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musgofasa posted a topic in Newbie Sign INHi 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 :-) Subwoofers in question, number of subwoofers & subwoofer size: SSA Evil 18D2 Amplifier being used, specifically the model number. Linear Power LP2250 Fabrication skill level: Expert (27 years building and competing) Preferred material to be used (i.e. MDF, fibreglass, etc) MDF multi layer Vehicle which the subwoofers will be used in: 2002 Chevrolet Suburban Musical preferences: Demoing at shows, pop, some rap and Dub and a LOT of Rock/classic Rock System goals: Primarily fun at shows and parking lots. Demoing low tones and musical Previous subwoofers you have used, and their installation particulars: many many many brands types of installs over 27 years 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.
I posted this over on SMD, I figured I'd put it up here as well. So I've been wanting to experiment with a series tuned 6th order bandpass design for quite a while. A conversation I've been having with another SMD member has finally motivated me to proceed with this experiment. First a little background. You don't see a lot of series tuned BP6 boxes out there and there is even less information on how to design them. What I have been able to find has mostly been conflicting information as to if and how the tunings for the different chambers interact with each other. Some info said they don't interact all all, some said the rear chamber will be tuned lower than if it was vented to the outside, and other info said both chambers will affect each other's tuning. I really want to know what happens so I built a test box to see what's going on. Here are some pictures of the box construction. Its mostly made out of 3/4" OSB. I used OSB because I don't care how the box looks, it actually stiffer and holds screws a little better than MDF, and its $14 a sheet. The box has a 3 cube rear chamber that I was shooting for a 24 hz tuning, the front chamber is 2.4 cubes with a target 54 Hz tuning. The sub is a Dayton Titanic 15" I picked up a while back for a song. Here is the basic layout of the box. The shorter port panel in the rear chamber is removable so that I can adjust the tuning. This is the box, ready to go. The front chamber ports are completely external so I can change them without affecting chamber volume. The three 4" ports are just press fit into the panel so I can pull them out and cut them down easily. There is a small window looking into the front chamber so I can see what the cone excursion looks like. With a little bit of sawdust on the cone it's very easy to see what frequency it stops moving and thus is the tuning frequency. Here I put a bunch of foam board insulation in the rear chamber to decrease its volume and further raise the tuning. You can see my Behringer NU3000DSP amp off the left that I was powering the thing with. The question: The question I'm trying to answer with this project is "how does the tuning of one chamber affect the other?" The experiment: To answer the question I individually changed the tuning of each chamber and measured if/how it affected the other chamber. The results: The results were pretty conclusive, the tunings of the two chambers are both linked together. This was not the result I was hoping for or expected. I expected that changes in the front chamber tuning would affect the rear chamber, but not vice-versa. However what I found was when I lowered the rear chamber tuning it lowered the front as well. Conversely, when I raised the rear chamber the front chamber's tuning was raised as well. When I sealed off the rear chamber, making it a 4th order bandpass, I then measured the front chamber and its tuning frequency was significantly lower than when the rear chamber was allowed to vent into it like normal. As I expected, changes to the front chamber's tuning frequency also affected the rear chamber in a similar fashion. This means anyone who tries to design one of these boxes using the regular methods for tuning a ported box or 4th order bandpass is in for a big and unfortunate surprise. Conclusion: This was definitely a worthwhile project for me. While I did not get the answer I was hoping for, at least I did get an answer. Unfortunately this means that designing a series tuned 6th order bandpass is a total pain in the ass. Everything is fine until you want move the two chambers tuning frequencies closer together or farther apart. Then it becomes like a dog chasing its own tail, you may be moving, but you aren't getting anywhere. Based on what I've learned I would venture a guess that the vast majority of series tuned 6th order boxes other people have built are not functioning like the builder's think they are. I know boxes don't always have to work as intended for people to be happy with them. I just wonder what kind of performance they are leaving on the table. When I was done playing around with the thing I threw it in my Jeep to see how it sounds. It actually sounded really good, quite punchy. I still need to drag the box outside to measure the frequency response and efficiency. When I do I'll be sure to post the results to this thread. For anyone that is interested, the Hornresp software can model series tuned 6th orders and it turns out it models them correctly. That's where I got the data indicating that the front and rear chamber will both affect each other, so I guess whoever wrote that piece of software knew what they were doing.
Figured I should start a build log since I've gone through so much trial and error in getting this stereo to sound good. I'm already done with most things but I did take pictures along the way so i'll get that all uploaded when i get photobucket or imgur figured out. I bought my passat almost a year ago, the weekend after black Friday to be exact, and knew immediately that it needed some love in the bass department. I had a rockford p-300-12 powered enclosure lying around that i once had mounted in a big self-propelled sprayer that i basically lived in for 3 summers, threw that in along with a rockford loc, rockford rca's, and some ebay 4ga cca to get it powered. That sounded awesome for the average non-basshead and would suffice until i found a real solution.... Did some searching and found this great place! After searching and reading here for hours I decided on a Fi BL 12 for a sub and a BRZ1200.1 hifonics amp to power it since i'm a poor college student and can't afford a bc, aq or saz lol I built a vented box for the BL that was 2.68ft^3 tuned to 28.5hz After I finished the box I had to stuff foam above the headliner near the upper brake light and under the rear deck to stop some rattling. Installed some dampener (dynamat and ebay stuff) to the trunk lid, under the trunk carpet on the floor, and rear deck from inside the trunk. dampener helped a ton. After the substage I realized that the stock front stage was not going to cut it... I knew that I wanted to fill some of the lacking upper bass frequencies with some volume so I was looking for the biggest components I could get for a decent price. Ended up getting the xr1800p components from Kenwood. They've got a big 7" woofer and an oversized 1 3/16" tweeter with external crossovers. currently the set is being powered by a dusty old pioneer 4-channel amp GM-x524. I'm not perfectly satisfied with the front stage for now since the amp likes to protect at high volumes and I've got some fuzzy distortion from the tweeters in certain frequencies. once i change the amp to the GM-d8604 class d 4-channel from pioneer I think it will get much better as I have the older GM-d9500f version in my s10 that never protects and has no distortion until extreme volume. also ran another 4ga run of cca to the trunk and a distribution block when I added the second amp. Also changed out the stock HU for a Pioneer Avh2600bt touchscreen unit which is fantastic for the money. I decided that the box was tuned too low so I chopped 10.5" off the port giving me a 2.88ft^3 net volume tuned to 32.2hz and was much happier! Now for the real reason I'm starting this build log.. I'm going to try a 6th order bandpass to keep this 'new to me' low end rumble and get back the awesome upper frequency volume from my mtx square sub in my s10 for when i want to blast the 50hz Flux Pavilion bass cannon! Much more to follow, including pics for the above^ stuff!