How could smaller speakers be more sensitive than larger speakers?

[Kreshna]

I was a little bit curious about the specs of JBL titanium series (JBL 120Ti, JBL 4412, JBL L80T, etc), and what I found is pretty surprising. According to the manual, the JBL 4410 has a sensitivity rating of 91 dB / 1 watt (2.83 V) / 1 meter, while JBL 4412 has sensitivity rating of 90 dB / 1 watt (2.83 V) / 1 meter. What surprises me is that JBL 4412 is the (sligthly) larger between the two; the 4412 uses 12" woofer, while the 4410 only uses 10" woofer.

So, how could it be possible? I thought larger speakers should be more sensitive than smaller speakers, well at least according to Hoffman's Iron Law. So how could the smaller 4410 be more sensitive than the larger 4412?

 

[Chris Brown]

The cabinet can have lots of impact on the efficiency. The 4410 and 4412 are both ported designs, and generally in that case, the bigger the cabinet is compared to the woofer, the more efficiency you will have. With both having nearly the same size cabinet, it's more cabinet space relative to the 10" woofer than it is relative to the 12" woofer, thus the 10" model is more efficient.

Then take the L100T into account. Similar driver compliment (except obviously for the 2214H instead of the 128H), but as a result of the larger cabinet relative to the 12" woofer, efficiency of the L100T is back up to 91dB vs 90dB for the 4412.

 

[Kreshna]

The cabinet can have lots of impact on the efficiency. The 4410 and 4412 are both ported designs, and generally in that case, the bigger the cabinet is compared to the woofer, the more efficiency you will have. With both having nearly the same size cabinet, it's more cabinet space relative to the 10" woofer than it is relative to the 12" woofer, thus the 10" model is more efficient.

Then take the L100T into account. Similar driver compliment (except obviously for the 2214H instead of the 128H), but as a result of the larger cabinet relative to the 12" woofer, efficiency of the L100T is back up to 91dB vs 90dB for the 4412.

Ah I see, thanks for the explanation.

I also notice that JBL 120Ti is actually less sensitive (89 dB / 1 watt / 1 meter) than JBL 4412 (90 dB / 1 watt / 1 meter), while the ratio between cabinet size to woofer size is about the same between the two speakers. Probably because JBL 120Ti has more complex crossover?

 

[Tom Brennan]

A small speaker can have high efficiency by trading depth of bass response (F3) for efficiency. For instance if you put a 6.5" Lowther driver in a small box you'd have very high efficiency but a very high F3. Note the Klipsch Heresy which has very high efficiency for a box it's size but also has a correspondingly high F3. Anyway you have to figure in the F3, not just box size and efficiency.

And be leery of manufacturer's claims of efficiency (and depth of bass). Some are very, shall we say, optimistic.

 

[Chris Brown]

I also notice that JBL 120Ti is actually less sensitive (89 dB / 1 watt / 1 meter) than JBL 4412 (90 dB / 1 watt / 1 meter), while the ratio between cabinet size to woofer size is about the same between the two speakers. Probably because JBL 120Ti has more complex crossover?

Many more factors at play. 4412, 4410, and L100T all use the exact same tweeter and mid-range (035Ti, 104H-2), and they all have the same Crossover frequencies (800Hz, 4500Hz), so it makes for an easier comparison. The 120Ti uses a different tweeter and mid (044Ti, 104H) and has different crossover frequencies (900Hz, 4000Hz).

All of the 104H mid-range drivers (including 104H-2, 104H-3) are very efficient, usually several dB more efficient than the tweeter or woofer. With the 120Ti crossover frequencies, it is putting less load on the efficient mid-range, and more load on the less-efficient woofer and tweeter. That would be my guess as to the reason for the slightly lower overall efficiency.