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15" vs 18" subwoofer - which to buy?

If price and room space/aesthetics were not a big issue, is there any reason to get a 15" subwoofer over an 18" one? My main issue is not disturbing the neighbors too much. I'm confused about the difference between a 15" and 18" subwoofer. I want to get the best sound quality possible for low-to-medium volume use.

I've heard that an 18" subwoofer can be played at low decibels and provide good bass resolution and fullness of sound, while to achieve the same volume with a 15" subwoofer, the power has to be much higher. So for any given sound volume, the main difference is in distortion- and higher distortion sound may be more obtrusive. Is this true? it seems counterintuitive that an 18" subwoofer could be better for neighbors than a 15" subwoofer.

However, I compared a B&W800 (12") vs B&W850 (15"). I listened from the other side of the store wall (not as thick as my apt), and at minimum levels which I found satisfying for HT, I found the 12" more obvious and 'boomy' sounding while the 18" produced a more subtle (though actually more powerful), lower frequency vibration, like a very low-level rumbling background earthquake. The 15" subwoofer did seem more of a disturbance because of it's 'obvious' sound. However, I worry that an 18" won't even start producing quality sound until a certain volume that was much higher than a 15", and consequently potentially more disruptive for neighbors. Is this true? What is the relationship between subwoofer size, low sound volume, and subjective listening experience?

Unfortunately, it will be difficult to get an opportunity to hear both the DD-15 and DD-18 which I am considering, so I hope someone can help out here.
no_slouch
c123666
871 posts
 
I asked Tyler acoustics for a quote on a custom subwoofer with the following design parameters:

purpose is to use with single ended tube amps and very efficient speakers....the sub must be "quick" enough to keep up with demanding bass passages and the mid/hi frequencies.

dual 8" drivers arrayed vertically
one speaker input straight to the drivers
one speaker input with a quality passive crossover (cut at 60 to 75hz)
non ported design
high efficiency so can be driven by a tube amp if desired (intention is to build a mono tube amp that will only operate in the bass frequencies and opimtized for bass duty)..output control on the amp would control the level

Tyler quoted me a price of 450 for a basic black ash woofer based on these specs and estimated the bass output would go to 30hz or slightly below.

An AudioAero dual 8" sub which supposedly hits 20hz recently sold very cheaply locally. I missed it by a couple of days.
This is supposed to be an excellent product but that is only hearsay.
eldartford
4,262 posts
 
I think that for LF, and especially for SW, the more cone area the better, although, as Sean says, there are other imnportant considerations. The large cone area is not to play louder. It is to play with the proper loudness without need for extreme cone excursion. A small subwoofer must be very loud one foot in front of it because the sound pressure must spread out to fill the whole room, with the SPL falling off rapidly with distance. If people used multiple 15" subwoofers (one for each speaker system) there would be less chatter about the difficulty of locating SW in the room.
gmood1
1,251 posts
 
Eldartford you make a good point. I know some don't understand the concept of multiple subs in a system.
I think you hit the nail on the head. This is why I have went this route.Blind folded it will be nearly impossible to point out the subs in my system.
no_slouch OP
48 posts
 
Thanks for your responses so far. I will audition Bag End and Martin Logan, in addition to Velodyne. Up to now, I am inclined towards Velodyne because of the easy built-in room correction features. I'm not sure that Revel is available in Hong Kong, where I plan to make the purchase. I will also look into the Aurios and Auralex Gramma, recommended from a previous posting.

I guess I have a very basic question..before getting into differences in speaker design, if possible. That is, is it possible for a large subwoofer (or several smaller subwoofers in one enclosure) to be effectively played at an equally low volume as a small subwoofer? I'm really not concerned about large volume sound for the medium-term, and want to achieve the best possible sound, i.e. bass extension, resolution/clarity, and fullness, at extremeley low to low volumes. All other things being equal, should i just get the largest subwoofer (or largest total cone volume, for those who advocate using several smaller cones) possible? I guess I don't understand the physics involved..

my Velodyne dealer recommends the 18" over the 15", independent of room size (mine happens to be about 14 x 35 feet), placement issues and price. he said the main reasons people would go for the smaller subs is because of price and lack of physical space for the cabinet, and that inside this subwoofer line, volume/neighbor issues are a total non-factor, since i have control over the volume. is this true at low levels, or is there a "minimum" effective volume threshold for the 18" which is higher than for the 15"?
rives
953 posts
 
I'm going to recommend something entirely different. Get 2 lesser subs rather than one big one. You can place them in such a way to cancel out certain room modes and get a much more even response throughout the listening room. I also think those with parametric eq built in is very useful, you can fine tune the one mode (floor to ceiling) that you usually can't do much about based on positioning. The Harmon Group wrote a great paper on number of subwoofers. There's a link to it on our resources page. There's also a paper we wrote on speaker placement, which includes subwoofer placement.
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