Rat Shck Presidian 40-5053. Next Sonic Impact?

I got the upgrade kit for the Minimus 7 and installed it a couple of days ago. The improvement in the sound is dramatic, well worth the $20 cost of the kit and the half hour it takes to install the new crossover.

I've always liked the Minimus 7 because of it's very small size and construction. Litekey's kit turns it into a very respectable little speaker.

Be prepared for some head scratching over the included instructions but once you sort it out it's pretty straightforward.

sfar, as i stated above it was my own experience with the m-7 upgrade that led me to approach larry about the presidian. this speaker "bottom-feeder" upgrading/modding is just plain fun, especially while finances are temporarily lean.

QUESTION: could someone provide me a measurement (in millimeters) from the center of the stock presidian tweeter to the center of one of the fixing screws? i have already snipped off the phase plug thing to fit the new tweeters. thanks in advance.

Well - I completed the upgrade on one of the Presidian speakers tonight and A/B tested against the still stock one. I used an old Marantz receiver for 2 reasons - it has the ability to run R & L speakers from one mono source AND it has excellent tone controls (Bass/Mid/High).

I need to do some more experimenting but here's what I've observed so far:

1. The upgrade kit is VERY reasonable for the amount of time Litekeys must put into it AND it is definitely an improvement over the stock. It took about 2 hours start to finish ( I soldered all new joints). You have to have fairly nimble hands to install the crossovers inside the cabinets.

2. Most of the improvement comes from the upper mids to the highs and it is not subtle - if you had to pick either the Litekeys version or the Stock version of the Presidian and not mod further, it's not a contest. The Litekeys is a big improvement.

3. That being said - the situation is more complex. By playing around with the tone controls on the receiver I was able to improve either Presidian considerably. On the first A/B comparison it became obvious that the stock Presidian is rather attenuated in the highs. The sound is muffled compared to the Litekeys speaker. However the Litekeys version is a bit lacking in the low end by comparison - which may simply mean, in a 2 way system, that the tweeter is a little too hot.

4. The original Rat Shack tweeter states 8 ohms on the back, while the upgrade (a Dayton ND20TA, cheap yet well-respected among DIY'ers for it's flat response) is nominally 6 ohms. However actual measurements from Dayton show it really runs about 5.5 through the meat of it's freq. range.

These relatively different tweeter efficiencies may explain a lot of the immediately noticeable audible difference between the stock and the litekeys Presidians.

I found that if I turned the Treble control nearly all the way up that the stock speaker improved considerably - possibly even bettering the Litekeys in the extreme highs and while maintaining the better bass at the same time. But it's hard to A/B that reliably because it involves flipping 3 nobs as simultaneously as possible. On the other hand, with the Litekeys speaker, turning the bass up a lot and boosting the mids a little yielded a substantial improvement to my ears.

5. So I don't feel that the Presidians are yet optimized. In order to sort this all out I feel I need to try a few things - in this order:

A. What if I just replace the stock tweeter with the Dayton in the 2nd (still stock) speaker and leave it untouched otherwise?

B. What if I add the Litekeys crossovers but keep the original tweeter?

C. What if I add, say, a 3 ohm resistor (probably about right) in line with the Dayton tweeter in the Litekeys version speaker to better balance the tweeter and woofer responses?

D. What if I add a 3 ohm resistor in line with the woofer in the stock speaker to attempt to better match the tweeter level?

I'll tell you what sounded better than either one at this point - stacking them on their sides and running both of them simultaneously with the balance a little higher on the Litekeys speaker. Their different tonalities balanced out very well and it really sounded pretty impressive. You could make a case for buying two pairs and running a baby "line array" like this - with one pair upgraded and the other stock. Not bad for about $125 total!

I'll report back here when I've tried as many of these as I can before my kills me....

This morning I A/B'ed the single Litekeys Presidian against a Dick Sequerra Metronome, which is admittedly a dated design - but cost about $800 for the pair new, and the Presidian was hands down the winner - with the one drawback being that softness in the lower mids. (Can't compare imaging obviously as I only have one Litekeys speaker right now.)

Also - Since I've hardly used the Presidians at all, even before the mod, and the Litekeys side has a brand new tweeter, I'm going to let them break in for a few days before trying my further ideas.

just now catching up with the thread. opalchip, your comments are very intersting and much appreciated.

i contacted litekeys and he said he intentionally left the tweeter a little "hot," and simply placing a 2 ohm resistor in series with the positive terminal should do the trick (he actually said 2-4 ohms depending on taste so opalchip certainly had the right idea). i couldn't imagine that litekeys didn't take the 6 ohm impedance of the new tweeter into consideration.

opalchip, regarding the midrange, are you stuffing the cabinets or ports? i'm referencing your comments from 1/22/06. i plan on addressing the treble issue first, then listening more intently for your perceptions of the mids. i'm wondering if a little experimentation with the type and amount of stuffing material may be a potential solution.