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February 17, 2011

Modifying the Music Hall MDR-1 Table Radio

I'll start by saying that I respect Music Hall equipment and it generally represents a good audiophile value, but the Musical Hall RDR-1 Table Radio left a little to be desired in my humble opinion. Music seemed to have a compressed and uninvolving presentation, even compared to other table radios such as the Sony ICF-M1000.

I was on the verge of selling the unit, but I decided it had it's utility, and I assumed that the main issue lay with the 3" driver, which shouldn't be very difficult to replace with a more expensive driver. I popped open the unit to see what other little tweaks could be done while I worked on the unit, mostly because I really enjoy tweaking things :)

I decided that the easiest and most cost effective mods would be replacing the driver with a Fostex full range driver FF85K, lining the cabinet with Dynamat damping sheets, replace the wiring leading to speaker with Cardas 20.5 gauge wiring, and replace the easily accessible power supply caps with a known brand, Rubycon.

I opened the unit by unscrewing 6 screws, sliding out the front cover and disconnecting the ribbon that connects the display to the circuit board. The back then slipped out without issue.

Below is a comparison shot between the two drivers. The left one is the stock driver, and the right is the Fostex FF85K.

Stock and Fostex drivers

 I opted to use the FF85K over the FE83E because of the bulkier magnet. The FF85K weighs in at a sizable 565g. You can find more driver specs here. Fostex full range drivers are looked upon very favorably by the speaker DIY community, the brand wasn't an arbitrary choice by any means.

I found that the Fostex driver was slightly larger than the stock driver, so I had to melt the surrounding plastic a bit to get the driver to fit. I'd imagine the plastic could be dremelled as well, but I didn't want plastic bits ending up in the sealed display compartment. 

Melted plastic to allow driver clearance
With the new driver in place, a generous bit of Dynamat was applied to the back of the driver and the plastic casing the front display.

Dynamat mounted on driver magnet
 Dynamat was then used to line a portion of the cabinet and the port. Since the Dynamat is foil lined, I made sure to keep it away from the circuit board and anything else it may touch. 

Dynamat Xtreme mounted

 It was now time to replace the power supply capacitors with the Rubycons. 

Original power supply caps

 The Rubycons are about 30% larger, despite the same rating.

Rubycon capacitors mounted

Finally, the Cardas 20.5ga wiring was installed. There was a bit of glue on the circuit board that had to be removed before this was possible. 

Cardas wiring in place

 Here's the finished product, it looks basically stock from the outside:

Finished product
Bass extension, clarity and midrange quality was all improved, and the driver still needs time to break in. Most importantly, the radio is now very enjoyable to listen to. Perhaps I'll have to get a thicker C7 power cable for it next. Mods were in the neighborhood of $75 or so dollars for anyone wondering. 

The Fine Print:
Please remember that modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a posted modification and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind. 

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