Subwoofer speed is in the room, not the box

First, if you like swarm, that’s fine, please start a thread somewhere else about how much you like swarm.

I want to talk about the impression that subs are fast or slow compared to planar or line sources.

The concern, and it’s correct, is that adding a subwoofer to say a Martin Logan or Magneplanar speaker will ruin the sound balance. That concern is absolutely a valid one and can happen with almost any speaker, not just speakers with tight dispersion control.

What usually happens is that the room, sub and main speakers aren’t integrating very well. Unfortunately for most audiophiles, it’s very hard to figure out exactly what is wrong without measurements or EQ capabilities in the subwoofer to help you.

So, there’s the myth of a small sub being "faster." It isn’t. It’s slower has worst distortion and lower output than a larger sub but what it does is it doesn’t go down deep enough to wake the dragons.

The biggest problems I’ve heard/seen have been excessively large peaks in the subwoofer range. Sometimes those peaks put out 20x more power into a room than the rest of the subwoofer. Think about that!! Your 1000 W sub is putting out 20,000 watts worth of power in some very narrow bands. Of course that will sound bad and muddied. The combination of sub and main speaker can also excessively accentuate the area where they meet, not to mention nulls.

A lot is made about nulls in the bass but honestly IMHO, those are the least of our worries. Of course too many of them can make the bass drop out, but in practicality is is the irregular bass response and the massive peaks that most prevent any good sub from functioning well in a room.

Bass traps are of course very useful tools to help tame peaks and nulls. They can enable EQ in ways you can’t do without it. If your main speakers are ported, plug them. Us the AM Acoustics room mode simulator to help you place your speakers and listening location.

Lastly, using a subwoofer to only fill in 20 Hz range is nonsense. Go big or go home. Use a sub at least at 60 Hz or higher. Use a single cap to create a high pass filter. Use EQ on the subwoofer at least. Get bass traps. Measure, for heaven’s sake measure and stop imagining you know a thing about your speaker or subwoofer’s response in the room because you don’t. Once that speaker arrives in the room it’s a completely different animal than it was in the showroom or in the spec sheet.

Lastly, if your room is excessively reflective, you don’t need a sub, you need more absorption. By lowering the mid-hi energy levels in a room the bass will appear like an old Spanish galleon at low tide.


@phusis I don't think we can entirely stop talking aobut potential solutions, whether that be my preferences, SWARM or a horn loaded woofer, because ultimately they all prove the idea that large drivers aren't fast is simply not the real problem.

@audiokinesis is not wrong, but the SWARM solution, like adding EQ, and traps, is probably NOT what audiophiles expect when they first think of adding a sub.

Again I agree, but audiophiles are less about education and more about aimless tweaking. So when they add a sub they expect it to be plug and play and not something they have to educate themselves on.

The idea that large drivers have excess stored energy which they can’t get rid of fast enough is bunk. That, and that alone, is my point. Which set of challenges audiophiles decide are best for them is for another thread.

I think the Danny Ritchie video linked earlier by @deep_333 proves this point, although I have had good success with 8" and 10" drivers and have no desire to go larger than that.


@james633 Anyone that has used a sub without a highpass is doing it wrong.

After crawl test positioning and playing the Sweep Tone CD the Velodyne Plus software measures the speakers from 200Hz and the subs from 100Hz - 15Hz in room simultaneously.

The software automatically feathers in the subs fourteen Optimization Parameters within the eight frequency bands beginning at 100Hz self designing a crossover region that uncannily maintains the speakers low frequency presentation quite closely as they roll off, in roughly twenty minutes.

The speakers remain in the analog chain at full range during the process.

While high pass filtering is a Plus option, with an abundance of speaker amplifier power the filtering is noticeably less desirable.


I have had good success with 8" and 10" drivers and have no desire to go larger than that.

In many rooms that may very well be ideal.  While I could argue you'd get more out of a larger sub, there are dragons in the depths and not messing with success is a good principle to live by.


While high pass filtering is a Plus option, with an abundance of speaker amplifier power the filtering is noticeably less desirable.

Honestly disagree. There are measurements showing that less bass = less IM distortion from main speakers, and many attribute this reduced IM/doppler distortion to some of the benefits possible. I’m not sure how much of that matters, but I can say, conclusively, that the high pass filters absolutely make the main speakers sound better.

Also, as an aside, Monitor Audio recently produced a high tech speaker, not sure if it was a prototype, with woofers facing each other, so you listen at 90 degrees to their motion, and I’m convinced this is an attempt at solving that particular problem.

From a power/efficiency point of view, you are right, no reason to high pass or use active crossovers in a home environment, but if you ask me if it sounds better, I am completely convinced it does.