Need help choosing an amp:

[R055]

Hey guys, I have 2 speakers inside my boat and 2 single big air kicker bullets on the tower. I need an amp. The speakers inside the boat are 50rms/120 peak and the kickers on the tower are 65rms/195 peak. What amp would you guys recommend for that setup? Also it doesn't have to be a marine amp, the amp will be mounted in a dry compartment. I believe my head unit outputs 22rms/50 peak.

 

[Scott Danforth]

it depends on how you want to listen to the music. you may need to resize everything (including your battery) to get the sound level you want.

 

[R055]

it depends on how you want to listen to the music. you may need to resize everything (including your battery) to get the sound level you want.

I want an amp that can max out the speakers but not so strong that it will blow them or anything like that.
How is this one?
https://www.amazon.com/Pyle-PLMRMP3B...s=800+watt+amp

I just want the music to be audible while underway in the boat. I'm not looking for sound that can be heard from the shoreline while wakeboarding.

 

[gm280]

Well let me explain something for you to pound first. A 12 volt (actually probably 13.8 volt) input supply voltage fused at 10 amps can not out put 800 watts in any planet. I don't know how they can call it an 800 watt amp when the input wattage is maxed out about 120 to 138 watts. Wattage is current (amperage) times voltage. You can get more power out of anything then the power put in...period! Remember one thing when looking at any electronic power amp. output wattage can never ever equal more then input wattage. It just can't happen. If that were possible, we wouldn't have any energy issues worldwide. So that statement is extremely questionable on the surface. The THD(Total Harmonic Distortion) seems good if verified at 0.05%, and so does the weighted S/N (Signal to Noise) at 95DB. But wattage, not even close. And all that for just $44 dollars should be the tip off as well. JMHO

For that amplifier to provide 800 watts output power, the input current would have to be at the absolute least, 58 amps at 13.8 VDC!. And that isn't what it is fused at.

 

[frantically relaxing]

Stereo amplifiers feed the speakers volts, which is expressed as watts. And as voltage doubles, wattages quadruples. This is very different from factoring the ratios of watts/amps/volts of AC or DC electric output. Music amps are essentially step-up voltage transformers...

From some quick searching: a 25 watt RMS rated amp will typically peak at 20 volts, which equates to 50 watts peak. A 100 watt rated amp will peak at 40 volts/200 watts peak. So doubling volts to 80 will equal 800 watts peak. I'm not sure about this, but most home stereo amplifer's ratings are based on RMS output, and most 12 volt audio system's ratings are based on peak output...

So how much 12 volt battery power is needed to sustain an average 400 watts output of a 800 watt power amp? I'll let someone else figure that out

 

[thumpar]

Ohms law. Volts times amps is watts. The ohm rating of the speakers will also dictate how much power the amp is puting out. A 4 ohm speaker will try to pull 2X what an 8 ohm speaker will. Home systems are only rated at RMS for a quality unit just like car amps. My old Sony was rated at 120 per channel but my Harmon rated at 40 per channel blows it away. I used to run Soundstream (when they were good) and Zapco amps. For your setup I would look for an amp that has separate front and back inputs so that you can control the levels or just get 2 smaller amps that are more fit for each pair of speaker power. I have a Crossfire in my Crownline and really like it.

 

[gm280]

You can try to figure out wattage any way you like. But mathematics in electronics doesn't lie. Wattage is wattage and amps times voltage is wattage...period! You can go from there. You will never ever produce more output wattage then the available input wattage regardless how you segment up the amps and volts. It is simple Ohms Law!

 

[Scott Danforth]

I used to try to run a large stereo.....thinking that my stereo was great, then a friend of mine showed me his Bob Carver lightstar setups. to make good crisp sound that is loud takes a lot of power and a really really really good set of amps, and to top that off, properly built speakers. I think he had $30k in the stereo

Back to RO55 and his system. RO55, you will find that adding an amplifier will tax your existing speakers and make them sound crappy as the distortion will be there. so you upgrade the speakers to find the distortion of your head unit. next thing you will find is that you are running out of battery... prior to throwing components at the boat, take a look at some audio shops that deal in the marine market. nothing worse than listening to distortion. as you get into driving power, you may also want to look into at least passive crossovers.

The Pyle amp you shown will be a disappointment. They are inexpensive for a reason. I have a small bluetooth Pyle unit on my tiki bar near my pool - it works ok enough for the waterproof speakers I have however the sound quality only becomes better after the 10th margarita. There is way too much distortion to enjoy it any more than background music.

back to the battery issue. nothing kills a battery faster than an amp. there is a reason most people who install large stereos have multiple house batteries on their boat, as well as a really large alternator to charge everything back up.

 

[R055]

Alright thanks for the input guys, anyone want to suggest an amp other than the one I posted? Also for battery, I'm getting a smaller 12 volt battery as a secondary battery that I'll use when my boat engine isn't running.

But I want just enough loudness to hear the sound decently when underway, not trying to get into the 12 speaker 2 subs 2000watt amp expensive wakeboard boat speaker system territory or anything like that.

 

[R055]

I used to try to run a large stereo.....thinking that my stereo was great, then a friend of mine showed me his Bob Carver lightstar setups. to make good crisp sound that is loud takes a lot of power and a really really really good set of amps, and to top that off, properly built speakers. I think he had $30k in the stereo

Back to RO55 and his system. RO55, you will find that adding an amplifier will tax your existing speakers and make them sound crappy as the distortion will be there. so you upgrade the speakers to find the distortion of your head unit. next thing you will find is that you are running out of battery... prior to throwing components at the boat, take a look at some audio shops that deal in the marine market. nothing worse than listening to distortion. as you get into driving power, you may also want to look into at least passive crossovers.

The Pyle amp you shown will be a disappointment. They are inexpensive for a reason. I have a small bluetooth Pyle unit on my tiki bar near my pool - it works ok enough for the waterproof speakers I have however the sound quality only becomes better after the 10th margarita. There is way too much distortion to enjoy it any more than background music.

back to the battery issue. nothing kills a battery faster than an amp. there is a reason most people who install large stereos have multiple house batteries on their boat, as well as a really large alternator to charge everything back up.

Also my speakers are all new so not looking to upgrade them, just want an amp that will give the speakers all the power they need to sound their full potential. This summer I was running the 2 stock speakers in the boat and no wakeboard tower and it's fine when the boat is standing or docked but can't here crap when the boat is underway. I'm hoping that will change with 4 new speakers and an amp that gives the speakers all the power they need.

 

[bruceb58]

Stereo amplifiers feed the speakers volts, which is expressed as watts. And as voltage doubles, wattages quadruples. This is very different from factoring the ratios of watts/amps/volts of AC or DC electric output. Music amps are essentially step-up voltage transformers...

Sorry...ohms law says otherwise.

 

[bruceb58]

This amp uses two 30A fuses in parallel and is similarly rated to the Pyle

https://www.amazon.com/dp/B00A02PG0C/ref=psdc_10980761_t1_B00G9RCYD4

Not sure what the deal is with the Pyle with the 10A fuse. Obviously, it is not a true 400W or 800W amp.

 

[R055]

Alright thanks for the help guys, I'll start looking for a 2 battery solution and amp although don't think I'll be able to test this year anymore because of the weather. Hope you all had a good boating season!
-Ross

 

[frantically relaxing]

Sorry...ohms law says otherwise.

You are right of course, my explanation was off base, I'm not an electric genius by any stretch and I wasn'tt sure how to explain what I'm trying to say. After a little research (thanks Joe Roberts) maybe this will make more sense...audio watts can't be judged as 'continuous' watts like a toaster or electric motor would use, because audio output voltage and wattage figures are based on peaks over time due to the fact music output is continuously changing... high watt peaks are very few and very short in time. Based on tests with actual music with a 100 watt amplifier, when run at 100 watts/40volts RMS (the maximum average of instantaneous power over time, and on the verge of clipping), the actual average electric output to the speakers was only 5.13 watts/6.4 volts...

The 100 watt surges do happen, and the amp will need to have the voltage available to reach them. But it seems to me a single battery will be able to handle a 100w power amp with little problem...

800 watts? I'm still thinking that's peak and not average...

 

[bruceb58]

the actual average electric output to the speakers was only 5.13 watts/6.4 volts...

Yep and that is why whenever some posts on here about needing a second battery, I usually tell them that the actual current that they will draw will be something a LOT less than the rated current that the amp could draw.

 

[thumpar]

100 watts would probably be just fine with one battery but there is no way you can can get more than around 200 watts peak with a 10 amp fuse and that is only because the amp will have capacitors in it to buffer otherwise it would pop the fuse. You need to keep in mind that the volts and watts are not a direct comparison. It will depend on the ohm rating of the speaker setup. I had a Soundstream amp that was true class A and only made maximum power at low ohms. It was 1/4 ohm stable. It blew up a JL Audio 12W6 which is rated for 600 watts. The amp was rated at 600 watts at 1/4 ohm. I ended up using the amp to run my mids/tweets at 4 ohms so it only put out 50 watts. RMS (root mean square) is not actually continuous watts, it is a rating of a wave. I took college level electronics in high school. We installed and fixed many amps.

 

[bruceb58]

RMS (root mean square) is not actually continuous watts, it is a rating of a wave. I took college level electronics in high school

RMS is basically just the average of a sine wave. If you sampled a sine wave and averaged the square of all the voltage points, you would get the RMS value. Not even sure what you mean by continuous watts.

You can do an RMS Calc of any signal but a sine wave is used just because you just multiply the peak voltage with a constant value.

 

[thumpar]

RMS is basically just the average of a sine wave. If you sampled a sine wave and averaged the square of all the voltage points, you would get the RMS value. Not even sure what you mean by continuous watts.

You can do an RMS Calc of any signal but a sine wave is used just because you just multiply the peak voltage with a constant value.

Some companies try to use continuous watts instead of RMS. People throw continuous watts around a lot too. When the cheap companies claim ridiculous "peak" and "continuous" watts I laugh.