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POSITIVE FEEDBACK ONLINE - ISSUE 19
 
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Our readers respond…we respond right back!

Send your comments to either drobinson@positive-feedback.com or dclark@positive-feedback.com

 

 

Dear Sirs
I enjoyed Levi's report on the New York show but would like to clear up some misinformation on the Talon speakers.

The Firebird diamonds now retail for $48,000 and do weigh 300lbs each. However, the Firebirds weren't at the New York show. Bob was listening to the new Firehawk's. They weigh about 200lbs. each and now retail for $36,000 with the diamond tweeter.

Regards, Frank Gortz

P.S. Keep up the good work on your outstanding online mag.


I recently brought back my Dual CS505-1 from its burial plot in the basement.  So it was with great interest that I read your informative and interesting, albeit too late to help, article on restoring vintage turntables.

Two points to add on the Duals. Foremost is the $60 that needs to be spent to convert from the proprietary Dual cartridge mount to the industry standard 1/2" mounting pattern (make sure you get the additional counterweight).  Your only alternative to this is to buy a replacement Ortofon stylus. This will also run you about $60 and leave you with a 20 year old bass deficient cartridge. This leads to my second point. Audio Technica makes several excellent lines that are a good match for the intended budget. I put a AT316 on my Dual and was quite surprised and pleased by the improvement over the Ortofon. I realize that statement borders on heresy, but I stand by it.

Thank you for your time, and your excellent site.

Regards,
Bob Beischer


Hi, Carl,
Looks like you had fun upgrading your 3.6s (see Magnepans). However, you did say the idea was to "take them to their limit", in terms of sonic improvement, so I thought I'd suggest several more things you can do.

These additional mods WILL make them sound better!

1. Remove the wooden styles and take the socks off so you have Maggie in all her naked glory. Then, stiffen up the panels by glueing aluminium U-channel down each side. If you wanted to take this stiffening idea to its extreme, glue U-channel on the top and bottom edges as well.

NB: This means you are not going to be able to put back the wooden side-pieces (unless you use a router to widen the slot on their inside edge). However, I suggest removing the styles makes your Maggies more attractive - particularly if you have the black or grey socks. All you see then are slim, black or grey panels!

2. The 3.6 is constructed from one overall sheet of MDF... a sonic advantage will be gained by isolating the piece of MDF which the ribbon-cage sits in, from the MDF panel which the base/mid-panel assembly is fixed to - so base/mid vibrations do not shake the ribbon-assembly.

This requires you to use an electric saw to cut a slot almost the whole length of the panel, between the mid-panel and the ribbon-cage (I suggest you remove the ribbon-assembly first!! :-) ).

NB: If you have stiffened the top and bottom edges of the panel with aluminium U-channel then this will be sufficient to hold the piece of MDF panel in which the ribbon-cage sits, in place... ie. you can extend the cut in the MDF from top to bottom, before glueing the top and bottom U-channel sections in place.

You will then need a more complicated stand arrangement to cope with an independent "ribbon-panel".

3. If the 3.6 base/mid-panel assemblies are held into the rebates in the MDF panels by many staples (like my IIIAs), these need to be replaced by a more solid fixing arrangement. Particularly if you have gone to the trouble of holding your panels rock-solid with some substantial stands, you want the base/mid-panel assembly to be held firmly against the MDF panel. The staples are not capable of doing this effectively because MDF is too soft!

I believe the ideal solution is to use some short lengths of mild steel right-angle section which can be screwed to the back of the MDF panel, so that their edges touch the back of the metal plate and hold it firmly against the rebate in the MDF. You use one length of this right-angle section between adjacent metal-plate support-bars.

There are two additional possibilities within the crossover rebuild itself:

1. You didn't specify whether you did this but, the way the IIIA/3.X speakers are constructed, the ribbon HP filter has already had to go through a 200uF cap in the external crossover box.

This degrades the sonics of the ribbon. It is better to rewire the ribbon HP filter so that its input comes directly from the input to the external crossover box ... not the output from the external crossover box. However, this requires some computer modelling to bring the mid LP & ribbon HP crossover point back to their original place.

2. There is also the matter of adjusting the HP and LP crossover points slightly, to smooth out the overall frequency response. With IIIAs and 3.3s, anyway, the overall frequency response is far from flat and by moving the pairs of LP & HP -3dB points apart slightly, a flatter result can be obtained.

Regards,
Andy


Dear Editors
One interesting tweak is putting a humidifier in the listening room. This reduces static electricity, and it also makes the air slightly heavier, giving the sound more impact. Do not make the room too humid, however.

I am be wrong, but if we remember our high-school chemistry course, the molecular weight of H2O or steam is 2 hydrogen plus 1 oxygen which equals 2*1 + 1*1 = 18. Whereas the molecular weight of air is around 28. Hence, steam is lighter than air and adding humidity to the room makes the air lighter. So, I don't know what Clay is thinking, but I think he's got it backwards.

Russell DeAnna, Anniston, Alabama

 

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