Notes for speaker tweakers -- my DIY audio engineering mods this year:

Infinity RSII: pulled midranges and replaced with Infinity 5 inch (not 5.25 inch) carbon fiber (125-3k, 125-1.5k, 125-2.5k) ; replaced bullet woofers with Infinity 10 inch carbon fiber (at 60 and 125). Toed in for better imaging. Results: midrange much more present with better overall dynamics and resonance elimination, and more acceptable performance on vocal passages. Bass presence is more controlled but heavier, less punchy (no wonder the Kappas did not have much cabinet depth -- these IMG's are very short throw and they do not need a lot of cabinet volume to provide resonance). Midranges now competitive with EMIMs. Overall carbon-fiber coloration is apparent (I like it). Now more musical at low spl's, but not as well-paced for dance music, the mods are like turning a fiddle into a cello. They no longer rock loud, but they are delicate even at a whisper (was this really a good tradeoff?). Even though smaller midrange drivers don't quite fit the cutouts, they are stronger, brighter, have better high volume characteristics, and importantly, almost as good looking as the original presentation. I had an old Sansui midrange compression horn for the low midrange for a while and it was an excellent choice for horns, but harsh with vocals.

Infinity Reference Six: replaced EMIT-R's with older linear EMITs and remounted in pole position (think of B&W Nautilus) on top front of cabinet. Upper midrange is now a Vifa 4.5 inch. Seiko carbon fiber 10 inch woofer (crossed below 200). Polypropylene bullet woofers went deeper, but the Seiko is generous in upper bass volume and has the right color. Now multinational: Californian highs, Danish upper mids, German lower mids, and Japanese bass. Vifas are excellent in this application. Still too bright -- need to put original EMIT-R's in there.

EMIM'd Jensen CCS pair: drivers and crossover removed, just the box retained, replaced with Infinity Reference Five 3-way crossover (300, 4k). Reflex port closed. Infinity 5.25 inch polypropylene and Elan 5.25 inch carbon fiber full range crossed over at 300Hz (wired in parallel). EMIM midrange in pole position with no baffle. EMIT tweeter mounted midships, slightly outboard of center axis. External cabinet bracing. Result: a fine midrange-resolving, surprisingly bottom-present pair of speakers that are probably the most addictive to listen to. Proof that the formula for deep bass from small drivers is large magnets plus deep crossovers plus sealed boxes (also, this box has more volume than many small boxes) -- but the upper bass dominates, so these are not good dance speakers and certainly not for reference. Best for those soloist type passages -- guitar, voice, cello. Painted white.

DefTech'd Jensen CCS pair: crossover and drivers removed, only Jensen cabinet retained. One 5.25 inch Infinity polypropylene midrange mounted firing inwards to a passive radiating 5 inch doped paper cone midrange mounted properly in its baffle. Two-way Infinity (RS6000?) crossover mounted outboard with 5-way speaker posts and clip inputs permitting main midrange wired directly to input. Midrange is Definitive Technology paper cone 5.25 inch mounted on top of cabinet off-center. Infinity polydome tweeter mounted at 45 degree angle to baffle on rear of (rectangle cross-section) cabinet out of phase. This is an incredible mongrel! Jensen is placed with midranges to ceiling, tweeters firing back and out, or placed on one end, with midranges firing 45-degrees to center, tweeters firing back, 45-degrees to ceiling. Result: Looks like hell, like Pompidou in Paris, but this is the sound that Bose should have created when it tried to produce a large amount of reflected sound. This small pair can fill a large room and is robust across varying sound levels. The key is to have overly prodigious tweeters and an extremely accurate and likable forward midrange.

Kef C40: Replaced lower woofer with HKM Westra 8 inch doped paper woofer. Result: retains all the original silk tweeter and oversized polypropylene upper midrange imaging strengths and deepens bass output to acceptable tonally balanced levels. I had the B&W woofer in here, but the Westra is a much better match. I also had the titanium dome tweeters in here, and they were ok, but fatiguing as front-tweeters. Those cheap tweeters obviously have too much sizzle. So now they fire backwards, but I can't really say they add much. This is for girlfriend's video system, so what do I care? The real key to fixing a C40 is to replace the lower woofer with a Westra.

Infinity Center mono/stereo mini-tower: Removed drivers and crossover, wired with two separate Infinity RS2000 crossovers (4.5k) for asymmetric L/R or mono bridging, one 5.25 inch Infinity polyproylene, one Kef B110 SP1057, one EMIT-R mounted on one side (trapezoid cross-section cabinet), one Infinity polydome. Result: supplies added dimension to mono signals and stereo inputs alike; B110 and 5.25 collaborate beautifully in this small cabinet. I had a polydome tweeter in here for a while instead of the EMIT-R, and it was also good, but the idea is to mismatch L/R, and the EMIT is clearly a better driver. This is a fantastic design. Really amazing for tv applications, but this is probably a lot like the great illusion of a good sounding car stereo.

Infinity RS Video pair: retained one of the 5.25 carbon fiber shielded midranges and polydome tweeter in each and substituted an Elan 5.25 shielded carbon fiber full-range for the other original Infinity driver (which is generally a weak driver) with Infinity Reference Two crossover (3k). Added an in-parallel out-of-phase titanium dome dipole tweeter to back face, which also closes off the reflex port. Result: still a lot weaker in the bass than the mono/stereo tower with the older softer components, it is at least a proper TV center channel pair with good clarity and musicality.

Infinity Reference Two with monsoon electrostatic panels: using crossover from b&w dm110, bypassed tweeter and mounted sonigstix monsoon emim/emit panel on top phase-aligned with woofer. An interesting fairly low budget speaker! Monsoon panels are much better in a 2-way crossover than a 3-way, or as a full-range driver. I would build this and sell it if I thought I could make a profit. People should stop buying monsoon panels unless they are going to use them in 2-way systems. EMITs are still more musical, but monsoon panels are very revealing. Mids dominate highs, which is really OK for a lot of sources. Sometimes it seems there is not the right tonal neutrality on difficult sources. Requires further study.

ESS Heil AMT1d: 12 inch woofer replaced with doped paper cone MTX Blue Thunder under metal grate (crossed at 800). Grilles removed and red laminate finish added. Result: much better match of low end to monstrously capable high end. This is my favorite place to play Telarc 1812 overture discs. Probably needs even more modern woofer. Yes, you can hear the air being squeezed. I can't believe I haven't given these speakers non-stop tango music.

Unmodified: Magnepan SMGa (very picky about placement, rather bland), Kef 105/4 (laid back and throws around images, goes very loud, but never gets raucous), NHT Super Two (proof that modern silk domes can do metallic horn sounds, a good reference speaker with lower 6.5 at 120, upper at 2.2k -- bass is not quite right), Cerwin Vega D5 (not hooked up), Cambridge Soundworks (surprisingly capable for surround and bass fill). Sold: NHT Super One, NHT Super Center, B&W DM302s2, B&W DM110i.