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Preamp connection to multiple powered subwoofers

I'm trying to understand how those of you who have multiple, say four, powered subwoofers in your 2-channel audio systems feed the signal from your preamplifier to these amplifiers in addition to driving your main speakers. In addition to the physical connectivity, I'm also wondering how is the impedance matching between the preamp output impedance and the combined input impedances of these multiple amplifiers is addressed. Using my system as example, my preamp has two parallel outputs rated at 600 Ohms with one set driving a tube amplifier rated at 100K Ohms. Would the second output be shared across four powered subwoofers, most likely Class D with generally low input impedance around 10K-20K Ohms? Or folks mostly use the high level speaker connections through the main speakers and split through to the rest of the subwoofers?  I have the same question for those running passive subwoofers. Do you use the second preamp output to drive a dedicated 4-channel amplifier and out to the subwoofers, and if so, how do you handle the phase, gain, and frequency adjustments across the four subwoofers.
Appreciate any input.
128x128kalali
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almarg
9,670 posts
 
Thank you kindly, Chris (@cal3713 ).

@kalali, the suggestion by @koestner of a buffer stage is an excellent one. A number of possibilities were discussed in the following thread, most notably IMO the iFi micro iTube2:

https://forum.audiogon.com/discussions/impedance-matching-question

The micro iTube2 is available at B&H Photo Video for $399.

Also, a few years ago another member reported excellent results using a custom made tube-based buffer stage in conjunction with his Audio Research Ref 6 preamp to drive a powered sub. (That preamp has a 20K minimum load recommendation, which was not met when using the preamp to drive both the sub and his main power amp). It was custom made for him by Tom Tutay of Transition Audio Design in Florida. Tom does not have a website as far as I am aware, but his contact info should be findable via a Google search. I don't recall the price, but I believe it was somewhere between $500 and $1K.

Good luck. Best regards,
-- Al
 
oem-wheels
196 posts
 
the perfect solution is to place a good crossover behind the preamp.. the bass section from the crossover will feed a 1 input / 4 output amplifier, all output from bass amp being fed the same signal.. bass amp should be class a/b type.. in this way ….. 
- preamp only driving one component
- main amp driving the R & L speakers duties are lightened up not having to produce the lower frequencies = better performance..
- subwoofers should all still receive a good strong signal.. 

Does anyone of such an amp (for bass) ????
kalali's avatar
kalali OP
1,977 posts
 
Not sure if I quite follow the crossover arrangement but the use of a buffer such as iFi micro iTube2 seems quite logical, especially with its 1M ohm input impedance and ~150 ohm output impedance in direct buffer mode. I’ll probably start with a two subwoofer set up and see how it sounds and add more if needed. My other challenge is to pick the right driver(s), most probably an 8" or 10" to better blend with my Omega Alnico single drivers.
Thank you all or your input.
recluse
268 posts
 
Wouldn't the simplest approach be to daisy chain your subs from your main speaker input posts, if that is an option?
oem-wheels
196 posts
 
Whats hard to follow with the crossover arrangement .? You split the  frequency coming out of the preamp before it hits the amps. Say at 80Hz. The upper frequency gets fed to the amp driving the R & L speakers . And the 80Hz below gets fed to the bass amp. 
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