Small or large sub for music

@mapman wrote:

"Also lower bass frequencies take exponentially more power to produce flat response so you better have plenty of good clean amp power in those subs too to carry the load. The more the better. Not enough power in reserve is perhaps the most common cause of bad sounding bass."

Well, it depends on the specifics. Some subs rely on aggressive EQ to go deep. The DEBRA and Swarm systems do not.

The DEBRA and Swarm systems use individual subwoofer modules whose native response is the approximate inverse of typical room gain from boundary reinforcement (which is +3 dB per octave south of 100 Hz, according to Martin Colloms). The Debra and Swarm subs have a native response that falls at about 3 dB per octave from 80 Hz down to 20 Hz. This is a more gentle rolloff that you can get from an unequalized sealed box.

In many smaller rooms this ends up giving you more low end than you need. One option is to invert the polarity of one of the four subs. Doing so often further improves the in-room bass smoothness in my experience. And since small rooms are the ones that usually have the most room for improvement in the bass region, this works out well. This is not the only trick the DEBRA and Swarm systems have up their sleeves - they are highly adjustable in the acoustic domain, and still have EQ available in their amplifier if needed.

One advantage of not relying on power-hungry EQ to go deep is, we’ve never had an amplifier fail due to being over-driven. And we’ve only had one woofer failure in twelve years.  That's less than 1%, and it was an 8" woofer (which we no longer use) in an early version of the Swarm.

Duke

Swarm designer

@wolf_garcia wrote:

"Bass frequencies absolutely require MUCH more power than treble or mids, to state otherwise is ridiculous."

The musical spectrum normally has more energy at low frequencies than at mid and high frequencies, with 400 Hz being the approximate midpoint for power distribution.

But if a speaker is "flat" down to 20 Hz, then by definition that means it requires the same amount of power to reach a given SPL at 20 Hz as it does elsewhere in the spectrum.

The reason a subwoofer might need a 500 watt amp to keep up with speakers that only need 50 watts is, the subwoofer is perhaps 10 dB less efficient than the main speakers. The way to get deep bass extension in a small box is to trade off efficiency (or to equalize, which is another way of doing the same thing). If the subwoofer box was 10 times larger, its efficiency would be 10 dB higher (perhaps matching that of the main speakers). But it’s more practical to build a 500 watt amp into a small sub than to have a much more efficient large sub.

Duke

@wolf_garcia wrote: "I’ve been in the actual music biz for over 5 decades...back when we used Altec A7s (extremely efficient) we typically ran maybe 200 watts into the bass speakers and 50 to 100 into the horns to make things balanced. Now I use 1500 watt powered bass systems, with maybe 350 watts per side for full range main speakers. Look at meters for output on home gear and you get the story...bass frequencies take up a lot of juice, even with efficient speakers...they simply do."

I think I see where our disconnect lies. I think you and I are mis-communicating.

You’re saying that you have observed amplifying (or reproducing) bass takes more power than reproducing the rest of the spectrum, and I’ve been saying that if a speaker has a flat frequency response, by definition the same power input produces the same SPL output up and down the spectrum (including in the bass region).

I think we are both right. What we are missing is, equal-loudness curves. I think they will explain why the needle jumps on the drum hits.

In order for the fundamental of the kick (ballpark 50 Hz) to be perceived as being as loud as the electric guitars, its actual SPL must be MUCH higher, like about 20 dB higher!

That 20 dB peak for the kickdrum’s fundamental would call for a 100-fold increase in power over what the guitar needs (assuming the speaker’s efficiency is the same at 50 Hz as in the mids and low treble). In other words, the kick must be LOUD for its fundamental to come through with authority!  THAT is why the needles jump!

My numbers may be off a bit - the kick’s fundamental is probably not as loud as the guitars - but I think the principle is valid, and I think it explains the apparent discrepancy between what you and I have been saying.

Duke