# Can a box be tuned too low?



## Dj4770 (Nov 4, 2012)

I have 1 Sundown SA 15 and I am building a box for it soon. My friend has a program that says that if we tune it to 25hz, it will sound the best. Sundown recommends 35 hz. I listen to mostly rap music althought I do play some decaf songs that get low but thats about 10 percent of what I really listen to in the car. Is 25 hz too low or will it sound good? This is the first box we have ever built so I want to make sure It sounds good at higher frequencies too like atleast up to 60 hz but can hit some of the lower frequencies well.


----------



## minbari (Mar 3, 2011)

if you have the ability to build it and tune it that low, in most cases it will sound better. lower tune will allow you to use a lower SSF and it will unload much later than a higher tune.

higher freq are unlikely to be effected very much by a lower tune.

post the T/S spec if you want a second opinion.


----------



## Mack (Jul 27, 2007)

The only thing I'd worry about is sending too low subsonic frequency that you may potentially damage the sub. Sundown subs are monsters, so it may not be applicable in your case.

Does your amp have a subsonicfilter for this? What you are doing with that filter is creating a bandpass filter so the subs play within a range of frequencies(high and low). 

Any real experts have an opinion on this?


----------



## ATOMICTECH62 (Jan 24, 2009)

If you tune the box lower then what it needs to be then you will loose output and the group delay will be massive.A sealed box would give much better results.
I have played with this on BBP6 a lot.And I have even tried to tune some boxes that i had no T/S parameters for with different length ports.
But if the program says to tune it at 25 hz,and everything is correct then Sundown is wanting you to get more output at the expense of low end extension.
You should be able to compare the 2 boxes with the graphs.
The program might be correct.If it is then its not being tuned too low.
Ive seen people tune boxes lower then recommended by a program thinking they will get really low and it doesnt work right.


----------



## Spyke (Apr 20, 2012)

Tuning lower will protect you sub a little better because it won't unload like was mentioned. And, you can always eq to get the sound you want. Besides, If you take that nice flat freq response curve and compare it to the in car response it won't even be close. Imo, I would tune low and eq.


----------



## asoggysponge (May 14, 2013)

ATOMICTECH62 said:


> If you tune the box lower then what it needs to be then you will loose output and the group delay will be massive.A sealed box would give much better results.
> I have played with this on BBP6 a lot.And I have even tried to tune some boxes that i had no T/S parameters for with different length ports.
> But if the program says to tune it at 25 hz,and everything is correct then Sundown is wanting you to get more output at the expense of low end extension.
> You should be able to compare the 2 boxes with the graphs.
> ...


Is the effect of group delay below 1khz even audible? Every sub I've ever modeled tuned that low has an extremely high group delay. If you want to go by rule of thumb, trying to stay below (group delay x frequency = less than 400) is nearly impossible to achieve with car audio drivers.


----------



## qwertydude (Dec 22, 2008)

It's not just group delay that goes on super low tuning. Most music doesn't have much material below 30 hz anyways. So it's usually better to tune it a little bit higher. You'll get more efficiency in the areas where you actually have music.

Get a function generator app for your smart phone. Play a 25 hz note in your car and tell me if you've ever heard your music go that low. Chances are it never has. People think hip hop and rap go low, they don't, they're just loud, and loud hip hop bass rarely even goes below 35 hz anyways, it's very compressed bandwidth-wise and dynamic range-wise.

You won't notice the loss in subsonic frequencies but I guarantee you'll notice the loss in efficiency when tuning ultra low. And one thing about those tuning programs is that many times they will automatically recommend what plays flattest. They don't take into account cabin gain, and whether you want an efficiency bump in bass frequencies you like to listen to.


----------



## Danometal (Nov 16, 2009)

My sub is tuned to 25 hz (JBL P1224), and it sounds great. Tuning low flattens the response and pushes the group delay way down into inaudible territory. If you have the room for the amount of port for that and the proper net volume, I would go for it. 

Tuning high, like in the mid 30s or higher causes a nasty peak around 45-55ish hz and thus makes it hard to integrate into a SQ oriented setup. 

And, really most subs play a lot higher than expected, especially if their voice coil inductance spec is reasonably low.


----------



## Hanatsu (Nov 9, 2010)

I usually tune around 30Hz. Nothing below that in 99,9% of the music anyway. It's not like sub will unload 0.1Hz below Fb. With a tune of 30Hz you should be fine playing notes slightly lower without unloading. With Fb that low (25-30Hz) a highpass filter "subsonic" is unnecessary imo, otherwise set it roughly 10Hz below tune freq (depending on HP slope). Too low tuning means less power handling above Fb (tune freq).

Group delay cannot be determined by just looking at tune frequency, the slope/rolloff of the transfer function also matters (driver T/S parameters and box size/alignment). Group delay IS audible but fortunally the audibility for phase distortion in the lower frequencies is quite low compared to the midrange. A rule of thumb is to model the enclosure so the GD won't exceed half a cycle of a given frequency - i.e for 50Hz = 1/50sec = 20ms cycle, half of that is 10ms. The GD audibility is frequency dependant! The absolute audibility threshold is debated and some claim that even 1,5x cycle of GD ain't audible in the lower frequencies. 

There is one issue with varying GD however. If it's very high in the transition area between midbass / sub it can be hard to compensate for it. Sealed enclosures often have a fairly flat GD plot.

Sent from my Samsung Galaxy 3 via Tapatalk.


----------



## qwertydude (Dec 22, 2008)

Tuning low flatten the response rate but did you take into account cabin gain?

Cabin gain some some cars can boost 20hz upwards of 12 db making for a really rumbly frequency response. Getting a slight boost in the 40 hz region with a little more cutoff in the subsonics actually flattens in car frequency response and gets you more efficiency. In fact in a SUV or hatchback the reason why sealed subwoofers sound so good is because they have a relatively high f3 and a shallow dropoff rate that dovetails very nicely with cabin gain.

The old Power series JBL used to recommend tuning for ultra flat response, but that was open air response. The the newer ones actually compensated for average in car response and recommend tuning a little higher.

That's why you can't just go by simulation alone when going ported. You kinda have to know how a subwoofer will match with the car's natural response.


----------



## Spyke (Apr 20, 2012)

qwertydude said:


> *Cabin gain some some cars can boost 20hz upwards of 12 db making for a really rumbly frequency response. Getting a slight boost in the 40 hz region with a little more cutoff in the subsonics actually flattens in car frequency response and gets you more efficiency.* In fact in a SUV or hatchback the reason why sealed subwoofers sound so good is because they have a relatively high f3 and a shallow dropoff rate that dovetails very nicely with cabin gain.


I have to agree with this. I noticed this a lot when I went IB. I actually had to boost 45hz quite a bit to compensate for the increased 20-30hz response.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> . Getting a slight boost in the 40 hz region with a little more cutoff in the subsonics actually flattens in car frequency response


Nope. The closer you get to a gently sloping low frequency output (which requires a low tuning) rather than a peaked then sharp cutoff (which you will get with a higher tuning), the closer you'll get to a flatter response in-car. This is very easy to model with a program that takes the car's actual transfer funtion into consideration.


----------



## Danometal (Nov 16, 2009)

I meant to add to my recommendation that my trunk car doesn't have a ton of cabin gain, especially with all my windows down and sunroof open, and my hearing naturally rolls off down low, so all that was factored into my decision to tune to 25 hz.

Not sure what vehicle the OP has.


----------



## Brian Steele (Jun 1, 2007)

Spyke said:


> I have to agree with this. I noticed this a lot when I went IB. I actually had to boost 45hz quite a bit to compensate for the increased 20-30hz response.


IB <> vented, so you really can't compare the two alignments.

If you want to get close to the in-car flat response of a sealed box with a vented alignment, this requires detuning the vented box to a lower frequency and adjusting the box size somewhat.


----------



## qwertydude (Dec 22, 2008)

Brian Steele said:


> Nope. The closer you get to a gently sloping low frequency output (which requires a low tuning) rather than a peaked then sharp cutoff (which you will get with a higher tuning), the closer you'll get to a flatter response in-car. This is very easy to model with a program that takes the car's actual transfer funtion into consideration.


You don't get a flatter in car response by simply tuning low. Cutoff steepness is determined by box size, large boxes have steeper cutoffs, small boxes have shallower cutoffs. By tuning below the cars cabin gain range you still end up with a response bump.

If your cars cabin gain is 6 db/octave starting around 60 hz, the only way to get a flat response then is not by tuning to 25hz. Your sub will play open flat to that if it's a quality unit, but you won't have a response match.

In fact besides a sealed box, the only way to get a 6 db shallow slope is a very small box and about 40hz or higher tuning frequency. About the opposite most people assume which is a large box and ultra low tuning.

Don't take my word for it either. Simply model it. Take the same subwoofer and keep the same tuning frequency and change the box volume and look at the steepness of the rolloff, smaller boxes will rolloff slower. Larger boxes will play flat lower but again like I said will drop off quicker and playing flat low in a car with significant cabin gain won't give you flat in car response.

And just simply playing with it, if you want a shallow cutoff you can achieve it by ultra low tuning and very small enclosures. With my RE SXX12 I've determined similar response should be .25 cubic foot tuned to 10hz, but it has no real advantage over a simple 1 cubic foot sealed box. It's also called a transmission line box. I've yet to see any sane person put a true transmission line in their car.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> Don't take my word for it either. Simply model it.


Well, here ya go - my Alpine 12D2 in a 26 Hz vented alignment (red) and in the same box size with a 35 Hz vented alignment (blue), using my car's *actual* measured transfer function added to determine what the actual response would likely be in-car. You tell me which one you think is flattest.


----------



## Brian Steele (Jun 1, 2007)

Brian Steele said:


> Well, here ya go - my Alpine 12D2 in a 26 Hz vented alignment (red) and in the same box size with a 35 Hz vented alignment (blue), using my car's *actual* measured transfer function added to determine what the actual response would likely be in-car. You tell me which one you think is flattest.


Aargh, I hate when that happens. The model was done with the SWS-12D2, not the Type R 12D2. However, the message remains the same.


----------



## Spyke (Apr 20, 2012)

Brian Steele said:


> IB <> vented, so you really can't compare the two alignments.
> 
> If you want to get close to the in-car flat response of a sealed box with a vented alignment, this requires detuning the vented box to a lower frequency and adjusting the box size somewhat.


If you didn't get my point, don't worry about it.


----------



## qwertydude (Dec 22, 2008)

The Type SWS and Type R have entirely different response curves.

In fact the reason why ultra low tuning on a Type S works in car is because it really needs a sealed box with such a high Qts and Vas. In fact in order to get any decent response out of that subwoofer ported it requires lower tuning because of the very large box requirements.

That's such a horrible state of tune and an unnecessarily uncontrollable subwoofer in a ported configuration the low tuning is needed simply to keep it from becoming a boomy sloppy nightmare.

The same goes for the Type R but a smaller box at and even lower at 3.57 cubic feet and 22.36 hz. Simple fact is the Alpines are simply not going to do well ported, the box requirements are ridiculously large and need to be tuned so low in order to not sound boomy and have any low end at all.

But I'm comparing it to my RE SXX12 which in order to match well with my car simply needs only 2 cubic feet and a higher 34 hz. It'll play flatter naturally with a shallower rolloff because of the smaller box requirements. So simply stating tuning ultra low without stating what kind of in car response or subwoofer requirements can be a recipe for a really inefficient and sloppy sounding system.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> The same goes for the Type R but a smaller box at and even lower at 3.57 cubic feet and 22.36 hz.


Below is the Type R 12D2 modelled in 1.45 cu.ft., 25 Hz vented (red) and 35 Hz vented (blue). This driver is capable of a Qb=0.7 alignment in a box smaller than 1 cu.ft. and is known for great output in a vented alignment.

Tell me the specs of your RE sub and I'll see what works out to be flatter as well, using my car's measured t/f.

IMO the key here is the MEASURED transfer-function of the car and finding the best match for it. You can't just assume 12dB gain under x Hz. It's a bit more complex than that. Any my modelling shows that the lower tuned box seems to be always better at getting that flatter response.

BTW, the box sizes I used for the SWS-12D2 alignment earlier? 1.6 c.uft.


----------



## Dj4770 (Nov 4, 2012)

Danometal said:


> I meant to add to my recommendation that my trunk car doesn't have a ton of cabin gain, especially with all my windows down and sunroof open, and my hearing naturally rolls off down low, so all that was factored into my decision to tune to 25 hz.
> 
> Not sure what vehicle the OP has.


I have an 03 Altima and I will ask him what program he is using. At first he was saying that a tuning of 30 hz gives a very flat response which is fine but he lowered it to 25 which worried me although I will add that it is a free program he is using. He was also trying to find a program that added cabin space into the equation but he doesn't want to pay for the program so I cannot really trust whether the tuning will be accurate so I personally think that 30hz tuning will be fine as long as we do it right. Most of my music hits around 35 hz and up anyways for 30 is perfect for me as I have only a few songs that get that low.


----------



## Brian Steele (Jun 1, 2007)

Dj4770 said:


> I have an 03 Altima and I will ask him what program he is using. At first he was saying that a tuning of 30 hz gives a very flat response which is fine but he lowered it to 25 which worried me although I will add that it is a free program he is using. He was also trying to find a program that added cabin space into the equation but he doesn't want to pay for the program so I cannot really trust whether the tuning will be accurate so I personally think that 30hz tuning will be fine as long as we do it right. Most of my music hits around 35 hz and up anyways for 30 is perfect for me as I have only a few songs that get that low.


Note that a lot of people don't MEASURE the Fb they targetted, and many box design programs can give vent dimensions that result in an FB quite a bit lower than targetted, particularly when the inside opening to the vent is near to a cabinet wall or corner. Someone telling you that the box is vented to 30 Hz may not therefore necesarily mean that it is actually tuned to that frequency.


----------



## qwertydude (Dec 22, 2008)

If you can't find the specs for an SXX 12d4 on your own and need me to provide them you really shouldn't even be giving any advice. The data is out there.

In my car which is a hatchback, to my ear compared to my in ear monitors with a 2 cubic foot box tuned to 34hz, and that's box measured box tuning not theoretical tuning, my sub plays flat. If I tuned it lower I'd lose efficiency and only gain subsonics.. To me that's a lose, lose.

The Alpines on the other hand apparently need lower tuning. And just comparing the three subs in ported enclosures, specifically with a 1.45 cubic foot 25 hz enclosure I can easily see the SXX, in my 2 cubic foot 34 hz, not only playing the lowest frequencies but also playing into the higher midbass frequencies and that's still using a smaller higher tuned enclosure. That's sorta the magic with low Qts subwoofers that are specifically made to be put in smaller ported enclosures which can play a wider frequency range with a flatter response without efficiency compromising ultra low tuning. In fact if I tune that low I actually lose bass response almost all across the board except for the midbass and a small slope near box tuning. Oh and if you can't see the Yellow is the Type S surprising how efficient it is though it's peak is at 70 hz, Type R is unsurprisingly less efficient but can play flatter. The SXX demolishes both playing with more authority down to 26 hz and bear in mind this is with 34 hz box tuning, it also has less prominent peaks with only a 3.5 db variance from 32 to 125 hz, overall more sound output and only losing to the Type S in the 70hz peak. This doesn't even take into account cabin gain which will more than make up for my lack of subsonic bass.

This is the point I'm trying to make is that ultra low tuning isn't a universal necessity. If you need ultra low tuning to play flat it's more than likely you have a sub not really made to play flat in a ported box. And those Alpines just do not do well in such small boxes they really need very large boxes ported since their Qts is quite high, they are more suited to sealed. And small box ultra low tuning actually gets a response quite similar to sealed, I just ran a simulation and yup small box ultra ultra low tuning like 10 hz, essentially transmission line, just about matches a sealed box.


----------



## Hanatsu (Nov 9, 2010)

Brian Steele said:


> Note that a lot of people don't MEASURE the Fb they targetted, and many box design programs can give vent dimensions that result in an FB quite a bit lower than targetted, particularly when the inside opening to the vent is near to a cabinet wall or corner. Someone telling you that the box is vented to 30 Hz may not therefore necesarily mean that it is actually tuned to that frequency.


This ^^

Sent from my Samsung Galaxy 3 via Tapatalk.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> If you can't find the specs for an SXX 12d4 on your own and need me to provide them you really shouldn't even be giving any advice. The data is out there.


Actually, if you reread what I asked, you'd see I was asking for the parameters of YOUR SXX drivers, not the published ones. If you didn't measure them before actually building a box around them, particularly when it seems that you apparently went to the trouble of actually measuring the Fb, then perhaps you really should not be giving any advice either . 

FWIW, you didn't even mention which version you have because I've found two sets of specs for the SXX - one that has a higher Fs and lower Qts than the other. It's not a driver that I'd buy anyway, as they don't publish Le, which can tell you very quickly if it's designed for SQ or just a high-BL "boomer" sub for which you can't trust any of the predicted performance above 60 Hz because the high Le significantly affects it.

Anyway, here's three graphs for you, showing the predicted response with measured car t/f:

(1) the Re (low Qts) (red) vs the Alpine Type R (blue), in a 1.45 cu.ft. box tuned to have as flat a passband as possible in-car

(2) Same thing, this time using your stated 2.5 cu.ft. box, 34 Hz Fb, and tuned for flat in-car response with the Alpine (Fb=25 Hz), and

(2) Both drivers in a 2.5 cu.ft. box, tuned to 34 Hz 


I'll let the graphs speak for themselves. 

Finally, just a suggestion - next time you want to talk about the low tuning and effects of cabin gain, use a box-modeling tool that actually shows the effects of ACTUAL cabin on the response curve.


----------



## Brian Steele (Jun 1, 2007)

Hanatsu said:


> This ^^.


Yup. In my experience, many simply have no idea what their vented sub is actually tuned to or how it performs because they spend xx hours building it, yy hours pontificating over it and 0 hours actually measuring it, LOL.


----------



## qwertydude (Dec 22, 2008)

The specs in the T/S box on the RE Audio site are designated wrong at .44 Qts. The manual itself states a .3 Qts which by my own experience it's definitely a .30 Qts because I stuck my SXX in a small sealed box and it positively didn't work at all. A .44 Qts subwoofer should definitely have worked sealed.

And yes they don't publish the Le spec but I've measured the voltage on mine at different frequencies with an inline resistor equal to the dc resistance to get an idea of the Le. I came up with 4 mh with the voice coils wired in parallel. So it's not exactly a JBL WGTI but neither is the Alpine Type R. I don't have a klippel machine so I kinda have to trust the manual that the other parameters are at least true to spec.

But something is telling me there's something up with the modeling software used when a .30 Qts subwoofer and a .48 Qts subwoofer model essentially the same when put in the same box. It may have transfer function capability but even I would take that to be suspect when my own experience dropping different subs in my 2 cubic foot 34 hz box tells me quite easily that different Qts subs behave very differently in the same box.










This is what WinISD tells me happens when the Type R and SXX are put in my 2 cubic foot 34 hz box.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> The specs in the T/S box on the RE Audio site are designated wrong at .44 Qts. The manual itself states a .3 Qts which by my own experience it's definitely a .30 Qts because I stuck my SXX in a small sealed box and it positively didn't work at all. A .44 Qts subwoofer should definitely have worked sealed.


Low Q spec here - RE Audio SXX12D4 (SXX-12D4) 12" Dual 4 ohm Car Subwoofer

Higher Q specs here - woofers

Qts is not the only determinant of ideal box alignment. Vas and Fs also have quite a lot to say about that. In any case, a simple tester like a WT3 can find the correct parameters in seconds. Failing that, there's a method on my site that can be used to test t/s params, but it can take a while, depending on what accuracy you're looking for. In any case, I usually check the parameters first before building a box for the driver - saves possible grief later on.




qwertydude said:


> And yes they don't publish the Le spec but I've measured the voltage on mine at different frequencies with an inline resistor equal to the dc resistance to get an idea of the Le. I came up with 4 mh with the voice coils wired in parallel.


That is VERY high for what is basically a 2 Ohm load. Unless the motor is very good, noticeable audible effects due to shifts in Le could occur as low as 80 Hz. For comparison purposes, the old Shiva checked in at 1.94mH, and that was wired in parallel for a 4 Ohm load (Fo~300 Hz). My previous pair of cheap Infinity Kappa pros checked in at around 1.97 mH wired for a 2-ohm load (Fo~160 Hz). My current Alpines check in at 1.52 mH for a 2 ohm load (Fo~210 Hz). The Type Rs however have a pretty flat BL curve, so I expect, and have measured (see my review on the driver) very low distortion anyway.




qwertydude said:


> But something is telling me there's something up with the modeling software used when a .30 Qts subwoofer and a .48 Qts subwoofer model essentially the same when put in the same box. It may have transfer function capability but even I would take that to be suspect when my own experience dropping different subs in my 2 cubic foot 34 hz box tells me quite easily that different Qts subs behave very differently in the same box.


Make sure you've entered the correct Vas and Fs for both drivers.


----------



## qwertydude (Dec 22, 2008)

The motor is most definitely very good and strong. The suspension is so stiff you really have a hard time pushing it in just with your hands. Just physically trying to hold the woofer while playing a 10 hz test tone I literally can't stop the motor from moving, it will push back with a lot of force. My JBL P1224 I can definitely stop cone movement by pushing against the cone, and it has similar motor strength to the Type R, 12 t-m of Bl. So that extra Bl definitely aids in keeping the upper bass frequencies from disappearing.










The simulation I put up includes a 4 mh Le at 2 ohms and you can see it still models with more upper frequency response than the Type R at 1.52 mh at 2 ohms. And listening to my friend's Type R ported before at 2.5 cubic foot 30 hz I know the Type R doesn't have as much upper bass authority as the SXX.

Even putting 1.52 mh on the Type R the SXX still has more output on my 2 cubic foot 34 hz box up to 150 hz or so. I can attest the SXX definitely has more upper bass and even a little midbass punch. Certainly not as much as my JBL P1224 sealed but the SXX12d4 definitely doesn't fall off a cliff above 60 hz.

That's why I still have a hard time believing these two woofers would model so similarly in a program when WinISD and my own experience tells me they're vastly different woofers that behave very differently when put in the same box.

The whole point I'm trying to make here isn't bashing on Alpine. The Type R is a decent subwoofer. The SXX is definitely a great subwoofer and definitely one to get if you're apt to abuse your subs with extremely high power. But the point is the simulations for me definitely show they're two very different subwoofers and that goes along with my personal experience but your simulations show they seem to be near identical especially when put in the same box, my 2 cubic foot 34 hz box for example.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> The motor is most definitely very good and strong. The suspension is so stiff you really have a hard time pushing it in just with your hands. Just physically trying to hold the woofer while playing a 10 hz test tone I literally can't stop the motor from moving, it will push back with a lot of force.


I said good motor, not strong motor. What does the BL curve look like? How does Le vary with displacement? Those are the type of characteristics I look for when I want to judge whether a motor is good or not. If they're not published, in any case I do my own distortion tests and find out anyway. Anyone can slap a few magnets on a chunk of iron with a coil on it to get high BL. It's how linear that motor behaves in operation that really counts IMO.


----------



## sh.moto.2 (Jul 2, 2010)

ok, you guts are getting a little technical..... the best thing to do is to build a couple different enclosures... depending on your thirst for sound see which one fits the bill, this will also give you more experience in making enclosures( u said u had none), scrap the box building programs because the outcome will be completely different in every vehicle. experimentation=experience


----------



## qwertydude (Dec 22, 2008)

When did this all of a sudden get to motor linearity, Bl distortion, and displacement graphs? I never mentioned those.

The point I'm trying to make is simple frequency response and box tuning. It seems to be a distraction for you that you simply can't accept that not every subwoofer on the planet benefits from ultra low tuning. The Alpines happen to be one that does.

The point the OP was asking was do you always have to tune so low. What everyone on this thread including me is trying to say is no. And not every subwoofer benefits from it. Most people don't really care that their subwoofer isn't playing sub-sonics.

I put on the plots for my SXX and box for it and explanation of why I chose it and then you come back with some plots saying it doesn't matter and you just need to tune it lower. Well if what you're saying is true and the plots you posted are accurate and both subwoofers sound essentially the same, why come back now claiming they're so different, the motor must be inferior, there must be motor distortion, the SXX is just a slapped together driver.

I mean even your first posts came in claiming the ultra low tuning message stays the same with the Type R and Type S which have very different characteristics. Then you back track on that one. Because earlier you say the lower the tuning the better you get to being flat, except of course when you go with IB which definitely can get too boosted in the sub-bass, IB happens to have almost exactly the same FR as transmission line alignments, which is also the same as small box ultra ultra low tuning. And the people who've tried that know you end up having to boost upper bass to compensate for the really strong sub-bass. Which in real life in a car means not flat frequency response.

To me it seems like a poor defense trying to defend the Type R and denigrate RE Audio for being some sort or rank amateurs. I've seen plenty of SQ competition cars and they often ran ported boxes. And they definitely were going for SQ and when I asked about their enclosures a majority of them weren't tuning in the low 20's.


----------



## sqshoestring (Jun 19, 2007)

OP- IMO you take the factors at hand and make a good guess. You have the music you listen to most and the response you like, you have the cabin gain of the car, you have the output you are looking for, etc. If you want more output you tune higher, more SQ you tune lower, car has gain you can tune according to that, you like 30hz hits (or XXhz) you tune to have it work there. 

I think one of the best things is to try a temp sub you can model, then say I want more/less of whatever. It gives you something to compare against in that car, gives you a benchmark far as tone/response you want to have. You can then model prospects against that temp sub. Play some tones to get familiar with what Hz range you are looking to change output of.

I tried many boxes/subs and still lacked bottom, now I have pair of 15s IB and still boost 20-30hz even with a qts .7 and fs20hz which is great for response down there. Part of it is this car seems to kill bass under 40hz not sure, but now it has a healthy bottom some would say is too much. I like a hit at 25-35hz and it gets it done. If I did ported I would tune at 30hz max, go lower and I lose output above tuning (30-35hz), go higher I lose 30 and below. Though output can be changed with the amp and sub you use. If you want strong 35hz for example and tune a lot below that you will see the gain drop at 35. If your sub is not that strong it will sound weak. Most manufacturers seem to recommend tuning higher I think for more output is my guess, I tend to not like it. I hear all kinds of sound in the 20-30hz range now....how can you know if you never have subs that will do it like most that will not? Just the same it takes more to get down there and you will give up output doing it unless you overkill like I did. I don't have need for pair of 15s for my use normally, only to get that low not to go super loud. I have 125/ch on highs (4 doors) and it matches up nice with 500rms on the subs with authority down to 25hz. I do have a midbass weakness in the 60-80hz range but that from my small mids no time to do a better install yet, and don't like my subs localizing that high.

Like Qwerty says, it can also depend on what you are putting in....you will never get much 30hz out of 8s for example with any normal setup that is why I have 15s. It is senseless to tune to something your equipment can't handle. Many people here tune low for SQ you get a flatter response and you get the whole musical range if you can get to 20hz or close. Many people here also run better subs and amps capable of more....most don't run $50 15s like me lol but they work for my particular application.


----------



## BuickGN (May 29, 2009)

sqshoestring said:


> OP- IMO you take the factors at hand and make a good guess. You have the music you listen to most and the response you like, you have the cabin gain of the car, you have the output you are looking for, etc. If you want more output you tune higher, more SQ you tune lower, car has gain you can tune according to that, you like 30hz hits (or XXhz) you tune to have it work there.
> 
> I think one of the best things is to try a temp sub you can model, then say I want more/less of whatever. It gives you something to compare against in that car, gives you a benchmark far as tone/response you want to have. You can then model prospects against that temp sub. Play some tones to get familiar with what Hz range you are looking to change output of.
> 
> ...


For your application those subs are great, regardless of price. That's one setup I've been wanting to hear. 

I agree with everything you said. I'm like you, I don't need a pair of 15s for a lot of my listening and I don't like to go around with it at obnoxious SPL but that cone area is awful nice when you want to go really low with some authority. I had no idea how effortless the really low stuff could be until I had a pair of 15s IB. 

About ported, I've never done any measurements and I've only run 2 ported setups in my life, one of them was with my 12W6s which I also ran sealed, bandpass, and IB over the course of about 7 years so it was a great comparison of the different alignments. There was absolutely no doubt that a 28hz tune sounded better than the 40hz tune. That's holds true in every single car I've ever heard with a ported setup. 100% of them have sounded better with a low tune. They just play flatter and sound "quicker", "punchy", and all of the other common adjectives to describe a good sounding sub setup while also going low. If you have to cut a little at 20-30hz, that's not a bad thing by any means. I'm also the guy that thinks every sub I've ever tried in both sealed and IB or sealed and larger sealed sounds better the larger the enclosure gets so maybe I'm just crazy.


----------



## ChrisB (Jul 3, 2008)

I tuned my Digital Designs 1508 to 32 Hz in one cubic foot net and regretted doing so. So yes, it is possible to tune too low!

Now for the why. I measured my 1508 with a Woofer Tester 3, modeled it up in BBP6, and noticed there was a huge hump near 45 Hz using their recommended tuning frequency of 40 Hz. Sooooo, I play with the program, tune lower and smooth out the response. Great, right?

WRONG! I forgot to measure the exhaust drone of my car at and that bump I tuned out should have been sufficient to overcome the exhaust noise. DOH! The end result was deep bass out the wazoo, but it peters out near the exhaust frequency.

I'm going to build one more box when it gets cooler outside before I give up on Digital Designs all together, but I have some other subs that I want to play with in the meantime!


----------



## Brian Steele (Jun 1, 2007)

BuickGN said:


> There was absolutely no doubt that a 28hz tune sounded better than the 40hz tune. That's holds true in every single car I've ever heard with a ported setup. 100% of them have sounded better with a low tune. They just play flatter and sound "quicker", "punchy", and all of the other common adjectives to describe a good sounding sub setup while also going low.


Exactly. And this can easily be shown by any box modelling program THAT CAN INCLUDE THE EFFECT OF THE CAR'S TRANSFER FUNCTION.


----------



## Brian Steele (Jun 1, 2007)

qwertydude said:


> When did this all of a sudden get to motor linearity, Bl distortion, and displacement graphs? I never mentioned those.


Hey, you opened the door - I only walked through it ;-).




qwertydude said:


> The point I'm trying to make is simple frequency response and box tuning. It seems to be a distraction for you that you simply can't accept that not every subwoofer on the planet benefits from ultra low tuning. The Alpines happen to be one that does.


Many more do. In fact, I can't remember coming across one that doesn't, and that includes your RE sub. Which, BTW, in that 2.5 cu.ft. box vented to 34 Hz likely produces a big peak in-car around that frequency, rather than a smooth in-car response, and that's using an actual measured car T/F, not using WinISD which is apparently incapable of incorporating it and taking a guess. I showed you just that in one of the graphs I put up.




qwertydude said:


> Well if what you're saying is true and the plots you posted are accurate and both subwoofers sound essentially the same, why come back now claiming they're so different, the motor must be inferior, there must be motor distortion, the SXX is just a slapped together driver.


I fail to see what correlation you're trying to draw here. Unless you're really suggesting that you really don't know the difference betwen a predicted FR curve based on small-signal parameters and distortion at higher power caused by poor motor design.




qwertydude said:


> I mean even your first posts came in claiming the ultra low tuning message stays the same with the Type R and Type S which have very different characteristics.


Did you notice that I changed the box size between the models? A vented alignment consists of the resonance frequency AND the box size, and the impact that has on the overall performance with a chosen driver. You can't just look at Fb alone and draw conclusions.




qwertydude said:


> Then you back track on that one. Because earlier you say the lower the tuning the better you get to being flat, except of course when you go with IB which definitely can get too boosted in the sub-bass, IB happens to have almost exactly the same FR as transmission line alignments


Totally disagree. Depending on the driver used, an IB system can in fact have a response quite similar to a very low Q SEALED box, which can result in a rising low frequency response when cabin gain is taken into consideration.


----------

