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View Full Version : Bi-amping 4333As- amp options, etc.



Fred Sanford
12-08-2007, 01:59 PM
OK, here's some of the brainstorming I've been doing. And, yes, I know there will be suggestions of, "Why don't you try them all and see what sounds best to you?", and that may be what ultimately happens. However, this is right smack in the middle of our living space, so a clear plan would be smoother all around. I'm looking to bi-amp my 4333As with some assortment of the gear I've got lying around here, and looking for opinions on which approach might be best to start with. The feed/preamp will likely be a split from the local surround processor, which I admit might become the weak link (quality-wise) in the plan.

Crossover is an old pro Ashly SC-22, no metering. Plan is to set this up & upgrade to modern ASAP. This will be put through its paces in the control room before re-wiring all this, and if it's sucking I'll put this off until I can spring for a modern crossover. It's one of those, "it was working fine when I put it in storage" things. Specs here:

SC-22, circa 1984
Stereo 2-way crossover, 12dB/octave filters,
Crossover frequency range-160Hz--8KHz,
Rolloff = 1.5dB--12dB
Input Z = 10K ohm balanced
Output Z = 50 ohm unbalanced
Max in/out level = +20dB
THD = <0.05%, @+10dBV 20-20KHz
Hum & Noise = -90dBV
Power Consumption = 5W

Amp options available:

Adcom 2535 (two of them). Current front-runners, mostly 'cause: A] they're aesthetically acceptable to be visible in the living room, and: B] I can't think of any other use for them here. Actually, the only minor aesthetic issue is that they're two different ages, so front panel layouts & labeling are slightly different. They've got four 60W amps in each, but the first two amps in each can be set to bridged. I'm figuring on setting them up as dedicated left & right amps, each with the bridged 200WPC for the 15s, and one of the remaining 60W amps powering mids/highs and one sitting idle. Not knowing too much about these particular amps, my only reservation here is that running the lows & mids/highs from a single amp seems to somewhat defeat the purpose of bi-amping (is the low amp robbing the mids/highs of some of its resources?).

Crown DC300A. Not a bad choice for the lows, I'd think, but it's fugly. Could be located in my studio's control room, which is directly below this Living Room system- interconnects & speaker cables would still be reasonably short. Easy enough to remotely power it on & off in sequence, too, but it'd be with the volume controls already up (hmmm...). This amp is currently idle, sitting as a spare in case there's call for a quick little PA system rental or loaner. I have a DC-sensing protection circuit box to run in-line after this amp, just in case.

JBL/Urei 6260. Currently slated to run the vocal/keyboard mains in my small recording/rehearsal studio (JBL TR225s), which is likely to work very well but be a bit of a waste of this amp. I'd think this would do very well for the 15s, and be high quality (if overkill) for the mids/highs. Same locating situations as mentioned for the Crown, including the power-up-&-down-while-volume-is-up thing.

Yamaha P2100 (one or two of them). I have had four of these for 20+ years now, and love them. Number One runs my control room monitors (L110s), and Number Two is set to run my small wedge monitors for drummer & singer. Number Three is idle/spare, and Number Four is slated for powering a set of L100s as playback in the studio, but that could potentially be replaced with the Crown. Upside is, I love the transparency and character of the high end with these amps. Downside, I think the ~85WPC rating is a bit low for the 15s. Can be remotely located, or possibly prettied-up enough to live locally.

...so, there you go. Any one of these amps could run the 4333As full-range and be impressive, probably, since the speakers are so efficient and sound great now on a Yamaha receiver's power (~100WPC). Any one of them could also be sold to finance a nicer crossover- that just occurred to me, too. I think writing this out has convinced me to leave the plan in place (Adcoms), but since it's already typed let's see what feedback there is out there.

#1 = Adcom & Adcom
#2 = Crown (lows) & Yamaha (highs)
#3 = dunno...

Thanks in advance,

je

speakerdave
12-08-2007, 02:53 PM
When that speaker is switched to bi-amp mode the high pass and filtering for the treble horn and tweeter stay in the circuit. Therefore you do not need to use an active external crossover to roll off the lows under the horn. Just, in effect, biwire into those terminals for the highs and use the external crossover to set a low pass at 800 Hz for the woofers. That will give you more flexibility in choice of crossover hardware because you will not need to be concerned with some aspects of the sound quality of the instrument chosen. JBL suggests a 12 dB/octave roll off as being the standard slope closest to what is needed.

David

Fred Sanford
12-08-2007, 05:39 PM
Interesting, thanks- I hadn't noticed that I'd only need the low-pass.

je

Tweak48
12-18-2007, 06:30 PM
Not having that built in switch on my 4333 home versions (L-300s):), I use the existing crossover, but have to hard wire the LF amplifier directly into the woofer.

Tubes on top, s/s on the bottom. The best part of bi-amping is the iron-fisted control that direct coupled amp has on that big woofer. Really tight bass!!!!







http://audioheritage.org/vbulletin/attachment.php?attachmentid=8649&stc=1&d=1119662088

speakerdave
12-19-2007, 12:07 AM
The switched version of the crossover also leaves the zobel on the woofer. You might try replicating that across the terminals of your direct-wired woofer and see which way you like it.

David

Fred Sanford
05-05-2008, 10:57 AM
The system is up & running in a 'test' mode, signal flow as follows:

Pioneer Elite DVL-91, PCM output of LD/DVD/CD.

Marantz DP870, essentially being used as a level-controllable DAC. Its alternate input will eventually be getting a feed from an AV switcher in the basement, giving remote access to PCM streams from all of my music servers.

Analog signal splits here, with lows going to the Ashly for an 800Hz low-pass, then on to:

Adcom GFA 2535 4 channel power amp.

JBL 4333As.
-----------------------------------------------------

I don't think I'll be needing to add a second amp, as efficient as these speakers are I've only been able to get the Adcom's "Instantaneous Distortion Alerts" to light at levels louder than I would ever realistically play music. Nice that I have a spare, though. I ran the 1812 Overture from the Eargle On Everest CD, just beautiful how the system now handles dynamics. Adcom ran cool through all testing, doesn't seem to be any ventilation issues.

In the final configuration, I'll probably only have the Marantz visible, with the Ashly hidden behind the speakers and the Adcom downstairs (if my wife ever notices/comments on its sudden appearance in the Living Room). This setup also shares the Pioneer DVL very nicely, which means that I can choose to hear LDs or DVDs through the Yamaha/Canton surround system or the Marantz/Adcom/JBL 2-channel system while video signal always goes directly to the HDTV. Sweet. It also means that my wife views the Pioneer as "His DVD" and heads for the Sony progressive scan unit for her DVD and CD uses. Works out well.

Still need to run some tests & tweak the x-over freq and levels, but off-the-cuff settings have resulted in a very good balance, with only minor noise audible in the 15s- likely generated by the crossover. I'll play with I/O levels to try to minimize that, and ultimately upgrade the x-over...this one has been with me since a PA system in 1987 or so. Having the 4333As on the floor is messing with the tonal balance I think, but for now that's where they're staying 'til I can get some custom cabinetry made up.

Thanks for all the advice & inspiration so far. We've got guests coming soon, so pics will follow once I've finished dressing cables & dusting off my 'bachelor-black' gear. :bouncy:

je

Tim Rinkerman
06-10-2008, 08:33 AM
I'm using a BGW 750A for the lows, and a Marantz 250 for the highs of my 4333's. The crossover is an Audioarts 4100 2 channel,2 way.

Fred Sanford
06-10-2008, 08:50 AM
I'm using a BGW 750A for the lows, and a Marantz 250 for the highs of my 4333's. The crossover is an Audioarts 4100 2 channel,2 way.

I've got the mono version of that crossover, I think (2100A), used for PA subs in the past. Is that a 12dB slope? I forget.

je

subwoof
06-10-2008, 05:07 PM
Hmmmmmm

I have (12) 6230's and (8) 6290's from an install ( with caps over the knobless volume controls ).

If you used the 6260, they would match and behave the same power-up wise.

Crossover wise maybe a simple homebrew 600ohm passive network stuck in front of the LF amp would work. it's only 3-4 components...

Hmmmm

Fred Sanford
06-10-2008, 06:03 PM
Hmmmmmm

I have (12) 6230's and (8) 6290's from an install ( with caps over the knobless volume controls ).

If you used the 6260, they would match and behave the same power-up wise.

Crossover wise maybe a simple homebrew 600ohm passive network stuck in front of the LF amp would work. it's only 3-4 components...

Hmmmm

I'd thought about the simple line-level passive approach for the lows, but the Ashly checked out OK with just a bit of cleaning so I went with it figuring it gave a bit of adjustability while figgering things out.

The Adcom's been sounding good, I just have to take the time to adjust my low-mid-hi balances & live with that for a while, see where I'm at. Room's still way too live, we haven't decided what to do with decorating the walls yet.

Next $$ is probably getting thrown at the tired 2231s to make them into healthy & robust 2235s.

je

Tim Rinkerman
06-11-2008, 07:14 AM
Fred,
It is a 12 db.per octave filter, but they have a knob for lowering the slope/depth of the crossover point. I always thought it was a really good not sounding(as in transparent) crossover. It does what it does really well and no more.
I re-surrounded my 2231's when I first got them, the surrounds were long gone. One of the cones had been mis shapen slightly by their de-stallers, but didn't rub, so I re formed it and it was good for several years, then developed a buzz. Not to make the story too long, but wheen I took it apart, the mass ring had just come loose..(%^&&* that AC/DC disc!!)but the coil was perfect. The new cone was a bit "stiffer sounding", for about the first 2 months, now it sounds identical to it's 30+ year old brother! My point is if the coils don't make any noise, the surrounds make all the difference in the world, in terms of refreshing them, and a heck of alot less expensive. Tim

subwoof
06-11-2008, 07:34 AM
I had my speaker reconer re-do the surrounds on all 6 2231 / 136A and they are just fine. I get my surrounds from Mr cobb so there is no question of correctness.

When I have them done I pull the old kit out of the frame ( use MEK and a few tools ) so the coil can be inspected, mag gap cleaned of junk and coil former checked on a jig for roundness. Then it's reinstalled just like a recone kit *with* the shim so it's perfectly centered.

This way there is no question that it will last a long time - and yes I have seen a few mass rings with a little "tingle" to them. When the cone is slammed inwards it pushes against the ring and eventually will loosen them or rip away one layer of paper..:(

It wasn't AC-DC that did in the 136's - it was Iron man.

dunht dunht dunht dunht dunht dunht dunht dunht

...tink...

Fred Sanford
06-11-2008, 07:56 AM
Thanks for looking out for me, these are working for now but I think could be better. My 15s are mismatched and tired. These 4333As were Clive Davis', from his office/listening room at Arista Records and got lots of miles on them. They were then abused/enjoyed by a teenage music student, even playing synth through them. Then, left to rot in a garage for years.

One of the 2231s was replaced at some point (original sn 7038, replacement sn 24103), and both were re-foamed a few years ago. Both spiders are obviously sagging, and to me there's an audible difference between the two. Could still be binding posts (have yet to replace the OEM), but either way I'm pretty confident (mostly because of the spiders) that a re-cone & regauss is in order.

je