# Subwoofer Fs and Box Tuning



## rxh0272 (Jul 26, 2020)

Hi Guys:

can someone please help me? What do we do, apply, when we never a sub woofers resonate frequency?

when designing the subwoofer enclosure, do I need to tune it to make sure I am above the resonant frequency, below the resonant frequency, or what?

And what does the cars resonant frequency have to do with the subwoofer resonant frequency and enclosure design? Sealed/ported?

is it worth me buying the least expensive equipment to determine the resonant frequency of the car in order to properly design the subwoofer enclosure and choose the proper subwoofer?

Thank You,
Rob


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## daloudin (Nov 2, 2020)

The resonant frequency of the woofer is the point at which the driver naturally rolls off below that point. It used to be that you had to have a sub with an Fs (resonant frequency) that was really low in order to play true sub bass but with the abundance of wattage and dsp/eq available now you can add enough boost below Fs to compensate. Once you add in cabin gain it's usually not necessary anyway. 

The car will have multiple resonant frequencies as every pair of parallel surfaces will have one frequency and then there's the helmholtz resonance (the low frequency thrumming you get when you only open one window - it's the sound that a bottle makes when you blow across the opening) and panel resonance and the list goes on...

The most important resonant frequency is the box you put the Subwoofer in... the wrong box can ruin the best Sub and even an expensive box that's not the right size or design is equally as bad. Any good sub will list Thiele Small parameters which can be entered in to a free box design program (WinISD, BassBox, etc) to give you good idea of what box the driver needs. 

Then you also have to use the right kind of sub in the right kind of design: sealed, ported, passive radiator, bandpass, infinite baffle, etc. Each sub has a preferred design but some work equally well in multiple designs. Ported is louder but if it's not tuned correctly then it's boomy and peaks without much bass extension since it rolls off faster below tuning. Sealed rolls off the slowest (well actually infinite baffle is slowest but that's not really an enclosure unless you count the trunk as the enclosure) for the best low bass extension. But you can design a ported enclosure that's capable of going just as low with the right sub...

Clear as mud?

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## rxh0272 (Jul 26, 2020)

daloudin said:


> The resonant frequency of the woofer is the point at which the driver naturally rolls off below that point. It used to be that you had to have a sub with an Fs (resonant frequency) that was really low in order to play true sub bass but with the abundance of wattage and dsp/eq available now you can add enough boost below Fs to compensate. Once you add in cabin gain it's usually not necessary anyway.
> 
> The car will have multiple resonant frequencies as every pair of parallel surfaces will have one frequency and then there's the helmholtz resonance (the low frequency thrumming you get when you only open one window - it's the sound that a bottle makes when you blow across the opening) and panel resonance and the list goes on...
> 
> ...


Thanks for the reply. 
So, when using winISD Pro to simulate subs (JL 10W3v3, RF P3-10) I can tune the box to whatever Hz I want? 
I was looking at the peaks and adjusting size, port length,etc. trying to get it not peaky.


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## daloudin (Nov 2, 2020)

WinISD will give you optimum tuning right out of the gate. Then if you want to fiddle with things like port tuning or box size you can but avoid doing the click and drag thing as it moves way too much at a time and it's really hard to control. But yes, you can change the tuning frequency of the box or port for vented and changing the size in sealed will change the Q. The lower the Q (optimum is 0.707) to go towards infinite baffle and a slower low frequency roll off, raise the Q to increase rolloff, power handling and create an increase in response above the tuning point. 

You "can" model in-cabin gain but it's all just an estimate based on math. 

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## LBaudio (Jan 9, 2009)

Usually we tune boxes at or a bit above FS of the driver in case of ported enclosures. The driver will ofcourse play under own Fs, but with added distortion. 
In case of sealed it will play to Fo since we usually dont use subsonic filter with sealed enclosures.


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## rxh0272 (Jul 26, 2020)

daloudin said:


> WinISD will give you optimum tuning right out of the gate. Then if you want to fiddle with things like port tuning or box size you can but avoid doing the click and drag thing as it moves way too much at a time and it's really hard to control. But yes, you can change the tuning frequency of the box or port for vented and changing the size in sealed will change the Q. The lower the Q (optimum is 0.707) to go towards infinite baffle and a slower low frequency roll off, raise the Q to increase rolloff, power handling and create an increase in response above the tuning point.
> 
> You "can" model in-cabin gain but it's all just an estimate based on math.
> 
> Sent from my SM-G965U using Tapatalk


Thanks a lot for the input. 
My TS parameter notes r home.
If I recall, .707 is typically used. .6 is kind of middle of the road. .5 is lot and can be too low. 

So, when I forst enter the parameters and load it as a project, whatever is in there is the optimum performance that winISD Pro calculated, right?

But, for the P3-10 it made something like a 23 cubic foot box. And for the JL is was something lime 9 cubes. 

So, basically it’s best to only manually modify the box volume and let winISD calculate the rest, but make sure Q remains at/around .707, correct? 

Is winISD Pro simulation accurate in the real world?


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## Destarah (Feb 24, 2019)

I find it helpful to compare the recommendation from WinISD to the recommended box size from the manufacturer. You can make a copy of the project and then modify the size and tuning frequency to see how things change. Here is an example of the P3-10 in WinISD recommended ported compared to RF recommended:









As you can see, RF (red) is louder above 35Hz (1.4cuft box, 40Hz tuning frequency) but below 35Hz the WinISD option crushes (due to the 20Hz tuning frequency and 3.3cuft box) 20dB louder at 20Hz. If you are looking for significantly higher output at 45Hz then the RF option is great lol.
Full list of differences:









Hope this helps


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Thanks a lot for the input.
> My TS parameter notes r home.
> If I recall, .707 is typically used. .6 is kind of middle of the road. .5 is lot and can be too low.
> 
> ...


In theory, yes. WinISD will give you optimum but if it said 23ft³ then start by looking at the parameters input for that driver. Specifically look at the units for each one and make sure they are correct. Things like VAS in liters vs ft³ can throw WinISD off course in a big way. Big M vs little m for things like motor force etc. Check every one of the inputs, leave no stone unturned. Click on the units label and it will increment through the available options. 

PA woofers with accordian cloth surrounds and extremely high efficiency usually model in the 20+ ft³ but not a sub designed for use in a car. (I'm not near my laptop to run some quick models rn.)

Then there are size limitations due to the car. You get a sub that models to 0.7 in a 1ft³ box but the space for the factory sub only allows for a maximum of 0.7ft³ so the box Q goes up and you compensate with eq in the dsp. But ideally, you make the box as flat as possible (for SQ) and then use dsp to take care of peaks and valleys caused by the cabin.

Going below 0.5 means you're getting in to infinite baffle territory and wasting space with very little return. 

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## rxh0272 (Jul 26, 2020)

Destarah said:


> I find it helpful to compare the recommendation from WinISD to the recommended box size from the manufacturer. You can make a copy of the project and then modify the size and tuning frequency to see how things change. Here is an example of the P3-10 in WinISD recommended ported compared to RF recommended:
> View attachment 290128
> 
> 
> ...


Thanks *Destarah:*

What version of winISD are you using? I'm using the latest version of winISD Pro alpha. But, I'm not sure I really know how to use it, so I. am reading the Help contents top-to-bottom

--I'm trying to go as low as the sub can with good output. The P3 was just a starting point. In another forum, we narrowed it down to a 10" because of size constraints. However, I could always double the size by using the size of the entire floor. Right now, I took the floor area and divided it by 2, and plan to put the box on the left side of the trunk. This will save more trunk room. down firing anyway. 

--Is there any other recommendations you have for a better sub that can go low?
--Been modeling some JL sub, but expensive; yet, easier to tune.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Thanks *Destarah:*
> 
> What version of winISD are you using? I'm using the latest version of winISD Pro alpha. But, I'm not sure I really know how to use it, so I. am reading the Help contents top-to-bottom
> 
> ...


Check out the Dayton HO-44 - Really small box requirements and you can put 2 of them in 3 ft³ ported around 22-24hz for the same price as one more expensive sub.

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## rxh0272 (Jul 26, 2020)

daloudin said:


> In theory, yes. WinISD will give you optimum but if it said 23ft³ then start by looking at the parameters input for that driver. Specifically look at the units for each one and make sure they are correct. Things like VAS in liters vs ft³ can throw WinISD off course in a big way. Big M vs little m for things like motor force etc. Check every one of the inputs, leave no stone unturned. Click on the units label and it will increment through the available options.
> 
> PA woofers with accordian cloth surrounds and extremely high efficiency usually model in the 20+ ft³ but not a sub designed for use in a car. (I'm not near my laptop to run some quick models rn.)
> 
> ...


Happy Sunday. Thanks for the input.
I still do not fully understand Q. I'm readying up on it.
--The recommended box size, vented for a P3D4-10 is 3.019ft³; I have 1.638ft³ before sub+port displacement subtracted.
I checked all the values, and they are correct, except Vd is 0.02 ft³, but the sub, in this case a P3D4-10, is 0.074, and when I try and change it, WinISD says to check values/doesn't let me save.

--I have 1.638 ft³ before sub and port displacement. When I use winISD Pro, does the program automatically subtract the port displacement from the internal volume?


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## rxh0272 (Jul 26, 2020)

daloudin said:


> In theory, yes. WinISD will give you optimum but if it said 23ft³ then start by looking at the parameters input for that driver. Specifically look at the units for each one and make sure they are correct. Things like VAS in liters vs ft³ can throw WinISD off course in a big way. Big M vs little m for things like motor force etc. Check every one of the inputs, leave no stone unturned. Click on the units label and it will increment through the available options.
> 
> PA woofers with accordian cloth surrounds and extremely high efficiency usually model in the 20+ ft³ but not a sub designed for use in a car. (I'm not near my laptop to run some quick models rn.)
> 
> ...


Hello:

So, I checked all the values, and they are all correct values and measurements, except Vd. 
--I believe Vd is the driver displacement? sorry, haven't done a build since about 1998. 
If Vd is the driver, then it's supposed to be 0.074'³. But, when i change it and try and save, winISD gives an error message.


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## Destarah (Feb 24, 2019)

rxh0272 said:


> I checked all the values, and they are correct, except Vd is 0.02 ft³, but the sub, in this case a P3D4-10, is 0.074, and when I try and change it, WinISD says to check values/doesn't let me save.


Follow the instructions found here when entering driver parameters ... it's best to let WinISD calculate as many values as possible based on minimum input.



rxh0272 said:


> I have 1.638 ft³ before sub and port displacement. When I use winISD Pro, does the program automatically subtract the port displacement from the internal volume?


WinISD is not calculating the net volume, it is telling you what the net volume needs to be. Figure on 0.3cuft for a 10" sub and port combined. So your volume in WinISD should be 1.3cuft


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## rxh0272 (Jul 26, 2020)

daloudin said:


> Check out the Dayton HO-44 - Really small box requirements and you can put 2 of them in 3 ft³ ported around 22-24hz for the same price as one more expensive sub.
> 
> Sent from my SM-G965U using Tapatalk


I have used Dayton


Destarah said:


> Follow the instructions found here when entering driver parameters ... it's best to let WinISD calculate as many values as possible based on minimum input.
> 
> 
> 
> WinISD is not calculating the net volume, it is telling you what the net volume needs to be. Figure on 0.3cuft for a 10" sub and port combined. So your volume in WinISD should be 1.3cuft


OK. So basically just use my calculated net after subtracting out port + sub displacement.
The link does go to anything.


Destarah said:


> Follow the instructions found here when entering driver parameters ... it's best to let WinISD calculate as many values as possible based on minimum input.
> 
> 
> 
> WinISD is not calculating the net volume, it is telling you what the net volume needs to be. Figure on 0.3cuft for a 10" sub and port combined. So your volume in WinISD should be 1.3cuft


OK. So basically just use my calculated net after subtracting out port + sub displacement. 
The link does not go to anything. Says that the forum is empty


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## daloudin (Nov 2, 2020)

The order of entering in driver data is also in the Help document in WinISD:
Cut and pasted from WinISD Help document.
The suggested procedure for entering driver parameters is following (check first that "Auto calculate unknowns" option is checked):

1. Enter *Mms* and *Cms*

This gives *fs*. If either is not available, then enter *fs* and other parameter.

2. Enter *Sd*, *Bl* and *Re*

Now, you should get all but *Qms* (and *Qts*), *Vas*. Please note that Vas may not match exactly what is specified by manufacturer, because exact value of Vas depends on environmental parameters. See FAQ.

3. Enter *Rms* or *Qms*.

Either one will do, although I tend to prefer *Qms* over *Rms*, because it can usually be measured in driver measurement procedures.

4. Enter *Hc*, *Hg* and *Pe*.

If *Hc* or *Hg* or either is available, then enter *Xmax* and optionally either *Hc* or *Hg* if available.

5. Enter number of voicecoils.

This procedure is most accurate. Also note that it also calculates true SPL (1W/1m) value. So it might not match the marketing SPL value, which is generally somewhat vague. Not in all cases, though.

6. Correct *Znom*, if necessary.

If there are several voicecoils, then you must be careful when entering parameters in that case, because many manufacturers give *Bl* in voice coils in series, because it yields double value for Bl against parallel connection. If driver manufacturer gives *Qes*, *Bl* and *Cms* or *Mms*, then you can check how *Bl* is specified. For that, you can enter following parameters to calculate *Re*: *Qes*, *Fs*, *Mms* or *Cms* and *Bl*. Connection mode can be changed by changing the combobox selection. The driver editor then converts Bl and Re values accordingly.

Equivalently, you can check for *Bl* by entering:

*Qes*, *Fs*, *Mms* or *Cms* and *Re* (for desired connection mode).

If you enter resistance for parallel connection and get about half of advertised *Bl*, then you know, that *Bl* was specified that way.

Like in Driver-tab in project window, you'll probably noticed the driver icon in bottom of the driver editor window. you can drag the driver object into some project by just dragging the icon.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Hello:
> 
> So, I checked all the values, and they are all correct values and measurements, except Vd.
> --I believe Vd is the driver displacement? sorry, haven't done a build since about 1998.
> If Vd is the driver, then it's supposed to be 0.074'³. But, when i change it and try and save, winISD gives an error message.


Vd is calculated Displacement based on Sd (Cone Area) multiplied by Xmax.


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## rxh0272 (Jul 26, 2020)

daloudin said:


> The order of entering in driver data is also in the Help document in WinISD:
> Cut and pasted from WinISD Help document.
> The suggested procedure for entering driver parameters is following (check first that "Auto calculate unknowns" option is checked):
> 
> ...


Thank you much daloudin!

I found it in the Help section. I am basically reading the entire contents top-down. Haven't designed/built a system since 1998, and have to catch up. 

I entered the parameter again for the JL 10W0v3-4 (Just one of the subs I have loaded to model). 

I had to find the parameters because the manufacturers don't always put the values on their website/manuals. So found www.loudspeakerdatabase.com, which has all the parameters missing from JL's website. 

So I reentered the parameters in the correct order and tabbed through it. I then checked my previous W0v3-4 project and opened a new project using the correct parameters and sequence. I then opened the parameters box and compared. Result: The values are different! Some not by much, and some are the same. BUT, winISD didn't take the new overwritten parameters and change the previous project, so I need to start anew. 

Not a big deal. 

The 10W0v3-4: in ported, to get it tuned lower, the sub can only handle about 90w to prevent over excursion. The box is small: 1.3 cubic feet. 

It's a starting point, but I need to find a sub that functions in 1.3 and get low and loud, but still has extension (?) to play at low-moderate power and sound good. My last build, could only hear the sub at moderate-high levels, but mostly high.

Alright. I am also reading Introduction to Loudspeaker Design by John L. Murphy to add to my knowledge.


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## Destarah (Feb 24, 2019)

rxh0272 said:


> The link does go to anything.


Sorry about that, didn't realize I had created a bookmark in Chrome that pointed to the help file on my hard drive lol ... daloudin pasted the same info I was attempting to link to.



rxh0272 said:


> he 10W0v3-4: in ported, to get it tuned lower, the sub can only handle about 90w to prevent over excursion.


Especially when using a ported box, you need to add a high-pass filter in WinISD to simulate the subsonic filter you would need in real life. Put in the max RMS power under the Signal tab, then switch over to Excursion plot and add a 4th order LW high-pass filter at 20Hz ... if that doesn't get you under Xmax, keep increasing the frequency until it does.


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## daloudin (Nov 2, 2020)

Without getting real spendy (like $400 for a Morel Ultimate) the only 10" Sub that I know of that will work ported that small AND go fairly deep is the Dayton HO-4 (not the 44 it needs a bigger box) and the HO-4 (Single Voice Coil) actually would work with two of them in 1.3 cuft ported at 29.5Hz. See screenshots from WinISD (Note the Excursion has a 20Hz LR24 HP Filter added) below and note that the f3 is 34Hz (10" is red). You could do one 12 HO-44 in that size box and move the f3 down to 30Hz (12" is green) but with 3db less SPL at the same 1200 Watts.

Doubt you would be able to tell the difference once you got them installed with cabin gain. One 12 or 2 x 10s... probably more of an aesthetic choice than anything.


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## rxh0272 (Jul 26, 2020)

Destarah said:


> Sorry about that, didn't realize I had created a bookmark in Chrome that pointed to the help file on my hard drive lol ... daloudin pasted the same info I was attempting to link to.
> 
> 
> 
> Especially when using a ported box, you need to add a high-pass filter in WinISD to simulate the subsonic filter you would need in real life. Put in the max RMS power under the Signal tab, then switch over to Excursion plot and add a at 20Hz ... if that doesn't get you under Xmax, keep increasing the frequency until it does.





Destarah said:


> Sorry about that, didn't realize I had created a bookmark in Chrome that pointed to the help file on my hard drive lol ... daloudin pasted the same info I was attempting to link to.
> 
> 
> 
> Especially when using a ported box, you need to add a high-pass filter in WinISD to simulate the subsonic filter you would need in real life. Put in the max RMS power under the Signal tab, then switch over to Excursion plot and add a 4th order LW high-pass filter at 20Hz ... if that doesn't get you under Xmax, keep increasing the frequency until it does.


I changed the filter settings. Now: 300w signal @1.3 ft3 box tuned to 31Hz, ported with circular 4" port, 23" long, 111.720 SPL @ 53.39Hz, and is under the excursion limit with HPF set to 35Hz. 
--But the graph looks like crap to me. Am I wrong? 
--I'd like to find a sub that fits and can tune lower. I suppose it will be one at at a time.


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## rxh0272 (Jul 26, 2020)

daloudin said:


> Without getting real spendy (like $400 for a Morel Ultimate) the only 10" Sub that I know of that will work ported that small AND go fairly deep is the Dayton HO-4 (not the 44 it needs a bigger box) and the HO-4 (Single Voice Coil) actually would work with two of them in 1.3 cuft ported at 29.5Hz. See screenshots from WinISD (Note the Excursion has a 20Hz LR24 HP Filter added) below and note that the f3 is 34Hz (10" is red). You could do one 12 HO-44 in that size box and move the f3 down to 30Hz (12" is green) but with 3db less SPL at the same 1200 Watts.
> 
> Doubt you would be able to tell the difference once you got them installed with cabin gain. One 12 or 2 x 10s... probably more of an aesthetic choice than anything.
> View attachment 290328
> ...


Thanks man. I used a Dayton HO8" before because it was the only sub that would perform well in a 0.4 enclosure. But, it ended up blowing. I just needed more and ran it too hard. Pretty sure it was rated for 350w RMS, and I ran like 400 to it. So, I only presume that, if I am going to use another Dayton, it might as well be more capable than the last one was. But again, 0.4 enclosure, and people thought I had a 12" back there. haha. At least at 1.3 ish net I should be able to run Dayton and some others.
Any thoughts? Besides Dayton?


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Thanks man. I used a Dayton HO8" before because it was the only sub that would perform well in a 0.4 enclosure. But, it ended up blowing. I just needed more and ran it too hard. Pretty sure it was rated for 350w RMS, and I ran like 400 to it. So, I only presume that, if I am going to use another Dayton, it might as well be more capable than the last one was. But again, 0.4 enclosure, and people thought I had a 12" back there. haha. At least at 1.3 ish net I should be able to run Dayton and some others.
> Any thoughts? Besides Dayton?


I'm running a Dayton 10 HF-8 that's rated for 350W and 1ft³ in a 0.65ft³ Sealed with 1,000W and no problem. I can bottom the coil before the amp clips. Dayton Reference Subs can handle WAY more than they're rated for but it has to be clean with good voltage support. 

Other than Dayton or JL W6 (the W6 or the Slim series are the only JL subs "designed" for small enclosures) there's Morel Ultimate, ID Max, Adire Brahma, Sundown or Wavecor which will all work in that size. And all stomp on a P3 but you're in to the $300+ MAP.

AND if you're looking to slam (#basshead) don't forgo a 12 in that size sealed. One Brahma 12 in that box sealed or 3x10 Brahmas Sealed with enough power would be slamming in a little SUV.

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## Destarah (Feb 24, 2019)

You are forgetting the shallow subs, personally I have experience with the JL 10TW3 ... others have met with great success using a variety of manufacturers. Here is a 10TW3 in 1.3cuft tuned at 26Hz ... pretty freaking solid with a -3dB down at 25Hz. Tricky part is the long port (36"), but any amount of the port length can be outside the box, so you could have it go across the back of the trunk behind the seats /shrug


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## daloudin (Nov 2, 2020)

Destarah said:


> You are forgetting the shallow subs, personally I have experience with the JL 10TW3 ... others have met with great success using a variety of manufacturers. Here is a 10TW3 in 1.3cuft tuned at 26Hz ... pretty freaking solid with a -3dB down at 25Hz. Tricky part is the long port (36"), but any amount of the port length can be outside the box, so you could have it go across the back of the trunk behind the seats /shrug
> 
> View attachment 290360


Shallow... Slim. Tomato... Potatto.

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## rxh0272 (Jul 26, 2020)

daloudin said:


> I'm running a Dayton 10 HF-8 that's rated for 350W and 1ft³ in a 0.65ft³ Sealed with 1,000W and no problem. I can bottom the coil before the amp clips. Dayton Reference Subs can handle WAY more than they're rated for but it has to be clean with good voltage support.
> 
> Other than Dayton or JL W6 (the W6 or the Slim series are the only JL subs "designed" for small enclosures) there's Morel Ultimate, ID Max, Adire Brahma, Sundown or Wavecor which will all work in that size. And all stomp on a P3 but you're in to the $300+ MAP.
> 
> ...


Yeah, in the other form, people were stealing today 12 no work in that size


Destarah said:


> You are forgetting the shallow subs, personally I have experience with the JL 10TW3 ... others have met with great success using a variety of manufacturers. Here is a 10TW3 in 1.3cuft tuned at 26Hz ... pretty freaking solid with a -3dB down at 25Hz. Tricky part is the long port (36"), but any amount of the port length can be outside the box, so you could have it go across the back of the trunk behind the seats /shrug
> 
> View attachment 290360


ok. . So a graph like that is OK. I wasn’t 100% sure. I got a similar graph on the JL then I did boarded. -3dB at 25 Hertz It’s pretty good. I haven’t really looked too much into the shallow subs because I’m not really a fan of them. I do not see or believe that they can perform as well as a regular sub. A regular sub with a deep Cohen. But apparently from what I was told and learned through research is that the performance of the sub and I’It’s pretty good. I haven’t really looked too much into the shallow subs because I’m not really a fan of them. I do not see or believe that they can perform as well as a regular sub. A regular sub with a deep Cohen. But apparently from what I was told and learned through research is that the performance of the sub and Performance has nothing to do with depth of the cone. Is that true?
Also is the price point. The better performing sub for a lower price means that I can get a better amp that costs more. 
And that’s how I end up back at the Dayton

I could build the poor inside the box. I have never done a circular pour the Benz or snakes inside the box but I suppose in theory you could do it. However that will also lower the net volume


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## daloudin (Nov 2, 2020)

The shape of the cone has nothing to do with performance. Back to Thiele Small specifications and how a driver works. The cone is a piston, whether the shape is a cone, a "w" or flat like an actual piston doesn't matter. It's the radiating area (Sd) multiplied by the stroke (xmax) which yields Vd that tells you how much air a subwoofer can move. Shallow, Deep, Front Magnet, Rear Magnet how many spiders the suspension has, etc. Are all part of the design but are not part of how a sub will model (other than power handling.)

1.3 to 1.6 ft³ is plenty of space for any of a number of 12s or multiple 10s if they were designed for small boxes. 

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## rxh0272 (Jul 26, 2020)

Work has been filling my days. 

I'm modeling several subs in winISD Pro Alpha. Can anyone please tell me what the "Ripples" are? I mean, I can see them on the transfer function magnitude, but I don't know what they indicate or how to measure/what amount of ripple is acceptable. 

Thank You,
Rob


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Work has been filling my days.
> 
> I'm modeling several subs in winISD Pro Alpha. Can anyone please tell me what the "Ripples" are? I mean, I can see them on the transfer function magnitude, but I don't know what they indicate or how to measure/what amount of ripple is acceptable.
> 
> ...


A screenshot or pic of the ripple you are referring to would be  

In general 1db is the limit of what can be discerned by the human ear (smallest amount of change we can perceive) and 3db is the point at which it starts to really make a difference. Anything less than 3db will likely be absorbed by cabin gain and can easily be eq'd out if necessary. Some mfrs prefer small boxes (JL Audio) so that the 3db box gain helps level out the cabin gain in-car.

Pure SPL Burp builds try to match the peak of the box gain with the resonant frequency in-car to gain that extra free db from the sympathetic resonance. Or they used to before the massive amount of wattage available today. 

Ripples below the tuning point (RF P3 is known for this) are due to multiple resonant points in the design of the driver motor/suspension and are only a problem in ported designs where dampening goes out the window below tuning. (They have to be filtered out to prevent over excursion and bottoming the vc limiting output.)

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## rxh0272 (Jul 26, 2020)

daloudin said:


> A screenshot or pic of the ripple you are referring to would be
> 
> In general 1db is the limit of what can be discerned by the human ear (smallest amount of change we can perceive) and 3db is the point at which it starts to really make a difference. Anything less than 3db will likely be absorbed by cabin gain and can easily be eq'd out if necessary. Some mfrs prefer small boxes (JL Audio) so that the 3db box gain helps level out the cabin gain in-car.
> 
> ...


Thank you.
Sorry for late reply. 

The ripple are very small. Some models might have 1dB ish ripples, but like the JL below in the ported box, gray line, has some ripples around 0 dB


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## rxh0272 (Jul 26, 2020)

Is the excursion part of the simulator accurate? I ask because every box that winISD recommends over-excursion happens when signal power is put up to RMS level.


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## rxh0272 (Jul 26, 2020)

Hi guys:

Sorry, work sucks up a lot of my time.

I'm finding that JL subs tend to be easier to tune. But, general question: I read that the box/port of ported box should not be tuned below the Fs of the driver, as the driver will not effectively play under its Fs. Is this true?


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## Destarah (Feb 24, 2019)

The excursion part of the simulator is accurate, WinISD doesn't care about exceeding excursion ... it only tries to acheive the target response (typically as flat as possible). Apply a Highpass filter to control excursion, or reduce the box volume (which is typically what the manufacturers do).

Lowering the tuning frequency has the effect of extending the low frequency response of the driver well below the Fs, that is actually one of the main benefits. Tuning the box to the Fs of the driver delivers a nice boost above that frequency. Consider the following examples using a JL Audio 10TW3-D4 ... all using recommended 400W RMS, red is JL spec 0.5cuft sealed (no need for a subsonic filter), black is JL spec 0.6cuft ported tuned at 32.14Hz (LW 24dB subsonic filter set at 17.1Hz to control excursion), green is WinISD recommended 3.037cuft ported tuned at 21Hz (LW 24dB subsonic filter set at 15.35Hz to control excursion). As you can see the JL spec ported box has more output than sealed across the entire frequency range, and more than the WinISD spec above 40Hz. However, the WinISD option has flat response all the way down to 20Hz where it is still delivering a staggering 106.5dB compared to ~92dB for the others.









This is when Group Delay starts getting discussed ...


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Thank you.
> Sorry for late reply.
> 
> The ripple are very small. Some models might have 1dB ish ripples, but like the JL below in the ported box, gray line, has some ripples around 0 dB
> View attachment 290827


That 1db "ripple" on the grey line is box gain above Fs, if you tweak the box size up a little this swell above 0db will flatten out and if you decrease the box size then this will increase the magnitude of the ripple.

Having some box gain (due to a smaller than optimal box) is fine as long as it doesn't reduce your low frequency extension too much. Depending on your cabin gain (which is usually below 70Hz) it can actually make the sub easier to integrate. 

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## daloudin (Nov 2, 2020)

rxh0272 said:


> Is the excursion part of the simulator accurate? I ask because every box that winISD recommends over-excursion happens when signal power is put up to RMS level.


Yes, it's as accurate as the specifications you enter for each driver. Suspension compliance, motor force, moving mass, etc all play a role in that calculation. 

What you're finding is why JL recommends smaller than optimal (0.707 Q) boxes to help limit excursion and create low frequency rolloff.

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## daloudin (Nov 2, 2020)

rxh0272 said:


> Hi guys:
> 
> Sorry, work sucks up a lot of my time.
> 
> I'm finding that JL subs tend to be easier to tune. But, general question: I read that the box/port of ported box should not be tuned below the Fs of the driver, as the driver will not effectively play under its Fs. Is this true?


That's an over simplification or a generalization that's not always the case but for the most part it's true. 

Tuning below Fs of the driver will cause a reduction of response slightly above the tuning point and make the box peaky with less control of excursion at driver Fs which is the point of a ported box - limiting excursion where the driver is the most efficient and most likely to bottom out. 

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## rxh0272 (Jul 26, 2020)

Destarah said:


> The excursion part of the simulator is accurate, WinISD doesn't care about exceeding excursion ... it only tries to acheive the target response (typically as flat as possible). Apply a Highpass filter to control excursion, or reduce the box volume (which is typically what the manufacturers do).
> 
> Lowering the tuning frequency has the effect of extending the low frequency response of the driver well below the Fs, that is actually one of the main benefits. Tuning the box to the Fs of the driver delivers a nice boost above that frequency. Consider the following examples using a JL Audio 10TW3-D4 ... all using recommended 400W RMS, red is JL spec 0.5cuft sealed (no need for a subsonic filter), black is JL spec 0.6cuft ported tuned at 32.14Hz (LW 24dB subsonic filter set at 17.1Hz to control excursion), green is WinISD recommended 3.037cuft ported tuned at 21Hz (LW 24dB subsonic filter set at 15.35Hz to control excursion). As you can see the JL spec ported box has more output than sealed across the entire frequency range, and more than the WinISD spec above 40Hz. However, the WinISD option has flat response all the way down to 20Hz where it is still delivering a staggering 106.5dB compared to ~92dB for the others.
> View attachment 290873
> ...


Thank you very much. It’s more clear now. So basically once the box and tuning Hz is chosen, modify port, or box size for sealed, until desired effect reached, but balance it with group delay, max power, excursion, etc.

i have been using a HPF to keep excursion under control. The Nguyen ISD recommended enclosure really bumps. Better than a peek at 50 Hz. I have not modeled the JL shallow mount yet. I plan to do that tonight
I could actually double my box size. Right now, i was trying to only use half of the trunk space. And It will be down firing. So I figure out about 8 inches tall it will not be so tall that it will impede usage of the trunk.

if I double it, extending the box across the entire width of the trunk, then I will have approximately 2.6 ft.³. It’s actually bigger than that, but that includes a rough estimate of woofer displacement and vent displacement subtracted already.

The other problem I’m having is that in the maximum power a graph I am seeing a dip in power at approximately 40 Hz where power is zero, so I only can presume that at zero W at 40 Hz the woofer is reaching its maximum X max

can you tune out those power dips? Because I did run the JLW1V3-2 at 1.3 ft.³ ported, and I had a very minimal dip on the power maximum graph

I plan to model a 10 and 12 JL shower now tonight.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> The other problem I’m having is that in the maximum power a graph I am seeing a dip in power at approximately 40 Hz where power is zero, so I only can presume that at zero W at 40 Hz the woofer is reaching its max...


The maximum power calculation gives you an idea of what the driver can absorb at any particular frequency without any power compression effects or reaching xmax as you've suggested. If the graph drops to zero at 40hz while the rest of the curve is at 500 (or more or less) Watts then you've got a problem that would indicate a possible resonance issue or one of the driver specs is wrong or you've got a ported box tuned to 50hz and lost all cone control below that...

You can tune it out of the box but I would be researching why WinISD is predicting that in the first place. 

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## rxh0272 (Jul 26, 2020)

daloudin said:


> The maximum power calculation gives you an idea of what the driver can absorb at any particular frequency without any power compression effects or reaching xmax as you've suggested. If the graph drops to zero at 40hz while the rest of the curve is at 500 (or more or less) Watts then you've got a problem that would indicate a possible resonance issue or one of the driver specs is wrong or you've got a ported box tuned to 50hz and lost all cone control below that...
> 
> You can tune it out of the box but I would be researching why WinISD is predicting that in the first place.
> 
> Sent from my SM-G965U using Tapatalk


Ya. I’ve been researching and reading all the Help info


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## rxh0272 (Jul 26, 2020)

daloudin said:


> The maximum power calculation gives you an idea of what the driver can absorb at any particular frequency without any power compression effects or reaching xmax as you've suggested. If the graph drops to zero at 40hz while the rest of the curve is at 500 (or more or less) Watts then you've got a problem that would indicate a possible resonance issue or one of the driver specs is wrong or you've got a ported box tuned to 50hz and lost all cone control below that...
> 
> You can tune it out of the box but I would be researching why WinISD is predicting that in the first place.
> 
> Sent from my SM-G965U using Tapatalk


Ok. So on this model, the max. power graph shows max 300w is 24Hz to 29Hz, then there's a dip down to 215W @ 37Hz then goes back


daloudin said:


> The maximum power calculation gives you an idea of what the driver can absorb at any particular frequency without any power compression effects or reaching xmax as you've suggested. If the graph drops to zero at 40hz while the rest of the curve is at 500 (or more or less) Watts then you've got a problem that would indicate a possible resonance issue or one of the driver specs is wrong or you've got a ported box tuned to 50hz and lost all cone control below that...
> 
> You can tune it out of the box but I would be researching why WinISD is predicting that in the first place.
> 
> Sent from my SM-G965U using Tapatalk











This is JL 10TW-2 at the winISD recommended 1.7ft3 box, ported, 4" port 26" long. 
max power seen at 24-30Hz, then dip is 30-49Hz with lowest power 215W, then goes back up to 300W.
---Is that dip a problem? 
So, basically at the lowest part of the dip, only 215W is needed to reach Xmax? And if so, then would that be a way to damage the sub ?


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## SWRocket (Jul 23, 2010)

What is the box tuned at? You have a HP filter at 32Hz which seems high...should be half octave below tuning as far as I know.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Ok. So on this model, the max. power graph shows max 300w is 24Hz to 29Hz, then there's a dip down to 215W @ 37Hz then goes back
> 
> View attachment 291318
> 
> ...


That's what it's predicting, yes. 

It's easier to see if you look at the excursion plot of the same model. 

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## rxh0272 (Jul 26, 2020)

SWRocket said:


> What is the box tuned at? You have a HP filter at 32Hz which seems high...should be half octave below tuning as far as I know.


It is tuned at 26Hz. The thing is that winISD made a 1.7ft3. It looked great. But then I tried to replicate JL recommended box, and that turned out to be ****ty. Anyway, I had to increase the LPF to 27Hz to prevent the excursion curve from going beyond the speaker's Xmax. 










And here is the excursion chart










Here is the original tune by winISD


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## Destarah (Feb 24, 2019)

The Maximum power and Maximum SPL graphs both respresent theoretical limits imposed by excursion. The dip you are seeing shows that in that frequency range it takes less than rated RMS to reach Xmax. This graph (and Maximum SPL) ignore variables you have included (filters, System input power) and just show the excursion-imposed limits.
That Rear port - Air velocity graph you posted shows that you are over 30m/s which indicates that you may want to increase the port area so that you don't hear chuffing.

WinISD prioritizes a flat response curve, JL has a more realistic approach to designing their enclosures. Basically they want something that will actually fit in a vehicle, and still sound good doing it (with the help of cabin gain). It's in their best interest to get the box size as small as possible without sacrificing too much low frequency response ... also helps with warranty claims from people bottoming out the subs because of a huge box and no subsonic filter.


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## rxh0272 (Jul 26, 2020)

Destarah said:


> The Maximum power and Maximum SPL graphs both respresent theoretical limits imposed by excursion. The dip you are seeing shows that in that frequency range it takes less than rated RMS to reach Xmax. This graph (and Maximum SPL) ignore variables you have included (filters, System input power) and just show the excursion-imposed limits.
> That Rear port - Air velocity graph you posted shows that you are over 30m/s which indicates that you may want to increase the port area so that you don't hear chuffing.
> 
> WinISD prioritizes a flat response curve, JL has a more realistic approach to designing their enclosures. Basically they want something that will actually fit in a vehicle, and still sound good doing it (with the help of cabin gain). It's in their best interest to get the box size as small as possible without sacrificing too much low frequency response ... also helps with warranty claims from people bottoming out the subs because of a huge box and no subsonic filter.


OK. Thank you. 
But, what happens during playing music and the music in that dip range? Does one run the risk of blowing the sub in that Hz range? Or is it more of that when playing music, the changes occur so fast that the sub will not pass excursion. 

Maybe I have it wrong. So basically, that dip region means that the sub will only require 215w in order to hit Xmax. So, if I'm running 300w RMS to the sub, will it over exert the sub, since it would be running 85 w higher?


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## Destarah (Feb 24, 2019)

rxh0272 said:


> So, if I'm running 300w RMS to the sub, will it over exert the sub, since it would be running 85 w higher?


Xmax is a measurement limited by an acceptable distortion level, not the mechanical limit of the driver. Besides that fact, the power output of the amplifier is constantly changing while music is being played.


daloudin said:


> You can tune it out of the box but I would be researching why WinISD is predicting that in the first place.


The maximum power dip that you are seeing between 30Hz and 49Hz is due to the high FS of the driver, here is what it looks like compared to sealed ... power handling below FS is bolstered by porting the box.









In order to maintain power handling without having that dip you would need to bring the tuning point up to 36Hz ... here is what that looks like









Still a vast improvement over the sealed option, your 300W power handling is extended all the way down to 33Hz


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## rxh0272 (Jul 26, 2020)

Destarah said:


> Xmax is a measurement limited by an acceptable distortion level, not the mechanical limit of the driver. Besides that fact, the power output of the amplifier is constantly changing while music is being played.
> 
> The maximum power dip that you are seeing between 30Hz and 49Hz is due to the high FS of the driver, here is what it looks like compared to sealed ... power handling below FS is bolstered by porting the box.
> View attachment 291544
> ...


OK. Very Helpful
So, don't confuse Xmax with Xmech.
--So, I did similar, which is to shift the curve right by increasing tuning Hz of the system/enclosure. That's what I did. 

Gray is my box size. Purple is the winISD box. I had to modify the tuning Hz on both to prevent the power dip. I also had to raise the tuning Hz of the boxes and adjusted the ports to flatten out the responses.
Alright. After messing around with winISD for like an hour, I came up with the below. 
The main difference is Gray is my 1.4 box and purple is winISD's rec. 1.7 box.











Below, I suppose the boxes might be a little peaky, but pretty hard to find a good balance between all parameters. 



















They both follow a very similar path. 



















Any thoughts? It's pretty much a compromise. Can't have tuning in the 20s and not a ridiculous port, or or it becomes very peaky.


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## Destarah (Feb 24, 2019)

The 1.7cuft recommended by WinISD is necessary for the very low tuning point that they aim for. As you raise the tuning point it makes a lot of sense to decrease the volume. So I say have at it with the 1.4cuft tuned at 36Hz


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## rxh0272 (Jul 26, 2020)

Destarah said:


> The 1.7cuft recommended by WinISD is necessary for the very low tuning point that they aim for. As you raise the tuning point it makes a lot of sense to decrease the volume. So I say have at it with the 1.4cuft tuned at 36Hz


Ok. So, the winISD 1.7 cube box tuned low, but over excursion and port was unreal. Made everything so it works, and hen tuning not much off from the 1.4
--So, your vote is he 1.4. Thank you for your input. 
--If you don't mind, what about the bump seen on the Transfer Function Magnitude to about +3 dB over the reference point? And, does it seem like I have the correct approach to using winISD Pro? balancing the graphing, etc.


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## rxh0272 (Jul 26, 2020)

I did a lot of modeling. 
I decided to go the entire floor, making a false floor in the back. So this now increases my internal volume to 2.43-2.87. And with that, it's a lot easier to tune the box down lower, like in the 20s at -3dB.


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## Destarah (Feb 24, 2019)

Tuning that particular speaker below 36Hz isn't really an optimal approach. As you have seen, it will impact power handling and you will get a dip in response between the tuning frequency and FS. If you have the option of making the volume that much larger I would definitely recommend using a different sub, what is your max mounting depth with the 2.8cuft option?


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## rxh0272 (Jul 26, 2020)

Destarah said:


> Tuning that particular speaker below 36Hz isn't really an optimal approach. As you have seen, it will impact power handling and you will get a dip in response between the tuning frequency and FS. If you have the option of making the volume that much larger I would definitely recommend using a different sub, what is your max mounting depth with the 2.8cuft option?


6.5” interior dimension or 7.25 top mount depth (.750 wood). 8” exterior dimension. 
That’s too why I asked about tuning below the sub’s Fs, resonant frequency. Some said it's fine, but I didn't think so; however, I lack the experience/knowledge to actually know.
I am open to other subs. Just kind of going one-by-one modeling them to find the right one.


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## Destarah (Feb 24, 2019)

Tuning at 36Hz is below that subs FS, by a fair margin actually ... my point was that lowing the tuning below 36Hz exposes the sub to being easily pushed past it's limits.
Sounds like you should be looking towards the pair of Dayton HO-4 10" as mentioned earlier by daloudin


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## daloudin (Nov 2, 2020)

At that size box I'd be looking at dual 12HO ported or one 15 maybe.

Edit: went looking for the lowest F3 you could get with 2.8 ft^3 and found Dayton Ultimax 12-22 will get down to 18.3Hz in that size box:

























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## Fish Chris 2 (Dec 18, 2019)

Out of the 30+ enclosures I've built, I don't think I've ever built one without either just going with the manufacturers recommendations, OR, a lot of the time, I've called and chatted with a tech guy for the manufacturer. So by the time I start building the enclosure, I already know it's going to work decently well.


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## 156546 (Feb 10, 2017)

When you put the sub in a box, there is no more Fs. It becomes Fc and we ALMOST ALWAYS tune for a subwoofer below what the Fc would be if the box was sealed.


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## rxh0272 (Jul 26, 2020)

GotFrogs said:


> When you put the sub in a box, there is no more Fs. It becomes Fc and we ALMOST ALWAYS tune for a subwoofer below what the Fc would be if the box was sealed.


yup! I noticed the typo after the fact. 
So, correct me, if I am wrong: Since fc will always be higher than the fs, for any given driver, when placed into a sealed enclosure. So tuning can be done based off of this, say in winISD, and tuned lower than the fc hoping to get the speaker box system tuned at the goal. So, tune for 25 Hz to get 30Hz. ? But, I'm still confused about whether or not it is safe to tune the system with ported box tuned below the sub's fs because I've read in my research that doing so can cause the sub to blow when trying to play Hz below it's fs and capabilities. Or, at least power handling goes down at such frequencies, and thus blow, unless power is turned down.


Fish Chris 2 said:


> Out of the 30+ enclosures I've built, I don't think I've ever built one without either just going with the manufacturers recommendations, OR, a lot of the time, I've called and chatted with a tech guy for the manufacturer. So by the time I start building the enclosure, I already know it's going to work decently well.


Thank you. 
Ya, back in the '90s I would build based on spec sheets for the woofer. I changed the box sizes, etc. sometimes. I was just a kid then, and surprised I was even able to do the design and build and keep all my fingers. 

One thing is that when I take the OEM specs and try and model the box-sub to OEM specs in winISD, I can't get the boxes tuned to OEM specs, using their recommended sizes, ports, etc.


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## rxh0272 (Jul 26, 2020)

GotFrogs said:


> When you put the sub in a box, there is no more Fs. It becomes Fc and we ALMOST ALWAYS tune for a subwoofer below what the Fc would be if the box was sealed.


Ya. I noticed after the fact of the typo. 
My understanding is that the fc is always higher than the fs for any given sub when in a sealed box. So, I suppose shooting for tuning lower than what it would be in a sealed enclosure would hopefully get the sub-box system to the desired tuning. 
Is the fs actually used for much?


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Ya. I noticed after the fact of the typo.
> My understanding is that the fc is always higher than the fs for any given sub when in a sealed box. So, I suppose shooting for tuning lower than what it would be in a sealed enclosure would hopefully get the sub-box system to the desired tuning.
> Is the fs actually used for much?


Resonant frequency is determined by the interaction of all the components used to manufacture a driver and how they interact with each other and is simply the frequency at which the driver is MOST efficient meaning that it will handle the least amount of power at that frequency since it will reach mechanical limits easiest at that frequency. Tuning a ported box to that frequency reduces excursion at and just around this frequency to compensate leveling out the response. Running or tuning below Fs is often recommended to extend the driver's low frequency response and as mentioned earlier changes the natural Fs to Fc which is now based on the combination of driver, box and port tuning. This can all be modeled in s/w like WinISD and mechanical excursion limits predicted with a high degree of accuracy. (Results are dependent on accuracy of box building and tuning along with the accuracy of T/S specs - thus the reason that better box builders use speaker measuring like DATS on every driver before building to confirm specs and after building to confirm modeling.) The danger to the driver comes from playing frequencies BELOW the tuning frequency of the port where there's no control over cone movement and excursion limits can easily be exceeded with very little power. 

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## rxh0272 (Jul 26, 2020)

daloudin said:


> Resonant frequency is determined by the interaction of all the components used to manufacture a driver and how they interact with each other and is simply the frequency at which the driver is MOST efficient meaning that it will handle the least amount of power at that frequency since it will reach mechanical limits easiest at that frequency. Tuning a ported box to that frequency reduces excursion at and just around this frequency to compensate leveling out the response. Running or tuning below Fs is often recommended to extend the driver's low frequency response and as mentioned earlier changes the natural Fs to Fc which is now based on the combination of driver, box and port tuning. This can all be modeled in s/w like WinISD and mechanical excursion limits predicted with a high degree of accuracy. (Results are dependent on accuracy of box building and tuning along with the accuracy of T/S specs - thus the reason that better box builders use speaker measuring like DATS on every driver before building to confirm specs and after building to confirm modeling.) The danger to the driver comes from playing frequencies BELOW the tuning frequency of the port where there's no control over cone movement and excursion limits can easily be exceeded with very little power.
> 
> Sent from my SM-G965U using Tapatalk


Thanks a lot for explaining. I usually respond faster, but very long week.

So, essentially the system (sub+box) ported design should be at or above the Fs, but can tune below, if necessary, to compensate for system response. So if I want low bass, I need a driver that has a specified low Fs to start with, yes?

Then, I can tune it slightly under the Fs, if necessary, but how much does the Fc need to be below the Fs before it becomes too much lower than the sub can handle? Or, maybe I'm seeing this wrong--maybe it's that the system Fc can be lower than the sub's Fs because of the port tuning, thus helping to prevent over excursion, but then run a HPF at the port tuning Hz. I suppose if the system is designed very well, the HPF might not be as necessary as if otherwise.

I don't have much space, and I want low bass that can get pretty loud, when wanted. I'm only working with ~ 1.39-2.73 ft³. I also decided to run ported, if I can design it, because I can't get a sub sealed box modeled in winISD Pro that plays with an f3 around 30Hz or so in the limited space I have. RF P310" seems to work, otherwise Dayton, which a few others recommended/suggested. I checked some JL shallow mount subs (down firing box is the plan), and they are easier to model for some reason, but also cost more.

If I can't get the box design correct, then hell, I might have to stick with a sealed box. I've always ran sealed and would build sealed back in the 90s. It's just what I learned to do well. But, in this case, ported seems the way to go.

DATS: I've looked into the, but I'm not building enough to justify buying the gear.


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## Destarah (Feb 24, 2019)

I just finished reading through this thread again from scratch ... there have been significant changes to the parameters that you are working with along the way. I think it would be helpful to regroup here and define the boundaries that you are now working with.
For example: what is your budget for the sub(s)?
Are you comfortable using 2.73cuft (and will that include the displacement of driver/port)?


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## daloudin (Nov 2, 2020)

Destarah said:


> I just finished reading through this thread again from scratch ... there have been significant changes to the parameters that you are working with along the way. I think it would be helpful to regroup here and define the boundaries that you are now working with.
> For example: what is your budget for the sub(s)?
> Are you comfortable using 2.73cuft (and will that include the displacement of driver/port)?


^^^Agreed

Let's redefine and see where it goes with Ported.
Maximum unloaded airspace before Ports or Sub?
Approximate dimensions so we can discuss things like mounting depth and port dimensions.
Budget for Sub alone - not the box or the amp just the Sub?
The Dayton 12HO-44 works in a really small ported box but keep in mind you can't beat the laws of physics and the smaller the box the harder it is to port deep. WinISD won't take into consideration that you can't port a 2 cuft box at 20Hz without putting most of the port tube outside the box - it only tells you what the model predicts - not if the box is readily buildable.


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## rxh0272 (Jul 26, 2020)

Destarah said:


> I just finished reading through this thread again from scratch ... there have been significant changes to the parameters that you are working with along the way. I think it would be helpful to regroup here and define the boundaries that you are now working with.
> For example: what is your budget for the sub(s)?
> Are you comfortable using 2.73cuft (and will that include the displacement of driver/port)?


A. Yes, I like the 2.73 because 7" is less aggressive than 8" thus less noticeable. It also just look better. 
B. Yes, the sizes are internals and include displacement of sub+port, which in this case means I need to subtract the port+sub displacement from the volume and figure out what I have. I figure subtract about 20% ish. So, that is 2.184ft³ and then add the sub+port displacement to that.
C. ---Costs willing to pay-----Sub: OK with $200-300 range. Amp $300-400 or less. I'm looking to have capability of 700-1,000wRMS, with sub around 500-700-1,000 wRMS rating range. I want goo headroom. 

I originally measured and calculated the original size and for the sub to only be on the left side, down firing. I realized my measurements must be wrong, so I better measured. Then, after sub to sub to sub, I couldn't find a sub to work in such small spaces and also go low and get loud enough, so I came to running ported. Back in the '90s, I only built sealed enclosures and like them, but this sub I want as low Hz as I can.

D. -------So, I decided to double the size--full left-right false floor. I took tens of measurements and came up with the finals following. Note that all are planned to be down firing and all cubic feet is internal using 3/4" MDF/birch without sub/port displacement subtracted: 
(a) 7" tall left side only = 1.39cu³, 
(b) 7" full false floor = 2.73ft³, 
(3) 8" left side only = 1.63ft³, 
and finally (d) 8" tall full false floor = 3.22ft³. 
The 7" and 8" tall is exterior. The cubes are internal. So, need to add clearance for down firing. I test fitted some cardboard and 7" is less of an issue than 8" tall. 

I've been running models in winISD Pro. JL are easiest to tune for some reason, Dayton performs pretty well, but the last Dayton I had blew too easily and lost bass after broken in. P3 is harder to tune. Not sure what else.



-----I ended up at the same subs over the past few weeks: RF P3, Dayton HO?, JL shallow mount. I suppose I could use another shallow mount, but using a double baffle means I can likely run a deeper sub.


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## Destarah (Feb 24, 2019)

Maybe I am oversimplifying this, but the 10TW3 in 2.2cuft tuned at 23Hz would be excellent. I am thrilled with it's output in a 0.6cuft sealed box with only 300W, I imagine it would be significantly more impressive tuned at 23Hz with 400W.


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## rxh0272 (Jul 26, 2020)

Destarah said:


> Maybe I am oversimplifying this, but the 10TW3 in 2.2cuft tuned at 23Hz would be excellent. I am thrilled with it's output in a 0.6cuft sealed box with only 300W, I imagine it would be significantly more impressive tuned at 23Hz with 400W.


I agree. Thing is that I’m still confused about the port tuning. From what I understand the poor tuning frequency allows waves at Or below the tuning frequency to patch through the port but any frequencies above the port tuning frequency will be blocked by the port.
Is that correct?

and, the sub- box is it’s own system and the system has its own resident frequency. From what others have said that sounds that you can tune a port below the FS because the system tuning frequency will prevent the subwoofer from over excursion.Fs becomes Fc


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## daloudin (Nov 2, 2020)

No, the port does not block anything it is simply less capable of passing certain frequencies. Both Fs and Qts change based on the box and/or tuning. As a result the impedance curve (or rise) changes as well. It's the difference between a driver and a speaker since, once combined, they measure as a unit. The port frequency defines the resonance of the combination which simply means the cone will move the least at that frequency. The port itself actually contains at least some of all the frequencies the driver produces. It's simply more efficient at certain frequencies. Regardless of what that eventual tuning point is though, you HAVE to HP about 1/2 octave below this frequency to prevent accidentally damaging your driver at frequencies where this no longer any dampening. 

The real challenge is in tuning the system to match the vehicle. Putting a huge box tuned to 18Hz in a car or suv will give you a huge bottom end but likely at the expense of being able to blend it in to the rest of your system since at frequencies above the cabin gain frequency of the vehicle it will have a lack of response in comparison to the combination of port gain and cabin gain. Its the reason that companies like JL specify smaller than optimum sealed enclosures and use the enclosure gain to compensate while additionally increasing power handling and creating a natural roll off to prevent overexcursion. Finding the optimum ported enclosure requires knowledge of what the optimum ported size and frequency is for the driver and then using your vehicles transfer function to figure out what the optimum ported size and frequency is for your car.

The only way to do this entirely accurately is to take a subwoofer with a known anechoic (free air) response and use it to plot the transfer function of your vehicle. I'm currently in the process of doing this with my vehicle and it's even more complicated than it sounds. 

Sent from my SM-G965U using Tapatalk


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## LBaudio (Jan 9, 2009)

Bass Reflex, Helmholz resonator, Port, Vent - all names for the same thing, last two are somehow self explanatory. port only works in narrow freq. range arround the choosen tunning frequency and with freq goes up it "closes". Your ported enclosure should be airtight, no matter that there is a large opening-Port. You can see the area-bandwith where port works in a graphs when calculating enclosure /acoustic power graph). Cone excursion at the tunning is at minimal. 1/3 octave bellow tunning cone will start to loose control, and you can face overexcursion/bottoming of the vc, but you can combat that issue with subsonic filter which will filter out the lowest freqs and prevent overexcursion of the cone.


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## rxh0272 (Jul 26, 2020)

Thanks a lot guys. I appreciate it. By now, I've probably asked the same questions 'round and 'round. But, I believe I get it now.


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## rxh0272 (Jul 26, 2020)

LBaudio said:


> Bass Reflex, Helmholz resonator, Port, Vent - all names for the same thing, last two are somehow self explanatory. port only works in narrow freq. range arround the choosen tunning frequency and with freq goes up it "closes". Your ported enclosure should be airtight, no matter that there is a large opening-Port. You can see the area-bandwith where port works in a graphs when calculating enclosure /acoustic power graph). Cone excursion at the tunning is at minimal. 1/3 octave bellow tunning cone will start to loose control, and you can face overexcursion/bottoming of the vc, but you can combat that issue with subsonic filter which will filter out the lowest freqs and prevent overexcursion of the cone.


OK. Thanks a lot for the input. sorry for the late response. Damn job is taking over my life.

Some responses are not always corrent, but it's good to see the ones that are.
From my research, Hz > 1 octave above port tuning Hz will not be permitted, and port will block the waves from exiting.
Then, 1/3 octave below port tuning Hz = port air vibrates, reducing sub vibration
the amplitude heads to zero at the tuning Hz. 

OK. So, if I tuned the ported enclosure to 25Hz, so Fb = 25Hz, then between ~ 21Hz (1/3 octave) to 50Hz is where I would get the most SPL. Correct? And, I can always adjust HPF to prevent over excursion. 

Been reading, "Introduction to Loudspeaker Design" eBook. very interesting.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> OK. Thanks a lot for the input. sorry for the late response. Damn job is taking over my life.
> 
> Some responses are not always corrent, but it's good to see the ones that are.
> From my research, Hz > 1 octave above port tuning Hz will not be permitted, and port will block the waves from exiting.
> ...


Model it in WinISD and then click on Port Transfer Function and it will show you the range of frequencies. 

Sent from my SM-G965U using Tapatalk


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## JohnnyOhh (Feb 19, 2015)

Hey once you build a ported box, if you install the woofer, you can measure the tuning frequency, correct?

I think it involves something like measuring the woofer's resistance at different frequencies, then graphing the results and looking for peaks/valleys.

That would be a nice way to round out all of the simulation/up-front analysis.


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## rxh0272 (Jul 26, 2020)

JohnnyOhh said:


> Hey once you build a ported box, if you install the woofer, you can measure the tuning frequency, correct?
> 
> I think it involves something like measuring the woofer's resistance at different frequencies, then graphing the results and looking for peaks/valleys.
> 
> That would be a nice way to round out all of the simulation/up-front analysis.


To my knowledge, yes. But, I need at least some software, at minimum, and some hardware. But, it doesn't replace the design phase up front. Goal is to be front heavy so that after built and installed I would need less after-the-fact analysis and re-tuning, or even rebuilding. 
I've only ever designed several ported boxes, and that was back in the '90s. I typically would design and build sealed enclosures. I want to run ported this time because it's the only way to get as low as I want to go, but someone commented and gave a practical advise that some subs sealed can have an f3 of 30Hz or so, and he made a great point.
If I can get the right sub in a sealed enclosure to play low, then that would be the easiest way of doing this. I would really prefer to not have to build the enclosure more than once. If it comes out a little off, i can tune the system. But, if too wrong, then ... uhh. ya. 

There are SMD meters that can measure the sub at specific frequencies, which is great, except I can't afford those tools, and I never needed one before, so why now? I could usually tune a system by ear and get really close to peak and where the customer or I wanted. I can still do that, it just takes time. And, sometimes I need to add components.


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## mrexcitement (Jan 23, 2019)

I prefer to build the box as per WinISD recommendations and then tune out the hump with a DSP , you can always reduce too much bass but you can't magically pull it out of nowhere if you don't have it to begin with.
I have never liked sealed for bass duty as I'm a bass head and a well designed ported setup with low tuning always sounded better to me.

And yes you can measure the tuning frequency after you have built the ported cabinet , I use a signal generator and a o-scope but a multimeter would also do. You vary the frequency while looking at the voltage , there will be 2 peaks (highest voltage measured) , the dip (minimum voltage measured) between the 2 peaks is the tuning frequency of the box.


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## BJG (Feb 7, 2021)

Please know that I follow ALL WinISD related threads and am NOT trying to hijack this one! However, I have never heard WinISD *PRO*.. Would one of you please be so kind as to give me a direct link to the best version of WinISD or whatever version you guys are all using?

Thanks,
Ben


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## daloudin (Nov 2, 2020)

BJG said:


> Please know that I follow ALL WinISD related threads and am NOT trying to hijack this one! However, I have never heard WinISD *PRO*.. Would one of you please be so kind as to give me a direct link to the best version of WinISD or whatever version you guys are all using?
> 
> Thanks,
> Ben


WinISD Pro is an older version... stick with whatever the newest version is on the Linear Team website for the best experience: WinISD - Linearteam


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## BJG (Feb 7, 2021)

daloudin said:


> WinISD Pro is an older version... stick with whatever the newest version is on the Linear Team website for the best experience: WinISD - Linearteam



Thank you!!!


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## JohnnyOhh (Feb 19, 2015)

@mrexcitement cool! what voltage (roughly) do you drive the woofer at when you are testing? you use sine wave sweep, i assume? the voltage changes through the sweep.... do you set voltage to like ~1.0V RMS or something?

totally agree that you would want to make the analysis front heavy, because fixing/re-working a box would suck, but always good to test something after you make it, to make sure it does what you intended, imo.



mrexcitement said:


> I prefer to build the box as per WinISD recommendations and then tune out the hump with a DSP , you can always reduce too much bass but you can't magically pull it out of nowhere if you don't have it to begin with.
> I have never liked sealed for bass duty as I'm a bass head and a well designed ported setup with low tuning always sounded better to me.
> 
> And yes you can measure the tuning frequency after you have built the ported cabinet , I use a signal generator and a o-scope but a multimeter would also do. You vary the frequency while looking at the voltage , there will be 2 peaks (highest voltage measured) , the dip (minimum voltage measured) between the 2 peaks is the tuning frequency of the box.


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## mrexcitement (Jan 23, 2019)

The voltage is not that important as long as the source is not clipping , I generally do it at roughly 2 - 4 volts peak to peak , it mostly depends on your source voltage output capabilities.

Yes just set it to sine wave and slowly vary the frequency up and down while monitoring the voltage and you will see it will peak (highest voltage) then dip (lowest voltage) then peak again , so you are looking for the dip in between the 2 peaks and that's your boxes tuned frequency , I always verify any ported box I build this way to confirm my port calculations have turned out correct.


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## JohnnyOhh (Feb 19, 2015)

totally yes. would a car audio amplifier that is set to a low level be able to do this also? These are constant voltage outputs, so maybe that would not work. Or maybe you need to measure the current going through the speaker, if you would use an amplifier?

is the signal generator you use constant current device?



mrexcitement said:


> The voltage is not that important as long as the source is not clipping , I generally do it at roughly 2 - 4 volts peak to peak , it mostly depends on your source voltage output capabilities.
> 
> Yes just set it to sine wave and slowly vary the frequency up and down while monitoring the voltage and you will see it will peak (highest voltage) then dip (lowest voltage) then peak again , so you are looking for the dip in between the 2 peaks and that's your boxes tuned frequency , I always verify any ported box I build this way to confirm my port calculations have turned out correct.


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## mrexcitement (Jan 23, 2019)

No the amp will make it hard to find the dip , just a low voltage signal generator is what I use.

Something like this would do , you can find them on Ebay

Also they are very handy to have for general audio testing.


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## Holmz (Jul 12, 2017)

mrexcitement said:


> No the amp will make it hard to find the dip , just a low voltage signal generator is what I use.
> 
> Something like this would do , you can find them on Ebay
> 
> ...


Could one run the amp through say an 8ohm power resistor and measure voltage at the speaker?


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## mrexcitement (Jan 23, 2019)

Yes you could add a resistor but it would more likely need to be about 570 Ohms 1/4 watt as the currents will be low , I am pretty sure the output impedance of the signal generator I use is about 600 ohm , the lower the impedance the less voltage change you will see at the speaker.


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## BJG (Feb 7, 2021)

Holmz said:


> Could one run the amp through say an 8ohm power resistor and measure voltage at the speaker?


Took the words right out of my mouth LOL


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## Holmz (Jul 12, 2017)

BJG said:


> Took the words right out of my mouth LOL


I finds it hard to resist.


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## rxh0272 (Jul 26, 2020)

JohnnyOhh said:


> @mrexcitement cool! what voltage (roughly) do you drive the woofer at when you are testing? you use sine wave sweep, i assume? the voltage changes through the sweep.... do you set voltage to like ~1.0V RMS or something?
> 
> totally agree that you would want to make the analysis front heavy, because fixing/re-working a box would suck, but always good to test something after you make it, to make sure it does what you intended, imo.


I agree. Have to do both.


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## rxh0272 (Jul 26, 2020)

Wait a minute. The Qts is total Q of the sub, correct? Qts = Qes * Qms. So, is higher Qts or lower Qts more stiff of a suspension system? Because research indicates Qts < 0.4 = good for vented box. 

So, if I want to get low, and run ported, I need a sub capable of Qts < 0.4 and Fs somewhere around 30 or less, or at least that's how low I want it to go. I have limited space, so challenge is getting the tuning I want within the constraints.


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## daloudin (Nov 2, 2020)

No, not necessarily. It's not that simple. You can have Q of any value and still get deep(er) depending on other parameters. But what IS generally true is that a lower Qts will generally work better in a smaller box before getting peaky. You want to aim for an enclosure that is going to keep the Qtc at 0.7 or lower to keep the low end extension. Aiming for 0.4 will put you in Infinite Baffle territory and reduce power handling without the airspring of a sealed enclosure or a really small ported tuned really deep.

You can use the Efficiency Bandwidth Product to find drivers that work best in only ported or sealed but most mobile audio drivers today ride the fence in the middle and will work either way if you size the enclosure correctly. 

Sent from my SM-G965U using Tapatalk


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## rxh0272 (Jul 26, 2020)

daloudin said:


> No, not necessarily. It's not that simple. You can have Q of any value and still get deep(er) depending on other parameters. But what IS generally true is that a lower Qts will generally work better in a smaller box before getting peaky. You want to aim for an enclosure that is going to keep the Qtc at 0.7 or lower to keep the low end extension. Aiming for 0.4 will put you in Infinite Baffle territory and reduce power handling without the airspring of a sealed enclosure or a really small ported tuned really deep.
> 
> You can use the Efficiency Bandwidth Product to find drivers that work best in only ported or sealed but most mobile audio drivers today ride the fence in the middle and will work either way if you size the enclosure correctly.
> 
> Sent from my SM-G965U using Tapatalk


Thank you very muc hfor the feedback. Sorry too. Got laid off and needed new job, and that sucked up my time. 

When using winISD for a 10 or 12 W1v3-2 in a sealed enclosure... winISD recommends a sealed enclosure of like 26L. When I increase the sealed volume to 1.5 or even 2.5 cubes, the Q goes up around 0.8-0.9.

How/why is that? Does that higher Q of 0.85, for example, mean the sub will be sloppy? And, it seems like the JL subs work in small enclosures, unless ported.


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## 156546 (Feb 10, 2017)

rxh0272 said:


> Wait a minute. The Qts is total Q of the sub, correct? Qts = Qes * Qms. So, is higher Qts or lower Qts more stiff of a suspension system? Because research indicates Qts < 0.4 = good for vented box.
> 
> So, if I want to get low, and run ported, I need a sub capable of Qts < 0.4 and Fs somewhere around 30 or less, or at least that's how low I want it to go. I have limited space, so challenge is getting the tuning I want within the constraints.


No. The formula for Qts is product over sum, just liek it is for resistors in parallel. Qts = (Qes*Qms)/(Qes+Qms).


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## 156546 (Feb 10, 2017)

rxh0272 said:


> yup! I noticed the typo after the fact.
> So, correct me, if I am wrong: Since fc will always be higher than the fs, for any given driver, when placed into a sealed enclosure. So tuning can be done based off of this, say in winISD, and tuned lower than the fc hoping to get the speaker box system tuned at the goal. So, tune for 25 Hz to get 30Hz. ? But, I'm still confused about whether or not it is safe to tune the system with ported box tuned below the sub's fs because I've read in my research that doing so can cause the sub to blow when trying to play Hz below it's fs and capabilities. Or, at least power handling goes down at such frequencies, and thus blow, unless power is turned down.
> 
> Thank you.
> ...


The sub doesn't blow if you tune it below its Fs. This is why I posted what I posted. There is no Fs when the woofer goes in the box. There's only Fc (in a sealed box) and Fb in a vented box. There is no more Fs.


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## rxh0272 (Jul 26, 2020)

GotFrogs said:


> The sub doesn't blow if you tune it below its Fs. This is why I posted what I posted. There is no Fs when the woofer goes in the box. There's only Fc (in a sealed box) and Fb in a vented box. There is no more Fs.


OK. Well, I can only model them in winISD, since I do not have the equipment to test for real. 
Otherwise, it might end up being one of those cases where I build, then modify/rebuild, etc. But, I would like to prevent that. 
--I see your point about tuning lower to try and get the Hz desired.


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## daloudin (Nov 2, 2020)

rxh0272 said:


> Thank you very muc hfor the feedback. Sorry too. Got laid off and needed new job, and that sucked up my time.
> 
> When using winISD for a 10 or 12 W1v3-2 in a sealed enclosure... winISD recommends a sealed enclosure of like 26L. When I increase the sealed volume to 1.5 or even 2.5 cubes, the Q goes up around 0.8-0.9.
> 
> How/why is that? Does that higher Q of 0.85, for example, mean the sub will be sloppy? And, it seems like the JL subs work in small enclosures, unless ported.


You've misunderstood, misread or had the wrong unit for the recommended.

WinISD recommends 100.9 L or 3.563 cuft Sealed for 12W1v3-D2 for Qtc 0.704
Going *down *from that to 1.5 or 2.5 cuft will raise the Q


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## rxh0272 (Jul 26, 2020)

daloudin said:


> You've misunderstood, misread or had the wrong unit for the recommended.
> 
> WinISD recommends 100.9 L or 3.563 cuft Sealed for 12W1v3-D2 for Qtc 0.704
> Going *down *from that to 1.5 or 2.5 cuft will raise the Q


Oh. OK. I thought it seemed odd.


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## JohnnyOhh (Feb 19, 2015)

Thanks again for all the info in this thread. Based on some of the comments above, I put together a little set-up in my basement and measured a box (Belva 1SV12B from SE) that I had laying around to try to see if I could measure the tuning frequency. It's advertised on SE as 36Hz tune. I found it to be pretty close. It was a fun experience. Now I personally feel like there could be some subjectivity in regards to the labeling the exact tuning frequency.... based on my data set anyway. Is there any way I can improve this? I would say there might be some un-certainty of maybe a ~5 Hz window to choose the specific tuning freq. Maybe it could really be anywhere between 33Hz - 38Hz...? Any thoughts how I could improve? I was thinking maybe use more POWER (2x more)....? or maybe little higher resistance value (2x more)?

So I used a 12V power supply, I used a subwoofer amp, ported box + woofer & I used a 1 ohm power resistor in series between the amplifier & the woofer. I took measurements with an el cheapo scope. I tried the ~500-600 ohm resistor mentioned above, but that did NOT work, I think it was limiting the output current of the amplifier too much..... I think. The 1 ohm worked nice though.

I used a subwoofer amplifier and set the output to around 30W (for me this was around 9.5V pk-pk with my 2 ohm woofer coil + 1 ohm series R) at the output terminals of my amplifier. Then I measured the voltage across the 1 ohm series resistor to get the current - converted this to impedance & plotted the results in Excel. I did the measurements at 1Hz spacing, between 30Hz - 60 Hz.


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## rxh0272 (Jul 26, 2020)

JohnnyOhh said:


> Thanks again for all the info in this thread. Based on some of the comments above, I put together a little set-up in my basement and measured a box (Belva 1SV12B from SE) that I had laying around to try to see if I could measure the tuning frequency. It's advertised on SE as 36Hz tune. I found it to be pretty close. It was a fun experience. Now I personally feel like there could be some subjectivity in regards to the labeling the exact tuning frequency.... based on my data set anyway. Is there any way I can improve this? I would say there might be some un-certainty of maybe a ~5 Hz window to choose the specific tuning freq. Maybe it could really be anywhere between 33Hz - 38Hz...? Any thoughts how I could improve? I was thinking maybe use more POWER (2x more)....? or maybe little higher resistance value (2x more)?
> 
> So I used a 12V power supply, I used a subwoofer amp, ported box + woofer & I used a 1 ohm power resistor in series between the amplifier & the woofer. I took measurements with an el cheapo scope. I tried the ~500-600 ohm resistor mentioned above, but that did NOT work, I think it was limiting the output current of the amplifier too much..... I think. The 1 ohm worked nice though.
> 
> ...


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## JohnnyOhh (Feb 19, 2015)

I added the resistor in series with the woofer to measure the current going to the woofer/box. With the resistor in series, the same current will flow through the resistor as the woofer. You need something to measure current. I suspect this is what many of the tools that do this automatically use.

Then you can measure current via measuring the voltage drop across the resistor and knowing V=I*R therefore I=V/R. So you can measure current at each different frequency since you know V & R.

The voltage would be constant across the woofer in my set-up because I am using an amplifier that holds constant voltage, I set it to around 9.5V. Once you know current flowing through the woofer and the voltage across the woofer, you can calculate the resistance of the woofer. It's really just directly scaled to the current flow... R=V/I -> graph.

I don't _think _the environment should affect any of these measurements to drastically..... I was thinking about that before..... I did not use a mic for any of this.

I think the point here is to really use the woofer as a measurement tool. This is all in the spirit of measuring Box Tuning. So you are using the coil on the woofer in combination with its suspension to measure the pressure pressure in the box at different frequencies. The pressure in the box is related to the current that flows through the voice coil, I gather. Which you can measure.

So that at the box tuning point, the resistance to movement is minimum, and the highest current would flow, with a constant voltage applied to the speaker.


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## Holmz (Jul 12, 2017)

JohnnyOhh said:


> I added the resistor in series with the woofer to measure the current going to the woofer/box. With the resistor in series, the same current will flow through the resistor as the woofer. You need something to measure current. I suspect this is what many of the tools that do this automatically use.
> 
> Then you can measure current via measuring the voltage drop across the resistor and knowing V=I*R therefore I=V/R. So you can measure current at each different frequency since you know V & R.
> 
> ...


You mean *inversely*?





JohnnyOhh said:


> ....
> So that at the box tuning point, the resistance to movement is minimum, and the highest current would flow, with a constant voltage applied to the speaker.


It is good up until the end.
Just flip over the graph to show current.

The high impedence at the tuning freq is because the box has a high resistance to movement there, not a low resistance..


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## JohnnyOhh (Feb 19, 2015)

Ahhh no. Don't think so. If you google search "example box impedance graph" they pretty much all look like this.
I mean I am not calculating impedance exactly, but only resistance.

But I thought the low point on the impedance/resistance graphs indicate the box tuning frequency. That's the low impedance/resistance and also highest current point, with constant voltage applied.


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## JohnnyOhh (Feb 19, 2015)

I think the resistance to movement (of the woofer) would be low at the box tuning frequency because the port is tuned to allow air to pass easily at Fb. So the woofer/suspension/coil would not have to work hard at all, it would be easy to push the air out of the box at Fb.

This does feel counterintuitive though,.... because if the resistance to movement is low, and it is easy to move the speaker, you would _want _to think that the power consumption would be low also. But I think power consumption is high in this case. Maybe that's part of why ported boxes have extra sound output here.

Also, I do mean inversely there, thx! hahaha.



Holmz said:


> You mean *inversely*?


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## Holmz (Jul 12, 2017)

JohnnyOhh said:


> I think the resistance to movement (of the woofer) would be low at the box tuning frequency because the port is tuned to allow air to pass easily at Fb. So the woofer/suspension/coil would not have to work hard at all, it would be easy to push the air out of the box at Fb.
> ...


If the resistance is lowest at port tuning, then the cone must be moving the most distance there?

And then why use a subsonic filter if the resistance is higher below tuning?


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## JohnnyOhh (Feb 19, 2015)

I do not know that. I was wondering the same thing.

Maybe the reason is related to the Fs resonance of the speaker itself?

If the box is tuned around the Fs, playing music/frequencies below box tuning frequency, also means playing music/frequencies below Fs..... is bad for the woofer?


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## Holmz (Jul 12, 2017)

JohnnyOhh said:


> I do not know that. I was wondering the same thing.
> 
> Maybe the reason is related to the Fs resonance of the speaker itself?
> 
> If the box is tuned around the Fs, playing music/frequencies below box tuning frequency, also means playing music/frequencies below Fs..... is bad for the woofer?


It was a rhetorical question... the cone moves the least at the port freq.

When the cones moves easily, like below the port freq, then one can slam the VC into XMAX.

There is the box freq, the port freq, and the subs Fs...
A sub can play below its Fs.


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## LBaudio (Jan 9, 2009)

every SW driver play under its Fs in a Sealed box.....


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