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FAQ's

FAQ's


FREQUENTLY ASKED QUESTIONS:

#1 - How to set Gain: 

This is probably the Number #1 Tech phone call we get at Diamond Audio.  By a factor of 1,000 to 1!!!   Which is NOT good as this is a VERY basic concept.  It has been written about by many people, tons of YouTube videos, etc.  Guys showing you how you HAVE to use a Oscilloscpe to set it up correctly or at the very least a SMD DD1+, or WORST case a DVM (Digital Volt Meter)    I am telling you straight up..... YOU DONT NEED ANY TEST GEAR TO SET UP A SOUND SYSTEM !  PERIOD!!!


I dont know how many of you have O'Scopes (I have 4 and use them pretty much everyday and have for over 30 yrs).  So I can absolutely tell you it is a SUPER handy tool and a MUST have for a professional installer.  BUT not needed for setting gains....at least for playing MUSIC (SPL?  Different deal)  So here is an article that I "borrowed" from some friends "down under" and modified slightly.  

FOR THOSE OF YOU WHO DONT REALLY CARE ABOUT THE WHYS AND THEREFORES OF SETTING GAINS....CLICK HERE TO GO TO THE TYPICAL SETTINGS I DO IN ALL INSTALLS

I HIGHLY recommend that you DO read this thesis as it wiill make way more sense what and why you set the gains this way...but if you just want to get to  it...click above

Correctly Adjusting Gain and Crossover Controls on your Amplifiers 
By Larry Frederick and Friends

Many retailers/installers/consumers have always had “issues” with adjusting gain.   When is a little too much and when is too much too little?   Do I turn the input gain all the way UP, or all the way DOWN?  A common example of misguided information is the consumer comes back to you after a system has been installed and complains that their “buddy” – or “local audio expert” has noticed that you did not give them all the amplifier power that they bought!   Inevitably the customer’s buddy says that because you have the gain settings tuned WAY down, the amplifier is NOT delivering full power!!    Their rationale is that you’ve CHEATED them on the power they bought!!!!  You’ve set gain at less than half (there is NO such thing as half gain, by the way)…therefore it must be only giving me less than half power!!   To answer those questions and many more….read on!!

THAT’S A RESOUNDING NO TO 1/2 GAIN, 3/4 GAIN. ETC.  MEANS NOTHING WHEN SETTING UP INPUT SETTINGS!!!!!

Half gain or 3/4 gain settings DOES NOT mean that the amplifier is only getting 1/2 power, or 3/4 power.  Totally ridiculous.   If the amplifier is 500 watts, its 500 watts with the gain at minimum or maximum.  Input gains setting s have NOTHING to do with it.  Input VOLTAGE has EVERYTHING to do with it!!!  (read on)

I’ve taken the liberty to “borrow” from our “Down Under” fellow 12 volt guys (read Australia here ) ) and used something they wrote about correctly setting gains from a couple years ago and added some of my own additional information (see credits at the end of the article)  Hey…Why reinvent the wheel?? In addition to their informative article, periodically you’ll see my “2 cents worth” thrown in !

To that end let’s get setting gains correctly!!!

Abbreviations used in this article:

*EQ = Equalizer
*HP = Highpass
*HU = Headunit
*LP = Lowpass
*RMS = Root Mean Square
*W = Watts (Electrical Power)

What is a gain control? (also called Input Sensitivity or "SENS" on many of  our amplifers)

The gain control on ANY amplifier is NOT a volume control. Say it out loud! Turning the gain up higher and higher does not produce higher or ‘full-power’ output. If an amp produces a maximum of 100 watts (RMS) per channel, increasing the gain will not yield more than this.  At 100 w/channel and assuming two channels, it’s a 200 watt total amplifier and – theoretically – a 400 watt mono 4 ohm amplifier if it’s run in a “bridged” mode.  That’s it.  No more.  Turning input gain up (or down) does not make the amp more powerful.  If it’s a 200 watt amp …it’s 200 watts…PERIOD!  Gain has NOTHING to do with adding more POWER.

Better to think of the gain as a ‘sensitivity’ setting:  the higher the gain, the more sensitive the amp is to the signal fed into it.  This means that a headunit (HU) having more preamp output voltage (say 4 volts) will have an amplifier input setting lower than a low voltage preamp output HU (1 volt for example).  This does not make the amplifier more powerful turning the input gain up. In fact turning input gain “UP” causes more system noise..or HISS.

First…we need to understand how an input gain adjustment works…look at the example below of a typical input gain on an amplifier (or signal processor, makes no difference).  For purposes of discussion, let’s say we have a standard amplifier that can take from 0.2 volts (200 mV) to 4 volts of input signal. Look at this rotary gain control illustration as an example.

Input Gain1













Now the question is which side is the minimum setting and which is the maximum setting???  In other words which is the 0.2 v setting and which is the 4 volt setting??  What do YOU think it is????  This is the most basic fundamental concept of gain, and the question which 90% of those who are quizzed get WRONG!!  So what do YOU THINK??   Well….the correct answer is shown below

InputGain_new

















Not what you thought?  Right??   Remember that the input gain control is a potentiometer (pot),  which is nothing more than a variable resistor.   At the “minimum setting” – fully counter-clockwise, it has the MOST resistance, and at the “maximum setting” – fully clockwise, it has the LEAST resistance. The input gain control is just an attenuator.


As an example, consider three gain settings: A, B, C.
 

InputABC















A is ‘low’, B is ‘medium’ and C is ‘high’. The lowest possible setting would be fully counter-clockwise (the A setting) and highest would be fully clockwise (where the gain control is a ‘knob’ or pot) for the C setting.

Now let us say the HU is delivering a 2V signal via the preouts (typically the RCA outputs) at it’s maximum usable volume position BEFORE signal clipping occurs. With the gain at B, the amp may be producing 100WRMS per channel. If the gain is now changed to A (4V setting), the amp is less sensitive; in order to produce the 100 WRMS as before, the HU must now deliver a higher voltage signal, say 4V. Setting the gain to C, the amp becomes much more sensitive; it now may require only a 0.2V signal to produce 100 WRMS.

The whole purpose of gain setting is to match the audio signal voltage output of a given headunit with a given amplifier. You see, unlike some standardized home audio equipment that provides a known signal level from one component to another, car audio headunits and amplifiers can have a very wide range of possibilities of audio output signal levels, both on preamp (RCA) signals and powered (speaker level) signals. The input gain control allows you to essentially match one piece of equipment to the other for ideal performance.

A HU with a higher voltage signal will require a low gain/sensitivity setting; if the HU only produces a low voltage signal, the amp would need to be more sensitive (read –have more GAIN) to produce the same power.  The input “gain structure” of different manufacturer’s amps is…well different.  Gain is NOT going to be the same with all amplifier manufacturers, and not even necessarily the same between the different lines of amplifiers from the same manufacturer.

Basically having the gains set TOO high causes all sorts of issues.  If input clipping occurs to rapidly (by having the input gains CRANKED!! Or set TOO high) , the systems distorts quickly, eccessove hiss at higher levels (this is the tell tale sign that gains are set TOO high - system gets loud very quickly) and the amplifier gets really HOT .....really FAST. GAINS are set to HIGH!! Go back and re adjust. 

What do the voltage markings on the gain setting mean?

Some gain controls have markings with ‘voltage’ to use as a guide. These voltage settings suggest to you what audio signal input voltage is required to make the amp produce full power. You’ll note that with a high gain/sensitivity setting, the marking may read 0.5V; this makes sense because the amp needs to be more sensitive to respond to a low voltage signal in order to produce full power. Whereas a low gain setting may have a marking of 4V; with such a high input voltage, the amp needs to be far less sensitive to produce full power. Some amplifiers may also have a “range” switch to accommodate signal levels from either preamp level or speaker level inputs. Typically speaker level inputs are higher voltage, but may also clip sooner depending on what IC “chip” amplifier is used to drive the output. In general, preamp level signals don’t go through fewer components in the headunit and are often recommended for connecting to the amplifier.

What RCA preout voltage does my HU produce?

Unless you have sophisticated measuring equipment like an oscilloscope, you will not know what voltage the RCA signal is from you HU, at least not without knowing where it begins to distort.

Handheld Oscilloscope

TPI440

The advertised voltage found in the specifications on your HU refers to the output signal under test bench conditions: usually by playing a constant signal like a test tone (sine wave) at a fixed frequency and it does not always mean that the advertised specification for output voltage is the same amount of output voltage that’s “clean” and free of distortion. Test tones are obviously very different to conditions to playing actual music. Music is very dynamic, meaning it is constantly changing between loud and soft whereas the test tone is always the same, varying only in amplitude (which is the “volume” of the signal, measured in volts AC.

It is important to realize that the RCA preout signal voltage, when playing music is far lower than if playing a test tone at the same position of the volume knob. Therefore, while a HU may feature ‘4V preouts’, when you play music the ‘average’ voltage may in fact never reach beyond 1~1.3V…or lower. Sure, it may peak as high as 4V, but never reach that level in a sustained manner, at least under music conditions.

Of course, these maximum “advertised” output signal voltages are only achieved when the HU volume is turned up to full (wherever that may be!). Using a low volume setting, as you would for normal listening, the signal voltage is far less again.

The implication is that the gain setting on the amplifier must be much higher than predicted. You should expect a 5 dB to 10 dB ‘overlap’ in voltage.

For example, a HU claiming ‘4V preout’ signals will only produce an average of 1 to 1.3V when playing music and at full volume, which is 10dB down and less than the predicted 4V output.  The gain setting remains true however; that is, if you set the gain to the ‘1V’ marking, the amp will produce full power when the HU delivers 1V with an oscilloscope measuring this with a 1,000 Hz sinewave.  Or 2 volts, or 3 volts and so on and so forth.

Simply remember the Gain Pyramid –

Ideally, you prefer to have ALL the gain at the beginning of the signal chain and the least gain necessary at the end. A 4 volt preamp output HU is WAY better than a 2 volt preout HU!!).   Amplifier gains set at absolute minimum are preferred because the overall result is a lower noise floor of the entire audio system!!  This means less audible hiss when the amplifier gains are minimized AND optimized. Subwoofer amplifier gains can be somewhat higher because of ambient noise floor (road noise, etc) and the fact that subwoofers generally are positioned further from the listener; hence they make it harder to hear the audible hiss of the slight increase of gain.

Input Gain Pyramid

Why set the gains properly?

There are several reasons to set the gain control properly:

1. The wider the range over which you can use the volume control on the HU, the finer the control you have. There’s no point having the amps reach full power with only 30% on the headunit dial where every little step produces a large volume difference. Therefore, you want full volume to be achieved when the volume control on the HU is full (100%) or as close to 100% as possible, the difference being where the signal distorts if it does so before the headunit reaches full volume. You know the gains are set incorrectly when the system gets very loud…VERY quickly and the master volume control is not near its limit.  As an example, if the HU readout for volume goes to 35 as its maximum volume output and at a volume setting of 10 the system is VERY loud,  99% chance that the gains on the amplifiers (or signal processors in-between) are set too high (meaning – incorrectly!)

2. To avoid overpowering speakers. Every speaker has a power handling limit; if it is fed a continuous amount of power beyond this, it will be at risk of having the voice coil overheated and permanently damaged. Gain settings can be used to limit the amount of power being delivered to within safe operating levels.  ANY voice coil that is “blackened” or burned has been thru intensive ABUSE. This is NOT a flaw of the speaker, or a design issue.  It is simply ABUSE!!!!

3. To avoid ‘clipping’ the amplifier. Clipping occurs when an amplifier is pushed beyond its design limits; this limit is the maximum clean output power the amp can reliably produce. Beyond this, the output signal becomes highly distorted, and is referred to as being ‘clipped’. Clipping is very audible with test tones and difficult to mistake. Although it’s a bit less obvious to identify clipping with the varying nature of music signals, by the time you DO hear clipping with the music signal it’s going to be severely distorted!  If the gain is set too high, the amplifier will reach full power when the volume control has not reached full; if the volume control is turned up higher, the amplifier is now pushed beyond its design limits into clipping (which means it’s introducing a distorted signal into the audio path). By reducing the gain setting, the amplifier will never reach clipping despite the volume control being turned up full. Note that clipping does not necessarily mean the speakers will be overpowered; therefore it is not always dangerous for the speakers (see later).

4. To achieve a nicely balanced system between front and rear speakers, and the subwoofer, their respective levels need to be matched. Using correct gain setting procedures is a useful means to achieve this.

What happens if the gain is set too low?

If the gains are set too low, the amp will not be sensitive enough to reach full power. For example, if the gain is set where the amp requires an input signal of 3V to produce full power but the HU only delivers 2V even at full volume, the amp will never reach full power. This is wasting the potential of the amplifier.

However, this may still be required if you are to achieve a better balanced system, or more importantly, to avoid overpowering the speakers or subwoofer.

As such, a ‘low’ gain setting can be used to cap power output from the amplifier, or match it with the outputs of other amplifier channels in the system. It’s much better to back off the gain of the louder amplifier (or channel) then to try and take an amplifier channel that’s lower in volume and subsequently dial up the gain to try and match. What happens? Well you already know what could happen, and it’s unlikely the results of added hiss, possible clipping, and overpowering can really help things. Remember it’s better to cut gain from the louder amplifier..

What happens if the gain is set too high?

This has been discussed above. The problems encountered include the risk of overpowering speakers and causing clipping, as well as excessive system “Hiss”.  Excessive system hiss is increasing the noise floor, which is the lowest audible noise the audio system makes when there’s no signal passing through. When gain is excessively high and the volume is very low, audio systems with a high noise floor have a real apparent hiss.  In other words if your system “hisses” and it is very obvious, go back and check you gain adjustments again. Chances are you’ve introduced too much gain in at least one stage of the signal path.

What is distortion and overpowering speakers and subwoofers?

In audio, distortion is a music signal (electrical or acoustic) that is less than 100% identical from the original. Even though an amplifier’s job is to “amplify” the signal, it’s only to increase the signal voltage, not to “color” it in any way. Where the CD recording is the ‘original’, distortion may occur when this data is converted from digital to analog, as it passes through the controls (preamp) of the HU, along the RCA signal cables, into the amplifier, out to the speakers and in the reproduction by the speakers themselves. Some is audible and this should always be considered ‘bad’, if not only to our ears, but also to the components. Very small amounts of distortion are common as the equipment operates and does its thing, but you want to avoid adding in severe distortion by incorrect adjustments of input gain levels.

Important forms of distortion to be aware of include:

1. Over-excursion of the cones of speakers and subwoofers from being pushed beyond their physical limits. This typically occurs when small speakers (e.g. 4 to 7” diameter) that are part of the front-speaker setup are fed too much bass, especially when delivered a ‘full range’ signal. By using a HP filter to remove bass, it will greatly improve the power handling of the speaker and avoid over-excursion.

2. Clipping of the amplifier. Discussed above, clipping occurs when the amplifier is pushed beyond its design limits of producing ‘clean’ power and the output signal becomes distorted. This transition is typically sudden and harsh, but some amps have soft clipping, which is far less noticeable. Other amplifiers feature a clipping warning system, which is commonly an LED warning light.

Overpowering of speakers occurs when either they are pushed to over-excursion or the power being delivered exceeds their power handling. Every speaker and subwoofer will have a power handling designation specified by the manufacturer, and usually marked onto the speaker itself. You should always refer to the ‘RMS’ power handling specifications for the speaker, not necessarily the peak, MAX, or “if lightning strikes”inflated ratings.

It is possible to cause over-excursion without exceeding power handling. For example, a 6” speaker may have a power handling of 50WRMS, but if fed a signal with Subbass (below the Fs or free air resonance of the speaker) it may over-excurt and distort with only 30WRMS of power.

Usually a speaker or subwoofer audibly distorts if it is overpowered. This is a warning to back off or risk permanent damage!

Clipping can cause overpowering and is therefore dangerous for speakers. It is a common cause for burning out voice coils.

Clipped Oscope Signal

 







Oscilloscope with unClipped and Clipped waveform

 A clipped audio signal is typically far more powerful than a clean, unclipped audio signal, quickly reaching double the power of the clean signal. It is because of this rapid transition that people often misperceive the actual issue.  The output of the HU clipping can cause the amplifier to clip LONG before full power output of the amplifier. Setting gains properly can avoid clipping!  You need to know WHERE your HU clips at

Note that clipping, per se, is not dangerous for the speaker. It is the actual electrical power of the signal (representing a value of heat) that causes the overpowering. For example, an amplifier may produce only 100WRMS of power, beyond which it will clip. If clipped, the signal may reach around 200WRMS. However, if the subwoofer it drives has a power handling rating of 300WRMS, it will not be overpowered or at risk of seriously overheating. Therefore, the subwoofer will happily reproduce a clipped signal of 200WRMS all day long; it will just sound terrible and the amplifier may overheat from delivering that clipped signal!   But doing this for long periods of time is VERY  destructive (see the voice coil below)

So understand that clipping is a sign that the amp is being pushed beyond its limits; that the onset of clipping causes a rapid increase in power output, albeit highly distorted; clipping does not necessarily mean the speaker or subwoofer will be overpowered.  The result of clipping is pretty obvious.  For example burned voice coils of speakers (typically subwoofers)

 Below is a picture of a GOOD voice coil and a BURNT voice coil
 

VC-BURNT-VS.-NEWBURNT Voice Coil

This is NOT caused by a “design” error, this is caused by abuse!!  Period.  It takes a LOT of time and abuse to do this.  It is NOT instantaneous damage!!  Ya gotta work at this stuff!!!!!

Remember that what comes out of an amplifer is A/C volts (Yeah...like off the wall A/C voltage!! Same deal!!)   And a voice coil is simply a tube with thin copper wire glued to it.   You put A/C voltage on thin copper wire for long enough and you get HEAT.  Heat is what kills subwoofers.  Well...that and who ever is tuning the volume control UP.    The idea that you have a 500 watt RMS woofer and a 500 watt RMS amplifer somehow meaning that it is "magically" matched is not happening!!   And therefore you shouldnt be able to hurt this woofer because its "matched" to the amplifer...and in NO WAY could you hurt the woofer (no MATTER what you do!!) ...is..Well...RIDICULOUS!!! 

Thats like buying a brand new Z7 Corvette and driving it around for an hour  - bringing it back to the Corvette dealer and complaining that the car "ate" the tires off....It wasnt YOU doing "donuts for a hour that did it.  It was THE CAR that did it!! Not me!!    Righttttt!!

AC voltage on thin copper wire will get HOT.  Period.  Having a BIGGER voice coil (meaning going from a 2" voice coil to a 3" voice coil)  buys you almost 50% more heat dissipation.  Meaning a HIGHER RMS rated woofer.  This, by the way, does not mean a BETTER woofer.  Just higher power handling.  The picture shows a GOOD voice coil and a BAD voice coil.  The difference is HEAT.  The voice coil on the right has been heated up and heated up over and OVER again..breaking down the glues that hold the copper to the voice coil "former".   This is PLAIN AND SIMPLE ABUSE.  Not a "defective" or bad woofer.  The user has abused this woofer many MANY times at a high power levels causing a LOT of heat (more than likely  - CLIPPED) .   Voice coils do not "un glue" themselves for NO reason.


How do I best utilize crossovers (filters)? ) this is called "FREQ" on many of our amplifiers

Crossovers are defined by the frequency at which they are set and how “fast” they filter out the unwanted audio signal (slope rate, also called “roll-off”), which is why another technical name for a crossover is simply “filter”. Depending upon the part of the audio frequency spectrum you wish to filter out, the crossover can be a lowpass (LP), high pass (HP) or even an band pass (which is a LP and HP combined) type of filter. Nearly all amplifiers include an active crossover, and most are ‘variable’. This means you can adjust the frequency from the point at which the filter takes effect. Most slopes are fixed, commonly of 12dB/Octave effect. The higher the slope rate, the faster the filter.  Meaning that 6 dB is relatively slow, 12 dB is faster 18dB is faster still and 24 dB is really fast (or steep, depending on how you want to look at it). Filter alignments can be either the most common – Linkwitz/Riley type or Butterworth type (or M derived or Bessel, or a number of other filter types). These alignments have particular properties of how they create their slope “shape”, particularly where the relationship of two filters will be used near one another.  I PERSONALLY recommend go SLOW, NOT fast on crossover slopes.  Meaning 6dB or 12dB slopes.  Especially if drivers are located far from each other and not millimeters apart!  The closer the drivers (speakers) are the faster the slopes you can use (18dB/24dB)  The farther the drivers are apart from each other, FOR EXAMPLE midbass/woofer in door and tweeter in the "A" Pillars or on top of the dash or in the window sails for example - then go SLOW -   6dB or 12 dB.  

You should select the filter to suit the speakers and subwoofer, and also set them to achieve a nice blend between front, rear and subwoofer.  Generally speaking regarding the slope, the farther apart the speakers in a frequency range (such as a mid and tweeter component set), typically you would want a shallower slope (for example 6-12 dB per octave). Generally speaking regarding the frequency set point, if it is a small speaker (4 inch or 5 ¼ inch) and the crossover HP filter frequency is set too low (like 40-70 Hz for example) the speaker can be fed too much bass. This excess of bass in that small speaker will cause premature distortion from over-excursion and reduce its power handling. Setting a HP crossover point for speakers too low then, may limit how loudly you can run the system because the speakers start “barking” at you. In other words they are excerting to far,  or "over excerting" (in other words exceeding Xmax - or linear throw) 

Other schools of thought have been that you should always start your crossover at least one octave above the speaker’s Fs (Resonant frequency –or Fs)  And an octave is DOUBLE or HALF any frequency in the audio world. 

The choice of frequency where the HP filter is set is a compromise: it is always better to have MORE midbass (70-150Hz range depending on the physical properties of the speaker itself) from the front speakers, asking too much of them will diminish their power handling. It may also ‘muddy’ their sound because they struggle to maintain the clarity of the higher frequencies whilst reproducing the midbass. Setting the HP filter slightly higher will improve power handling at the expense of midbass.
 

NOW THAT YOU'VE READ A BUNCH OF THEORY - LETS DO SOME PRACTICAL SETUPS!

First , what source do you use for music?  Do you use CD's?&a