Hello All, Apparently something in the "Speaker Dispersion" topic triggered a move to the "Manufacturers' and Retailers' Forum." Given the relevance of the material I provided to this forum, I'm starting a new thread with only the free information I provided in the other one. Speaker directivity is the bane of a consistent guitar sound. That much is generally recognized. However, there are several audio myths that continually get repeated, and they should be be corrected: 1. High frequencies come from the center of a cone speaker, and that's why they beam. Nope. If you could actually get the high frequencies to be radiated by the "center" of the speaker - say the dust cap - you'd find them being radiated over a greater angle, not a smaller one. A number of past cone speaker designs actually had compliance elements built into the cone in an attempt to create this exact scenario: the size of the cone effectively getting smaller at higher frequencies. They didn't work particularly well. 2. Placing an obstruction in front of the center of the cone "blocks" these "beaming" frequencies and makes the speaker's directivity (the word "dispersion" does not actually apply to radiation pattern) broader. Nope again. The "blocker" will indeed change the on-axis response and directivity of the speaker, but the effect is not consistent or necessarily useful. The directivity will actually be made narrower at some frequencies. The mechanisms whereby an obstruction placed in front of a speaker changes its response and directivity are complex and counterintuitive. "Blockage" has nothing to do with it, however. An obstruction will reflect sound back towards the cone, which will "re-reflect" the sound forward. The time it takes sound to make this extra trip means that the reflected sound will be delayed by some amount compared to sound that didn't make the extra trip. The response of the combined sound - slightly delayed plus undelayed - will contain interference ("comb filters"). The "phasiness" some folks describe when they install beam blockers is due to these comb filters. A portion of the outgoing sound will diffract around the obstruction. This sound is also delayed and will cause an additional set of comb filters. The diffracted sound also has a different radiation pattern from that of the speaker, since it comes from the edge of a small disc. Taken by itself, the diffracted radiation has a strong beam directly in front of the disc. Combined with the other radiation (direct and reflected), the radiation pattern will vary widely with frequency - even more than the pattern of the speaker with no blockage. If you find these effects desirable - as a number of players apparently do - then there is nothing wrong with the use of "blockers," but they don't cause the directitivity changes their makers attribute to them. If you want to alter the directivity of a guitar speaker in a favorable and frequency-consistent way, I've developed a means to accomplish that, and it can easily be tried by any reasonably competent DIY type. It is outlined in the next post. I've used this method on my tube amps, and it works beautifully.