I was wondering if someone familiar with 4th order box graphs could shed some light on this one. I started out with a smaller box design and due to the port and subwoofer fitting I had to make the box larger. Its a 4th order enclosure I initially started with 2.25cu ft net sealed and 3.5 cu ft net ported, the box id ending up closer to 2.73 sealed net and 4.25 ported net.
Port is the same as the initial design at 110 sq inches by 22.5" long. This box is for 2 jl audio 13w7's. Heres a graph baron did for me but I cant tell what the tuning will be or even if the box looks like it will work or not.
FB is 54.84Hz, it will work, though not as well as the previous design-it will give you a more peaked output and not as wide a bandwidth.
Do you still have the original spec I gave you? I've accidentally saved over it with your latest design and can't recall the spec. Also provide amppower to be used so I can check for excursion and vent speed.
I've tried messing with this since in BBpro-can't get it to tune lower, longer you make the port the less volume the box has so tuning starts to go up after a point Will have a play with box volume over port volume.
Ok, I've worked out what's gone wrong-you've over doubled the port area, so are requiring a much longer port to hit the same low tune. Issue is that the port is then taking up too much box volume and you're ending up with a higher tune.
Do you have two ports with total area of 110ci or one of 110ci?
The new Curve isn't as bad as you might think-it's got that curve under it's output, so EQing down the peak could give the same response-or just put up with the excess-if you get what I mean.
Once Richv72 clears up whether he has two ports totalling 110sq in or one 110 sq in port we'll know what's actually going on.
I looked closer at it, there is a bit of a bend around 35hz or so. if you eqd 30 hz up a bit, it might even out. I would rather start out with a better band and then eq out weirdness, than use an eq to get the curve right.
Original post whore!
Stock Sync HU |AC LC2i | Phoenix Gold EQ215i | Soundstream SA120 -> ID CD1eMH | JL 300/2 -> ID X65 | JL 500/1 -> (2) 15" Pyle PL1590BL in IB
Wow a flurry of responses today. Ok ill be running 1500 rms to each subwoofer, or as much as they can safely handle. The original box was supposed to be: 2.25 net sealed
3.5 net ported
110 sq inch of port area
22.5" longThis was going to net me a 52hz tune.
New size 4.25 ported net (after all port displacement) Now I can't tell but I think the graph shows this chamber as only being 3.164 cu ft. 2.73 sealed net (after sub displacement) (same sealed to ported ratio as original specs 1.553 to 1) 2 23" long ports 55 square inches each, total of 110 square inches.
1 port would have been impossible to fit, so i made 2 55 square inch ports. I also made them almost 23" long because that was max length I could fit.Its going into a convertible so I dont really expect it to sound as good as if it were a car with a cabin.
Heres an updated picture of the box progress. Also I really appreciate all the help from you guys, not many places a person can turn to when they have these kind of questions.
Last edited by Richv72; 07-31-2012 at 03:05 PM..
Reason: put in some pictures
you may have the same ratio, but since you made the volume of the enclosures larger and the port is the same, that is why your tune and band went haywire.
it looks beautiful, but you may have to add some ballast to get those volumes back down.
Original post whore!
Stock Sync HU |AC LC2i | Phoenix Gold EQ215i | Soundstream SA120 -> ID CD1eMH | JL 300/2 -> ID X65 | JL 500/1 -> (2) 15" Pyle PL1590BL in IB
All boxes with a port end up with a tuning frequency that's *significantly* different than what's predicted. This can affected your output by 1-3dB. Simple way to fix this is to get a WT2, measure the impedance curve, then cut the port accordingly. (All of this assumes that you install a port that's larger than needed, than trim it until you get the right tuning frequency.)
The location of the port, proximity to the inside of the box, proximity to outside barriers, and a bunch of other factors all affect the tuning frequency. So it's basically impossible to get the right tuning without measuring the impedance curve.
In my 25 years of working in this industry, I've listened to thousands of cars and I can count the ones that sounded great on two hands. Most of them have serious problems and some of the worst ones are IASCA winners... 50% of these guys have plans to change all the equipment in their cars because they don't sound good. In every case so far, none of the equipment has been the cause of poor performance. In every case, it's the installation, the adjustments or the system design. AW
All boxes with a port end up with a tuning frequency that's *significantly* different than what's predicted. This can affected your output by 1-3dB. Simple way to fix this is to get a WT2, measure the impedance curve, then cut the port accordingly. (All of this assumes that you install a port that's larger than needed, than trim it until you get the right tuning frequency.)
The location of the port, proximity to the inside of the box, proximity to outside barriers, and a bunch of other factors all affect the tuning frequency. So it's basically impossible to get the right tuning without measuring the impedance curve.
It looks like a cool tool to have for sure. First time ive evr even heard of one, very interesting.
you may have the same ratio, but since you made the volume of the enclosures larger and the port is the same, that is why your tune and band went haywire.
it looks beautiful, but you may have to add some ballast to get those volumes back down.
Im wondering if the graph is showing a different size ported side then the actual size. I hardly know anything about graphs but it looks like the ported side is only 3.164 cu ft net on the graph instead of the actual 4.25cu ft size measured with the ports taped off, im wondering if that could throw the whole chart off.
if it is supposed to be 4.25 cuft, then yes it is wrong. correct it in BB6 and see if that fixes it. I am going to guess and say that you tuning will still be off a bit. you need longer ports or the tuning will change when you made the volumes bigger.
Original post whore!
Stock Sync HU |AC LC2i | Phoenix Gold EQ215i | Soundstream SA120 -> ID CD1eMH | JL 300/2 -> ID X65 | JL 500/1 -> (2) 15" Pyle PL1590BL in IB
if it is supposed to be 4.25 cuft, then yes it is wrong. correct it in BB6 and see if that fixes it. I am going to guess and say that you tuning will still be off a bit. you need longer ports or the tuning will change when you made the volumes bigger.
Im hoping the larger ported section brings the tuning down because the ports are maximum length I could make them and still be able to remove the box from the trunk. Ill say this is the last time i ever build a fiberglass enclosure because it has been a tremendously time consuming and expensive project. Its like a nightmare, but im in too deep to quit now lol.
Im hoping the larger ported section brings the tuning down because the ports are maximum length I could make them and still be able to remove the box from the trunk. Ill say this is the last time i ever build a fiberglass enclosure because it has been a tremendously time consuming and expensive project. Its like a nightmare, but im in too deep to quit now lol.
lol, it does look like a labor of love.
yup , you are right, I had it backwards. if the volume goes up, it should tune lower. BUT, this is a BP too. both chambers effect each other, so hopefully it was just a key-flub when putting in the stats in bb6
Original post whore!
Stock Sync HU |AC LC2i | Phoenix Gold EQ215i | Soundstream SA120 -> ID CD1eMH | JL 300/2 -> ID X65 | JL 500/1 -> (2) 15" Pyle PL1590BL in IB
Right, you're not in the mire, I've found a fix that is remarkabley easy: Just use one port. Have checked it and you'll get no port noise on 3000w.
I've just remodeled it with the volumes and vents as you describe and the outputs are below. Red trace is with two ports, grey with just one. Not quite the nice plateau we had originally, but much flatter than the twin port option. You'll end up with a 3dB gain at 30Hz Vs 60Hz - before you car wreaks havoc with the response anyway
Baron you are the man, ill definitely stuff the sealed side. Now do you mean just cap off 1 port when you say 1 port? that would give me a port of 55 square inches.
Yup, that would work-though also just thought you might be able to make the diameter of ports smaller, will be more work but might gain better results-will model tomorrow
Yup, that would work-though also just thought you might be able to make the diameter of ports smaller, will be more work but might gain better results-will model tomorrow
Sent from my Motorola DynaTAC using Tapatalk
I could definitely decrease the port size for sure, just couldnt increase the size. That bassbox pro looks like a good program is it pretty easy to learn to use?
Sorry, took a dive down the stairs and not been to work, not sure when I will. If things are pressing you should just block off one port for now and I'll get back to you at some point.
Bbpro is easy enough to use when you understand the graphs, has a few foibles but much easier then anything else I have used-other than Eminence designer which was a slightly watered down version of it and what I used before stumbling across bbpro online after my eminence disc finally stopped working after 10years.
Good luck with the install, will try and get the software running at home and see what I can do.
Need Help with this graph
Will have a play with box volume over port volume.
Linear Mode
