Summing up L & R line-level for dual subs

Al,

You are right, I did mistype.

BTW, your last paragraph clarified what you meant: 2 Y connectors, each going from one pre out into both subs and letting the subs do the summing. I had not picked up on that! Thanks once again!!

Horacio

Thanks for the inputs. I'll ask Lamm if the outputs are buffered or not. Good tip!

Karl, you wrote "If your subs have L/R inputs, you should connect to them independently and let each sub do the summing". Yes, my subs have L & R inputs, but how should I connect them independently? From preamp left output #2 have a Y connector to go to sub # 1 and to sub #2 connecting to left input in each one, and do the same on the right?

Csontos, the reason being Mr Geddes has put much more time than me into this and that's his prescribed way...so if I want to give the approach a fair shot...it follows I should follow the prescription. It is indeed an intriguing approach.

Thanks all for the input!

Al,

Thanks for the very thoughtful post. I'll do my best to answer:

1) input impedance of the line level inputs of the subs: Rythmik 12" with A370PEQ amps. Impedance is not listed. Input is through coax, though. Should this be a key data point I would ask the manufacturer - let me know.

2) input impedance of the main power amp: McIntosh MC275 mk IV. According to Stereophile measurements on the "RCA jacks was a high 86k ohms at low and middle frequencies, dropping slightly and inconsequentially to 62k ohms at 20kHz"

3) how long the interconnect cables would be, from the preamp outputs to each of the subs and to the main power amp: all of them are RCAs. From pre to amp: 4 feet of PUrist Audio Museaus - I don't know their impedance. From pre to subs: one coax is 10 feet, the other one is 17 feet of Neotech bulk OFC interconnect cable.

Thank you!

Al,

Thanks so much for such a thoughtful post, and taking the time to do the research and the math. Truly appreciated! I'll have to digest it.

I have posted a question to Lamm to check if the outputs are buffered. Assuming they aren't, then it seems I could try 2 Y-connectors in series so to have L&R output > summed-up to one cable > divided into two RCA prongs using one to each sub. At least I could try it.

Thanks also for the tip about Transition Audio. I'm overseas, though, so that would be a second step.

Gbart,

Thanks for the suggestion. I will look into those (especially if the Lamm outs are NOT buffered).

Cheers

indeed, Kal. However, let me point out your posts tend to be criptic and I oftentimes don't find them helpful, despite being right on (which, like in this case, I realize after someone else has gone through the trouble of explaining). This is why Al's contributions are so valuable to many here: super-knowledgeable, takes the time to look into the question, and takes the time to explain.