low notes = sub excursion = no bass?

[SRim23 5,000+ posts]

At Fb your woofer is optimally damped, in a ported enclosure, so the woofer moves very little, it can take a crap load of power (mechanically), and the port does most of the work.
As soon as you go below Fb however, your woofer starts to act as if it's in free air without any box at all. It begins to flop around and loses significant power handling capability. This is why sealed boxes are generally used for the absolute lowest frequencies.

To be quite honest, there's not much real music below 30hz, so what are you trying to play that's creating an issue? 32Hz is probably a fine tuning for most music, to keep a mix of sound quality and spl.

alot of people seem to be suggesting sealed to fix this problem but my last 2 sealed boxes ive had this problem on test tones. 34hz and below the cone just moves alot but you really cant hear anything.

subsonic at 27hz...make sure your not using 2 or more LP filters on your sub...use only one and set around 80hz.....prob should be solved if gains are set properly

if you are coming out the sub jacks on the deck...make sure it is set for through/full ...most pioneer decks there is no way of doing that on the sub jacks...and a lot of mono amps you can't turn off the crossover....so that gives the amp a potential of 2 LP signals that it could see....

this is the first time ive heard you should only use 1 filter. ill have to try that when i get my new subs installed. i always figured it couldnt hurt to use both.

does the same apply for your components? should you only use 1 hpf ? what does it hurt to use 2 filters?

 

[bass-aholic 10+ year member]

...

 

[bladebarrier 10+ year member]

alot of people seem to be suggesting sealed to fix this problem but my last 2 sealed boxes ive had this problem on test tones. 34hz and below the cone just moves alot but you really cant hear anything.



this is the first time ive heard you should only use 1 filter. ill have to try that when i get my new subs installed. i always figured it couldnt hurt to use both.

does the same apply for your components? should you only use 1 hpf ? what does it hurt to use 2 filters?

You're obviously looking to get to the next level of understanding. PM me, if you want, and I'll answer all the questions I can answer, or refer you to where you can go for more info.

You're starting to get into deeper acoustic theory, and I might be able to explain in better detail if I have more time between responses, to explain the physics of it.

Some of the posts here are not correct (including those that have many thousands of posts), and they may screw up the concepts that you seem to be right on the edge of getting fully.

 

[bladebarrier 10+ year member]

might need to turn the ssf up some. more like 5 below

This, and then some. if your box is tuned to 32hz, set your ssf closer to 30hz, check the excursion, and adjust as needed.

If you hate it, you can say I don't know what I'm talking about, in the forums, but I bet you'll get a better result overall.

Tune low, cross low, ssf at just below Fb, for clarity.

If you want spl, go bandpass, and call it a day.

If you want depth, go sealed, and call it a day.

If you want in between, go ported (best design for most music), but accept it's the middle ground.

 

[Louisiana_CRX 5,000+ posts]

alot of people seem to be suggesting sealed to fix this problem but my last 2 sealed boxes ive had this problem on test tones. 34hz and below the cone just moves alot but you really cant hear anything.



this is the first time ive heard you should only use 1 filter. ill have to try that when i get my new subs installed. i always figured it couldnt hurt to use both.

does the same apply for your components? should you only use 1 hpf ? what does it hurt to use 2 filters?

using multiple crossovers can cause phase and slope issues along with freq. dips...you slope will actually get steeper if your freq is matched perfect....say deck is a 12db slope amp is a 12 db slope you'd end up with a 24 db slope.....or an amps 24 and the deck is 12 you'll get a 36db slope....if the freqs arn't matched precisely it will cause dips in the freq ....and again possible phase issues.....that is why its best to only use one crossover....more user friendly

 

[BlurredVision 10+ year member]

Some good shit in this thread. I'm in learning mode.

 

[SRim23 5,000+ posts]

using multiple crossovers can cause phase and slope issues along with freq. dips...you slope will actually get steeper if your freq is matched perfect....say deck is a 12db slope amp is a 12 db slope you'd end up with a 24 db slope.....or an amps 24 and the deck is 12 you'll get a 36db slope....if the freqs arn't matched precisely it will cause dips in the freq ....and again possible phase issues.....that is why its best to only use one crossover....more user friendly

so as long as my HU has hp crossover and slope adjustment i should just turn my crossover on my amp off? might try that

 

[justin smith 10+ year member]

could have air leaks in youre box

 

[bladebarrier 10+ year member]

might need to turn the ssf up some. more like 5 below

THIS

could have air leaks in youre box

You can have all the air leaks you want, after you dip below Fb, you have the biggest air leak on the planet.

A vented enclosure is sealed untii it approaches Fb, then it becomes extremely damped, then below Fb it's free air.

He seems to be doing ok above the Fb, so it's below that's the issue.

 

[bladebarrier 10+ year member]

using multiple crossovers can cause phase and slope issues along with freq. dips...you slope will actually get steeper if your freq is matched perfect....say deck is a 12db slope amp is a 12 db slope you'd end up with a 24 db slope.....or an amps 24 and the deck is 12 you'll get a 36db sope....if the freqs arn't matched precisely it will cause dips in the freq ....and again possible phase issues.....that is why its best to only use one crossover....more user friendly

He's flopping around below his port tune. WTF does a deck x-over have to do with anything?

Also, while audioholic explained it pretty well, he didn't fully cover why your woofer is flopping around. Like everyone said before, you're playing notes below Fb.

If you really want to try something different, and get the lowest bass, while trying to maintain the gain from a ported, **** around with transmission line setups. They are huge, bigger than bandpass often, but they allow you to stay damped below the tuning frequency and still give the gain of a port (albeit less than a normal vented). If you get a transmission line right, you get the sq and depth of a sealed, but the boost of a ported. The trick is, it's ****ing hard to do.

 

[Fique 10+ year member]

my sub will do that in a sealed enclosure. the bass that low is barely audible, but it shakes the hell out of my truck!!

I hear polyfill makes your box "seem" bigger? Does this help?

 

[bladebarrier 10+ year member]

my sub will do that in a sealed enclosure. the bass that low is barely audible, but it shakes the hell out of my truck!!
I hear polyfill makes your box "seem" bigger? Does this help?

Polyfill, or any synthetic fill (dont' use fiberglass wadding like they used years ago), can increase the box size by about 10-15%, depending. In a sealed enclosure, you usually always stuff it, but make sure the fill isn't blocking the rear of the magnet, or touching any wiring. Sometimes I see people stuff boxes with the woofer, and they don't realize the hole in the back of the magnet is for venting the temperature.

1lb per cubic foot, and staple it with a staple gun, to the side. Any fill behind the woofer magnet should be pushed away to let the woofer breathe. Also, keep fill away from the tinsils' and such.

It's good to use fill, but keep it away from your motor/tinsil.

 

[Fique 10+ year member]

Not to thread jack, but what do you think I would gain from stuffing? Im in a 6 cube sealed now. Spec'd at 4-8 cubes.

 

[audioholic 5,000+ posts]

my sub will do that in a sealed enclosure. the bass that low is barely audible, but it shakes the hell out of my truck!!
I hear polyfill makes your box "seem" bigger? Does this help?

If it 'shakes the hell' out of your truck, why do you think there is a problem?
Again I think its being ignored that the lowest octaves are, quite naturally, inaudible to the human ear.

In other words, stuffing your enclosure with polyfil will not decrease the wavelength of a 20hz note, nor will it affect ear's ability to hear this note... in a small car or a large concert hall.

 

[bladebarrier 10+ year member]

Not to thread jack, but what do you think I would gain from stuffing? Im in a 6 cube sealed now. Spec'd at 4-8 cubes.

If you're running a sealed, you can gain 10-15% in volume, by stuffing.

About 1 lb of fill per 1cu3 is normal. It can also increase transients and reduce standing waves. It also doesn't reduce the dampening. Fill makes a box appear larger because the fill heats up, which causes sound waves to slow down.

If you run a sealed, you should always fill.