpeakerDave, I thought about getting an Audio Research to run my tweeters! They are nice sounding amps!"

Yes, they are very fine, although this particular one I have, the VT60, I wouldn't work very hard into a 4 ohm load. The thing that impresses me, though, is that these JBL speakers can play that song too, besides all the heavy lifting they can do in other applications, and it sounds like Ken is finding that they can go to the SET zone as well.



scott fitlin
08-27-2003, 11:41 PM
The D-150A is perfect for mids and an old white face DC-300A happens to sound good on woofers IF its enough power for you! This will give you a punchy low end!

I like the white face 150A and DC-300A from 78 and 79 the best!

I dont like the blackface series II D 150,s and 300,s!

08-28-2003, 12:07 AM
Yeah--those were the ones I meant. I'm not familiar with the Series II amps.


scott fitlin
08-28-2003, 12:17 AM
Originally posted by speakerdave
Yeah--those were the ones I meant. I'm not familiar with the Series II amps.

David I say this because when Crown introduced the black face series II run of the legendary D series amplifiers they neglected to tell us that they had switched to a different output transistor! And because of this switch the D series amps never had the same amount of steam their predecessors were known for. You run a series II against a white face w/IOC indicators 79 vintage DC-300A and you willl see the black face doesnt have the same BALLS as the older generation! YOU CAN HEAR THE DIFFERENCE!

All the years I ran DC-300A,s on my Altec 421-8LF,s and a Crown D-150A on six JBL 2395 lens horns with 2441 drivers! very good sound indeed!

I honestly couldnt see anyone being unhappy with these running JBL,s !

BUT, I still like McIntosh for its musical sound in the high frequencys!

Ian Mackenzie
08-28-2003, 01:31 AM
Regards the biamp amp issue as you are running bia- amp active there is also the the power split ratio to consider and this will ultimatly limit your available headroom.

To explain this concept the bi amp crossover point in the 4344 is about 50/50% power split on normal program material for each amp. The rated sensitivity is 95 db for the system and as you are using 10 watts for the mid/high amp we can assume that this will be the limiting factor for dynamic headroom.

ie 10 watts will give you +10 db gain @ 1 metre = 105 db @ 1 metre.

Now as you are biamping in this situation we will assume you have normally equally power amps so we can work out the maximum headroom.

For example we have here 10+10 watts per box.

The peak voltage (crest factor) is the equivelant of a 40 watt amp.

Your available dynamic headroom is going to be with 40 watts =
+16 db @ 1 metre = 111 db @ 1 metre using the 10 watt SET on the mid high drivers and the 10 watt amp for the bass.

I tend to think your SET will run out of steam before the bass amp bass using the above reasoning, but bear in mind that 111 db is still loud, and that loudness is attenuated 6 db for each doubling of distance back from the speaker not taking into account reverberant conditions of your room.

If your are keen to use the SET 10 watter and this is a valve amp, I would tend to eye off a nice hifi amp with a tuneful articulate bass and warm lower mids, otherwise the lower mids and bass will tend to sound too cool relative to the presentation of the SET unless you aim high for an expensive big amp which is IMHO unnecessary.

(I tried this a while ago myself with a Cary SET 7 watter on mids and higher and PA bass amp for the woofer and the mids and top were out of character with the bass, your active xover will also need to be 1st class or you'll loose the SET's virtues)

If you are are dabbler (diy) and want the ultimate, consider a Pass Aleph 3 30+30 or Aleph 5 60+60 for your bass, they sound midway between a smoothest solid state amp and value amp and are SE.

Or like many including my self gradually scale up to bigger Alephs like the Aleph 2 100+100 pure class A and there you are in utopia IMHO. Making them is not hard, if you can plug in a soldering iron to the wall your on your way! Bi amping is not really necessary with a big enough class A amp unless you require extreme dynamics, ie you don't need to run the JBLs up loud to makem sound good, the dynamics, precision, imaging and fine detail is there in spades even at modest levels (IMHO).

Passlabs actually sell to a major JBL dealer and there is a strong synergy with both brands.

There is an absolute treasure chest of DIY information on how to make your own Aleph now at diyaudio.com and a nice gallery of projects at http://www.passdiy.com/gallery.htm

Please note I have no alliance with diyaudio.com or Passlabs but have built several of their amps and there is no going back.




08-28-2003, 08:42 AM
Sometimes the least obvious option SOUNDS best, while the one perceived (hyperbole, prestige, cost, et al) as best candidate turns out to yield HSD (HammeredSonicDung) with a given set of speakers, physical enviornment, assosiated gear, etc.)
With my pair of 2235H subs in JBL Pro-spec
cabs (ducted port, 5 Cu. FT volume, et cetera), the [stunningly IMO] best, most musical amp of many tried was an Old Colony Sound kit designed by Erno Borbeley. Early MOSFET-output design, two channels, 50 Wrms/ch. If you are not familiar with Erno, search @ Google, using this exact search term, including quotation marks:
"Erno Borbely" +amplifiers
My little project amp, which I bought off a closeout sale [ca. 1980] in Audio Amateur Mag for $215 total, was when used with the brutish 145 lb. each subs sonically warm, tight, quick, deep-going, and extremely articulate. The first time in 35 years chasing the holy grail of amps that I noticed whatever the bass instrument, EVERY discrete note played was clearlly discernable as what it was ( vs. wall-shaking tubby doses of low-end molasses...made up of mostly farty distorted harmonics).
Moral: Expect the unexpected, try to avoid preconceptions whatever their basiss, keep an open mind & ears, and TRY EVERYTHING you can beg, borrow, and steal.
To be continued: "EGAD, what what! The hyperbole IS TRUE!!!"
A quasi-rambling diatribe, in regardS to Pro Audio amps...and my success story with the Alesis Matica 500 power amplifier. Search for an easily found downloadm of the Matica Amp series' owners manual (usage/installation/tech notes etc.) : "Alesis Matica" +amplifiers
The Matica 500 IS IMHO the best amp I've heard. Believe it or not.

08-28-2003, 01:54 PM
"TRY EVERYTHING you can beg, borrow, and steal."

How true. No amount of bookreading or specification sheet reading can take the place of experience.

08-29-2003, 08:26 PM
A dude where I was working (temp, via a tech job shop) and I were frothing audio freaks and yapped ad infinitum about it. He traded his pair of 4310WX to me four a pair of L-65's. I was (am) always looking for good deals & good gear, so when he said someone he knew had an ESS preamp for sale I got a bit excited as ESS speakers were "hot" at the time, and when I looked up the preamp's price it was quite "spendy"
I was running a Marantz 7T into a pair of Dyna MKIII's, wasn't totally happy with the tone. (Does this sound familiar & even chronic?) Once again HyperBowled with the sudden ESS intrigue attack,
I managed through Stan to borrow it over a weekend for a demo.
The evaluation lasted maybe 10 minutes. I made a note that the unit should be labled P*SS, not ESS, 'cause that's how it sounded. Probably the very worst I've heard, period.
I don't recall the asking price, but $400 (c.a. 1976) (!) keeps popping up. Had I paid $50 I would have been P*SSED off about the P*SS from ESS. Not even a gig in the garage would that dog have been listenable on.
And on and on and on it seems to go blah blah blah...

P.S. I have not "upgraded" my preamp/power amp setup nor degraded its sonix since 1996. But hey, you never know!
( Advent 300 preamp section, Alesis Professional Matica 500 Dual-Channel power amp)
Alesis Matica 500 / 900 owners' manual: