Suitcase with piezo tweeters

[Electroharmony]

Getting ready to mod... Any thoughts on why I shouldn't?

[Rob A]

Having done it, it's incredibly excellent. I can't think of any drawbacks.

[dnarkosis]

I agonized over this forever, but would now never go back.
I assume you've seen this:

http://kosis.blog4ever.com/blog/lire-article-42357-126662-bright_kit_tweeter_mod.html

But even more interesting is Rob A's actual quantifiable analysis of the effect the mod has.

http://ep-forum.com/smf/index.php?topic=3217&postdays=0&postorder=asc&start=0

[Rob A]

Yeah, I'd put in eight if I were doing it over.

[Electroharmony]

Great instructions guys.  Just got my tweeters in the mail, and anxiously awaiting the next time I have a few free hours to install.

Wondering if you wire these tweeters in parallel, as opposed to the original series diagram, would you need to use a power resistor on each tweeter ?

[Rob A]

Short answer: no.

The resistors are just "insurance" anyhow, intended to avoid driving the amp into oscillation as a result of excessive capacitive reactance.  I tried to study the amp design and determine whether they were strictly necessary, but it's just cheap insurance so I left them in (I had some on hand, and the value is not critical).

[Electroharmony]

Just installed the tweeters...  Not quite the impact I was expecting.

 I used 4 KSN1005A piezos, wired two per channel in parallel.  The first thing I noticed was the volume was quite low, so I removed the power resistor and that boosted the sound a bit.

Unless the treble slider is past 50%, these tweeters are negligible.  I have been playing the keyboard for about an hour, and am happy leaving the treble maxed out.

And with the tweeters pointed at my knees, well that doesn't help either.

It does improve the sound in a positive way, however.  I guess I was just expecting more of a pronounced effect, and to be able to leave my treble at 50%.

I wonder if using different tweeters would have a better effect?  Maybe I'll try upgrading to 2" x 5" horns.

[Rob A]

Right, the effect will also depend on vicing and hardness of your hammer tips, but my spectrogram of typical Rhodes output is pretty convincingly showing that there's not a lot of info in the signal above 4k, which is where (from memory) the piezos kick in for real.

[Ben Bove]

My advice would be to get an EQ pedal of some sort as well, in conjunction with the piezos.  

This way, you can boost the signal even according to Rob's diagram above.  This will bring out more mid-highs.

[Kbjazzman]

๊Ummmm...... Interesting mod for my suitcase amp indeed.