Bob - we promise not to call you Bob TMF (the measurement freak).
 
I'm dying to know what you found out about sustain blocks - no measurements required.

I created a monster!!! Anyway. . . I justed scored a Stewart World 1.6 an e-bay for $361.00. Now I'm looking for an AccuGroove Tri210L or an El Whappo. Can't find any in the SF Bay area. Keep your ears open.

Just my 2 cents for a useful damping factor:
 
Just do this math: damping factor is calulated by speaker impedance divided by the reactive load impedance of the PA. But the reactive load impedance of the PA is connected to the speakers by a cable so you have to add the cable resistance (including the cables in the box and all connections). The reactive load impedance of the PA cannot be lower than zero so the overall impedance cannot be lower than the cable resistance. This means the maximum damping factor cannot be higher than speaker impedance divided by cable resistance. A total cable and connector resistance of 0.02 Ohms is a very optimistic assumption. With an 8Ohm Speaker this results to a damping factor of 8/0.02 = 400. With a 4 Ohm Speaker its 4/0.02 = 200. If your PA has a higher damping factor you either will not hear it or you need lower resistance cables. I don't see why I should ask for a PA with a damping factor higher than 500.
 
In terms of slew rate: let's guess you want to kill any band member with pure bass volume, will 2000 Watt @ 8 Ohm be enough for you ? Ok, let's assume that. To generate this power (RMS) at 8 Ohms you need 127 Volts RMS or 179 Volts rail-to-rail (it's less at 4 Ohms). In case your Alembic goes up to 20kHz your Amp should be able to provide a complete rail-to-rail ramp in a 50us/2*PI time. This means it should be able to provide a slew rate of approx. 22.5 Volts/usec. What for do I need a higher slew rate ?
 
Please correct me if I am wrong. It's 12pm here in Germany, I will go to sleep.

High damping factor = tight speaker control as mentioned above.  But practically speaking, higher damping factor doesn't necessarily mean better sound.  
 
The attention paid to damping factor dates back to the dawn of solid state amps.  The output impedance characteristics of a vacuum tube circuit are very different than a solid state output stage.  Tube amps require an output transformer to match their output to the speaker.  There's no direct wire connection between the tube and the speaker, it's a magno-electric connection happening in the transformer.  
 
The effect of that transformer is that damping factor of tube amps is very low - I believe 10-50 would be pretty typical.  The tube amp stages aren't as fast or tight as solid state and that's a significant part of tube warmth.  There are a few really expensive direct-coupled tube amps which have no intervening transformer.
 
When solid state amps started coming around damping factor was a good way market them relative to tube amps.  
 
Generally, a fast, high-skew capable amp should be the best, but I  believe there are certain kinds of distortion that are associated with high-slew amp designs.  They may not be audible relative to the difference in sound between tubes and solid state.

So ...this would be something interesting???
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=29922&item=3721176460&rd=1&ssPageName=WDVW

i always wondered what high damping factor meant i dont run a complex system yet but this will be useful for future purchaces thanks
andrew

Paul,
 
I think you can't go wrong in buying a professional PA from any of the major brands like QSC, Stewart, Crown, Mackie, Peavey, Dynacord, EV or ... you name it. Their electrical durability has been prooved by thousands of customers. The differences which may be more important for you are size, weight, fan noise and type of Inputs or Outputs. For me it was also important that the PA has a low cut filter, a peak limiter and a soft-start (no loud speaker plop when it's switched on or off) to protect my speakers. But this is more or less standard today.

John, Bass Central sells El Whappo.
www.basscentral.com
 
Sam

John:  2 months ago or so there were several Whappos on Ebay being sold by individuals who needed to reduce their speaker investments.  All were almost new or very good with prices ranging from $1,100 to $1,600.  There were also one or two tri series cabs on sale.  There was a flurry of activity with about 3 different sellers - then nothing since.  I found it so interesting to watch that I put Accugroove into my favorite searches.  You should do that.  It's the only way you'll find Accugrooves at a discount.
 
Bill

John,
Guitar Showcase had an El Whappo at one time. Maybe it's gone now. I was at Gelb (Redwood City) on Saturday, and they had two of the smaller cabs. A Tri 110 and Tri 210.  
 
- nate.