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Discussion Starter #1
I'm probably going to answer my own stupid question here but if you over power your speakers to have more clean headroom, then you probably shouldn't set the gains according to an oscope right? I mean, the oscope shows you what the max gain setting would be without clipping which would be too much power if you're bridging/overpowering your speakers. So you'd want to lower your gains below max unclipped output, correct?
 

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You would want to use a dmm to the specified voltage. Headroom mainly just allows your amp to cover the dynamics in the music with clipping them.
 

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Discussion Starter #3
Dmm? That isn't a reliable way to set gains.

I'm not talking about how to set gains here... I'm talking about sending 300W to 150W speakers so that you can turn the gains down on your amp, to provide the speakers with cleaner power (less distortion).

I guess I'm asking, is measuring the output of the amp with an oscope just allowing you to find the maximum gain setting before clipping? Because if you're lowering your gains in the example above (300W to 150W speakers), you're throwing that "max gain without clipping" value out the window and just setting it to somewhere below that.
 

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Sort of. If you set with a DMM then that should be about the max voltage the amp can supply without clipping, true. But it depends on what you do with it, you are right somewhat, but depends. You can send 300 to a 150 sub if it does not xmax with regular music. Odds of it puking are slim if you don't bang it all the time like that. However if you play a sine tone, or bass music with sines in it, it can blow the sub. Peaks in the music likely will not though is possible depending on the quality of the sub and the install/tuning. Peaks in normal music are typically brief and will not smoke a VC that fast, but heavy club bass makes those peaks last much longer than say rock music. This is what people are talking about with newer compressed top40 type music, the bass is dialed way up.
 

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if you set the gains for max power on your scope, with your example. doubtfull you will hurt the sub unless you are tonedeaf, lol. since most music is less than 10% power most of the time, you are not going to exceed 150W RMS anyway. you also have a volume knob on your radio, unless you listen to your system flatout all the time, you will never push 300W anyway.

that said, it wont hurt anything to turn the gains down. will give you a measure of safty and not pushing the amp to max will ensure you never clip it.
 

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if you set the gains for max power on your scope, with your example. doubtfull you will hurt the sub unless you are tonedeaf, lol. since most music is less than 10% power most of the time, you are not going to exceed 150W RMS anyway. you also have a volume knob on your radio, unless you listen to your system flatout all the time, you will never push 300W anyway.

that said, it wont hurt anything to turn the gains down. will give you a measure of safty and not pushing the amp to max will ensure you never clip it.
Exactly my point!
 

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It doesn't need to be so complicated. Set your head unit volume level at 75-80% level, turn on some kind of CD, and then adjust the amplifier gain until the sound reaches the normal listening volume level. The ensures that head unit's pre-amp out is not clipped and the amplifier gain is at its lowest possible setting.
 

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Dmm? That isn't a reliable way to set gains.

I'm not talking about how to set gains here... I'm talking about sending 300W to 150W speakers so that you can turn the gains down on your amp, to provide the speakers with cleaner power (less distortion).

I guess I'm asking, is measuring the output of the amp with an oscope just allowing you to find the maximum gain setting before clipping? Because if you're lowering your gains in the example above (300W to 150W speakers), you're throwing that "max gain without clipping" value out the window and just setting it to somewhere below that.
There's nothing wrong with setting an amp with a DMM. Sure you need an o-scope to find out where an amp clips, but if your running the gain lower than max output an O-scope shouldn't be entirely necessary.

For instance: you mentioned running a 300 watt amp at 150 watts. An o-scope would be required to safely get all 300 watts from that amp but if your only shooting for 150 watts, how do you plan on getting there. You rnot gonna just arbitrarily turn the gain down are you? You need to measure the output so you can hit your target voltage. A DMM is perfect for this. Besides the voltage reading that is on an o-scope is just a DMM anyhow.

Also, I was having this discussion with minbari the other day; if you have a 300 watt amp and set it's gains to run at 150 watts that's all it's ever gonna push. In order to have that extra 150 watts of headroom you have to set your gains properly (300 watts) and listen responsibly.

Anyone care to back me up or correct me on this?
 

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While I agree with what most have already stated, I'd look at this from the other side of the equation.

If you set you amp with a 0, -3 decibel tone and the material you listen to never goes above this reference, there should be no clipping.
The problem is. What material do you use to set the gain?

I wouldn't be happy if I set my system up using the above method then put something in with a much lower recording volume. There has to be some room for adjustment.

This is the best argument, for music/daily, against buying an oscilloscope for this purpose.

Headroom is never a bad thing to have, but what percentage of distortion/clipping, and at what frequency is audible to you?

I've tried the DMM method before, but use my ears to finalize the settings.
I've not lost a speaker yet.

If you aren't seriously overpowering your driver, there shouldn't be a problem with toasting coils all the time.

Hope this helps.
 

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There's nothing wrong with setting an amp with a DMM. Sure you need an o-scope to find out where an amp clips, but if your running the gain lower than max output an O-scope shouldn't be entirely necessary.

For instance: you mentioned running a 300 watt amp at 150 watts. An o-scope would be required to safely get all 300 watts from that amp but if your only shooting for 150 watts, how do you plan on getting there. You rnot gonna just arbitrarily turn the gain down are you? You need to measure the output so you can hit your target voltage. A DMM is perfect for this. Besides the voltage reading that is on an o-scope is just a DMM anyhow.

Also, I was having this discussion with minbari the other day; if you have a 300 watt amp and set it's gains to run at 150 watts that's all it's ever gonna push. In order to have that extra 150 watts of headroom you have to set your gains properly (300 watts) and listen responsibly.

Anyone care to back me up or correct me on this?

I believe this will come down to the level of the material you set the amp at versus the level of the recording.
 

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Discussion Starter #11
For instance: you mentioned running a 300 watt amp at 150 watts. An o-scope would be required to safely get all 300 watts from that amp but if your only shooting for 150 watts, how do you plan on getting there. You rnot gonna just arbitrarily turn the gain down are you? You need to measure the output so you can hit your target voltage. A DMM is perfect for this. Besides the voltage reading that is on an o-scope is just a DMM anyhow.
Well that makes sense.

So.. if I have 300 watts going to each midbass, but they only handle 150 each, at 4ohms nominal, i should aim for about... 24.5V AC right? according to ohm's law.

And that is exactly what i was asking.. I wondered if I set my gains with an oscope do i just arbitrarily turn the gain down hoping I get it right for 150 watts? Perfect way of wording it! Couldn't find the right words


Thanks for the responses everyone
 

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Not to steal your thread, but since it's on the topic. I have a pair of Hybrid audio 6.5 Clarus and have thought of buying a jl hd600/4 to power them. I was thinking of using 2 channels to power the components (150x2 @ 4 ohm) using a o silla scope on the amp once head unit is set at the volume before it clips, but would it be best to bridge the amp and set the power to 150x2 @ 4 ohm or would it be best to set the amp to send 175x2 @ 4 ohm? I'm not too sure on how much these components can take, but i was thinking of using like 70-80hz xover point since i do have a woofer in the trunk. Also after reading steve meads dd1 manual it states that -5db test tones is for sound quality and -10db is a comprimise of sq/loudness and -15db being loudness. what do you guys think of this info that is found on his manual? hope to hear some feedback soon thanks
 

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Don't forget the voltage from a RMS DMM on AC will be different than the voltage you see at peak on a scope. A simple formula to convert them though.

The whole problem is source material level, its all different. You set gains on 0dB and put in some old CD and its quiet....go the other way and you clip. The only way around that I know of is an amp that limits at clipping or a clipping indicator.
 

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Don't forget the voltage from a RMS DMM on AC will be different than the voltage you see at peak on a scope. A simple formula to convert them though.

The whole problem is source material level, its all different. You set gains on 0dB and put in some old CD and its quiet....go the other way and you clip. The only way around that I know of is an amp that limits at clipping or a clipping indicator.
My scope (DSO Nano V2) has separate settings for peak and RMS voltage. Since it's the cheapest o-scope out there, I assumed they could all do that.
 

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My scope (DSO Nano V2) has separate settings for peak and RMS voltage. Since it's the cheapest o-scope out there, I assumed they could all do that.
I have an old Hitachi scope, it does not show any voltage at all. You have to use the scale on the screen to determine peaks, and depends on what range the scope is set to. Newer scopes will show peak voltage must be nice lol, but I have a fluke meter to show me RMS if I need, well two of them actually. One is an old table top thing I got for $15 shipped it works like a charm, exactly same read as my much newer one. Also have a clamp meter than does RMS or peak, voltage or amperage, but I have only used that for 12v power testing not sure what it would show for AC.
 

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ya, most DSOs do alot of calculation functions for you these days. very handy. still have to know what the calculations mean ;)
 
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