# Noise floor and high efficiency drivers



## Freudie2 (May 19, 2015)

As I wrap up my first horn system I am plagued with noise floor issues.

Background:

Front stage consists of two ES full size horns with Beyma cd10nd drivers coupled with 2 JBL 2118h midbass drivers in some fairly massive fiberglass kick pods I made.

Amps for the front: Zapco DC200.2 for the horns, PG Xenon 100.4 bridged running the two midbass drivers.

Issue:

I can hear hiss in the horns and the midbass drivers. I have the Zapco -8db on the output level. That helped tremendously (and for tuning as well...), but with car off in the garage I can hear it.

The midbass: I have the gain to the floor on the Xenon amp. I can hear a slight hiss.

From what I can tell this is a tradeoff in a car with high efficiency drivers. Really a drag. Thinking that short of going to some very high end/esoteric "car audio" amps I am at the good as it gets stage.

The good news is I can't hear this with engine on at all.

Is this why I see things like Milberts and high end Sinfoni amps in most hlcd installs?

Note: The hiss is totally from the amps. I proved this by disconnecting the input cables to both amps. Still hear the hiss. It's very slight, just wish it was "none" (if that's even possible in this scenario).


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## Freudie2 (May 19, 2015)

Realized I never posted my build here (been posting mostly on the PG forum).

Here is my latest project cross-posted from the other forum, enjoy....I did:

Phoenix Gold Phorum • View topic - Project Serious


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## Patrick Bateman (Sep 11, 2006)

If you wire resistors inline with your compression drivers it will lower the noise floor.


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## freudie1 (Nov 16, 2009)

Patrick Bateman said:


> If you wire resistors inline with your compression drivers it will lower the noise floor.


Basically that would just attenuate the output of the compression driver correct? If so, aren't I doing the same thing via the output level adjustment on the Zapco amp? Case in point I currently have it set for -8db on the output level adjustment and the noise floor went way down (so did the output of course, but the volume knob compensates).


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## gregerst22 (Dec 18, 2012)

Do you have high level / low level input selection on your amps? I had a noise floor issue that was solved by switching my amps from low to high level inputs. The amps get their signal straight from a Mosconi DSP.


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## ca90ss (Jul 2, 2005)

If you take one of your compression drivers to the local stereo shop and ask nicely they'll generally let you try it out on a few amps on their display to see which one has the lowest noise.


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## Patrick Bateman (Sep 11, 2006)

freudie1 said:


> Basically that would just attenuate the output of the compression driver correct? If so, aren't I doing the same thing via the output level adjustment on the Zapco amp? Case in point I currently have it set for -8db on the output level adjustment and the noise floor went way down (so did the output of course, but the volume knob compensates).


True, but with resistors you can knock it down by twenty or thirty decibels. Compression drivers only need ten watts to hit 120dB. And resistors don't hurt your power handling, as long as the limiting factor is the driver, not the amp.

Resistors simply drop the noise floor.

I also run my DSP off batteries, that makes a HUGE difference. My system has zero noise.

Even if I'm wrong, it only costs $2 to find out. Resistors are a buck.


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## nextproject (Oct 17, 2010)

Patrick Bateman said:


> If you wire resistors inline with your compression drivers it will lower the noise floor.


Sorry.. I am a little bit of an electrical moron...
What value resistors?.. How is it wired in?


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## oabeieo (Feb 22, 2015)

Every horn I've installed has had hiss, but a tolerable amount. Now noise, that is tough .
I have had very good experience using the biggest 2ch amp with a s/n ratio in the 90s or more. And have the gains ALL the way down and up a butt hair. Like 1/16th the way up. 

That's the best I have ever got, and still have some hiss if you stick your head on floor near speaker to hear it . 

If your fuse box is near a horn you probably won't get rid of it unless you shield it with a magnet. I've taken old neo tweet magnets placed it on the magnet of the horn so it resists it, taped it on in a spot that helped noise, had limited success with that like maybe a db or two of noise. I hear mumetal works good never used it tho.


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## Patrick Bateman (Sep 11, 2006)

nextproject said:


> Sorry.. I am a little bit of an electrical moron...
> What value resistors?.. How is it wired in?


Go to Radio Shack, get some 10ohm resistors, they're two to a pack and they sell for $1.99

Wire them inline and watch the noise go down (Between the positive terminal of the compression driver and the amplifier)

If 10ohm doesn't do it, up the ante to 20ohm

LeCleach used 30ohm. (Google "LeCleach 30 ohm" and you'll find the paper, I think it may be in French though.)


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## nextproject (Oct 17, 2010)

Thanks!.. Have a wall of resistors at work... Saves a trip or two to RS...


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## subwoofery (Nov 9, 2008)

Most amps that have a DSP inside have a low S/N ratio. 
Highest I've seen have been in the 70s 

I once tried an Arc SE amp on my horns and it was silent (think it was the 2150)

Kelvin


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## Freudie2 (May 19, 2015)

subwoofery said:


> Most amps that have a DSP inside have a low S/N ratio.
> Highest I've seen have been in the 70s
> 
> I once tried an Arc SE amp on my horns and it was silent (think it was the 2150)
> ...


The Zapco DC200.2 that I am using on the horns has a published (accurate who knows...I digress) snr of ">95 db".


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## Freudie2 (May 19, 2015)

Patrick Bateman said:


> True, but with resistors you can knock it down by twenty or thirty decibels. Compression drivers only need ten watts to hit 120dB. And resistors don't hurt your power handling, as long as the limiting factor is the driver, not the amp.
> 
> Resistors simply drop the noise floor.
> 
> ...


I can do the same thing with the Zapco amp I am using. The dsp inside the amp allows for up to -128 db of attenuation on the output channel. Indeed if I drop it to >-10db I can basically hear nothing (I went way below that in testing and it's silent, but it's too much attenuation for my tastes much beyond 10db).

I think I am "fine", this is just me expecting a bit more out of "high end" equipment (I use that term loosely as I don't find car audio equipment to be particularly that amazing, hence the reason most of my drivers are from the pro audio world).

I'm still amazed that the Helix DSP is living up to it's specs. It's the first "car" DSP I've used that doesn't cause me grief.


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## Eric Stevens (Dec 29, 2007)

I would first determine the cause of the hiss or noise floor. Start with amp and horns only with no input to the amp and gain at minimum, try adjusting gain higher to see if it introduces any noise. If the amp is quiet at lower gain levels its not your problem.

Next add the next processor in line into the mix with no input into the processor. Listen for noise with the output level of the unit set at unity gain ( what comes in is going out). Most processors have gain on the input and outputs only attenuate so you want the input set to 0dB of gain and output at maximum. 

Try this and hopefully it helps


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## nextproject (Oct 17, 2010)

Eric Stevens said:


> I would first determine the cause of the hiss or noise floor. Start with amp and horns only with no input to the amp and gain at minimum, try adjusting gain higher to see if it introduces any noise. If the amp is quiet at lower gain levels its not your problem.
> 
> Next add the next processor in line into the mix with no input into the processor. Listen for noise with the output level of the unit set at unity gain ( what comes in is going out). Most processors have gain on the input and outputs only attenuate so you want the input set to 0dB of gain and output at maximum.
> 
> Try this and hopefully it helps


Thanks Eric... 
A truly logical and "should have thought of that" approach that I have not done yet... Just assumed it was the MS8


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## Freudie2 (May 19, 2015)

Eric Stevens said:


> I would first determine the cause of the hiss or noise floor. Start with amp and horns only with no input to the amp and gain at minimum, try adjusting gain higher to see if it introduces any noise. If the amp is quiet at lower gain levels its not your problem.
> 
> Next add the next processor in line into the mix with no input into the processor. Listen for noise with the output level of the unit set at unity gain ( what comes in is going out). Most processors have gain on the input and outputs only attenuate so you want the input set to 0dB of gain and output at maximum.
> 
> Try this and hopefully it helps


The only thing that lowers the hiss is if I drop the output level on the Zapco amp to -10 db or more. I've proven it's the amp itself by unplugging the inputs to the amp (I still get hiss if I don't attenuate the output level). NOTE: I've already tried the walk up the chain method (even tried adjusting input and output levels on the processor and/or unplugging inputs to processor as I originally suspected the OEM headunit...no change at all). It's the amps and the high efficiency drivers (horns and midbasses in my case) are displaying it (or rather exposing it). Short of going to "better" amps (of which I doubt will help) this is what I have at this point.

I have the same issue with my midbass amp and the Phoenix Gold amp that is running those (unfortunately I can't attenuate below setting the gain to all the way down).

Like I said, it is NOT a major issue now (can't hear it at all with engine running)...but I was surprised to have audible hiss with what I considered "good" equipment (and my install is not an issue...I have zero alternator whine, no clicks, pops, nada.....the ground I installed is 1/0 gauge right to the frame with a huge bolt/star washers/etc.....measured basically identical to the ground at the battery with a DMM).

I had massive hiss with the original horn amp (Lunar Audio 40x2) that I was using. That was truly just a garbage amp....horns only illuminated that fact. The Zapco is miles ahead of that amp in terms of noise floor.


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## oabeieo (Feb 22, 2015)

Freudie2 said:


> The only thing that lowers the hiss is if I drop the output level on the Zapco amp to -10 db or more. I've proven it's the amp itself by unplugging the inputs to the amp (I still get hiss if I don't attenuate the output level). NOTE: I've already tried the walk up the chain method (even tried adjusting input and output levels on the processor and/or unplugging inputs to processor as I originally suspected the OEM headunit...no change at all). It's the amps and the high efficiency drivers (horns and midbasses in my case) are displaying it (or rather exposing it). Short of going to "better" amps (of which I doubt will help) this is what I have at this point.
> 
> I have the same issue with my midbass amp and the Phoenix Gold amp that is running those (unfortunately I can't attenuate below setting the gain to all the way down).
> 
> ...


Is it more on one side than the other? Is the noise more on the driver side? More with engine on? 

If so, dismount horn on driver side and pull it away from fuse box and see if noise lessens.

If not - resistors, however with too high restiance you will have to gain up amp to compensate which will eventually lead you back to noise. 

I would start with 2ohm sand resistors and than 4,6,8,10,12


(Guys would a zobel fix this?) that way speaker gets full power and amp gives full power???)


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## Victor_inox (Apr 27, 2012)

Eric Stevens said:


> I would first determine the cause of the hiss or noise floor. Start with amp and horns only with no input to the amp and gain at minimum, try adjusting gain higher to see if it introduces any noise. If the amp is quiet at lower gain levels its not your problem.
> 
> Next add the next processor in line into the mix with no input into the processor. Listen for noise with the output level of the unit set at unity gain ( what comes in is going out). Most processors have gain on the input and outputs only attenuate so you want the input set to 0dB of gain and output at maximum.
> 
> Try this and hopefully it helps


 That is exactly correct.


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## LumbermanSVO (Nov 11, 2009)

I had an 800PRS as my source going to a DEQ.8 with an AG200 powering my horns and never had a noise floor issues. Then I went digital directly from my phone to the DEQ.8 and now I have an audible noise floor on the horns with the same amp. It's a curious problem. I just won't have the time to solve it until late August.


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## Freudie2 (May 19, 2015)

oabeieo said:


> Is it more on one side than the other? Is the noise more on the driver side? More with engine on?
> 
> If so, dismount horn on driver side and pull it away from fuse box and see if noise lessens.
> 
> ...


It's equal on both sides. If I get bored I may throw a few resistors inline, but I'm splitting hairs at this point. I don't listen to the radio with engine off in my garage typically (unless I'm tuning which I'm doing for the next week). 

It's 100% the amps though. Like I said, no dsp in the chain (or inputs plugged in)....same results/hiss. It's low though.


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## Eric Stevens (Dec 29, 2007)

Freudie2 said:


> The only thing that lowers the hiss is if I drop the output level on the Zapco amp to -10 db or more. I've proven it's the amp itself by unplugging the inputs to the amp (I still get hiss if I don't attenuate the output level). NOTE: I've already tried the walk up the chain method (even tried adjusting input and output levels on the processor and/or unplugging inputs to processor as I originally suspected the OEM headunit...no change at all). It's the amps and the high efficiency drivers (horns and midbasses in my case) are displaying it (or rather exposing it). Short of going to "better" amps (of which I doubt will help) this is what I have at this point.
> 
> I have the same issue with my midbass amp and the Phoenix Gold amp that is running those (unfortunately I can't attenuate below setting the gain to all the way down).
> 
> ...


Hmm you have DSP built into that amp. HMM that changes everything. There is a adjsutment process to getting them quiet and I cant remember. They are a little peculiar to get right though gain wise.

Gain hiss is a normal thing and can show up even with the best products.


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## lsm (Mar 11, 2009)

It's not the speakers fault. I have horns and have never had hiss before.


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## Freudie2 (May 19, 2015)

lsm said:


> It's not the speakers fault. I have horns and have never had hiss before.


I never said it was the speaker's "fault". It's more the fact that high efficiency drivers (be it tweeter/compression drivers/mids) EXPOSE the high noise floor of most "good" amps.

What amp do you use with your horns?


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## Freudie2 (May 19, 2015)

Eric Stevens said:


> Hmm you have DSP built into that amp. HMM that changes everything. There is a adjsutment process to getting them quiet and I cant remember. They are a little peculiar to get right though gain wise.
> 
> Gain hiss is a normal thing and can show up even with the best products.


Yes I read something about the Zapco DC amps that they recommended maxing out the output gain and lowering the input gain. I'll tweak a little more, but last week when I was messing with the gain(s) on that amp I only say positive changes with the output gain attenuated.

I probably should just have this thread closed, because honestly it's so low now (and the horns are so loud) that I have very little to complain or tweak (well I can always complain ha!).


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## lsm (Mar 11, 2009)

Freudie2 said:


> I never said it was the speaker's "fault". It's more the fact that high efficiency drivers (be it tweeter/compression drivers/mids) EXPOSE the high noise floor of most "good" amps.
> 
> What amp do you use with your horns?


Maybe "fault" was the wrong word... sorry I get what you're saying though

I use a Milbert now but I have used other amps in the past. Most recently my horns were powered by half of a TRU Technology B475, before that I have used Rockford Fosgate, Soundstream, and MTX to name a few.


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## bitperfect (Oct 1, 2010)

I've had hiss before in my system. After troubleshooting I determined it was the amplifier. After testing a few I ended up with an Arc Audio SE 2075. Their small 2 ch amp I don't think they offer it anymore.

I couldn't be happier, no hiss at all can be heard from normal seating position.


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## nextproject (Oct 17, 2010)

Just for the heck of it... I turned off my (factory) head unit and 80% of the hiss disappeared.... Think I know what the problem is.... 

(Rest of system remains live still)


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## strohw (Jan 27, 2016)

Sounds like you have a snake in your dash. I'd definitely recommend calling animal control.


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## nextproject (Oct 17, 2010)

strohw said:


> Sounds like you have a snake in your dash. I'd definitely recommend calling animal control.


Yeah... Worst part is it obviously doesn't like my radio being on


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## MusicMike315 (Jun 29, 2009)

I have to ask why you have an issue with setting the output to -10? The best gain setting for any amp running high efficiency drivers is as low as possible while still maintaining sufficient total output. I have been out of the business for quite a while now and have started to get my feet wet again and am surprised at the lack of general knowledge in the industry today. All of these numbers thrown about are relative. -10db from what?? Max output of the dsp? Max output of the amplifer? Some arbitrary voltage? Same thing for S/N ratio. There is a lot of literature in the pro audio world about how to maximize gain structure. Most of which starts from the source and proceeds forward. The gain adjustment on most amps should be attenuating the signal from upstream. I don't know where this idea that an amp gain needs to be somewhere other than set to provide full output (or some gain overlap) came from.


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## Freudie2 (May 19, 2015)

MusicMike315 said:


> I have to ask why you have an issue with setting the output to -10? The best gain setting for any amp running high efficiency drivers is as low as possible while still maintaining sufficient total output. I have been out of the business for quite a while now and have started to get my feet wet again and am surprised at the lack of general knowledge in the industry today. All of these numbers thrown about are relative. -10db from what?? Max output of the dsp? Max output of the amplifer? Some arbitrary voltage? Same thing for S/N ratio. There is a lot of literature in the pro audio world about how to maximize gain structure. Most of which starts from the source and proceeds forward. The gain adjustment on most amps should be attenuating the signal from upstream. I don't know where this idea that an amp gain needs to be somewhere other than set to provide full output (or some gain overlap) came from.



I'm in alignment with your logic/thinking. I was more surprised that I had noise at all.

A couple of key takeaways from my build:

High efficiency drivers are very revealing of noise floor.

Zapco DC Reference amps (for those that don't know, these amps have their own DSP inside the amp...I don't use said DSP however I DID have to access it to adjust the input and output level settings....):

Zapco DC Reference series amps have TWO gain settings...input and output. The output is only to be used as a level attenuator. I originally was of the thought that the output level setting at -0db was were it "should be". In other words, this is the first amp I've ever used that allowed for output attenuation and not just gain adjustment for the incoming signal. Messing with the output value (like I said -10db which is "whatever that means") proved to be the ticket for the horns. I can't hear squat even in the garage with engine off now (at least through the horns that is).

Phoenix Gold Xenon amps have a lousy SNR (read: the old literature/manuals for them are BS.). I say this as I can hear very slight hiss through my midbass drivers (once again high efficiency as well) despite the gains being to the floor on the amp (and with no signal input either!). C'est la vie.

Unless you listen to your system in a closed garage with engine off.....noise floor in a properly setup system will be essentially non existent. The second I pull the truck out of the garage I can't hear a single thing other than music and exhaust rumble.


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## subwoofery (Nov 9, 2008)

Freudie2 said:


> The Zapco DC200.2 that I am using on the horns has a published (accurate who knows...I digress) snr of ">95 db".


Finally found what I was looking for... 
Have some tests that shows real S/N ratio for DC Ref amps: 
- DC650.6 has a 78dB S/N ratio 
- DC1000.4 has a 75dB 
- DC350.2 has a 81dB 
Can't find the test for the DC360.4 

Zapco is a very good brand but most amps with a DSP incorporated have that problem. 
The only one that managed to have a S/N ratio up there is the Helix 6 channels amp. 

Kelvin


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## oabeieo (Feb 22, 2015)

MusicMike315 said:


> I have to ask why you have an issue with setting the output to -10? The best gain setting for any amp running high efficiency drivers is as low as possible while still maintaining sufficient total output.


No idea who you are, but that is absolutely correct!

HE drivers need a very low gain, and they can handle boost/cuts in deq way better when there gain is properly set. And they still get silly loud.


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