Listen to my sub

[mikee55]

Whats it doing???????

Mike

 

[rabbitz]

Rubbing voice coil? Does it make any noise when you push the driver by hand? Spider intact?

Sounds like it needs to be put out of it's misery.

 

[Cal Weldon]

Strange sound. Did you overheat it?

 

[mikee55]

Hello

The woofer is fine physicaly.Its got 300w written on it. I don't have an amp that big. I'm using a Linkwitz Transform after a 24db 40hz lowpass filter. Its tuned to 20hz.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=98902

Driving me up the wall.

 

[pinkmouse]

EQ breaking into oscillation?

 

[mikee55]

Okay

With limited test gear, DMM and a 24bit soundcard on my PC. Could download scope/oscillator software, how can I test that theorey? Would the speaker have to be attached, thats probably a dumb question, but the missus will probably get arsey, if I set it up in the kitchen
Tell me! Please!!



Mike

 

[ocool_15]

Not sure if it helps but the content starts at 403.2hz( on a 1/24 octave rta) with harmonics (806.3, 1208, 1613 ect). Sounds like feedback/ oscillation problem.

 

[mikee55]

Oh poo

Sorry, although its a .wav file, it was done with an mp3 recorder.Sorry, shoot me. Im gonna run in on my pc and try for a visual of some kind.
cheers
Mike

 

[pinkmouse]

How much gain are you running with your LT?

 

[theAnonymous1]

How much gain are you running with your LT?

18.56dB

 

[richie00boy]

That's a lot of gain but I've run 20dB before without a problem.

Mike I know you had some issues when building the circuits up so it's possible something is wrong or broken. It just so happens I made one PCB of each sub controller and LT for somebody recently, and now they don't want them...

 

[mikee55]

Hi Rich

Just sent email via button above, forgot you are away. Put my name on em. When you ready, I'll send you a cheaque or something and I will rebuild.
Regards

Mike

 

[mikee55]

Still bugging me, though

Seems to be an answer, to build it again. But I would still like to know and will continue to play. It took a lot to come this far and its given me sleepless nights wandering where I've gone wrong. I ain't got the guts to take it apart, but I will.

Its too late to test it tonight, kids gone to bed, but in the morning I'm going to take a waterfall plot using Spectrum Lab.
http://www.qsl.net/dl4yhf/spectra1.html

Great bit of software, try it.

Get back to you soon.
Regards
Mike

 

[mikee55]

DOH!

STUPID,F*%$ING GROUND, a tiny break in a ground track on the LT pcb, not visible by eye, shows up like looking through Hubble on the DMM.

Many thanks for listening. Sorry, but I'm used to hum when I loose a GND wire.DOH!


CASE CLOSED

Thankyou

Mike

 

[pinkmouse]

Glad you got it sorted.

 

[mikee55]

Thanks Pinkmouse

But, hold on. Sir, maybe you could help.

Now, its bloody loud as in it booms! I know its sat up close to a wall, but I don't understand why, I'm crossing at 40 hz 24db octave. I have it connected to the loudspeaker out of my main amp via 10k resistor and 10k pot in a potential divider, but its doing too much bass. I thought and had originaly crossed at about 80hz for my floorstanders. Can I cross lower, or maybe go 36db lowpass.

What do I do???

 

[pinkmouse]

Could just be the room positioning, try moving it about a bit. A clever technique I picked up from somewhere is to put it in your listening position, then walk around the room 'till it sounds good, and that's where it should go. If that doesn't work, then I'd look at electronics.

 

[mikee55]

Outta curiosity

Would it make any difference if I hardwired it directly to the volume pot(output side) on my main amp?

Cheers Pinkmouse

Regards Mike

 

[pinkmouse]

Do you have a highpass on your mains?

 

[mikee55]

Hello gain

No I don't. I don't get much boom off of my mains. Fs of my Mordaunt Shorts is about 80 hz. richie00boy suggested the lowpass be able to encompass at least 80 to allow the two to meet. However, I found that too obtrusive and dropped it to 40hz. I didn't want the transients of a Kickdrum for example to come through, just the low low stuff. I hoped the sub would only work when the signal dropped right down.

Mike