Polyfill

[basshead08 0]

I am in the process of building a box and am thinking of using polyfill. I just wanted to know if polyfill works the same with ported enclosures or is it purely for sealed boxes only?

[BKOLFO4 29]

It can work for ported boxes, but it is experimental. If you are "increasing" the size of the box, that will also lower the tuning frequnecy. It is hard to predict how much "increase" in volume you will get, so you could not predict how much shorter to make the port wall to keep the same tuning. It would be build, test, modify, build, test, etc. . .

I also would not recommended, since it can interfere with the airflow inside the box, which would also change the tuning frequency. worst case it could make the enclosure react like a leaky sealed box instead of a properly tuned ported box. . .

Are you tight on space?

[basshead08 0]

Yes I am tight on space. I am going to have 1.9 net cu.ft. for one BL12.That is absolutely as big as I can go. I was just wondering because I know that 1.9 is towards the low end of that speaker's enclosure specs.

[BKOLFO4 29]

Is that before driver and port displacement, or is that net volume after driver and port diplacement?

What are your dimensions?

[NDMstang65 403]

Personally wouldn't polyfill a ported box...but as brian said what kind of dimensions are you working with, that is on the small side of things...

Thanks!

-Nick

[johnecon2001 82]

Have you already bought the sub? Maybe go down to a 10" BL

[basshead08 0]

Well a friend of mine has one and I am looking at getting his bl12, so I am locked in to a 12".

[NDMstang65 403]

Is the 1.9 cubes after all displacements?

Thanks!

-Nick

[basshead08 0]

Yeah the 1.9 is after all displacements.

[///M5 2,833]

I hope by after all you mean net. If it is gross your box is WAY too small, if it is net you could surely line the walls with a single layer but I wouldn't stuff the enclosure. I would try to get more space though as that is really tight for that driver.

[BKOLFO4 29]

1.9 after sub and port displacement will work. What size port and tuning frequency?

Can you post up dimensions of the box you have in mind???

[basshead08 0]

I have been working on designs all morning. I have reworked the design. I have 3.25 cu. ft. after wood and sub displacement is subtracted. I don't think polyfill is an issue anymore, because I seem to have plenty of airspace. However, I have NO experience building ported boxes. So I am trying to learn as much as I can, because I take pride in doing all of my installing myself. Anyway, I need ideas for a port, I no nothing about tuning so I need ideas for a port. If possible give all specs (size, length,) Box is a basic wedge design. depth1=46"

depth2=28"

height1=13"

height2=5"

slope=24.65"

Thanks!

[BKOLFO4 29]

use an online calculator like this one:

http://www.carstereo.com/help2/Articles.cfm?id=31

For a single 12", I woudl use (1) 4" aero port.

http://www.partsexpress.com/pe/showdetl.cf...tnumber=268-352

Use the calculator, and then add 1" to the length for end correction for the flared ends.

[basshead08 0]

use an online calculator like this one:

http://www.carstereo.com/help2/Articles.cfm?id=31

For a single 12", I woudl use (1) 4" aero port.

http://www.partsexpress.com/pe/showdetl.cf...tnumber=268-352

Use the calculator, and then add 1" to the length for end correction for the flared ends.

That port calculator says that I should make my port 22 inches long. I have heard that having a port that long can cause unwanted noise. Any truth to this? Also it said that the port should be at least 6 in. in diameter. Will that aero port still work even though it isn't big enough or long enough. Also if I use a rectangular port, could I make a 90 degree turnn in the prot in stead of making it one long straight shot?

[BKOLFO4 29]

What volume and tuning gave 22"? Sorry, I do not understand the dimensions you posted above. . .

A 4" aero is sufficient for a single 12" sub. The flare on the port will allow for less port area without port noise. Testing has been done to show port area can be cut in half with these ports. . .

At 1.9 ft^3, the 4" would need to be 15" long for a 32-33 Hz Tuning.

Brian

[basshead08 0]

What volume and tuning gave 22"? Sorry, I do not understand the dimensions you posted above. . .

A 4" aero is sufficient for a single 12" sub. The flare on the port will allow for less port area without port noise. Testing has been done to show port area can be cut in half with these ports. . .

At 1.9 ft^3, the 4" would need to be 15" long for a 32-33 Hz Tuning.

Brian

I changed my design and wound up with 3.25 cu. ft. At 32hz it calculated that I would need a round prot of at least 6.85 inches in diameter and 22" long.

[BKOLFO4 29]

Use the 4" aero, it will be enough port. Calculate the length based on the 4" diameter, and then add 1" for the end correction.

[shizzzon 461]

I have to ask this...

BKOLF04, what is the maximum port velocity before audible distortion is heard?

I do not know this answer but I have been told not to exceed 145 ft\sec, although i tend not to go past 130 ft\sec.

The 1.9 cuft design for 33 hz would need a port area of 26 sqin.

The calculator i am using, however, shows no change in port velocity when changing from flared to flat ends, the only thing that changes is the length of the port.

According to this calculator, a 4" flared port would yield a max port velocity of 276 ft\sec flared or flat using 1,500w of power.

Is this calculator not calculating something or is this port velocity acceptable?

[BKOLFO4 29]

I am going by testing done by Lloyd Lowery (BigBassMan on most forums). . .

I know at one time David (TeamPSI) was running (2) MT 15's with (4) 4" flared ports (48 in^2) doing 154+ and no problems. Calculate that out, and I think he should have around 115 in^2 with those two drivers.

I have run a MT 15 on 4000 watts with a pair of 4" aeros with no problems.

I have a bandpass box under my desk with a 10" driver and a 3.5" port (9.5 in^2, but it is largest that will fit). In a bandpass, that should have 25+ in^2. Sounds terrible with an open end, but I designed and had tooled a flared end for the 3.5" tube. Slide the flare over the end of the tube, all noise is gone, and it sounds great.

I am not saying it is always the best solution, and for metered SPL I would want the full required port area. For daily bumping with tight space, a 4" aero port should be fine. . .

Brian