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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.
kalali
kalali's avatar
kalali OP
1,977 posts
 
Thank you. Those impedance values pretty much rule out the use of the second (parallel) output from the Unlimited to drive all the powered subwoofers. I also remember reading somewhere that selecting too large uF output coupling capacitors can have some undesirable sonic side effects and the designers generally strike a balance between the size (uF) and coloration. Anyway, researching some older discussions on the distributed bass array topic, it looks like a more practical approach is what AudioKinesis uses in his acclaimed Swarm where I believe he utilizes a single kilowatt class AB amplifier to drive four passive subwoofers. 
https://www.parts-express.com/dayton-audio-sa1000-subwoofer-amplifier-rack-mountable--300-811
But even with this amplifier with a published 12K Ohms input impedance, I'd get a combined ~11K Ohms which probably works well with most if not all SS preamps but borderline for most tube preamps.
I'd like to hear if anyone is driving a distributed bass array system similar to the Swarm using a tube preamp as the signal source.
Thanks again.
millercarbon's avatar
millercarbon
12,531 posts
 
kalali, did I not already say don't overthink it? And then you go and compliment and start paying attention to the world's greatest offender in overthinking it? Now it appears you have overthought things to the point you've concluded that what works for everyone else cannot possibly work for you. At least that is what you think. Because you are thinking. Instead of doing.

The Dayton amps you have figured out cannot work are the exact same Dayton amps I am using. Exact. Same. Amps. 

Please go back and read my first post. Then stop thinking about impedance. Start thinking about table saws, sand papers, and veneers.
bdp24's avatar
bdp24
10,274 posts
 
If you can build the enclosures, Rythmik offers their subs in DIY kits. The kit includes the servo-feedback woofer and associated 600w plate amp, and polyfill enclosure stuffing. Even if you can't make an enclosure, Parts Express sells some really good sub flat packs, which are a snap to assemble.
kalali's avatar
kalali OP
1,977 posts
 
"...did I not already say don’t overthink it?"

Yes sir, you did. Guilty as charged. I appreciate your input based on your practical experience.  
almarg's avatar
almarg
9,670 posts
 
kalali, did I not already say don't overthink it? And then you go and compliment and start paying attention to the world's greatest offender in overthinking it? Now it appears you have overthought things to the point you've concluded that what works for everyone else cannot possibly work for you. At least that is what you think. Because you are thinking. Instead of doing....

... Please go back and read my first post. Then stop thinking about impedance. Start thinking about table saws, sand papers, and veneers.

Miller, my analysis establishes pretty conclusively that the OP's preamp should not be used to drive four powered subs having typical impedances, in addition to his power amp. That was something he was rightfully concerned about, and that he had specifically asked about.

Rather than telling him to "stop thinking about impedance," and throwing in a gratuitous insult (toward me) in the process, I suggest that it would be more constructive if you were to specifically address the question he and I were discussing, about driving all of those loads with his particular preamp.

Regards,
-- Al
 
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