Mixing Low QTS and High QTS subs in the same box

[blazian87 10+ year member]

My mistake in my post I had 4 passives, 2 on the back opposite the subs one one on each side. As I said, you def couldn't tell what speaker was what. The roll-off of a PR setup is steeper below tuning, it's a 5th order rolloff vs a 4th order, but that doesn't really make a difference as you shouldnt' be trying to play much below tuning anyways. I also had an issue ripping passives for a while when, until I switched to the creative sound ones. My theory was the interal space inside by box was too small and somehow the magnets on the subs were causing non linear behavior from the passives, ripping the spider. same passive every time too, trust me I know how you felt lol. Once I finally switched to the creative sounds ones without the weight on the back, they have handled everything I have thrown at them perfectly and they are super to adjust, love them. They don't have the excursion of the TC sounds,but really it's not needed. Run TC passives in a 1:1 ratio and odds are you still need a second one because your excursion will be 50mm or something silly. Once you go up to a 2:1 ratio, excursion drops MUCH lower and you no longer need 45mm, the 34 I have is enough lol. Right now I'm only using 3 passives on a 21 with A LOT of motor force (just a touch weaker than a TC 5200) and they are fine with 1200 watts applied, once I go to 2-3k, I'll need to add another one.
Also, if correctly utitlized a ported or PR box will have better SQ than a sealed box, all things equal. They are lower in distortion, just harder to get correct frequency response, but once you do, they sound great. My subs were pretty low Q and worked very well in a small ported box tuned very low, which is hard to build with a standard port, especially inside a trunk. They exhibited a falling response similar to most good IB setups with a Q of around .5, but had the reduced distortion levels due to being ported.

Anyway a proper port is better than a proper passive in most respects, but proper ports are hard to come by in cars in some cases. Like in my case, to build a box for 2 15's ported tuned where it would sound the best, I'd need around 7 cubic feet internal before port displacements, no way in heck that was fitting in my trunk. I'd either have to use an undersized port, compromise my tuning, or both. Passives don't take up any displacement, so I only needed a 5 cubic foot box with enough surface areas to mount the passives. That's the advantage of a passive, you have no port compression to deal with, vent displacements, port noise, and they are infinitely adjustable. Sure if your in can fit anything, then ports are the better way to go, if you can't, passives can be a ideal solution.

I don't understand how ported and PR have better SQ than sealed? I thought sealed has the most flattest and cleanest sound. I'm not saying it's not gonna sound great in a ported but I think sealed is more accurate. Nonetheless I'm gonna give PR's another try. I just ordered the creative ones. The weights on the outside sounds fun to play with. I still don't know how to find the exact tuning frequency. Like should I add all the weights first and just take one off at a time? Should I try to aim for 28 hz? Hopefully they ship it out soon so I have something to listen to as my sub is running with no passives right now. Once the new subs come in a month or so, I"ll compare them and see which one I like better.

 

[T3mpest 10+ year member]

I don't understand how ported and PR have better SQ than sealed? I thought sealed has the most flattest and cleanest sound. I'm not saying it's not gonna sound great in a ported but I think sealed is more accurate. Nonetheless I'm gonna give PR's another try. I just ordered the creative ones. The weights on the outside sounds fun to play with. I still don't know how to find the exact tuning frequency. Like should I add all the weights first and just take one off at a time? Should I try to aim for 28 hz? Hopefully they ship it out soon so I have something to listen to as my sub is running with no passives right now. Once the new subs come in a month or so, I"ll compare them and see which one I like better.

If you download WINISD Alpha, which is free, it can model passive radiator enclosures. You'll choose PR as your box type, put in the specs for the passives, which can be found in the PDF on creative sounds site where you ordered. Put that all in, then select the PR tab, add weight to the passives until it tunes where you want with the box size you have, it's a very easy program. OR give me your exact enclosure volume, including the sub displacement, and I can do it for you an tell you how much weight for various tunings.

The basic idea is a sealed box rolls off at 12db octave and cabin gain is approx that much gain the other direction, so you should end up with a flat response. However, two issues with that. One cabin gain is NOT that simple. Cabin gain is really 2 or 3 major high Q peaks that average out to that kind of gain, second flat response in a car, sounds like crap. Small environments generally need a 6db gain between 40-20hz in order to sound flat to the human ear. A properly done ported or PR box can sometimes give you that, with some subs anyways. Also, sometimes you can actually design a ported box to end up with a smoother response than sealed, as you can sometimes get the peak at tuning to fill in some of your weaker bass areas. It's mostly about frequency response and level matching for a sub when dealing with SQ. Sometimes it takes a sealed box to get the response you want, sometimes it's ported. If you have an EQ though, you can always fix the response later and ported/PR setups have lowered distortion from the lowered cone excursion near tuning. I always run a DSP in my car, so I dont' have to worry about my basic response as much, that ALWAYS makes ported/PR's a better choice. However, as I said, in my last car, even without EQ, with the sub I ran a small ported box was the way to go for proper response.

Small sealed boxes area an easy way to get decently response of out most subs. Your also literally just choking the **** out of them and letting cabin gain make up for it, not exactly clean effortless bass lol. For a beginner, it's very easy to say SQ=sealed ported=SPL, as if you don't know how to build a box to deal with cabin gain, that's often how it ends up. Once you know how to tailor a subs response to fit your needs better, you end up in a grey area where both designs can work, but ported is superior in distortion characteristics.

Anyway, the 3 FI Q's will certainly be louder than one one will be, but response wise we will have to see which you prefer once you get it setup properly.

 

[blazian87 10+ year member]

If you download WINISD Alpha, which is free, it can model passive radiator enclosures. You'll choose PR as your box type, put in the specs for the passives, which can be found in the PDF on creative sounds site where you ordered. Put that all in, then select the PR tab, add weight to the passives until it tunes where you want with the box size you have, it's a very easy program. OR give me your exact enclosure volume, including the sub displacement, and I can do it for you an tell you how much weight for various tunings.
The basic idea is a sealed box rolls off at 12db octave and cabin gain is approx that much gain the other direction, so you should end up with a flat response. However, two issues with that. One cabin gain is NOT that simple. Cabin gain is really 2 or 3 major high Q peaks that average out to that kind of gain, second flat response in a car, sounds like crap. Small environments generally need a 6db gain between 40-20hz in order to sound flat to the human ear. A properly done ported or PR box can sometimes give you that, with some subs anyways. Also, sometimes you can actually design a ported box to end up with a smoother response than sealed, as you can sometimes get the peak at tuning to fill in some of your weaker bass areas. It's mostly about frequency response and level matching for a sub when dealing with SQ. Sometimes it takes a sealed box to get the response you want, sometimes it's ported. If you have an EQ though, you can always fix the response later and ported/PR setups have lowered distortion from the lowered cone excursion near tuning. I always run a DSP in my car, so I dont' have to worry about my basic response as much, that ALWAYS makes ported/PR's a better choice. However, as I said, in my last car, even without EQ, with the sub I ran a small ported box was the way to go for proper response.

Small sealed boxes area an easy way to get decently response of out most subs. Your also literally just choking the **** out of them and letting cabin gain make up for it, not exactly clean effortless bass lol. For a beginner, it's very easy to say SQ=sealed ported=SPL, as if you don't know how to build a box to deal with cabin gain, that's often how it ends up. Once you know how to tailor a subs response to fit your needs better, you end up in a grey area where both designs can work, but ported is superior in distortion characteristics.

Anyway, the 3 FI Q's will certainly be louder than one one will be, but response wise we will have to see which you prefer once you get it setup properly.

That makes much more sense now. I guess I was thinking too simple to think that one box rules all. I just got a DSP installed in my car like 2 months ago. I still don't know how to mess with EQ settings yet. I left it off for now because I don't know exactly which frequencies to cut. Same for Time Correction. I just figured that I want an equal sound stage from left seat and right seat so I didn't want one seat to sound better than the other. I will try auto-eq when I get the chance to get an idea where to start from but everyone seems to think that auto-eq is horrible, which is why I left it alone. The only thing I've done so far is set the active crossovers and adjust the levels to match. I'm fairly satisfied with how it sounds now but I know I'm missing EQ. Do you know a good RTA program to use to find peaks and such?

 

[T3mpest 10+ year member]

That makes much more sense now. I guess I was thinking too simple to think that one box rules all. I just got a DSP installed in my car like 2 months ago. I still don't know how to mess with EQ settings yet. I left it off for now because I don't know exactly which frequencies to cut. Same for Time Correction. I just figured that I want an equal sound stage from left seat and right seat so I didn't want one seat to sound better than the other. I will try auto-eq when I get the chance to get an idea where to start from but everyone seems to think that auto-eq is horrible, which is why I left it alone. The only thing I've done so far is set the active crossovers and adjust the levels to match. I'm fairly satisfied with how it sounds now but I know I'm missing EQ. Do you know a good RTA program to use to find peaks and such?

You'd need to buy a mic with a calibration file. True RTA is a decent program and I think the demo version is free and will do the basics What EQ are you using, how many bands do you have? If your not using a dual 31 band or anything crazy, it's probably easy enough to tune it by ear, I'll explain how down below.. Best way to do time alignemnt by ear is to play some test tones in the midbass region and delay the closest midbass to you until it sounds centered on the dash. To double check it, if you've time aligned properly, if you disconnect one mid from the amp and reverse it's phase your midbass should now sound VERY bad. Quiet and speaker locations should be immediately obvious, it's because your now almost all the way out of phase. Bandwidth limited pink noise 80-300hz is the best, but IDK where I even found that track lol.

Most smartphones can get RTA programs for free, but IDK if I'd trust it too much. If you only have a few bands of EQ avaialable, easiest way to tune by ear if you have no experience is to use headphones. Download a bunch of tones 100-20k and listen to them in order low to high on headphones that you like the sound of. Pay attention to how much louder each tone is as you go up, take notes as you go. You'll find some notes jump quite a bit in volume vs others, while others stay the same more or less. Write down where the jumps in volume appear to be and which tones are more or less the same SPL, slowly rising, slowly falling Then go to your car and do the same. You'll pretty quickly find your big peaks that aren't supposed to be there and you can cut them down. If I only have say 5-7 bands of EQ I usually do that first (although I've memorized the tone loudness part) and then fine tune using music I know well.

Anyway without using any DSP, your sound in both seats is probably "eh" at best. If you use a DSP, yes it will get better for one seat and worse for the other. However, since right now your already not optimized for the passenger seat, it won't sound too much different from there, while sounding MUCH better from the drivers seat after you EQ and T/A, which is where you sit anyways.

 

[blazian87 10+ year member]

You'd need to buy a mic with a calibration file. True RTA is a decent program and I think the demo version is free and will do the basics What EQ are you using, how many bands do you have? If your not using a dual 31 band or anything crazy, it's probably easy enough to tune it by ear, I'll explain how down below.. Best way to do time alignemnt by ear is to play some test tones in the midbass region and delay the closest midbass to you until it sounds centered on the dash. To double check it, if you've time aligned properly, if you disconnect one mid from the amp and reverse it's phase your midbass should now sound VERY bad. Quiet and speaker locations should be immediately obvious, it's because your now almost all the way out of phase. Bandwidth limited pink noise 80-300hz is the best, but IDK where I even found that track lol.
Most smartphones can get RTA programs for free, but IDK if I'd trust it too much. If you only have a few bands of EQ avaialable, easiest way to tune by ear if you have no experience is to use headphones. Download a bunch of tones 100-20k and listen to them in order low to high on headphones that you like the sound of. Pay attention to how much louder each tone is as you go up, take notes as you go. You'll find some notes jump quite a bit in volume vs others, while others stay the same more or less. Write down where the jumps in volume appear to be and which tones are more or less the same SPL, slowly rising, slowly falling Then go to your car and do the same. You'll pretty quickly find your big peaks that aren't supposed to be there and you can cut them down. If I only have say 5-7 bands of EQ I usually do that first (although I've memorized the tone loudness part) and then fine tune using music I know well.

Anyway without using any DSP, your sound in both seats is probably "eh" at best. If you use a DSP, yes it will get better for one seat and worse for the other. However, since right now your already not optimized for the passenger seat, it won't sound too much different from there, while sounding MUCH better from the drivers seat after you EQ and T/A, which is where you sit anyways.

My DSP comes with 10 bands parametric and 31 bands graphic. I can do L and R channel individually too as it appears. I have to do everything through a program with my laptop so it's a bit annoying and very time consuming. I'll show you a pic of how the layout looks. Seems very intimidating with so many things to control but I also like how they don't limit you on sound tweaking. This processor also includes a mic to use with the auto EQ and everything. I'm not sure if I can use it as a RTA but I will try and see. I haven't used it yet because I don't really know where to mount it. I don't have a tripod stand so maybe I could just put it in between my headrests? I think I might mess up doing it by ear because I'm not very familiar with how to get a good response in the first place. I'm just guessing that I'm supposed to cut the frequencies that are too loud or any unwanted noise. If anything I will invest in a paid RTA program to see things more accurately. What am I missing out on if I use the free demo one? I think I have a CD with different pink noise so I will definitely try that out too.

 

[T3mpest 10+ year member]

If you have that much power at your disposal, I'd pay for a full RTA program at some point. The free version will give you basic rta functions, just no gated measurements and things like that, a good program can do lots of advanced things. You don't need a tripod. You want yourself in the car so that your body is taken into accoutn with the measurement. Best way to do it is to figure out where you head is and lean out of the way or put your seat back so your mic can go where your head is. then swirl the mic in a figure 8 above your head while taking measurements so you end up with an average of where your head is. There is a good article on DIYMA about it. Tuning your car using a pc based measurement setup - Car Audio | DiyMobileAudio.com | Car Stereo Forum

Just a few other tips. Do each speaker and side individually. EQ one speaker first then the other on the same side. Once you have one side totally EQ'ed, then go an EQ the other. The goal is not only to get a fairly flat response, but it's even more important to get a MATCHING response from left to right. So get one side to the curve you want, and when EQ'ing the other side, try to make it mirror the other one, that's more important than flat. Also, while I'm talking about flat response, don't aim for that lol. Aim for a few extra db's in the midbass region 80-250 or so, flat from there and then a gentle roll off once you hit the upper treble region, down around 6db by the time you hit 20k. Sub region usually needs to be flat with the midbass from 80-40 and then a small boost above that,again 3-6db of gain as you approach 20hz.

 

[ancorp 10+ year member]

Seal up one side of the box, put a 6" aero port tuned to 32hz into a 12.5" wood disk to cover the other side, and put the original FI sub into it. Sell it like that. Use money to build the biggest box you can fit into your trunk for the two new FI 12s.

 

[blazian87 10+ year member]

Seal up one side of the box, put a 6" aero port tuned to 32hz into a 12.5" wood disk to cover the other side, and put the original FI sub into it. Sell it like that. Use money to build the biggest box you can fit into your trunk for the two new FI 12s.

Are you saying biggest sealed box or biggest ported box for the 2 Fi Q's? I may not be able to fit dual ported box but for sure a big sealed box.

 

[ancorp 10+ year member]

No im saying use your triple 12 box as one single ported box. Cover both side holes, put a 6 inch aero port in there, and run the old FI sub in it, and sell it.

Then use the money to make a nice dual 12 box for your new subs.

 

[blazian87 10+ year member]

No im saying use your triple 12 box as one single ported box. Cover both side holes, put a 6 inch aero port in there, and run the old FI sub in it, and sell it.Then use the money to make a nice dual 12 box for your new subs.

Yes, I knew what you said. What I'm asking is should I go ported or sealed for the dual 12 box? How big would I have to go to make it sound great? I might not have enough space for an ideal dual ported box. And since these subs are dual 2 ohm, I won't be able to take advantage of the 1 ohm load. Unless I go .5 ohms, which might be harmful to my electrical. Would it sound good in a big dual sealed box with the Low qts subs?

 

[blazian87 10+ year member]

@T3mpest; The Fi Q's came unexpectedly fast so I ended up hooking all 3 up in the same box. It was really loud on the higher range but had practically no low end like you said. Very under dampened.. I wasn't getting the frequency response I wanted and there seemed to be a lot of muffled noise inside the box which I believe was cancellation. It was choking the **** out of my subs basically lol. I then disconnected the middle sub and ran only 2 subs on the side. It definitely sounded a little better and the low end came back alittle but still not ideal. It could be the extra displacement from the middle sub and the fact that it's in a shared chamber. I just barely got the Creative Passives in yesterday so I will try that soon and report back. Oh btw I tried using winisd alpha and had a hard time getting the parameters right especially the Fi Q. I still can't figure out how much weights to put but I'm gonna try putting all the weights on and slowly take off one at a time.

 

[T3mpest 10+ year member]

[quote name='blazian87']@T3mpest; The Fi Q's came unexpectedly fast so I ended up hooking all 3 up in the same box. It was really loud on the higher range but had practically no low end like you said. Very under dampened.. I wasn't getting the frequency response I wanted and there seemed to be a lot of muffled noise inside the box which I believe was cancellation. It was choking the **** out of my subs basically lol. I then disconnected the middle sub and ran only 2 subs on the side. It definitely sounded a little better and the low end came back alittle but still not ideal. It could be the extra displacement from the middle sub and the fact that it's in a shared chamber. I just barely got the Creative Passives in yesterday so I will try that soon and report back. Oh btw I tried using winisd alpha and had a hard time getting the parameters right especially the Fi Q. I still can't figure out how much weights to put but I'm gonna try putting all the weights on and slowly take off one at a time.[/QUOTE]

Just let me model it real quick and I'll tell you.. Super heavy passive isnt' a good idea, that may be why you broke them in the first place. What airspace is your box again? Do you know for sure? If you give me your airspace I should be able to give you a very good idea where to start.

edit: Just modeled. Full weight will add 900 grams and tune you at 25hz. That's not a bad tuning, but I' remove a bit of weight if only to ease the suspension some. 16 of them tunes you around 28 and will give you your peak from tuning right around 30hz. Should be good for music with just a bit of extra bump on the lowend for rap.. Starting with 20 weights isn't too bad in this case, your box size makes that doable. Still I think between 12-16 weights is where you will end up. If you have a SSF, set it at 25hz if you end up in the weight range I said. If you end up with less weight, SSF needs to go to 30. If you do full weight, 20hz should be fine.

 

[ancorp 10+ year member]

What vehicle and what are your maximum dimensions that you can fit in the trunk?

 

[blazian87 10+ year member]

What vehicle and what are your maximum dimensions that you can fit in the trunk?

2004 Toyota Corolla. max i can fit is probably not much bigger from the box I have now. Maybe 34 L x 15 H x 17 W. My trunk space is actually bigger but the shape of my trunk entrance prohibits me to put a big box. It would have to be weirdly shaped to fit or actually build the box inside my trunk which seems like a hassle. I recently put new passives in and I actually like how it sounds now. I decided to put up my extra Fi Q's for sale since I won't be needing it anymore. But hypothetically, how big of a box can I get away with using 2 12" Fi Q's? maybe 1.3 cu ft net each?

 

[blazian87 10+ year member]

Just let me model it real quick and I'll tell you.. Super heavy passive isnt' a good idea, that may be why you broke them in the first place. What airspace is your box again? Do you know for sure? If you give me your airspace I should be able to give you a very good idea where to start.
edit: Just modeled. Full weight will add 900 grams and tune you at 25hz. That's not a bad tuning, but I' remove a bit of weight if only to ease the suspension some. 16 of them tunes you around 28 and will give you your peak from tuning right around 30hz. Should be good for music with just a bit of extra bump on the lowend for rap.. Starting with 20 weights isn't too bad in this case, your box size makes that doable. Still I think between 12-16 weights is where you will end up. If you have a SSF, set it at 25hz if you end up in the weight range I said. If you end up with less weight, SSF needs to go to 30. If you do full weight, 20hz should be fine.

I just recently put it in the Creative passives and they sound great. I'm really diggin it. I still kinda prefer the sound of sealed but this is still a great sound. I put the SSF to 25, then moved it to 28 now. Made it sound so much better. I first started with 16 weights each side. When I play rap songs like young jeezy and ice cube.. mann those things go LOWW.. Tuning was a bit too low for my taste though, sounded a bit too muddy on most higher note songs so I decided to take two weights off and ended up with 14 each side. I really like it now, it's a pretty good compromise and was still able to attain some lows. I wonder what I'm tuned to right now.. I've been messing with my DSP a lot and slowly but surely, it's sounding so much better. Thank you so much for all the help you've given me. I've decided to keep this box and sell off the 2 extra Fi Q's. Wish I had known about this info before.. oh well, you live and you learn. I have a question.. do you think it would benefit me at all to put poly-fill inside my box? Is there any cons to doing it?