Newbi: Box Volume and Port Length - diyAudio
 Newbi: Box Volume and Port Length
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 10th April 2005, 07:29 AM #1 diyAudio Member   Join Date: Apr 2005 Location: NH Newbi: Box Volume and Port Length Hello everyone. Great forum here. I have finally decided to build my our subwoofer box. My home theatre / stereo system does not have one. I will be using a 10" sub. Can someone calculate the desired volume, port length and diameter? I have tried some of the "online" calculators and I get screwy numbers. Here are the specs: 10" diameter Fs = 35 Vas = 0.07363 Qes = 0.39 Qms = 11.3 Xmax = 0.0051 Qts = 0.377 __________________ Audio DIY Page FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.
 10th April 2005, 07:34 AM #2 diyAudio Member   Join Date: Nov 2004 Location: Québec, Québec Can you give the units for the Vas and Xmax measurements please? It's cu.ft and inches or something else? __________________ DIYaudio for President !
diyAudio Member

Join Date: Jun 2002
Location: USA, MN
Re: Newbi: Box Volume and Port Length

Quote:
 Originally posted by 69stingray 10" diameter Vas = 0.07363 Xmax = 0.0051
I am assuming that Vas is in meters^3 and Xmax is in meters
Try the online calculators again with Vas=73.63 Liters and Xmax=5.1mm
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. —Aldous Huxley

 10th April 2005, 04:31 PM #4 diyAudio Member   Join Date: Apr 2005 Location: NH Thanks Ron E., that is what I figured out around midnight last night. They are in m^3 and meter. I retried the online calculators this morning and came up with the following: Inside volume: 2,936 in^3 Port Diameter: 3 3/4" Port Length: 11 1/3" Does this at least sound right? __________________ Audio DIY Page FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.
 10th April 2005, 11:07 PM #5 diyAudio Member   Join Date: Nov 2004 Location: Québec, Québec The data the online calculator calculated is ok. It won't be a strong subwoofer, not much output under 35 Hz. If I was you, I would use a 30W amplifier on it, and put the driver in a 100 liter internal box with one 3 inch diameter port 11 1/4" inches long for good output down to 18 Hz. Good luck! __________________ DIYaudio for President !
 12th April 2005, 06:49 AM #6 diyAudio Member   Join Date: Apr 2005 Location: NH Thank you simon5- For my own education, how did you come up with those numbers? The volume is considerably higher then the online calculators. In regards to amps, I was thinking about using Keiga KG-3100, which is 50W. What other options are there? __________________ Audio DIY Page FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.
 12th April 2005, 01:27 PM #7 diyAudio Member   Join Date: Nov 2004 Location: Québec, Québec I found these numbers with slight trial and errors method in WinISD Pro, not the online form of it. I try to match a theorical room gain curve to have a nice and flat response down very low in frequency. To compare the two enclosures easily, you can look at : http://www.linearteam.dk/default.aspx?pageid=isdonline Enter Vas (in liters), Qts and Fs. Enter Vb = 48.12 liters for your idea, then enter Fb = 35.3 Hz (11 3/4" x 3 3/4" diameter pipe). Click on Draw it, you'll see your curve. Then to see my curve, enter Vb = 100 liters and Fb = 20 Hz (11 1/4" x 3" diameter pipe). You'll see that you have better output down low. You can use your Keiga with no problems especially if it's rated at 50W RMS continuous, just don't use too much power when playing movies with deep bass like LoTR. If it's a linear volume knob, stay under 1/2 if possible hehe! If not possible, you can go higher, then lower the volume when you hear too much distortion for your taste. If the rating on the Keiga is a bit too much optimistic, you can probably use the full power output. But then, as you can see, you lose some output in the 30-40 Hz region, so it depends on how you like your sound. __________________ DIYaudio for President !
 14th April 2005, 03:26 PM #8 diyAudio Member   Join Date: Apr 2005 Location: NH Thanks simon5, I will play with those numbers. I do have an idea - I am actually using two 4-ohm woofer wired in series to get 8 ohms. I was just going to make one box with a divider for two equal volumes. Can I have two different volumes? One volume tuned for a lower freq. and the second volume tuned for a slightly higher freq? We I run into out-of-phase problems or cancellations? __________________ Audio DIY Page FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.
 14th April 2005, 06:26 PM #9 diyAudio Member   Join Date: Nov 2004 Location: Québec, Québec You can do that, but it's hard to make it sound good I think. You may find that the higher tuned subwoofer have a bad transient response. You better tune them both at the same frequency, like a single 200 liters box with 2 subwoofers. You could go with a single vented subwoofer and a single sealed subwoofer, probably better... but I prefer my 200 liters idea! __________________ DIYaudio for President !
diyAudio Member

Join Date: Apr 2005
Location: NH
OK, I have completed my box design, I think.

I went forward with the 200 liter internal volume. I am wiring two (2) 4-ohm subs in series and using 2 ports.

The internal dimensions are 18-5/16 x 18-5/16 x 18-6/16. The brace has five (5) 8"-diameter holes. I plan on using 3/4" MDF for everything.

The tuning freq. works out to be approx. 29.5 Hz

QUESTIONS:
1. What does everyone think?

2. I will be using a 45W amp. from Parts Express
http://www.partsexpress.com/pe/showd...number=300-784

3. What about stuffing? I have read some are in favor and some are not.

4. A guy at work suggested that I mount one sub facing forward and the other sub facing up. What do you think? It will be positioned in the corner of the room BEHIND the TV and the rest of the speakers.
Attached Images
 sub_design.jpg (54.5 KB, 118 views)
__________________
Audio DIY Page
FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post jwhit67 Multi-Way 1 6th March 2008 12:29 PM Bobhof Multi-Way 3 2nd May 2006 06:32 PM busterno1 Multi-Way 5 27th October 2003 08:05 PM dave k Multi-Way 13 13th July 2003 02:32 PM

 New To Site? Need Help?

All times are GMT. The time now is 03:59 AM.