Mixing Low QTS and High QTS subs in the same box

[T3mpest 10+ year member]

really no 1:1 ratio..... I thort that's what they were built for lol

You clearly know nothing about passive radiators (no offense). Passives radiators are generally ran in a 2:1 ratio. A passive is just like a port, it does most of the work around tuning and is VERY effecient at tuning. So a speaker moving 15mm when it plays a note near the tuning of the passive can move that passive 30mm or more. In order to not break the suspensions on them you run around 2x the cone area of the active speaker in passives. Generally by doing more passives, sometimes simpy a bigger passive like a pair of 10inch subs and 2 12inch passives would generally work.

Anyway the provide the same frequency response as a port, but without the chuffing or port compression effects. Also the tuning can be adjusted so you don't have to build several boxes to get the correct low end response, simply add or subtract weight. To combine both effects, as a single benefit, if you want to do a low tuned box with lots of port area, you can achieve that without giving up a bunch of room for a port. So if you did a 8 cubic foot box at 28hz for 2 15's, you'd normally need a 10-12 cube box by the time you factor in the port, with passives it would just need to be 8 cubic feet.

As far as that box goes, i can't imagine it is big enough for 3 subs sealed. It was only built for 1 12 ported airspace, so that isnt likely to be enough for 3 sealed subwoofers, generally ported boxes are maybe 1.5-2x the airspace of a sealed box, not 3x.

 

[Side Show 10+ year member]

yeah sorry man, i no absolutely nothing about PR, thanks for schooling me tho.

 

[blazian87 10+ year member]

okay so I contacted Fi tech support and they said that the sub can't be converted to high qts. It's already been machined. He also said "Odds of you hearing the difference in the room blindfolded without knowing to begin with would be slim to none honestly." Does anyone know how it would sound different if I went all 3 high qts compared to without it? Would it just sound more smoother with high qts or something? does lower qts hit the lows better because of more motor force?

 

[winkychevelle 10+ year member]

The high qts is a softer suspension setup than the low qts

 

[blazian87 10+ year member]

@T3mpest; I know the box may be small for 3 subs but I looked on the Fi website and it says .8 - 1.5 cu ft recommended for sealed. So technically if I divide my 2.5 cu ft box into 3, that would equal to .8 exactly. It might not be ideal but it might possibly work with enough power going to them. What do you think?

 

[winkychevelle 10+ year member]

[quote name='blazian87']@T3mpest; I know the box may be small for 3 subs but I looked on the Fi website and it says .8 - 1.5 cu ft recommended for sealed. So technically if I divide my 2.5 cu ft box into 3, that would equal to .8 exactly. It might not be ideal but it might possibly work with enough power going to them. What do you think?[/QUOTE]

Low end is gonna suffer but they will hold a little more power. The low qts sub isnt goint to excurt as much which may damage it but hey its your money to blow

 

[T3mpest 10+ year member]

[quote name='blazian87']@T3mpest; I know the box may be small for 3 subs but I looked on the Fi website and it says .8 - 1.5 cu ft recommended for sealed. So technically if I divide my 2.5 cu ft box into 3, that would equal to .8 exactly. It might not be ideal but it might possibly work with enough power going to them. What do you think?[/QUOTE]

One thing to remember is while small boxes "handle more power" they do so by reducing excursion, which is really just a nice way of saying they have less low end output, which is caused by the reduced excursion. Sure you can sometimes get more output at higher frequencies this way, but output down low is still all about excursion. While you can still get the low end back by adding more power (assuming the coil can take it) you won't get the same overall response as the large box as your upper bass frequencies will be louder than the would have been in the larger box. So you don't get the same frequency response. Generally speaking, I like my sealed boxes a hair on the larger side as will most people. That's why most people like low tuned ported boxes too, you get extra output down low with the same output up top. Also don't forget these Q's have some decent sized motors, did you include that displacement when you said it was .8 per sub?

I'm mostly point this out because 1 12 in 2.5 cubes ported which was your original setup will sound nothing like 3 12's sealed in .8 a piece. However you said you didn't like your single 12.. What was your original tuning and what didn't you like? If you can explain that maybe I can advise you on a different setup or how to piece what you have together.

Lastly you will NOT damage your sub by mixing them. You'll end up with a slightly different frequency response than you normally would since the lower Q sub won't have the same roll off as the higher Q models. In the end, it's a mix of all three subs that you hear anyways, so not as big a deal as you'd expect to be honest. Low Q and high isn't that big of a deal. Mostly effects the box size you need for a good response. IMHO, lower Q subs do tend to sound a little smoother and have less of an issue being in a small box as the overall Q of the system doesn't jump up too high. High Q subs are best used in large sealed boxes or IB where you can bring the Q down a hair as a small box tends to make them sound peaky.

 

[blazian87 10+ year member]

Interesting... yea so my box size is 28 x 15 x 15. That would be around 3.6 cu ft but after displacement it's around 2.5 ish I think. I was trying to figure out what I was tuned to. I didn't know the exact method to find out so I used a Tone Generator on my phone. I just put on the passives without any weights. I moved it around 34-35hz and that's where it was moving the least. When I moved up or down from it, the sub moved more. So I'm assuming that it's right where it should be. Maybe I should have tried tuning down to 28 but my passive blew before I could even do that. When I heard it while it was working, the Fi Q sounded great. It was smooth and delightful. Definitely the type of sound I was looking for. But then the moment it hit the lows, the TC passives would react and it just sounded horrible. It didn't match the sound of the Fi. On certain notes, it was very loud while other notes, I barely even heard it. I listen to a wide range of music but even then I tried to listen to a lot of rap and hip hop with low notes. It just sounded weird. And plus my active sub was facing the rear, reflecting the sound deadening I have on my trunk lid while the passives were just floating in the air barely audible. One other thing I noticed was the steep cut off slope. I listened to songs I was familiar with that went very low and sometimes some notes would be missing. I personally don't like the sound of ported as they get muddy pretty easily and some music will sound better than others.

Before this setup I ran 2 12" Diamond D6's in a small prefab sealed box. It sounded way louder than this Fi Q and PR setup and hit every note better. It could have been for various reasons why. Maybe because these diamonds are well broken in while the new setup is way too stiff. Or maybe there was a cone advantage of running 2 12's instead of 1. The Diamonds are rated at 600 rms so I was well overpowering it with my AQ2200. I set my gains with a DD-1 so I wasn't clipping. I used to run a 12" TC9 sub in a custom ported box 2.5 cu ft back in the day so I know what ported boxes are capable of.

Now that I've come to this point. I'm confused more than ever on what to do. Ultimately I'm looking for the best possible SQ I can get while having decent output that can be heard with my front stage. I have Rainbow Germaniums running fully active on an Alpine PXA-h800 processor. I thought I had everything figured out but I always seem to miss little details that mess up everything for me. Maybe I should tell Fi support to change my order to low QTS instead. I'm completely lost. I have no idea how it'll sound. I'm just going with however the boat floats really.

 

[winkychevelle 10+ year member]

Just run the 2 same q s in a sealed box and call it a day. Hell seal up one of the holes in you box and throw em in that box but be careful with the power.

sell the ported version should easily cover the cost of a new box.

another thing the tc vmps are hit and misd quality wise. I dont know why but I have run them with 1 to 1 ratio and they have held but I did a pair of 8s and 2 12inch passives and the passives had failed.

overall psi makes better passive just with less excursion so a 1:1 ratio is almost impossible

 

[Side Show 10+ year member]

dam I wanna hear a PR setup now, got me all intreaged now

 

[blazian87 10+ year member]

I was considering PSI passives actually but I knew the TC are supposed to be high excursion so that's why I picked that. I went on the PSI website and tried to buy passives but for some reason the website wasn't working correctly and said that it doesn't ship to my location. I tried emailing them like over a week ago and they didn't reply back until yesterday. I'm kinda skeptical about it so that's why I had the idea of making my box sealed.

How did you like the sound of the PR's before it failed? Did you like it? Did it hit the lows accurately?

 

[blazian87 10+ year member]

oh yea and if I were to run 2 subs dual 2 ohm, then I would be at 2 ohms final which would be around 1500W. I would need to change the subs to dual 1 ohms to take advantage of the full 2200w. If I run 3 subs 2 ohm, my final impedance would be 1.34 ohms which should be more than 2000w. That's why 3 subs sounds more appealing...

 

[T3mpest 10+ year member]

Sounds like you mostly had user error to blame. I'm guessing you didn't have a subsonic filter either. When I get home today I will model those passives to let you know where you were tuned, but odds are it was higher than you think, hence the missing notes and overexcursion. If you half way liked your sound, I think passives are probably still the way to go, but you need to do it right lol. Creative sounds sells passive radiators, google them. They are less than 1/2 the price of the TC sounds, offer most of the excursion capabilities (regardless you still need 2 and wont' bottom them if run properly) and you can change tuning by adding weight to the FRONT of the cone, so you don't have to remove anything from the box, simply unscrew the dustcap, screw down weight and done.

If you don't like it your out very little money compared to buying 2 more subs, but I honestly think you will like it. Passive setups are great, trust me it was high tuning, you didn't like your box tuned at 40hz lol, that was the issue. My last setup was 2 15's and 2 15's PR's. If done properly, you have no idea when a passive is making the music vs the active sub. I had strong and flat output from 25hz up to 125hz with my subs, tuned at 28hz after I found the sweet spot. Only needed a 4db cut right at 40hz where my car peaks for audibly flat reponse from 25-125. Also removed the weight and did a 147.x out of the trunk at 40hz when I removed most of the weights to tune at 38 for fun lol.

 

[blazian87 10+ year member]

[quote name='T3mpest']Sounds like you mostly had user error to blame. I'm guessing you didn't have a subsonic filter either. When I get home today I will model those passives to let you know where you were tuned, but odds are it was higher than you think, hence the missing notes and overexcursion. If you half way liked your sound, I think passives are probably still the way to go, but you need to do it right lol. Creative sounds sells passive radiators, google them. They are less than 1/2 the price of the TC sounds, offer most of the excursion capabilities (regardless you still need 2 and wont' bottom them if run properly) and you can change tuning by adding weight to the FRONT of the cone, so you don't have to remove anything from the box, simply unscrew the dustcap, screw down weight and done.

If you don't like it your out very little money compared to buying 2 more subs, but I honestly think you will like it. Passive setups are great, trust me it was high tuning, you didn't like your box tuned at 40hz lol, that was the issue. My last setup was 2 15's and 2 15's PR's. If done properly, you have no idea when a passive is making the music vs the active sub. I had strong and flat output from 25hz up to 125hz with my subs, tuned at 28hz after I found the sweet spot. Only needed a 4db cut right at 40hz where my car peaks for audibly flat reponse from 25-125. Also removed the weight and did a 147.x out of the trunk at 40hz when I removed most of the weights to tune at 38 for fun lol.[/QUOTE]

Thanks @T3mpest; I appreciate your input. Actually I did use a subsonic filter. I tried it at 20 hz, 22 hz, and 25 hz.. Couldn't really tell too much of a difference but left it at 22. From what I know, the Tc passives are quite heavy even without weights so I believe it was already tuned low but I could be wrong. I researched every passive radiator there is and I just went with the ones that I thought had the best quality in materials and highest excursion. I have heard of the creative passives but was turned away because I didn't know if it would be able to handle excessive power. The person who built the box for me (known as Dave the Box guy) told me that he built the box on the bigger side so that I wouldn't need to put much weights on, if any. What 15" subs and what PR's did you use? I thought it's not good to use 1:1 ratio as they'll blow no? Even if I were to tune lower, I would think I can still distinguish between the sub and PR because the sub is reflecting directly off the sound deadening material whereas the PR's are dissipating. Maybe if all 3 were facing the rear, it will probably be louder and more equal in sound levels. They had their own unique sound and they just didn't match sonically. I mean after one of my passives blew, I could have technically glued it back together but I've had enough of it. Maybe I may never know how it could've sounded but that's a choice I'm willing to live with. I have read several articles about passive radiators saying that they have a much steeper roll than usual. Even more than ported boxes. I'm starting to think ported boxes are superior to passives if built correctly. Honestly I've always liked the sound of sealed the most. I just wish I had known about the characteristics of a PR setup beforehand. I had the impression that it was actually a sealed box but louder, just not quite as loud as ported. I found out later on that it was actually considered ported which kinda made me regret my buy as I'm looking for pure SQ. Besides everyone's taste is different. What might sound good to someone, might not sound good to someone else.

I already purchased the 2 extra Fi Q's and told them to change the order to Standard QTS instead. I will give it a try once I get em'. I don't imagine it being that bad. I might end up getting a 3500w amp in the future to juice the subs to their potential. I'm having a hard time figuring out what my internal volume will be after putting 3 Fi Q's in. I'm thinking it might be more than 2.5 cu ft or it could be just about 2.5. Dave is the one who told me it's around 2.5 after displacement but I don't even think he knew the exact number. My total volume is 3.64 cu ft with all 3 being flush mounted 1.5 inch baffles all around. I'm trying to use a speaker displacement calculator right now and it might possibly be around 2.95 cu ft internal.

I've already spent well over $10,000 on my system alone, not including the stuff I have laying around which I need to sell. I have the same exact setup as this Fi Q and TC PR combo except everything in 15" version. I was pissed to find out that the box was 1" too tall to fit in my trunk. I had about 20" in height to use but my entrance to my trunk is only 17"! That was my fault for not measuring the entrance. After having waited 4 months for this 15" box to be built (huge wait list) I bought everything in 12" versions and asked Dave for a favor to have me build me another box within a month. I'm taking a huge gamble with everything but ultimately I know what I'm looking for. I don't want to buy anymore boxes though lol. I have way too many now. I just want to use what I have and make the best of it. I will show you the picture of my 15" box. I'm planning to sell the 15" Fi Q and maybe keeping the 15" box and PR's for a future home theater build (unless I can find someone to buy them off of me). Was thinking of matching it up with the 15" Tc Axis since they're practically identical in cone design.

 

[T3mpest 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.