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musgofasa

3 SSA Evil 18s B Pillar wall 2002 Suburban Enclosure opinions wanted

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Hi guys,

Just got the third 18 in this week and we are starting a new build in a 2002 Chevy Suburban. We've got a TON of room as we're going to go up to the B pillar. We're using 3 SSA Evil 18" subs on 3 Linear Power 2250 amplifiers which should be at 2500w ea (maybe a touch more at 15.8v we will be running with dual alts/batts etc). I've modeled these subs till my head hurts and I've asked a few people for opinions on the enclosure and gotten quite a mixed result.

The most popular opinion has been a 4th order using 3 to 3.5 cu ft ea sealed and 9 to 10.5 cu ft ported...modeling looks best to me at 3.5 and 31.5 cu ft with a 30x17.25 port  (roughly 90% of total Sd) Gives me a port velocity around 20m/s at peak but the low end of the output suffers a little in the model. 

I've built literally thousands of boxes but only a few walls and honestly I'm not sure how it will perform considering the smaller cabin space in front of the box. Our ultimate goal is a reasonably musical response with as much output in the hair trick range as possible. Doesn't have to play into the teens and doesn't have to do 160s at 55hz but would like it to be a demo monster and play music. 

With that in mind I've also modeled a 6th order and ported walls and come up with a better looking curve...I have only done a few 6th orders and never anything nearly this large. Most of mine have been 1:1ish depending on modeling but this one seems to work out better at 18 rear tuned to 24hz and 25 front tuned to 50hz. 

Has anyone here done a band pass with these subs in a very large vehicle like this? Or would anyone be willing to take a look at the numbers on these subs and see if you might have a better idea on the band pass design for them? I've seen quite a few vids of 4th orders and I know a few people using 4ths but haven't heard them. Considering our goals and the relatively low power I want to take advantage of all that airspace :-)

  1. Subwoofers in question, number of subwoofers & subwoofer size: SSA Evil 18D2
  2. Amplifier being used, specifically the model number. Linear Power LP2250 
  3. Fabrication skill level: Expert (27 years building and competing)
  4. Preferred material to be used (i.e. MDF, fibreglass, etc) MDF multi layer
  5. Vehicle which the subwoofers will be used in: 2002 Chevrolet Suburban 
  6. Musical preferences: Demoing at shows, pop, some rap and Dub and a LOT of Rock/classic Rock
  7. System goals: Primarily fun at shows and parking lots. Demoing low tones and musical
  8. Previous subwoofers you have used, and their installation particulars: many many many brands types of installs over 27 years
  9. List any research you have previously done: Youtube vids of these particular subs and others with 3 18s as well as comparable subs, checked with other builders and searched here for band pass and threads on these subs. 

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Welcome, and thank you for grabbing some Evils.  I am not a pro at this type of install, so I will let the guys who have done these jump in.

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Thanks Aaron. I talked to you about this one a while back too....we were only going to do 2 but decided to use that third amp we already had on another sub instead....changed the landscape of the install some. Still waiting on that third sub to arrive...hopefully any day :-) Would love to get this thing playing by Finals in KY but shooting for early November if not

 

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If anyone is interested in the models here are three spl graphs.....Red is 4th order (10.5sealed, 31.5ported) dark blue is ported (21cu ft at 28hz) and green is 6th order (18rear at 24hz and 25front at 50hz)

3118s.jpg

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These huge wall builds are over my head,  but I will say 3 18" evils is gonna be rediculously loud in a wall. And I don't know if this is off topic or not, but will this truck be at finals in Louisville? I live in Kentucky myself and would love to hear it.:cartman-unsure: 

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We will be in Louisville for sure but the truck being done by then is pushing it......I would LOVE to have it done so Ray can bring his toys and help us tune the amps :-)

 

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Welcome to SSA. Where are you located ???

Linear Power amplifiers !!! Nice !!! I have a few myself. Can't wait to see those LPs pushing some Evils !!!

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We are in upstate SC (Greer area). This will be the first SPL oriented install I've done with the LP amps. After hearing Keith Payne's Strokers and seeing that voltage stay up so easily it was a no brainer. And the Evils are supposed to be very good sounding woofers so I'm hoping to get a pretty musical build out of this. We are using MMATS Pro mids/highs and another LP amp to push those as well...should know today whether it will be a 2150 or another 2250....fingers crossed I can talk him into another big one :-)

 

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Cool. I was in Columbia SC the other day picking up a Holmes Trucking truck and trailer for their local office here in Jackson.

Should be an interesting build. Post pics !!!

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Can't wait to see pics. That's an impressive list of toys!

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Here is why I'm questioning which enclosure to build....with the crossover applied I get such similar results on the graph...normally there's some sort of obvious winner.....either means these are the most versatile subs ever or I've got something off in my models. While I don't depend solely on models, I don't have any first hand experience with this massive type sub in a wall build and my gut is telling me to do the 4th order anyway. Probably because I'm just comfortable putting the subs in the sealed side and being easier to tweak anything on the other side. The up facing arrow shows the curve of the 4th order model....the down facing arrow is to the 6th order model.....the other two curves are for reference. One is for a ported enclosure and the other is sealed. Sadly the model shows me getting virtually the same output from a ported box in a flat wall. This would make my life so much easier lol. With the power I am using I want the tight, controlled bass of a sealed enclosure but the extra output from a band pass.....my gut says that using a gigantic port (port = Sd or slightly smaller) that I will get that since the box is so huge.....but half of me thinks that 10.5 cu ft for 3 18s is too small for that to work the way I want it to at lower frequencies....something about the group delay just doesn't feel right......now that I've thrown all that out there......anyone got any ideas?

graph.jpg

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You state musical response in your first post.  If you meant it, then just do a normal ported box.  A 6th order remodeled could also do that, but you are focusing too much on the peak and not on the overall response.  That will help on the hair trick side, but not on the musical.

Everything is a trade-off.  The one I would avoid though is the 4th order BP.  It is recommended by everyone else as they don't seem to mind one note fart cannon's and it is a cool trend.  That trend happened in the late 80's too and rode off into the sunset for non-remote firing applications.  It should stay there.

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I agree m5......sadly, if all I was worried about was musical response I would be building a much different install for this guy. He (who owns the truck and is paying the small fortune for the build) wants a ton of air moving. More sadly he isn't giving me the luxury of saying it's ok to have a one note wonder enclosure. It was with that in mind I started down the 6th order path. Basically this thing will have SQ quality mids/highs or close to it and extremely SQ quality amps along with what I believe will be good sounding subwoofers capable of completely drowning out and front stage I could build short of hundreds of pro drivers lol. In the end he has heard a bunch of top notch demo builds with tens of thousands of dollars in them and wants to play on their field.....he's $20k short of the big boys but I'd like to get him as close as I can with what we have. I am convinced he'll be ecstatic as long as the bass is violent whether the transient response and overall bandwidth sucks or not. Best compromise is what I'm after I suppose

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If the models are any indication at all then a ported box would be the best option for sure.....at 30hz the output is identical. My concern is what will load best into the small space left in the cabin....seems like the BP would move a lot more air but I'm not sure really

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I would be afraid to have such powerful subs in sealed enclosures for a 4th order bandpass box.

I'm tuned in ...for more !

 

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4th order BP are mostly pointless.  If the situation is such that the box is remote from the cabin (not in a suburban) that is potentially different, but then the choice is super narrow peaky 4th or a much broader 6th.  Being narrow in its passband it can have the benefit IF you choose the peak frequency to line up perfectly with the cabin that you have some gain, but the likely hood of that on box one is nearly zero.  Since you have a big cabin you only have 2 choices.  Standard 4th order ported or a 6th order BP.  The 4th order BP is a waste of wood.

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On 9/14/2016 at 2:09 PM, musgofasa said:

If anyone is interested in the models here are three spl graphs.....Red is 4th order (10.5sealed, 31.5ported) dark blue is ported (21cu ft at 28hz) and green is 6th order (18rear at 24hz and 25front at 50hz)

3118s.jpg

model the 4th order bp at 9 sealed and 18 ported tuned at 44hz that should smooth response out and still have a decent passband and peak. 

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surprisingly makes very little difference....lowering the tuning to 44 even at the larger size does smooth the response slightly but it does nothing for the low end.....although that's what I wonder with the increase in total box volume in relation to the shrinking cabin volume.....I've seen these in action and getting it done with less power and less cone and certainly less quality drivers so I could just be paranoid lol.

4thonly.jpg

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Actually now that I do that and add filters to the ported box I checked the needed port sizes and holy smokes! lol. Ported isn't going to be as easy as I thought if I want to go that route....needs a LOT of port area AND length to get tuning down.....if I tune it even a little higher than Fs the ported enclosure appears to lose any possible advantage....in peakiness and bandwidth....not to mention overall output.....granted that's on paper....but it's worth noting....just a thought

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Here's something of note.....I've heard that it's a good idea to tune the ported side of a 4th BP at or close to the Fc of the sealed side....at 9 and 27 the tuning would be 42.5hz which is really close to what I want and should mean a windy output in the low frequencies....it also gives me a 6" long port which is about where I want the thickness of the loading wall to be while making the ported side 15.5 square inches per cubic foot....if I go with the bigger box it tunes at 40.5hz and that works with a 16 sq in per cu ft port at roughly 6" deep as well.....could go slightly smaller to shorten it to a less deep loading wall......I'm liking the idea so far :-)

 

 

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Remember everything you have ever "heard" is from someone with some driver in some vehicle.  Your situation is not the same.  sq in per cuft is not a way to determine port size.  I realize you are trying to move air, but again you used the word musical in your needed description.  If you care at all about the latter don't go but rules of thumb or the grapevine.

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25 minutes ago, ///M5 said:

Remember everything you have ever "heard" is from someone with some driver in some vehicle.  Your situation is not the same.  sq in per cuft is not a way to determine port size.  I realize you are trying to move air, but again you used the word musical in your needed description.  If you care at all about the latter don't go but rules of thumb or the grapevine.

I agree, the bandwith on the ported enclosure is more efficient for music. Both bandpass designs modeled have a nasty roll off. Will they be loud, yes. But if you care about moving air & being pleasant to the ear while playing music then you will need that line to be as flat as possible without tuning ridiculously low. A wider wave tends to move more air as far as frequency goes. When playing music, songs are never produced with a similar frequency range on the bass line. That's why one song will hit like crazy in one design & lack output on another design. Unless you're going strictly for SPL, I would stay far away from a 4th order design. There are never any "rules of thumb" when it comes to any design beign that there are too many variables between not only the equipment but the variables in the actual vehicle itself.

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This is why I don't do the Internet forum thing anymore....5 replies to this post telling me why not to do a thing without even one constructive thought as to what would work. Saying a ported box would be better is great. Perhaps take away the "rule of thumb" BS and make any suggestion for me to follow up on. I was hoping for a technical conversation to help me work out some details but only one person (thank you DangRebel) has offered any constructive input. I NEVER said it had to be a 4th BP. I asked for ideas to help make the best use of the available space and listed everything I am working with so you would understand I'm no idiot. I've been doing this nearly 30 years and I know rules of thumb are not the bible of box building. I also know they exist for a reason and when calculations work out to be within a rule like that it's ok to take it as reinforcement that I'm going in the right direction. How about offering some insight as to what airspace, port area and tuning style you would use if you were asked to do the build instead of telling me a single reflex BP is a "waste of wood". This is a box builder's dream. I have the best of all conditions for Hofmann's iron law here. Nearly unlimited space, enough power to get the job done and I want low extension with the best compromise for transient response I can get while maintaining high output at 30ish hz. I don't care if the sub will play one note over 55hz at all and I'm not looking to compete against a meter. i think it should be possible to deliver something pretty awesome but telling me how not to do it won't get me any closer to the goal at all. 

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