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1 The Proteus - To D' Appolito or not to D' Appolito, that is the question
2 The cabinet.
3 To D' Appolito or not to D' Appolito? That is the question.

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The Proteus - To D' Appolito or not to D' Appolito, that is the question

By Tony Gee
27 Feb 2001

The Proteus - To D' Appolito or not to D' Appolito, that is the question
Introduction
A lot has happened in the last year since I finished the Andromeda's. On the loudspeaker side of life I have built three more pairs, of which two could already been seen in the Andromeda article, the third pair I would like to explain in more detail in this article.

What do you do when you have finished a pair of Andromeda's? You sell them! Or at least I did. Not because they are bad, according to the many e-mails I received they are one of the best speakers you could build (he said modestly). No, I sold them because the designer in me is never satisfied, he wants to conquer new frontiers and boldly go where no loudspeaker designer has gone before (and some friendly Danes offered me enough money).

After such a complex exercise I thought it was time to build something a little easier. It had been a few years since I had built a D' Appolito system and I happened to have some 7 inch mid-woofers and a couple of burnt out tweeters laying around and some left over pieces of mdf. I thought it would be fun to see what would happen if I mixed them together. Fig. 1. Image 1

I didn't want to put much effort into designing the cabinet seeing as this would be a temporary design that needed to be built quickly as I was speakerless (not a situation you want to be in for too long). I had always found the Wilson Audio Cub a very nice example of form-follows-function design so the decision was easily made. The Series-I, where I had found my inspiration, has now been discontinued. I find the follow-up Series-II not as attractive because it is less basic in form and a little more (over) styled.

The tweeter
The Seas Excel T25-001. I had by accident fried a pair due to a faulty filter so I bought some replacement domes. While I had the massive aluminium front plate off for repair I thought why don't I take out the ferrofluid? You never know, they might sound better. It comes out rather easily if you pour a little turpentine into the air-gap and carefully absorb it out using a piece of kitchen roll or toilet paper. Repeat this several times until all the dark brown liquid has gone. The cavity inside the magnet and rear volume is filled with mineral wool to dampen resonances, remove this first so that it doesn't get wet. Leave the speaker to dry for a few hours before you replace the mineral wool. The Seas replacement domes are self-centring, so putting in new one's shouldn't be too difficult.

The mid-woofers.
The Seas CB17RCY/P. I had originally bought some to use in the Andromeda. I had noticed that several commercial designs use similar units in their systems so they couldn't be that bad. They are not as good as the Scanspeak 18W8545 but considering they are much less than half the price they perform very well. They have a very lightweight coated paper cone; the moving mass is only 10 grams as compared to 15 grams for the Seas Excel units. The magnet is reasonably large and in combination with the lightweight cone it should give a quick reacting driver. A nice detail is that the basket has four extra half-depth mounting holes on the rear side. It is therefore easy to drill them through so that the driver can be mounted with eight screws instead of the standard four. I believe it is better to divide the pressure as evenly as possible around the frame to give maximum contact between the driver and the cabinet - and it looks rather cool.

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