Just to clarify several issues I am seeing about bad / odd smells with your woofers

[toaster 10+ year member]

All,

As stated, I would like to clarify what is causing most of these issues with bad smelling woofers in ported enclosures. Again, this is only for ported enclosures. Sealed enclosures will not experience this issue. Most of the newer digital music these days has notes that go all the way down to 20-25 cycles. Most ported enclosure applications call for tuning anywhere from 32 cycles all the way up to 50 cycles. What you need to remember is that, with any ported enclosure, your woofer has virtually NO power handling at frequencies lower than your box is tuned to. The reason for this is the mechanical damping of the enclosure itself. When you put your woofer into a box tuned to a certain frequency, you are tuning the entire woofer system, which includes the woofers and enclosure, and the environment immediately surrounding the system, to a certain resonant frequency. When you play a song or tone that goes below whatever your woofer setup is tuned to, it cannot control the woofer motor's movement, and the entire system becomes unstable. At that point, there are only two things preventing the woofer to destroy itself:

1. The electrical damping factor of the amplifier circuit. Don't count on this to be of much help, especially with today's "d-class" amplifiers.

2. Time. This is the biggest factor. Anything more than a few seconds with a woofer running at near excursion capabilities will destroy your speaker.

Here is a test to visually see exactly what I am writing about:

Go out to your car, and queue up a test tone cd at VERY LOW VOLUME. Turn to the track on the cd with a test tone at or around 20-25 cycles, and watch your woofers. See how much further in and out they travel? That is because the entire system is unstable.

PREVENTION: If your amplifier has a subsonic filter, adjust it a few cycles under whatever your woofer enclosure is tuned to. This will prevent damaging information from ever reaching your woofer system. If you do not have a subsonic filter and you run a ported enclosure, you really need to buy one. If you do not, then you must be very careful with test tone and "bass" cds.

I hope this cleared up some of the confusion I am seeing with regards to this issue. I keep seeing threads with everyone saying that amp clipping is the cause of bad smelling woofers, but most of the time this is not the case. The distortion and clipping issue has probably been beaten to death on this board, but I will comment on it if everyone would like to hear more.

Click to read more...

 

[Maxipads 10+ year member]

Where can i buy a subsonic filter? Im new sorry im making my way through the bass world learning as i go //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[toaster 10+ year member]

Use Google, and you will find many different brands. Just buy a reputable brand and you will be ok. A word of caution, however: Make sure you get an active filter, not a passive. An active filter will be powered with 12 volts from your vehicle's electrical system.

 

[cx-7heaven 10+ year member]

99% of newer amplifiers already have a subsonic filter built in. Check your amp first before spending more money, or if you are a complete noob and dont know your gear, just post up what you have, and someone will tell you.

 

[Maxipads 10+ year member]

LOL i just looked in my truck and at my amp... Subsonic Filter dial right in my face.. im blind .. well the dial goes from 35 to 15 and id say its on like 20 or 21 hz now cause i just turned it down

 

[cx-7heaven 10+ year member]

LOL i just looked in my truck and at my amp... Subsonic Filter dial right in my face.. im blind .. well the dial goes from 35 to 15 and id say its on like 20 or 21 hz now cause i just turned it down

You need to find out what your system is tuned to, before you turn anything up or down. If you are tuned to 35, and you just turned the dial to 15, you are turning it too low, and could damage your setup.

 

[Maxipads 10+ year member]

My system is tuned to 30.3 hz. so if i put it at 20 would that be bad?

 

[ahole-ic]

You want it very near your actual tuning frequency. Put on right below 30 and you'll be fine.

 

[Maxipads 10+ year member]

alright thankss

 

[T3mpest 10+ year member]

Playing below tuning does not damage the power handing of a woofer, at least not thermally. If your smelling a subwoofer it's not because it's moving too far, it's because it's getting too much power and getting too hot. If your going over the RMS of the coil or even near it well below tuning your likely to break a speaker mechancially first. Power handling is a two factored idea, mechanical and thermal, only thermal is listed as mechanical depends upon the application. Smelling a woofer is indicative of a power issue...

 

[hatedonmostly 5,000+ posts]

Nice post, OP.

 

[surreal 10+ year member]

So if your box is tuned to 35, would the SSF at 30 be too low? Or 33 about ideal?

 

[T3mpest 10+ year member]

Depends how much power your putting to it and what box size as well as tuning. Best bet it to model it in a program and see where your sub will meet it's mechanical limits. Again these limits are mechanical and have nothing to do with why coils stink, well at least not directly. Everyone on this forum tunes at 35hz because they want a loud enclosure. People who tend to like things loud tend to own large amplifiers and put alot of power on subs. THis leads to coil stink being common, especially with most of the forum agreeing that sub "x" will take 2x RMS all day long.. Also power is really cheap nowadays, people can spend 300 dollars on two entry-mid level subs and for another 300 get 2500watts of power to put on their tiny little 2"coils, then they wonder why the stink lol.

 

[toaster 10+ year member]

Playing below tuning does not damage the power handing of a woofer, at least not thermally. If your smelling a subwoofer it's not because it's moving too far, it's because it's getting too much power and getting too hot. If your going over the RMS of the coil or even near it well below tuning your likely to break a speaker mechanically first. Power handling is a two factored idea, mechanical and thermal, only thermal is listed as mechanical depends upon the application. Smelling a woofer is indicative of a power issue...

While partly true, you cannot separate thermal and mechanical power handling. Both are a function of the moving mass of the motor, plus the inductance produced by moving the coil through a magnetic field. While they are on paper separate, when placed together the only way to separate them is by removing one or the other.

As far as modeling a woofer system in a software environment, remember that, unless you have an accurate model of your particular application, it will not mean anything once it goes into a vehicle. Placing a woofer system into a vehicle adds another order of resistance, loss, and gain to the system. When speaker modeling software first came out, we discovered quickly that while it helps to plot how the system will behave with regards to tuning and resonance, it cannot predict with any accuracy how it will behave in a vehicle. Many times, something that looked good on a PC screen performed poorly in an automotive environment, and vise-versa.

 

[T3mpest 10+ year member]

While partly true, you cannot separate thermal and mechanical power handling. Both are a function of the moving mass of the motor, plus the inductance produced by moving the coil through a magnetic field. While they are on paper separate, when placed together the only way to separate them is by removing one or the other.
As far as modeling a woofer system in a software environment, remember that, unless you have an accurate model of your particular application, it will not mean anything once it goes into a vehicle. Placing a woofer system into a vehicle adds another order of resistance, loss, and gain to the system. When speaker modeling software first came out, we discovered quickly that while it helps to plot how the system will behave with regards to tuning and resonance, it cannot predict with any accuracy how it will behave in a vehicle. Many times, something that looked good on a PC screen performed poorly in an automotive environment, and vise-versa.

Yes, but mechanical and thermal limits of a driver are very often 2 different power values, within a given range of frequencies. If your smelling a subwoofer burning, it's not because the cone is moving too far, it's because it's seeing to much power. While a SSF can help this by taking away some of the power as well as limiting excursion that may very well be damaging the woofer, it's not the key issue. As a matter of fact it's almost the opposite. You tune a sub at box at 45hz and run 10hz tones through it all day and NEVER smell coils burning. Unless your woofer has the stiffest suspension known to man your going to bottom it out and damage the suspension first. Simply modeling where a you need to set a SSF with a modelling program is fairly reliable unless you have your system sitting very close a wall. Worst case it gives you a good starting point as you can see how fast you run out of xmax below tuning.

I agree that with many companies recommending high tunings for their sub that a LPF is a necessity, however I dont' feel ti's why people are complaining of coil stink. That's simply too much power at any frequency and the gains need to be lowered.