Filby1
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Registered: 12th Dec 03
Location: Brighouse
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what do they do? should i have tham turned on and if so at what setting? this is on a MRD-M300 mono amp powering a Type R 12" alpine sub running at 360 wrms
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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lol. The MRD M300 is 300w RMS (in an ideal situation), as is the sub, where'd you get 360 from???
What box is the sub in, if its ported then have the subsonic on, if its sealed then you dont need it on.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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got a little bit of paper with the amp said 300wrms but tested to show 360
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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yeah my M300 has that too, but thats only at exactly 14.4v, the actual voltage in use will be around 13.2- 13.8 from experience and so actual output power will be lower.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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What do ya think to this amp?
http://www.caraudiodirect.co.uk/product_info.php?products_id=3149&cadid=c811d74973d9793fb432a2c5c38f0ed2
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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there very nice, a HUGE step up from an alpine.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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with a L7 15" in a 2cu.ft box
Hopfully
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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depends wat sound you want, id couple it with a 12" RE XXX myself.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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im not sure 12" subs go as deep as i want it ny type R dont seam to anyway
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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as i say depends on sub box etc.. If you want it to drop put your 12 in a ported box.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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to be honest the shitty JBL tube things sound deeper. than mine and there like only 100wrms
[Edited on 20-05-2005 by Filby1]
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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yeah and they are most likely ported...
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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so swap my sub box for a 1.0cu.ft ported box?
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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nope needs to be bigger youd have to see wat size port alpine reccomend ansd wat volume box.
Ask the ice dealer you got the sub from. Will make it a lot louder at tuned frequency but it wonk kick as well.
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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what do you mean wen you say tuned frequency
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Filby1
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Registered: 12th Dec 03
Location: Brighouse
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and would i be better with a normal port? or a letterbox vent?
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kev_corsa
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Registered: 7th Nov 02
Location: Newport, Uni in Bristol
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a subsonic filter is basically a high pass filter for very low frequencies. Basically, it's used for filtering out frequecies lower than what you can hear, therefore, reducing cone excursion and making the amp more efficient in amplifying signals within the auduable range.
Heres a diagram of the frequency response of a subsonic filter, may help you to understand it a bit better.
Id say its quite important to have on irrespective of the box your using, just my opinion though 
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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sorry mate but i have to disagree.
Subsonic filters use is almost solely to prevent over excursion in a ported enclosure.
You might not 'hear' the difference between subsonic on/off, but u can 'feel' it. Try it bass is much deeper and fuller with it off using a sealed box.
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kev_corsa
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Registered: 7th Nov 02
Location: Newport, Uni in Bristol
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From the manufacturer:
"Mode 3: Subsonic filter
3-1 Set to “ON” for most cases, especially when using vented box subwoofer designs.
3-2 Adjust to the desired cut-off frequency. Warning: Since it is possible to overlap the subsonic
and low-pass filters, you may create a condition where amp will produce little or no output. Make
sure that the subsonic filter frequency is significantly lower than the low-pass filter frequency,
unless you have a very specific performance goal in mind."
I agree that you may get the best use of the filter when using a ported enclosure, but I agree with Alpine that it should be on in most cases
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AdiSRI
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Registered: 1st May 02
Location: Berkshire
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Well your choice mate, i know a LOT of people who build ICE for a living and they dont use them unless the enclosure is vented or the sub is free air.
If the box is sealed it performs the same job as a subsonic filter anyway, air pressure stops over excursion.
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