Having a very hard time getting help. PROS ONLY!

[mendon mafia 10+ year member]

I think i may knock out the short port wall and then add another port wall 26.25" long This will decrease the port area 39" for each box and should increase the volume quite a bit. Hopefully this will increase the efficiency in the low end and lower it in the top end.

sound like a good idea or no?

 

[spltuscon 10+ year member]

The numbers aren't really that critical in this case so I wouldn't worry too much about it. Your port is pretty big for that volume so that's probably not helping....but by itself probably not enough to matter. Gorilla glue ***** for box building though...I know its strong as hell, but it needs moisture to activate which isn't good for the mdf and it swells as it cures which tries to push the joint open. Titebond II is the best glue for boxes. I'm not familar enough with that sub to say if you were overpowering it, but your voltage drop is not that significant so you're still feeding it a lot of power above tuning. Most subs start to distort with a lot of power when you get well above tuing. Don't forget that the 1500w rating is just thermal power handling, not mechanical and with no reference to frequency and tuning. It might be just fine in a different box though. Maybe cut down the size a little and with less port area.

 

[CRXBMPN 5,000+ posts]

Gorilla Glue was the single worst purchase I ever made for anything. Ever.

I stand by my idea that its unloading in those frequencies and your pressure in the box is more ideal at the "non distorting" levels/frequencies.

 

[dt053 10+ year member]

A few things to try... but sorry not a pro.

Make sure your amp isn't clipping... your system is more efficient around the tuning frequencies... check it with a O scope.

Have you tried closing the port and seeing if it still distorts?

When the sub unloads, can you tell if it seems to move in one direction more than another?

Have you swept it with test tones and watched the reaction as you move up in frequency... is there a frequency where is stops?

With frequencies above the tuning frequency, can you push the sub inward and have it lock into that position?

What I'm getting at is: does the sub have a dynamic DC offset?

The DC offset could be caused by something as simple as the port geometry... Remember the sub will pull in air not only from right in front of the port but also the sides. which causes the air velocities to be different...( a very good reason to flare or radius a port) this also happens on the inside of the enclosure. If the sub pulls, or pushes air differently, then a DC offset is created and the sub can move more in one direction than another... the harder you drive it the worst it can get.... as the port becomes more restricted when it you try to push more air through it the tuning can change.

If the VC is off center it can cause a DC offset, and if the suspension isn't linear it can cause the sub to move to it's minimal during operation.

Not sure if any of this is your problem but putting my 2cents out here.

dT

 

[mendon mafia 10+ year member]

The numbers aren't really that critical in this case so I wouldn't worry too much about it. Your port is pretty big for that volume so that's probably not helping....but by itself probably not enough to matter. Gorilla glue ***** for box building though...I know its strong as hell, but it needs moisture to activate which isn't good for the mdf and it swells as it cures which tries to push the joint open. Titebond II is the best glue for boxes. I'm not familar enough with that sub to say if you were overpowering it, but your voltage drop is not that significant so you're still feeding it a lot of power above tuning. Most subs start to distort with a lot of power when you get well above tuing. Don't forget that the 1500w rating is just thermal power handling, not mechanical and with no reference to frequency and tuning. It might be just fine in a different box though. Maybe cut down the size a little and with less port area.

its 2k thermal according to steve not that it matters much. but so you think i should make a smaller internal volume box? like 1.5 cubes or somthin?

I also free aired a sub to see what happens then and it moves about the same at the high (51hz) and the 37 hz note for hypnotize but the 34 hz note moves less. and actually the sub moves more in the box on the 51hz note than in free air.

im almost positive its the box. im gonna build a few boxes just for one sub to experiment with. hopefully within the next couple of weeks. I want to build like 6 different boxes 3 with the same volume and tuning but diff port area and 3 with the same port area and tuning but different volumes.

gonna have some cheap 12" boxes for sale soon hahah.

Is it possible that the shape of the box is causing issues? (like the fact its really long and the sub fires into the length)

 

[ciaonzo 5,000+ posts]

ok to clarify all the problems i have 2 seperate boxes which i run BOTH at the same time usually. the specs given are for one box. so multiply by 2 and there ya go.
My amp is used for both subs. wired down to .5 ohm. (1 ohm when im using 1 sub) problem still happens either using 1 or 2 subs.

voltage drop is not a problem i dip into the mid 12's at the lowest. got a 200 amp alt 2 spv70's and a stock batt. only 1 run of 1/0 tho for pos and ground. but as stated before my voltage drop isint that bad.

all my filter and eq settings are set correctly. flat on the eq. filter on the hu is set at 80hz, filter on the amp is probably at 70. If i cross down to 50 i will have no output between 50-80 hz, my momo components are nowhere near as loud as my aplhas. and dont really start hitting until about 80-100hz. (I need speaker pods my doors **** for sealing)

My speaker wire is 10 gauge and i have separate runs for each woofer directly from the amp. the wire shown was just for testing.

Imp rise might be a very likely cause but how do i get around this. never had this problem before. and ive built tons of boxes and systems. non having this large of port area though. but thor and all those other guys with big ports dont have this problem either so idk.

Lots of good input in this thread, particularly in posts #17 and #19, so I won't reiterate anything there. One concern of mine is that you're using two low pass filters. This can work but it takes some planning. If you cascade two filters you can get good results and you can get very bad results, all depends on the application and the execution. If you use two steep filters right on top of each other you will get a peak right around the filter pole in the pass band. Couple that with a high inductance figure for your driver and you can get quite a nasty peak. I can't say for sure if that's what you've got going on but it's a possibility. Try using one low pass at 24dB instead of two at whatever they are now. That's not accounting for anything that anyone else has already pointed out.

 

[ciaonzo 5,000+ posts]

Shot you a PM as well.

 

[SSS 18734 5,000+ posts]

The problem is most likely with your enclosure. Your box design should reflect the excursion and power handling abilities of your sub.

Download WinISD Alpha (not beta) and correctly enter the parameters of your sub. There is a tab that allows you to see the excursion of the sub at any given frequency with any given amount of power. Adjust your box design according to that and build a new one.

Remember, cabin gain exaggerates low frequencies. You could be expecting too much of your sub at higher ones. At a tuning of 37, you're going to have a huge peak around those two lower frequencies.

 

[mendon mafia 10+ year member]

The problem is most likely with your enclosure. Your box design should reflect the excursion and power handling abilities of your sub.
Download WinISD Alpha (not beta) and correctly enter the parameters of your sub. There is a tab that allows you to see the excursion of the sub at any given frequency with any given amount of power. Adjust your box design according to that and build a new one.

Remember, cabin gain exaggerates low frequencies. You could be expecting too much of your sub at higher ones. At a tuning of 37, you're going to have a huge peak around those two lower frequencies.

i used to have a pair of 12" re sx's and i ran them in 5 cubes net tuned to 32 hz and never had a problem. The port was small though only 58" and it was straight not L shaped

 

[dappa5 10+ year member]

.02 here port to big the reason it looks the same when you free air it is because you are loosing cone control /"unloading" / over those freqs gl with new boxes

 

[mendon mafia 10+ year member]

.02 here port to big the reason it looks the same when you free air it is because you are loosing cone control /"unloading" / over those freqs gl with new boxes

it actually looks completely different when i free air it.

the cone moves MORE on the higher note (hypnotize young jeezy) IN THE BOX than in free air. How could the cone be more controlled in free air than in the box?

the low notes both move less in the box but the same ratio to each other the lower on moves less in both cases.

 

[mlstrass 5,000+ posts]

PM DDbump as he had a similar problem with his HW's for a while. Don't remember what we did to get it resolved...

 

[mendon mafia 10+ year member]

PM DDbump as he had a similar problem with his HW's for a while. Don't remember what we did to get it resolved...

So DDbump got back to me and he said he had this problem with his HW's and alpha's.

He said he thought it was the suspension //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

gonna experiment more when i find time. I love the lows on these subs to much to swap out at the moment. below 40hz is just awesomeness to my ears.

 

[SSS 18734 5,000+ posts]

Another issue that I didn't pay attention to before was your port. The end of that port is awfully close to the corner of the enclosure - Your sub is seeing a port that is about 5-6 inches longer than you intended it to be (unless you intended the design to be that way).

In either case, you should try dropping the port area a bit. 25-35 square inches should be more than adequate. This will also allow the end of the port to be further away from the side of the box.

I suppose it could be an issue with the sub itself, but there are a lot of other variables here that could easily be the solution.

 

[photocrazy8 10+ year member]

box looks way off, you need to redesign it...