I found this thread after looking for details of Monitor Audio Monitor 9 speakers on the web. I bought a pair in 1991 from Raleigh Hi Fi in Chelmsford, to go with my Arcam Alpha 3 amp and Rotel RCD-955 16 bit CD player. It was quite a good setup, and later I added an Arcam Black Box II to really smooth out the CD sound. I kept this rig until this year, and in all that time, I heard maybe one other person who had a setup I actually liked more. Anyway, I have always found the ability of these speakers to reproduce female vocals to be amazing. There is also plenty of bass and drive to them, they really have done it all for me. I should add that mine have silver tweeters, not gold. My wife loves these speakers too, they still look perfectly smart and modern, and the piano finish is just lovely.
In this last year I've bought an Arcam AVR300 amp, to enable me to run a 3 speaker setup for films (might add the rear two in future) and to offer the ability to connect up some other digital sources directly. I was getting a bit tired of changing inputs by hand to the old black box. One of the features much commented on in reviews was that this new amp can use channels 6 and 7 to bi-amplify the front two channels. I thought this would be the way to go, but had to buy some new speakers to do this, so began looking, and eventually bought a pair of Monitor Audio BR6, which did show me that bi-amping would work, but were just not as good as the old Monitor 9's, unless you wanted massive volume. The treble was in fact quite a let down. Compared to the Monitor 9s they had 'air' at the top end, but no 'presence', female vocals shrank back in the mix, whereas the 9s really pull out vocals nicely. Now, when I had bought the Arcam amp, the chap who sold it to me had Monitor 14 speakers and mentioned that he had converted them for bi-amping, and after selling on the BR6s I began to wonder if I could do this to the Monitor 9s. I have pulled out the crossover, which is just on the back of the terminal plate, and here it is.
Here is the circuit
So, R1 is 5W 2.2 Ohm, C1 is an Alcap 50 V low loss electrolytic 3.3 microFarad +/- 10% cap, and I do not have the inductor values. Both could be about 0.3mH or near, given a 6 kHz crossover frequency?
Looking at how simple this crossover is, I'm planning on converting the speakers to bi-amped reusing the existing inductors and with new polypropylene caps from Wilmslow Audio
http://www.wilmslow-audio.co.uk/supersound-polypropylene-capacitors-68-c.asp. As the ferrite cored inductor for the bass is stuck down pretty well, I'm going to leave it where it is, and add a new terminal plate for the treble above it, and then just snip out the treble section from the existing crossover and make the new one on the back of the new input. I've ordered the bits with new resistors too, so I'll post photos and some impressions when I've done it. Anyway, any suggestions would be welcome. I've fixed amps and electronics in the lab at work, so not a newbie exactly, but I've not played with my own hi-fi stuff at home. I also have a B&W LCR3 centre speaker which has 2 caps in series with the tweeter, so I'll be replacing them too, but that's maybe off-topic.
P.S. Thanks bigblue for posting up the information about these, it's nice to see!
