Originally Posted by flcusat

I was reading this post and also notice that the calculation for a single channel was way off. Assuming that the intended measurement was for just one channel (no bridge mode) in the example, then P=130 Watts, since the Resistance is 2.7 Ohms the Voltage should be
18.73 Volts.
The original calculation was probably made for bridge mode in which case the numbers are right, but not the measuring pointsfor the meter.

Originally Posted by Makdaddy

Cheesehead
He is referring to the diff in musical passages.
Not all music is recorded the same.So he saying find a happy median , that is related to the crest factor.
Now some of that can be corrected with using MP3 Gain to level all of your music
But for setting up your system, you may leave some performance on the table by setting it up with a test tone that runs at +5 or +10 db your music may actually be at 0 db
So in conclusion ask what reference level in db the test tone is set at.
So it may be better to get a test tone set @ 0db or -5db rather then +10db

the original post is a sticky under audio the Harley Tech Talk Forum
I know its a little confusing at times, I too am still trying to wrap my head around it

Originally Posted by flcusat

I was reading this post and also notice that the calculation for a single channel was way off. Assuming that the intended measurement was for just one channel (no bridge mode) in the example, then P=130 Watts, since the Resistance is 2.7 Ohms the Voltage should be
18.73 Volts.
The original calculation was probably made for bridge mode in which case the numbers are right, but not the measuring pointsfor the meter.

Originally Posted by Makdaddy

I found this and copied it over

Hope it helps


First off for the critics out there; I want to point out that to perform a 100% accurate test, an oscilloscope, the knowledge to use it, and multiple test tones/tone generator are required but this procedure will get you pretty darn close with a single test tone and a DMM.

*IMPORTANT* Disconnect speaker output wires from amplifier to speakers during this procedure otherwise you will stress the speakers and could possibly damage them when sending this 1000hz tone through the amplifier. Also disconnect any speakers that are connected directly to the HU.

This is the down and dirty way to test and set your gain controls on your amplifier with a DMM to properly drive your speakers without the amplifier clipping. To test a subwoofer, the process is the same; you simply need a lower frequency test tone for subwoofer frequencies such as 50hz. I don’t suggest you use an iPod to do this mainly because you’ll have to worry about the equalizer settings on that device too. I recommend on 5.25”, 6.5”, or 7.25" coaxial or 3 way speakers, as most are using on their bikes, that you use a 1000Hz 0db test tone to conduct this procedure. This procedure is the same regardless if using RCA inputs to the amp or line-level inputs (speaker wire inputs)



Abbreviations
HU – Head Unit or Radio
DMM – Digital Multi Meter
AP – All Pass – allows all frequencies to pass to speaker
HP – High Pass – allows all signals over a certain frequency to pass to speaker. The frequency is adjustable on the amplifier.
LP – Low Pass – allows all signals below a certain frequency to pass to speaker. The frequency is adjustable on the amplifier and used for sub woofers installations
F – Full – same as All Pass


Information and items needed prior to test procedure:

1- V = √PxR (see below)
2- Test tone CD or thumb drive. This tone can be obtained here and simply burn to a CD (or whatever device you are using) that will play in your HU. Leave this test tone at 320kbps otherwise this will be a futile effort.
3- You will need a decent DMM set to AC volts with auto ranging enabled or if you don’t have an auto ranging meter, set it to measure at least 50vac.
4- Amplifier, HU, speakers already installed and fully tested for functionality.
5- Specifications for amplifier(s) and speakers.
6- For my example I will be referring to the Soundstream PN4.520d amplifier and Polk Audio MM651 speakers. Find your specifications in your owner’s manuals for your specific product. DO NOT USE MAX POWER RATINGS OR BIRTH SHEETS!
a. Amp specs
RMS power 4 ohm load per channel (4 channels) – 100wx4=400W
RMS power 2 ohm load per channel (4 channels) – 130wx4=520W
b. Speaker Specs - You simply need to know what ohms your speakers are (2.7 ohms) and what ohm load the amp will see (2.7 ohms).
7- Set your HU to repeat play mode so it will continue to play the tone. The above tone is 2:00 in length so you have that much time before you will see the AC voltage drop on your DMM. If it does, no biggie, simply wait for it start playing again.
8-If you have an amp with 2 gain controls (usually a 4 channel amp), it is to be treated as 2 separate amplifiers and divide total watt output by 2.




Procedure:

1- What you now need to figure out is the V in the above equation. We know the P and R from the specs above. So, P = RMS output of amp at required ohms and R = ohms the amplifier will see from speaker(s) on that specific channel. In this example P=520/2 (260) (I’m running a 2.7 ohm load to each channel) and R=2.7. So P(260) x R(2.7) = 702. Now you need the square root of 702 which equals 26.49 so V=26.49. This is the AC voltage that you will achieve by adjusting your gain(s) on your amp.
2- Turn all equalizer settings, bass boost, etc. on HU to their minimum settings
3- Turn volume control all the way down on HU
4- Turn all gain controls, bass boost, etc. on amplifier to their minimum settings
5- Turn HP/LP filters to full range. On RF amps it’s called AP and the Soundstream is called F
6- Connect your DMM + (red) lead to the front right speaker output + on the amp. Connect your DMM – (black) lead to the front right speaker output - on the amp.
7- Put test tone CD you burned earlier (or thumbdrive) in HU.
8-Turn your radio up to ž volume. On a HU that displays numbers turn your volume to max then divide that number by 4 to get your ž setting. On HD HUs there are 17 bars to max volume so set your volume at 13 bars.
9- Now look at your DMM. Whatever your AC voltage reading is coming out of the amp, adjust it up to 26.49 (or as close as you can get it)
10- On most 2 channel amps such as the RF PBR 300x2 has only 1 gain control. Most 4 channel amps will have a gain control for the front and one for the rear. The Soundstream PN4.520d has 2 gain controls, 1 for front, the other for rear so I’ll need to repeat this adjustment for the rear channel output also.
11- After you have adjusted your rear gain control to match the front, turn your HU volume down to minimum and take out the test tone CD. Again, you do not want this test tone running through your speakers.
12- Turn everything off and reconnect your speaker wires.
13- Now you can adjust your equalizer or bass and treble back to your liking.

Originally Posted by iMAK79

My amp is SS PN4.1000D and two front Kappa 62.11i speakers. I need some clarifications regarding step 5, 6 & 7 from the above procedure.

5. On PN4.1000D, there is a switch for LPF-FLAT-HPF and a rotating **** 35Hz - 250Hz, how to turn HP/LP to full range?
6. Do the speakers need to be connected to the amp for measuring?
7. Any test tone? Or there is a preferred one?