Thanks!!

LX-60 has:
*9mm linear excursion vs 7mm of the G40, hence greater SPL capability
*LX-60 works in SBB4 alignment because of lower Fs and lower Qts, it's better damped with no sharp knees in the group delay (better transient response)

G40 has:
*0.5db less power compression at 700W
*Dual Spiders and what Beyma calls an improved motor structure

Both drivers will work though, but I'd prefer the LX-60. In a pro sound application the more rugged G40 with dual spiders will withstand high volume levels for longer, but for a home application the LX-60 has more benefits. I'd expect it's probably a little cheaper too, if the G40 is a new model.

Overhang and top plate thickness of both models are actually the same though according to Beyma, so the quoted 9mm xmax of the LX-60 to the G40's quoted 7mm xmax should possibly not be used as a comparison; they should have the same linear excursion. The better transient response capability is what really makes me choose the LX-60. To me, having tight transient response is very important.

Regarding cabinets? Can I build all of the drivers in one cabinet? Will the 18" back-air(air backwave) affect the 12" and the horns?

thanks adrian, I'll keep you posted.

Sounds good then. The G40 isn't bad or anything, in fact it will still work quite well. The LX60 isn't all that different, but this was my preferance for the reasons given. I'm sure you'll be happy with the G40 though. Its similar to a lot of other high end 18" drivers.

I'd have the 18" in a seperate enclosure from the rest - a subwoofer. I'm assuming that the 12" can reach to below 100Hz (I have not checked myself), below 70Hz would be the best. The G40 18" needs over 300L box volume so you can't really have the 12" and HF horn in the same cab. In any case, I'd rather have the 18" seperately anyway. The 12" driver your using needs to reach at least 70Hz. Have the 12" and HF horn in the same box with the 12" on the bottom, and HF horn on the top. The 18" goes in another box. This will also let you place the subwoofers each in a room corner, and have the 2-way main speakers out in front which is a good setup.

I don't know how much the Beyma's are worth, in fact I live in Australia so its pretty hard for me to give a US$ price.

> Will the 18" back-air(air backwave) affect the 12" and the horns?

If they were in the same cab, you're right, the G40 and 12G320 each need to be in their own seperate enclosures. The HF horn can be in the same compartment though.

"CP650ti (2" exit driver), CP25 and a TD400 horn"

What is the CP25? Is it a supertweeter or something that doesn't require a horn? If it is, then I'd have the 12" driver on the bottom, HF horn in the middle and supertweeter at the top.

Have you made sure that your tweeter horns provide the correct response curve and such.

Adrian

the CP-25 is a supertweeter with a small horn just like the JBL 2404H bi-radial horn if you are familiar with JBL. It has flat freq. resp upto 15khz after which it goes down a few decibel to 20khz. I thought and assume this would be just a good match with the 2" exit driver CP650ti which rolls-off sharply after 10khz.

sorry but I still have to ask regarding port size and length. I still do not understand how I am going to measure my port length and size for my 18G40 driver in a 320l enclosure. does it have a formula? I can't understand how to read the port sizes and length in WINISD and Boxplot shareware software.

thanks!!

The CP25 looks OK. It's a 100x60 deg horn though, I would prefer to match the dispersion to be the same as the TD400 horn your also using, which is 90x40deg. Even then though the directivity varies with frequency so they won't be exactly matched. Actually at the 10Khz crossover point the DI between the two subsystems are definitely not matched. That vertical dispersion is really a bit large in relation to the other subsystems - more lobing error will result especially up this high. It's a shame Beyma don't publish much about vertical on and off axis response for the CP25.

I couldn't find the CP650Ti comp driver response curves on the TD400 horn on the Beyma site either. In fact that compression driver model number did not even seem to be listed.

In terms of distortion, if you compare to the JBL's curves they are clearly a lot lower, though thats not to say the Beyma's are bad. I've never used Beyma before so again, I can't offer opinion on how they will sound subjectively, only design advice to make it good academically.

About the port length's, yes, there are formulas. Boxplot and WinISD should also give you port sizes too. I'll load up the 18G40 later and get you the port requirements if you want me to. Here is my 300L vented box tuned at 25Hz that I built for my 18" driver about one and a half years back:

I'd still prefer a 1" exit compression driver on a horn with compensation to cover 1.6KHz to 16 or 18KHz rather than a supertweeter crossed at 10KHz. It's not worth it in my opinion, too much polar response error and parallax is introduced for the small gain in HF bandwidth which you don't need.

Adrian