quick ballpark tweeter pad change ?

freddi

Member
Paid Member
2005-08-16 4:21 pm
I've got a P-Audio 12CXA coax with the schematic and L-pad below but in the little Karlson enclosure I'm using, it required about a minimum of +4dB treble boost on a Onkyo SR309 receiver to subjectively balance. I don't know if that boost is referenced to 20K or not as not in the spec sheet.

what might be done to get some rise like the control and not goof up the compression driver on the low end and not have Z drop too low on the top?

the receiver pooped out today - audio gone - lived 3 years - tried to reset but only ran a few minutes - might be a common problem as the complaint has been noted by others.

9Ps9Nss.jpg
 
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You can use this calculator to try different configurations.

It would of course be easier if you could measure it.

Best,

Erik

From this handy linked table and using your schematic, it would seem that decreasing the series R to 2R2 and increasing the parallel R to 19R woukd do the trick.

But...

Only the series R in your schematic matches the table.

So it would seem the l pad in your speaker also does some response shaping (I'm guessing the 4R is lowering the Q of the filter )

I haven't looked in depth, but perhaps it's not such a simple matter if the filter curve is to be preserved?

For that reason I'd leave the series R as it is, and increase the parallel R, maybe up to 15 or 19 ohms as the table suggests for the -6dB line (assuming an 8R tweeter), which should give you up to 3dB less attenuation.

Caveat: running the numbers through a calculator keeping the series R unchanged (if it allows this) should help confirm this (or show I know nothing hahahah)
 

freddi

Member
Paid Member
2005-08-16 4:21 pm
I really appreciate the input - that Onkyo's treble control referenced to 20KHz so don't know how much lift in the lower treble. Here's the very optimistic looking curve for the compression driver/treble "funnel" - even with a lot of on-axis acoustic-eq, - don't think it would have usable output to 30KHz (?)

RtYZJuk.jpg


Here's a discussion (Google translation to English) of the same coax with a different crossover
https://translate.google.com/transl...p=40689&hilit=12cxa#p40689&edit-text=&act=url

[IMGDEAD]http://i57.tinypic.com/ka2srd.jpg[/IMGDEAD]
 
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