Quad ESL Cap mods

It is a film cap and is a #71348 available from Parts Connexion.

I used it in a similar application, to filter out bass from a open baffle speaker. I didn't notice any negative effect on SQ, but it was only used on a woofer.

If you use a smaller cap you will lower bass response.

A Mundorf tube cap is not made for this application.

William, I have no experience with Mundorf Tube caps, because Tube caps are designed for high voltage tube gear power supplies, not coupling.

Regarding Face's Mundorf cap, it is a great choice if the original cap is rated for 250 Volts or less, however, I maintain my recommendation to bypass any large film caps with a Mundorf 4.7 uF silver / oil. This will provide speed and transparency in the treble range, which large film caps tend to lose due to high internal inductance (side efects of the soda can size).
224.7 uF as compared to 220 uF means that your speakers bass response will extend a couple of Hertz down, not really a factor given the usual 5% tolerance of large film caps and any resistors used within the speakers.
Good luck

I have been researching the same options for replacing the electrolytics in my Quad 2905s. FYI the 220uF cap is in series with the input and it does have a 1.5 ohm resistor in parallel with it (which could also use an upgrade to a Mills or something similar). I have read several of the capacitor comparisons including some comments specific to Quad 2905s over on the Audiocircle website. My observation is that for very little extra cost you can get 2-100uF Mundorf MKP 400V. And for a little more again you could get 4-47uF of the same 400V MKPs. With the 2905s any shift toward a heavier balance is not what I want. So with four caps instead of one I have the flexibility to try various values and see if the increased resolution and speed(expected from smaller values with higher voltage ratings) are what I like better. My big decision is whether to spend more on Auricaps which I understand have a slightly nicer midrange and apparently are a step up from the Mundorf MKPs. Their premium price at two to three times the Mundorfs would certainly indicate this. I would definitely appreciate comments from anyone who has compared these two. Another big plus with the Mundorfs is the availabilty of a nice selection of blend/bypass capacitors such as the Supremes or the Silver/oils as someone pointed out. I think its likely combining MKPs with their premium capacitor lines would really improve the sound. I'm not sure if the Auricaps sound would improve being bypassed for extra performance. From reading the Auricap datasheet, its actually discouraged. I would like to know if anyone has had good results doing this also.

I spoke to a moodder and he says F & T MPP caps with a Harmony cap bipass are the best way to go for the price. He feels the F & T MPP caps give a better result than the Mundorf MKP.

He sais the only appropriate cap for this (Quad esl) application is MPP type (Metallised Polypropylene) and of course they have to be of adequate voltage -- because of this, suitable candidates are limited and pricey...

Any comments?

Any experience or comparison of F & T MPP caps?

thanks,
William

The Mundorf is rated at 250V, which should be more than enough.