18" subs

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  • MTXMAN
    MTXMAN Posts: 682
    edited October 2003
    well either way he doesn't seem to have any clue wtf he's talking about. i always find it amusing to talk to these guys in real life ;D it's always good for a laugh to see how many technical and brand related questions that they can't answer ;D
    Hemi: (HEM -e) adj. Mopar in type, V8, hot tempered, native to the United States, carnivorous, eats primarily Mustangs, Camaros, and Corvettes. Also enjoys smoking a good import now and then to relax.
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  • PoweredByDodge
    PoweredByDodge Posts: 4,185
    edited October 2003
    "Ay Gotz No O-u-m-z _igga"

    thats my fav.
    The Artist formerly known as PoweredByDodge
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  • Nathan32387
    Nathan32387 Posts: 15
    edited October 2003
    what does damping factor and slew rate mean for amps, and how would i find out that info about an amp. And if the slew rate and damping factor are bad what does the amp sound like compared to a good amp?
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  • PoweredByDodge
    PoweredByDodge Posts: 4,185
    edited October 2003
    damping factor is a property indicative of the amplifier's ability to return the speaker to 'center' after bumping out... or bumping in.

    the speaker goes out - in - out - in - out - in... and the amp's ability to retain linearity and a smooth transition between those stages is an important thing.

    the slew rate is the rate at which the amp can increase or decrease its voltage output.


    **** damping factor and **** slew rate = **** amp.

    "****" however is a relative term.

    personally, anything over 20v/us slew rate and 200 damping factory is acceptable to me. some people may require even better numbers for their highs, but still retain 20/200 as the limit for their subs.

    you'll find that 20/200 is pretty much a common trait for mid-grade gear.

    orion / mtx / some hifonics and other brands all are at or kinda float around those numbers.

    better amps are going to look more like 35v/us - 500 damping factory. RF would be included in that range, and is one of the reasons RF sounds better than most other amps in its price range... however there is more than just those two factors to determining what amp is right for you. durability is critical.

    something like a zapco can have as high as a 1,000 damping facotor and a slew rate of 75 v/us ... USamps puts up even better numbers. but that depends on the model... you'll find that for example Zapco will have one amp with a damping factor of like 500 and another with 750... the same is true for every brand... you have to look model for model, and do your comparison that way.

    as far as what will one with a low damping factor and low slew rate sound like... well, an amp with 20v/us and 200 df will sound not nearly as good (given all other parameters are virtually equal) as an amp with a damping factory of 750 and a slew rate of 50v/us

    but to be simple -- anything under 15v/us and 150, you dont want to buy ... viper makes an amp that puts out damn near 3000 watts but has a slew rate of 5 v / us and a damping factor of 50... you might as well kick your subs in with your boot and call it a day. its sloppy - muddy - and i doubt it does well for the speaker(s).

    as far as any scientific proof, i've got none, but ask around and you'll get similar answers -- and when the guy from an amp company tells u though properties aren't important, dont believe him.

    ... oh - and how to get the info - it should be on the amp mfg's website - if its not, it should be in the amplifier's instruction manual (download the manual, read it, its in there usually), and if still not there, then call the company and ask a tech... if they give u a hard time, press them, demand it... and if they wont give it to you - dont buy their stuff.
    The Artist formerly known as PoweredByDodge
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  • MTXMAN
    MTXMAN Posts: 682
    edited October 2003
    if they say they don't have that information stay the hell away from they. avoid them like you would someone infested with the black plague
    Hemi: (HEM -e) adj. Mopar in type, V8, hot tempered, native to the United States, carnivorous, eats primarily Mustangs, Camaros, and Corvettes. Also enjoys smoking a good import now and then to relax.
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  • LittleCar_w/12s
    LittleCar_w/12s Posts: 568
    edited October 2003
    I'm a total Polk fan, but the only over-15 speaks i've seen put out good SQ and SPL are Cerwin Vegas, and the man had 4 of the 18's in a wall in a van... that's some loud ****. I wouldn't reccomend any other brand for over 15" and only vega, Polk and orion for 15's :rolleyes: in dhort. stay away from 18, unless ya got $$$$, lotsavit for good equipment.
    ___________________________
    Total cost of materials: Going up...
    Time spent: Countless Hours...
    Cranking the system, having it quiet outside the car, and sound that takes the rear-view off inside: PRICELESS

    For some things in life, you pay others to do it... For a masterpeice, do it yourself.
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  • MTXMAN
    MTXMAN Posts: 682
    edited October 2003
    The eclipse Titaniums are good large sized subs too... insanely priced but good
    Hemi: (HEM -e) adj. Mopar in type, V8, hot tempered, native to the United States, carnivorous, eats primarily Mustangs, Camaros, and Corvettes. Also enjoys smoking a good import now and then to relax.
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  • stormchaser
    stormchaser Posts: 1
    edited October 2003
    hey all i just got 2 new MM12's and i need good clean power that won't wimp out or need to b replaced next week
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  • sutko
    sutko Posts: 2
    edited December 2003
    Originally posted by PoweredByDodge
    damping factor is a property indicative of the amplifier's ability to return the speaker to 'center' after bumping out... or bumping in.

    the speaker goes out - in - out - in - out - in... and the amp's ability to retain linearity and a smooth transition between those stages is an important thing.
    Damping factor is an almost meaningless number. Damping factor is the ratio of the nominal impedence of the speaker in question to the output impedence of the amplifier. Basically, its:

    Damping factor= Z (Speaker Impedance) / Z (Output Impedance)

    The reason it's meaningless is that the DC resistance of the voice coil is so much greater than the output impedence of the amp that it doesn't really matter. At least not until the damping factor gets really low, like below 10, and the wire resistance is added in, then there begins to be a difference in frequency response between the two amps- and thus the boomy bass. Some tube amps can have damping factors that are fractions, yet sound good with certain speakers that are overdamped.

    Damping factor is semi-relevant for pro audio, where they are potentially running hundreds of feet of speaker wire into all sorts of different loads. Not important for most home and car installs however.
    the slew rate is the rate at which the amp can increase or decrease its voltage output.

    **** damping factor and **** slew rate = **** amp.

    "****" however is a relative term.

    You got the definition of slew rate right, but not the application. Slew rate is another term that is often completely misunderstood. Anybody who buys their amps based on which one has the highest slew rate or damping factor clearly doesn't understand what these terms mean or their relevance to audio.
    personally, anything over 20v/us slew rate and 200 damping factory is acceptable to me. some people may require even better numbers for their highs, but still retain 20/200 as the limit for their subs.

    you'll find that 20/200 is pretty much a common trait for mid-grade gear.
    Completely arbitrary numbers. Curious as to where you got them from? Training seminar? Streetcorner?

    Regarding slew rate. Not relevant for sub amps. If your amp is slew rate limited, it will affect the high frequency performance before low frequency performance is affected.

    Okay, let's look at your numbers. Take an amp that puts out 100 wpc at 4ohms for a set of components(6 ohm tweets). Assume a worst case scenario- where you need to put out the full output power at 20khz (unlikely based on any music. Almost guaranteed to fry a tweeter on most setups)

    The relevant equation is:
    dV = 177,600 sqrt(P Zl)

    dV=slew rate P=power Zl=impedence

    dV= 177,600 sqrt(100 6)
    dV= 177,600 (24.5)

    dV= 4,350,000 v/s

    or 4.3v/us

    And that is a worst case scenario. Again, slew rate is just not relevant for most solid state amps.
    snip some more rambling
    as far as what will one with a low damping factor and low slew rate sound like... well, an amp with 20v/us and 200 df will sound not nearly as good (given all other parameters are virtually equal) as an amp with a damping factory of 750 and a slew rate of 50v/us

    Not supported by fact. But if you can prove this claim in a listening test, Richard Clark has $10K for you.

    but to be simple -- anything under 15v/us and 150, you dont want to buy ... viper makes an amp that puts out damn near 3000 watts but has a slew rate of 5 v / us and a damping factor of 50... you might as well kick your subs in with your boot and call it a day. its sloppy - muddy - and i doubt it does well for the speaker(s).
    Damping factor is usually rated playing 50hz tone at 4 ohms. If this is the case (you'll have to email dei to find out) then the output impedence would be .075 ohms . Running that amp at 1 ohm will result in the df dropping to a quarter of the rated value. That would be a paltry 13.5 and probably even lower at resonance and once you add the wire resistance. Not what I would run, but the woofer is not going to be flopping around as you suggest.
    as far as any scientific proof, i've got none, but ask around and you'll get similar answers -- and when the guy from an amp company tells u though properties aren't important, dont believe him.
    You shouldn't punish them for telling the truth. The only companies that will push damping factor and slew rate are the ones who market their products based on those factors.
    ... oh - and how to get the info - it should be on the amp mfg's website - if its not, it should be in the amplifier's instruction manual (download the manual, read it, its in there usually), and if still not there, then call the company and ask a tech... if they give u a hard time, press them, demand it... and if they wont give it to you - dont buy their stuff. [/B]

    The company should give you these numbers but they shouldn't tell you that higher numbers mean better sound i.e. they shouldn't lie to you.

    People should realize that specs are not measurements, they are advertising. Companies place too much emphasis on "buzzword" figures such as THD, S/N ratio, stereo separation, slew rate and damping factor which aren't as significant as the product literature makes them seem, i.e. they don't guarantee how the product will perform. These numbers are pretty much good for spotting really deficient designs, and that's it. For choosing between competently designed amplifiers, they are oversimplified and practically useless.

    Also, getting rid of the last .001% of thd for the marketing dept. distracts engineers from working on features that really do improve the sound- such as flexible crossovers and improved power supplies and output stages.
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