Hi
Need help here ... i have a diy 10inch vented subwoofer ... (passive sub driven by LM3875 with subwoofer controller - All DIY circuit) ... my problem with my subwoofer is it pops/cracks on certain occasion on constant volume level ... sometimes it behaves rather well ... just gone through some bass blasting session this morning (behaves rather well) ... then suddenly these popping/cracking noise came ... BTW actually it has this problem in the past also ... in other words is intermittent ... volume level is constant ...
feedback are well welcomed ... TQVM ...
Need help here ... i have a diy 10inch vented subwoofer ... (passive sub driven by LM3875 with subwoofer controller - All DIY circuit) ... my problem with my subwoofer is it pops/cracks on certain occasion on constant volume level ... sometimes it behaves rather well ... just gone through some bass blasting session this morning (behaves rather well) ... then suddenly these popping/cracking noise came ... BTW actually it has this problem in the past also ... in other words is intermittent ... volume level is constant ...
feedback are well welcomed ... TQVM ...
Not enough information given to help you.
It could be one of many things, such as the driver exceeding the mechanical limits, especially if the sub is forced to play frequencies below its tuned point.
It could also be from the current limiting in the LM3875. This can be caused from running the IC at too high of supply voltage into too low of load impedance. Impedance can be lower than the drivers nominal rating at the subs tuned frequency. I've noticed some ICs current limiting can make a loud pop or cracking sound with reactive loads.
It could be one of many things, such as the driver exceeding the mechanical limits, especially if the sub is forced to play frequencies below its tuned point.
It could also be from the current limiting in the LM3875. This can be caused from running the IC at too high of supply voltage into too low of load impedance. Impedance can be lower than the drivers nominal rating at the subs tuned frequency. I've noticed some ICs current limiting can make a loud pop or cracking sound with reactive loads.
oh ... ok ... thanks for the info ... maybe gonna try to switch another amp and see if maybe the amp is the culprit ...
The fold-back current limiting has a variable limit based on the temperature of the die in the IC.
It will make a loud 'farting' type sound when activated.
It will make a loud 'farting' type sound when activated.
I had exactly the same problem with an Eminence Kappalite 3012LF vented box. I was blasting Latin Fever by Wolfgang Gartner through it on a bridged Acoustic Solutions SP101 (one channel out of phase on crossover) and for my experience, was silly enough not to use a high pass. It probably bottomed out at some point and the voice coil is now dented and rubbing against the magnet gap. Okay at low volume, but needs a recone - a definite rubbing coil. I hate being British where the shipping brings a recone up to £80!
I discovered that particular amp can make funny sounds (different from usual clipping, which just makes a muddy sound in my woofer) when cranked and bridged (to be fair it wasn't designed to be) as I thought my other woofer which I was STRICT about high passing had the same thing happen. I did a sine wave sweep from 38-100Hz, turning up gradually to monitor excursion. Using only one channel on the amp there was no such sound. No rubbing when I gradually cranked 10Hz to test excursion either. I was relieved as I thought I had damaged the second woofer due to trying to bridge a stereo signal, and infrasonics created by the difference in bass on each channel had caused it to fail.
When I get a proper PA amp I will try it up to the box's 40 Volt theoretical modelled limit (9mm Xmax) in the pass band just for peace of mind. The Acoustic Solutions amp could put out about 17 clean volts per channel.
Also what is the position of the ports? You could POSSIBLY be getting cone rocking which MIGHT cause a tight tolerance voice coil to rub. My box had 4 ports, a triangular one in each corner to even the cone load (and help brace the box).
This is all the advice I can give over the internet, without even a picture of the box.
I discovered that particular amp can make funny sounds (different from usual clipping, which just makes a muddy sound in my woofer) when cranked and bridged (to be fair it wasn't designed to be) as I thought my other woofer which I was STRICT about high passing had the same thing happen. I did a sine wave sweep from 38-100Hz, turning up gradually to monitor excursion. Using only one channel on the amp there was no such sound. No rubbing when I gradually cranked 10Hz to test excursion either. I was relieved as I thought I had damaged the second woofer due to trying to bridge a stereo signal, and infrasonics created by the difference in bass on each channel had caused it to fail.
When I get a proper PA amp I will try it up to the box's 40 Volt theoretical modelled limit (9mm Xmax) in the pass band just for peace of mind. The Acoustic Solutions amp could put out about 17 clean volts per channel.
Also what is the position of the ports? You could POSSIBLY be getting cone rocking which MIGHT cause a tight tolerance voice coil to rub. My box had 4 ports, a triangular one in each corner to even the cone load (and help brace the box).
This is all the advice I can give over the internet, without even a picture of the box.
Simple ported box 45L ... 3in flare port tuned to about 42Hz ...
Below pictures of amplifier and subwoofer controller from ESP (project 48)
Below pictures of amplifier and subwoofer controller from ESP (project 48)
Attachments
Well I can't rule out cone rocking. What sort of power levels/Xmax are we talking here?
I can't give advice on the amp circuitry I'm afraid.
I can't give advice on the amp circuitry I'm afraid.
I certainly had loud noises, perhaps pop or crack sounds with my first sub. Dual Kef b139 make a very loud noise when they hit bottom, and even in a sealed box will do so... Had to move to bigger woofers....
You need to make sure you know the limits of your creations with a Volt meter, frequency generator and excursion. Some subs can survive the odd bang on the back plate. Others, the coil will be dented like a toilet roll tube on a table, develop a permanent rubbing against the magnet gap and need to be reconed. This is what happened to me with a brand new Eminence 3012lf driver, be warned!
BTW i am on the way ordering a new different 10inch woofer to see if is the culprit behind ... currently no spare woofers hanging around my house since my favorite dual 12inch DIY subwoofer sold already ...
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