Test Beyma CP21/F
Copyright 2019 © Troels Gravesen
These Beyma CP21/F horn loaded tweeters seem a replica of the venerable
JBL 077/2405 tweeters - and they're only around 110 EUR, about one-fifth
of what I paid for my JBL 2405H. Time to take a closer look.
First of all, the finish of these tweeters is far away from the JBL
ancestors and to get the full potential we need to do a few
modifications. Read below.
Manufacturer's data here.
Insert a sharp knife gently below the cover ring and peel off gently!
Below we find four screws holding the horn.
The diaphragm doesn't look too smooth and the center plug seems pretty
rough too. But whatta we get for 110 €?
First thing we notice is the sharp edges of the horn mouth and we need
to smooth it with a file.
Turning around the horn we notice the "lips" forming the slot fit very
badly to the basic horn. There are huge gaps between the "lips" and the
horn throat they need to be filled with e.g. Superfix. I used a small
syringe and a large and short syringe needle to add the Superfix and did
the final smoothing with my little finger, the best tool for this job.
As can be seen we now have an overall smooth throat. This is about it,
and let's see what we've got.
Basic response the the two units received. Quite some difference I
should say.
What bothers me the most is the dip around 6-6.5 kHz. What happens here?
Above the frequency response promised by Beyma stretched to make almost
the same 60-110 dB range and 2k-20k.
Not quite what I found.
Response of the two tweeter after treatment. Now, does look better and
the dip is gone. I'm sure the poorly aligned horn parts are responsible
for this. As we for our application here, The Loudspeaker II, only need
the 10-20 kHz range, these tweeters look suitable, at least as good as
some of the other tweeters. The JBLs don't look much better albeit
having a much high sensitivity - but we need attenuation anyway.
Above my two JBL 2405H units.
Pretty good response in the 10-20 kHz range.
Above my two units JBL 077 tweeters. No baffle.