Accurate non-boomy sub for satellite system

If you DIY, try to design for a fairly low, near 'critically damped' 'Q' of about .71
Above abot 1.0, a speaker will start to have problems with peaky bass/ poor control while too low....bass gets 'thin'.

One problem with most vented subs is that they are approximately "flat" under anechoic conditions, often down to a very low frequency. So when room gain is factored in (typically +3 dB per octave below 100 Hz), the result is a slow and bass-heavy presentation. Yuck.

A sealed box typically avoids the problem of excess deep bass energy, which is definitely an improvement. Its rolloff slope is closer to the inverse of room gain. That being said, I think it's possible to do even better.

"Even better" is a low-tuned vented sytem designed such that its anechoic response rolls off at about 3 dB per octave from about 100 Hz down to the tuning frequency, below which it of course rolls off rapidly. Even this doesn't solve all the problems - there's still the inevitable peaks and dips imposed by room interaction, and these can ruin an otherwise good sub's presentation. Rather than equalization, I suggest using multiple small subs distributed asymmetrically around the room, so that the sum of their individual peak-and-dip patterns is smoother than any one of them would have been.

In other words, work with the room instead of fighting it - sort of an acoustic application of the "sometimes it's easier to plow around the stumps" concept.

Duke
dealer/manufacturer

Duke,

I recently added two small subs (Velodyne SPLR 8") and extensive experimentation with room placement allowed me to reduce 15db peaks to 11db - 12db peaks (AFTER utilizing the onboard auto eq function on the SPLR subs). An outboard PEQ (Velodyne SMS-1) allowed fine tuning and I managed app +/- 3db from 25hz to 200hz. Inserting the SMS-1 between my Verity Parsifal monitors and actively crossing to and biamping the Encore woofers took me to +/- 3 or 4db between 38ish hz and 200hz from a very bad starting place. The crossover point and slopes I'm using are limited by the high pass in the SMS-1 and I suspect that a more flexible outboard cross would allow further improvements. (The trade off here was giving up about a half octave of pretty raggedy response in the deepest bass before EQ.)

I know that the approach is conceptually unappealling to many purists (I was somewhere on the upper portion of that list until recently), but the results are hard to argue with. This is audible improvement unlike any change to my system that I can recall over the last decade. I would never have tried but for a crappy new room. Now, I doubt I'll go back to unequalized bass.

BTW, the SMS is fairly cheap (app $600 at Audioadvisor.com) and -if you haven't already -you might want to play with one to see how it affects your opinion of EQ'd bass. Given your extensive experience designing speakers, I'd love to hear your reaction.

Just my experience.

Marty

Marty,

Thanks for your post.

It sounds to me like you combined multisubs with EQ, and this is an excellent approach. The reason is, with distributed multisubs the bass is much more consistent throughout the room, so that when you equalize you are more likely to be addressing global (throughout-the-room) problems instead of addressing problems in one location but making things worse elsewhere.

I have heard it argued that a single equalized sub will be smoother in the sweet spot than a distributed multisub (3+ subs) system will be. But I don't know anyone who has tried it both ways who prefers the single equalized sub. Let me quote from someone who has experince with both approaches:

"I’m 54, musician, assistant engineered & programmed synthesizer at the Sausalito Record Plant, been doing this since a teenager...

"My last room had the equivalent of about $6k worth of acoustic soffit installed to tame bass modes. Also heard the superb $100k YG Acoustics Anat Reference system (Yoav is a great guy, very down-to-earth, worth hearing if setup correctly).

"[Four small specialized subs spread around the room] exceeds the best sub performance I know of. You name the quality, it’s there in spades. Slam, low bass cutoff, power, etc. In pure musicality, pitch definition, transparency, realism, portraying differences in recording venues, this system probably sets the world standard. I’ve played electric bass; the acoustic guitar I sold last winter was a Martin HD-28LSV (purchased from Dave “The Ghost” Caspar of the Oakland Raiders at his home in his trophy room). There's a nice Chang grand upstairs. The capability of [the multisub system] to flatten the room’s bass modes blows away the above described soffit of my last room. I had to leave that soffit behind.

"[This] subwoofer philosophy may seem strange to the uninitiated, who might view four subs as about three too many. To them I reply: “Oh, really?” Take a little peek over at the circle for room acoustic modifications & read the pages about people trying to control bass modes. [The multisub approach], IMO, completely eliminates the need for any other contraption to flatten your modes. The automated digital EQ of my Sunfire Signature sub was almost completely worthless (in performance) compared to [the multisub system], which costs less."

This is from a post on another website, and I can provide the link if requested.

My opinion is that if the question is going multisub vs equalized single sub, the multisub approach is superior. The best possible may well be an equalized multisub system, which sounds like what you did. But apparently the multisub system used by the guy I quoted above worked pretty well without equalization.

Duke
dealer/manufacturer

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

Please read above for the Harman International take on this.
They really like the multisub idea, support it with both listening and hard data.

If my listening area wasn't so messed up / asymetrical, this is the way I'd go.....

How's that DIY coming? Plate amps are dirt cheap....buy 2!

Check out a sub on this site for sale from Adire. It is sealed with a 15" driver. The price is right too. I have their Rava which is a sealed 12". I have had it for years and works great. I also have a second sub from Hsu going in my room. The 2 together fill my room with great tight slamming bass. I have no doubt however that 4 would be fun.