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Two pairs of spkrs in tandem

I need the help of the technically minded and capable folks on this great audiophile panel.
I am running B&W original 80 series 802's as my primary spkrs. rated at at 8 ohms..... tweaked..re-wired and all inards hard wired, soldered with cardas, great solid copper binding posts & Sand filled and tensionized side dampers to control box resonance in this (pre- matrix) design.

I have attempted to intigrate my other pair of favorite spkrs, 1996 Sound Dynamics 300ti's rated at 4 ohms, with their propietary titanium dome tweeters and run them in tandem with my 802's

In principal they have added a great deal in capturing subtle detail as well as in specificity and depth in the sound stage, most certainly in (over-all) dynamics and clarity

Basically "I love the sound" the 300 ti's seem to add that extra level of transparancy, reveal and crispness that the the B&W's didn't quite capture on their own...

THE SNAG however is a low level HUMmmmm!!!! coming from the Sound dynamic spkrs......

Mine is a complex set-up.... featuring A stereo pair of Janis SUB WOOFERS crossed over at 100 HZ and powered with their own dedicated W3 100 watt JANIS AMPS..

Also a pair of TOWNSHEND "super tweeters" connected to the B&W's

I built a (glued & screwed) MDF coupling that positions and holds the the 300 ti's upside down (forming a 6 foot high 9 driver (per side)"array" tweeter to tweeter assembley.. COOOL!!!

THE WHOLE THING IS A TERRIFIC REVALATION FOR ME!!!!! EXCEPT FOR THE ANNOYING HUMmmmmm!..

I've checked and re-checked the integrity of all connections to no avail...

If I re-move the 300ti's.. the hum is gone???...

IS it the B&W 8ohm Vs the ti's 4ohm mix??. Is that creating some kind of dichotomy causing the hum in my otherwise silent set_up ?...

I would love some help on this.... THANKS..
tweakyman
tweakyman OP
21 posts
 
Thanks Reylon.

I think you've nailed it....There is a low level hum (60hz)or (fan motor)? coming from the Moscode. I suppose I've gotten used to it having owned it since it was new. Kal Kr4 in the first response to my thread intimated that a passive spkr would not be the origination of such a hum, so he was right and I should have checked further upstream right away.

the hum never came through the B&W spkrs but I guess the sensitivity or filtering in the 300ti's which are more revealing in general is allowing and further amplifying this low level hum. Now I have to decide whether this tweak is worth it. I have fought hard to have a silent buzz and hum free set-up, so this annoys me...Thanks for your input...What amp did you acquire after selling your Moscode?
manoterror
216 posts
 
So I have a question on how you wired them. KR4 was asking why I would run them off the A + B terminals since they are off the same amp. I was thinking of this for 2 reasons. 1) Its simple, and I have 2 runs of cable. 2) I thought if I wired the speakers together, that it would drop the Ohms from 8 to 4.

So how did you accomplish this task? Is one way better than the other? As I see it, there are 3 methods:
1. Wire the speakers together (red to red, black to black) and connect a single cable to one of the speakers from the amp.
2. Use a bi-wire cable that isn't designed to have seperate treble and bass connections to both speakers, to one connection on the amp.
3. Use the A + B terminals with seperate runs of speaker cable to each speaker.

I would assume all of these might give the same result, but my main concern is the Ohm rating on the amp, as I'm running a Marantz SR7001 reciever and don't want to overtax it. :-)

Thoughts?
tweakyman OP
21 posts
 
Hi Manoterror. All I did in regards to the hook-up was run a short 4ft speaker wire from the original bottom speakers terminals into the add-on top pairs terminals. Only the primary lower pair of speakers are connected to the power amps terminals.I connected high quality banana plugs to each end of the short (tail)speaker wires. the primary lower pair of speakers are connected with spades but there are banana female openings in the tightening nuts. This allowed for a simple method of dual connection. It seems to work fine. I had originally run both pair separately from the amp but changed it to the method I described above. There was no real difference in the sound...
hifitime
715 posts
 
I'm guessing it may still overload your receiver.They don't make it clear enough.If you use speaker"C" for bi-wire,they may assume a typical 8 ohm speaker split(by removing jumpers)that would give 16 ohms for highs,and 16 ohms for lows,total still 8 ohms,the same as it would have if the jumpers were left in. Page 20 is where they talk about speaker"C" switch.Page 23 says the SR 7001 doesn't have the multi-room feature. On some that may give an extra amp.I can't find anywhere that it says 4 ohms total is ok.Manual link.>[http://us.marantz.com/DFU_SR7001_SR8001_final_eng.pdf]
tweakyman OP
21 posts
 
Manoterror, I forgot to adress your concern regarding over-taxing your amp.. Please take a look at Hifihvn's response to this thread. He talks about this type of parallel connection in a tandem speaker set-up resulting in an impedance drop. The amp I am using is rated at 300 watts per chnl into 8 Ohms and 500watts per chnl into 4 Ohms.
Other than the amp running a little warmer after a long listening session, everything seems OK..I'm not familiar with your amp...so I can't comment on how it would react to the additional load.
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