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.



Your subs look great. Are they push/pull or dual opposed?  Have you ever tried precast concrete tubes?

FYI..I don't use REL subs. I just use that crossover/volume method. My experience has yielded a great end result that's cheaper and easier and sounds great to me.

An advantage of going to an audio show is you get to hear some of the best speakers in the world and then go home and compare. Otherwise the imagination can take take over in beliefs that are not based on reality. IMHO.

@clio09  If the amplifier could talk and express an opinion on filters, slopes, and frequencies, not to mention phase and damping we might be a bit surprised. After all its the amp that is coupled to the speaker.

During the development of their sensor technology beginning with the SMS-1, Digital Drive and finally with their DD Plus, Velodyne Acoustics (USA). While it doesn't talk it simply listens to the mains, subwoofers within the room as it makes your suggested adjustments and many more.

Briefly, using a Texas Instruments platform and Code Composer Studio which enabled a broad range of coded controllers of multiple variable parameters within multiple low frequency bands. The end result are audibly and graphically viewable automatic and manual parameter adjustments saved to memory presets. 

With the Plus release the manufacturer fully adopted the subwoofer crawl as the first step implementation. 

If you put the mains through a capacitor that was not previously there, what does that do to the overall phasing of the drivers, including the mid and high that now have an additional capacitor in their circuit?

What influence would this have on soundstage and imaging?

I run my speakers at 2.5 ways using an 18", a 9.5", and a Heil. I’ve put the cap on the 9.5" (run as three ways) and it is a loosing proposition as I lose a lot of the low end volume near the crossover frequency. I’d never considered it with respect to soundstage and imaging.

Also, different types and makes of caps have slightly different sounds. It seems that putting a cap on the mains will then create some degree of coloration that would not otherwise be there.

In another vein, yes a small sub is "faster" than a larger sub at the same volume level.

Ultimately the volume is directly related to the volume of air moved. Because a smaller cone must move further to displace the same volume of air as the larger cone, and it must make its displacement in the same amount of time (Hz), it travels a further distance in the same amount of time. Speed is defined as distance over time and a faster speed means that a further distance is moved over the same time frame.

So, then, the smaller cone is ligher making it easier to move, possibly reducing "flop/flutter".

But again, the cone travels faster and force is defined as mass times velocity squared. So while mass is a linear function, speed has more impact on the force required to make the cone change direction because it is based on the square of the speed and these forces must be overcome at each cycle of the cone.

@mijostyn wrote:

I have no experience with horn subwoofer. For most of us they are impractical do to size constraints. For sure distortion will be lower for any given size driver due to efficiency. They problem is low bass will rattle and resonate almost anything. IMHO is is much easier to make a small enclosure resonance free with clever design and balanced force construction. It will not come remotely close to the efficiency of a horn but is way more practical from a size perspective.

"Practicality" mostly comes down to convenience, aesthetics and making a decision about something, not what's strictly and barely possible to physically and acoustically integrate in one's home surroundings. You are right about the majority of audiophiles balking at grand size, to which manufacturers certainly cater, but who cares about the majority of opinion when all that matters is meeting a performance envelope in a dedicated listening space, from a DIY-approach and defined by oneself? I don't care about practicality or what's at first easy, as long as the damn things can get through the doors and be properly located in the listening room. Done. Henceforth (or for a while) they're no longer impractical and are well out of way in their respective corners - even at 20 cubic feet per cab. It's really about the will of things and what one sets his mind on.

And you don't think 8x12" sealed cab woofers crawling below 20Hz can make things rattle at elevated SPL's? My TH's will bend the windows at war volume, but there's no reason to go there. It's about how they sound at listening levels we're usually exposed to, and that there's an abundance in reserve even at our max. desired SPL's. Ease of reproduction is paramount. 

Please keep us updated on your quad cab subs development. They look great even with raw surfaces, and I'm sure the sonic outcome will turn out to be quite awesome. 

You are doing exactly as I suggested for crossover and slope. The game is keeping the sub out of the midrange or you will have mud. You are running 85 Hz @ 36 dB/oct. If you move up to 100 Hz you will have to steepen the slope.

We'll see what comes of it. If we're able to sufficiently clean up the upper band of the TH's I feel rather confident maintaining 36dB/octave slopes will do fine. 

I can change crossover points and slopes on the fly which is very helpful for AB comparisons. 

As can I.