# SMD Distortion Detector - tips for setting gain?



## jrodefeld (Dec 21, 2018)

So I ended up buying an SMD Distortion Detector so I could be sure that I'd set my gains correctly on my amplifier. I wasn't having much luck with doing it by ear, nor did I trust the multimeter method.

It seems pretty easy to use, but I'm not sure how to set the gains for the tweeters?

My system:

Pioneer DEH-80PRS
ScanSpeak Illuminator D3004/6020-00 Tweeters
Focal PS165F Flax Mid-Woofer
Morel Ultimo SC 124 12" Subwoofer
Arc XDi 850.5 5-channel amplifier
Arc KS-1200.1 monoblock amplifier

First, I set the subwoofer amp gain. I turned the gain all the way down on the 1200.1 and played the 40hz 0db track.

Then I turned up the head unit to determine the maximum unclipped signal the 80PRS will output.

The distortion signal only turned on at the highest setting 62. When I turned it down a click, the signal turned off at setting 61.

So, then I played track 3, which is 40hz at -5db. Then I proceeded to turn up the gain until the distortion light came on, then back it off slightly until the light turned off.

Sub amp gain setting done.

Then I played track 2, 1khz at 0db to determine the maximum unclipped signal for a full-range amplifier. Again, I turned the gain setting to its lowest level.

For the 1khz signal, I found that the 80PRS would play clean up to 58 out of 62. At 59, the distortion signal would come on, so I backed it off to 58.

Then I played track 4, 1khz at -5db. I proceeded to turn up the gain dial on the "Front" part of the 850.5 until the distortion signal came on. A little more than a quarter of the way up, it came on so I backed it off til it turned off.

Okay, mid-range gain set.


But how do I set the gain for the tweeters? The tweeters will never get anything close to a 1khz signal. In fact, I'm not sure how to defeat the crossover on the 80PRS so I could even sent a 1khz signal for the purpose of setting the gain. The lowest it'll let me set is 1.25khz.

Are there any tips for setting the gain for the tweeters on an Active setup like mine?

What I did is just match the gain setting from the mid-range to the tweeters, but I wonder if I should back it off a bit?

The nominal power of the Focal mid-woofers is 70w.

The nominal power of the Scanspeak tweeters is 50w.


I think I've got the basic hang of it using the SMD Distortion Detector, but I really would like some tips on how set the gain for the tweeters more precisely.

Just listening to the system, it seems like the tweeters are a tad harsh or overpowering the mids. I'm thinking this is because I set the gain the same as the mids, when it should be a bit lower.

Any tips would really be appreciated. Thanks.


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## kanadian-kaos (Sep 12, 2010)

The SMD allows you to set the maximum gain before clipping... 

Just turn the gain on the amplifier for the tweeters down as they need way less power to get loud.

Otherwise, if it is anything like my old Eclipse 8445, there should be a setting to temporarily put it back into Front and rear mode vs 3way outputs... and I am assuming all your speakers are disconnected while doing this.


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## thornygravy (May 28, 2016)

jrodefeld said:


> But how do I set the gain for the tweeters? The tweeters will never get anything close to a 1khz signal. In fact, I'm not sure how to defeat the crossover on the 80PRS so I could even sent a 1khz signal for the purpose of setting the gain. The lowest it'll let me set is 1.25khz.
> 
> Are there any tips for setting the gain for the tweeters on an Active setup like mine?


Swap the mids rcas with the tweeters rcas on the amp. Use the DD-1 to find the maximum for the channels you'll be using on the tweeters. That way you bypass the crossover.

Swap em back, then start turning those suckers down to your liking. (If you're not using an RTA or anything.)


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## DavidRam (Nov 2, 2014)

You have two types of amps to set the gains for, the bass amp and the full range amp. There shouldn't be any cross overs involved. Set the xdi850 to full range and set the gains the same way you did your mids channels.


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## Weigel21 (Sep 8, 2014)

If your HU distorts about level level 59 on the mids, then you should have set the subwoofer amp gain with the HU set at 58 as well, NOT 61 like you did.

And as stated, you don't want the gain for the tweeters set for maximum clean output, that'd result in ear piercing highs. 

You can swap RCA cables at the amp to set the gain for maximum clean output, then swap back and attenuated the output by either dialing down the gain or through the HUs settings, which is what I'd do as you can easily dial it back and raise it until it blends well without having to leave the drivers seat while listening. 

Also, make sure you DO NOT swap the RCA cables while the stereo is powered on, doing such could blow the Pico fuse.


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## Weigel21 (Sep 8, 2014)

DavidRam said:


> You have two types of amps to set the gains for, the bass amp and the full range amp. There shouldn't be any cross overs involved. Set the xdi850 to full range and set the gains the same way you did your mids channels.


The 80PRS has non-defeatable crossovers for the tweeter output when set to 3-way mode.


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## DavidRam (Nov 2, 2014)

Weigel21 said:


> The 80PRS has non-defeatable crossovers for the tweeter output when set to 3-way mode.


Thanks. My bad, I didn't know that...

Then the next easiest thing, is to set the gains for tweeters to the same level of the mids (as the maximum) and lower them from there... Swapping RCAs back and forth seems unnecessary, imho. 

Also, like Weigel said, don't raise the volume on your head unit after determining that 58 is the maximum un-distorted level. Leave it at 58 and reset gains at that level. 

Btw, I use my SMD DD a lot and love how easy it is...


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## Weigel21 (Sep 8, 2014)

I agree, given that he'll be attenuating the output of the tweeters anyways, he could easily set the gain as close as visually possible, if not slightly lower, on the amp to that of the channels for the mids, then begin attenuating the output by lowering the gain further or by sitting in the drivers seat and using the HUs feature to attenuate the output via the level adjustment for the highs. The latter is what I'd do, as hearing it blend properly while you're at the amp is not going to be as easy or effective. (IMHO).


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## openglcg (Jun 23, 2018)

this sort of thing comes up alot here and the general answer is that: tweeters need so little power compared to everything else that you should start at the lowest gain and adjust upward to match mids.

some tweeters seem to have ratings that would casue pain to most people. I run 2000w to my sub but i seriously doubt that Im running the full 75w to my tweeters. probably under half that.

the dd1 is a good tool but its not super useful for tweeters. based on the xmax and power ratings for those they should get to loud levels especially if you cross high enough at 2.5k or higher. if you do have the urge to listen at very loud levels make sure you listen for pops / clicks and back off if you hear them.


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## Smdaniel-11 (Feb 4, 2019)

Ran into the same issue. I have stepped up to a Zapco DSP. 
I ended up getting my voltmeter out and cut the tweeters power back. You can balance them out pretty accurately.


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## jrodefeld (Dec 21, 2018)

Okay, so the trick is to just lower the gain on the tweeters until they "blend" well with the mids and sub?

I re-adjusted the sub amp gain and mids gain using audio level 58 (the highest clean output when playing the 1khz tone). Sub and mid gain is now set perfectly I think. I used the 5db tone for both, which the manual said is best for maximum sound quality.

The gain for the mids is set a tad more than a quarter turn on the knob. 

I matched the tweeter gain, then turned it down about 30% or so. It sounds pretty well-balanced thus far.

I guess I got it set properly now?


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## Smdaniel-11 (Feb 4, 2019)

Sounds like you got what you where looking for. Great entry radio, I ran one for a bit and it actually got me back into audio. I am very happy SMD has this and the CC-1 for people. They are a great starting point. Best of luck and you are who has to be happy with your set up!


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## riceandpho (Dec 30, 2009)

on the deh 80prs, i use volume 57 for the gain setting.

leave the radio in standard mode and set the crossover to full pass.

sub i use -10db tone. and mids and highs at -5 tone

then you can still use the radio to adjust the speaker level to lower the signal output when needed.

my final level on the tweeter output is -3 on the level part. everything else at the 0 , if i need to lower my subs, i can use -5 when i want.


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## dumdum (Feb 27, 2007)

Weigel21 said:


> The 80PRS has non-defeatable crossovers for the tweeter output when set to 3-way mode.


Set gains initially in f/r/sub mode then enable network mode when connecting speakers back ??


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## Weigel21 (Sep 8, 2014)

dumdum said:


> Weigel21 said:
> 
> 
> > The 80PRS has non-defeatable crossovers for the tweeter output when set to 3-way mode.
> ...


I haven't even removed my 80PRS from its box, so I have/had no idea how easy it is to switch between modes. I've been using Alpine for many years and with those, one must remove the HU to change modes via switches on the unit.


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## rockinridgeline (Feb 2, 2009)

jrodefeld said:


> Okay, so the trick is to just lower the gain on the tweeters until they "blend" well with the mids and sub?
> 
> I re-adjusted the sub amp gain and mids gain using audio level 58 (the highest clean output when playing the 1khz tone). Sub and mid gain is now set perfectly I think. I used the 5db tone for both, which the manual said is best for maximum sound quality.
> 
> ...


Independent of getting maximum amp power from your sub and midbass or midrange channel, you want your gains for the tweeter section of the amp to be set as low as possible to get them to blend with the midrange. Having the gain backed off on the tweeters gives the benefit of lower noise since nearly 100% of your perception of noise on the system is high frequency hiss. If your tweeters need to be attenuated to match the rest of the system, you want to do that at the amp gains to get the benefit of lower noise. You have it set exactly where any expert tuner would set up the system.


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## Shane (Oct 8, 2009)

Just remember that when you adjust the gains on your amp, you are also adjusting your crossover settings at the same time. So when you are turning the gain screw, you are actually adjusting the crossover settings simultaneously. So... adjust the gains and then move on to tuning. If you have everything tuned to your liking and then mess with the gains again, you are throwing all those hours of tuning out the window.


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## jrodefeld (Dec 21, 2018)

rockinridgeline said:


> Independent of getting maximum amp power from your sub and midbass or midrange channel, you want your gains for the tweeter section of the amp to be set as low as possible to get them to blend with the midrange. Having the gain backed off on the tweeters gives the benefit of lower noise since nearly 100% of your perception of noise on the system is high frequency hiss. If your tweeters need to be attenuated to match the rest of the system, you want to do that at the amp gains to get the benefit of lower noise. You have it set exactly where any expert tuner would set up the system.


I found this to be very true. After more testing, it seems that my tweeters sound plenty loud with the gain almost set almost at minimum.

When they were set as high as the mids, or to a slightly lesser degree when they were set 30% lower, the sounded a tiny bit louder, a bit more shrill, but I noticed more noise.

I'd prefer less noise, especially if the tweeters sound loud enough.

So it seems I've really got all the gains set correctly, by the books.

But if, once I record all the speakers in Room EQ Wizard with my mic, I find that the subwoofer is too loud and overpowering compared to the mids and tweeters, do I turn down the levels or turn down the gain?

Will both methods accomplish the same thing?

Also, I'm a little confused about how the gain setting relates to the crossovers.

If I understand correctly, the crossover settings I enter into the 80PRS are not necessarily the real, measured crossovers. 

The electronic crossovers I have entered into the 80PRS are:

Sub LPF: 63hz
Mids HPF: 80hz
Mids LPF: 2.5khz
Tweets HPF: 2.5khz

All with a 24 db/oct slope

Should be actually reading these precise crossovers when I do my measurements in REW? Should I modify these electronic crossovers until I measure these actual, acoustical crossover points?

I think the key to getting the sound I'm after is properly blending the sub with the mids.

Speaking of that, on another thread someone suggested that time aligning the sub is not as straightforward as simply using a tape measure. Instead they recommended flipping the polarity, then playing a sine wave tone at the crossover point, then changing the time alignment until the sound "disappears", then flipping the polarity back to normal.

I don't understand the science behind this, but if it works I'll go for it.

Thanks for all your help.


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## DavidRam (Nov 2, 2014)

For those that are interested, here is the SMD DD1 manual:

http://www.bladeice.com/wp-content/uploads/2013/12/Distortion_Detector_DD-1_Ver._5.pdf


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## given_to (Jun 10, 2012)

DavidRam said:


> For those that are interested, here is the SMD DD1 manual:
> 
> 
> 
> http://www.bladeice.com/wp-content/uploads/2013/12/Distortion_Detector_DD-1_Ver._5.pdf


 
Reading through the manual...

Problem: Low battery LED is on 
Solution: Really?

Lol


Sent from my iPhone using Tapatalk


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## JamesRC (Sep 18, 2017)

I approach this by setting my mid-bass first. They're my baseline. Set them just below the clipping point. From there set sub level to match the EQ curve; see if it's clipping. If yes, set it so it doesn't clip, then lower the mid-bass as needed. Then set tweeter to match the EQ curve. Check out the level-setting section in Andy's tuning guide on the Audiofrog site to see what I'm talking about. It's downloadable on the Testing Gear page. 

Tweeters are extremely efficient. They don't need much power to move. Once your mid-bass and sub are set, you won't need to see if the tweets are clipping because they won't be. To give you an idea, the gain on my tweeter channel is literally all the way down on my Zapco.


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## ckirocz28 (Nov 29, 2017)

jrodefeld said:


> I found this to be very true. After more testing, it seems that my tweeters sound plenty loud with the gain almost set almost at minimum.
> 
> 
> 
> ...


Do you have a measurement mic that your using with REW? If you do, you can play a 2500 hz sine wave from the signal generator in REW, do mids only, measure db level with the spl meter in REW, then tweets only, match the db level with the gain, and you're done, with perfectly matched levels.


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## EmoJackson (Aug 13, 2018)

Just to add a little question to this thread.

Using the factory headunit sending high level speaker signals to a DSP.

Can you use the DD-1 to find the clipping point of the factory HU by leaving the signal gain on the DSP at 0 and the amp at 0?


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## ckirocz28 (Nov 29, 2017)

EmoJackson said:


> Just to add a little question to this thread.
> 
> 
> 
> ...


Unless the dsp or amp clips before the hu. But you're using the speaker level outputs from the head unit, why not just check those?


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## thornygravy (May 28, 2016)

Even though I would do what ckirocz28 mentioned, just checking at the headunit. 

This is from the manual: "The DD-1 can measure the headunit’s distortion THROUGH the amplifier!"

So it can be done, just make sure to use the 0db tones.


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## EmoJackson (Aug 13, 2018)

thornygravy said:


> Even though I would do what ckirocz28 mentioned, just checking at the headunit.
> 
> This is from the manual: "The DD-1 can measure the headunit’s distortion THROUGH the amplifier!"
> 
> So it can be done, just make sure to use the 0db tones.



That is exactly what I was thinking. In theory it should work with everything connected using these steps.

1. Set the gains to 0 on the DSP and the amplifier section. Use the DD-1 to find the clipping point on the HU. Set the volume point below the clipping point. 

2. Set the input gain on the DSP by using the clipping indicator on the DSP (Maybe verify with the DD-1 at the amp?). 

3. Set the amplifier gain using the max volume points at the stock HU, DSP, using the DD-1. 

That would make sense to me.


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