Making a decision on subwoofer connectivity

Loudspeakers
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Hi

I’m relatively inexperienced in HiFi and audio equipment. And I’m sorry if this is a beaten horse around here. I just got my first active subwoofer to complement my cheap 3.0 LCR setup and I’m experiencing a split brain decision about how to connect it.

I initially used an RCA cable to try setting LCR speakers to small and tinkering around with crossover to the sub, this seemed to be the general idea of doing things. After playing around with it, I didn’t like it much… Sounded kind of flat and thin in a way I can’t put my finger on exactly. Tried different speakers, maybe they’re all bad… I don’t know.

Then I saw the high level ins and tried those from one of the LR speakers, before even doing any research on it. I really liked that in comparison… I like the simplicity of it as well. And easy to add another subwoofer whenever, and run them in stereo LR respectively, complementing my LR towers. Making DSP settings very simple as the AVR doesn’t even have to know they’re there. Like the LR towers simply grew some bigger testicles…

But then I ask around and everyone seem to tell me I’m wrong. I find threads like this for instance:

Some main arguments against high level seems to be:

  1. Subs play bass under 80-120Hz much better than most loudspeakers speakers do.
  2. LCR mids and highs will play better because of more available power.
  3. Playing bass from mains as well as subs will “muddle” the sound stage no matter what.

So… I considered this (I mean, it has some logic to it, at least on the surface) and tried it as best I could with my only current subwoofer, but I just cannot make it sound as good as going full range and using the sub as an extension. I have no measuring equipment, just my ears and favorite movies/tracks.

Closest experience I got to high level was using RCA from LFE out but turning on LFE Plus (Pioneer AVR) which duplicates LCR as well as sending LFE, having all speakers set to large. But this won’t let me easily add a sub number 2 down the line while having respective LR output.

A local HiFi chain suggested it sounded worse because I have only 1 sub, and going above 80Hz would make it distinct and off to the side where I have it located. So I figured, okay maybe I can get 2. But the only way I can see to split LR into respective subs, is to have an AVR with 2x preout/LFE+preout and program them to stereo, but I have only 1 LFE out on my current receiver/AVR… And kinda want to make the most out of it, keeping things simple.

I keep leaning towards the simplicity of high level (except for a few more wires)… I thought it sounded good and easy to adjust. But people argue all kinds of distortion if I let LR play full range, as if they suddenly loose power, and other things that doesn’t make sense to me. How will they have more distortion than if not having any subs at all? I had the setup 10 years before adding a sub. And I view the sub as simply an extension of it.

Is the criticism perhaps because some subwoofers don’t handle high level input very well? I don’t really get it… Thanks for taking the time to read, for any thoughts and input you may have, and for letting me share my dilemma with you all.

Kind regards,
Jonny

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First suggestion is to not set your L&R speakers to small….

Try that with different sub connections and let is know what you think.

Cheers.

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My view is you are on the right track, try different set ups and go with the one that sounds best to you. If it sounds good it is good.

A few other thoughts:
Recognize the LFE output on your processor may only be active on movie settings and off for music. Does your processor have a music+sub setting? That will activate the LFE.
It is likely that the crossovers in your speakers and sub will sound better than the crossover in your processor. I agree with the suggestion above, set all your speakers to large.
You can get an RCA splitter to connect more than one sub to the single LFE output.
FWIW, in my system I have 4 subs connected via speaker wire with high-pass filters for music and for movies I add two more subs connected via XLR LFE

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Thanks for the suggestions.

As I continued my research, the only real problem I can find with running speakers as large, is potentially overdriving them, whereas sub may handle higher volume levels. But this was hard to find examples of, even on purpose, and I don’t view it as a problem at all. I’m a rather gentle user and won’t reach these kinds of levels. If I do, I’ll happily cross that bridge when I get to it.

I came across an interview with the VP of global technology at THX ltd. He suggested setting small with crossover to offload lows to subs for home users, but with an important sidenote that the recommendation is simply because most home setup speakers (home theatre in a box) won’t be able to effectively reproduce full range. So it’s a compromise rather than the ideal, as he underlined that cinema speakers can do this and they don’t make this compromise. Dolby content is ultimately mixed with full-range channel capability in mind.

Another thing, this I’m highly unsure of, but it keeps nagging on me. I’m hard pressed to think that offloading 3+ channels of low frequencies to a single sub driver at once can’t be optimal for the sound image compare to having individual drivers playing respective intended channel frequencies, and potentially by extension individual subs attached to them. But I’m just theorizing and need to test more.

I also found this:

“Its purpose is to supplement the overall bass content of the program or to ease the burden on the other channels. The LFE channel was originally devised for 70 mm movie productions to deliver a separate bass signal to one or more additional subwoofers placed behind the movie screen”

So having the .1 LFE going to one or more dedicated subs definitely seems like a good idea. Even if I could potentially mix it into LR by setting SW to off in the AVR, it’s a frequency best served sub.

My current opinion is subject to change, but it’s is that setting speakers to small and offloading all lows to one or more subs is a compromise done when not having speakers able to do full range in the first place. One of the biggest counter arguments is that LR will be able to play mids and highs better when lows are offloaded, but I view this as a power delivery problem or a speaker choice problem and something to be fixed individually, not one to make a compromise of.

Maybe I’m wrong, but it’s where I am at the moment. Gonna think a bit more about what makes sense to my intended usage. Maybe I’ll use 1 sub for L and R and a separate just for the LFE… not sure yet. I guess optimally I’d have 3. Rabbit hole danger…

Thanks for taking an interest.

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In principle using the LFE output to drive one or more subs should be superior. You set the crossover frequency to suit your speakers’ capabilities, your amplifier then cuts off frequencies below that from the speaker outputs and directs them to the LFE output and the sub(s). It should be equivalent to adding another driver (the sub) to your speakers and extending its crossover capabilities. The speakers no longer try to generate low bass for which they are not suited.

In reality it’s not that simple. It implies that you can set the LFE crossover point exactly. I have never had equipment which allows this. It has either been fixed, a choice of two depending on whether you select small or large speakers, or a limited range in 10Hz increments. For my desktop system the highest point was too low, and for my main system, with very large speakers, the lowest point was too high. Using the LFE output made it difficult (impossible for the desktop system) to get a satisfactory even frequency response.

When I use a high level connection I can, albeit with much fiddling and measuring of SPL, get a pretty even result. It is complicated if you have a Class D, or bridged AB, amp because you then have to find a suitable ground point for the ground return from the sub. Keeping the LFE output connected but turning the low level on the sub to zero is one way of doing this.

The conventional wisdom is that low bass is not directional, so the positioning of a single sub is not critical for stereo image. I have found this to be a truth with qualification. On my desktop system the sub is under the desk, but on the main system the only place for it was in a corner. There I found that at low volumes the bass did seem to come noticeably from the sub, but this effect vanished as volume was increased.

Once you start using subs purists will insist that you should correct for room modes. They are right, but it is a nightmare process even if you have the electronics to support it!

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Two subs both high level.

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This can be very dependent on what AVR/Processor you are using. What can it do with music vs movies. What xover points can it do. Can it do full range L&R for music or not? Depending on the unit the answers are different.

Best
Two high level subs for L&R set then to large.
If you can fit, connect 3rd sub to LFE for movies.
If your process can support two modes for music and movies this will be really nice.

I do know some AVRs if you use LFE it will NOT let you put in Large for Speakers. this really hurts the use of high level subs. hence why I said 3rd sub for movies.

Trying to mix a movie and music system can be done, but it comes at a much higher cost to do right. But for music as priority high level subs best. Movies many believe 80hz cut off is plenty if you have the right subs on the LFE. Trying to combine those two mutually exlusive goals gets hard to do right. And them of course sometimes speaker placement for music is not the same for movies.

I ended up with the JL CR-1 external cross over. it can set the cross over for music at any setting, and has a bypass for Home theater mode. not as good as 3 subs, but I did not have room for 3. I have one bigh one. Lets the AVR do the HT work, and just does xover at 33hz from my Sopra 2 with a nice slope. I add room correction with Roon and it works great. Again not a cheap solution at all and requires mulitple boxes and cable and and and… probably not what you are looking for.

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I got room for 3, more as well, but WAF probably limits it at 2-3…

Is this only suitable if the subs have high pass filters forward to the speakers? Or is it okay to add them anyway and adjust their low pass filters to where the L&R naturally rolls off. By e.g playing a frequency sweep and just doing it by ear, trying out different sources. I don’t have any measuring gear. Unless there’s any respectable smartphone apps available for this.

I mean, I went cowboy yesterday and went all large and even LFE + main, and still watched a movie… So I guess I’m not too picky…

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Yes that process seems fine. if you are good with setting mains = LFE + Main and your speakers can handle,that works too for movies.

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I think here is your answer, if you think it sounds better and it allows for more flexibility in the future why not continue to go this route? Who cares what ASR thinks? (Don’t get some of us started about ASR…)

Also to answer the third point/question you posed…. The high level input on your sub is prob in the range of 600 ohms, so it’s using a milliwatt of power, you should have no worries about distortion or ‘mudding’ the soundstage.

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