Re: Bass amp question for bass players
From what I can hear when comparing subs on a medium to large sized stage there is a big deep full difference between 15" subs and 18" subs (the latter really dominates). Yet, when it comes to bass speakers, it's not unusual to find bass players preferring, for example, six to eight 10" speakers in a bass cabinet over two 15" bass speakers in a similar size cabinet. Fender, for example, no longer manufactures it's 215 (two 15s") anymore but continues the same bass cabinet line for it's 610 and 810 models (six and eight 10" speakers, respectively).
What do multiple smaller bass speakers offer over 1-2 larger (15 or 18") bass speakers?
Thanks!
Response time and power-to-surface area, mostly. A 15" or 18" speaker is a lot of mass for one voice coil to move. Remember that, to maintain a constant acceleration, the required power increases on the
square of mass; if the cone is twice as heavy, you need four times the power to drive it at the same amplitude (and that's after all inefficiencies, which in a magnetic inductor like a speaker's voice coil are considerable). All other things being equal, a 15" cone is a little more than twice the surface area of a 10" cone (706 sq in vs 314), so assuming that also translates to double the weight of the cone itself, to make it get up and dance you'd have to feed that speaker's voice coil over 4 times as much power as you would to get similar travel out of a 10.
Now, let's consider a 4x10 cabinet. Each 10 takes 1/4 of the power needed to push the 15 at a similar travel amplitude, but the 10 is only half the surface area; so, for the same power, you can push double the surface area (and thus move double the air) by divvying up the load. The net result, all other things being equal, is a 3dB increase in SPL for the same power. This is borne out by sensitivity ratings; the 15 will average significantly lower SPLs than the 10 across most of the response curve when given a 1W sine wave. Also remember the better response times; 10s are described as feeling "punchier", as they respond better to transient attacks, like in slapstyle. For this reason, they're common in the rigs of jazz and funk players, and even more traditional bassist genres like country, rock etc will use 10s for the efficiency gains.
The downside is bass response. Larger speakers get more dB per watt at low frequencies than smaller speakers do; it's why larger speakers are used for bass in the first place. 15s designed for bass guitar cabs, like the Eminence or Black Widow, will stay closer to their rated sensitivity at much lower frequencies than comparable 10s. The Eminence Legend CB15 has a "shoulder" where it starts bottoming out around 45Hz; the comparable Legend BP102 10" has a similar shoulder much higher, all the way up at 100 Hz. However, it's not all about the fundamental; the 10s will be better at reproducing the higher harmonics making up the bass's tone. From the same response curves, the CB15 starts a falloff around 3kHz that looks like the stock ticker from October 1929; above 5kHz, the response curve looks like noise. The BP102, on the other hand, maintains near-peak sensitivity through 5kHz before starting a gentler falloff, and it remains much more sensitive to higher frequencies all the way to the upper bound of human hearing.
OBM is quite right, however, that cabinet manufacturers are beginning to spend more time tuning the cabinets they load the drivers into; the result is that the 12" "compromise" driver, which trades about 1kHz of peak high-end sensitivity range vs a 10 for an extra 35Hz or so of bass response (and gentler falloff than the 10 as it bottoms out) is becoming popular, as with proper cabinet tuning it's as loud as a 15, with high-end response approaching 10s, for considerably smaller size and less weight than either 1 15 or 4 10s.
