Not sure which forum this would be best placed in, since it has a bit of several categories. Anyway, after some trouble getting the parts delivered, I've finally managed to construct the first of five active speakers to replace my old system.
It uses MCM 6.5" aluminium cone woofers and titanium dome tweeters, powered by 2 x TDA2050 per channel with an active crossover.
Here's a pic from the front:
and another of inside, showing the pleasingly tidy wiring:
More info, schematics and PCB layouts on this page: http://www.cheese83.freeserve.co.uk/amp/amp4.htm
Now I just have to build four more of the damned things, then a subwoofer! Things were so much simpler with a plain 2-channel setup...
It uses MCM 6.5" aluminium cone woofers and titanium dome tweeters, powered by 2 x TDA2050 per channel with an active crossover.
Here's a pic from the front:
An externally hosted image should be here but it was not working when we last tested it.
and another of inside, showing the pleasingly tidy wiring:
An externally hosted image should be here but it was not working when we last tested it.
More info, schematics and PCB layouts on this page: http://www.cheese83.freeserve.co.uk/amp/amp4.htm
Now I just have to build four more of the damned things, then a subwoofer! Things were so much simpler with a plain 2-channel setup...
It sounds good. As I mentioned on the linked page, the first thing that strikes me is the excellent bass. It's very tight, not the slightest bit of boominess, and it's quite happy to reproduce some very low notes. With a little EQ I could use these without a subwoofer and not be unhappy, at the expense of efficency. I think it would be hard to find better woofers for the price.
I was a little worried that the crossover frequency right in the middle of the midband might be a problem, but I can't hear anything wrong there, with speech being perfectly intelligible (my sound system gets used for everything: TV, music, games etc).
It does become noticably more directional above about 10kHz, due to the largish tweeter diameter.
There is some hum, but not objectionable. I wonder if this might be partly due to the lack of shielding from a metal case, as it decreases when I connect ground to earth.
I can't really say more, since listening to one is not going to be the same as five!
Oh, and yeah, I have noticed that people tend to either really like or really hate the cow-print... I go to buy the fabric tomorrow regardless!
I was a little worried that the crossover frequency right in the middle of the midband might be a problem, but I can't hear anything wrong there, with speech being perfectly intelligible (my sound system gets used for everything: TV, music, games etc).
It does become noticably more directional above about 10kHz, due to the largish tweeter diameter.
There is some hum, but not objectionable. I wonder if this might be partly due to the lack of shielding from a metal case, as it decreases when I connect ground to earth.
I can't really say more, since listening to one is not going to be the same as five!
Oh, and yeah, I have noticed that people tend to either really like or really hate the cow-print... I go to buy the fabric tomorrow regardless!
No baffle step compensation. Since they will be placed close to the walls there should be little baffle step to worry about. I do have provision for making adjustments via my computer, but without the means to make decent frequency response measurements I can't do much to smooth out irregularities.
heat dissipation
Hi,
Nice work, the cow print sounds cool to me, and great for kids. I've been doing something similar with different drivers, but because of the much hotter amps I'm using (NPs Zens) I ran headlong into the heat problem.
If you decide you need to, one of the easy ways to get rid of heat from the amps etc is probably to enlarge the panel with the connectors, make it out of aluminium and use it as a heatsink. I made mine the whole back of the speaker, seems to work well enough, but I will probably make it a heatsink extrusion to lower the temp further, at which point it is a micro version of passlabs rushmore...
Hi,
Nice work, the cow print sounds cool to me, and great for kids. I've been doing something similar with different drivers, but because of the much hotter amps I'm using (NPs Zens) I ran headlong into the heat problem.
If you decide you need to, one of the easy ways to get rid of heat from the amps etc is probably to enlarge the panel with the connectors, make it out of aluminium and use it as a heatsink. I made mine the whole back of the speaker, seems to work well enough, but I will probably make it a heatsink extrusion to lower the temp further, at which point it is a micro version of passlabs rushmore...
Two finished now. Only three more to go...
An externally hosted image should be here but it was not working when we last tested it.
Caps across the diodes are to reduce noise? Since I used Shottky diodes, the noise should be low already I think. Certainly I couldn't see anything other than normal ripple with my 'scope.mhelin said:
I've had my fair share of ground loops before, so I laready cut that
As for heatsinks: I would have used external heatsinks, but I didn't want to put them on the sides, for aesthetic reasons (it's bad enough having the connectors sticking out!), and can't put them on the back because I then wouldn't be able to remove the back without having to disconnect wires. Also it would force me to electrically insulate the chips, which would negate part of the advantage. I suppose what I could do is mount a large heatsink on the back to cool the air inside, leaving the current heatsinks alone.
Anyway, I have already performed temperature measurements on them, and they remain within sensible limits.
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