Adventures With Subwoofers

I had the same speaker with an SVS 16 and thought it really helped steady the image and deepen the experience. Mayne my hearing is off and I didn't notice the nuances, or maybe room dependent as it mostly is.

Some of those Rel subs are not rated very low. I suppose it's a niche to make a sub that only goes down to 35hz, but for my purposes I'd say you want something more like the s812 with those speakers.

My issue with the C7's were with volume. They play loud but once you throw a little bass at them and the driver would bottom out.  Other than that I loved them. The clarity and energy with the lack of fatigue or aggression is great.

Proper sub integration takes a lot of time and effort. If you are a seasoned audio aficionado and have lived long without subs, it becomes easier to understand when subs add smearing and cause issues more than help. In my experience, this is not just about the crossover point and slope, but also equally as much to do with phase and time alignment, and maybe even more so.
 

The challenge with REL is that integration of their subs is typically limited to adjusting the crossover and positioning them, as phase is limited to 0 or 180 degrees, and most models do not have other features such as delay or parametric EQ. If you were to play with subs fromPerlisten (I’m an authorized Perlisten dealer, FYI), SVS (previous owner), or Martin Logan, their subs can be dialed in from your listening chair. When you can do this and adjust phase by degree, delay by millisecond, and crossover frequency by Hertz (as well as its slope), you’ll be amazed at how much easier it is to dial the sub into your system and get favorable results. Of course, sub build quality is very important. While SVS does wonders for the money, Perlisten and Martin Logan offer products that are a huge step above.

As others have mentioned, many of RELs offerings are meant to operate in the audible range and augment musical information into the subs (e.g. they don’t go that low). To experience the benefits of a wider, deeper soundstage and a more coherent presentation across the entire frequency spectrum (and not just in the lows), the sub should be dialed in using the features mentioned above, but in reality the sub also needs to go down to at least 20Hz, and preferably below. 

In my reference system, I employ two Perlisten D12s subs. A few of my clients have had me configure swarms of their larger subwoofers. In some cases they are crossed as low as 31-34Hz, and with proper integration in any system I’ve configured subs, you can barely hear them when the amplifier is off. But what they do to eliminate room modes, clean up the entire frequency spectrum, and add immediacy and texture to the sound can be accomplished by little else (BACCH-SP’s DSP innovations come to mind here). 

I used a miniDSP to my sub only (Rythmik F12SE) to blend sub integration. Was able to get a relatively flat frequency response as measured with Audyssey MultiEQ-X & the Audyssey microphone with a known frequency response. 
My next step is to use the UMIK-1 with REW. 

I use an SVS sub which has very comprehensive DSP over most parameters. Changing the rolloff to 24db instead of 12 makes a huge difference in how it interacts with the mains. I also use a 24db HPF on my mains to reduce the bleed. I tried two subs but found one works better in my room. 

Integrating a sub takes time and effort. How many, location, filter settings, EQ, and phase all work together in complex ways. It's not much different than setting up your mains. Listening, measuring, trial and error with settings, and sufficient time are all part of the process. 

I have a pair of rel subs that I have setup where you can’t tell where the subs are located and you think the bass is coming out of the revels.

what model rel to get is room dependent. Some people say the t5x are very musical. I went with the bigger rels.