Subwoofer connection with a twist

Loudspeakers
#1

I’ve experimenting with a subwoofer connected to RCA L/R from my BHK Pre and the result has been very satisfactory. I do have two identical subs so in theory I could go full stereo. Here’s the but… the second sub is hooked up to my HT (same room but all in wall/on ceiling/in ceiling) with a dedicated AVR.

Could I hook up the AVR to the left/LF RCA in and use the right RCA from the BHK? The two systems are never on at the same time

All the settings are already identical between the two so that’s a non issue.

#2

Yes but to be sure contact the maker of each if not the same.

I run RCA (or single-ended) from AVR to ‘LFE IN’ and BHK 250 through a Jensen transformer to go from high-level to single-ended. Both connected all the time. Works great. It should also hurt nothing to have both on at the same time but playing two sources at the same time is not advised.

I often have my AVR and display on with Youtube playing on old Apple TV 3 with optical out to my dac to pre to amp. There is no audio processing through the AVR only through the 2 channel system.

Hope this helps

#3

For most subwoofers this does work, I use this same method in my own system. But I would recommend checking with your subwoofer manufactures as some subs will only accept a single input at a time.

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#4

Thanks everyone!

I checked with PSA and they see no reason why this wouldn’t work. Time move some very heavy subs!!!

#5

The subwoofers are moved around and it’s all hooked up. RCA from BHK Pre to standard input on each subwoofer. RCA from HTR to the LFE input on each subwoofer. Luckily, the settings are the same or this wouldn’t have worked. BUT… it sounds fantastic! The stereo subwoofers made a huge impact (no pun intended).

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#6

Goof to hear. Nice when things work out.

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#7

Is it considered “subwoofer connection with a twist” if I were to connect the subwoofers’ (two of them) drivers straight to my amplifier’s left and right terminals (of course with a low pass filter that handles the amperage), given that my amplifier handles up to around ~470W and the subwoofers are, let’s say, light 8" low distortion ones with passive radiators, that take up a light 380W in total, and my main speakers have a power handling of only 80W.
Wouldn’t powering a light pair of subs this way passively give me a much better integration of the bass? Of course now I’m missing phase control, etc, but no matter.

…is there a problem with a suitable low pass filter? At those wattages?

#8

@Arenith Are they active subwoofers or passive subwoofers? If active, then that is indeed the preferred way to hook them up. If passive, then, no that won’t work

#9

I didn’t really mean subs with any inner amplification, just drivers in boxes with terminals. So definitely wasn’t referring to high-level inputs.

I meant driving the subs with a powerful enough stereo amplifier with the same cabling for both the main speakers and subs. With a low-pass filter. The thing is I don’t know if there’s low-pass filters for such high wattage applications.

#10

That would mean that you have them connected in parallel which means you will drop the impedance. For example, two 8 ohm speakers in parallel would mean that the amp sees 4 ohm. Two 4 ohm will be 2 ohm, etc. You’re running a serious risk to damage the amp if the impedance is below what the amp is capable to handle.

Second issue will be that the efficiency of the speakers and the passive subwoofers will need to be exactly matched (best would be if the efficiency is matched in YOUR room, as you will have boundary gains to deal with). Otherwise, the level of one may not match the other.

Basically, what you are asking for is a recipe for disaster. You skip the whole idea of a passive subwoofer and use an active (powered) subwoofer. OR, get a dedicated subwoofer amp that has gain, low pass filter (or high/low pass to with RCA/XLR in’s/out’s to be used with your existing power amp), some kind of eq (to smooth out room gains).

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#11

I’m bad at math so help is appreciated - my speakers are nominally 8 ohms, efficient with power handling 80W, the amp handles down to (under) an ohm with max output 500W (peak current 80A), do I have room for two quite efficient 4ohm subwoofers in stereo config (left & right separately from terminals)? I need the subwoofers outputting only the bandgap below about 25Hz
I guess I do have (room) for them. But confirm, as I said my math is bad, poor even.

#12

As for a “recipe for disaster”, for my amp, no. I’m sure, even with quick calculation by head. It has too good an output protection circuit (and fuse) for it not to handle this, I’m more asking… How well?

#13

You still have the issue of efficiency match between the speakers and the subwoofer… it’s just too difficult to integrate passive subwoofers without a dedicated outboard amp/crossover.

May not be disastrous for your amp, but very likely for the sound

#14

“without a dedicated outboard amp/crossover.”
So an outboard crossover would do? I absolutely want to drive the subwoofers with my main amplifier and use the same cable, etc, just to remain absolutely truthful to the analogue transmission received by the main speakers. I don’t want Class D in the way, I’m a class A snob. Make a difference in subs? Don’t care.

What about the impedance mismatch? Will I mitigate this with passive components?

#15

No, a crossover won’t help as that would need to go ahead of the amplifier (or have a built in amplifier for the subwoofer).

You will either need an active subwoofer and then use your speakers full range, or an active subwoofer with a high-pass for the speakers. Or passive subwoofer with an external crossover and a second amp.

You’re not going to be able to drive the subwoofer from you existing amp that’s also driving the speakers.