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An alternative to powered sub woes?

Yesterday, I took home a trial a REL R305 sub to go with my C220/MC252 and Sonus Faber Guarneri Homage. The room is 11x14x9. I am driving the REL from the MC252's speaker posts (as recommended). I read all the instructions about proper placement and setting of level and xover points, etc. I tried a bunch of different level/xover settings and room positions (in 1", 1/2" and even 1/4" inch increments) and angles.

Four hours into this and I still haven't found anything close to satisfactory - let alone an improvement in sound over my sub-less set-up. I am getting more bass, no doubt about it, but I don't like the it's quality and how it integrates with rest of the sound spectrum.

When it comes to subs, people are often concerned with lack of speed but what I keep hearing is almost the opposite - the sub seems to beat the Guarneris to the punch and the two just don't seem to "play well together". It's hard to describe it in words (perhaps coherence is the word I'm looking for), but easy to hear.

I will spend some more time on it tomorrow - after giving my ears and head a chance to recover, but I believe that what I am experiencing is a significant and hard to reconcile difference in sonic signature - which should not be too surprising given the REL's digital switching amp.

Another problem is that more bass = more room acoustic problems. I have very limited flexibility in terms of positioning speakers and listening chair and there are 25 and 50Hz peaks that are hard to defeat and are now accentuated.

As I was going through this, I remembered reading an article in some audio magazine about this very problem of smooth integration between subs and the rest of the system and room acoustics. The writer thought that, in many cases, a better solution would be to take the low-level signal off the pre-amp, pass it through a digital eq (to perform low-pass filtering and equalize away room problems), send it to the same model amp being used for the main speakers, and then go to a passive sub-woofer.

In other words:

pre --> power-amp --> main-speakers
|
|--> digital eq (low pass + room eq) --> power amp (same as above) --> passive sub

According to the writer, this would have several advantages:

1) Takes care of room eq problems and allows an low-pass xover curve to match the main speakers roll-off. Gives more flexibility in positioning.

2) Using the same amp for main and sub would keep similar "sound signature".

On the down side, cost (ideally another McIntosh MC252) and the fact that passive subs are not that easy to find anymore.

The other alternative is to forget this subwoofer thing altogether (this system is a pure 2-ch, music only system, not a home theater) since the pluses from that extra bottom octave punch come with a problems of their own.

Any thoughts? Has anyone else given up on subs for similar reasons or tried the eq +matched amp + passive sub route?

Before going all out (or forgetting subs altogether), I am planning to find a passive sub, use a spare, older, McIntosh amp and Behringer DEQ2496 and see what comes out.

Alberto
__________________
Main System:
McIntosh: MCD201, C220, MC252, MR80
Thorens TD125mkII, SME 3009II, Clearaudio Maestro
Sonus Faber Guarneri Homage, AKG K1000, Sennheiser HD580
as1963
6 responses Add your response
Post removed 
eldulcesol
197 posts
 
As, before you go out an get an digital eq or anything, turn the sub 90degress each way if that will help as suggested from Mapleshade free tweak. This did work quite well for me when I had forward facing sub.

If you are using the Rel Spekon cable, try something else. It is the same type of cable that came with my MJ200s and it sounded terrible. Fortunatly I had an extra set of speaker cables (Cardas) which I terminated with the Spekon plug from the cables that came with the subs. The end result was tighter, controlled musical bass with the entry level cables. If you do this, the polarities are marked on the inside of the plug with screw fasteners. It is a cheap tweak that you can experiment with before going for the eq.
audiokinesis
2,740 posts
 
AS1963, I posted a somewhat detailed reply to your inquiry on Audio Asylum.

Briefly, I'm not sure that your sub's crossover filter is steep enough to blend well with your Sonus Fabers. Also, equalization can correct the frequency response for one location but may actually make things worse for other locations within the room. The problems of reproducing smooth bass in a small room are formidable, as the room acoustics works against you by imposing a nasty peak-and-dip pattern on your subwoofer's output. This peak-and-dip pattern will change if you move the subwoofer to another location, so one way to get smooth bass in a small room is to use multiple small subwoofers spread around the room instead of one "ubersub". This will average out smoother than any single sub would be. This smoothing is the main benefit that people derive when they add a second subwoofer.

Researcher Todd Welti published an article on the subject that you can read here:

http://www.harman.com/wp/pdf/multsubs.pdf

He advocates using four subs, located symmetrically around the room. I prefer using an asymmetrical configuration, as advocated by Earl Geddes (this might look like it's the same link but it's not):

http://www.gedlee.com/downloads/sub%20study%20.pdf

One other point I neglected in my Asylum post: If you go with a scattered multi-sub setup, you'll need subs that have a steep low-pass filter so that upper bass energy doesn't leak through and disclose the location of the subwoofers.

Multisubs allow you to experiment with unorthodox polarity schemes. In some rooms, it sounds better if one or more of the subs operate in reverse polarity, as this further decorrelates the low frequency energy (which is desirable).

Best of luck to you.

Duke
dealer/manufacturer

disclaimer: Note that in this post I am advocating a technique, not a specific product.
trianglezerius's avatar
trianglezerius
119 posts
 
I was recently in the market for a sub and had REL high up on my list. Then I started ready up on MJ Acoustics and found them to be really intriguing and the perfect size for my room. So I pulled the trigger and bought the Reference 100 MKII since a few recent audition of the newer RELs weren't very satisfying. I'm looking to add a second MJ later this year since room placement is less critical it seems. Plus it blends seamlessly with my currently speakers perfectly.
Post removed 
swampwalker's avatar
swampwalker
5,138 posts
 
If you have two very specific room node peaks and no significant valleys, you might try reading up on the Rives Parc bass equalizer. It will allow you to precisely attenuate those peaks; its eq is parametric and fully adjustable, IIRC. They even have a new one with an amp built in for a passive sub.
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