I know what your saying, given a fixed load, increasing the voltage will increase the current. What I intend is rather then run lower voltage/high current into 4 ohms. I'd like to run higher voltage/lower current into 8 ohms. Wattage remains unchanged. Two of my four supplies are 32v which should be able to do 100w into 4 ohms (rear speakers). The other two need to be rewound to a higher voltage to supply the same 100w but into 8 ohms (door speakers). I have to try and calculate that. A pic of the supply is attached.
I brought up that example to try and help jwilhelm understand horsepower. In my example, it's a tie. How am I going nowhere by using an example to try and help someone, or even myself, understand something? Because the example wasn't electronic?
Anyways, to those trying to help, thank you. I appreciate it.
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All we are trying to explain is that an 8 ohm speaker isn't actually 8 ohms so theoretical power isn't 100% accurate here. Yes you can make a theoretical wattage but the same voltage with more VA behind it will usually sound richer. I was comparing horsepower to wattage numbers because at the end of the day who cares what the number is? The one that sounds better is the best choice.
I also understand horsepower completely. I've been building all types of custom vehicles for over 30 years both professionally and as an enthusiast. I deal with more than just the odd little car so I also understand torque. If you ever have the chance to check out an offshore marine race engine or top fuel dragster engine you will understand what I'm talking about. A conversation with some experienced custom engine builders might make you rethink things too. Spend a week with a pioneer of power like Keith Eickert at Onken Racing and you'd have a whole different outlook.
I also understand horsepower completely. I've been building all types of custom vehicles for over 30 years both professionally and as an enthusiast. I deal with more than just the odd little car so I also understand torque. If you ever have the chance to check out an offshore marine race engine or top fuel dragster engine you will understand what I'm talking about. A conversation with some experienced custom engine builders might make you rethink things too. Spend a week with a pioneer of power like Keith Eickert at Onken Racing and you'd have a whole different outlook.
Just a quick calculation shows 65W from a 32V supplies into 8 ohm.
That is 3dB less than 100W, and far more than most speakers can handle full-range (you will reach mechanical limits on most 5-7" speakers with about 30W).
It's also very loud. Louder than you need for an average living room, let alone a car.
I wouldn't sweat it, but you're welcome to. I just don't think you will gain any advantage from doing so.
That is 3dB less than 100W, and far more than most speakers can handle full-range (you will reach mechanical limits on most 5-7" speakers with about 30W).
It's also very loud. Louder than you need for an average living room, let alone a car.
I wouldn't sweat it, but you're welcome to. I just don't think you will gain any advantage from doing so.
I don't have an outlook on racing engines. Nor am I biased one way or another. I have an appreciation for them and their builders. I build engines for fun and don't hit numbers anywhere near top fuel dragsters. The most torque I've driven was a 400sbc I stuck in a Monza. The fastest car I've driven was my boosted Miata. Much less torque, but much more horsepower. Say amps is torque. Could you determine the output power level of an amplifier using only one variable of a power equation? Nope. Same goes for engines. You need to know the horsepower output not just the torque. For all you know a 500ftlbs rating was at 100rpm. That's not even 10hp. You need to know how much torque is produced and how fast it can produce it aka. horsepower. Then the transmission comes into play. It's like an impedance matching transformer. It shifts the torque/rpm (amps/volts) up or down to another level, but the power remains constant. That 10hp is still 10hp.
Correct me if I'm wrong. I'm not trying to argue. I'm trying to understand why you feel watts (or horsepower) isn't the determining factor in output power.
He's running these to door speakers so they will likely be running high pass from a crossover. In my experience a 100 watt amp does a good job at that. It really sharpens the highs.
Fair point, I run my door speakers full range and traffic/road/wind noise is a bigger issue than output power. If 3dB would make a difference (it's subjectively about 20% louder) then it would make sense. I still don't see the point, because once you add a subwoofer the major consumer of amplifier power, i.e. bass, no longer needs to be handled by the amp, so it's an even stronger case against any changes.
I'm not saying the amperage is the number to strive for, the VA is. They both go together. Let's skip the engine analogies. I deal with enough apprentices every day.
I agree fully about background noise. There's a lot more gained by lowering the noise floor. That's always a spot for improvement in a vehicle.
Car speakers are pretty inefficient but my fronts are 8" with a 90db rating. I tried many 4x50w and 4x75w mobile amps and they begin distorting fairly quickly on the front speakers. Their power rating is at 4 ohms so I'm lucky if I'm getting 25~35 watts on the fronts. Also, the front speakers are mounted low in the door so they are poorly aimed and a lot of the sound is lost. I had to pad the pillar tweeters to match. The rears are 4 ohm 6x9s and they are plenty loud with 50w on them. Reflecting off the rear window and being 4 ohms give them two advantages over the fronts. Going from 25~35w to 100w up front will make a significant improvement. I tried a 2x 100w receiver on them for the hell of it and it was a perfect match. I don't always play my music that loud but every once and awhile I play a good song and want concert-level sound.
Besides, the easy way is boring. Sure, I could buy a 4x200w amp (4x100 into 8 ohm?) just to use 300w of it and have a 30lb surfboard in my trunk. I'll wind up with a better quality amplifier the route I'm going, as soon as I figure out the details.
Hello
greetings maybe of some help
That's helps a lot. I looked everywhere for a chart like that.
Looks like I'll need about +/-52v.
Correct. I have the fronts around 80-100hz 12db/oct. Being 8" they handle a bit lower xover point without the cones breaking up. Try 100w on a 6.5" at 80hz. Not happening. My subs are two 8" with 500w to them. They can't take much more then that which is fine. 8" subs usually play well with midbass but the box is tuned to 34hz which hurts that a little. Which is where the 8" doors shine. Toms, snares, slap-bass sound great out of them. Ever feel a cello? Love it. It's like I'm sitting next to the musician. I needed the home receiver to get that though. The JL 300/4 or the Memphis 4.75 couldn't do that into 8 ohms. My new DSP just died right after I finished adjusting the delays. For 10 minutes I had the most amazing image I've ever heard in a car. Almost brought tears to my eyes.
Sorry I meant Prms not Vrms. Your looking in the same spot I am. My supply is a +/- 32v 180w unregulated SMPS. If I wind for +/-52v I might get +/-42v under load. This supply will be the limiting factor but I am running one supply per channel. The supplies for the rears will be left at +/-32v but use the same amplifier modules. Hopefully my amps show up soon. The first set made it to Chicago but were mailed back to China. Not sure why.
10 volt drop under load is pretty high. I'm not a transformer guru by any means but I think that much voltage drop means the windings aren't neat enough and you're getting a lot of stray/waste magnetism. In my home amp toroidals I droop approximatly 2 volts. There are some expert transformer designers here. Hopefully they'll add some input if I'm wrong.
Where did my post go?
Anyways. I wish it was as low as 2v. I just tested a Jenson amp here with about a 100v load and the voltage drops from 58v to 52v. Gets in the 40s if I play it loudly into my test speakers.
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Why bother calculating.
Fit the 8ohms speaker/s and listen.
8ohms speaker will not damage a 4ohms capable amplifier
And
the amplifier will perform better into the higher load impedance.
And
you may find that the 8ohms speaker is more sensitive/efficient and you get more sound output at the same source volume setting.
Fit the 8ohms speaker/s and listen.
8ohms speaker will not damage a 4ohms capable amplifier
And
the amplifier will perform better into the higher load impedance.
And
you may find that the 8ohms speaker is more sensitive/efficient and you get more sound output at the same source volume setting.
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