I have wanted to do a 3 way with a B&C 8PE21 and a B&C DE10 on a wave guide, along with a 15" woofer. I already have the DCX2496 and 3 T amps. If I went passive, I would do one of the 2 way designs presented. Question 1, what is the vertical dispersion of a SEOS 12? I am guessing 40 or 60 degrees. As a follow up, horizontal dispersion is 90 degrees, correct? Sanity check: Crossover frequency for 90 degree dispersion would be about 2.5 KHz to match the waveguide? Bonus Question: Besides the loss of pattern at a higher frequency, anything obvious I am giving up by going with an 8" mid? Thanks in advance. Doug
Loss of pattern means more room in the sound. If you want "faster" drivers for the midrange, use 2x 6" horizontally positioned. Then you will have the greatest amount of cooperation with the polars. I guess the question is what you are trying to accomplish that the 2 way doesn't and if you have to tools to "integrate" the 8" driver at both ends of its spectrum. What can go wrong? Lobe between woofer/midrange doesn't line up with listening area, lobe between midrange and SEOS doesn't line up for listening area, room response from the 8" makes the midrange too thick, small enclosure for 8" colors sound, makes total box bigger, shallow depth of 8" driver makes time alignment of the voice coils hard to balance with acceptable domestic design. One of the the primary goals of the Econowave was to get that controlled polar response as LOW in frequency as possible. The SEOS 12 allows horizontal pattern control down to about 1200Hz, as does a 12 or 2x 6" woofer/mid array. The suggested crossovers allow for a pretty big listening window in the vertical too as well as placing nulls in the vertical to minimize reflections from the floor and ceiling. If I was looking at a 3.5 way system, it would be to add a supertweeter above 15K to keep the polar response there at about 90°. The problem up that high is time aligning the drivers. The standard 2 way plus subwoofer(s) is absolute genious. That all being said, you never learn without trying. I think that the easiest way to learn is to try a proven two way design (in a box that would allow an upgrade later). Live with it for a while and identify things that you think could be better. Be careful here as your previous "HiFi" listening will color what you hear at first. Wait a couple of months and then think about is something HAD to be better, what that could be. For those that have never heard the midbase/lower midrange from a big driver, you are really missing something! There is simply too much garbage on the internet about "speed" and limitations of big drivers and way too little about the SOUND that we hear. The reviewers generally have a box of phrases that can be combined at will to keep advertisers happy. Most involve keeping MYTHS alive. Developing a taste for sound is a process that doesn't occur more quickly with a big box of parts.
rowuk, Thanks for the quick response. My delusion is more about keeping the "voice range" on a single driver. I also like a 3 way concept because it puts less demands on the tweeter, which is sometimes a good thing. It also generally has less IMD which may or may not be audible. Perceived speed IMHO has nothing to do with the diameter of the drivers. I do have the tools to do this with a measuring package and a Digital crossover that I am competent with. However, having a proven design would give me the best indication of what the format is capable of.. I think I will Start with one of the proven designs and experiment. Doug
Hi Doug, what is the "voice range"? Middle C between the bass and treble clefs is 256 Hz, C above the staff that is only sung sometimes, is 1024Hz. The overtone structure of the human voice and formants to make speech/singing intelligible is primarily below 1500Hz. I would be more worried about getting the "melody range" between 100 and 900Hz messed up by switching drivers. The main advantage here with the two way is pattern control and efficiency. The efficiency keeps the distortion far lower and the pattern control makes rooms work better because the frequency response is not destroyed by room effects as easily. I think the only way a 3 way would be better is to use a BIG horn from 100 to 1200Hz and then the SEOS 12" on top of that. You need a VERY understanding wife for a 100Hz horn............
The 2 way does look appealing. I can see that the 12" would have lower excursion at any given frequency compared to an 8". The 12" also has a minimum lobe with the SEOS Waveguide 12. So its a great match. I guess it really depends on the Compression driver, and how low it will go with low distortion. Since you are using the DE250 or clone that does 1200 hz comfortably, its not an issue. The voice range is considered to be 300 hz to 3 Khz, about the range that a telephone operates in. Like any other rule of thumb, I have seen instances where it works, and those it does not. 100 hz to 900 hz seems like an interesting target. Even if my wife was on board (she isn't) I can't find a place in the house to put a 100 Hz Horn. I would be interested in the 300 hz tetrex horn , but that's a toy for the large house set as well.