I wanted to share with you some of my SDA experiences over the years. It’s a long read but hopefully informative.
I began my SDA hobby in 1997 with a used pair of 2Bs that I bought from a local shop. They replaced my Monitor 10 Series 2, which had been my primary speakers since 1993. I used the 2Bs for a few months and then stumbled across a pair of SRS 2.3s at a different local shop. The salesperson attempted to demo them for me with two Denon monoblock power amps while the interconnect cable was in place. What a display of fireworks! The grills were off the speakers when he started playing a CD, and I clearly remember seeing about a 1" excursion on all 12 drivers while they produced extremely loud popping noises. The end result was 2 blown tweeters (the main one in each channel) and one dimensional driver. It had burned so badly that the lacquer around the voice coil melted and caused the cone to become frozen in place. I purchased the pair for $300 in their less than ideal condition. Nevertheless, I ordered replacement parts and got them working in no time. However, I felt they lacked midrange clarity.
In 1998 I actually converted the 2.3 to a 2.3TL. My father played an instrumental role in helping me with this project and the others I will describe shortly, as he is skilled in working with electronics. I swapped the left and right cabinets and ordered 12 MW6510s and 6 SL3000s from Polk, new internal wiring from Home Depot, and new crossover parts from Madisound. I used Carli polyester film capacitors, standard inductors, and sandcast wire-wound resistors. After all that work, I noticed that I heard much more detail than the regular 2.3, especially in the midrange. However, it was not really pleasing, as vocals, soprano sax, and electric guitar often became harsh. It wasn't scratchy - not something that could be fixed by replacing the tweeters with the now popular RD0198-1. The problem resided somewhere within the frequencies chosen for the crossover points. Though dissatisfied, I left it like that for a while.
In 1999, I bought a pair of SRS 1.2TLs off a posting I saw on deja-news (now Google groups). They sounded great, but it bothered me that the 2.3TLs sounded so different. My next attempt was to actually use the 1.2TL crossover in the 2.3TL. So, in 2002, I again ordered all new crossover parts. The only part of the circuitry that I eliminated was that which corresponds to tweeter 4 in the 1.2TL (for obvious reasons). Not bad – getting much closer! Still the midrange seemed a bit forward, a property inherent to MW6510 drivers. So, I ordered 8 MW6503s for the stereo arrays and replaced the MW6510s. It was even closer, though I still heard “hootiness” within the cabinet on some vocal tracks, slightly above 200Hz. I also left the MW6510s in the dimensional array, as they afforded a really wide sound stage. Though not perfect, I decided to leave it alone for a while.
In 2003, I read the “Picking Capacitors” article by Walter Jung and decided to switch all capacitors in the tweeter sections of both the 2.3TL and 1.2TL with Solens. This was a significant improvement. Cymbals were clearer and had less “fuzz” around them, as did female vocals and solo reed instruments. In this round of experimentation, I also decided to modify the cabinet of the 2.3TL in an attempt to reduce the aforementioned hootiness. I added internal bracing from side to side behind the middle of the driver panel, and a 3-sided brace right below the crossover. I also added one more brace from front to back above the highest tweeter. Finally, I ordered 2 quarts of Soundcoat from Percy Audio and painted the insides of the cabinets. Wow, what an improvement! No more boxy sound! (Well, maybe just an iota on one or two particular frequencies, but it was more than acceptable.) The center image also became much more prominent.
It is during this experiment that I also learned how important it is to have the internal damping material opened and spread evenly. While replacing the tweeter caps in the 1.2TL, I noticed that the damping “fluff” was rolled up into a narrow bun. I could see the back and sides of the cabinet showing. So, I opened it up, trying to cover as much of the perimeter as possible. That change alone added some midrange clarity. However, the midrange was now better on the 2.3TL. The only difference was the use of Carli caps in the 2.3TL and stock NP-electrolytic caps in the 1.2TL. I did not think it mattered what kind of cap was used in a low-pass circuit, but I rounded up some Carli caps I had in the basement and replaced the stock caps. Wow! They do make a difference, most noticeable on any recording with acoustic guitar. It no longer seemed like the guitar was being played from behind a curtain. Individual notes could be heard more clearly and with “space” in between them.
Now comes the latest (and probably my last) experiment. Though I hardly ever post, I read this forum all the time (sorry – hopefully this makes up for it :) ). I see how everyone speaks so highly of Mills resistors, Solen caps in the low-pass section, better tolerance silver-mica caps, and the new RD0198-1 tweeters. So, I ordered all of these components for my speakers and installed them in the 1.2TL this weekend. Next week I will do the same for my hacked 2.3TL.
(Though off topic, I can confirm the inconsistency of the silver-mica caps used. My left channel used unmarked caps and my right channel used caps with a value of 560pf.)
I replaced the silver-mica caps with 750pf caps from Parts Connexion. I used 12w Mills resistors in place of the sandcast stock parts. Solen capacitors went in the low-pass section. Moreover, I also took a risk by replacing all inductors for the woofer section of the crossover, including the large 16mH. I ordered Sidewinder 1.0mH and 2.0mH chokes for the midrange and a large, custom-wound steel laminate 16.0mH choke for the bass, all with lower DCR than the stock parts. Yes, I know changing the DC resistance can change the overall Q of the speaker as well as shift the crossover points slightly. I am also intrigued how a speaker can be rated at 1000 watts while using 100 watt 20awg wire. Nonetheless, I put all the stuff together, as pictured below.
Too much bass! Something was not right. The low bass as well as the entire midrange spectrum was too forceful and masked the tweeters’ output. I liked the low bass improvements but could not tolerate how much sound was coming from the driver arrays. So I reinstalled the original inductors, but it was still unacceptable to me – too much lower midrange. I played Sarah McLachlan’s Angel and heard tubbiness in her voice when she sang lower notes. Much to my surprise, the Solen caps were responsible for this sound. I put back the Sidewinder inductors as well as the Carli caps I previously removed. This was the magical combination — excellent low bass response that blended smoothly into the midrange. In addition, the tighter tolerance resistors and new tweeters really smoothed out the treble. It sounds like a whole new speaker. I couldn’t be more pleased with it.
(I must admit that I was looking into the VMPS RM40. However, I read an article that shows the passive radiator has a foam surround and that they tweak its performance by putting a layer of Elmer’s glue on it. Look here: http://www.audiocircle.com/circles/m...view_album.php
Maybe it’s a great speaker, but I don’t want to spend $6000 for a pair. Besides, I can have lots of fun playing with what I already have!
Well, so much for my thesis on 8 years of experimentation. I hope it can help someone in some way.