B&C DE120-8 Replacement tweeter for Klipsch K77

[nre_admin]

I received the tweeter assembly below for measurements.  It's a B&C DE120-8 with an Aluminum horn flare fabricated by Dave Ault. The flare is two pieces bolted together with Allen hd machine screws.  It's pretty stout, a hog-out from either thick plate or bar stock.





Here's a side by side with the sad little EV T35.  The Klipschorn, LaScala and Belle used the EV T35 for decades until it was NLA from EV.  Klipsch, rather than designing or sourcing a resepctable tweeter, decided to replicate the Avedon unit. 



 

 

[nre_admin]

Nearfield measurements were taken as shown in the setup below.  The mic and baffle, once spotted, were not moved during all the measurements taken, the power amplifier (Crown D-75) was set and not touched.  Response plots were made using CLIO 12 at a sampling rate of 192kHz.

T35



B&C with horn flare assy



The B&C website has the datasheet for the DE120 mounted to a B&C horn.  Here's the published plot from the data sheet.



Here's the no-net measured response of the B&C with the horn flare, similar to the factory response.  There's a peak in the response around 16.5kHz.

[nre_admin]

First iteration of the network used on the both tweeter assemblies.



Here's the measured response on the B&C assy, the net produces an 18dB/octave slope starting around 8kHz.  For the Klipschorn, the presumed mid-HF crossover is about 6kHz.



Here's the same set of measurements with the T35 and its net response superimposed.  Under identical conditions the B&C assy has higher sensitivity thus requiring either padding of the output or turning the wick up on the mid horn output.

[nre_admin]

Here's mods to the network shown above.  The Blue response is the original with C1 set to 1.5uF. 



And corresponding responses of the B&C unit.  The mods maintain the 18db/oct attenuation slope.

[nre_admin]

Impedance, suspended, of the B&C horn assy

[nre_admin]

B&C Impedance comparison to the T35.



 

[Deang]

Nice.

Looks like the 1.5uF will work just fine. Did you receive my email concerning Mike's trap for the peak?

200uh + 8 ohm + .47uf

Looks like if the driver is padded down 3dB, the peak is probably easy enough to live with.

[nre_admin]

Couple of plots showing effect of a series LCR on the network response.  Lowering the magnitude of L2 pushes the notch a bit higher in this case 15.6kHz to 18.9kHz.



 

[nre_admin]

The LCR knocks the resonance down a bit from the net response with no LCR.   

 

[mboxler]

Picked up a pair of used Crites CT-120's this morning, and was interested in the how it compared to the SMAHL.  SMAHL in RED, CT-120 in GREEN.  Both hung off a 6khz third order Butterworth filter.

The 16khz spike is less pronounced on the CT-120.  The subsequent roll off is much less.

Mike

[DaveA]

Picked up a pair of used Crites CT-120's this morning, and was interested in the how it compared to the SMAHL.  SMAHL in RED, CT-120 in GREEN.  Both hung off a 6khz third order Butterworth filter.

The 16khz spike is less pronounced on the CT-120.  The subsequent roll off is much less.

Mike

  Hi Mike,
  Curious to know if you tested the two in free air. A part of the equation here is the tunnel the CT-120 goes through which the SMAHL does not.

[mboxler]

If I understand your question, my Khorns have the Z-Bracket K77M's.  I had a pair of CT-125's with
Z-Bracket's so I just transferred those to the CT-120's.  The CT-120 horns are flush with the front of the top hat baffle.

Mike

[DaveA]

That is what I was looking for. Thanks