Help me understand Bastanis wiring

[mrthieme]

I am interested in building speakers based on the Bastanis Prometheus. They have no crossover to speak of, and I don't understand what keeps the bass info from the tweeter, which is wired directly from the other driver( Eminence Beta 12 cx coaxial with Beyma tweeter). Here's the schematic http://www.bastanis.com/diy/prometheus+mkii+build.htm
Eminence calls for a 3.5k crossover with the coax and their own suggested tweeter. Thanks

 

[joensd]

Hi,
what makes you think it´s the 12CX from Eminence?
Looking at the datasheets and the FR in particular I´d guess it´s more like the Delta12LF. (at least for the Prometheus MAXX which has a paper dustcap)

don't understand what keeps the bass info from the tweeter, which is wired directly from the other driver

There´s cap in series with the tweeter, isn´t there?

greets & let us know how it turns out

PS.: I reckon you did see their forum:
http://www.audioasylum.com/forums/bastanis/bbs.html

 

[mrthieme]

Thanks, I thought I had read somewhere it was a beta 12 cx but maybe you are right and I'm reading the wrong specs. There is a cap, does that act as a high pass filter or simply +/- db at the tweeter depending on cap value?

 

[joensd]

I had read somewhere it was a beta 12 cx

Read that too, but still haven´t seen a proof for it.
(as for my assumption likewise)
This might be of interest:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=19883&highlight=

The cap forms a 6dB-highpass filter.

greets

 

[mrthieme]

The driver is always referred to as a wideband, I wonder if the delta qualifies for that description. I know it is a customized application but it must start as one of their standard drivers.

 

[joensd]

Look at the datasheets of the 12CX and Delta12LF.
There is a jump of almost 10dB at ~800Hz in the fr of the CX
whereas the Delta is kinda smooth until 2k.
Then comes a little hump that should be negligible (or easy to tame with a 6dB-high-pass).

If you want to further investigate I could send you an article about the Prometheus MAXX with fr-responses of the fullrangers used (the fr´s look very similar to the Delta12LF here as well) and everything else.

greets

 

[mrthieme]

Hi Jens, thanks for all the info, one more question, what does the resistor do if it's simply soldered across the woofer terminals?

 

[joensd]

The 12ohm resistors damp the impedance peak at 45Hz.
Will scan in the graphs later and put them up.

 

[joensd]

To avoid copyright issues I´m gonna send you a PM.