# Set the gains on the head unit first..



## gstokes (Apr 20, 2014)

I don't think we hit on this enough, most people are aware about setting the gains on the amplifier but sidestep setting the gain on the head unit first.
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Just like the main amplifier driving the speakers the receiver has a built-in amplifier and the volume knob (gain control) must be adjusted for maximum signal strength (without clipping), the same way you calculate the required voltage at the speaker terminals of the amplifier you do the same with the head unit..
Some people say set the volume knob at 90% and other people say set the volume knob at 75% before adjusting amplifier input gain/s, they're both wrong and i've been guilty of giving the same advice, you adjust the volume knob for the maximum unclipped signal..
If your head unit makes 15 W/channel @ 4 ohm then it would be 15 x 4 = 60, square root of 60 = 7.74V, connect the DMM or oscilloscope or SMD DD-1 to one channel of the head unit (speaker wires, not the RCA's), set the EQ flat, play a 10kHz test tone or sine wave and rotate the volume knob until the DMM reads 8VAC or the oscilloscope shows an unclipped signal or the SMD DD-1 indicates no distortion, mark the spot and don't ever turn the volume knob (gain control) past that point, you have adjusted the head unit for +/- maximum unclipped signal..
The head unit is a full-range source and the center of the bandwidth is (roughly) 10kHz, actually it's 9.9kHz for the bean counters..

Edited for content..

If you are using line level/pre-out/RCA's it makes no sense to adjust the speaker level outputs on the head unit.. 

Instead, use an oscilloscope to determine if and/or when the line level signal becomes clipped..
or.. 
Use the SMD DD-1 to measure distortion at line level..


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## legend94 (Mar 15, 2006)

Happy to see you start this as I am just getting a new install going today actually. So far I just have the mids and tweets going off of the amp.

As a test I just set the gains on the amp to minimum and figured I could adjust them after I made sure everything was working.

So now the head unit is at 60 percent at the highest level I want to listen at. Now what?


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## ATOMICTECH62 (Jan 24, 2009)

A head unit will never read 14.4 volts at the speaker leads.
7 -8 volts is the most they can do.

The reason?

There are no HU's that do 50watts RMS.They would need to be big as a 50x4 amp and have a Power supply built in.
Most HU's do about 12-15 watts RMS.


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## gstokes (Apr 20, 2014)

legend94 said:


> Happy to see you start this as I am just getting a new install going today actually. So far I just have the mids and tweets going off of the amp.
> 
> As a test I just set the gains on the amp to minimum and figured I could adjust them after I made sure everything was working.
> 
> So now the head unit is at 60 percent at the highest level I want to listen at. Now what?


60% is fine, if the amplifier in the head unit is not clipping at the 60% mark..
Some head units begin to clip before the 50% mark is reached and others won't clip until the volume is set to the 95% mark, all depends on the head unit..


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## gstokes (Apr 20, 2014)

ATOMICTECH62 said:


> A head unit will never read 14.4 volts at the speaker leads.
> 7 -8 volts is the most they can do.
> 
> The reason?
> ...


I was being hypothetical and did say "if".. it makes 50 wrms per channel, it was used as an example but you took it literally..

Maybe I should have said peak and not rms, or just left out peak and rms altogether and just said voltage ?


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## Weigel21 (Sep 8, 2014)

I agree that many tend to overlook the step of finding the HU's maximum clean output level, but I disagree with your method to finding it.

Using a DMM to set the HU to reach a particular output VAC does NOT guarantee the output is distortion free or even unclipped. 

You mention using a DMM for setting the output to a particular VAC, but fail to mention what one should use as the source material, which a sine wave test tone is the common source material. On top of this, you fail to mention a frequency best to use. 

You also fail to recommend the use of a True RMS DMM or that all settings on the HU should be set to flat to achieve the lowest distortion. 

Granted, there are many different views on all of this and my own aren't necessarily the "one and only correct way".

Some recommend using an O-Scope or distortion detecting device like the DD-1.

Me, I play various test tones ranging from 1kHz down to 50hz listening to the speakers/sub(s) as I dial up the volume seeking the point where the tone changes. From what testing I've done (with the aid of an O-Scope), I've concluded my ears seem capable of detecting 1%THD, but only when I am well rested and before my ears have had a chance to desensitize throughout the day. If I wait until evening, 1%THD seems difficult to detect, if not impossible for my ears to detect. 

Anyways, that's my 2 cents.


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## Weigel21 (Sep 8, 2014)

And I didn't go through all the procedures I follow when finding maximum clean volume or setting gains, but there are some very good threads on such here if one looks.


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## jb4674 (Jan 29, 2015)

It's good advice but, who is going to pull out a dmm and go through all those motions?


Sent from my iPad using Tapatalk


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## gstokes (Apr 20, 2014)

Weigel21 said:


> I agree that many tend to overlook the step of finding the HU's maximum clean output level, but I disagree with your method to finding it.
> 
> Using a DMM to set the HU to reach a particular output VAC does NOT guarantee the output is distortion free or even unclipped.
> 
> ...


Granted, i did make some mistakes and will correct..
I didn't go through the whole procedure because i assumed people would know a test tone is required and setting the EQ flat is done before setting the gains on the main amplifier and most people don't have an o-scope and sinced the head unit is a full-range source i would use 10kHz sine wave or test tone to set the gains, i am learning..
It was intended to be more of an addendum than a complete guide, my bad..


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## Velozity (Jul 6, 2007)

I'm confused about the target of this thread.

If using an external amp the head unit should be tested to find it's maximum usable unclipped level at the pre-amp outputs. The distortion of the internal amp is irrelevant if you're not using it (assuming it even has a built-in amp as most higher end units do not). 

If you are only using the internal amp in the HU then there's no gain except the volume control (and whatever built in EQ boosts there are). So you turn it up as loud as you want depending on the source material and how much distortion you can stand.

If you are using both the internal HU amp and an external amps you have to set the gains to the maximum unclipped level of the weakest amp so that you don't have some speakers distorting and some not.


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## Weigel21 (Sep 8, 2014)

It's also worth noting that the internal amplifier of a HU will produce distortion much sooner than the preamp outputs, which if one is running amps for everything, then the method laid out in the first post is useless. 

Not trying to be disrespectful, the OP makes a valid point, it's just that the information seems a little misguided.


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## gstokes (Apr 20, 2014)

Weigel21 said:


> It's also worth noting that the internal amplifier of a HU will produce distortion much sooner than the preamp outputs, which if one is running amps for everything, then the method laid out in the first post is useless.
> 
> Not trying to be disrespectful, the OP makes a valid point, it's just that the information seems a little misguided.


The information has been edited..

How would one use the RCA's/line level to set the gains, is it possible ?


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## Velozity (Jul 6, 2007)

gstokes said:


> The information has been edited..
> 
> How would one use the RCA's/line level to set the gains, is it possible ?


Yes you can use an o - scope or SMD distortion detector. You can also use your ears if you hook up a power amp and one speaker and set the amp gain at minimum. Then play 0 dB or -10db test tones (sine waves).


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## gstokes (Apr 20, 2014)

Velozity said:


> Yes you can use an o - scope or SMD distortion detector. You can also use your ears if you hook up a power amp and one speaker and set the amp gain at minimum. Then play 0 dB -10db test tones.


I gotcha, clipping is clipping no matter where it's measured, even though i'm taking an asswhipping I'm still glad I started this thread..

My MB quart has line level out so amplifiers can be daisy chained, this is good info..

To be clear, when I say built-in amplifier I am referring to the output transistors and not some additional amplifier inside the head unit.. 

Thank-you :thumbsup:


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## ATOMICTECH62 (Jan 24, 2009)

You brought up a point I don't remember seeing discussed before and I have ran into it a few times.

When using the internal amp in the HU along with an external amp it is best to get them to clip together.Most HU amps will clip at around 50-60% max volume.So this means getting the max preamp voltage might not be possible from the deck before the internal amp clips.
But unfortunately there really isn't any way to do it without a scope.But if I had to do it on the fly I would set the amps to clip once the HU reached about 6-7 volts RMS.


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## brumledb (Feb 2, 2015)

A couple of nice tutorials on the subject.

Gain Settings


http://www.diymobileaudio.com/forum/how-articles-provided-our-members/51435-setting-gains-w-o-oscilloscope.html


http://www.diymobileaudio.com/forum/how-articles-provided-our-members/542-tutorial-gain-setting-amplifier-power-usage.html


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## gstokes (Apr 20, 2014)

brumledb said:


> A couple of nice tutorials on the subject.
> 
> Gain Settings


I'll be damned but Adam even misguides people with his article..
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Line 6) from setting gain with DMM..

6 - Set your head unit's volume somewhere around 3/4 of max to ensure it isn't clipping and remember this volume setting..
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How can he be sure it's not clipping at 3/4 volume


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## brumledb (Feb 2, 2015)

From all the reading I have done on the subject for people who do not use an oscilloscope setting the H/U to 75% seems to be the accepted approach.

I just edited my other post. Check out the last link.


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## Weigel21 (Sep 8, 2014)

Late to respond, but it seems you've gotten responses very similar to what I've have said anyways.

I'd like to mention that I've found (both by ear/test tones and later confirmed with a Scope) that my Sony DSX-S200X's internal amplifier produces 1%THD at volume level 20 (so volume 19 is the loudest clean with the internal amp), but the preamp outputs seem to remain clean even at full tilt (EQ set to flat and all other sound shaping features deactivated). IIRC, as I haven't used the internal amp for two years. Either way, it was distortion at 20 or 21 with the loudest clean volume being 19 or 20. Still, that's less than half volume before the internal amplifier produced 1%THD, dispite the HU being 

This actually surprised me, as I honestly thought the HU's internal amplifier would be able to produce more power before distortion in excess of 1%THD and I didn't figure the preamps would remain distortion free at full tilt.


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## Hugg727 (Sep 17, 2009)

Good thread.......quick question.

How do you suggest setting the gain on a factory head unit that has the MOST bus? I have an Audi and will be using a mObridge DA1 to tap into the stock radio signal. Do I just assume that the output is clean at 100% because it is digital?


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## legend94 (Mar 15, 2006)

Weigel21 said:


> Late to respond, but it seems you've gotten responses very similar to what I've have said anyways.
> 
> I'd like to mention that I've found (both by ear/test tones and later confirmed with a Scope) that my Sony DSX-S200X's internal amplifier produces 1%THD at volume level 20 (so volume 19 is the loudest clean with the internal amp), but the preamp outputs seem to remain clean even at full tilt (EQ set to flat and all other sound shaping features deactivated). IIRC, as I haven't used the internal amp for two years. Either way, it was distortion at 20 or 21 with the loudest clean volume being 19 or 20. Still, that's less than half volume before the internal amplifier produced 1%THD, dispite the HU being
> 
> This actually surprised me, as I honestly thought the HU's internal amplifier would be able to produce more power before distortion in excess of 1%THD and I didn't figure the preamps would remain distortion free at full tilt.


What is the max volume on the head unit for comparison?

This is a great thread and I'm glad you are making use of your so are time, op.


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## gstokes (Apr 20, 2014)

legend94 said:


> This is a great thread and I'm glad you are making use of your time, op.


Thank-you, it sure beats laying around feeling sorry for myself..


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## gijoe (Mar 25, 2008)

Hey gstokes, do you have any examples of head units that clip at 50%? I'm not calling ********, but all of the decks I have used in the last 10 years have not clipped until max or a click or two below max. They have all been Pioneer units, 880prs, 80prs, and P99RS. Perhaps I've been a bit lucky, or I've just done a good job buying quality head units, but are there really head units that clip at 50%? That sounds absurd to me. 

Despite some complaints about Pioneer head units, their pico fuse issues and clunky interface, it seems that if other head units are clipping so low on there volume knob, Pioneer really has done some things right that other companies aren't doing. 

Again, not to call ********, but have you tested many head units for clipping? Which ones are clipping at 50%, 75%, etc.?


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## gstokes (Apr 20, 2014)

gijoe said:


> Hey gstokes, do you have any examples of head units that clip at 50%?


No I don't but this what I have heard from other online sources, perhaps the info is outdated and not pertinent to modern head units and not to call ******** but have you evaluated every head unit that has been built in the last 25 years and are confident that none of them clipped at 50% volume ?
I didn't think so either..


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## gijoe (Mar 25, 2008)

gstokes said:


> No I don't but this what I have heard from other online sources, perhaps the info is outdated and not pertinent to modern head units and not to call ******** but have you evaluated every head unit that has been built in the last 25 years and are confident that none of them clipped at 50% volume ?
> I didn't think so either..


Again, you're reading into what I said. I never claimed that there weren't any head units that clip at 50%. You made the claim that there were, and I'm just curious if that's true. 

I agree that your method should be considered when setting gains, sending a signal that is clipped by the head unit to an amplifier isn't something that you want to do. 

I just think you may be assuming a problem that isn't as typical as you think. I know not all head units are created equal, and there must be some that clip earlier than you would want, but you're the one that said "some head units begin to clip before the 50% mark is reached" I'm just asking if that is actually true. 

I have not evaluated every head unit from the last 25 years, nor did I ever claim you were wrong. You might be right, 50-75% may be pretty normal, I don't know, but I don't believe it is. 

Again, your method is solid, you don't want to send a clipped signal to the amp. But, I have a suspicion that setting the head unit to 75% will avoid clipping most of the time. 

I re-read my previous post, and I think it was fair. I try to chose my words carefully. In summary, I suspect you are making a mountain out of a mole-hill with this problem, and head units that clip at 50% are likely very uncommon, but as I mentioned from the beginning, I may be wrong. I've simply asked you, in a respectful way, to show some examples to support your claims. I'm as open to learning something from you as I am learning from the veterans in this forum.


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## gstokes (Apr 20, 2014)

gijoe said:


> Again, you're reading into what I said.


x 2, we are both guilty of reading into what the other person said..
:beerchug:


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## Alrojoca (Oct 5, 2012)

This is a question for the manufacturers, asking for specific models. I read some complaints with Alpines. With my current amps, no issues since it is done by the amp itself, automatic.

when I use another amp, I had major issues setting the gains to the point where the target voltage was 22 volts and I ended up with like 7-8 volts in order to get good clean sound. This makes me believe at 80% volume the voltage was clipped, therefore I could not get any clean sound unless I set the gains with a DMM for under 8 Volts. Even though the sound was great with headroom and everything. It makes me wonder if say I tried at 60% volume, then simply increase the amp's gain dial to get at least 20 volts out of the 24V target would have made it easier and make sense to me. On the other hand like someone else mentioned here I think, the sub's pre outs gave me no issues and gave me Voltage readings that really made sense.


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## Weigel21 (Sep 8, 2014)

Hugg727 said:


> Good thread.......quick question.
> 
> How do you suggest setting the gain on a factory head unit that has the MOST bus? I have an Audi and will be using a mObridge DA1 to tap into the stock radio signal. Do I just assume that the output is clean at 100% because it is digital?


Never ASSuME anything. Chances may well be good, but it's best to find out for yourself and not go off hearsay. 

So, how can you find out yourself? Easy, if your ears can detect 1%THD. This article covers what distortion is and about 1/3 of the way down is a test which plays a 400Hz sine wave at various distortion levels. If you can detect when it begins to play 1%THD, then you can find your HU's maximum clean volume level by playing various test tones in your car. word of caution, it can/will get LOUD. I recommend using some ear plugs or something to lessen the severity of the SPL levels to you ears. Depending on how sensitive/good your hearing is, the ear plugs will not hinder one's ability to detect 1%THD, or at least mine were not, but only when I do said testing early on in the day before my hearing becomes desensitized or fatigued. May want an extra set of ears to help. 



legend94 said:


> What is the max volume on the head unit for comparison?


The Sony DSX-S200X goes up to volume level 50. The internal amplifier produces 1%THD at level 20 or maybe 21, been a while to remember for sure which it was, as I run external amps. 

The Preamp outputs remain clean at full tilt from what my ears could tell and what my cheap DSO Nano scope showed. 


@gijoe
Your HUs have all been higher quality units thus far, so it's not surprising they remain clean at full tilt with the internal amplifier. Testing has been done with scopes and the DD1 on various higher end HUs and all of them (IIRC) remained distortion free at full tilt for both the internal amp and preamp outputs. 

I have been around lower quality Pioneer HUs and they do display distortion from the internal amplifier. My Brother-in-law picked up the recently posted $50 Pioneer from BestBuy and it's internal amplifier seemed to produce distortion at level 51 (think it goes up to 62). Testing was done with test tones and unfortunately, it was later in the day when I was over there, so the HU may produce distortion sooner or it may have been our ears playing tricks on us. What I mean is it could have been vibrations caused by the speakers or just the speakers distorting and not the HU. Didn't take my scope to double check. 

My sister has an Alpine CDE-124SXM I bought and installed for her in her 02' Grand Am. Her car has the Monsoon system and she had no plans to buy new speakers and an amplifier, nor did I have any desire to do such for her. So, I bought an integration harness to install it which used the speaker leads to send the signal to the Monsson amp. I was able to confirm by ear and my Scope that the HU could not be dialed past level 9 before 1%THD was present. However, volume level 9 seemed loud enough to me for daily listening, she said it was plenty loud for when the kids were in the car, but could see dialing it up louder when alone. Not sure why that was exactly, I ASSuMEd it was because the Monsoon HU was a dead head and the output voltage was quite low as opposed to the internal amp of the Alpine. Anyways, she went ahead and dialed it up and at level 13, I wanted to get out of the car. At volume level 15 she said it was plenty loud for any situation she could foresee. Still, I told her nor to go past level 10 unless she wanted to be buying new speakers before too long. Last I knew, she hasn't, but she now has a sub in the car which is just waiting to blow. Installers put a ported 200RMS sub setup in the trunk powered off a JL XD200/2. I wanted to make some changes, but my cousin paid for the gear and installation and wanted me to leave it alone. Amp is set to LPF 120ish Hz gain is dialed up to 7/8 max. No idea what the HU volume was at when the gain was set, but if it was level 10, that setting MAY be ok. Still, the HU has a LPF set at 80Hz, so WTF?! I wanted to switch the amp to HPF and set it at the lowest setting, which is 50Hz, as I know not what the enclosure is tuned to, sub being used in the size enclosure being used is recommended to be tuned to 40Hz. 

Sorry, getting off topic, end of rant.


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## Alrojoca (Oct 5, 2012)

Nice DMM, this video shows higher than rated voltage and no clipping at vol 35, and in another thread I posted back in July Erin H also confirmed he benched tested the 149BT at max volume of 35 with no clipping. 

Also in that thread it was mentioned that Alpines tend to no clip even with the EQ bands at higher levels, some kind of circuit. 

Maybe the 149 puts less voltage than the 148 and 147 or maybe this guy's DMM is a bit off. The main thing either 4.7V or 4 V as Erin said, no clipping at volume 35 with newer Alpine head units. 

I think he was testing the sub's RCA's on the video since he was using a 40Hz test tone, and those measured 
4.7 V, Erin bench tested the main channels and confirmed 4V, I am happy with that. 


https://www.youtube.com/watch?v=QRZhbZNyuXk


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## Weigel21 (Sep 8, 2014)

Can't personally comment on newer Alpine HU's, but the lower end models of just a couple years ago did not remain distortion free at full tilt with the internal amplifier and some of the entry level models years back didn't remain distortion free on the preamps either. 

All the models you listed, the 147bt, 148bt, and 149bt are their mid to upper level units. 

Now you claim new Alpine's do not clip. Well, this video says otherwise. The new CDE-195BT is shown to produce distortion at volume level 30 on the sub channel preamp with a 40Hz test tone on the bench test in the video. Granted, we know not the kind of voltage the HU is getting, but Alpine even lists the preamp voltage as "Pre Output Voltage (Before Clipping): 2V / 10k ohms".


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## scclarke1989 (Dec 13, 2021)

Hugg727 said:


> Good thread.......quick question.
> 
> How do you suggest setting the gain on a factory head unit that has the MOST bus? I have an Audi and will be using a mObridge DA1 to tap into the stock radio signal. Do I just assume that the output is clean at 100% because it is digital?





Weigel21 said:


> I agree that many tend to overlook the step of finding the HU's maximum clean output level, but I disagree with your method to finding it.
> 
> Using a DMM to set the HU to reach a particular output VAC does NOT guarantee the output is distortion free or even unclipped.
> 
> ...


Whoah Bros.....
Do we really have to get so incredibly technical with the ****? EVERY TIME I get on here and do some reading, I get totally mind ****ed. It's absurd.
Don't get me wrong, I have an immense amount of respect for a Craftsman who takes pride in his work and has immense knowledge of his craft.

But at the end of the day, we're talking about sound. Nobody hears the **** exactly the same and the bottom line is generally "whatever sounds best to you"
I'm a professional electrician and anything with wires is a hobby for me. In the past couple of years I've done a lot of tinkering into the world of sound. Made some pretty cool **** along the way. But you guys get me depressed.
Can't a mfer just buy an amp and some subs, build a box, hook that **** up to the rear speaker wires on a 25 year old head unit, maybe change out or ass some speakers, set everything by his own half deaf ears, and just be happy and feel accomplished and content in the fact that he's GENUINELY PISSING OFF his neighbors?

I just feel like the national style tech lording-overness that is commonplace on these threads just takes all the fun out of something.

You guys talk about **** that is so over my head sometimes. And the more I learn it's like the more I realize I don't know jack.
The terminology alone has taken a while to swallow.

Are any of you here reading this not still amazed at the fact that sound, like full on orchestra, rock concert sound and coherent vocals, comes out of these things made with magnets and copper coils and ****in paper?

It doesn't matter how technical you get with it, it's still like frikin magic. And nomatter how many terms we come up with to describe it, manipulate it, understand it, we don't. In essence. Not really.

Sound itself is amazing.
Let's enjoy it and stop molesting it shall we?

Am I wrong or am I wrong?
Totally wrong, I'm sure, to you guys.

But I don't care I can't hear you over my magnets and paper circles bahahahaha


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## dumdum (Feb 27, 2007)

scclarke1989 said:


> Whoah Bros.....
> Do we really have to get so incredibly technical with the ****? EVERY TIME I get on here and do some reading, I get totally mind ****ed. It's absurd.
> Don't get me wrong, I have an immense amount of respect for a Craftsman who takes pride in his work and has immense knowledge of his craft.
> 
> ...


Holy old thread from the dead Batman

It’s only so good because of threads like this, if you don’t have a clean source you will never have a clean final output


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## reid1boys (Nov 15, 2010)

Thanks for this. I am about to install some new mids and tweets. I have good stuff in my Silverado, but im not happy with my sound at all. It is time, over Christmas break to dial my system in to get the sound im looking for. My 12 inch Klipsch powered sub in my garage sounds way better than my two alpine 12" type R's powered by a Zapco Reference 1100.1.


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## reid1boys (Nov 15, 2010)

Question...... Im gonna dial things in over Christmas break. I would love to use a SMD DD-1 , but damn, 200 bucks to dial in a system that is then gonna basically sit for years. Im about to turn 52, Im not out changing systems every year like when we were kids. Ive got stuff that is good enough to last my truck for years. Anyone know of a place that rents an SMD DD-1?


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## reid1boys (Nov 15, 2010)

scclarke1989 said:


> Whoah Bros.....
> Do we really have to get so incredibly technical with the ****? EVERY TIME I get on here and do some reading, I get totally mind ****ed. It's absurd.
> Don't get me wrong, I have an immense amount of respect for a Craftsman who takes pride in his work and has immense knowledge of his craft.
> 
> ...


Its your stuff, you can do whatever you want to do. Im 51 years old.... at age 16 I went out and bought 4 becker 10inch subs and tried to hook them up to an eq booster. Needless to say, that didnt work out so well. Since then, I read and try to learn as much as I possibly can about this hobby because of a couple of conclusions I have come to over my years of tinkering in this stuff.

1) GOOD stuff is not cheap. I found that out when I thought I could get some serious bumping off of those 4 10" Beckers hooked up to that cheap EQ booster.
2) Frying expensive stuff because you just hooked up some wires from your batter to your amps and from your amps to the speakers and turning that crap up loud to bother your neighbors will result in your expensive, good stuff getting fried.
3) Frying your expensive stuff and then buying new stuff is a way to piss off your wife
4) I like to use my expensive stuff for YEARS, not months. Im still using a 2 thousand dollar home stereo receiver in my movie room for about ..... 5 or 6 years now.
5) The more you learn about your expensive stuff, the better you will be able to make your expensive stuff sound.... and this is where we agree. Its all about sound. I want good, clean and LOUD, if I chose, sound. You likely arent getting all that your equipment is capable of if you just do as you suggest and hook it up and go to town.


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