can a speaker with just 4.5 inch drivers reach 20 hz or even 30 hz or 40 hz? the speaker has four 4.5 inch drivers and is rather big. about 5 foot high. can someone pls inform me. i cant seem to find any info on the internet about this. thanks.

There are some speaker systems which can reach that low with small drivers, but they are pretty unusual. You either need a very carefully designed enclosure or some pretty exotic drivers...

Look up the "straight8" or "whamodyne" (2 M's ?) speakers on the net for an interesting read. There are some better examples but I can't think of them right now.

Hi theshade,

All loudspeakers obey the laws of physics when it comes to bass extension and bass output. I'll simplify this to keep it clear. How low a frequency a loudpspeaker will reach is a function of total enclosure size, driver diameter, the "motor" characteristics (voice-coil, magnet) and sensitivity/efficiency. A designer can manipulate all of these variables to achieve a particular end.

For example, you could use two smaller 6.5-inch woofers in a large enclosure, like the Axiom M80ti, and achieve deep bass extension to below 30 Hz. If you make the enclosure smaller, you lose some deep bass extension and overall output. If you are willing to trade off sensitivity, it's possible (up to a point) to get deeper bass extension by using a smaller woofer with extremely long excursion except you would have to use a very large amplifier to power it. Think of the woofer as a reciprocating motor (air pump). If you use a smaller enclosure and force a smaller woofer with long excursion to "work" much harder, which will require more energy--a big amplifier--then you can get more bass output, but you will also limit how loud the speaker will play, because the woofer is already "working" hard, so it will have limited dynamics.

As you can see, it's very complicated, and my explanation is greatly simplified. Also, every driver has a measurable "free-air resonance" frequency, and that rises once you put it inside an enclosure. The driver will not produce significant output below its resonant frequency. To cite your example, with a very large enclosure, it might be possible using four 4.5-inch drivers, to achieve output in the 30 Hz region, but there would be significant trade-offs in other areas of performance.

Regards,