[totoro]

So I have the following system:

sb touch -> classdaudio amp -> speakers (right now Audio Physik Tempo 4, placed an order with Duke for a pair of floorstanding Planetarium 15s, should be here in April some time I think-- pretty excited about this )
               -> Dspeaker 8033s -> rythmik F12se + rel storm

right now, I have a pair of rca  y cable splitting into two sets of cables leaving the sb touch, and another pair after the dspeaker thingy . If I wanted to add a couple more subs, this would probably not work as a strategy. What's a good way of splitting the signal that scales up ok as one adds subs?

[James Romeyn]

It sounds like:
Stereo SB Touch, variable level pre outs L/R: Y adapter parallel feeds digital power amp and DSpeaker...DSpeaker dual sub pre outs feed Rhythmic and REL subs.  Is this correct? 

The following are critical:

Post respective input impedance: Main speaker amp, Rhythmic sub, REL sub 
Post source impedance for each DSpeaker output (is each output independent or are any parallel with each other? 

The result of source/load mismatch is reduced punch, dynamics, softer bass, etc, the exact opposite of your sub goals, especially with Duke's super dynamic speakers.  If my scenario above is correct, a source/load mismatch audibly reduces main speaker performance, and subs. 

Mismatch occurs if/when source drives multiple parallel loads, the lower the load impedance the worse the mismatch.  There is easy/low cost solution though.

Get four subs and you're in business, as long as they are not matched High-Q, in which case if they are there is easy solution for that too.       

[TRADERXFAN]

So I have the following system:

sb touch -> classdaudio amp -> speakers (right now Audio Physik Tempo 4, placed an order with Duke for a pair of floorstanding Planetarium 15s, should be here in April some time I think-- pretty excited about this )
               -> Dspeaker 8033s -> rythmik F12se + rel storm

right now, I have a pair of rca  y cable splitting into two sets of cables leaving the sb touch, and another pair after the dspeaker thingy . If I wanted to add a couple more subs, this would probably not work as a strategy. What's a good way of splitting the signal that scales up ok as one adds subs?

What you are looking for is a buffer, if not a full pre-amp stage. lookup the Dodd battery buffer for example.

[James Romeyn]

What you are looking for is a buffer, if not a full pre-amp stage. lookup the Dodd battery buffer for example.

Yes.  I'd predict mismatch, SB Touch driving a digital power amp input and DSpeaker input.  Plus Y adapters vary in quality/degradation.  A quality buffer should fix that, supplying the required current to properly drive both.

SB Touch L/R output > Buffer > main amp + DSpeaker 

DSpeaker may have similar current problem driving two subs, though less certain. 

Posting impedance for all pertinent outputs/inputs should answer that. 

[totoro]

I think it's fine right now, but might not be if I add a coup,e more subs. I got rid of my old classe preamp a while ago, and don't miss it. I'm hoping to find a reasonably priced buffer/splitter, but the only ones I've ever seen are for electric guitars. I'll look at the Dodd. Any other specific suggestions?

[James Romeyn]

I think it's fine right now, but might not be if I add a coup,e more subs. I got rid of my old classe preamp a while ago, and don't miss it. I'm hoping to find a reasonably priced buffer/splitter, but the only ones I've ever seen are for electric guitars. I'll look at the Dodd. Any other specific suggestions?

This is simple.  Without the impedance specs, the existence of any potential mismatch is unknown and unknowable, period.    A good analogy is speculating about an amp/speaker pairing without knowing the amplifier's current capacity (output impedance) nor the speaker's minimum load impedance.  It might be a fun way to waste time, but that's all it remains, forever. 

I got the SB Touch output impedance.  The amp company and DSpeaker seem to hide their respective input impedance specs online.  Check owner's manuals.   

[totoro]

I'd have thought this would be a common problem and there would've easily available buffer/splitters, but I couldn't find any, so I jury rigged it. There has been no noticeable effect on the sound.

[James Romeyn]

...There has been no noticeable effect on the sound.

If a mismatch exists, how would you "notice" it without the solution on hand to compare directly?  IOW, you can't hear a mismatch till you have the correct match to compare.  Duke's speakers are amongst the most lively and dynamic extant.  This performance suffers in the mismatch we discuss.   

The story of the mismatch or proper match is told by the impedance specs.  IIRC the total load impedance should ideally be in the range of 10x the source impedance. 

[totoro]

Right, that's why I want to get a splitter/ buffer now. I have no interest in arguing about this. I simply want to get a buffered/amplified splitter, and was hoping for some advice getting one.

I'm not trying to justify the y cable hack. It was a hack. The guy at the amp company told me that as long as the dspeaker thing and the squeezebox weren't absolutely pathological, it should be fine. I never did like it as a solution, though, and if I add a couple more subs their impedances will have to get factored in, so it will break down.

Do you have any advice  as to where to get a splitter or what to get? There are tons of really cheap ones aimed at the home theater market, but I have no idea if any of them even work properly.

[James Romeyn]

Sorry I missed the obvious solution:
 
SB Touch > power amp, speaker output > "bridging circuit" comprising 1/4W resistors (series 9k Ohm, parallel 1k Ohm on load side) > DSpeaker > 1st sub, pre out > 2nd sub pre out > etc.

Wire from main power amp speaker outputs to DSpeaker input: Canare Star Quad or 20AWG twisted pair hookup wire.  Install bridging circuit right in front of DSpeaker inputs or wire resistors into the DSpeaker input jacks (if the latter, note that inputs change from line level to speaker level).   

Jack Elliano of tube transformer fame recommended that bridging circuit, which I used to good effect.  It worked better than the cheap transformer I also auditioned.  If you solder cost is only price of the resistors.  Use Dale metal foil or your preferred brand.

Use the sub setup instructions at my web site and let me know results.       

[JohnR]

Right, that's why I want to get a splitter/ buffer now. I have no interest in arguing about this. I simply want to get a buffered/amplified splitter, and was hoping for some advice getting one.

If you can find out the specs of your subs (current and intended), you can work out the combined impedance and as long as that is greater than the recommended load for the DSPeaker, you should be fine. For example, say you have four subs with 10k input impedance. All in parallel, that means 2.5k impedance. Will the DSPeaker drive a 2.5k load fine? If so, you can just do that -- at least until you find some concrete reason not to. If not, then you will probably want to proceed along a different path. In that case, you could get a miniDSP to drive the subs for ~$150, that way you can experiment with different amounts of delay and high/low pass filters to the subs, as well as use the DSPeaker for the overall/automatic correction.