Vintage EPI Frequency Response

[Culpeper]

Back in 1973, new EPI 100's were shipped with paper Bruel & Kjaer graphs showing each speakers unique response .

RE the tweeters response ; both of my graphs show 5db deep holes, centered at @ 14K ( & more than 1/2 an octave wide )
- 1.5K to 10K is pretty flat ( at +/- 2db ) .

I could take a pic ( & post the results ) / though I'm ensure if I want to participate in unraveling a legend .

Perhaps it's worthwhile reminding people that Dr. Geddes focuses on the response from 1K to 10K ( for HF ).

That's torture...

 

[EarlK]

That's torture...

Here ya go! ( as I described a "way-back-when" )

 

[Culpeper]

What is Dr. Geddes relationship with the EPI 100?

 

[EarlK]

What is Dr. Geddes relationship with the EPI 100?

None ( as far as I know ).

My ( very off-hand oblique reference ) was made because in the past the good Doctor has made mention that he considers 1K to 10K a critical area to "get right" ( FR wise & Dispersion wise > he does use waveguides to control dispersion ). He prioritizes this area in his own designs.
- Probably shouldn't have mentioned this in the first place .

 

[Culpeper]

I think it was relevant. Thanks.

 

[Pete B]

Here ya go! ( as I described a "way-back-when" )

Thanks for posting this, I've not seen many measurements and it is good to see what a new, properly functioning EPI does.
This actually looks very good, the tweeter level steps down, probably because that is
what provides the best overall balance, in fact it might still be a bit bright. It is very
likely that the issue at 14 KHz is caused by diffraction and if the measurement had been
spatially averaged around the listening axis that it would average out.
I'm really pleased to see this, the tweeter looks better than the new aluminum version.
Are your tweeters masonite or plastic front?

 

[Pete B]

Here is an EPI 110 on axis and woofer nearfield response. IIRC, the 110 is very similar to the 100. Not sure about the 60 though.

It is nice to see that this agrees fairly well with the new curve, but is smoothed to 1/6 oct,
tweeter level is down a few dB, is very smooth with a dip at 15K ish.

 

[EarlK]

Thanks for posting this, I've not seen many measurements and it is good to see what a new, properly functioning EPI does.
This actually looks very good, the tweeter level steps down, probably because that is
what provides the best overall balance, in fact it might still be a bit bright. It is very
likely that the issue at 14 KHz is caused by diffraction and if the measurement had been
spatially averaged around the listening axis that it would average out.
I'm really pleased to see this, the tweeter looks better than the new aluminum version.
Are your tweeters masonite or plastic front?

They are the older masonite front.

 

[Culpeper]

The dip between 10k and 20k look similar to Mark's for the Human tweeter. The black line is the Human tweeter.

 

[Pete B]

Mark's plot of the Human tweeter is not what I'd call similar, rather it is -3dB at 7K well
into the audible passband and the max depth is about 7 dB. EarlK's factory plot is flat
to 10K with about a 5 dB dip at 14K, the shape suggests a diffraction issue whereas
Mark's does not look like diffraction.

 

[Culpeper]

Is it the tweeter itself causing the diffraction with the EPI.