Rail

I've been reading the Loudspeaker Design Cookbook and found the effects of lobing due to driver placement on the baffle, but am still left wondering two things. Use the picture below as a reference to how the placement would differ. Assume same port length and volume for each. #1: The port ends in a different location inside the box, does this have different loading effects on the sub? From appearance, it would seem that the air flow in each would be somewhat different and affect the subwoofer? #2: What happens to the subwoofer and response as you move it closer or farther away from the port? Is it best to have it centered or off to a particular side?

Alright that clears it up a lot, thanks both of you guys! Makes sense now that its explained.

Had to make it all pretty with a ruler, don't know what it would have looked like otherwise haha Ok so slot port enclosure A would have a slightly higher SPL than B due to the increased pressure for air to be pushed and pulled through the port? My initial thoughts were that that would be the case. I understand that subs up and port back or whatever variation depends on the vehicle, but what about the placement of subs relative to the slot port if the port and sub directions are not changed? Still centered? Because I would think that if you had the sub either very close or far from the port then the excursion might change slightly due to how the cone interacts with the pressurized air inside the enclosure?

Agreed, T/S specs would be great to estimate possible enclosures. I want to see what you could do with two 18" in a daily setup tuned around 20 to 26 hertz. (Just can't get enough of those lows)

At this point I'm thinking of waiting and getting the DSS Magnetar, Sundown Team, or DC Level 6. In the meantime I'll be able to do some sound deadening that I haven't got around to yet. The rattles from ceiling lights and controls get annoying after a while and it should sound a lot cleaner once its deadened.

Thanks, I forgot about Quentin's subs, but they look great! I was actually very interested in his Trident subwoofer, it sounds like it will be one heck of a sub. I like how he is gearing both the Trident and Magnetar toward the low frequencies, which is exactly what I'm looking for. Since the Trident is not going to be here for a while I might have to check out the Magnetar. By any chance do you know approximately when it will be out this year? Edit: (Just checked the Magnetar thread and it said about June)

Oh ok I didn't even know T3 was out of business. I only recently heard of them when looking for 4" coil subs. I'm going to keep an eye on the team sundown subs for sure, and when I get the time I'll have to plot out the DC, DD, and the Tantric in winISD to see which I can get loudest with at 20 hertz. I appreciate the opinions thanks!

I was running it on an AQ3500D.1 at 1 ohm. I have a Mechman 370A alt. I always paid special attention to make sure I didn't clip the signal. Its a shame, the sub sounds amazing and it has no problem with the low notes. I had it in a 4.5 cu ft enclosure tuned to 26 hertz and it sounded great musically and dished out the lows, while still getting pretty loud. It must be the sub's leads though, out of all of the other subs out there on these same amps there seems to be no issue. It took Fi 3 months to build my sub I had it playing for 4 months before the leads went out. Sent it in to get reconed and it took them a little over 2 months to get it back to me. After that I have had it running for 5 and a half months before it recently had the leads fail again. If this is bound to happen again even with the new leads then do you guys have any suggestions of other subs that are loud, musical, and like the low notes? Probably going for a 4" coil with higher power handling. I've been busy and haven't had a lot of time to look into details but heres a list of subs after a brief search : DC Level 6 T3 TSNS Tantric SHD Team Sundown (don't know when it will be released but looks promising) DD 9900 American Bass VFL Comp Ground Zero Plutonium Soundstream X3 Right now I'm most interested in the Level 6, TSNS, or the SHD. Any input on any of these subs or other ones that might be of interest to me? I might be looking at 2 18" tuned somewhere from 20 to 28 hertz. Definitely going for the lows, and want to be able to pull a decent hairtrick.

Last time I sent in my SP4 to get it reconed it took 3 months (I don't trust myself to do a recone and have never done it before). It just went out a second time due to the tinsel leads (again), and ironically the day after that Fi released the new FOAD leads. I'm questioning if I should give the new leads a shot or if I should look for a different sub.

In order to achieve the same tuning, your port will need to be slightly shorter if you increase the volume of the box. Power handling is reduced slightly due to mechanical limits. As for reproducing certain frequencies, a larger volume box will enlarge the peak that exists at the tuning frequency. It will thus be louder, but if the peak is very large then the other frequencies will be a bit quieter in comparison which can create an unnatural sounding frequency response with exaggerated loudness close to your box's tuning frequency (Fb). Can be good for SPL, but large peaks are not good for balanced sound or if you are going for SQ. To find the difference of how much larger the peak is, you would have to model it on WinISD or something similar to check if that is the response that you want. However WinISD does not account for cabin gain.

Thanks, I'll definitely have to check this book out. Seems like it has a LOT of good info in it that would answer a lot of people's questions.

Nice improvement from the old enclosure, your designs will get better and better. It would look good with some carpet or black paint. And is the 134.7dB in your sig with your new enclosure? What frequency did you peak at?

I hope you get what you want out of the new enclosure, it should turn out good That's all? Bueller.... ? No one can explain the tunneling effect in more detail (or other effects of a large port)?

Torres is not the most accurate either. When making a sub box, it said that I had 4.75cu ft after displacement, tuned to 26.02Hz. When calculating the internal volume by hand however, there was only 4.48cu ft, and plugging this into WinISD with my port gave me a tuning of 26.17Hz. Tuning change doesn't matter too much but that's a lot of volume that came out of nowhere from Torres. (Yes when I calculated volume by hand I took into consideration the wood thickness, port volume, bracing, and sub displacement). Something must be slightly wrong with the formulas it uses, but it still gets you close. With another box as well, Torres says 3.8cu ft after displacement at 32.25, but by hand and with WinISD gets 4.06cu ft after displacement at 34.81Hz.

Could someone explain the tunneling effect in more detail? I can't find anything about it. It creates a "hollow echo like sound", is there another way to describe this? And would the tunneling effect change the loudness as well, or just the sound quality/acuracy? And how can you estimate how much port is too much and will give you the tunneling effect so it can be avoided? And with the port larger than the sub it will unload? Is this no matter what, or I thought the sub unloading was just when you play below your tuning frequency? Then this would mean port area should be no larger than the Sd of the woofer? For example a 12" sub with a Sd of 481cm^2, which is about 74.56sq in, so port should be no larger than that or else you risk unloading? I have been wondering what the adverse effects of large port area could be, and detailed info would be great (Knowledge is power!)

Interesting info here, so according to the loud speaker design cookbook having large port area won't effect your excursion until you get below tuning frequency of the enclosure. It seems like if you don't play much below tuning then more port is the way to go, but what I am left wondering is if your port can be too large. Larger port reduces air velocity, so can too large of a port be bad if you are trying to move some air for hairtricks? Or would a larger port area be good for hairtricks because the port will be wider as well as longer to maintain your tuning frequency, so there will be more air in the port that is being moved even though it is at a lower speed?

Ok thanks! I thought I might have seen that formula before somewhere on these forums but it didn't have all of the units labeled so it was impossible to make sense of. 15" SP4 xmax spec is 33mm so I will use 22mm overhang to estimate sd is 810cm^2 I ended up with 65.7528 sq inch minimum area for the new box and my old box should have had at least 69.9613 sq in (I could tell that it was too small even without this) That is interesting how the cubic meters gets converted to square inches, 39.37 must be a magic number So this is the minimum that you should use, is there a maximum? I want to move some air, but I suppose that if the port is too large then the port velocity will be too low? Now I probably need a happy medium because 90 sq in of port might be too much (maybe?). Learning new things about car audio! Its interesting to have an understanding of how this stuff works. I can probably reduce the port area and length a bit now, but I am curious with the way it is in that diagram, would the sub be utilizing all of the airspace in the box? Or would it be unloading right into the port? The placement of the sub is probably another key factor in a good box. In theory should it be as far away from the port as possible? In the center of the open area? Probably not right next to the port I would assume

From what I have read here the port area per square foot rule is just a myth, port area has nothing to do with the size of the box. I tried searching more and all I could find was that port area is determined by the parameters of the sub, tuning, and amount of power. So I am curious what formula is used to actually calculate how much port area you need? I am currently designing a new enclosure for my 15" Fi SP4 which is run off an AQ3500. My old box was designed to fit in a trunk but now I have a Tahoe so size is not as big of a restriction for the new box. It was 3.83cuFt @32.25Hz (after displacement). I like the low end but actually would like to try tuning lower. I want to move some air too. I can probably safely say that my port area was far too small (only 46sq in). It was hard to get more port area because then the tuning would go up and I didnt have enough space to work with, but now I do. My new design: Is this too much port? Also is the box size optimal or too big for being on an AQ3500? The width of 24" works good to fit the box in my third row of seats and I only need to remove one rear seat as opposed to both (just in case). It takes a lot of port length to tune that low with that much port area and I wanted to do sub up port back, but I don't know if the loading of the subwoofer doesn't work because it is too close to the port? (See the below sketch) Also would the rear hatch have the effect of a longer port in this setup? And thus with the hatch open or closed would slightly change the tuning? I tried to leave room between the rear of the box and the hatch so that the port is not restricted. I'm also debating on how to run the speaker wire into the box, last time the port was not long and close enough to the amp where I just ran it through the port so that the box was 100% airtight besides the port. The black Photoshop add in is where I was thinking of possibly having some kind of bolt that wires could attach to and keep the box as airtight as I can while still being able to take the box out of the vehicle if need-be. I am not an expert at box designing, so any input, info, tips, or advice would be appreciated. I would like to at least attempt to design this correctly to achieve decent results.

Is the spaced spider option on the SP4 supposed to be free on black friday also? It still says that it is +$40 on both the 15" and 18"