Another Classic Restoration, Acoustic Research M6 Holographic Tower Speakers

Acoustic Research M6 Holographic Tower spekaers 

This pair of Acoustic Research M6 Holographic Tower speakers has been in Papa bear's hifi system since 1990. Recently Papa bear decide he wants to spring clean his AV room and ill' bear got this as his heir loom! A visual inspection of the speakers reveal that it's dusty and in need of some tender loving care, especially that 5 inch mid driver with a rotten voice coil cap. I did some Googling and found some information about this pair of speakers. This speaker was designed using time alignment combined with direct/reflected sound theory ala Bose as it's development basis for better sound staging & improved spatial cues, for that "life like" musical feel.

This speaker design is unique as it came coupled to that mat black pyramid shaped top module, with a dual 8 inch internal sub woofer, built in to a high gloss piano black finished tower box! A pair jumper cable connects the top pyramid shaped module to that tower box below. The top module locks to the bottom sub woofer box with 3 tight fitting pins.  I remembered being mesmerized by the sound of this pair of speakers growing up as a teenager, until I got my own system, that is.

Hence I would like to put in some effort and TLC DIY elbow grease to make this pair of Acoustic Research M6 Holographic speakers come alive again! The following picture guide depicts the work that went in to restoring this pair of beauties!

First step is to unplug the pyramid shaped top module from the bass tower box.

Looking around to access the speaker driver, I found 6 screws at the back of the pyramid module, made from molded plastic. 

Once the six screws are removed, I had to carefully pry open the plastic case as it was glued shut all round to prevent leakage of air. The glue around the front & back housing were removed with a pen knife with gentle scraping motions. The 2 way speaker drivers are revealed once the casing is opened.

The back housing have some acoustic foam stuck on inside to dampened the plastic module. Also in the back housing is the 2-way passive x-over for the tweeter & mid drivers. Yeah, I work on my kitchen table too!

The 5 inch mid driver was removed and revealed a rotten voice coil cover. I brought the drivers to a speaker repair expert to check on the condition. He took a good look, made a few presses on the cone, and then told me they mid range driver is fine, and all I had to do was get the replacement voice coil dust cap, and glue it back on my self. 

And so the speaker expert revealed to me that what we've been calling speaker glue is actually Araldite 2 part glue, available from any good hardware stores!

The surface of the mid driver was give a proper cleaning and vacuum out all the bits of rotten material from the old voice coil dust cap. The 2 part Araldite glue mixed, and applied to both the paper cone & new dust cap surface before joining up and leave for a couple of hours to cure.  

Once the glue had settle and cured, I just repeat the whole process removal process above in reverse and whoala! the speakers are fixed and awaiting a new musical life!

 After that, I gave the piano black gloss finish at the bottom sub woofer box an nice polish to return to shiny look. I haven't hooked up the speaker to test for sound yet, but I can't wait to do that. Stay tuned!