Subwoofer design question

Kepler · 2nd September 2005, 11:01 PM

I'm using winisd to size a box for a subwoofer.

I'm looking at two possibilities:

1. Flat spl/fr curve response from crossover down to ~21hz where it drops like a rock with cone excursion exceeded at ~18hz

2. spl/fr curve drops ~1.5db/10hz starting around 55hz down to ~25hz and then drops fast, cone excursion exceeded at ~22hz

The sub will be vented. Case number 2 has a higher max. spl than case 1. Something like 106 vs 101.

My biggest concern was if the fr curve is level all the way down to ~20hz, will it sound boomey when you factor in the room response below 45hz or so. I used the room mode spreadsheet from FRD, but I'm not sure how to interpret and apply the data to the sub design. From what I gather, there is a peak around 40hz, ?magnitude.

Any feedback is greatly appreciated, as I'm hoping to start on it this weekend.

thanks,
Brady

kornmong · 3rd September 2005, 03:07 AM

sorry ive got no answers for you but I have the same concern as you and did not know how to put it

ruerose · 3rd September 2005, 07:49 AM

Where in WinISD does it show cone excursion? I was looking for that feature but couldn't find it.

on topic, if you design your sub flat, with no major peaks in the slope, you can compensate for any room modes (boominess) with moving your sub to different spots of the room, or adjusting your seating position. If you have a really bad room, it will be difficult to design a sub to compensate for it.

Raoul · 3rd September 2005, 08:25 AM

Quote:

Where in WinISD does it show cone excursion? I was looking for that feature but couldn't find it.

Cone excursion is found in "transfer function magnitude" drop down menu. Look under the sub-heading "driver".

richie00boy · 3rd September 2005, 09:24 AM

Excursion is in WinISD Pro.

Is your box size the same in both cases? What is the tuning frequency?

Kepler · 3rd September 2005, 01:31 PM

No the box sizes are different. Case 2 has a smaller box size.

Case 1 tuning was around 20-21hz. I think case 2 was about the same, I'll check when I get some time a little later today to make sure.

thanks

ps The sub will be sitting in a corner next to a couch with the driver and vents facing out into the room. I don't have the option of moving it around the room at this point.

2nd September 2005, 11:01 PM	#1
Kepler diyAudio Member Join Date: Oct 2004	Subwoofer design question I'm using winisd to size a box for a subwoofer. I'm looking at two possibilities: 1. Flat spl/fr curve response from crossover down to ~21hz where it drops like a rock with cone excursion exceeded at ~18hz 2. spl/fr curve drops ~1.5db/10hz starting around 55hz down to ~25hz and then drops fast, cone excursion exceeded at ~22hz The sub will be vented. Case number 2 has a higher max. spl than case 1. Something like 106 vs 101. My biggest concern was if the fr curve is level all the way down to ~20hz, will it sound boomey when you factor in the room response below 45hz or so. I used the room mode spreadsheet from FRD, but I'm not sure how to interpret and apply the data to the sub design. From what I gather, there is a peak around 40hz, ?magnitude. Any feedback is greatly appreciated, as I'm hoping to start on it this weekend. thanks, Brady

3rd September 2005, 09:24 AM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Excursion is in WinISD Pro. Is your box size the same in both cases? What is the tuning frequency? __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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3rd September 2005, 03:07 AM	#2
kornmong diyAudio Member Join Date: May 2005 Location: Tasmania, launceston	sorry ive got no answers for you but I have the same concern as you and did not know how to put it

3rd September 2005, 07:49 AM	#3
ruerose diyAudio Member Join Date: Aug 2005	Where in WinISD does it show cone excursion? I was looking for that feature but couldn't find it. on topic, if you design your sub flat, with no major peaks in the slope, you can compensate for any room modes (boominess) with moving your sub to different spots of the room, or adjusting your seating position. If you have a really bad room, it will be difficult to design a sub to compensate for it.

3rd September 2005, 01:31 PM	#6
Kepler diyAudio Member Join Date: Oct 2004	No the box sizes are different. Case 2 has a smaller box size. Case 1 tuning was around 20-21hz. I think case 2 was about the same, I'll check when I get some time a little later today to make sure. thanks ps The sub will be sitting in a corner next to a couch with the driver and vents facing out into the room. I don't have the option of moving it around the room at this point.

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