Best Subwoofer Connection for Music

Thanks Mike. Looks interesting. 

@oldrooney, if you’re interested, another good read. Fast bass, slow bass - myth vs. Fact see here! 😎

Connecting a JBL subwoofer see here pages three and four.

Mike

@oldrooney "I don’t know why anyone recommends using high level I/O for integrating subs in a music system, but I swear I have read/heard the advice more than once, and it always caused me to scratch my head. I couldn’t figure out why they would recommend the practice."

It's cheap for manufacturers to add and it allows you to bolt on a subwoofer to any system, thus extending the potential market for that subwoofer. It also does nothing to extend the dynamic range of the system or protect a small satellite speaker's woofer from LF over-excursion. 

@panzrwagn Thank you for educating me. Then I don’t know why anyone recommends using high level I/O for integrating subs in a music system, but I swear I have read/heard the advice more than once, and it always caused me to scratch my head. I couldn’t figure out why they would recommend the practice. I thought I must have missed something. And, No, I wasn’t recommending building a crossover at high level voltages, even I’m not that crazy. I thought there might be one in the sub circuitry that could be used. 
 

As an aside, in other contexts [like power transmission] ‘Low Voltage’ is about 2.3 kilovolts (at the power plant); ‘High Voltage’ ⚡️ is over 4 kilovolts (on the transmission line to the substation near your house). The size of of the capacitors on crossovers for a network that size would be truly prodigious!

@oldrooney Yeah, but that's not how it works. Opening up any subwoofer with high level inputs and primary speaker outputs and you'll see they are just passthroughs tapped to feed the subwoofer amp. Hi level inputs typically have a high impedance value tap across which the signal voltage is measured, then padded down to line level which feeds the subwoofer amp and it's LP crossover. The high impedance presents no meaningful load on the main amp, and the full range signal continues on to feed the primary speakers. 

Doing what you suggest would require some very large value and thus very expensive capacitors and coils just for a single fixed frequency and would likely impact overall sound quality of the primary speakers.

@panzrwagn and others, I think I’ve figured out why some people are recommending the high level connectors, provided that the sub has high-level out, as well. If the full range, high level, signal goes to the sub first, the sub applies a low pass filter to the signal for the purpose of selecting the frequencies for its low frequency driver; but it sends the remaining frequencies (low cut = high pass) out the high level speaker out terminals to the main speakers. So the effect is the same, separating low frequencies from the main speaker and sending them to the sub; it’s just that the means are different. I’m sure that filtering is best done at the low level, but would suffice for testing out the theory. 

@m-db Thanks. I feel that I will to develop some skills along the way because despite several attempts at integrating subs, I haven’t been able to get lucky yet. And you’re right about the room ruling. I’ve got two completely different systems set up in the same room, and guess what? They sound virtually identical. The average living room is indeed a limiting factor that even acoustical treatments can only mitigate, but not remove entirely. The Sound Doctor makes that point before all others, I believe. Thanks for the response. 

@oldrooney   "I haven’t gotten that far yet on this go-round. I’ve placed the sub in the listening position and gone around the room to find the spot the bass was strongest.'' 

Determining your rooms actual standing wave bass modes using a sub placed at the listening position playing low frequency cadences. THEN locating the loudest bass modes is actually the very first step in setting up a -3dB subwoofer system.

There the subwoofer/s use the rooms modes requiring the least amount of their power and processing needed for their best performance, integration and the musicality designed during post production.

The room rules, not the system. Good luck with it.

@m-db I haven’t gotten that far yet on this go-round. In the past, I’ve placed the sub in the listening position and gone around the room to find the spot the bass was strongest. The Dayton-Amped 15” sub for the McIntosh system is headed for the #1 ‘sweet spot’ in the right front corner; the 10” RCA sub with the Rogue system will go to sweet spot #2 in the left front corner initially. The Sound Doctor (see ditusa’s link on first post) suggests that placing a second sub in the back of the room may be desirable. I’m just trying to get one per system up and running (correctly) before experimenting with a second sub. And I would likely try that in the upstairs listening space first. Good question, though. 
 

@panzrwagn The experts agree with you, see ditusa’s link in first response post above. I have a capable active crossover that I’m itching to use, a vintage Pioneer D23, so I have what I need to implement your (and the expert’s) recommendation. I’m going to try it without the crossover, and then with it. I’ll let you know how it works out. 
 

All: To anyone stumbling on this thread, Panzrwagn’s pronouncement is, indeed, the best way to connect a sub: using low-level connections, optimally downstream of the best active crossover attainable; although there are many options short of that that are all an improvement. As I’ve noted several times above, ditusa, in his first response to my post links to a rather complete treatise on the topic by the Sound Doctor (his name is given in the link) who has worked in field for over 15 years [probably 20 years now] and spent enough time with JL Audio to develop the finest crossover for the purpose in the industry (according to him). I found his writing style quite approachable. He recognizes that integrating a sun is NOT an easy task, but he explains WHY it isn’t easy and what can be done about it. If you’re interested in the topic of this thread, I recommend highly reading it entirely. 

There really is only one correct way to add a subwoofer: insert a high pass/low pass electronic crossover between your preamp output and the inputs to the main speaker amp(s) and the subwoofer amp(s). Anything else is just an attempt to get a subwoofer operational without the benefits of true bi-amping.

Where are your subwoofer cabinets positioned within your room and how were those locations determined?

@oldrooney, you're welcome!😎

Mike

@erik_squires Agreed. It is not the best way to connect a subwoofer and I’m sorry I brought it up. 

OP: An external crossover does have level matching. The problem is that in the tape loop it won’t track your preamp’s volume control.

So... you end up with another volume control, and at that point you might as well interrupt the preamp <--> amp connection or use the crossover to replace you pre, which some miniDSP models can do.

@czarivey 10-4. Up to this point I have done the same. It’s that I keep hearing others say that hi-level speaker connections are better for listening to music. Which makes me wonder if I’m missing something. 

@czarivey I’m sorry, I completely misread your post to mean that you preferred to use the tape loop for your sub. 
 

@paradisecom When I’ve used speaker level inputs on the subs, I’ve connected them as you describe. However, I found the dual coil sub arrangement with included satellite speakers, had wonderful integration, I just didn’t like the sound itself of the compressed satellites or the 8” floor-oriented sub. 
 

@erik_squires It is possible to use the tape loop for a sub, but as you state, you need a way to attenuate the volume; some crossovers have that feature built in, see Mike’s reference above in the first response to my post. 

I meant secondary pre-out... That dictates preamp to have 2 outputs and that's usually the case with most of the balanced preamps where one output balanced and the other isn't and one of them can be used to feed sub(s). 

@czarivey I’m sorry, I completely misread your post to mean that you preferred to use the tape loop for your sub. 
 

@paradisecom When I’ve used speaker level inputs on the subs, I’ve connected them as you describe. However, I found the dual coil sub arrangement with included satellite speakers, had wonderful integration, I just didn’t like the sound itself of the compressed satellites or the 8” floor-oriented sub. 
 

@erik_squires It is possible to use the tape loop for a sub, but as you state, you need a way to attenuate the volume; some crossovers have that feature built in, see Mike’s reference above in the first response to my post. 

Oh, BTW, you can't use tape in/tape out for the sub because it is before the volume control. You can put an EQ in there, but not a high pass filter.

It sounds like you could connect both subwoofers using the speaker-level inputs.  I prefer to not use the speaker-level outputs on the subs to feed the mains running through the subwoofer amp, relying on the subs internal crossover.  I prefer to just connect the mains and the subwoofers speaker-level inputs to the main amplifier speaker terminals.  Then, I adjust the phase, crossover and volume controls on the sub to blend with my main speakers.

@ditusa Thank you, Mike. That was a good read. Thank you, too, for introducing me to a very approachable audiophile expert.
I happen to have an active crossover [Pioneer D23] I can put to good use implementing some of Barry’s connection/integration recommendations.

@czarivey Both of my preamps have separate “processor loops” that I use for integrating EQ. The thing about the tape loops is that the output is fixed at full volume, but that can be an advantage if you’re willing to adjust the sub’s volume independently, I suppose. Also, I’m not sure that, depending on the amp, the tape loops are always identical to line in/out voltage & impedance, but I could be mistaken.

Edit: @czarivey Perhaps I should ask why you prefer to use tape loop. Others frown on it, and I’m curious, not knowledgeable (although I frequently pretend to be so). 

I've always preferred line-in connections to subwoofer via tape-output.

ADDING A SUB see here!

Mike