Welborne Posted November 8, 2015 Share Posted November 8, 2015 Hi guys, New here. Have been tweaking my La Scala the last few months. Bought soldered lig version K55v, replaced the mid horn with Azura Le Cleac'h flare round, tweeter replaced by B&C DE120 with a cheap PRV tractrix waveguide (us$8 each on Parts Express). I made a new Type A crossover using russian K75-10 pio capacitors. I am curious about a better mid driver, and have been thinking about the B&C DCM50. My listening space isn't very big, neither do I listen to very loud volume in most instances, so I guess the DCM50 should still be ok, although I may make another crossover similar to AlK's Universal or John Albright's DHAX2. My question is: should I get the 16ohm or 8ohm version? For example, in the Universal there is a 10ohm resistor across the autoformer which I think is to flatten the 16ohm (of k55) to something around 8ohm, and this necessitates a change of high pass capacitance from Type A's 13uf to 48uf. So If I get a 8ohm DCM50, the 48uf would not be correct and need to be adjusted. I am hoping someone can throw a torch here. Thanks Quote Link to comment Share on other sites More sharing options...
Welborne Posted November 9, 2015 Author Share Posted November 9, 2015 Any advice will be appreciated Quote Link to comment Share on other sites More sharing options...
Guest David H Posted November 9, 2015 Share Posted November 9, 2015 (edited) The type A really doesn't work for the DCM-50, the sensitivity is too high, and the type A doesn't have a band pass on the mid range. An ALK type crossover will work fine, and I would go with the DCM-50 16 ohm version. Welcome to the forums, enjoy. Dave Edited November 9, 2015 by GotHover Quote Link to comment Share on other sites More sharing options...
Guest David H Posted November 9, 2015 Share Posted November 9, 2015 For example, in the Universal there is a 10ohm resistor across the autoformer which I think is to flatten the 16ohm (of k55) to something around 8ohm, and this necessitates a change of high pass capacitance from Type A's 13uf to 48uf. So If I get a 8ohm DCM50, the 48uf would not be correct and need to be adjusted. With the universal crossover you can use either the 8 ohm or the 16 ohm. The 10 ohm swamping resistor keeps the impedance around 8 ohms regardless of attenuation level. The DCM-50 is a great choice. Dave Quote Link to comment Share on other sites More sharing options...
Welborne Posted November 9, 2015 Author Share Posted November 9, 2015 Thanks Dave! About your comment on DCM50 being too sensitve to use with Type A, how about using a lower tap on the autoformer? (In my case it is a 3636 transformer from Bob Crites with 1-18db attenuation setting)? Quote Link to comment Share on other sites More sharing options...
Deang Posted November 9, 2015 Share Posted November 9, 2015 You just can't drop to another tap. You also have to scale down the primary capacitor value because of the higher impedance (it changes based the tap you choose), add a coil in between the decided upon output tap and squawker positive (in order to form a band pass filter), and then move the tweeter connection from tap 5 to input positive -- it's almost like building a new filter. You need better capacitors too -- especially when the driver becomes that revealing. Quote Link to comment Share on other sites More sharing options...
Welborne Posted November 9, 2015 Author Share Posted November 9, 2015 Thanks Dean. But per B&C website, the DCM50 has an efficiency at 108.5db/1w, and K55v is 110db/1w (as per Atlas website). Will this be close enough as an "approximate drop in" replacement? http://www.bcspeakers.com/products/hf-driver/2-0/dcm50 Quote Link to comment Share on other sites More sharing options...
Welborne Posted November 9, 2015 Author Share Posted November 9, 2015 Here is Atlas PD-5vh http://www.atlassound.com/compression-driver-40w-16ω Does this mean the B&C DCM50 actually needs less attenuation than a k55v? And my usage will be less than 10w power handling 90% of the time. More thoughts welcome Quote Link to comment Share on other sites More sharing options...
djk Posted November 10, 2015 Share Posted November 10, 2015 Without a terminated tube plot, or the Di plot of the horn used, no one can say. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.