Rat Shck Presidian 40-5053. Next Sonic Impact?

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.

Hi again -

Sorry for the long delay, I've been very busy and somehow missed your last post. I've been running the stock and litekeys speakers in mono in my bedroom (not continuously) since my last post to really break them in. The litekeys has definitely improved - the bass level has come up a bit and the tweeter is a little more friendly. But for my ears, I still think adding some resistance on the tweeter will balance it out nicely.

I haven't the burning need to stuff the port on the litekeys version as I did with the stock. The addition of the crossover has cleaned up the woofer sloppiness quite a bit, but it's too hard to tell until I have two matching speakers running in stereo. I kind of wonder whether any analysis went into the design of the port at all - or did they just stick a random tube in the cabinet?
The rear of the cabinet has quite a bit of vibration which must be adding coloration, (as does the plastic grill frame, which is easier to eliminate) Even though there is a clever adjustable brace included in the kit, it can't really be engaged in a useful location inside the cabinet because the woofer takes up almost all of the front baffle. So adding stuffing may be useful to help damp some of that.

I'm hoping to finish up playing with these over the Xmas holidays, and I'll post my final results then.

Cheers, Chip

i have since placed 2 ohm resistors on the positive tweeter terminals to very good effect.

chip, i also noticed the vibration at the rear of the cabinet, and took the following measures: aside from putting generic dynamat on the inside of the cabinet, i got some 2.5" by 0.5" oak from lowes and gorilla glued it to the back of the cabinet on either side (9 10/16" long). this just clears the port area, but not the terminal cup. so i removed the terminal cup (a major PITA, btw), and glued another smaller piece of oak with rat shack binding posts. just file an oval area from the oak on the sides and you could easily keep the spring-loaded terminal cup.

thinking of also gluing some oak to the bottom of the cabinet which would further add some stability/mass without affecting aesthetics. hey, it's cheap and easy.

regarding the braces: THEY DO FIT, but in the following way: i requested and placed TWO per speaker, on either side in between the drivers. all you do is discard the square wood piece that is supposed to go with the non-threaded end and snug up the round brace to the baffle in that area. i didn't put any dynamat on the inner back in the area where the square piece for the threaded end fits, and gorilla glued front and back. it was a bit of a hassle reaching in to turn the brace while keeping it straight, but hey, i'm satisfied.

even with all this, mine seem to sound a bit better/clearer stuffed.

hard to tell if the port was a random act or a design intention. it's too thick to be a discarded chinese toilet paper roll :-) :-)

hope this helps a bit.

happy holidays!