4th Order Bandpass needs checking

[mikee55]

Hi all, want to make a small 4th Order Bandpass box using 2 6 "ers I got lying around. I downloaded the latest WinLsd and installed my drive T/S parameters. I played with it for a while and would like to know if my design is okay? One cavity is ported, one cavity at 2L and the other 4L, which cavity holds the port? What port frequency can I choose?

Thank you

Mikee55

[GM]

Can't open it, but the front cavity has the port: http://www.diysubwoofers.org/bnd/4thorder.htm

GM

[mikee55]

Hello GM, I had no trouble opening it, but I can't CTRL PrtScn and paste it in Paint, like I normaly do.

So I've botched it. I must say I didn't notice the port length and didn't want it tuned to 35hz!!

Obviuosly, my tuning is wrong, but is the cavity sizes okay? Maybe tune nearer 61hz?


Thanks for helping.

Mikee55

[GM]

Greets!

For my records, what brand/model driver is this and are specs published or measured?

FWIW, I'm very pleased with the free demo version of SnagIt 5.0 for copying active windows or just a portion of one without having to mess with using Paint/whatever to crop them.

Anyway, assuming a maximally flat response is desired, then tuning to Fs requires an IB rear chamber (> 10* Vas) and no, these Vbs are only good for a narrow BW up in the mid-bass/lower mids. Unibox seems a better freeware choice for designing these. For example:

Vbr = 14.5 L
Vbf = 1.78 L
dport = 6 cm
lport = 28.86 cm

Tuned to 120 Hz, it runs out of Xmax around 78 Hz, so a lower tuning/wider BW/bigger box is required to offset this at the expense of broadband system efficiency.......

GM

[mikee55]

Thankyou for replying.

Its an Audax HT170FO 6" Fibreglass driver. Basicaly, I used it as a Guinnea pig with richie00boy and measured the T/S with his help.
I have 2 such units, and would like to build an Isobaric 4th order bandpass, to use in my people carrier. I was thinking small box, resonable spl because, I have a small amp to power it. I'm seeking a quality bass to help with the vehicles built in full range drivers.
I got the idea from here
http://www.diysubwoofers.org/project...o/homepage.htm

Will look at Unibox

Thank you

Regards

Mikee55

[mikee55]

I'm scared of spreadsheets

I changed the default driver parameters but didn't know what to do. Now looking for a manual to read!!

Mikee55

[GM]

You're welcome!

Hmm, OK, since a different tuning is usually required for vehicles due to their cabin gain and factoring in what will be a tiny front/rear Vb due to isobaric loading, the vent will be a significant fraction of total Vb.

GM

[GM]

Hmm, don't know if there's a HELP file.........

Anyway, when you change the 'drive unit parameters' box and hit 'enter', the other driver variables are updated, but you still have to design each box type you're interested in. If you want to save your driver, then click 'save' in the 'design data base' box. If you want to use an existing driver, then scroll down to find it, click on it and the SS is updated.

Having just DL'd it the other day to respond to anothers Qs, I'm not completely versed in the use of this SS, but the rest of the fields/options appears to be self explanatory with prompts for minimum port diameter, though it's based on a higher vent mach than I prefer and even if you totally screw it up somehow you can reset all the defaults in the 'constants' box. If you change/screw up the driver specs, then just click 'reload' in the 'design data base' box.

GM

[mikee55]

Hello GM, I open the zip file, click on the xls and Openoffice opens up its spreadsheet program. If I hover on the default driver, it offers me to type a new name to start a new project. I change the T/S as far as I can, then nothing. I didn't download a data base because I was using my own measurements???
Which are

Re =6.7 ohms
Fs =61hz
zmax =39.9
sd =0.14
Vas =14.53814
Qms =2.6254
Qes =0.5298
Qts =0.4409
Power 50 w
Spl 90dB

I must be missing somthing?

Regards


Mikee55

[GM]

Still can't open it with Winzip. Regardless, when I add a name and basic T/S specs, it's changing the data in the 'Parameters of Single Unit' on the 'fly', then I save it using the 'Design Data Base' box. Maybe without the data base loaded it can't complete all the rest of the fields that work in the background and/or maybe it has macro issues with Open Office as it did when I tried V3 in Excel 97 along time ago.

GM