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Villainstone
08-20-2013, 01:22 PM
So I read a very good write up about quality built sealed SQ enclosures. I have always been a vented kinda guy but that article really makes me want to build a sealed SQ box. I have a PPI BK1300w and a 12" GCON in a vented box.I drive a 2003 Tiburon GT I messed up building it and made my port cross sectional area to small so I want to build another box. But I am not sure if I want to build it as a sealed or ported enclosre. Maybe someone can help me make an informative decision.

T3mpest
08-20-2013, 01:26 PM
Link to very good writeup? Then I'll go ahead and give my thoughts.

Villainstone
08-20-2013, 01:32 PM
Designing an SQ Subwoofer Box - The Xtreme Revolution (http://xtremerevolution.net/designing-subwoofer-box-sound-quality/)

That would be the one

T3mpest
08-20-2013, 11:26 PM
Designing an SQ Subwoofer Box - The Xtreme Revolution (http://xtremerevolution.net/designing-subwoofer-box-sound-quality/)

That would be the one

Lots of BS, with some elements of truth.. Here's the truth, whether you want to believe it or not, lol.

1.Group Delay is very misunderstood. It's the rate of change of phase of a driver. Interestingly enough, this also means we get group delay any time we employ a high pass or low pass filter. While that's audible, we hardly call it distortion and no one in car audio uses 6db/octave crossovers to minimize group delay do they? In a car, actually higher slopes tend to work the best. As you go lower in frequency hearing the group delays effect becomes harder and harder as the tones wave becomes longer and your ears are ALOT less sensative. Decent rule of thumb, multiply your group delay in ms by the frequency in question, if your number is less than 400, it should be of no issue. For a box in a car, it's basically the last thing you worry about and any box tuned low, will push the group delay down low.

2.Stuffing a subwoofer enclosure has NO effect on higher order harmonics, few points to consider. For a stuffing material aborb anything, it needs to be AT LEAST 1/4 as thick as one wavelength of the tone in question. 80hz as an example wavelength equals speed of sound/frequency, that's 343m/s over 80, so 4.3meters, give or take a bit. Multiply that times 3.2, to get feet, the wavelength is around 14ft.. Divide that by 4 and we find we need 3.5 feet of stuffing... Even going as high as 200hz, which would be the second order distortion of 100hz, we need around over 1.25ft of stuffing.. Good luck fitting THAT into your box, the only frequencies you'll absorb in very high midrange, 6th and 7th and 8th order distortion that is ungodly low level to begin with.. USELESS. Let's not also forget, we did nothing about the front side of the cone making the same distortion, that doesn't have to vibrate through the cone to reach us. What stuffing can do, is lower the overall q of the enclosure, which may make is sound flatter, bringing me to point number 3.

3. Frequency response is pretty much what you want for a SQ sub in a car, along with proper phase response at the crossover point. If you match phase with the mids, have good frequency response and are level matched, your sub should sound good, assuming nothing in the car rattles, that is a killer. Good frequency response for a sub should be level from the where the mids take over down to around 40hz. From 40hz and down you want a gentle slope of gaining SPL. The smaller the car, the more gain you want below 40hz. Big cabins, 6-8db of gain between 40 and 20 is good, for a small vehicle, 8-12db tends to work well.

4. Excursion issues and inductance issues are true SQ killers. The main type of distortion in most subs, up to 70% is BL related. This is when the motor force of a sub drops as the coil leaves the gap. Losing BL raises the speakers overall q, which changes your frequency response as the sub moves in and out. Tends to make things sound peakier as things get louder. Inductance works similarly, but with frequency. As frequency rises all coils become inductors, if it happens at the frequency in question as you go up, the impedence of the speaker will rise at that frequency, causing less output, so gain, no linear output, again, changing as the coil moves in and out. Subs with shorting rings or copper sleeves can control inductance modulation, subs with a special motor topology like XBL^2 or LMS or even the dual gap system JBL uses all help BL modulation. Now, if we dont' have a fancy motor tech, there is one other way to help keep BL even...

5. Vented boxes help keep the coil centered, so the speaker will have less total THD at any given output level. Near tuning excursion drops, keeping thing linear in a distortion standpoint in the lower octaves. Now if the box is peaky, it may hurt the even more important Frequency response... Thankfully that can be corrected if needed with an EQ, which, honestly, any half *** SQ system should be using given we are in a vehicle. So any box that can give you a curve close to what I mentioned earlier is good, but vented box can do it with less distortion overall.

Lastly, if you can find a sub with low q and low fs, they tend to model very well in small vented boxes, I've never messed with a GCON and dont' have any modeling on this computer. However, I know the DCON fits this description perfectly and is truly at it's best SQ in most vehicles ported, tuned low, between 25-30. My old Acoustic Elegance AV15's did it too, PLUS copper poles, sickening for SQ, IMO. Looking at the GCON, it looks like a moderately large sealed box would work well for good frequency response right out of the box. Ported, I can't estimate without some modeling software, but I'd assume mid sized box ported would be acceptable, especially with a bit of EQ.

Anyway just food for though. If you want full on SQ, moderate sealed, if you want the best of both worlds, go ported tuned low and use an EQ as needed , you can always disable it to boom.

Buck
08-20-2013, 11:40 PM
Depends on what kind of music you listen to.

Villainstone
08-21-2013, 06:13 PM
Awesome!! Ty for clearing that up :)


Lots of BS, with some elements of truth.. Here's the truth, whether you want to believe it or not, lol.

1.Group Delay is very misunderstood. It's the rate of change of phase of a driver. Interestingly enough, this also means we get group delay any time we employ a high pass or low pass filter. While that's audible, we hardly call it distortion and no one in car audio uses 6db/octave crossovers to minimize group delay do they? In a car, actually higher slopes tend to work the best. As you go lower in frequency hearing the group delays effect becomes harder and harder as the tones wave becomes longer and your ears are ALOT less sensative. Decent rule of thumb, multiply your group delay in ms by the frequency in question, if your number is less than 400, it should be of no issue. For a box in a car, it's basically the last thing you worry about and any box tuned low, will push the group delay down low.

2.Stuffing a subwoofer enclosure has NO effect on higher order harmonics, few points to consider. For a stuffing material aborb anything, it needs to be AT LEAST 1/4 as thick as one wavelength of the tone in question. 80hz as an example wavelength equals speed of sound/frequency, that's 343m/s over 80, so 4.3meters, give or take a bit. Multiply that times 3.2, to get feet, the wavelength is around 14ft.. Divide that by 4 and we find we need 3.5 feet of stuffing... Even going as high as 200hz, which would be the second order distortion of 100hz, we need around over 1.25ft of stuffing.. Good luck fitting THAT into your box, the only frequencies you'll absorb in very high midrange, 6th and 7th and 8th order distortion that is ungodly low level to begin with.. USELESS. Let's not also forget, we did nothing about the front side of the cone making the same distortion, that doesn't have to vibrate through the cone to reach us. What stuffing can do, is lower the overall q of the enclosure, which may make is sound flatter, bringing me to point number 3.

3. Frequency response is pretty much what you want for a SQ sub in a car, along with proper phase response at the crossover point. If you match phase with the mids, have good frequency response and are level matched, your sub should sound good, assuming nothing in the car rattles, that is a killer. Good frequency response for a sub should be level from the where the mids take over down to around 40hz. From 40hz and down you want a gentle slope of gaining SPL. The smaller the car, the more gain you want below 40hz. Big cabins, 6-8db of gain between 40 and 20 is good, for a small vehicle, 8-12db tends to work well.

4. Excursion issues and inductance issues are true SQ killers. The main type of distortion in most subs, up to 70% is BL related. This is when the motor force of a sub drops as the coil leaves the gap. Losing BL raises the speakers overall q, which changes your frequency response as the sub moves in and out. Tends to make things sound peakier as things get louder. Inductance works similarly, but with frequency. As frequency rises all coils become inductors, if it happens at the frequency in question as you go up, the impedence of the speaker will rise at that frequency, causing less output, so gain, no linear output, again, changing as the coil moves in and out. Subs with shorting rings or copper sleeves can control inductance modulation, subs with a special motor topology like XBL^2 or LMS or even the dual gap system JBL uses all help BL modulation. Now, if we dont' have a fancy motor tech, there is one other way to help keep BL even...

5. Vented boxes help keep the coil centered, so the speaker will have less total THD at any given output level. Near tuning excursion drops, keeping thing linear in a distortion standpoint in the lower octaves. Now if the box is peaky, it may hurt the even more important Frequency response... Thankfully that can be corrected if needed with an EQ, which, honestly, any half *** SQ system should be using given we are in a vehicle. So any box that can give you a curve close to what I mentioned earlier is good, but vented box can do it with less distortion overall.

Lastly, if you can find a sub with low q and low fs, they tend to model very well in small vented boxes, I've never messed with a GCON and dont' have any modeling on this computer. However, I know the DCON fits this description perfectly and is truly at it's best SQ in most vehicles ported, tuned low, between 25-30. My old Acoustic Elegance AV15's did it too, PLUS copper poles, sickening for SQ, IMO. Looking at the GCON, it looks like a moderately large sealed box would work well for good frequency response right out of the box. Ported, I can't estimate without some modeling software, but I'd assume mid sized box ported would be acceptable, especially with a bit of EQ.

Anyway just food for though. If you want full on SQ, moderate sealed, if you want the best of both worlds, go ported tuned low and use an EQ as needed , you can always disable it to boom.