Cplkittle i was reading through your article on sealed boxs. You have the formula (0.7/Qts?Fs) = box freq. Is that the freq. that the box is tuned to or the cutoff freq. I just got done skimming through "The Car Stereo Cookbook" and it says to figure out the cutoff freq. in a sealed box you use the formula 0.8(bass response= Fs sqrt of Vas)/sqrtVb(Vb is box volume). So i assume your talking about the freq. the box is tuned to am i correct?
Replies (7)
snipe523 on 09/8/2004 16:57:01
Are you sure this is not referring to a ported box? Sealed boxes have no tuning frequency, as ported boxes do.
ryan on 09/8/2004 21:57:29
Im sure cuz it said box freq. for a sealed box. maybe its the roll off freq. or something.
uochronos on 09/8/2004 22:03:50
i'm not reeal familar with this but any box is going to have a frequency that it well play louder then the rest... for insatnce a larger box well get more low end a smaller one well get more high end.
i'm sure there is a formula for this. and Kittle probaly could tell ya alot more. he is sort of are master of that subject. also swez well probaly be along to help explain this if he doesnt know he can probaly find a link to explain it... seems like he has an endless supply of great links:)
Chronos
swez on 09/9/2004 09:34:09
From my readings and imperical experiments, box size (Vb) has a lot to do with how low a sub will go in frequency and net a reasonable SPL value. 0.707 Qts is most common in audiophile quality speaker designs.
In smaller enclosures Vb will determine the slope rate of the rolloff on low end audio signals a sub can reproduce. Larger boxes produce gentle slopes from 100 Hz, down to ~ 40 Hz. Smaller boxes will net steeper slopes in that range.
Adire Audio has published "White Papers" and tech notes on several of their big seller woofers and there is a Tech section that shows rolloff curves for Adire drivers at different Q values. (0.707, 0.85 & 0.95) The larger the box, the lower the Q and more deep bass w/o adding EQ
http://www.adireaudio.com/
http://www.adireaudio.com/Files/SealedShivaApplications.PDF
Note the rolloff curves at each Q value.
Swez
snipe523 on 09/9/2004 10:32:55
So pretty much what we are talking about are frequency response curves for sealed enclosures? As a general rule of thumb, a larger box will yeild a flatter response curve with less of a roll off in the low end like stated above, A smaller sealed box will have the opposite effect. I think I just repeated what was said above. I have been up for 36 hours I am tired and rambling and need to go to bed, so feel free to ignore this GRIN
swez on 09/9/2004 17:53:39
Whoa... long day but yeah, you have the general plan.
Swez
cplkittle on 09/10/2004 08:38:26
The formula is for the resonant frequency of the box with a particular sub. It is not the cutoff frequency. A sealed box will have a frequency or small range of frequencies in which the box and the sub are 'in harmony'. It is an actual tuning point, but without the dB gain you get in a ported box tuned frequency. Probably difficult to determine by ear alone, but it does have a peak in efficiency and a small volume gain as well as clarity.
Replies (7)
snipe523 on 09/8/2004 16:57:01
Are you sure this is not referring to a ported box? Sealed boxes have no tuning frequency, as ported boxes do.
ryan on 09/8/2004 21:57:29
Im sure cuz it said box freq. for a sealed box. maybe its the roll off freq. or something.
uochronos on 09/8/2004 22:03:50
i'm not reeal familar with this but any box is going to have a frequency that it well play louder then the rest... for insatnce a larger box well get more low end a smaller one well get more high end.
i'm sure there is a formula for this. and Kittle probaly could tell ya alot more. he is sort of are master of that subject. also swez well probaly be along to help explain this if he doesnt know he can probaly find a link to explain it... seems like he has an endless supply of great links:)
Chronos
swez on 09/9/2004 09:34:09
From my readings and imperical experiments, box size (Vb) has a lot to do with how low a sub will go in frequency and net a reasonable SPL value. 0.707 Qts is most common in audiophile quality speaker designs.
In smaller enclosures Vb will determine the slope rate of the rolloff on low end audio signals a sub can reproduce. Larger boxes produce gentle slopes from 100 Hz, down to ~ 40 Hz. Smaller boxes will net steeper slopes in that range.
Adire Audio has published "White Papers" and tech notes on several of their big seller woofers and there is a Tech section that shows rolloff curves for Adire drivers at different Q values. (0.707, 0.85 & 0.95) The larger the box, the lower the Q and more deep bass w/o adding EQ
http://www.adireaudio.com/
http://www.adireaudio.com/Files/SealedShivaApplications.PDF
Note the rolloff curves at each Q value.
Swez
snipe523 on 09/9/2004 10:32:55
So pretty much what we are talking about are frequency response curves for sealed enclosures? As a general rule of thumb, a larger box will yeild a flatter response curve with less of a roll off in the low end like stated above, A smaller sealed box will have the opposite effect. I think I just repeated what was said above. I have been up for 36 hours I am tired and rambling and need to go to bed, so feel free to ignore this GRIN
swez on 09/9/2004 17:53:39
Whoa... long day but yeah, you have the general plan.
Swez
cplkittle on 09/10/2004 08:38:26
The formula is for the resonant frequency of the box with a particular sub. It is not the cutoff frequency. A sealed box will have a frequency or small range of frequencies in which the box and the sub are 'in harmony'. It is an actual tuning point, but without the dB gain you get in a ported box tuned frequency. Probably difficult to determine by ear alone, but it does have a peak in efficiency and a small volume gain as well as clarity.
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