Subwoofer line level inputs [Archive] - Audio & Video Forums


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04-22-2009, 02:04 AM
I have an older Carver CM 1090 integrated amp running a pair of Cambridge Soundworks model six speakers which recently replaced my Infinity Monitor Jr's. I want to install a subwoofer and am curious about using the line inputs on the sub amplifier. The Carver has pre-amp outputs. Would I use these outputs, or just use the speaker wires? Any advantage to using the line level connections. Thanks.

04-22-2009, 04:08 AM
Using the line-level connections from your pre out would avoid increasing the number of speaker-wire connections and the speaker-wire length. However, using the speaker-level connections would allow the subwoofer's crossover to cut off the lows that are sent to the two-way speakers so they don't have to play those sounds. They might sound better in the midrange if they don't have to play the lows.

Mr Peabody
04-22-2009, 05:34 AM
The line level would also go through the crossover. I feel the line level is best, when using speaker inputs the sub has to step the signal down just to boost it again when it gets to the subs internal amp. Using line level keeps the signal in that range without transforming it.

Some subs have now incorporated a bypass switch to bypass the crossover for home theater use but with your 2 channel set up you'd want to use the crossover to filter the low frequencies out of your main speakers as 02AN was saying.

04-22-2009, 02:51 PM
Thanks for the info - wasn't aware that the sub crossover would limit the low frequencies to the mains. The Carver amp is pretty clean, will forcing the speaker signal through a middle-of-the-road sub crossover compromise the sound at all?

04-22-2009, 03:59 PM
There's a fair chance the speaker ins are wired direct to the speaker outs. Not all subs with speaker level connections implement a high pass at speaker level. Read your manual for clues.

If there is a HP in the sub it will very likely be just a series capacitor. You need a high voltage, non-polarized, non-eletrolytic, low-inductance, high microfarad capacitor. The right capacitors are large and expensive specialty items. I would expect manufacturers might try to cut corners. The wrong capacitors would definitely compromise sound quality.

04-22-2009, 04:07 PM
I guess my concern with running the line level through the crossover is that it then goes to the amp. It seems like a lot of line-level interconnect length. The speaker-level signal isn't as affected by interference as the line-level signal. My sub is over near a corner while the amp is near the center. Running a line-level signal over there and back and then using that to run my speakers never seemed like the best idea...I don't know for sure. You'd have a sort of bi-amped system at that point, so that seems like a good thing...but I think I'd rather not have my line-level signal running so far and through extra connections.

On the idea of stepping down the signal and boosting it again, I don't think it would do anything to the main speaker signal except send a crossed-over speaker-level signal. It might do something like that to the signal it's going to amplify internally, but the signal to the speakers will just be a crossed-over version of the same signal that came in.

Regarding the point Kevio made...I can at least confirm that the high pass crossover is functional on both line and speaker-level on the Velodyne DLS-R series...personal experience and I have the manual here.

And as for compromising sound quality...I don't think I could hear a degradation running the signal from my Adcom system through the crossover of my Velodyne sub.

Mr Peabody
04-22-2009, 04:36 PM
I made a mistake on my prior post. If you use the preamp outputs and Y off with one side going to the sub and the other side going back into the amp it will not limit the low frequency to the mains. Sorry about that.

If you did a config where the cable went into the sub and back out again into the amp, then it could.

As mentioned though subs are coming out with a lot more features to be more versatile with different set ups.

04-22-2009, 05:40 PM
I don't think the ccady's idea is to Y off the pre out. It's to run the integrated amp in its normal mode, plus use its pre out to run the sub.

Mr Peabody
04-22-2009, 06:02 PM
I was thinking made in 90 the preamp out would be one of those that had the jumper bar and may not have a choice but to Y. I have a Krell integrated from the 90's though that is as you describe, it had a pre out that would let you connect to it without disrupting power to mains. Good for biamping, and, subs.

04-23-2009, 12:56 AM
My amp has the bars in right now on the preamp outputs, so I guess If I add a sub it has to be done with the speaker wire. Thanks for all the info.

Mr Peabody
04-23-2009, 05:04 AM
No, just take the bars out get a set of RCA "Y" adaptors, plug the body of the "Y" into the preamp out, take one side of the "Y" adaptor back into the preamp input which will complete the circuit as the bar did, then the other side of the "Y" will connect to the cable going to the sub. This configuration will not limit the bass to the mains.

If the sub had a "high pass" output, you could do a similar hook up that would limit the bass. No "Y" would be needed. Take one set of cable to the sub input from the amp's preamp output. Run a second set of cables from sub's "high pass" output back into the amp's preamp input.

Most, probably even your manual, will recommend line level opposed to speaker level.

04-23-2009, 06:02 AM
Or even better...

Roadrunner6 posted this link ( in another thread (

For each channel, wire from your preamp out to the Y cable. Attach filter to one branch of the Y and then plug that into the power amp in. Wire the other branch of the Y to the line in of the sub. Set subwoofer crossover frequency to 85 Hz. Use test disc and SPL meter to set sub level. Enjoy!

04-23-2009, 09:51 AM
Although I'm no expert on the topic I will offer one last comment...It seems like the Y would significantly alter the load the preamp section sees while the speaker-level configuration would have no significant impact on the load the amp sees.

06-14-2009, 10:08 AM
Or even better...

Roadrunner6 posted this link ( in another thread (

For each channel, wire from your preamp out to the Y cable. Attach filter to one branch of the Y and then plug that into the power amp in. Wire the other branch of the Y to the line in of the sub. Set subwoofer crossover frequency to 85 Hz. Use test disc and SPL meter to set sub level. Enjoy!

Just before I make a doofus move here, if I have an older model integrated (Kenwood KA-6006), I would hook up the sub by getting a Y-connector; one end into the pre-outs, one into the amp-outs and the extension into the sub, right? Also, would I be able to bridge it into a receiver (Sherwood-Newcastle R-525) and use the receiver to handle the sub while the integrated handles the satelights ?

JoeE SP9
06-14-2009, 10:24 AM
One of the reasons for powered subs is to remove the low frequencies form the main speakers. Using Y connectors defeats this. Most decent subs include a high pass filter as part of the built in amp and low pass crossover assembly
Mr Peabody has detailed the proper way to connect a powered sub. ie: No Y connectors. It's really no different than the bi-amping I use. All frequencies below 85Hz never get to my ESL's or the amps that drive them. Speaker level connections with subs should be avoided if at all possible. The absence of passive crossovers is one of the main reasons ESL's sound seamless. Adding more passive parts to a box speaker that already has passive parts can't be a good thing.
Adding a bypass capacitor may be cheap and easy but it's detrimental to better sound.