Mission 753 speaker modding

[justblair]

Hi all.

I am an overly enthuisiastic noob with a set of Mission 753 speakers. I have owned them for some time and have the itch to improve on the already very good sound.

So I have been researching avidly for suggestions on improving the sound but it seems that 753's just dont get modded that often. In fact the only thread I have found on Mission upgrades has been here.

Here is my state of play so far.

• I have mapped out the crossover, including inductor values
• I replaced the larger lytics in the crossover with nichicon KZ series
• I have a polypropline capacitor on order to replace the tweeter corssover cap
• I have applied "no more nails" to the baskets to reduce colouration.
• I have removed the metal grill from the tweeter and installed a foam rubber ring in its place

The crossover looks like this




The inductors interest me, I am considering replacing the mid and bass filters with heavier guage air core. Probably home rolled, though I am open to suggestion? The current ones are ferrite cored, guage wise they look around the .7mm region. I have read that ferrite can create distortion?

I am open to the suggestion of replacing the tweeters inductor as well, though with a resistor in the signal line, would increasing the guage (ie lower dcr) make any sense?

What are the thoughts of those that have compared air core to ferrite?

The change over to the nichicon lytics has not made a huge difference to the sound. The mid bass has a little more timbre, which is certainly nice to listen to. Double Bass, chello's and male vocals seem more musical. I am undecided though as to wether this is some extra colouration or an improvement to the quality. I currently have one crossover modded, the other stock. I am breaking in the modded one before doing a critical listen.

The Polyproplene caps I ordered before finding this site. They are mid range (am I allowed to mention the brand?) well reckoned caps. I am looking forward to them arriving. From Peter's advice on an earlier 752 thread here, I am hoping for improvements.

The "No more nails" mod is simple, I have seen various variations on the theme, but basicly i have filled the groove between the basket and the magnet with the stuff, reducing the ring from the pressed metal baskets. The effect was most pleasing. Clarity throughout the range has improved on the speakers. in blind tests everyone heard an improvement in clarity, all but one of my long suffering test subjects felt that it made a significant improvement to the music played. This is a £3 mod that i am so glad i found out about.

I plan to add some further damping to the baskets in the shape of damping sheets on the inside and outside of the legs as the basket legs are currently undamped

Removing the metal grill to the tweeter is an easy mod to do. The speaker is clamped into a plastic housing. Unclipping it, it dissasembles and the metal grill that covers the metal dome jsut pops out. It is a reversible mod, but I dont think that anyone will wish to go back after trying it.

Most recently I attempted to refine this by adding foam rings into the groove lleft behind by the removal of the grill. This seems to make the tweeter sound more like a point source than before, though I have not had a critical comparison before and after.

Here are a couple of bad photos of the completed tweeter mod.


While I had the tweeters apart i had a look at the motor construction.



I have read that some improvements can be had from tweeters by varying the stuffing in the rear chanber, You can see above the tweeters.

My thoughts were to replace the foam plug with lambswool and attach a felt ring around the metal ring that surrounds it. Again does anyone have experiance of such a thing?

My last question is wether enyone has attempted to remove dustcaps from speakers and replace them with aftermarket or DIY phase plugs?

A long post, and hopefully some people here may have some experiances that may be relevant to my project..

Blair