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Adventures With Subwoofers

 

My System:

Aurender N20

MSB Discrete DAC

Accuphase P4600 Amp
Harbeth C7-ES-XD Speakers

The Harbeth’s are -3db down at 45Hz. They have useful output down to around 35-40Hz. I wanted to fill out the lower octave from 40-30Hz.

I started with two REL T/5X subs I successfully integrated with the ATC 11 speakers I owned previously. They were -6db down at 55Hz.

After weeks of effort with these subs plus an older REL T3 I gave up. No matter what combination of crossover and volume I could not prevent the subs from bleeding into the lower midrange. The result was a loss of air and soundstage openness. Even at the lowest crossover the result was the same. Even voices were affected. I realized that these RELs especially when using the High Level Speaker connection are bass reinforcement and not true subs. I think if I had a way to externally crossover them and use the low level connection they might work as the REL/Harbeths would no longer be doubling the 35-60Hz range. But there would still be overlap in the 70-120Hz range. That would also mean the beautiful Harbeth upper bass and low midrange would now be appropriated by the RELs. So I sold the two T/5X subs and gave the T3 to my grandson for his gaming system.

Then one day I decided to ask ChatGPT why the RELs could not be configured to stay out of the midrange. The AI said it was because the RELs had a crossover slope of 12db per octave and that I should try a sub with a 24db per octave slope and recommended the JL Audio d108.

So with a 30 day return option I tried the D108. After about two weeks of testing I found it much better specifically because I could set the crossover to between 25-30Hz. But in the end I still noticed, to a somewhat lesser degree, the same artifacts especially on voices and soundstage openness. But I really loved the sub itself. Very well made and powerful. So I moved it to my home studio where I had just purchased Genelec monitors and it blended perfectly.

I really don't have an issue with the Harbeth’s low end response as almost all music sits in their range. I listen to predominately Classical and value an open airy soundstage which I get from the Harbeths.  I was hoping by adding a response down to 20-25Hz I might improve soundstage depth and support the lower harmonics. But I strongly prefer their response without subwoofers. I think if I listened to mostly Pop, Jazz, EDM or Soundtracks where I would not notice the soundstage openness as much the subs would work. But I crave that concert hall liveness,

jfrmusic

Showing 1 response by blisshifi

blisshifi's avatar
blisshifi
1,252 posts
 

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). 

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