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Fman

Adjusting tower speaker gains

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Fman

What is overall thought on pushing tower speakers?  I have substantial power running to my surf 9s.  I have the gains set to not distort at max volume on the zld eq.  I never maxed the speaker out while setting the gains.  Do you guys set them to distort them back off from there? I don't want to toast my speakers but want to take advantage of the power I have running to them.  I am running 300watts at 4ohms to each 9.

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shawndoggy

so kinda two separate questions here, I think:

1. Is it OK for the speakers to distort a little while tuning?  IMHO yes.  You can usually hear it in like two seconds and back down quickly.  not a big deal.

2. Can the surf 9s handle 300w of clean, distortion free power?  Dunno -- that's an exile Q.  But I'd suspect that the answer is yes given how many people are running that setup.  

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David

The 4-ohm speaker is rated at 250 watts RMS. The amplifier is rated at 300 watts RMS into 4-ohms. With a 1 kHz, 0 dB sine wave test tone, and the source controls on full, set the amplifier output AC voltage (with speakers temporarily disconnected) at 32 volts. This will give you just about 250 watts continuous output which should be in the safe zone.

Or 28.3 volts output for a 4-ohm 200 watt speaker.

Edited by David

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Fman
2 hours ago, David said:

The 4-ohm speaker is rated at 250 watts RMS. The amplifier is rated at 300 watts RMS into 4-ohms. With a 1 kHz, 0 dB sine wave test tone, and the source controls on full, set the amplifier output AC voltage (with speakers temporarily disconnected) at 32 volts. This will give you just about 250 watts continuous output which should be in the safe zone.

Uhhh....lost me my friend.  I'm a dumb blue collar worker, your speaking a foreign language to me.  Can you translate to my level?  I set the gains by ear...no flux capacitor gadget in my toolbox:biggrin:

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David
9 hours ago, Fman said:

Uhhh....lost me my friend.  I'm a dumb blue collar worker, your speaking a foreign language to me.  Can you translate to my level?  I set the gains by ear...no flux capacitor gadget in my toolbox:biggrin:

I provided you with a simple and precise method (so you would not toast your speakers as you requested) using a free test tone that you can download off the net, plus a $15 multimeter. Neither qualify as complex gadgetry. This is a simple procedure you can find on many vendor websites. Try the JL Audio site and their 9-step tuning process. They provide a good and simple explanation for all consumers. Btw, there's nothing wrong with tuning by ear. Your ear/brain are the ultimate gadgets.    

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90oldskool

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David

^^^ Good basic video. But keep this important distinction in mind. This method in no way can accurately reveal the amplifier true power because the speakers are disconnected as they should be, and without a low-impedance high-current load you cannot find the true amplifier power. However, when the amplifier power is already a known and you are simply trying to set a threshold within that known limit, this method is useful.

Btw, 50 Hz would apply to a subwoofer only. 1 kHz is used on fullrange/highpass speakers.

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Fman

I did not want to make this over complicated.  If a speaker is not distorting I would assume it is not being damaged?  I was told damage to a speaker occurs when distortion starts?

If an amp is rated at 300w per can is that at full gains?  So in other words would setting the gains at 45% not truly be pushing 300w to the speaker?  It would need be at a higher gain setting to achieve the max watts the amp can produce?

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Slurpee
40 minutes ago, Fman said:

I did not want to make this over complicated.  If a speaker is not distorting I would assume it is not being damaged?  I was told damage to a speaker occurs when distortion starts?

If an amp is rated at 300w per can is that at full gains?  So in other words would setting the gains at 45% not truly be pushing 300w to the speaker?  It would need be at a higher gain setting to achieve the max watts the amp can produce?

Howdy @Fman.  It's not a 1 to 1 relationship like you're reaching for.  A gain on the amp is only a multiplier.  So it's more of a A x B = 1 relationship. 

The amp has a top-end.  That top-end is dictated by the safe operating maximum of all the electronics as a whole inside it (we hope).  It's your job to make sure if you max out the amp you aren't asking too much of the speaker.

Anyways, the other half of the amplifier is the input.  It has a range of input voltage that it can see.  By turning up your volume you are turning up the 'gain' on that input voltage before it gets to the amp.  You can turn it up so much that the amp wouldn't see the whole signal.  Kind of like trying to see something large through your window that came too close.  The frame just crops the edges of your vision.  Back it off some from the window and the entire image comes into view.  The analogy is true of an amplifier input stage.  

Now, most of the time though you don't have a system that is making a signal that fills (but doesn't exceed) the entire window the amp can see.  That would be the optimum case if it were so, but usually the signals from equipment are designed to be conservative with the intention of being friendly to all amps.  This is where the gain on the amp comes it.  It can shrink or magnify that signal seen at the input of the amp as you see fit.  Not surprisingly, we normally magnify it at least some.  You'd shrink it if you were matching up speakers or doing other tasks.  For the simplified discussion of what gain is though, it's a magnifier.  You could turn an already ideal input signal up all the way and magnify the output to the maximum of the amps capability to multiply the input signal.  However, you'd most likely increase the output out-of-range of the amps ability to render that same signal on the output.  Distortion is what you hear that called, but it's too broad a term.  It's also more accurately called clipping, because it really does look like someone took a hedge trimmer to the top and bottom of the output.  You could also think of it as turning the zoom up too much on your photo-copier and only a fraction of the image is actually printed on the paper.  The rest is cropped out.  

You're playing a game of algebra really.  Volume Gain x Amp-Gain x (optional: Head-Unit-Gain like on a WS-420) x (optional: equalizer gains) = Speaker Power.  Make any of those 'gain' numbers too big and the final number is too big and you have a problem.

I've had it work out on my boat systems a few different ways over the years.  But since you sort of need the volume to do it's thing, then you turn it up most of the way to tune by measurement device like a multi-meter. [insert David's recommendation here].  Tuning by ear from up clase at that volume would require a gifted ear and a willingness to suffer hearing damage eventually. :p  I found a setting of 32 on my '16 was as high as I could go without getting a distorted signal from the black box for the amps to start with.  Before I put some equalizers in my system I believe most of my amps had gains somewhere around 60% of their full range to deliver close to their maximum power to the speakers.  When you start adding more knobs to turn, then you get into some really interesting decisions needing to be made.

Edited by Slurpee

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David
7 hours ago, Fman said:

I did not want to make this over complicated.  If a speaker is not distorting I would assume it is not being damaged?  I was told damage to a speaker occurs when distortion starts?

If an amp is rated at 300w per can is that at full gains?  So in other words would setting the gains at 45% not truly be pushing 300w to the speaker?  It would need be at a higher gain setting to achieve the max watts the amp can produce?

Sorry, but you are getting bad information.

Too much distortion does not cause speakers to fail. If that was true you would have your greatest risk with a 30 watt amplifier. Too much power is actually what causes a speaker to fail. Now here is the important extra information you need to understand. Most any amplifier can produce much more RMS power than its true clean power when clipped or over-driven, perhaps as much as 20% more. More power = increased risk of damage. Besides sounding horrible, audible distortion is a definite clue that you have exceeded the clean power level and an indication that excess power is being produced. Speakers cannot interpret the waveform shape, they simply are affected by the whole of the workload inherent in that waveform.

No, an input set at full gain is not at all representative of the full amplifier power output. Other factors would include the amount of voltage present at the input or the amount of resistance present across the output. That is precisely why you have such a wide range on your input sensitivity controls.

So back to more simple info. Audible distortion is a loose indication you have exceeded the 300 watts. So that is an important threshold...but perhaps still a little too much power. You have a 1.25" midbass voice coil. Even 250 watts is mighty rich for that VC size even if it were to be a ruggedly built subwoofer. So my best recommendation is to use the manufacturer stated power limit for their speaker of 250 watts and shoot for that as your highest safe level. At the very first sign of the slightest amount of audible distortion, which is a loose indication of 300 watts, stop and back off by 10%. Or, back it off about 20% for a 200 watt speaker. Understand that the input sensitivity control pots are not linear so there is no real scale to go by. This may not be as exact a method as the one outlined above (using a test tone and multimeter), but it may serve you well enough.        

Edited by David

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Fman

Thanks to both of you for the feedback...definitely shed some light for me.

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MLA

Fingernail for tuning amp = priceless 

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nlouthan

@David,

Would you please explain how you calculated the amp output voltage?

Thank you

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David
9 hours ago, nlouthan said:

@David,

Would you please explain how you calculated the amp output voltage?

Thank you

The formula is stated in the above video. Power (wattage) = AC volts squared divided by resistance (ohms). Or.... Volts = the square root of wattage times resistance.

Again, this can be used to set the maximum non-clipping output if the true power is already a known (was previously tested with a load). But it cannot be used to discover the wattage via reading the output voltage (without a load).    

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