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-   -   port lenght for subwoofer ?? (http://www.diyaudio.com/forums/subwoofers/17262-port-lenght-subwoofer.html)

hilbren 3rd July 2003 09:34 AM

port lenght for subwoofer ??
 
Hey everybody,

When I was 15 (now 22) years old I made a sub woofer, but I think the lenght of the port aren’t write. I made it like the picture below only with two speakers in stead of one [img] http://users.ece.gatech.edu/~mleach/ece4445/ece4445.gif[/img] the speakers in the sub are 8” diameter. And the holes for the ports are 6,5 cm (2.55” )

I already searched for calculation programs, but mostly the where designed for a single speaker sub woofer with only one port. I don’t think it will work on my sub

Can anybody help me with this ??

hilbren 3rd July 2003 01:45 PM

I forgot to give the size; it's 60*26*35 cm and it is made from wood 16mm thick.

mikee12345 3rd July 2003 02:56 PM

ports
 
the picture is of a dual tuned bandpass

- winisd does this.
also 'subwoofer simulator'


but i think that winisd pro cannot calculate 2 ports as there is a bug in the program,i think..


it is good to double check with formulas too,but i dont have them,only sealed and ported.

www.diysubwoofers.org

:nod:

hilbren 3rd July 2003 03:14 PM

So according to this site both pipes should be the same length??
Because the original plans was using two different lengths :?
I am confused

kelticwizard 4th July 2003 03:16 AM

Depends on the individual speaker.

Do you have the "Thiele-Small" specifications, (parameters) for your speaker? Listed will be such things as Fs, Vas, Qts., etc.

If not, what is the manufacturer and model number of these two 8 inchers?

Maybe we can help you there-although bandpass boxes are notoriously fickle.

hilbren 4th July 2003 08:03 AM

this is al thats on the speaker:
PAW-205
XXL Power Sound Laboratory

I made a cad drawing from the current setup:
http://ferry.student.utwente.nl/mode...sub%20copy.gif
both pipes are 6.5 cm dia.
the short one is 7cm and the long pipe is 16cm

kelticwizard 4th July 2003 07:27 PM

Quote:

Originally posted by hilbren
I forgot to give the size; it's 60*26*35 cm and it is made from wood 16mm thick.
So the dimensions you gave us, (60 X 26 X 35) cm are outside dimensions, then? I am assuming they are.

Also, the box was divided exactly in half-both chambers are the same size?

If so, I will return in a few hours and tell you what your box was tuned to. Whether this is the correct tuning or not, I cannot say unless I can find the driver's specs on the internet, which I often can.

kelticwizard 4th July 2003 11:22 PM

Okay. With those dimensions and 16mm buiding material, I got an internal volume of 47594 cm², which I believe equals 47.6 liters. Subtract 10% for speaker volume and ports, and you get 42.6L. No Metric fan here, no sir. Makes my head spin if I do Metric too long :spin: .

If the chambers are equal, then each chamber equals 21.3L.

Ran an Audax 8" in a 21.3L box on WinISD. It doesn't matter what the parameters of the Audax are-a certain box volume with a certain size port will always be tuned the same, regardless of what speaker is in it. The response of the speaker in that box will vary widely from one brand and model to another-but the box will be tuned the same.

The chamber with the 6.5 cm diameter, 16 cm long port will be tuned to 47 Hz.

The chamber with the 6.5 cm, 7 cm long port will be tuned to 62 Hz.

I don't have any experience building bandpass, whether with one port or two. However, I am given to understand that, in a two port bandpass, the response is usually better if the chambers are tuned one octave or more apart. These are tuned 1/2 octave apart. But again, without the parameters to measure the speakers, I simply cannot predict any more than to tell you what each chamber is tuned to.

The best thing to do is to measure. www.audua.com contains Speaker Workshop, freeware which takes some time to learn but which gives you accurate measurements on all aspects of your speaker, including frequency response.

If the chambers are not equal, or there are any adjustments, just post and I will figure out for you what I can.

If you do decide to use Speaker Workshop, you should know that the Pansonic WM-61 microphone element can be repalced by the Monacor MCE 2000 microphone element, apparently widely available at electronics parts stores In Europe.

Apparently, the Pansoonic WM 61 and WM 60 series have essentially identical flat frequency response.
http://www.diyaudio.com/forums/showt...ic+monacor+mic

hilbren 5th July 2003 08:44 AM

Okay I did a little search on the drivers and this is all I could find:

Quote:

De PAW serie van XXL Power-Sound kan gebruikt worden bij grote PA-systemen.
De luidspreker is van zeer hoge kwaliteit, heeft een stevig aluminium chassis, kapton
spreekspoel, vergulde connec-toren en een zeer stevige ophanging.
Vermogen 125/250W
Afmeting 205 x 95 mm
Bandbreedte 30Hz - 3500Hz dB. 92dB
Res. 33Hz
Gewicht 2,7 Kg


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