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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
knownothing
1,725 posts
 

Someone just mentioned subwoofer volume.  There was a recent thread on Agon where this was discussed and turning down both the crossover frequency and the volume on my sub did wonders to clean up the sound in general and reduce the localization of the bass in my room at certain frequencies.  This for a single sub application in a medium sized room.

As for REL subs, it has been suggested already that the S/812 would be a better match for the C7’s than the T5/X, and I agree.  If your room is on the smaller side, the S/512 might be better, or even the Classic 99, less hammer, more dulcimer.  The lack of crossover slope adjustment to match the ported C7 may be an Achilles heal for REL, but I have not heard this complaint before related to paring with Harbeths.

kn

knownothing
1,725 posts
 

There is also this:  https://rel.net/pages/speaker-pairings

desktopguy
423 posts
 

I have had consistent success in adding a sub (first the SVS SB1000, then a JLAudio e110) to my home office’s desktop system. There are 2 keys to success, in my experience:

1 - I use an external crossover with 24 dB/octave high- & low-pass filter slopes.

2 - I can run the speakers full range if I wish, but I find it’s absolutely critical to use a high-pass filter to cut off frequencies below the point where the sub will operate. Failure to do this creates a muddy, indistinct and bloated sound in the upper bass and lower midrange.

3 - Finally, I use sealed/acoustic suspension mains and sub. I find this design gives not only the most predictable, easy-to-manage bass overall, but also give bass that is qualitatively better than ported designs. This is ideal for music-only listenings. I might feel differently if I was using the sub in a home theater, but for music appreciation, sealed/acoustic suspension mains & sub give me the best results.

rwwear
2,909 posts
 

Just get an SVS sub and enjoy your system. Also try running your mains full range to keep the electronic xover distortion out of them.

dbastin
24 posts
 

Feim my Adventures with Subwoofers, here are some things that seem critical to solving integration.

Firstly, low end highlights smearing most. If your source is allowing smearing, focus on that otherwise the rest will be a battle.  For example, noise in you ethernet system is, in my experience, a damaging source of noise that causes smearing. Also subs power cables, interconnects and fuses all contribute.

Next, you need to be able to place subeoofers according to room acoustics, which means you need to be able to delay the main speaker output.  Adjusting phase might sound similar, but it's a convenient short cut.

Delay needs to account for not only distance but also the latency of the subwoofer - it's filters, amp, acoustic design, etc.  This is not to say subs are slow,just a tad late.  12ms is alot later than 4ms.  It's enough to cause smearing.

It's best to control the slopes of both the subs and the mains, so both HP and LP filters are needed.  The volume level of the sub can ruin the crossover blending 

24dB slope better than 12dB because it's over less frequency range.

Choose a crossover frequency that allows best tone,which may be influences by placement of the sub/s and their interaction with the room.

All this dialing in should be the foundation, the neutral/correct, for then choosing what you prefer.  EQ can help tune to suit preference if you prefer a less neutral ... suits you hearing (eg. change with age).

I hope this is helpful.

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