Frequency graph question
Pictured is the factory frequency response for a dayton rs150p-8a 6" woofer. The woofer's range is 45 - 10,000Hz. The frequency response stays pretty flat to 10kHz at zero (0) degrees. However, at roughly 2,000-2,100Hz the different offsets start to reallyseparate.
Do I want my crossover point to be at /slightly below this offset break-up point? I saw in one of 123toids videos he opted to crossover at/slightly below the "offset break up" of the woofer he used.
If I cross over higher than the "offset breakup" point on my mentioned woofer, say 3,000 or 4,000Hz, what will happen? Will the speaker only sound great head on (0 degrees) and horrible at 10, 15, 30, etc degrees?
This is an excellent question. I wish more people would ask it. Some of this depends on the slope of the crossovers, but I will answer this as a generality. Typically you will want to cross this speaker over by 2500khz. The main reason is off-axis response. If you were to crossover much higher you would have to deal with a phenomenon called "beaming." This basically means the speaker will start to play those sounds in a beam or straight toward the listener. This is bad for a few reasons, one the speaker will have really bad off axis response which will not sound good, except in the sweet spot. However, even then, it could be problematic, since a lot of the sound we hear is actually reflected off surfaces. So you typically will want to crossover either slightly before or slightly after that area. I say slightly after, due to the fact, the tweeter may help fill in that are, depending on your crossover.
P.S. beaming would only occur from around 2khz to 3 or 4Khz respectively.
Personally I like to use winPCD to analyse off axis problems, you can tell the program the positions on the baffle and give it the crossovers, frequency response plots and impedance plots, and it will give you a polar response! I loved it when designing that area. For everything else I like to use XSim to visualise the crossover and then WinISD with VirtuixCAD 2.0 for everything else.
Going along with what 123 toid, I would go with a lower crossover and a larger tweeter, I used a nd25fa, a crossover order of 3 gave me what I need. The higher the crossover order the more complex and expensive the crossover yet you can get it down to those lower crossover frequencies. Just make sure you always compare them with the limits of the tweeter!