posted
I began car stereo back in 1996 and saw as we went from big long high power Class AB amps (PPI A1200's, PC2350's Kicker ZR1000's, Orion)to big High Power High Current Class D amplifiers (mmats xfire, etc). I have tried all these amps side by side and have noticed that there is a different characteristic sound, most notably more TIGHT and snappy when running say 600 watts in the form of high voltage versus 600 watts in the form of high current, even when not exceeding 50% of a given amplifiers maximum head room. I am talking about Class A/B versus Class A/B also! Even a 300 WRMS PPI PC275 bridged mono into 4 0hms vrs a Soundstream Pure class a 3.0 or Reference 300 A/B amp bridged mono into 1 ohm that it wants. In that case the wattage would consist in proportion of more amps than volts.
Can any of you guys attest to the same phenomenon? Maybe its how these amps handle impedance rise, or simply the fact that theres more distortion with current heavy outputting amps. I do understand that the Class D should sound bit different. But I seem to see a diffenrence period in wattage by current versus wattage by voltage, maybe voice coil control characteristics are different?
posted
High current and high voltage have more to do with the type of transistors they use. such as the irfz44 are 60v 40 amp transistors, they are actually used in ppi amps(although as we all know they are not really what is considered to be a high current amp). then you have the irf540 transistors which are the most popular transistors used in amps which are 100v and 28 amp, these are the typical high voltage transistors, although some use them in "high current amps."
Clearing that up, the lower the impedence you go, the worse the slew factor becomes as well as the lower the damping factor is. slew is basically the amps ability to switch to different freqs and damping is the ability to control a woofer when the signal disappears. many sq people fear the high current amps on their mids, running impedence transformers and what not to them because of this.
As being in the US we demand smaller size, more powerful, cheaper... basically big better now mentality and that is usually what is sold to us. for this reason you will also see that stuff on ebay like the super high end quality amplifiers have a high price tag per msrp ratio than the normal xfire 1000d type amp. basically car audio used to be a subculture and to some extint it still is, but it is way bigger than it ever has been before, therefore companys may rush or find the cheap way to get what US(the car audio market) want. which is for the most part, to be heard and noticed a mile away.
posted
I agree with jarfunkz , though I'd like to add my 2 cents (CDN) to this post. My understanding of Voltage driven versus Current driven amplifiers is the way they are designed. In Voltage driven type, Voltage is applied to the signal, then "processed" and current(a by product of voltage and resistance) is applied at the output stage. Current driven works in the reverse way . One is not "better" but as SPL Neon noted , sounds different. I have always tried to show my customers how to blend Voltage driven amplifiers for bass/mid/treble, and Current driven for sub-bass . This combo works awesome no matter what speakers or HU's are used.
-------------------- E.C. Wuz here Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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posted
Good point, I suppose it all depends on what perspective you look at it from, what we tend to call high current amps is just because they drive loads under 4 ohms, that seems to be the most common terminology, even though the voltage is always higher than the amperage untill the below 1 ohm threshold is reached. If my D200HC was driving its 1 ohm load and I am getting around 1600 watts then i should see 40 amps at 40 volts...thats why we need THICK woofer cable when driving high current situations. Thats alot of current its pretty amazing that amplifiers can drive that and lower, the high current setups must be harder on the individual componenets you would think also.
Posts: 841 | From: Pennsylvania | Registered: Feb 2002
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posted
High current amplifier simply means it was designed to drive loads lower than the standard 4 ohm. Nonetheless, an amplifier is still considered a constant voltage device. Which means voltage is constant regardless of load. You ALWAYS apply a voltage to a load, not a current to a load.
The only difference is the new age of regulated amplifiers which is usually a "high current" and a "high voltage" amplifier in one. It switches to different rail voltages depending on the load.
I remember doing a test with a dvc woofer. I measured voltage, current and Bl for the coils in series and in parallel. Matching the power output so that I got 1 watt into 8 ohms as well as 2 ohms yielded the same Bl, same loudness, same power output. In terms of designing a woofer, 1 ohm, 4 ohm, it's all the same. The only real difference is that Damping Factor goes down due to the reduced impedance.
The problem here is the class D amplifier.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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What do you mean with: The problem here is the class D amplifier.
This is a PWM variation for the output stage.. and their efficienfy are very good because output transistor are always used in total saturation.. so less power lost in heat.. I know you understand that..
So.. why do you think that class D have problem..
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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posted
I don't have a personal problem with class D amps. I've played with them briefly and even built one using the LM4651/52 chipset. They have amazing effeciency, greatly reducing overall cost. Heatsinking is where you'll save most of your money.
Let me be more specific when I say the problem is the amp. Trying to compare the sound quality of an overengineered AB amp versus an inexpensive class D amp is the problem. One amp has <.1% THD at full power while the other is nearly 10%. It's not simply a matter of high current versus high voltage. It's a question of analog amplification versus PWM and filters to make the signal analog.
I will admit, many class D amps do sound perfectly okay for my standards if the crossover frequency is low enough.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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posted
Love the high voltage stuff...that's why I have so many Linear Power amps in the car- with the daddy of the high voltage sub amp the 4.1hvs.
-------------------- Team Image Dynamics/Zapco/Werewolf/JK Lab Team Kinetik Sick Bastard Audio SQ Who feels it knows it Posts: 7876 | From: Charlotte,NC USA | Registered: May 1999
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I think the scenario is different for woofers than midrange/tweeters. Woofers do draw full power from an amplifier, so regardless on how you get 1000w to the woofer, 4 ohm or 1 ohm, sonically it should be equal, 1000w = 1000w,....
But midrange and especially tweeters don't draw as much power from the amplifier like the woofers do. Do you know any dome tweeters that really dissipate a few hundreds watts ? I can drive a home amplifier bridged with a 1 ohm tweeter array, but this amplifier is not able to drive woofers less than 8 ohms.
Since we tend to overdrive our music and push the amplifier to clipping, it would be more beneficial to drive tweeters with high voltage rails to raise clipping headroom. Example, a cheap amplifier bridged that causes a 4 ohm tweeter to see 80v swing will have more clipping headroom than a monster amplifier that drives most of it's power into 1 ohms with 30 volt swings.
But on the other hand, some people don't like the extra headroom because some say it causes their tweeters to sound harsh... well, that is a tweeter problem or crossover problem. It's possible that your tweeters are to whimpy to handle the headroom and you are overdriving the tweeter on impulses.
The trend in car audio is to make the tweeters smaller, sacrificing it's ability to perform the traditional job of real tweeter duty.
The newer generation of system builders need to focus more on midrange/tweeter than just woofers.
103db sensitivity, I drive these with a 600w bridged amplifier. My goal is to line source these for a home project to achieve >140db just running tweeters. If I can't, oh well, one driver sound awesome, yet alone eight.
I'll be driving these with 180v swings, a DIY home amplifier project in the works.
/hehe
Posts: 47 | From: California | Registered: Feb 2003
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-------------------- Team Image Dynamics/Zapco/Werewolf/JK Lab Team Kinetik Sick Bastard Audio SQ Who feels it knows it Posts: 7876 | From: Charlotte,NC USA | Registered: May 1999
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there is a reason why a voltage drop happens when the load rises and that is there is a weak link in the amp
causing a voltage drop weather it be the power supply or even the output stage
there are amps out there that maintain 61 volts from 8 ohms too 1 ohm while the current exponentially increases
but once you go below what the amp is rated for then of course the voltage is going too drop because of the weak link in that unit acting like a resistor itself
i have built many amps in myu short time ranging from a max current and voltage from 16 ohms too .125 ohms w/o a voltage drop untill i went below what i designed it for
and at that point my current draw still increases but my voltage drops and stays efficient too a point and that point is when it looses total damping control
a combination of high current and voltage is the best route in any application for clarity and just hardcore pounding
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