Hello,
I have just started designing subwoofer boxes (i did it before, but with random dimensions, sometimes I was successful, sometimes not so much).
Let`s get to the point...
How do I know when box is too big and will sound boomy? or perhaps when it`s to small and driver will struggle?
Currently I have 15l sealed box for my 10" 125W RMS sub.
It plays to high and after entering T/S and box volume into the program I get the graph that shows exactly what I was expecting (tuned to high) YELLOW LINE.
However I was playing with the box volume until I get it lower RED LINE. Yes I loosed the 3db gain (at around 90hz), but I can deal that. I rather turn the volume higher than listen to this loud 90hz bass and when it realy needs to hit (lower) there is no output at all.
But... the box should be at 100liters to achive this frequency response. Something is telling me that a 10" sub in that big sealed box will sound boomy.
How can I know when box is too big or small. What is warning me of exceeding the right volume?
Or is there any rule in general?
Should I go ported for this driver in order to lower the frequency?
Somewhere I read that round port shoud at at least in diameter 1/3 of the driver, what about square (L) port
And why does the bass response of 15l box YELLOW LINE act like it`s in ported box? I mean 3db boost in short range?
Thank you all for your time and help
I have just started designing subwoofer boxes (i did it before, but with random dimensions, sometimes I was successful, sometimes not so much).
Let`s get to the point...
How do I know when box is too big and will sound boomy? or perhaps when it`s to small and driver will struggle?
Currently I have 15l sealed box for my 10" 125W RMS sub.
It plays to high and after entering T/S and box volume into the program I get the graph that shows exactly what I was expecting (tuned to high) YELLOW LINE.
However I was playing with the box volume until I get it lower RED LINE. Yes I loosed the 3db gain (at around 90hz), but I can deal that. I rather turn the volume higher than listen to this loud 90hz bass and when it realy needs to hit (lower) there is no output at all.
But... the box should be at 100liters to achive this frequency response. Something is telling me that a 10" sub in that big sealed box will sound boomy.
How can I know when box is too big or small. What is warning me of exceeding the right volume?
Or is there any rule in general?
Should I go ported for this driver in order to lower the frequency?
Somewhere I read that round port shoud at at least in diameter 1/3 of the driver, what about square (L) port
And why does the bass response of 15l box YELLOW LINE act like it`s in ported box? I mean 3db boost in short range?
Thank you all for your time and help
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Here's what you need to do.
If you want an opinion about a driver, post a picture or a link.
If you want to understand a simulation, post the parameters you used to get there.
The more information you give without rambling, the better answer you will get.
A sealed box too big will not sound boomy unless it is thin-wall, not braced and has no damping material in it - in which case the boom will be from the enclosure and not the driver. The 90Hz peak you see in the small box is "boom"
The small box is not 'acting like a ported box', it is acting like a sealed woofer in a small box.
To better understand how the ratio of box Vb to speaker Vas changes things, try varying the box size by 10L at a time. The box "stiffens" the cone and raises the resonant frequency. The smaller the box, the higher the frequency and vice versa.
Fc=Fs*sqrt(Vas/Vb+1)
Qtc=Qts*sqrt(Vas/Vb+1)
Vb=Vas/((Qtc/Qts)^2-1)
Qtc cannot be less than Qts
0.5<Qtc<1 for a decent sounding system
Get yourself a book. Maybe the Loudspeaker Design Cookbook?
If you want an opinion about a driver, post a picture or a link.
If you want to understand a simulation, post the parameters you used to get there.
The more information you give without rambling, the better answer you will get.
A sealed box too big will not sound boomy unless it is thin-wall, not braced and has no damping material in it - in which case the boom will be from the enclosure and not the driver. The 90Hz peak you see in the small box is "boom"
The small box is not 'acting like a ported box', it is acting like a sealed woofer in a small box.
To better understand how the ratio of box Vb to speaker Vas changes things, try varying the box size by 10L at a time. The box "stiffens" the cone and raises the resonant frequency. The smaller the box, the higher the frequency and vice versa.
Fc=Fs*sqrt(Vas/Vb+1)
Qtc=Qts*sqrt(Vas/Vb+1)
Vb=Vas/((Qtc/Qts)^2-1)
Qtc cannot be less than Qts
0.5<Qtc<1 for a decent sounding system
Get yourself a book. Maybe the Loudspeaker Design Cookbook?
Hello,
thank you for your help.
I don`t have exact accurate T/S parametres yet. I measured them with 5% tolerance resistor and I`m waiting for 1% tolerance resistor to make more accurate mesurement.
My current measurement is:
Parameter/Value Description
-------------------------------------------------------------------
fs 29,4 Hz free air resonance frequency
Zmax 23,9 Ohm impedance at resonant frequency
Rdc 3,8 Ohm DC-resistance
Qms 3,52 mechanical Q of the speaker
Qel 0,66 electrical Q of the speaker
Qts 0,56 total Q of the speaker
Mmd 50,87 g/1,794 oz mass of driver's cone
Cms 0,57 mm/N compliance of driver's suspension
Vas 97,83 l/3,455 ft³ compliance volume of the speaker
I would also like to use this opportunity to ask if Rdc is the same thing as Re?
And if Qel is the same thing as Qes?
Driver is a cheap one from Mac Audio Ice Block 125 (bandpass box) but it will do for now. The whole point is that I want to get some experience in designing encolures and I will be more pleased to get good performance out of cheap driver because of the design than good performance from 200$ driver (like JBL GTO 15" 1500w that shakes the whole car with a box that my friend made without any use of T/S at all)
Qtc was automaticly calculated by a program (BassBox 6 Pro) and it is 0,683, so this is good.
I had noticed that when I swich from closed to vented box Qtc disappears and Fb appears. Does that mean that there is no Qtc for vented enclosure and all I have to look for is Fb (box tunning frequency)?
I will find a book to study whole thing.
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no qtc for ported, just a tuning frequency. a ported enclosure for this driver gets huge, but like anything, one can pick their compromises.
take a look at a 42L sealed box compared to the 100L enclosure you came up with... see if a box with less than half the size is worth the box differential.
also take a look at a 56L enclosure tuned to 20 or 25hz.
given the high Q figures of the driver, a transmission line enclosure is a very viable option.
take a look at a 42L sealed box compared to the 100L enclosure you came up with... see if a box with less than half the size is worth the box differential.
also take a look at a 56L enclosure tuned to 20 or 25hz.
given the high Q figures of the driver, a transmission line enclosure is a very viable option.
With Qts of 0.56 it is a sealed box woofer, I'd probably go for a Qtc closer to 1 if you are trying to impress in a car sub setup. Maybe 30-40 liters.
The 1% resistor may not make as much difference as you think, just measuring teh resistor's actual value is usually good enough.
Qel and Rdc are nonstandard terms
A sealed box only has volume or Qtc as a parameter (one defines the other)
A vented box has Volume and Fb as parameters. There is no such thing as Qtc for vented. Drivers with Qts>0.5 or so ar not very suitable for vented, but they do work for bandpass.
Bassbox is nothing special, I'm guessing you downloaded a pirate copy like so many others, thinking it was useful, eh?
The 1% resistor may not make as much difference as you think, just measuring teh resistor's actual value is usually good enough.
Qel and Rdc are nonstandard terms
A sealed box only has volume or Qtc as a parameter (one defines the other)
A vented box has Volume and Fb as parameters. There is no such thing as Qtc for vented. Drivers with Qts>0.5 or so ar not very suitable for vented, but they do work for bandpass.
Bassbox is nothing special, I'm guessing you downloaded a pirate copy like so many others, thinking it was useful, eh?
There is a large range of permissible sizes for a sealed box. Ideally a Q between 0.5 and 0.707 is ideal, but one needs to remember that damping can make the box appear larger. Also bass in room is dominated by the room. If one adds EQ to deal with this then that can also be used to make a too small a box look larger. Also a smaller box is easier to get to be non-resonant — ie all potential resonances above the bandpass of the woofer.
In the end you have to choose which compromises are best for you.
dave
In the end you have to choose which compromises are best for you.
dave
Hello,
thank you all for opinions.
I have started reading a Loudspeaker Design Cookbook as Ron E advised to me. I had just finished with sealed box chapter.
I had learned alot of things from it.
I didnt even red the vented box chapter yet and I already know that this is sealed box woofer with its low fs, 0,56qts and heavy cone.
I think that I will use 30l sealed box with it`s Qtc at 0,95 and F3 at 49hz.
Thank you again
thank you all for opinions.
I have started reading a Loudspeaker Design Cookbook as Ron E advised to me. I had just finished with sealed box chapter.
I had learned alot of things from it.
I didnt even red the vented box chapter yet and I already know that this is sealed box woofer with its low fs, 0,56qts and heavy cone.
I think that I will use 30l sealed box with it`s Qtc at 0,95 and F3 at 49hz.
Thank you again
Hi diy1995,
A 30 L Sealed Box (No Damping) will return, a Qtc of ~1.1473,fc=~60.7 Hz and a f-3dB of ~45.3 Hz that IMO must be EQ'd if placed near a Wall.
I expanded(Checked) your T/S data and tested QW Designs that allow total Q's above 0.5:
b
PS:If xmax is less than about 5 mm and if Le has a large value, I would too make a Sealed Box but closer to 100L.
Attachments
Hello,Hi diy1995,
A 30 L Sealed Box (No Damping) will return, a Qtc of ~1.1473,fc=~60.7 Hz and a f-3dB of ~45.3 Hz that IMO must be EQ'd if placed near a Wall.
I expanded(Checked) your T/S data and tested QW Designs that allow total Q's above 0.5:
b
PS:If xmax is less than about 5 mm and if Le has a large value, I would too make a Sealed Box but closer to 100L.
thank you for your help.
I`m confused right now.
Had you ever used BassBox 6 Pro? Can you say if this program calculates incorrectly?
This is what I get in BassBox 6 Pro.
However after some thinking I decided to go with bigger box (50l according to my calculations) for more flat response and Qtc closer to 0.707:
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Hi diy1995,
A 30 L Sealed Box (No Damping) will return, a Qtc of ~1.1473,fc=~60.7 Hz and a f-3dB of ~45.3 Hz that IMO must be EQ'd if placed near a Wall.
I expanded(Checked) your T/S data and tested QW Designs that allow total Q's above 0.5:
b
PS:If xmax is less than about 5 mm and if Le has a large value, I would too make a Sealed Box but closer to 100L.
Hi Bjorno where did you get those equations in the images? is it in the software itself?
Members that are known to have died have "R.I.P." (Rest In Peace) under their name.
Unfortunately, Bjorno died September of 2020.
About Bjorno...
He, and his helpful insights are missed.
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