Active speakers

[Mr Evil]

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...

[wigginjs]

Wow? =)

I've often thought about building amps into speakers, but to build two in with an active crossover ... very impressive....

How does it sound?

BTW, I don't care what you say, that cow-print material looks awful =).

[Mr Evil]

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!

[Mikett]

Did you consider baffle step compensation?

[Mr Evil]

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.

[Stuart Easson]

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...

[454Casull]

The woofer doesn't vent the air trapped between the dust cap and the pole piece? Unless they perforated or otherwise vented the voice coil former, or the cone covered by the dust cap (Peerless uses the latter method in their XLS subs).

[Mr Evil]

Two finished now. Only three more to go...

[Tazzy]

Moo!

[mhelin]

Evil,

Add small caps 22-100nF across the odd numbered diodes (D1,3,5,7) in PSU. Also cut the groud line either to the PSU or to the power amp if it isn't cut already, there may be ground loop (same thing as different ground levels). Use bigger heatsinks. Outside of case, on the back panel.