Some things to remember "in the moment"

[chad]

It has been reported here several times of discouragement of losing speaker components and amplifiers during testing and tuning. It’s important to realize a few things. This may be remedial to many, but certainly worth remembering in the “heat of the moment”

Test tones have a 100% duty cycle, this is VERY stressful on amplifiers and drivers, and this is the way to get things the hottest the quickest! If you are not careful with tones you can kiss a tweeter goodbye right quick! The small voice coil simply cannot shag heat quick enough, and there is no break for it to do so! We listen to music not tones.

Setting your amplifiers clipping point with test tones robs you of power down the road. Since we are dealing with such a high duty cycle the power supply of the amplifier AND CAR is under stress, the most stress it will be under. If you set the clip point of your headunit to the clip point for the amplifier with tones you lose one important thing. Amplifiers clip MUCH later with music or bursts, the power supply is not sagging with music (much lower duty cycle) and the amplifier can make more power. This is not so as much with head units and processing. The maximum voltage is the max voltage. They are not driving a low impedance load as an amplifier is. You can usually eek a lot more gain out of an amplifier AFTER you set it to clip with a tone. We listen to music not tones.

Pink noise has a 50% duty cycle, if you can stand it.

There is nothing wrong with FLICKERING the clip light into a low frequency driver; it will take it in stride, no problem. HF drivers SOMETIMES will but it is not recommended. If you are flickering a clip light into a tweet you are GROSSLY underpowered.

A clip is a clip, no matter where it is at in the signal chain. If you clip your crossover the amplifier will amplify the clipped signal, a good amplifier will amplify ANYTHING, even DC on direct coupled amplifiers if no DC protection is present. Sometimes preamp level clipping is nastier than amplifier clipping due to overshoot on the op-amps and can/will have more HF content from clipping. If you clip a head unit and send it to the active crossovers they will separate this HF harmonic information, the amp will amplify it, and it will be passed to the tweeters. Modern gear has a staggering frequency response; this is good, and sometimes bad. I like my amps to clip FIRST, screw that “clip all at the same time stuff.”

The professional amplifier industry has taken a mind boggling approach to amplifier ratings and the FTC has agreed. Back in the day when you bought a Crest 8001, Crown 3600VZ, or larger type amp it came shipped with NO power plug on it, just a pigtail. Because if they shipped it with a standard 20A plug it would not adhere to safety ratings. These amplifiers can pull WAY more than 20A during sine testing and will play a sine wave at full output ALL DAY LONG and merely keep your coffee warm. No scoffs, no scuffles, this is how I tested them. In a music application it would be no problem to run them on a 20A outlet and flicker the clip light.

Today we are seeing MONDO power output figures and amplifiers equipped with 20A plugs. The FTC has given amplifier makers the go ahead to rate their amplifiers with real world figures under real world applications. Do the new amps make more music power than the old amps and weigh a mere 25 Lbs as opposed to 80Lbs? Yep! Will they do this at a sine wave? NO WAY IN HELL, in fact some see a true sine as oscillation at high levels and will go into protect! We may be seeing car amps doing the same thing as the market turns to more PWM designs as the pro audio industry has. There’s no reason to amplify a sine wave (we listen to music)

The early pro audio amplifiers are hand-me-downs (for the most part) from industrial designs used to power shaker tables, MRI machines (in fact Crown still has a division that makes gradient amplifiers, one is strikingly similar to the MA10000) and if Minivanman finds one surplus he WILL PM me ASAP! These amplifiers were the most powerful out there at the time (at a scorching 150W/Ch) but would drive a dead short. Recently we have gone to PWM and realized that 100% duty cycle was not needed, just bullet proof for the intended application, whereas the standard used to be bulletproof for ANY application! Enter the new FTC figures. Keep your eyes open folks for this to come around to us.

I still have mixed emotions about it because I’m psycho and find nothing more beautiful than a Crest 9001 at full output sine wave heating water in a water heater at full bore with the clip lights lit up ALL DAY LONG! It’s a thing of beauty. OTOH, I’m getting older and if I can tote around an amplifier rack that weighs 1/4 as much, uses less gas to haul, less manpower to do it, and makes more power to my drivers in the intended applications…..how can I bitch?

Now I went on that rant to touch on wire sizing. You can calculate wire sizing all day long and come up with insanely large figures, but remember one thing…… The duty cycle of music is low, we listen to music not tones. Know that your AVERAGE current draw is next to nil in a listening system, note that you are putting in figures into wire size calculators that represent what the system will be pulling full bore. Into low impedance loads. Many wire size charts are set up to recommend sizing based on high duty cycles, such as in heating and motor applications…. Just remember that and think wisely when totaling up your fuse sizes on your amplifiers and knowing you will be running 8 ohm drivers, mids and tweets, etc. Yall are smart folks, use common sense before you buy mondo wire and look at your actual current draw.

And here’s a bit of the FTC amp ratings if you are interested, it’s a neet read. I have some easier to read articles too.I need to find them.

http://www.soundandcommunications.co...6_06_audio.htm

Chad

[bikinpunk]

Originally Posted by chad

Setting your amplifiers clipping point with test tones robs you of power down the road. Since we are dealing with such a high duty cycle the power supply of the amplifier AND CAR is under stress, the most stress it will be under. If you set the clip point of your headunit to the clip point for the amplifier with tones you lose one important thing. Amplifiers clip MUCH later with music or bursts, the power supply is not sagging with music (much lower duty cycle) and the amplifier can make more power. This is not so as much with head units and processing. The maximum voltage is the max voltage. They are not driving a low impedance load as an amplifier is. You can usually eek a lot more gain out of an amplifier AFTER you set it to clip with a tone. We listen to music not tones.

Pink noise has a 50% duty cycle, if you can stand it.

So, you're saying that by setting your gains with a DMM while listening to test tones, you're not giving your speakers as much power as they could get? Basically we're "under-powering" our speakers using this method? If so, that's fine with me because I'm less likely to have clipping by playing music at the selected volume the gains were set at. However, what would you use to set the gains? I assume it would be "pink noise" since you followed the gain paragraph with that sentence. Thing is, I have no idea what pink noise is...

Search button is my friend.

[chad]

Knowing your speaker sensitivity and setting your REALTIVE gain with a DMM is not a bad thing AS LONG AS your dmm has the frequency response to deal with it. If you DMM can measure frequency it probably has a pretty broad frequency response.

To set a clip point....

You can't with a DMM because it will not show you where the amp clips, the amp will be well into clipping and increasing the input will make the voltage go up on the DMM. DMM's measure RMS AC voltage not P-P, P-P can stay the same RMS can go up in clipping situations.

You need a storage scope and a burst to properly look for a clipping point in a music situation.

Your ears are wonderful peices of test gear.

Chad

[MarkZ]

Originally Posted by bikinpunk

However, what would you use to set the gains?

Ears!

The main problem with using a DMM to set gains is that you're assuming that all recorded musical content peaks at 0dB. I've got some albums that never get that high, and some bootleg live/demo tapes that have transients that are lucky to get to -10dB. So when you set things up so that your volume knob is all the way up at the point where a 0dB recording will clip, then your -3dB songs will only get to max power minus 3dB (or half the output capabilities of the amp!). This is why amplifiers without gain adjustments (eg. your home theatre receiver) tend to clip most content when the volume knob is at around halfway or less. It gives you plenty of room for quiet recordings and low voltage sources.

So what you need to do is set your gain so that the amplifier clips when the volume knob is halfway or 2/3 up or something along those lines. Make the gain too low and you'll never be able to get max power for quiet recordings. Make the gain too high and you lose volume resolution -- in other words, your lowest volume setting will be too loud. Since the actual setting is rather arbitrary, there's absolutely no need to use measurement equipment to set your gains.

PS - A little clipping never hurt anyone. Especially for you guys running all active. It really takes an astounding amount of clipping before you begin to notice -- long duration signals overdriven at an appreciable level. Some of you may be well acquainted with my motto by now: If your speakers can't handle it, then it's time for new speakers!

[chad]

Originally Posted by MarkZ

Ears!

.....

PS - A little clipping never hurt anyone. Especially for you guys running all active. It really takes an astounding amount of clipping before you begin to notice -- long duration signals overdriven at an appreciable level. Some of you may be well acquainted with my motto by now: If your speakers can't handle it, then it's time for new speakers!

And BTW Mark and I are in no way realted

Chad

[bikinpunk]

Originally Posted by MarkZ

Ears!

The main problem with using a DMM to set gains is that you're assuming that all recorded musical content peaks at 0dB. I've got some albums that never get that high, and some bootleg live/demo tapes that have transients that are lucky to get to -10dB. So when you set things up so that your volume knob is all the way up at the point where a 0dB recording will clip, then your -3dB songs will only get to max power minus 3dB (or half the output capabilities of the amp!). This is why amplifiers without gain adjustments (eg. your home theatre receiver) tend to clip most content when the volume knob is at around halfway or less. It gives you plenty of room for quiet recordings and low voltage sources.

So what you need to do is set your gain so that the amplifier clips when the volume knob is halfway or 2/3 up or something along those lines. Make the gain too low and you'll never be able to get max power for quiet recordings. Make the gain too high and you lose volume resolution -- in other words, your lowest volume setting will be too loud. Since the actual setting is rather arbitrary, there's absolutely no need to use measurement equipment to set your gains.

PS - A little clipping never hurt anyone. Especially for you guys running all active. It really takes an astounding amount of clipping before you begin to notice -- long duration signals overdriven at an appreciable level. Some of you may be well acquainted with my motto by now: If your speakers can't handle it, then it's time for new speakers!

Wow, now I'm more lost...what do you use to set the gain with? I mean, audio-wise? Do you use a pink noise track? Do you use music, etc? Because like you said, music is different. However, I did set all my mp3s to the same decibel level via a volume matching program.

I was just fine with the DMM method...dangit, now I'm ruined!

[T3mpest]

If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.

[MarkZ]

Originally Posted by bikinpunk

Wow, now I'm more lost...what do you use to set the gain with? I mean, audio-wise? Do you use a pink noise track? Do you use music, etc? Because like you said, music is different. However, I did set all my mp3s to the same decibel level via a volume matching program.

I was just fine with the DMM method...dangit, now I'm ruined!

I just use various CDs that I'm familiar with. Most are recorded hot, some are much quieter. Personally, I use two tracks in particular for the quiet ones just because I'm familiar with them and they're recorded rather low -- "Double Dip" by Hum (rock) and "Nuages" by Claude Debussey (classical). Both are very dynamic with high crest factors (~12-15dB) and I find that useful to gauge volume.

Anyway, there's nothing special about gain adjustments. It's just a volume knob. The whole point of adjusting it is so that your volume knob on your head unit spans the range you need it to. Don't pay much attention to voltage settings and the like. I know people desperately try to line up the "4v" mark on their amplifier because their head unit says it has 4v outputs, but it's a waste of time.

[bikinpunk]

Originally Posted by T3mpest

If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.

This is a major step off the other tutorials I've read where 0db is the preferred method and anything below was "bad". I'm not disagreeing with you, though.

Originally Posted by MarkZ

Anyway, there's nothing special about gain adjustments. It's just a volume knob. The whole point of adjusting it is so that your volume knob on your head unit spans the range you need it to. Don't pay much attention to voltage settings and the like. I know people desperately try to line up the "4v" mark on their amplifier because their head unit says it has 4v outputs, but it's a waste of time.

I just put the importance on not overdriving your amp. I actually set my gain a tad under what the calculated was. Oh, well. I'll consider your advice. I can't think of any tracks that I can use to tune with right now. Plus, it's hard to change the gain and listen at the same time...might get the woman to help, lol. Setting the gain for my subwoofer would be pure hell like this though...the subwoofer is on top of my false floor, where my amps are under.

Thanks for the info.

[chad]

Originally Posted by T3mpest

If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.

No matter what level the tone is recorded at it's still a 100% duty cycle.

Chad

[evan]

What does clipping sound like?

[chad]

Honestly..... Not like much unless it's severe

The high end will get spitty and you may hear harmonics.

Chad

[npdang]

Originally Posted by evan

What does clipping sound like?

It depends on a great variety of things... for very brief periods of time at low frequencies I doubt you could hear it. It's more debatable in the midrange and treble frequencies. Of course, consistent heavy clipping is definitely audible and sounds as if your recording turned to noise/static.

[MarkZ]

Originally Posted by evan

What does clipping sound like?

You could download some tone generator software (try TrueRTA?) and compare a square wave to a sine wave for a rough approximation. You could also try going into Winamp's EQ window and turn the preamp level all the way up and you can get something resembling what you'd hear clipping real world music. In practice things are a bit different, but it may give you some idea.

[T3mpest]

Originally Posted by bikinpunk

This is a major step off the other tutorials I've read where 0db is the preferred method and anything below was "bad". I'm not disagreeing with you, though.




I just put the importance on not overdriving your amp. I actually set my gain a tad under what the calculated was. Oh, well. I'll consider your advice. I can't think of any tracks that I can use to tune with right now. Plus, it's hard to change the gain and listen at the same time...might get the woman to help, lol. Setting the gain for my subwoofer would be pure hell like this though...the subwoofer is on top of my false floor, where my amps are under.

Thanks for the info.

That's because anything less than a 0db track can cause clipping on actual music. Setting by ear will also allow for light clipping, but will also give you more power on the normal parts of your music. Honestly I've always just set my gains by ear, except for subs. I use songs that I know are "loud", set the hu to 3/4 volume. Then I turn my gains up until it's loud enough, or I hear stress. Once I hear stress I back it off until the stressing sounds are gone, then a tad more for good measure. Subs that usually doesn't work though.

[chad]

Yeah me too, I use ears on the subs too, the sub is least efficient in most situations so once that's dialed in it's just a balancing act IMHO. When the sub gets "blatty" I back off.

Chad

[FoxPro5]

Originally Posted by MarkZ

I know people desperately try to line up the "4v" mark on their amplifier because their head