x-over makes my amp get hot and shut down

[SimontY]

Hi everyone, probably a simple question for you...

I've been experimenting with different x-over combinations, and my current one makes my amp unhappy, so it seems. The amp is getting toasty hot at only moderate volume levels, and shuts itself down

After messing around and racking my brain I decided to take the parallel inductor off the tweeter leg, and I could then turn it up very loud without problems...

So - the parallel inductor obviously makes the amp unhappy. Why is this not normally a problem, and why is it a problem for me now?

The x-over is 1.5uF and 0.47mH on the tweeter, and full-range bass with impedance compensation.

Could the problem be mating a big inductor with a small cap? Or could it be positioning the components in the wrong order, physically?

Any advice appreciated!!!

 

[boholm]

Did you connect it all like this?

If you have no capacitor, then you have the problem right there, because the inductor will virtually shortcircuit your amp (1 ohm at low frequencies).

Otherwise please try and make a drawing like I did of your setup ( I can host it on a server if you can't).

 

[markp]

Make sure the coil is connected on the tweeter end of the cap. If it is on the amp end of the cap you have a near dead short!

 

[SimontY]

Woohoo, thanks guys!

I did have it connected before the cap. It sort of crossed my mind!! No wonder....

I feel stupid now!

 

[SimontY]

I'm so thick!

The inductor is something like 0.25DCR, so I'm sort of impressed with my amp taking that hardship at medium levels...

 

[Graham Maynard]

Hi SimontY,

Try 0.22R (220 milliohms non-wirewound) in series with the 1.5uF. Or 0.1R if that will work.

Cheers ........ Graham.

 

[SimontY]

Surely I'd only need to do that if I wanted to keep the configuration I have though?

I'll connect it 'properly' now and see how things work

 

[Graham Maynard]

Hi SimontY,

Your first post was the only one showing when I wrote my reply.
I did not assume that there had been an error.

Cheers ............. Graham.

 

[SimontY]

Graham, fair enough, I did wonder why you'd posted that.

I've actually removed the inductor now, and have unwound it to try 1st order on both drivers, with a very high x-over frequency, it's sounding promising so far... (but me could do with an LCR meter, or spl measurement )

It can be hard to know what causes certain sonic characteristics without LOTS of experimenting!

 

[markp]

Graham, fair enough, I did wonder why you'd posted that.

I've actually removed the inductor now, and have unwound it to try 1st order on both drivers, with a very high x-over frequency, it's sounding promising so far... (but me could do with an LCR meter, or spl measurement )

It can be hard to know what causes certain sonic characteristics without LOTS of experimenting!

Don't unwind the coil! Just disconnect it. If you have unwound it and left it in the circuit it is now a short! It is as if you took a piece of speaker wire and put it in its place. If you are going to use it on the woofer, try it as is first then unwind a few coils at a time.

 

[SimontY]

hehe, relax, I've used it in series with the + leg of the bass driver connection.

The inductor came wound at 0.39mH, and to cross over at a (seemingly desirable) ~5khz I need about 0.18mH.

I started carefully unwinding it, then lost control, lol. So I, err, had to start from scratch. Using WINISD to calculate the values I need a much bigger cap and probably many more windings on the coil. Currently, I have a 2.2uF cap (should be ~5.3uF) and a small amount of coil winding, but it already sounds really good, especially at low levels.

I will wind more on soon, and hopefully buy an LCR meter.....

My amp is cool and happy now btw