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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
 
Find a Bag End dealer and audition one of the best. Go review their site; think they may offer both sizes. Great product, rarely found used.
cytocycle
1,043 posts
 
If you go BagEnd you need to buy the 18" the 15" wasn't rated a very good value compare to the minimal extra cost of the 18". But the acoustical shaping that the DD's provide will definitely outclass the uncorrected BagEnd. You will need to use a Berinhger or Audio Control Richter Scale or other EQ to correct for the room accoustics and placement to truely compete with the DD's.

if you want your neighbors to have a chance float your sub with a decoupler like the Aurio Pro's (that's what I use on my Velodyne 18") and then mass load the top of the sub with 25lb back of #6 lead shot to tighten the response.

I am also considering the Velodyne DD15 and DD18 since I have an older F1800X without correction (which I will keep to use with the DD15). In my research I am going to go for the DD15 because the only thing different is the size of the enclosure and driver, and I don't need more max output. The other option is to do a pair of bagend 18" (commericial)with a Crown K2 amp and a Tact or Berinhger digital correction system, but I haven't been able to figure out whether I can actually hide 2 18" enclosures behind my couch.
bignerd100
515 posts
 
It is time to start believing the tales told to women. Size (in this case) does not matter. A larger woofer will move lots of air and make deep bass. However, it is difficult for an amplifier to do this with any accuracy. How much air do multiple small drivers move? Lots of air with more authority and precision. Check out the Martin Logan Depth (three 8" drivers) for small to moderate sized rooms and the Martin Logan Descent (three 10" drivers) for small to huge rooms. These are three spun aluminum (light and easy to move) drivers positioned in a triangular array (directly opposing each other to cancel out internal cabinet vibrations). They are also servo controled which means that they start and stop when they are supposed to. This is a big problem with larger woofers. They have more mass and air resistance to their movement which increases the lag-time between the time that the amplifier tells them to start/stop and the point in time that they acctually do this.

Another big consideration is tweekability. The ML subs give you a high level of adjustability as far as phase, crossover point, and low level cut/gain. There is an adjustment knob centered at 25Hz that gives you up to 12db of cut/gain. THis can help smooth out common room modes that give you boomy bass. Every room has peaks and nulls. There is little that you can do about these without tearing down a wall. By moving the sub around the rooom you can find a position that doesn't excite peaks too much and through phase adjustments you can demphasize the nulls. An equalizer that does not mess with the mid-bass (this 25Hz knob) can also be most useful.

Two cents.
sean
6,231 posts
 
There are too many other design factors to consider than just cone area, especially in your "limited use" situation. This is why we have Thiel-Smalle parameters as it describes most all of the aspects of the driver. Once you know all of those factors, then you consider cabinet rigidity, volume, bass alignment, etc...

Other than that, driver size has nothing to do with efficiency or cabinet volume. It is quite possible to have a 12" that needs a bigger box and requires more power than an 18" driver. This all depends on the above mentioned factors and the over-all design of the product.

I can't really point you in any specific direction as i stopped looking at subwoofers a while ago. Most are ridiculously priced and under-designed. After all, a passive sub is basically a woofer, a cabinet, some stuffing, binding posts and some feet. How they think that this costs as much as multiple drivers, complex crossover networks, etc... I don't know.

The one thing that i would suggest would be to try and listen to / compare some sealed designs to vented designs. The one advantage that vented designs offer is that they will play louder. Since this is not a major concern of yours, you can take major advantage of the improved transient response, increased damping, lack of overhang and ringing, slower resonance, more controlled output at resonance, etc.... of a sealed box. You'll also get less "bloat", which means you probably won't annoy the neighbors as much. Whether or not you prefer the sonics of this type of design is a personal matter, but i thought i would mention it. Sean
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