Originally Posted by Martycool007
OP-can you tell us anything about how some of the 2" CD's have compared to these 1" CD's that you are testing? I am most curious about the Radian 950PB, (or 951PB 1.4"), the BMS4590, and maybe the JBL-2446? Is the main problem with using a 2" CD in a 2-way design, getting the 2" CD to extend upwards around 20khz? Are there any decent 2" CD's that will go up that high and also have the ability to crossover to a 15" woofer at say 700hz to 800hz?
I would personally like to see someone do a 3-way build using a 1" CD for the tweeter and then a 2" CD for the mid-range portion. I do, of course, realize that the crossover will be more complicated and could possibly sound worse due to the disadvantages of a 3-way versus a 2-way, but me personally, I would love to see some kind of 3-way build that uses something like a Radian 950PB for the mids, and an AE TD12x or TD15x, not sure which tweeter would be best, though.
I have the 2445s and the BMS4590. They are all excellent drivers. Midrange performance is truly amazing. For a low crossover, I would stick to around 600 Hz. Below that the woofer is outperforming the CD. Yes, there is some more control of directivity, but not much. Definitely not use the drivers as low as 300 Hz.
The main problem with a 2" CD is two-fold: like Penngray says, the size of the horn to get it working at 500 hz makes it impossible for the horn to control directivity up high. Well, you can still do it using a pinched throat horn, ala JBL, but it doesn't sound the best. So, the driver is beaming at 5 or 6 kHz and plus it is in breakup mode beyond that anyway. It's just a series of resonances taking it up to 15 kHz.
The range above 10 kHz doesn't have much music anyway. Just air and ambiance. But below 10 kHz there are vocal sibilants and other important sounds. I wouldn't ignore it. See this chart:
It gives the frequency range of each instrument. At the bottom, it shows what subjective quality each range has. And as you hover over the ranges, there is interesting info in the side boxes. It's more for recording engineers, but it might help diagnose problems when doing diy.
Regarding three way, I've seen LeCleach do it with the Iwata horn. Woofer, small Iwata, large Iwata on top. But the crossover up high is very hard to integrate with the mid horn. There is time delay and CTC distance. It WILL be a comb filtered response.
Personally, I've decided to stick with the SEOS-18 (or 24 if it becomes available). And the next step is obviously the Synergies, where all these issues will go away. The only question I have about those is the smoothness of response.
People make a big deal about constant directivity and such. But what we are really most sensitive to is resonances. If you have a bumpy response, it doesn't sound nice. The response should be smooth. Some deviation from flat is ok, but it should be smooth. To get this smooth response, there are a number of issues to deal with. Baffle step, floor bounce, crossover, breakup, and more. Read Toole.