# Tuning a subwoofer enclosure



## primetimetsa

Exactly what is being done when you tune a box to a certain frequency? What does it mean? If a box is tuned to 30Hz, what happens when your speakers hit 30Hz? Does the world implode? How do you decide what frequency to tune your box at?


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## PorkCereal

You want to research ported boxes. Those are the only boxes you can tune to a certain frequency. Basically its a hole with a tube a certain length and diameter.


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## johnmasters

When you drive your speaker below the tuning frequency the port allows the driver to unload so that it can move much more in each direction with less power thus making it very easy to push the driver past its mechanical limit. You'll notice in SQ people will tune their box to a low frequency like 28 or 30 and and very rarely run there sub below that frequency so the driver rarely unloads. In SPL people will tune their box to a higher frequency like 40 and run their sub below the tuning frequency ALOT, moving more air and thus sounding LOUDER yet worse.

I like to think about it like the redline in my RX7. My car LOVES to travel just below the redline. That is where I see the best performance in this car and as I approach redline things just get better and better. The redline is your tuning frequency and the closer you drive to that frequency the better your driver performs yet when you pass the redline you have entered a territory where the mechanical and thermal limits are being pushed closer to the max and your performance begins to degrade.

So the answer to your question is NO, the world will not implode if you push your driver past the tuning frequency but if you do it to much your driver may explode.

Keep in mind... I still have yet to experience a ported enclosure in the car. Hopefully not for long


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## primetimetsa

Answered my question perfectly, thanks dude.



johnmasters said:


> When you drive your speaker below the tuning frequency the port allows the driver to unload so that it can move much more in each direction with less power thus making it very easy to push the driver past its mechanical limit. You'll notice in SQ people will tune their box to a low frequency like 28 or 30 and and very rarely run there sub below that frequency so the driver rarely unloads. In SPL people will tune their box to a higher frequency like 40 and run their sub below the tuning frequency ALOT, moving more air and thus sounding LOUDER yet worse.
> 
> I like to think about it like the redline in my RX7. My car LOVES to travel just below the redline. That is where I see the best performance in this car and as I approach redline things just get better and better. The redline is your tuning frequency and the closer you drive to that frequency the better your driver performs yet when you pass the redline you have entered a territory where the mechanical and thermal limits are being pushed closer to the max and your performance begins to degrade.
> 
> So the answer to your question is NO, the world will not implode if you push your driver past the tuning frequency but if you do it to much your driver may explode.
> 
> Keep in mind... I still have yet to experience a ported enclosure in the car. Hopefully not for long


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## pirate

primetimetsa said:


> Exactly what is being done when you tune a box to a certain frequency? What does it mean? If a box is tuned to 30Hz, what happens when your speakers hit 30Hz? Does the world implode? How do you decide what frequency to tune your box at?


This affects the frequency response of the speaker.
Around the tuning frequency, you get an increase in the output.
If the box is tuned to 30Hz, there will be increased output at this frequency. The driver will appear not to move as the output will be coming from the port.
Below the tuning frequency the driver will begin to unload (behave as though it it not in a box). The extent will be determined by how much power and lower the driver is pushed.
The tuning frequency, type of box etc... can be determined by the T/S parameters of the driver.


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## dougc

Great responses - thanks for the knowledge. So tuning to the "correct" hz for the speaker in relation to the enclosure will cause the amp to run cooler - most efficiency?


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## TheRealSpinner

Personally, I don't like ported boxes (or band pass boxes) but that's because I prefer sound quality. With tuned, ported boxes, the response curve will have a spike at the tuned frequency.  That means that it will be unusally louder at that frequency.

That's why, when going for SPL, they tune a box to a frequency that a subwoofer is also tuned to. When listening to music, if you like boom, boom, boom, go for ported, but if you like smooth response musical quality, go with a sealed enclosure.


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## 89grand

Just to set the record straight for those that may not know, if a ported box is tuned to 30hz, the driver does not unload at 29hz. It's incremental so the lower you go below 30hz the more it starts to unload. The driver may not be completely unloaded until 15hz for example.

Another myth that is already starting is that ported boxes sound bad and sealed is for SQ. That's ridiculous and untrue. A ported enclosure, if tuned properly can sound just as good if not better than a sealed box. It's free bass really because a ported box is much more efficient at and around the tuning frequency. They also offer lower distortion and roll off slower than a sealed enclosure.


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## 89grand

I was corrected on my post. I worded it wrong. Roll off is a lot lower with a ported enclosure, but the roll off is steeper with a ported enclosure at the enclosures F3.

A sealed enclosure rolls off at 12db per octave below it's F3, while a ported enclosure rolls off at 24db below F3. The difference is the sealed enclosures F3 might be 50hz, whereas the ported enclosure is typically around 30hz.


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## xb_guy

johnmasters said:


> When you drive your speaker below the tuning frequency the port allows the driver to unload so that it can move much more in each direction with less power thus making it very easy to push the driver past its mechanical limit. You'll notice in SQ people will tune their box to a low frequency like 28 or 30 and and very rarely run there sub below that frequency so the driver rarely unloads. In SPL people will tune their box to a higher frequency like 40 and run their sub below the tuning frequency ALOT, moving more air and thus sounding LOUDER yet worse.
> 
> I like to think about it like the redline in my RX7. My car LOVES to travel just below the redline. That is where I see the best performance in this car and as I approach redline things just get better and better. The redline is your tuning frequency and the closer you drive to that frequency the better your driver performs yet when you pass the redline you have entered a territory where the mechanical and thermal limits are being pushed closer to the max and your performance begins to degrade.
> 
> So the answer to your question is NO, the world will not implode if you push your driver past the tuning frequency but if you do it to much your driver may explode.
> 
> Keep in mind... I still have yet to experience a ported enclosure in the car. Hopefully not for long


Great explaination; what I'm wondering about though is how you guys decide *what frequency* to tune for. I understand that an SPL competitor would tune to the resonant frequency of their vehicle (for more output), but what about us "normal" folks just wanting to hear some tunes and bump some beats...


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## Dryseals

In the old days, we tuned a box to a few HZ below the resonance of the speaker. We shot for a flat response. So if the speaker had an Fs of 30HZ we'd tune the box for a few HZ down, say 25. This moved the Fs of the system down a little.

Since Fs is normally louder than the true response, you can tune above to get a higher SPL, but the sound reproduction quality will be far less. It's all a matter of what you are shooting for.

It really has more to do with the response curve of the speaker at Fs, some are wide and some are narrow, and how do you want the speaker to perform. It's a useful fudge factor to get what you want.


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## 89grand

I recommend lower tuning for a good sounding everyday system. Somewhere between 28-32hz.


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## johnmasters

These are all of the reasons why after purchasing my 2nd DIYMAr12 about 6 months ago, I still cant decide whether to build a sealed fiberglass enclosure to house both DIYMAs or to build a ported FG enclosure for the single DIYMA and save the other one for home theater.

I listen almost exclusively to electronic/techno type music so sealed does work good and I imagine that building a strangely shaped FG ported box and getting all of the parameters exactly right would be difficult but I sure am curious to hear what a well built and tuned ported enclosure sounds like with the correct driver.


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## BubbaBoBobBrain

Wow! This is all so far over my head. Im probably going to sound like an idiot but how do I know what type of box to get for my sub. What do I look for? Does it go by the range the sub can handle or not. For example the sub I am about to get has a range of 20hz-2200hz
so what type of box should I get. I kind of want a ported box but now you guys got me nervous about what type of box to get. HELP!


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## BubbaBoBobBrain

I also forgot to mention that the sub is a 2000watt peak 1000watt rms dual voice coil sub and my amp is an 1800watt class d mono block kenwood if that helps any.


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## XtremeRevolution

dougc said:


> Great responses - thanks for the knowledge. So tuning to the "correct" hz for the speaker in relation to the enclosure will cause the amp to run cooler - most efficiency?


It won't run cooler. It will just be louder for the same amount of power. Expect gains from 3-8db, typically. 



89grand said:


> Just to set the record straight for those that may not know, if a ported box is tuned to 30hz, the driver does not unload at 29hz. It's incremental so the lower you go below 30hz the more it starts to unload. The driver may not be completely unloaded until 15hz for example.
> 
> Another myth that is already starting is that ported boxes sound bad and sealed is for SQ. That's ridiculous and untrue. A ported enclosure, if tuned properly can sound just as good if not better than a sealed box. It's free bass really because a ported box is much more efficient at and around the tuning frequency. They also offer lower distortion and roll off slower than a sealed enclosure.


Its not ridiculous our untrue, as many of them do sound bad, and there are some subs that you can't make sound good in a ported box no matter what you do. Group delay at that point will determine how accurate your sub will sound. As for lower distortion, it depends on the sub and box design. You might think the distortion is lower near the tuning frequency because your excursion is lower due to the port controlling the cone, but you also have to remember that whenever there is augmented output by way of a port, passive radiator, or bandpass alignment, it is *always* accompanied by a delay. One cannot generalize in either case until the sub box is modeled. 



xb_guy said:


> Great explaination; what I'm wondering about though is how you guys decide *what frequency* to tune for. I understand that an SPL competitor would tune to the resonant frequency of their vehicle (for more output), but what about us "normal" folks just wanting to hear some tunes and bump some beats...


You decide what frequency to tune for based on how your sub models in software. 



BubbaBoBobBrain said:


> Wow! This is all so far over my head. Im probably going to sound like an idiot but how do I know what type of box to get for my sub. What do I look for? Does it go by the range the sub can handle or not. For example the sub I am about to get has a range of 20hz-2200hz
> so what type of box should I get. I kind of want a ported box but now you guys got me nervous about what type of box to get. HELP!


See the first link in my signature. I model/design sub boxes for many people here.


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## BubbaBoBobBrain

Thanks for the reply, but I don't understand 99% of this stuff. Until today I never heard of a tuned box. I have always bought subs that came in boxes or just threw subs in a box I already had. Im not new to systems, I just don't know the technical stuff. All I have ever done is much up watts for amps and subs. If you could tell me what type of box I should use for the sub I am about to buy to make it sound best I will trust your decision, considering you know WAY more about this than I do. If you want I will give you the sub model and whatever else I can and we can go from there. Any help you can give me would be appreciated.


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## XtremeRevolution

BubbaBoBobBrain said:


> Thanks for the reply, but I don't understand 99% of this stuff. Until today I never heard of a tuned box. I have always bought subs that came in boxes or just threw subs in a box I already had. Im not new to systems, I just don't know the technical stuff. All I have ever done is much up watts for amps and subs. If you could tell me what type of box I should use for the sub I am about to buy to make it sound best I will trust your decision, considering you know WAY more about this than I do. If you want I will give you the sub model and whatever else I can and we can go from there. Any help you can give me would be appreciated.


I can probably find the T/S parameters if you have a hard time finding them. Just reply to my initial post in my thread like everyone else did, providing the information I need, and I'll get something designed for you and make it as simple as possible.


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## NRA4ever

Use a sub sonic filter to stop your sub from unloading below the tuning.


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## fishboy38

Sending PM. Thank you in advance for the help!


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## cajunner

necromancer, your box builder has left the building...


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## fishboy38

Was your post in reference to mine? If so I would then assume you meant he is no longer on this forum?


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## cajunner

fishboy38 said:


> Was your post in reference to mine? If so I would then assume you meant he is no longer on this forum?


his last post under this screen name, was over three years ago.

It's safe to assume your PM will float unresponsive, in the river of lost thoughts for a while...


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## fishboy38

Well here is my pm I sent. Anyone else able to help me out?

Hello, 

I like many people am unfortunately not an expert when it comes to car audio, but I know some stuff and am trying to learn as much as I can. I understand you have a great deal of knowledge when it comes to subs and their relationship to their enclosures and surrounding environment with the particular vehicle.

Some info: I have a 2009 Honda Element with nothing stock left. I have a Kenwood Excelon Deck, Kicker components/coax speakers, a JL XD400/4 amp bridged into 2 channels at 200w RMS powering a 6" JL W0v3-4 in the front factory enclosure (reverse phase, tuned at 80 hz LP crossover), and a 12" JL W0v3-4 in its own CP112 Basswedge enclosure in the back (running normal phase tuned to 60 hz LP crossover).

My issue is with the 12". I listen to mostly bass heavy music (rap, dubstep, heavy rock), and when I listen to some songs that play really low ~ 35hz, I get a huge drop in SPL, where if I listen to the same song in other setups, there is a TON of SPL for the same song played from the same source (ipod). Also, some songs sound very boomy, vs true to the frequency they should be. I am assuming its an issue with the relation to my car, as I assume JL is a higher quality than some. The speakers response is rated as low as 22 hz, and their customer service says the box is tuned to 30hz, so 35hz should be good to go right? I really want to fully understand what is going on and fix it, hopefully by modifying the current box with wood or polyfill inside if at all possible to achieve my goal. 

I am looking to get the most out of this sub at the lowest I can, with as flat a response as I can, with as much SPL as I can within the ~25-65hz range.

Any and all advice is greatly appreciated!

Thanks!


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## cajunner

first I'd suspect is the reverse phase on the front sub, then I'd wonder if the 12" is defective, and I'd double check all the wiring connections and amp settings, and make sure the deck has the loudness feature off, and....

well, your set-up should do quite well in a JL-designed pre-fab box, and if 200 watts are getting on, it should hit relatively good, even if it can suck down a few more watts than you're putting in now.

you may not have something wrong, it may be your car has a null way down at 35 hz, but that seems unlikely since most cars do more pressurizing than wave propagation at that low tone.

interesting case, we'd have to see proof if you could get RTA graphs of your car, transfer function, response issue mic'ed and recorded, stuff like that.


right now we can just go on your words, that some songs are losing bass energy without any due cause.


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## fishboy38

All wiring and the like are good to go. The front sub is in reverse on purpose because the subs were competing and choking each other out. 

I do have an RTA graph app on my phone that I paid for and it shows very little drop compared to what my ears hear I'd say, but there is definitely one noted. My car has a lot of open room and obviously it's not contained inside a trunk. 

Any advice?

JL's customer service recommended reducing the box's internal volume by 10%. My head says this will raise the tuning frequency of the box and perpetuate my issue but they say that it's more about tuning the box to the car and my car is acting like a very large box. 
Agree with this?


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