Tweeter design change from 5 to 8 Ohm

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claude04444

Member
Joined 2019
#1
Hi

I am going to build a speaker designed by Paul Kittinger called "canTiLena".
I finally purchased the scanspeak speakers, takes a while to find $700 disposable funds.

Any how this design is over 10 years old and I cannot buy the original specified ribbon tweeter for it ( Fountek NeoCd1.0 1.5", Fountek does now make a new model of this tweeter (Fountek RD1.0 Ribbon). The problem is the old model was 5 ohm and the new one is 8 ohm.

Which leaves me at a fork in the design road

1: ignore the 3 ohm difference in the tweeters
2: modify the crossover resistor to adjust from 5 to 8 ohms
3: find a similar Tweeter brand that is 4 or 5 ohm.

My electronics knowledge is just enough to be dangerous, so I really would not know how to recalculate the resistors, maybe someone here could help.

Thanks in advance for your advise.
 
#2
The crossover tweeter portion looks like this

C4 C5 R3
+ in------------| 3.3 uF------------------| 5.6 uF----------- \/\/\/ -------------------------------
| 12.5 ohms
| Tweeter
| -----------------
L4 0.2 mH/0.2 ohms |
| |
r2 2.5 ohms |
| |
- in ---------------------------------------------------------------------------------
 
#3
The resistor in the original is there to balance the level of sound from the tweeter with that of the mid, so you can't just arbitrarily change it without affecting that balance. It might be better to replace it with an L pad, which will maintain the impedance load for the crossover, yet can be tweaked for the new tweeter. Do you have links to the data sheets for both the old & new tweeters?

I found the schematic here, but no parts values on it: forum.vegalab.ru
 
#8
Good news! I was able to purchase theold tweeter from Falcon Acoustics in the UK, the price including shipping was $146. So $40 more than Parts Express (or Madisound) old price. So I will not have to mess around with crossover.
The Morel MSM 55 is still readily available from Parts Express (or Madisound) so no other issues with getting other parts.

I intend to modify the cabinet slightly, for simplicity making a flat top (versus a arched), the interior inch^3 would remain the same as well as width and depth
I will finish the exterior cabinet with a laminate, I have used tons of this stuff over the years, it is easy to use (when you have the tools ), cheap and has so many finish options. Plus I’m a lousy varnisher.


Thank you again so much for your advice, it kept me on the right path
 
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