show me the laser scan of the surface of the cone vs the input …. pistonic is as pistonic does….
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.
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No. I want the sub to do the most it can do in the proper range to produce a fast, punchy sound (30 to 50hz). MORE gain not less. (BTW...16hz has no place in music.) Why would you do that? Just curious.
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Good topic. It’s nice to "get the low down" on subwoofers from guys with a lot of experience with the subject. Adding to the small vs large conversation: Its been stated that speaker distortion is directly proportional to the movement (excursion) of the cone. Double the excursion, double the distortion. Cut it in half ... half the distortion. Taking the popular 10" and 15" driver sizes as an example, the 15" has to move less than half as much as the 10 to produce the same volume of air. Assuming that things are somewhat linear here (the "motor" in the 15" has sufficient power to do what it does well), the 15" will be cleaner at a given frequency and sound level. So, what about the added "mass" of the 15? We have to keep in mind that some of the "added mass" is the weight of the air itself. At the same frequency and same volume level, the "weight" of the air being displaced will be exactly the same. The differences will be the moving mass of the additional cone material, larger voice coil, etc. on the 15" which will be minimized by the cone moving less than half as much as the 10". Cone breakup is another form of distortion on larger cones that may also be offset by less cone travel being introduced. The quality of the execution by the manufacturer will be a key element here, but it is entirely possible that larger woofers will, in fact, have less overall distortion and produce "tighter" base than a smaller woofer. We ordered in a 31" raw woofer many years ago because we were "hot rodders" who liked to mess with outrageous stuff. A 31" woofer has more cone area than 6 12" woofers, as a reference. I recalled mounting this thing in a 6 cubic foot sealed enclosure and running some test tones thru it. The rafters were, literally, shaking all over the building. A walk back to inspect the woofer revealed that the cone was moving about 1/4". There’s no substitute for cubic inches. |
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