REL six pack questions

Hoping those who have experience with REL six packs can answer a few questions for me. I am building a six pack and will have it operational in the next week. I am having a local dealer set them up, but I bought them all used and would like to ask the forum a few things. Some of these are just curiosity, but others I really need to know.


1. I watched John Hunter's six-pack setup video and cannot  understand why each sub is set up progressively without the other subs stacked above it. One would think the physical presence of the other subs above would affect the sound of the one below it. Why not have all three subs stacked up, and plug one in at a time to adjust it?


2. Speaker designers spend painstaking years getting a speaker to be very close to flat in frequency response. With a six-pack we are deliberately dialing the upper sub crossover points to overlap with the mains (my mains are flattish down to 28hz). How does this not create a muddy mess?


3.  My understanding is that part of the real magic of six packs (spatial realism, textures) happens because there is hidden low frequency content in fundamental instrument/vocal performances that becomes apparent with a six-pack. But if one has giant mains like Magico Q7s, for example, they produce deep frequencies. Why would a six-pack help mains that also produce very low bass? 


4. Separate from the above magic, I have also know that low frequency musical signals create harmonics all the way up the spectrum. But the subs don't reproduce anything above the midbass region due to the second order crossover so how would the subs reproduce those higher harmonics? Or maybe the point is that the six-pack reproduces low bass one didn't hear before, so now oe hears new higher harmonics that were not there before?

I have another question but I am going to post it separately because it is a special topic. Thanks for any thoughts on above. I am fascinated and excited about the six-pack.



I can’t speak to your technical questions, but I can give you my low-tech experience with my own Rel stacks (3 S 501’s on each side).  I set up the stacks and then tuned each by ear, starting with the floor and moving up to the top, one at a time, turning off the other 5, but adjusting the pairs together before moving to the next level.  I run them off the High Level outputs.

As to your other questions, I can tell you what I hear, but do not have the expertise in acoustics to explain why or how it works.  First the bass is very tight, controlled, and fast, with no boomy, bloated low frequency thumping at all.  There is a better sense of space around instruments and vocals, and a far better sense of weight and presence (but not unnaturally  up front) with each note.  The sense of space is three dimensional, which I think of as the polar opposite of, for example, the Phil Spector Wall of Sound effect.  The sound stage is improved in all aspects.  I do not notice any nodes or suck-outs, but I imagine that would vary across listening rooms.  The overall effect brings the sound much closer to an actual live music than any other component upgrade I have done.

Your observations are very astute.

  1. I agree with you, I would have all units in place after the bottom one is properly located, and make the initial adjustments individually.
  2. All over lapping frequencies reproduced by different drivers would have to be in perfect phase alignment in order not to be a muddy mess, though it might be possible that due to the latency of the passive radiator in the REL subs, this issue might be masked to some extent. You will notice in the video that A) they are pairing their six-pack with a bookshelf speaker that probably doesn’t have any meaningful bass below 60 Hz. And B) they don’t play any music through the system at any point in the demonstration.
  3. There is no such thing as hidden bass in a recording, it’s whether or not a system can reproduce the bass that’s in the recording, not all systems can, which is why subs exist. If your mains can reproduce low bass with authority, there is very little reason to add subs, unless you are looking for more impact, in which case there is very little reason to have mains that can reproduce low bass, in my opinion.
  4. They do not. The harmonics are created by the instruments and are captured on tape or digitally in the recording and then reproduced by the driver that reproduces that particular frequency of the harmonic during play back. So even if your system is unable to reproduce the low bass fundamental of an instrument the harmonics of that instrument are still captured in the recording and your system is currently reproducing them during play back.

Thanks audiorusty! Yeah you make a great point about them using small monitors for their demo. But in many installations they use giant main speakers that have response down to the bottom. So it's still a mystery to me with those kinds of speakers, or even with mine that go to 28 Hertz, how adding more response in let's say the 30 to 60 Hertz range doesn't just turn into a frequency imbalance. Unless maybe it's related to our ears natural insensitivity to low frequencies... Anechoically a speaker could be flat in the low frequency areas, but perceptually they probably have a lot of roll-off to our ears. Maybe that allows these subs to add energy without creating what seems to be a great imbalance. No idea if this is right or not but I have not heard anyone explain it In a way that makes sense to me! 


Thanks again for the thoughtful response!