best way to tune amp

twisted2corpse · 05-15-2008, 07:42 AM

I was wondering if anyone had any input on help me tune my amp? Listen to rap/hard rock/techno Mainly. Thanks JL 500/5

Futurepr3 · 05-15-2008, 07:49 AM

bump i would like to know also

CNUco2007 · 05-15-2008, 08:09 AM

I personally have an engineering background so I use my Multimeter and Ohm's Law :) Basically, if You know the load resistance and target power, then you can calculate the necessary voltage. You throw in a CD with a 50hz tone, set all settings to flat on your radio, diconnect the subwoofer from the amp, and turn the volume on the head unit up to 75%. Stick your multimeter on the speaker terminals on the amp, and adjust the input gain until you get the voltage you calculated.

As far as calculating the voltage, it's pretty easy. You know that (Power = Voltage * Current) and you know that (Current = Voltage / Resistance). If you put those two together, you know that (Power = Voltage * Voltage / Resistance). Move things around to calculate Voltage and you get (Voltage = SQRT(Power * Resistance)) where SQRT is the square root.

As an example, my amp is rated at 425Watts RMS and my subwoofer is wired in parallel as a 2 ohm load. so Voltage = SQRT(425 * 2) = 29.15 volts.

This may seem complicated, but it really is pretty easy and it tunes the amp's input gain perfectly. Never turn the input gain up for more bass. It is not a bass knob. It is meant to match the impedance of the pre-outs so that the amp puts out the rated power. A bass boost knob is what is used to increase the bass

tommygii · 05-15-2008, 08:43 AM

The only question that always comes to my mind is: doesn't the impedance (resistance in your formula above) of the speaker change with frequency? Therefore tuning at 50hz would give you a different result than tuning at 100hz or 5000hz?

CNUco2007 · 05-15-2008, 09:14 AM

Yes, that is true. I personally set my LPF to 80Hz and tune to 50Hz but you could tune it higher or lower as well. Here's a good web page that explains the impedance changes due to frequency for anyone who is interested.

Amplifier Output Impedance Why It

Duce2k · 05-15-2008, 11:02 AM

Good info...

The JL's are tuned using a DMM, if you download the manual it gives you step by step instructions

CNUco2007 · 05-15-2008, 11:05 AM

I love JL! I have a 12W6V2

It is sooooo worth the money.

twisted2corpse · 05-15-2008, 03:43 PM

Quote:

Originally Posted by CNUco2007

I love JL! I have a 12W6V2

It is sooooo worth the money.

Thanks for the info. i'll give it a try. JL Rules

tommygii · 05-16-2008, 09:27 AM

Quote:

Originally Posted by CNUco2007

Yes, that is true. I personally set my LPF to 80Hz and tune to 50Hz but you could tune it higher or lower as well. Here's a good web page that explains the impedance changes due to frequency for anyone who is interested.

Amplifier Output Impedance Why It

I'm still struggling with the concept I guess. If I understand this right, I should tune the amp at the speaker's point of lowest impedance that is within the spectrum of sound to be played since the most power draw will be there for a given voltage. So for example, LPF at 80Hz, minimum in the impedance vs frequency curve of my subwoofers at 50hz, then use a 50hz test tone. For front components, the same logic may suggest using a 142hz test tone. Would this be the correct way to look at it?

CNUco2007 · 05-16-2008, 09:57 AM

To be totally honest, I just choose a frequency within the speakers range. 50Hz for subwoofer since it is playing 80hz and below. for midrange, I would choose something higher. If you really wanted to get into it, you certainly could do all the calculations for variable impedance and stuff based on the resonating frequency of the speaker. I honestly don't think your going to notice all that much of a difference in sound but I could be wrong. I haven't actually gone through that much trouble before haha.I just calculate the needed voltage based on the speakers rated impedance (2 ohms in my case) and throw in a test tone of a frequency that is in range.

Shyn · 05-16-2008, 09:28 PM

40 hz for sub, and for the midranges, i tune with 1k hz. Weither thats good or not i dunno, but my test tone cd only has those tones on it.

The only thing i never liked about using a DMM to tune, is that some amps are not really rated at what it says. Most amps dont come with "birth sheets" so its kinda hard to know if you actually setting the gains to high or low.

Plus most subs are not exactly 2 OHMs, but 1.8 or 2.1. Same with subs rated at 4 OHMs.

The best way to tune is with an oscilloscope. With that you can easily see with a speaker or sub starts to clip. Unfortunitly, most people, and somtimes even car audio shops, dont have these laying around.

05-15-2008, 07:42 AM	#1 (permalink)
twisted2corpse Senior Member Join Date: Dec 2007 Location: FL Posts: 189 iTrader: 1 / 100%	best way to tune amp I was wondering if anyone had any input on help me tune my amp? Listen to rap/hard rock/techno Mainly. Thanks JL 500/5

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05-15-2008, 07:49 AM	#2 (permalink)
Futurepr3 Senior Member Join Date: Feb 2008 Location: Portsmouth, NH Age: 22 Posts: 108 Philly iTrader: 0 / 0%	bump i would like to know also

05-15-2008, 08:09 AM	#3 (permalink)
CNUco2007 Senior Member Join Date: Feb 2006 Location: Virginia Beach, VA Age: 23 Posts: 1,124 Eric iTrader: 6 / 100%	I personally have an engineering background so I use my Multimeter and Ohm's Law :) Basically, if You know the load resistance and target power, then you can calculate the necessary voltage. You throw in a CD with a 50hz tone, set all settings to flat on your radio, diconnect the subwoofer from the amp, and turn the volume on the head unit up to 75%. Stick your multimeter on the speaker terminals on the amp, and adjust the input gain until you get the voltage you calculated. As far as calculating the voltage, it's pretty easy. You know that (Power = Voltage * Current) and you know that (Current = Voltage / Resistance). If you put those two together, you know that (Power = Voltage * Voltage / Resistance). Move things around to calculate Voltage and you get (Voltage = SQRT(Power * Resistance)) where SQRT is the square root. As an example, my amp is rated at 425Watts RMS and my subwoofer is wired in parallel as a 2 ohm load. so Voltage = SQRT(425 * 2) = 29.15 volts. This may seem complicated, but it really is pretty easy and it tunes the amp's input gain perfectly. Never turn the input gain up for more bass. It is not a bass knob. It is meant to match the impedance of the pre-outs so that the amp puts out the rated power. A bass boost knob is what is used to increase the bass

05-15-2008, 08:43 AM	#4 (permalink)
tommygii Member Join Date: Mar 2008 Location: Indianapolis, IN Age: 20 Posts: 30 Tom iTrader: 0 / 0%	The only question that always comes to my mind is: doesn't the impedance (resistance in your formula above) of the speaker change with frequency? Therefore tuning at 50hz would give you a different result than tuning at 100hz or 5000hz?

05-15-2008, 09:14 AM	#5 (permalink)
CNUco2007 Senior Member Join Date: Feb 2006 Location: Virginia Beach, VA Age: 23 Posts: 1,124 Eric iTrader: 6 / 100%	Yes, that is true. I personally set my LPF to 80Hz and tune to 50Hz but you could tune it higher or lower as well. Here's a good web page that explains the impedance changes due to frequency for anyone who is interested. Amplifier Output Impedance Why It

05-15-2008, 11:02 AM	#6 (permalink)
Duce2k Senior Member Join Date: Apr 2007 Location: Houston, TX Posts: 2,714 iTrader: 1 / 100%	Good info... The JL's are tuned using a DMM, if you download the manual it gives you step by step instructions

05-15-2008, 11:05 AM	#7 (permalink)
CNUco2007 Senior Member Join Date: Feb 2006 Location: Virginia Beach, VA Age: 23 Posts: 1,124 Eric iTrader: 6 / 100%	I love JL! I have a 12W6V2 It is sooooo worth the money.

05-16-2008, 09:57 AM	#10 (permalink)
CNUco2007 Senior Member Join Date: Feb 2006 Location: Virginia Beach, VA Age: 23 Posts: 1,124 Eric iTrader: 6 / 100%	To be totally honest, I just choose a frequency within the speakers range. 50Hz for subwoofer since it is playing 80hz and below. for midrange, I would choose something higher. If you really wanted to get into it, you certainly could do all the calculations for variable impedance and stuff based on the resonating frequency of the speaker. I honestly don't think your going to notice all that much of a difference in sound but I could be wrong. I haven't actually gone through that much trouble before haha.I just calculate the needed voltage based on the speakers rated impedance (2 ohms in my case) and throw in a test tone of a frequency that is in range.

05-16-2008, 09:28 PM	#11 (permalink)
Shyn Junior Member Join Date: May 2008 Posts: 9 iTrader: 0 / 0%	40 hz for sub, and for the midranges, i tune with 1k hz. Weither thats good or not i dunno, but my test tone cd only has those tones on it. The only thing i never liked about using a DMM to tune, is that some amps are not really rated at what it says. Most amps dont come with "birth sheets" so its kinda hard to know if you actually setting the gains to high or low. Plus most subs are not exactly 2 OHMs, but 1.8 or 2.1. Same with subs rated at 4 OHMs. The best way to tune is with an oscilloscope. With that you can easily see with a speaker or sub starts to clip. Unfortunitly, most people, and somtimes even car audio shops, dont have these laying around.