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Old 25th January 2016, 03:42 AM   #1
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Default Dayton SD270A Bandpass

There's always more learning it seems...

Now is time to learn about bandpass subs.

Is this driver a suitable candidate for 4th order bandpass below 50hz?

http://solen.ca/wp-content/uploads/SD270A-88.pdf

-Shawn
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Old 25th January 2016, 07:29 PM   #2
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Hi Shawn,

I am not able to run the numbers at tha moment but just off the top of my head, the driver should work fine. Depending on the S and Qbp you pick for the alignment, you should be able to get an FL of about 30hz or lower and an FH of around 80hz. With an xmax of 6mm the out put would be limited. I am building a Bandpass as well, almost ready to start cutting wood for the prototype. I will run the numbers when I get a chance. I am sure there is someone with a lot more experience then me though.

Regards,
Matt

Last edited by reloader650; 25th January 2016 at 07:32 PM. Reason: Left out Qbp.
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Old 25th January 2016, 08:43 PM   #3
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Thanks Matt.

My mains will go have an f3 and fc of 95hz. Does it make sense to use a pair of sealed 8" I already have to go down to ~50hz and use a band pass of two below that?

In terms of drivers I have a limited selection, affordable and available from Solen.ca because the CAD to USD exchange is so low and shipping/duty fees Parts-Express is out.

I'll wait to hear back if you get the chance.

Thanks
Shawn
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Old 26th January 2016, 02:12 AM   #4
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This may work for you.
S= .6
Qbp= .9904
Vf= 28.6 cu.l
Vr= 24.97 cu.l
FB= 60.3
FL= 37.88hz
FH= 96.13hz

You should use the largest port area that you can while still being able to fit the port length in the box. There are several calculators available online to help with the box tuning, to find port length for the port area you would like to use. For my own project I am trying to use a port area half of the SD of the subwoofers. If you haven't already checked it out, there is some great info and projects on this website.

The Subwoofer DIY Page - 4th Order Bandpass Systems

Hope this helps. Brian Steele posts here all the time. He may be able to help better than I can. I still learning.

Regards,
Matt
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Old 26th January 2016, 03:13 AM   #5
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The three main issues of the design are likely going to be : (1)coming up with a box with the required volume that can fit the driver while allowing it to be removable, (2) tuning it to the correct frequency (the port length calculations are an estimate an the port will likely have to be trimmed back a bit to achieve the target FB, and (3) dealing with the out of band noise.
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Old 26th January 2016, 05:36 AM   #6
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3) I am using active dsp. Does this help with out of band noise? Reticulated foam in the port?

2) I still don't know what some of the parameter abbreviations mean. Ported enclosures is all new to me. The whole concept still hasn't 'clicked' I don't totally get what is going on with the port.

1) I can get pretty crafty with building. Once I know what constraints I'm working with.

Last edited by Mindsource; 26th January 2016 at 05:50 AM.
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Old 26th January 2016, 09:38 AM   #7
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FWIW, I find these applets is a good way to 'wrap your mind' around how a vented cab works. Scroll down to them and wouldn't hurt to read the article also : Welcome Secrets of Home Theater and High Fidelity

GM
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Last edited by GM; 26th January 2016 at 09:41 AM.
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Old 26th January 2016, 09:46 AM   #8
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Quote:
Originally Posted by Mindsource View Post
3) I am using active dsp. Does this help with out of band noise? Reticulated foam in the port?
FYI, to get good vent performance from a BP 'sub' often requires a large, long vent, so using a passive radiator [PR] with an effective piston area at least 2.5x the woofer's 'Sd' spec is a good plan.

GM
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Old 26th January 2016, 03:16 PM   #9
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Quote:
Originally Posted by GM View Post
FWIW, I find these applets is a good way to 'wrap your mind' around how a vented cab works. Scroll down to them and wouldn't hurt to read the article also : Welcome Secrets of Home Theater and High Fidelity

GM
Good stuff GM. A book that I have found to be very helpful to me is The Loudspeaker Design Cookbook. The material is presented in a way that was easy for me to understand. There are also several papers available online describing the different types of Bandpass enclosures with formulas to help design them. The more complicated Bandpass designs will need a program to sim. The sealed rear chamber Bandpass can be done using pen, paper and a calculator. Well I need to run, work is calling.

Regards,
Matt
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Old 26th January 2016, 07:38 PM   #10
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Default Dayton Audio SD270A-88 10" DVC Sub

Shawn,
This would be the limit for a
4th order bandpass
6th order bandpass

Obvious that a tuning of 12Hz (), on the 6.order, will give a very lengthly port. So I would go with a more manageable frequency, 15Hz or 16Hz and up, the extension being affected but the port being short. The 4.order looks like a clean alternative, not doing infra-sound.
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File Type: jpg 6th order bandpass.jpg (113.0 KB, 82 views)
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