Hi Inge!
You did a great job disguising your 15" monster as a piece of quaint furniture. No one would have a clue that this cute little cabinet can rattle your fillings loose! Good Job!
http://stevezeva.homestead.com/files/wooferfront_op_800x531.jpg
http://stevezeva.homestead.com/files/wooferback_op_800x531.jpg
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Thursday, September 20, 2007 11:23 AM
To: [log in to unmask]
Subject: [TN] NTC:subwoofer, pictures
Wife: on one condition: your wuffer or what you call it, must not look like an ugly loadspeaker!
Me: promis, sweetheart.
Sending pics to Steve for audiofil section of the wall.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Hfjord
Skickat: den 20 september 2007 17:51
Till: [log in to unmask]
Ämne: [TN] SV: [TN] NTC:subwoofer
Thanks Guy,
According to your information:
RIAA curve @ 20 Hz is 7,500 us
My power supply Ri= 0.1 Ohm
Backup caps on supply rails is 100,000 F
Tau = R (Ohm) x C (F) > 0.1 x 0.1 = 0.01 s which is 10,000 us
Not too bad! Near RIAA spec. Fine! I'm satisfied.
Thanks again. Didn't realize it was that easy.
/Inge
-----Ursprungligt meddelande-----
Från: Guy Ramsey [mailto:[log in to unmask]]
Skickat: den 20 september 2007 17:00
Till: 'Hfjord'
Ämne: RE: [TN] NTC:subwoofer
On the output? You mean on the power supply rails?
You can calculate how long it will take to discharge the caps if you know the output impedance of the amp and the speaker load. These act in series.
With the RC time constant.
http://en.wikipedia.org/wiki/RC_time_constant
Compare the output impedance of the power supply to the audio amp. How long it will take to charge the caps.
Then you need to decide what kind of sonic compromise you can tolerate base on the expected duty cycle imposed on the system by the music or sound track content.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Wednesday, September 19, 2007 4:57 PM
To: [log in to unmask]
Subject: [TN] NTC:subwoofer
Audio techies,
I've built a subwoofer with a 15" 400 Watt loadspeaker (4 Ohms). Bought a 200 Watt low frequency 12 V amplifier. For that one, I built a 12 VDC power supply with 15 A toroid, regulator, OP amplifier and a backup consisting of totally 100,000 uF on the output. What is your experience? Will these caps be enough to take the short power tops in Space War or the enormous sound effects in Matrix or Jurassic Park? Any thumb rules or maths?
/Inge
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