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Old 28th April 2004, 11:30 PM   #11
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Default ah, the ACTUAL sensitivity

Sébastien (by the way notice I found the accent mark now), my mistake. I assumed you were looking at a printed sensitivity.

I think we are probably in agreement:
a) The 120W amp with a good woofer is enough for decently loud bass
b) However, it will not satisfy anyone who wants to shake the air three blocks away.

So, Stevena2006, how loud do you want to play?


P.S. Yes, the boost of the closed car is theoretically 12 dB/octave, which is approximately the opposite of a sealed boxes' 12 dB/octave theoretical rolloff. The Q of the box and resonances on the car can modify things, but I'd agree Sébastien's sub should be more or less flat. Why is your SPL meter only good down to 80 Hz by the way?
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Old 29th April 2004, 12:05 AM   #12
tool49 is offline tool49  Canada
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Hehe don't worry about the accent mark, I'm used to people scrapping my name. So far only Parts-Express got it right the first time. But thanks anyway. I completely agree with you on this:

Quote:
a) The 120W amp with a good woofer is enough for decently loud bass
b) However, it will not satisfy anyone who wants to shake the air three blocks away.
I also implicitely agree that the manufacturer quoted specs are often way off (sometimes they are pure rubbish, especially in the rated power capacity of the drivers). More often than not, I end up measuring the specs myself and scrapping the box that I made with the manufacturer specs.

I found it strange too that the theorical boost of my car is less than the typical 12 db/octave but after a lot testing (read many dozens of tests) , I always come up with a gain of about 10-11 db/octave from 65Hz down. Perhaps the seals on the windows and doors are not tight enough and this causes leakage and a slight loss? I don't know but it does not bother me too much. (I also noticed that this behaviour is more pronounced when the temperature outside goes below 30F, even if the interior is up to 77F, thus my tought of a bad seal)

My meter is a Galaxy Audio CM130 (cheapy). It is rated to have a good precision over the range of 125Hz to 8kHz. But when I bought it, the salesperson had the CM140 at twice the cost and that is rated for 31.5Hz to 8KHz. So while he demoed them both to me at the same time, I noticed that the CM 130 would respond quite accurately (within 0.5db) down to 70Hz after which the readout would completely off or start to oscillate badly. So I consider my meter to be good till approx 80Hz. That is the reason why I don't trust it too much under 80Hz.

I should soon build mine with a Panasonic electret mic but until then, I'll rely on the good ol' CM130. (damn lazyness)

On a side note, for Stevena2006, I often noticed that the common listener won't like a flat car stereo. They want a LOT of extra bass. If this is your case plan to add an EQ if your amp or head unit does not offer one. Be careful though as a 3db boost on the EQ on a certain frequency will require twice as much power from your amp to achieve the boost.

Hope this helps!
Sébastien
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Old 1st May 2004, 05:36 PM   #13
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Default Re: will amp drive sub?

Quote:
Originally posted by stevena2006
well i have a 250w sony xplod amp MS-502z i know that it is only 120w rms and i was thinkin of buying a 10 or 12 inch sub that is 150w rms would this amp drive this sub or would it barely beat at all?
Given the right enclosure, yes. I wont show the full potential of your sub, but it would power it adequately.
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