Hi Duke, since you have lived with Soundlabs, which subs work best for planars, if any? JLs, SVS...? Or would you recommend dipole woofers like Gradient or BG Radia?
Excellent question!
First, by way of background, dipole speakers really do have demonstrably smoother in-room bass! A researcher by the name of James M. Kates published a paper on the subject a number of years ago, and the room-interaction superiority of a dipole vs a monopole was evident.
Likewise, distributed multiple subs really do have smoother in-room bass! So you can probably guess where I'm headed.
We can see some anecdotal evidence of this in the internet posts made by people with Maggies. Many Maggie owners have tried subwoofers. If you peruse the experiences they've posted, if they only tried one sub, they often were initially impressed but eventually went back to just the Maggies all by themselves because the discontinuity was distracting. But if the Maggie owner tried
two subs, most of the time he kept them in his system. I think this is because there was less discrepancy between the in-room response in the region covered by the Maggies, and the region covered by the subs. I believe that four good subwoofers, intelligently distributed, will approximate the in-room bass smoothness of two dipoles, and that is why my multisub system has four subs.
You see, before SoundLabs, I had Quad 63's with Gradient subs. Very nice pairing, except that they were lacking in impact. Being a long-time hardcore amateur speaker builder, I set out on a quest to build subs that were "fast enough" to keep up with the Quads, but would have the impact that the dipole Gradients lacked. This was years before I'd ever heard of multisubs. I tried sealed, extended bass shelf vented, aperiodic, isobaric, transmission line, high-displacement equalized dipoles, and maybe others that I can't think of right now. I finally gave up.
Then one day, I think it was at CES 2006, I was taking Earl Geddes to the airport in Las Vegas. We were stopped at a stoplight. Out of the blue he said to me something like this: "Duke, I've figured out how to get good bass in small rooms. Use a bunch of small subs scattered around the room. Each will have a different response, but the sum will be smooth." That was it! That was the answer! I replied, "That's brilliant! Can I license that idea from you?" He said, "You can just use it." And then the light changed. It was that fast, and I had a completely new paradigm.
Going back to your question, I think that the improvements from going to a multisub system significantly outweigh the differences between JL vs SVS vs REL vs Seaton Sound vs whatever. I had arguably covered a pretty wide range of subwoofer characteristics in my aforementioned DIY quest, and going multisub was by far better than any of them.
Once I had embraced the multisub paradigm, the question of what specifically those subs should be naturally arose - which is right back to the question you asked. I had a lot of tricks up my sleeve, but by now I was a manufacturer, so this had to be commercially viable, which in world means that cost-effectiveness is critical. I was sold on the idea of not looking at subs independent of their room, but rather of seeing subs + room as an inseparable system, so I wanted to take the room into account from the beginning. In the course of my investigations, I came across the idea that typical room gain is roughly 3 dB per octave across the bass region, this from several sources. So my target response became the inverse of room gain, which would be a gentle 3 dB per octave rolloff across the bass region. The most cost-effective way to achieve this was with a vented box, using a woofer with a particular range of parameters in the right sized box with the right tuning frequency. The same thing can be accomplished with an equalized sealed box, but it's not as cost-effective.
Now intuitively we all know that sealed boxes are "faster" than vented boxes, and this is demonstrably true, but the implications of the ear's poor time domain resolution at low frequencies brings into question whether or not we are actually hearing this "speed" difference (which arises from the vented box's worse group delay characteristics). In fact, I read an Audio Engineering Society paper that showed group delay of the same magnitude as we'd typically get from a vented box to be statistically undetectable on music and barely detectable on test tones. So if it's not group delay that makes vented boxes sound slow, what is it??
I think it's the room! Most vented boxes start out "flat" to a considerably lower frequency than a comparable sealed box, but then we bring in room gain, and our sealed box is now closer to "flat" but our vented box will have a hump down low, and
that is what makes it sound slow! We can take that same vented box and put it outside, where we get no room gain, and it sounds tight and fast, maybe even erring on the "lean" side. Its speed hasn't changed, but its effective frequency response has.
So out of the well-respected high-end subwoofers on the market, I would look for the ones that take room gain into account, or that can be equalized to do so (which I think they all can via outboard DSP).
Just for the record, I am NOT claiming that my room-gain-compensation tuning is superior to a high-quality equalized sealed box (and the ports on my subs can be plugged to transform them into sealed boxes, which can then be equalized). I am only claiming that it's a bit more cost-effective way to get there... my target market is probably not well-represented on this forum!
If I didn't have to worry about cost-effectiveness, nor crating and shipping, I'd probably go with equalized sealed isobarics. And frankly those big "dual opposed" configuration Seatons look pretty sweet to me.
Imo, ime, ymmv, etc.
). There will be at least two more box subs ... Will use Acourate most likely...
