Axiom Home Page Forums General Discussion Technical Questions Pre-amp Out to Sub: Receiver Adjustments

He's just use a pair of speaker wires from each of the output terminals on the receiver (Y-ing to split is OK, it's Y-ing to combine that's the issue). Run one set of high level outputs to the sub, set the sub's low-pass filter ("crossover") to 80 Hz, and then run the second set of wires to the speakers. Their natural roll off will blend in with the sub's filter.

There's not much one can do with a receiver that has no in built provisions for a sub-woofer.

He's saying high level in and out, not just in. I'm also assuming an actual cross-over, and not just a low-pass filter. That way the sub can control what signal gets passed on to the speakers, rather than the full frequency range.

A speaker cabinet, and driver does constitute a band-pass filter anyway. It's more a matter of getting a smooth match between the two (the electrical filter in the sub, and the physical filter in the speaker).

you better reread my post.

until i get a new prepro, i'm running separate preamp and power amp.
They're from the 1980s and don't have a sub out.
the simplest way to make connections in my case was using the high level inputs AND outputs (speakers connectors on the sub):
Power amp TO sub's high level inputs;
Sub's high level outputs TO main speakers.
when done, i adjust the sub level with the level control on the sub to match the main speakers' levels.
You also need to adjust the crossover freq. on the sub itself for a "best match".

speaker wire needs to be used for those connections.

Okie doke... I'm going to need some help to clarify in my mind, what's been discussed here, and add a few new queries while I'm at it!

1. JohnK... One thing I do NOT intend to do, if possible, is to lose any bass signal in either left or right channels from getting to the subwoofer. If i need to use high/speaker-level inputs for that, than so be it. But please confirm for me, if by doing so, the subwoofer will receive ALL the info it needs to perform at it's peak (and perhaps more than needed, in the higher frequencies), and that there will be NO loss in volume output, as it will still run off of it's own amp with no handicap from using high/speaker-level inputs... correct?

2. Also, please verify, by using high/speaker-level in the manner that has been suggested (speakers branch from receiver, subwoofer branches from receiver - speakers do NOT branch from subwoofer)... that the speakers run off of the receiver's amp, and the subwoofer runs off of its own amp, correct?

3. Additionally... my receiver has main left/right speaker outputs and 'remote' left/right speaker outputs, with a front panel 'remote' on/off button. I should be able to connect the subwoofer to these 'remote' speaker outputs, and avoid 'sharing/crossing' speaker and subwoofer speaker-wire wires in the same slots, correct? Would give me a nice 'off' mechanism too!

4. Everyone always talks about getting sheilded coaxial subwoofer cable. If I use speaker wire, there won't be any shielding. Is shielding, for some reason, suddenly a non-issue with speaker wire?

5. ClubNeon, earlier you responded to the what-if I connected my receiver's stereo-headphone-jack output to the subwoofer's 1/4" phone (stereo-headphone-jack, essentially, no?) input. You suggested that would be a worrisome strategy. But... isn't the subwoofer itself able to convert stereo signal to mono, internally? After all, isn't that what it does when you use separate high/speaker-level inputs on the subwoofer? And it would give me the chance to feel I didn't totally waste my money on that nice RCA cable (and y-adapter) i ordered (assuming I buy a 2nd 'phone-adapter' for the receiver end). Hmmm... i guess what you were suggesting is that it's converted to mono IMMEDIATELY upon entering the single RCA cable, rather than when it gets to the subwoofer... but can the current/short jump backwards into the receiver's phone jack - without a 2nd cable available to physically loop back, as in the case with the RCA Y-adapter attached to the 2 Pre-amp outputs on the receiver? Hmmm... do my questions even make any sense at this point? I'm so out of my element here, lol.

6. JB, your setup is the kind that I got a bad impression from, hearing tidbits discussed here and there online. In your setup, is there a point to having a main amp? I might be wrong, but if your subwoofer has its own internal amp, won't it ignore any power coming from your main amp? And since your speakers are attached to your subwoofer, won't they draw their power from the subwoofer (and not your main amp), hence draining some energy from the subwoofer that the subwoofer possibly could have used for itself? In all of that... the main amp would be useless, except for sending the audio signal itself. Again, I'm a naive noob, so what do I know! lol

Great discussion, very informative!

Quote: "4. Everyone always talks about getting sheilded coaxial subwoofer cable. If I use speaker wire, there won't be any shielding. Is shielding, for some reason, suddenly a non-issue with speaker wire?"

I've had sound systems since the mid 80s, and i've never had any interference of any kind by using ordinary 2 wire cable for all my speakers. it does not mean it never happens.

On number 4, it's probably not a problem because low level inputs have much lower voltage than high level (ie speaker level) inputs, and are therefore more susceptible to interference.

Quote: "6. JB, your setup is the kind that I got a bad impression from, hearing tidbits discussed here and there online. In your setup, is there a point to having a main amp? I might be wrong, but if your subwoofer has its own internal amp, won't it ignore any power coming from your main amp? And since your speakers are attached to your subwoofer, won't they draw their power from the subwoofer (and not your main amp), hence draining some energy from the subwoofer that the subwoofer possibly could have used for itself? In all of that... the main amp would be useless, except for sending the audio signal itself. Again, I'm a naive noob, so what do I know! lol"

i will try to make this as clear as i can.
speaker (high) level signals come out from the main amp and go to the sub high level inputs.
from there, the signal is divided in 2 parts by the sub's crossover; one becomes the Low Freq. signal that goes to the sub's internal amp, and the other one contains only signals above the sub's crossover point and that signal goes to the front speakers at the same level it had when going out of the main amp.

done this way, the main speakers receive the signals stripped of the frequencies below the crossover point,
and the sub receives only the low frequencies below the crossover point.

if the crossover is set to, let's say 100 Hz, then the sub will reproduce, with it's own amp, the frequencies below 100 Hz,
and the main speaker will receive all the frequencies above 100 Hz. from the main amp output to the speakers.
this is a simplified explanation.

Quote: "6. JB, your setup is the kind that I got a bad impression from, hearing tidbits discussed here and there online."

Please explain what you mean.

Okay GC; this discussion is still a bit tangled-up with terminology. Again, subs don't have internal crossovers; the speakers get a full-range signal even when they're connected through the sub. The low-pass filter in the sub rolls off the sub driver response above the selected frequency on the control(sometimes labeled as "crossover"), but has no effect on the mains. A very few subs have a separate high-pass filter, typically fixed at around 100Hz, on their speaker level outputs which affects the mains if they're connected in that way, but this has nothing to do with the sub's low-pass filter and its frequency control.

1. When connected to your 2235 with speaker wires, the sub gets all frequency content in both channels and the internal low-pass filter then rolls it off above 80Hz when that setting is selected.

2. Yes, the receiver power goes straight to the mains, regardless of whether the mains are connected through the sub. The sub amp can only power the sub driver; it has nothing to do with the mains.

3. Not familiar enough with the 2235 to discuss that "remote" provision, but again, use the speaker wire connection and don't worry about it.

4. Yes, shielding is essentially a non-issue with speaker wire. The current carried is far greater than that on line-level coaxial cables and isn't audibly affected by weak external interference.

Re 3., I was able to find a picture of the back of the 2335 and I see the second set of speaker terminals for "remote" speakers. So yes, as long as your manual says that you can use both sets of terminals simultaneously, you could connect the sub wires to the "remote" terminals instead of jamming them into the main terminals.