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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.

erik_squires
mijostyn's avatar
mijostyn
8,570 posts
 

@gdaddy1 Subwoofer manufacturers are in business to sell subwoofers PERIOD.

They could care less about the performance of your system. Rel is handily the worst but the vast majority of them do the same half baked thing and supply their subwoofers only with low pass filters. Their reasoning is if they make things more complicated and expensive nobody would by their units. The sad thing is they are right. Digital subwoofer management has been around since 1995, invented by Radomir Bozevic (the Boz of TacT Audio). Some subs include a watered down version of room control but without a high pass filter they have no control over the main speakers which is 50% of the issue. Proper bass or subwoofer management has to know what the main speakers are doing to mate the two correctly in time and phase. Then there is the marked improvement in main speaker performance when you relieve them of the lowest octaves. This can only be done by direct measurement of a system in it's own environment. Any other way is wishful thinking which you seem to be very good at. 

There is, at this time, only one best way to integrate subwoofers into a system and that is with Digital bass management. There are now units available from MiniDSP and Anthem that are very reasonably priced. Benchmark Media Systems uses a MiniDSP SHD Studio with two of their DACs to run their own system and they get great results with it. (Dirac Live) For people who can spend more there is the Trinnov Amethyst and the DEQX units which will be available to the general public shortly. The Anthem STR preamp is 1/2 the price and a great performer.

@clio09 One of the best thing about digital signal processing is you can add subwoofer and eliminate the "bump". Full range speakers like ESLs benefit the most from a high pass filter. 

james633
1,040 posts
 

Any negative to these very high crossover slopes, 48db etc? 

mijostyn's avatar
mijostyn
8,570 posts
 

@clio09 I did not know anything about Roger until I bought some of his tubes, the best I ever had. I use Sound Labs speakers and before that Acoustats.  I have been crossing between 100 and 125 Hz for 30 years. It requires a very steep slope to keep the sub out of the midrange. The reason so high is that full range speakers are very susceptible to Doppler Distortion. I chose 100 Hz because that is the point that I could not see the diaphragm move. Aside from lower distortion I get another 10 dB of headroom. ESLs will go extremely loud if they do not have to make low bass and they don't have to force an amp to drive a 30 ohm load.

clio09
3,356 posts
 

ESLs will go extremely loud if they do not have to make low bass and they don't have to force an amp to drive a 30 ohm load.

@mijostyn that is kind of my point for crossing over as high as possible, but Roger always told me the amp has a say in this so for the mains speakers if we can keep the amp from seeing difficult loads it will be happier and run more efficiently with less distortion. Case in point is a Music Reference RM-10 on a set of QUAD ESL speakers. While on it's own it does a fine job, in a active bi-amp arrangement with a 100 Hz LP and HP it relieves it of having to drive the high impedance in the bass. For the bass speakers Roger just advised me to get a decent solid state amp with good damping.

gdaddy1
135 posts
 

@audiokinesis Did you ask any of them why they chose to not high-pass filter their main speakers? 

Yes. The majority of the speakers were very capable of producing strong, impactful bass without using a sub. So, they were fed the full unrestricted signal. 

So my point is why on earth would you restrict and high pass filter using any of these speakers when they are perfectly capable on their own? For this reason you don't see any restrictive high pass filtering method being used.  @mijostyn Not wishful thinking, just a fact.

Very simply put... these speakers are allowed to perform as they were designed by the manufacturer without any unnecessary attempts to make them sound "even better" by choking them down and adding complexity.

@mijostyn ... I believe ALL speaker manufacturers are looking to "sell speakers" not just REL.

 

 

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