How does a High-Level connected sub (i.e. REL) improve midrange?

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I keep reading reports that people who have added subs with high-level / speaker level connections (such as REL) find significant improvement in midrange and upper bass performance. I don't doubt the reports, but I'm intuitively struggling with how this is possible. If none of the load is being taken away from the main speaker (via a high pass filter), its job shouldn't be getting any easier. And the sub shouldn't be contributing anything of its own much above 80-100hz depending on crossover point. So what's going on here? With line-level connections that include a high and low pass filter, I can see how this would work if done correctly. The high level connection has me mystified a little, though.

Question prompted because we're once again considering adding a sub, and the finalists are JL and REL, who go about their business in very different ways.
 
From my personal experience, the benefit is a result of relieving your main speakers from playing below a selected frequency and letting the subs take care of that. Essentially you are letting the sub handle the lower frequencies. You need a crossover for that. Your main amps now have more reserve to play the mid/high frequencies.
 
I keep reading reports that people who have added subs with high-level / speaker level connections (such as REL) find significant improvement in midrange and upper bass performance. I don't doubt the reports, but I'm intuitively struggling with how this is possible. If none of the load is being taken away from the main speaker (via a high pass filter), its job shouldn't be getting any easier. And the sub shouldn't be contributing anything of its own much above 80-100hz depending on crossover point. So what's going on here? With line-level connections that include a high and low pass filter, I can see how this would work if done correctly. The high level connection has me mystified a little, though.

Question prompted because we're once again considering adding a sub, and the finalists are JL and REL, who go about their business in very different ways.

I have a couple of REL R528SE subs in my stereo setup.

It takes a while to define the best positioning, xover and gain but once you do get it right the result is truly good IME.

Not only in terms of low frequency extension but also you get a sense of a much more realistic atmosphere, as if you can hear the air of the recording venue.

I agree that the midrange improves too. I'm not very technical but I do know that the REL low pass filter isn't a brick wall so that may help to explain.

But better still is to hear it for yourself in your own room if possible.

BTW should you decide to buy a REL I think you should buy the best you can afford and then seriously consider adding a second one when budget allows.
 
From my personal experience, the benefit is a result of relieving your main speakers from playing below a selected frequency and letting the subs take care of that. Essentially you are letting the sub handle the lower frequencies. You need a crossover for that. Your main amps now have more reserve to play the mid/high frequencies.

That's not the case whilst using the REL's high level connection.
 
The added low frequencies support definition of low and midrange output from the main speakers.


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Hmm, that's an interesting thought - that the additional LF energy supports improved definition from the mains. So it's a foundational thing where a robust low end sets up the midrange for better sound?

I keep coming back to the fact that without a low pass filter or crossover involved in REL's method, the main speakers are still working as hard as if the sub weren't present. So it has to be a perceived improvement, as opposed to a physical or mechanical improvement coming from a driver or amp that isn't working as hard as it used to.

As was mentioned by Music Fiend above, when you do have a low pass filter (say with a JL Audio or most other subs), then absolutely the main speakers and amp are working less hard, and should have more headroom for midrange definition.

I find the REL solution intriguing for a number of reasons, not the least of which is adding fewer cables and devices in the signal path for pure 2-channel use.
 
You don’t use RELs with a low pass filter, that’s why they are connected to the speaker terminals. Instead you control sub level and cut-off frequency. They are a support, not a replacement for the LS woofer. Probably a different thing with gaming and earthquaking subs.

And honestly, at least I would not buy hi-end speakers and cut off the woofers. Through a low pass filter you might control frequencies, but lose coherence.


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I totally understand your confusion. And when I try to reason it out - it doesn't make sense why the midrange gets better when nothing has changed in the speaker. Only the addition of a sub.

But. It absolutely does improve the mids. I guess my suggestion is to try it out and see if you hear the same things a lot of people hear before you buy the subs.
 
The added low frequencies support definition of low and midrange output from the main speakers.

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After doing some research, I believe that this is the correct answer.
 
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