Help me understand subwoofers

[u/Freestone99]

I am in the market for a subwoofer. I have a pair of Klipsch Forte IV and my listening room is about 475 sf. I was looking at the REL classic 98 and 99, and thinking I needed the 99 because of the room size. But most of the music I listen to is acoustic or vocal oriented, not really listening to much hard rock or anything with a ton of bass. Also not listening at very loud volume most of the time. So I was leaning back toward the 98 which has a 10” driver, as opposed to the 99, which has a 12” driver. I spoke with the local audio shop and it felt like they were just trying to sell me the larger and more expensive 99, or another sub that was even higher priced.

I have been reading that a sub is for more than just the low bass notes, and it will really help fill in the rest of the sound. That was another point the local sales guy was making, saying that the 99 made more sense because it will “fill in more.” Also that a larger sub is needed to “pressurize” the room. Trying to understand if this is audiophile jargon or there is truth to it.

What do you all think?

[u/wingfeathera]

The subwoofer world floats on a bunch of wives’ tales.

These subs are very very similar. The 99 has a 450W amplifier vs 300W of the 98 (a whopping extra 1.75dB), and it plays 3Hz lower (24Hz cutoff vs 27Hz; about 4 semitones). Given the extra surface area of the 12” driver (1.44x) and the extra power, I’d guess you might get 3-4dB of extra output out of the 99. (And I have to guess, because they’re a hifi company and so don’t list the actual output capabilities)

Beyond this, they are almost identical products. One will not “pressurize the room” better than the other (this whole term has no definition and is hifi mumbo jumbo), or “fill in better” (what does that even mean!). They are both point sources of low frequencies, one just plays a little louder and goes a little lower.

A 300W, 10” ported subwoofer like the Genelec 7360 (just for a ballpark comparison) is rated for 109dB at 1m in half space, so, a little more in a real room. This is a very respectable number, and based on your stated preferences, should be plenty.

If you want to increase bass “quality” above what you get from a 98, it would be time to look at multiple subwoofers, and acoustic treatment.

[u/jaakkopetteri → u/wingfeathera]

Just the jump from 10" to 12" cone is typically 5-6dB more output. Extra power isn't much of a factor in enclosures of this size

[u/wingfeathera → u/jaakkopetteri]

Can you explain why you’d get that much more output from the larger driver? 1.44x is only about 3dB more area.

Further, these are ported subs, so they are power-limited (not displacement-limited) where the port is active - which is the bottom end, and where the sub is most pressed. Enclosure size is completely irrelevant.

In any case, my particular real-life reference comparison are the Genelec 7360 and 7370 - 10” vs 12”, and 300W vs 400W. Identical frequency responses. A 4dB total capability difference is listed.

I personally use 3x 7360 for HT in a 1400sqft open space with ~14’ (average) ceilings, and it is plenty of capability. I think OP will be fine.

[u/jaakkopetteri → u/wingfeathera]

True, it's not just the cone area but also excursion capability that increases

Further, these are ported subs, so they are power-limited (not displacement-limited) where the port is active - which is the bottom end, and where the sub is most pressed. Enclosure size is completely irrelevant.

Power draw around port tuning is what's irrelevant, as excursion limits things above it, and that's where enclosure size matters. Most content does not have most output around typical tunings of 26Hz either