1 ft3 vented at 25Hz, subsonic needed?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=48151
Printed Date: July 06, 2025 at 7:36 PM
Topic: 1 ft3 vented at 25Hz, subsonic needed?
Posted By: maxxx
Subject: 1 ft3 vented at 25Hz, subsonic needed?
Date Posted: January 19, 2005 at 10:06 PM
1 ft3 vented at 25Hz, subsonic needed?
I have a brahma 10 mkII in 1.05 ft3 (net) with a 3" round ABS port 26" long (+/-25Hz). Do I need a subsonic? At what frequency? I am running it off a zapco 3.0x c2k which has a 33Hz subsonic, will this actually work or will it hurt the response below 30Hz?
TIA
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destination moon
Replies:
Posted By: stevdart
Date Posted: January 19, 2005 at 11:05 PM
Yes, you should employ that subsonic filter. You don't want to hit below the Fs of 30 Hz at loud volumes. This is a DVC 2 ohm driver, so are you bridging to the amp at 4 ohms for a 300 watt output? Beautiful amp, BTW. But will it power a Brahma?
Posted By: DYohn
Date Posted: January 20, 2005 at 10:09 AM
Yes, that is a nice amp. Bridged into a 2-ohm load it will produce around 600 watts, so it'll handle any sub you want to throw at it. The 33Hz "sub sonic" is rather high, and yes since it is an 18db/octave (I believe) high-pass filter it will effectively cut all frequencies below 30Hz to near inaudibility. This is a class A/B amplifier and the crossover section is actually designed for highs/mids more than for subs. For vented enclosures, you do need to use a high-pass "sub-sonic" filter just below the tuning ffrequency to avoid damaging the woofer(s). If your enclosure is vented at 25Hx, then I'd use a sub-sonic at 20-25Hz. ------------- Support the12volt.com
Posted By: kfr01
Date Posted: January 20, 2005 at 11:39 AM
I like stevdart's point here. Nice amp. Possibly wrong for the sub. Brahma is a DVC 2-ohm sub. So he wires one at 1-ohm or 4-ohms. That amp shouldnt' be bridged to 1-ohm. At 4-ohms the very inefficient Brahma isn't getting a ton of power. Hey, this isn't something I personally would be too concerned with, as my desired volume level is very moderate, but I know many of you have different expectations. ------------- New Project: 2003 Pathfinder
Posted By: maxxx
Date Posted: January 20, 2005 at 9:38 PM
I am considering to run it at 1 ohm off of one of the 2 channels of the 3.0x (300W/ch@1ohm). Presently at 4ohm bridged.
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destination moon
Posted By: stevdart
Date Posted: January 20, 2005 at 10:34 PM
...and use the other channel for what? You know that the power output is the same either way. And that a 2 ohm load (4 ohm bridged) on the amp is fairly gentle, while a 1 ohm load makes it run hotter with higher distortion and might shorten it's life. Don't try to use that amp for more than it's made to be used (if you're considering trying to use the other channel for something else). Did you find out if a Brahma can get more than a tickle with 300 watts? Both are some of the best equipment made, but not made for each other in this case. You should be powering some awesome front end components with that amp at the rated 4 ohm, and have an amp more suitable for use with subs for the Brahma. I just can't imagine that you're going to get $1000 worth of subfrequency sound with that marriage.
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