Optimus Pro 7 / Pro SW-12 system

[jdmccall]

I have an Optimus Pro SW-12 "sub" that I bought new, on sale from RS for $100 in 1993, and have accumulated six Optimus Pro 7 speakers over the past few months, all on Ebay. A couple were even NOS, still in unopened boxes. I just recently acquired another SW-12, in excellent shape, also from an Ebay seller. I paid a little over $70 for it. Still looking for a clean, single Pro 7 for eventual center channel use. When I received the "new" Pro SW-12 and got both subs connected and operating, I immediately heard a clattering sound from my original 25-yr-old SW-12. Upon closer inspection, yup, the surround was shot. A week later and $17 poorer, I put the new surround on and all is well again. Ready for another 25 years! I probably won't be around, but that's beside the point...

...Which is: Should I continue powering the Pro 7's directly from my Marantz NR1602 AVR, and powering the two subs my old Onkyo M-282, which is fed from the AVR's sub out? This lets me adjust the x/o frequency from 250 Hz (where it's currently set) on down as far as I care to push the little 7's. But, I lose stereo separation below crossover. Or would it be best to use the SW-12's internal crossover, which I believe is fixed at 250 Hz? Of course, considering the sub's age the x/o point may not be as spec'd. Using the sub's x/o would effectively render the two subs and the front L & R Pro 7's as a full-range stereo pair. All other speakers would still have to be rolled off using the receiver's bass management. But this would maintain stereo separation in front L & R pair as far down as the mix and bass directionality allow.

Other than this question regarding bass management, I think everything is pretty much going as expected with this system. It may not be a giant killer in any sense, but I dig it. I'm a huge fan of the Minimus/Optimus 7/77 speakers and also of the SW-12 passive sub. Cheap and cheerful hi-fi! Well OK, the fi ain't really that hi, but it's pleasant and enjoyable in a non-critical system. And tweakable to the extreme, which makes it fun.

 

[swechsler]

Interesting question. I had to read it through a couple of times to make sure you were considering everything. I have one of these but haven't used it in several years. I believe, though, it was designed with the Minimus 7/Pro 7 in mind.

I think you'll have superior sound for music reproduction if you use the built-in crossovers, but you'll lose the LFE channel output (although theoretically this should be redirected to the L/R channels if you disable the subwoofer in your AVR's config). However, one concern may be level matching. One SW-12 was designed to be connected to two Pro-7s, which means its output should be (in theory) 3dB higher than the output of a single Pro-7, and if you use two of them (one per channel) the your bass will be 3dB higher than the mid/treble. Now if you only connect one channel of each sub it may compensate for that (in addition, if you connect both in parallel, you'll increase output by another 3dB since you're now running a 4 Ω load in the bass frequencies, so you probably want to avoid doing that if you use this configuration).

Regarding a center speaker, RS at one time sold a center that was designed to match the Pro-7, more or less. It might be the CS-2 (I couldn't find a picture online with the grill off). The CS-3 uses a similar tweeter but has woofers like those used in the Pro-LX5. Optimus centers sell for not much money on eBay.

 

[jdmccall]

Thanks for the suggestions! I do apologize for my rather convoluted description, but the set-up is rather convoluted. I have all Pro 7's connected directly to the receiver. Each Pro SW-12 has one input channel connected to one channel output of Onkyo amp which has both channels driven from sub out on avr, via Y-connector. Currently, crossover in avr is set at 250 Hz. Sounds pretty good. A little bass heavy, but otherwise good. But I have yet to run auto EQ with both subs functioning. That should help with frequency balance.

I will investigate an Optimus center speaker. I really had not considered that, thinking I wanted to do identical Pro 7's all around. But, I will check ebay and see what I can dredge up.

 

[swechsler]

If you decide to keep using the built-in crossover in the AVR with the external amp for the subs, I'd go much lower with the crossover frequency. The Pro-7s should be flat down to at least 120hz, so I'd start with that. I'd also try running with both voice coils (for each sub) in parallel, which your Onkyo will see as a 4Ω load, but it shouldn't have a problem with that. If you decide to stick with this configuration, you might even consider removing the SW-12s internal crossover from the circuit. You don't actually need to remove the crossover from the box, just wire the terminals from the woofers directly to the input terminals on the boxes, this way you can restore them in the future if you need to.

 

[jdmccall]

If you decide to keep using the built-in crossover in the AVR with the external amp for the subs, I'd go much lower with the crossover frequency. The Pro-7s should be flat down to at least 120hz, so I'd start with that. I'd also try running with both voice coils (for each sub) in parallel, which your Onkyo will see as a 4Ω load, but it shouldn't have a problem with that. If you decide to stick with this configuration, you might even consider removing the SW-12s internal crossover from the circuit. You don't actually need to remove the crossover from the box, just wire the terminals from the woofers directly to the input terminals on the boxes, this way you can restore them in the future if you need to.

More points to ponder...thanks! Especially the idea to connect drivers directly to input panel. Regarding x/o point, it seems to me to be a trade-off: lower could give better imaging, but higher more power handling. I usually tend to favor dynamics and "big-speaker sound" of using relatively high x/o point.

 

[jdmccall]

I'm still playing around with crossover settings. Currently 200Hz to front stereo pair and 100Hz to all four surround speakers. Only issue is bass is localized in front of room where subs are. May need to lower surround speaker x/o's some more. Bass level may still be a bit high, too. Been listening to mostly chill and down-tempo, so it seems appropriate, though. Scintillating stuff!!!

 

[swechsler]

Bass is generally considered to be non-directional below 100hz. That's probably a little low for your satellites, but it's why I recommended you set the XO as low as possible - you've now demonstrated to yourself the disadvantage of using a high crossover frequency.

 

[jdmccall]

Next stop: 120 Hz in front, 80 Hz in surrounds! Actually, the receiver's auto set-up routine puts x/o's at 110Hz in front, 60Hz in surrounds and 80Hz in back surrounds. I don't feel localized bass issue is due to high front x/o, but is due to surrounds (and back surrounds) being too high. So, I'll see...or rather, hear.