Wierd subwoofer box calculations

[ohsigmachi]

OK, so I've been browsing for quite a while now, trying to find a good compromise between the funds and the sound. I listen to everything from Outkast to Bach to Clutch (pro-rock.com), and everything in between so I wanted a versatile sub. I'm not going to drop a name brand just so no ones biased. I'm going to build my own sealed box for this sub, but when running the numbers on several online calculators I came up with ridiculously low volume values...why is this? Ok, so for you audio gurus here are the speakers vital signs.

This is a 10in sub. I got a Qtc of .7048 with a sealed box volume of only .25 ft^3!! wow!

1500 watts RMS
*VCdia: 3"
*Impedance: 2 ohms per coil
*Re: 4.6 ohms (series)
*Fs: 28 Hz
*SPL: 81.7 dB 1W/1m
*Magnet weight: 195 oz
*CMS: 118 uM/N
*Mms: 270 g
*BL: 23.0 Tm
*Sd: 0.032 sq. m
*Vas: .61 cu. ft.
*Qts: .38
*Xmax: 28 mm

 

[CarpePoon]

OK, so I've been browsing for quite a while now, trying to find a good compromise between the funds and the sound. I listen to everything from Outkast to Bach to Clutch (pro-rock.com), and everything in between so I wanted a versatile sub. I'm not going to drop a name brand just so no ones biased. I'm going to build my own sealed box for this sub, but when running the numbers on several online calculators I came up with ridiculously low volume values...why is this? Ok, so for you audio gurus here are the speakers vital signs.

This is a 10in sub. I got a Qtc of .7048 with a sealed box volume of only .25 ft^3!! wow!

1500 watts RMS
*VCdia: 3"
*Impedance: 2 ohms per coil
*Re: 4.6 ohms (series)
*Fs: 28 Hz
*SPL: 81.7 dB 1W/1m
*Magnet weight: 195 oz
*CMS: 118 uM/N
*Mms: 270 g
*BL: 23.0 Tm
*Sd: 0.032 sq. m
*Vas: .61 cu. ft.
*Qts: .38
*Xmax: 28 mm

Sounds like somebody else got the partsexpress sales flyer
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=293-612

 

[ohsigmachi]

Sounds like somebody else got the partsexpress sales flyer
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=293-612

Uhh yes, I've been eyeing these subs for a looong time, but they were always too pricey for me, but I found a good deal locally on a 1000 watt RMS, 2 ohm stable amp so I figured why not... now what kind of box to put this thing in. All the sub enclosure calculators I've used spit out very small sealed enclosure volumes and I don't want to build it to that spec and get crappy sound. Should I try a vented/ported enclosure?

What Qtc should I try for with this sub? .7 or should I try a lower value?

 

[CarpePoon]

Uhh yes, I've been eyeing these subs for a looong time, but they were always too pricey for me, but I found a good deal locally on a 1000 watt RMS, 2 ohm stable amp so I figured why not... now what kind of box to put this thing in. All the sub enclosure calculators I've used spit out very small sealed enclosure volumes and I don't want to build it to that spec and get crappy sound. Should I try a vented/ported enclosure?

What Qtc should I try for with this sub? .7 or should I try a lower value?

There is no perfect Qtc, Qtc is more just a byproduct of the size box you choose. Its the pressure on the back surface of the sub. You can look at it both ways, get the Qtc from the box volume, or box volume from the Qtc. More airspace = lower Qtc. The whole reason you are getting such small enclosures is because of the high Qtc you are using. typically anything from .4 to 1.2 should give good results. .7 will give you more of a flat response.
What you should look for is what frequency are you trying to tune to? Because frequency should be your base and the other #'s will be calculated off of that. With a Qtc that high (due to the small box) you are going to get a higher resonant frequency.
For a 10" SPL system optimum resonant frequency is usually around 50hz give or take depending on the vehicle. (I have no idea what the best frequency is for a contour, maybe Soundq can jump in and lend some knowledge.) But with going for the box volume you have chosen you get a frequency of 51.93hz so you are getting the typical desired results for SPL, so the programs arent deceiving you. I usually tune for the mid 40's due to personal sound quality preference and since 12's are my sub size of choice. I just feel that 50hz is a bit too high for my preference and my SQ setup is more than loud enough for me. You could step up to a .4cu ft box to tune for 45hz.

 

[SoundQ SVT]

for a sealed box... "tuning frequency" is not a concern. that is a concept reserved for bass-reflex type enclosures, which a simple ported box is one example of.

For a sealed enclosure, the best measure of frequency response performance is the combination of Qtc and the -3db frequency. If my memory serves correctly from long, long ago, the Qtc of .7 and a -3db frequency between 30 and 40 Hz should give a good flat in-car response once cabin gain is added.

 

[elraido]

for a sealed box... "tuning frequency" is not a concern. that is a concept reserved for bass-reflex type enclosures, which a simple ported box is one example of.

For a sealed enclosure, the best measure of frequency response performance is the combination of Qtc and the -3db frequency. If my memory serves correctly from long, long ago, the Qtc of .7 and a -3db frequency between 30 and 40 Hz should give a good flat in-car response once cabin gain is added.

What he said.....