Hi, Everyone, In an earlier thread (see http://www.talkbass.com/forum/showthread.php?threadid=8346&pagenumber=2), a question came up about how certain speakers seem to project (throw) bass out into a large room better than others. I promised to do some reading and see if I could find out more. I also asked people to contribute ideas and observations, but did not get much response. However, I think I can summarize a few leading ideas: __ 1. Member "Spacegoat" (Talkbass, 12/9/00) said: "Maybe it's because 10's produce more mid freqs than 15s or 18s and thus appear to be louder at the same distance near field." I think this is a good point: 10's more easily produce harmonics than 15's or 18's, which may make them seem louder - especially when we take Fletcher-Munson (hearing sensitivity) curves into account. Since electric bass signals are rarely without at least some harmonic content, I agree that this could be a factor. __ 2. I note that most bassists tend to put the bigger speakers on the very bottom (next to the floor), whereas smaller speakers (e.g., 10") are often placed up higher, away from the floor, and closer to ear level so that higher frequencies can be heard. Two related points: ___ (a) the sound from the big speaker near the floor will be more readily augmented by reflections from the floor boundary - (see Comment 4 about "virtual horn"); ___ (b) the smaller speaker placed higher will be more readily heard by the player because of simple proximity to the ears (and, referring to Comment 1 above, they more readily emit harmonic content). I have noticed this with my own stack. The 18" bottom on the floor does not seem to be very audible when I stand near it (though I can certainly "feel" it), whereas the 2x10 on top is what I'm hearing more readily on stage. __ 3. For a given near-field sound pressure level (SPL), larger diaphragm speakers generate more _acoustic_ power than smaller ones ,*. I would think that the higher power radiated from larger speakers interacts more readily with room boundaries to produce higher SPLs farther out. __ 4. In effect, room boundaries act like a horn at very low frequencies; consequently the effective "mouth" of the horn may actually be well beyond the speaker and perhaps even the stage! In this situation, the speaker - and even the bassist - would be located inside this "virtual horn". The SPLs at points inside a horn may be less than those of points at or beyond its mouth, for certain frequencies. __ 5. I have not analyzed the radiation of 4x10 vs. 1x18 mathematically (can you say "Bessel Functions"?); however, the 4x10 array is likely to be somewhat more directional in the near field than the 1x18, at a given low frequency. If so, perhaps the near field SPL is higher for the 4x10, without augmentation by lateral reflections; whereas, since the 1x18 is more omnidirectional, reflections from nearby boundaries augment the SPL in the far field. __ 6. Folded horns, in particular, tend to couple with the room boundaries to extend the effective horn out into the room. A pertinent post on TalkBass (December 29, 2000), by member ROCKBOBMEL: "Stay away from the Acoustic 301 Cabinet. I had the 360 with the 301 cab. It is a great sounding rig but, the problem with 18s, and especially the folded horn 18 is the sound does not develop until about 15-20 feet out (past where you stand). You can't hear the notes well enough, so you turn up the deep bass and it is killing people in the back of the room. You probably can get one for cheap, but only good for stadiums (like John Paul Jones played)." In conclusion, to date I have not found any strong arguments to refute the claim that bass from certain types of speakers seems to carry (throw) better than bass from other types. It is really interesting ("Fascinating," as Mr. Spock would say). I think I mentioned earlier that I read that Ampeg's big SVT 810 cabinet started to win players over because it sounded stronger in the music dealers' showrooms than the existing folded horn cabinets; however the folded horns tended to excel in their "throw" of bass in bigger spaces. I'd be interested in comments anyone might have about this. - Mike *References: __  "Low-Frequency Loudspeaker Assessment by Nearfield Sound-Pressure Measurement", by D.B. Keele, Jr., Journal of the Audio Engineering Society (April 1974). __  "Some Aspects of the Self and Mutual Radiation Impedance Concept with Respect to Loudspeakers", by Oluf Jacobsen, Journal of the Audio Engineering Society (March 1976).