# Fighting Boominess



## jtavrisov (Jul 5, 2010)

So I'm currently running a IDQv2 12" in a '00 Subaru Forester in a 1 cubic foot sealed box.

With some songs, mostly rock side stuff, the drum is very tight and hard hitting. Very enjoyable. Then I might get a hip hop song up on my play list and get this loud boom sound. Very over powering very annoying. 

Anything I can do to dimish this boomy sound. I'm going to get an accident soon if I keep having to change the sub level for every song.


I currently have it crossed over at 80hz with a 12db/oct (?I'm assuming these units?) slope


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## Danometal (Nov 16, 2009)

Rap aims for that kind of response, IMO. I wouldn't worry about it, unless you want to adjust bass/sub levels when those songs come up. Other than that, a bigger box might help.


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## jtavrisov (Jul 5, 2010)

I suppose it does but I was hoping to reduce the boominess and not really the volume. Make it sound tighter.

I have some songs where I can't hear the actual rap compared to that awful sound. I guess I'm just used to my flat headphones with very (but accurate) bass.


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## Oliver (Jun 25, 2007)

jtavrisov said:


> So I'm currently running a IDQv2 12" in a '00 Subaru Forester in a 1 cubic foot sealed box.
> 
> With some songs, mostly rock side stuff, the drum is very tight and hard hitting. Very enjoyable. Then I might get a hip hop song up on my play list and get this loud boom sound. Very over powering very annoying.
> 
> ...


Try adding ziploc baggies filled with sand 

The low notes are hitting near the resonant frequency of your speaker , which equals overshoot on the subs part 

Loss of control - it keeps moving and moving ... even after the signal is long gone that made it move in the first place



> My favorite Tom Nousaine-isms
> 
> 
> 1)Every ME review : ...Torch Red 2001 Corvette.
> ...


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## jtavrisov (Jul 5, 2010)

ooo now we are getting into interesting territory.

So why sand? I assume the goal is to absorb some of that energy, wouldn't something else work better.


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## Danometal (Nov 16, 2009)

a$$hole said:


> Try adding ziploc baggies filled with sand
> 
> The low notes are hitting near the resonant frequency of your speaker , which equals overshoot on the subs part
> 
> Loss of control - it keeps moving and moving ... even after the signal is long gone that made it move in the first place


Polyfill has always helped my subs to avoid doing that, IMO. I guess standing waves can possibly cause an undesirable boominess.


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## Volenti (Feb 17, 2010)

Danometal said:


> Polyfill has always helped my subs to avoid doing that, IMO.


Ding Ding Ding we have a winner! polyfill will damp the resonance of the driver and help prevent a boomy sound. However foresters have a natural peak in the _car's_ cabin gain at 50hz, and guess where rap/hop hop have a lot of their bass centered around...

Standing waves aren't an issue for bass in most enclosures, especially a small 1cuft sealed enclosure.


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## Danometal (Nov 16, 2009)

Volenti said:


> Ding Ding Ding we have a winner! polyfill will damp the resonance of the driver and help prevent a boomy sound. However foresters have a natural peak in the _car's_ cabin gain at 50hz, and guess where rap/hop hop have a lot of their bass centered around...
> 
> Standing waves aren't an issue for bass in most enclosures, especially a small 1cuft sealed enclosure.


I wonder if he were to make a larger box could that help lower the F3 of the subwoofer/enclosure below the resonant peak of that vehicle, thus reducing boominess (along with adding 1 lb/cube polyfill).


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## kyheng (Jan 31, 2007)

That's why I love sealed enclosure...
Adding polyfill is great, but when overdone, it cause more problem such as it cause the sub to lost its compressions.


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## Danometal (Nov 16, 2009)

kyheng said:


> That's why I love sealed enclosure...
> Adding polyfill is great, but when overdone, it cause more problem such as it cause the sub to lost its compressions.


Polyfill BRAND is important also. The other brand at Walmart actually seems to choke the sub a bit in my experience. Polyfill brand maintains its airy consistency when stuffed. Also, 1 lb/cube volume is a failproof formula, IMHO.


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## kyheng (Jan 31, 2007)

For me, there's no such thing as failproof formula, especially for sub enclosure's constructions. 
I don't know, but when I'm constructing the enclosure, I will get the "perfect" size for it.


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## Danometal (Nov 16, 2009)

kyheng said:


> For me, there's no such thing as failproof formula, especially for sub enclosure's constructions.
> I don't know, but when I'm constructing the enclosure, I will get the "perfect" size for it.


I hear you.  That formula has just been consistent with my successful enclosures. And, man do I wish I would've had WinISD back in the day!!

So, do you think a larger stuffed box could help the OP's vehicle resonant frequency's juxtaposition with the F3 of the enclosure, assuming that's what's occurring?


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## kyheng (Jan 31, 2007)

From my point of view, nope. I've tried my woofer on a 50liter sealed(which should be ported) and the result were not that good. Putting more polyfills make it worst. As for me, ported will be the best(provided enclosure is done right)
From my very noob experience, we put polyfill is to make the enclosure "bigger". While getting a bigger enclosure do help to improve bass response, but too big may cause the sub to lost its compression which you will get the unwanted boom....


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## Volenti (Feb 17, 2010)

kyheng said:


> From my very noob experience, we put polyfill is to make the enclosure "bigger". While getting a bigger enclosure do help to improve bass response, but too big may cause the sub to lost its compression which you will get the unwanted boom....


No No No, The _primary_ effect of fill is resistive damping, there is a _small_ secondary effect that makes the enclosure appear _slightly_ larger to the driver but it's minor enough to be ignored in most cases, this is formed from imperical observation and measurement, not opinion.

Case in point, I can lower the effective QTS (ie how resonant it is) of a driver in an enclosure with polyfill to a level _below_ what that driver is in free air (normally a driver in a sealed enclosure will always have a higher QTS then free air) This would be impossible if fill just "made the box appear larger".

The damping effect is also why in some suitations it will "suck the life" out of a driver, especially if it's already well damped to begin with.

Sometimes you want lots of fill, sometimes just a little, sometimes none, enclosure design is loaded with compromises, fill is simply another one.


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## Oliver (Jun 25, 2007)

Nousaine.com - The Archived Works of Tom Nousaine

Random articles from Tom Nousaine ^^^^




> Output falls below the system's resonant frequency (Fs), defined as the frequency of peak impedance. In a closed-box, the air inside the box acts as a spring, returning the cone to the 'zero' position in the absence of a signal. There may be an increase in output at the resonant frequency. The enclosure may be entirely empty, lined, filled or packed tightly with damping material, generally polyester foam, bonded acetate fibre (BAF) also known as pillow stuffing, fibreglass, or long fibre wool, which absorbs internal reflections, and changes the thermodynamic properties of the enclosed air mass from adiabatic to isothermal, making the enclosure behave as though it were slightly larger. The enclosure or driver must have a small leak so internal and external pressures can equalise over time, to compensate for barometric pressure or altitude. The porous nature of paper cones is sufficient to provide this slow pressure equalisation.





> putting polyfill in a subwoofer enclosure isnt necessarily about decreasing the internal volume. in fact, its maybe the easiest way to "increase" the volume. it actually alters the rate that the air inside the box changes temperature. lets use a sealed box as an example-
> 
> when your cone is at rest, the pressure inside the box is considered ambient. when the cone goes in, the pressure inside the box goes up. when you pressurize air, the temperature goes up. when the cone goes out, the pressure inside goes down, and temperature goes down. we're not talking about a couple of degrees, its generally a very small temperature change.
> 
> ...





> Fibrous tangles are frequently used in loudspeaker enclosures to damp acoustic resonances that might otherwise occur. However, in addition to their attenuating properties, fibrous tangles also reduce the propagation speed of the sound waves, and this could also be used to reduce the dimension of enclosures.


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## Oliver (Jun 25, 2007)

> Tom Nousaine did a real nice analysis a while back. I saved the page (thank goodness since the old link is now dead). There's a bit of formatting lost, but here goes . . .
> 
> 
> 
> ...


Great Article here ^^^^


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## Volenti (Feb 17, 2010)

The above article is a great example of someone not seeing the forest for the trees, yes the thermal effect is a real thing, but when you assume that is all that is happening with fill you fall into the trap of coming to a conclusion for the wrong reasons.



> With all three boxes, I enjoyed roughly 25 to 35 percent of "space gain" by using stuffing at a rate of 1 to 1.75 pounds per cubic foot of internal volume


Incorrect, there is no such thing as a free lunch, the 3 boxes had thier impedance curves altered (by the presence of the fill) to be kind of similar to the impedance curve of a larger enclosure (as a model, not an actual measurement), however when you actually build and measure the larger enclosure you find that;

1. you can't actually get the 2 impedance curves to come close to matching up, since there's a very large resistive damping component that's ignored.
2. the larger enclosure is more efficient, always

So yes you can make a small enclosure sound kinda like a larger one, but at a signifigant efficiency cost.


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## kyheng (Jan 31, 2007)

^Well, do people care about thermal issues nowadays? I don't see they do. Because by using a sealed enclosure, is there a way to cool the voice coil down? It is good that when the sub failed because of voice coil overheated. Atleast the user need to get another sub. Will the warranty cover the sub on such failure?

If a sealed enclosure are really that superior, home active sub already using such enclosure, but I've yet to see such sub.


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## Oliver (Jun 25, 2007)

Volenti said:


> Incorrect, there is no such thing as a free lunch, the 3 boxes had thier impedance curves altered (by the presence of the fill) to be kind of similar to the impedance curve of a larger enclosure (as a model, not an actual measurement),* however when you actually build and measure *the larger enclosure you find that;
> 
> 1. you can't actually get the 2 impedance curves to come close to matching up, since there's a very large resistive damping component that's ignored.





> To evaluate the effectiveness of box stuffing, *I used an MLSSA analyzer to measure the impedance of three enclosures *– 5.l-cubic-foot sealed, 1.4-cubic-foot sealed, and 1.4-cubic-foot ported (the port measured 3 inches in diameter and 6 inches in length) – with various densities of stuffing. For the sealed boxes, I was able to determine the effective box size – as enhanced by the stuffing – using the system's resonant-frequency and Qes values. For the ported box, I compared the tuned frequency of the empty enclosure to the tuned frequency of the stuffed enclosure, using the Speak for Windows computer program; this enabled me to find the effective box size that fit the actual resonant frequency I'd measured.


dra laboratories- mlssa acoustic measurement system
Description
_MLSSA by DRA Laboratories is the loudspeaker industry's standard measurement system._ *MLSSA is also used by automakers, recording studios, acousticians and government agencies to measure sound systems, room acoustics and speech intelligibility.*

The MLSSA Remote Controlled Analog Interface (RCAI) is now available. The RCAI allows you to perform both frequency response and impedance measurements of loudspeakers without pausing to switch cables or change the MLSSA setup. Impedance and frequency response curves can be displayed and printed together on the same graph. Reference loopback measurements of even the highest powered amplifiers are performed automatically and safely. The RCAI also includes a four-input microphone multiplexer for automated spatially averaged room measurements. Up to four units can be daisy chained to expand the number of inputs and/or power amplifiers supported by a single MLSSA 2000 card.


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## Volenti (Feb 17, 2010)

Once again, if the article is correct, then you could build a 1cuft ported enclosure, stuff it with the recommended quantity of fill and not only would it sound the same as a 1.4cuft enclosure tuned to the same frequency, it would have the same efficiency too, this is not backed up by the imperical data.

Don't believe me? build the enclosures and see for your self.


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## kyheng (Jan 31, 2007)

^^^I don't know, but it seems like you are good on enclosure design. Any solid fact to support your statements? 

I'm a simple guy and prefer to use simple terms to elaborate a thing. But I also like to see people using some technical terms but at the end, it is still doing the same thing. Example, I want to buy a can of diet coke which the store is 10 step from my house, I just walk the 10 steps and buy the coke. But you like to walk few miles which go round the neighbourhood first and go to the same store and buy a can of diet coke....


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## ncv6coupe (Oct 25, 2009)

i agree with both volenti and noussaine, they just word it from two different understandings but they are in the same boat, if i may add though, adding fill will RAISE the f3 of the enclosure but you get more low end by doing so and boominess is a subjective term depending on what frequency range you are talking about for subs which i assume the op may be talking about 35-55 range for rap


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## illinja (Jun 13, 2010)

I've been struggling with this a little myself lately as Ive got a new car and system. 

I don't know if it was mentioned but your crossover setting is high for a 12db/oct slope. That means your getting a lot of overlap in the midbass area and possible ringing (harmonics) from the sub..

try either 

- Lowering the x-over to 50hz 12db/oct
- Switch x-over to 70-80hz 24db/oct. 


Also, the Rap source material is accentuated in the low bass notes, while rock isn't (usually). Best bet is to tune your system for rock music first off, because it is more demanding from a tuning perspective (read SQ) then just listen to your hip hop stuff with an attenuated setting on the sub.


my 2 cents.


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## jtavrisov (Jul 5, 2010)

I'll try lowering the crossover point to 50hz. My HU doesnt do 24db/oct but I think i can do 18db/oct.

Also while I'm on the subject. Where should I cross my components at. They are a passive set so I cross them all at the amp.


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## Oliver (Jun 25, 2007)

listen for popping sounds when they're cranked up very loud.

raise the x-over until it sounds good and doesn't make strange noises


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## jtavrisov (Jul 5, 2010)

This is my last weekend before classes start back up, got lots to do. Still have wires showing on one of my amps, got banana plugs to hook up to my speaker box, and install the deadener I bought.

Oh and finally tune the damn thing. I think part of the boominess is due to my comps being crossed over to low. I think i have them high passed lower than my sub is low passed.


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## sqshoestring (Jun 19, 2007)

Most comps don't produce much below 80Hz anyway. What you can do is make a tone CD, you can download them and burn one. Then play tones and find out what frequency is making this boom. Find out if it comes from the subs and/or mids. You might try running your xover near that and running the subs out of phase if you can't tune your box differently. Can you EQ it out, you could get hold of a parametric EQ they can take booms out.


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## illinja (Jun 13, 2010)

first off listen to the components only (subs off) while tuning them, make sure your rear speakers are off/gone.

start with a low HPF x-over like 60 or 70hz, listen to music with punchy snappy mid-bass and some with deeper bass (or both if you have a song like that) turn it up till its as loud as you'll ever want to listen. At 70 hz x-over there will likely be distortion when the bass hits, now turn up the x-over till you no longer hear that distortion. you might end up around 80-100hz. 

once you have that set properly you can go ahead and blend in the sub. you dont need LPF x-over to meet up at the same number, Ive always found a gap of 10-20hz is helpful for blending. But you can tune to your tastes. Also make sure your sub gain isn't set uncharacteristically high(loud) or it wont blend. If you want to use that 12db/oct slope definetly use a gap between the LPF and HPF points. I personally find that 12/db oct slopes blend better than 24/db for pure sq use. but the 24db/oct slope acts more like a wall and allows you to have a higher crossover point without the bass pulling to the rear.

Also, after you tune it listen to the system for a while without fiddling(very difficult!), your ears may need to adapt to any new settings. Try lots of different material to decide if it sounds good in general. usually there is not perfect setting for all types of music, some times you gotta compromise.

hope it helps.


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