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Discussion Starter · #1 ·
So I'm ready to tune my amps and head unit for my new system! I'll be tuning using an o-scope and test tones. I had been going off a popular post over at SMD, but I ran into two conflicting statements from the author. Just looking to clear up the right answer.

First statement:
Step 1: Tuning your head unit:
Tools that will be required:
An Oscilliscope with probes or probe and clip connectors
Test tones,
For bass: I recommend using a 40Hz tone.
For treble: I recommend using a 1000Hz tone.
Make sure the tone is the same amplitude that you will use to tune your amp. If it isn't you could either be sending clipped waves from the head unit, or not getting full voltage through the RCAs.

Second Statement:
When it comes to tuning your system you should always use a 0dB tone to set your head unit volume, EQ, Epicenters, etc... but you may use whatever desired tone for the amp. If you were to use a sine wave of -3dB to set your head unit, then used the -3dB tone to set your amplifier it would be tuned as if you used a -6dB tone on the amp. However, now since you had tuned your head unit with a lower amplitude, your head unit will have a higher maximum volume. At that volume the head unit could actually be clipping a bit.

Which train of thought is correct? Should HU be tuned w/ 0dB tone regardless, or should the amplitude of the tone match the the amplitude of the tone you use for your amps?

Thanks guys
 

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0db on headunit rcas to check for clipping before full volume.

0 or -3 for midbass as its always the weakest link. Everything else is level matched to loudest midbass volume.

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You're not tuning, you're simply setting gains. Setting gains doesn't require an o-scope or test tones. Are you using a DSP, or just head unit to amps?
 

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If you have a huge amount of power headroom, then 0db is desirable because you're gauranteeing a clean signal with no clipping and minimum distortion, no matter the source.

I think everyone's aware of that.

If you have rated or less power and tune with 0db you'll likely not have enough volume.

It also depends on the source.

Most high quality flac / Wav files I've analyzed have a maximum gain of -6db (or even -10), but some converted mp3s hang near 0db for most of the track.

This is the main problem, varying source levels.

If you tune for 0db, then you are preventing the "loudest" sources (mp3) from clipping. Then you go to listen to a high quality FLAC file and it may not exceed -10db, now you don't have the volume you need if you want to crank it up.

I've seen people go as low as -10 db test tones.

If you tune with, say -6db tones, now you are right below clipping for high quality tracks at Max volume, but mp3s will clip.

The solution?
Turn down the volume a bit.

So if you trust your ears to turn it down when it's distorting, you can tune with lower test tones to get more volume range.

IMO, whatever you choose, you should use the same level of test tone for the entire signal chain.

That will set all your equipment right below clipping for your target and net you the most overall power.

It's also good to use several test tones throughout the range to check for clipping.

Equipment will start clipping at certain frequencies before others. I found my DEH-80prs was clean to 61/62 volume, but at max, it started clipping the 100hz area. If I just tested with a 1k tone and 50hz tone I would never have known that.

As a bonus, if you run a 4channel amp, setting gains may reveal that one half (front) has more power than the other (rear).

Connect your mids to the beefiest channels.







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A lot of people in this hobby are passionate about the technical, scientific side of things, and because of this we like to use all kinds of measuring devices to optimize our equipment. It’s understandable that people want to use an o-scope and test tones for setting gains, but this is a case where using fancy meters won’t get you to a point that is any more optimal than using your ears.

The reason for this is because if you set gains using a 0dB tone at 40hz, that is the only circumstance where your gains will be optimal. Anything other than 0dB, and anything other than 40hz will be less than optimal. You simply cannot set gains to be optimal across all frequencies, at all recording levels. Luckily, that doesn’t matter. Gains only need to be set within an acceptable range. Within this range all you need to accomplish is an acceptable SPL at an acceptable distortion level.

Basically, set your head unit volume to about 75%. Play some well recorded music that you are familiar with and slowly turn up the gain until you hear distortion (or until you’ve reached an acceptable SPL). Back the gain down a tad so that the sound is clear again, and you’re done. If you are doing an active system, start with the midbass, then simply adjust the tweeter gain to balance the response with the mids, you won’t need much gain at all for the tweeters, I’ve often left it in the minimum position.
 
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