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Old 18th December 2008, 12:18 AM   #1
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Default Sub to Amp power ratio

Sub to Amp power ratio

Hey guys was wondering if you could advise a bit of a beginner.
I have a 1000Watt RMS sub and a 1500Watt RMS sub and am looking for monoblock type D Amps to power them. What sort of RMS power would you suggest I get for each? I don't want to throw money away buying an unnecissarily huge amp yet I also don't want to damage the speakers by getting something too small!! Any advice appreciated......
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Old 18th December 2008, 01:56 AM   #2
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First off what kind of subs are they. also what size are they. Sometimes if your running 2 differnt types of subs one might play luder then the other or what they call fighting eachother and might sound like *** also 2 different amps on two subs if they arent the same amp u also might run into a problem there also IMHO
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Old 24th December 2008, 10:06 AM   #3
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You won't fry your speakers with a small amp as long as you don't play your music heavily distorted, which burns the voice coil. RMS watts now becomes MAX watts as the sinewaves flatten into square waves at full power, and the constant high MAX wattage (now over the RMS of the speaker) smokes the speaker coil.

Simple, turn the volume down when the music sounds like $***!

The myth of a big amp is safer is complete BS. We have all heard that one before. Actually, It's better to have a smaller amp than the rating of your sub if you want them to last.

It's a compromise between speaker loudness and reliability. It's hard to have both. If you have each sub getting 800W or less you will be fine and have longer lasting speakers. I don't trust RMS ratings anyway after frying a few 12's myself in the past. Even 300WRMS per speaker is a LOT.

Just get amps big enough to be loud enough and cost-effective for you, but small enough not to destroy your speakers.
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Old 26th December 2008, 11:00 PM   #4
mandude is offline mandude  United States
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Well, if you end up running your amp at 100% all the time, won't you shorten it's lifespan? If your amp/sub ratio is not balanced, and you are running your amp as hard as you can, the amp will be running really hot, all the internal components will be really hot, and you can fry the amp before it's useful life is up.
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Old 29th December 2008, 04:52 PM   #5
Clipped is offline Clipped  Thailand
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Default Re: Sub to Amp power ratio

Quote:
Originally posted by DanSR20DET
Sub to Amp power ratio

Hey guys was wondering if you could advise a bit of a beginner.
I have a 1000Watt RMS sub and a 1500Watt RMS sub and am looking for monoblock type D Amps to power them. What sort of RMS power would you suggest I get for each? I don't want to throw money away buying an unnecissarily huge amp yet I also don't want to damage the speakers by getting something too small!! Any advice appreciated......
need to know type of sub and number of spiders along with voice coil diameter.
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Old 3rd January 2009, 11:57 AM   #6
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You wont fry any speakers with small amp as long as you dont clip it.

It's the clipping of the small amp that produces excessive harmonics that actually fry the tweeter, I've experienced this myself, But it will never fry a sub.

This are the facts that I know:

- small amps will not fry a big sub even when the music is being clipped,( LF test tone is another matter). But it will fry a tweeter due to the harmonics.

- Big amps will fry subs clipped or not, If the power being applied is way over the rating of the sub. Sometimes even less. But subs will never fry with smaller amps even when the amps is being clipped.
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Old 3rd January 2009, 12:53 PM   #7
AndrewT is online now AndrewT  Scotland
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What type of speaker are you needing to power?
Does it require any equalisation to bring up the bass response?
i.e. does it use a linkwitz transform?

Next question.
What is the normal volume you require from your speaker?
How much power is required to produce that volume?
How much overhead do you want to ensure that the signal is rarely/never clipped when playing highly dynamic music/audio?

If you want 96dB average at your seat and leave 20dB transient overhead then the speaker must produce peak SPL of 110dB @ ~1m when only one driver is used. For stereo that becomes 107dB @1m when two speakers are used.

If your speakers are 90dB/W/m then you need a transient peak power of +17dbWper channel i.e. 50W/channel.
If the linkwitz transform uses +10dB of equalisation then the amps must deliver 500W/channel to achieve that same average 96dB at the seat.
If the transform has +18dB of equalisation then the power required jumps to 3.155kW/channel.

You must know what the system is doing and what it needs to get to your targets before you can start asking any sensible questions.

Asking about sub to amp power ratio is nothing other than nonsense.
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Old 3rd January 2009, 01:04 PM   #8
AndrewT is online now AndrewT  Scotland
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I would set my targets as follows.
average SPL at the seat <=90dB
transform equalisation <=+10dB
speaker sensitivity >=86dB/W/m
transient overhead +20dB.
power /channel to meet these requirements ~ 1.2kW/channel, if using a sealed box speaker that can take a take a transient peak of 1200W and produce 127dB without power compression.

If I were using a ported driver or horn loaded driver that does not require any linkwitz transform then the power required drops to just 120W/channel.

If the drivers' sensitivities were increased to 96dB/W/m then only 12W/channel is required.

My car insurance probably only covers this last option and even then they'll charge a premium for the speakers that could be damaged or stolen.
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Old 3rd January 2009, 02:14 PM   #9
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My short answer would be:

For 10" sub I'll use 100 to 200wrms amp.

For 12",200 to 300wrms amp.

For 15" ,250 to 500wrms amp.

Regardless of the brand or the quality of the sub.

Using higher power than what I said, would be a waste, because of power compression, regardless of the brand of sub.
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Old 3rd January 2009, 02:16 PM   #10
AndrewT is online now AndrewT  Scotland
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Quote:
Originally posted by marchel
My short answer would be:

For 10" sub I'll use 100 to 200wrms amp.

For 12",200 to 300wrms amp.

For 15" ,250 to 500wrms amp.

Regardless of the brand or the quality of the sub.

Using higher power than what I said, would be a waste, because of power compression, regardless of the brand of sub.
Based on Dan's post1 data, this is a nonsense answer.
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