[euro3er]

When it comes to tuning a car subwoofer with a DMM (which I have done before) I have been reading everywhere that you're supposed to set your head unit volume at 75% of max volume.

What I was wondering about is that why can't I set my volume at 20 or 22 if that's my max listening level and then set the amp gain according to that max level as I'll never go higher then that?

Here is my setup:

Alpine CDE-HD149BT

Polk Audio SR5250

Polk Audio DB690

Alpine PDX-F4

Alpine SWR-12D2 x2

Alpine MRX-110

The CDE-HD149BT has a max volume of 35, 75% of that would be 26.25 or 26.

The mono-block and subwoofers are 1000 watts x 2 ohms = 2000 watts/square root = 44.7 volts (which is what my gain should be set to).

Thank you in advance everyone!

 

[JVD240]

It really depends.

You don't NEED to set it at 75%. That's a general rule of thumb. I know my 80PRS can be run full jam without distortion.

What you need to be aware of is leaving power on the table and/or raising the noise floor.

 

[euro3er]

It really depends.

You don't NEED to set it at 75%. That's a general rule of thumb. I know my 80PRS can be run full jam without distortion.

What you need to be aware of is leaving power on the table and/or raising the noise floor.

I see what you're saying. When I thought about it, I never listen to music at volume 26. The highest I've ever listened to it was 20 with the windows down and it was clean. However, if I tune to volume 22 accordingly, giving me some room for volume, wouldn't that be the better thing to do?

Could you possibly elaborate on the 75% volume level when using a DMM versus sound output and clarity?

 

[JVD240]

I see what you're saying. When I thought about it, I never listen to music at volume 26. The highest I've ever listened to it was 20 with the windows down and it was clean. However, if I tune to volume 22 accordingly, giving me some room for volume, wouldn't that be the better thing to do?

Could you possibly elaborate on the 75% volume level when using a DMM versus sound output and clarity?

You could just give it a shot and see how it sounds. I really doubt you will have any problem with it in this config.

Fairly certain 75% is just a general guideline as to when some decks will start clipping. Usually you want the max undistorted signal coming from the HU and match the amp sensitivity accordingly. This will give you the most available undistorted power and the lowest noise floor. Depending on the output voltage of your HU at volume 20 and the input sensitivity of your amps you might be able to get full available power out of the amps. But maybe not.

Think about if you were to set your HU to volume 6 lets say. Then you have to crank your amp sensitivity wide open to get any sort of level. What you did was bring up the overall level... which includes the noise floor.

I cannot comment on how dynamics, clarity, etc. will be effected in your situation. Only one way to find out.

Also, keep in mind that your volume control is not linear... meaning the you're not necessarily getting 75% of max voltage at volume 26.

Best practice is always to get maximum unclipped signal from the HU and adjust the amp to match that. Did I say that already?:laugh:

What's your reason for not setting it as such? Too many turns of the knob? Haha.

 

[Weigel21]

75% recommendation is a flawed method. Some HU's produce distortion before that level, while others can play at full tilt distortion free, as JVD240 said.

Your Alpine is likely to be able to play full tilt as well with the preamps remaining distortion free.

I ASSuME you set the gains on the PDX with the volume at level 25/26, though I'd recommend going back and resetting it with the volume higher. Why? You'll get more range in your volume control for one. With the volume set lower, you have less control over the ouput level,as each click raises output more than it would if the volume dial had been set higher.

Once you have the gain set again for the PDX, you can find the loudest level you listen to the stereo at and use such for the level to set the sub amp gain. I've done this for quite some time. I've tried setting the gain for both full-range and sub amps with the volume at the same level, but it always results in not enough bass for some music while the full-range are just SCREAMING away. So, I begain using my loudest listening volume to set sub amp gain.

Another thing to remember is that the DMM method tends to be a conservative method for setting gains and one is "recommended" to not use higher attenuated level test tones, as you can't tell if clipping is being induced with a DMM.

Setting the gain by ear with the aid of test tones can be as accurate as setting with a Scope, at least it's been proven to be possible, however it relies on one's ability to hear and distinguish 1%THD. If one can not detect such, then this method can not be used effectively. Many can hear 1%THD, but not everyone, so it's not recommended as a gain setting method terribly often.

 

[1fastkingcab]

As a rule of thumb I tell people to shoot for 19-21 on the alpine stuff, now that's just a good number that I know will work without being withing 100miles of the unit, if you are actually going to get technical you'll find that 23 is about as high as you can go depending on your soruce (MP3 /WMA / CD /CD-R / XM )

I set them up with a CD @ 21, that leaves some room to turn it up when your on a less than perfect source like SiruisXm or MP3's

 

[euro3er]

Thank you for all the responses. I'm going to play around with different volume values and tune with the DMM and see how things turn out. I was going off of the general 3/4 rule of thumb as stated above, so lets see how things turn out now.

 

[Weigel21]

1fastkingcab, are you talking about internal power clipping or preamps? OP is not using the internal amplifier and in all truth, 23 should NOT be the maximum clean volume for the HU's preamps. While I can't exactly comment on his model, I know that the models I've owned have all been capable of playing higher than 23 without distortion. I'd ran the CDA-9815, CDA-9833, and CDA-117. His looks to be the second model down from the top, surely the preamps can remain clean beyond level 23, internal power, maybe not.

"IF" you, euro3er, can hear and identify 1%THD, then you should be able to find the maximum clean volume level of the HU.

If you go to this page, there's a test about 1/3 of the way down the page in which a 400Hz tone is played clean, then with 0.5%THD, then 1%THD, then 5%THD and finally at 10%THD.

Again, if you can detect when the tone plays at 1%THD, then you could easily download 0dB test tones and play them in the car to find the HU's maximum clean volume level. You'd want to dial the gains on the PDX down to minimum for this, then you can reset them.

 

[euro3er]

So I went ahead and attempted to tune the system with a DMM again and either I'm not doing something correctly or I got lucky when I did it previously.

I inserted the 50 hertz 0db test tone cd that I burned into the disc player, hooked up the DMM to the sub amp, disconnected the power to the 4 channel amp and set the volume on the head unit to 20, 22 and 26 for this test.

The DMM was set on 200 VAC. The reading that I was getting on the DMM was a little under or way above the reading I should be getting when the gain on the sub amp was set the minimum. I had the bass setting at +15 on the alpine head unit, as this is for the prevolts.

The bass boost was off, subsonic filter set to 10 hertz, LPF at 80 (I even tried it all the way down and all the way up) and the gain set all the way down at first.

Why would my reading be super high at such a low gain setting? With the volume at 22 or above I was read twice what I should be getting which was 44.7 on the DMM.

Any ideas there? Could it be my DMM? Am I not doing something right?

This is the DMM I have: http://www.harborfreight.com/7-function-multimeter-98025.html

 

[Alrojoca]

So I went ahead and attempted to tune the system with a DMM again and either I'm not doing something correctly or I got lucky when I did it previously.

I inserted the 50 hertz 0db test tone cd that I burned into the disc player, hooked up the DMM to the sub amp, disconnected the power to the 4 channel amp and set the volume on the head unit to 20, 22 and 26 for this test.

The DMM was set on 200 VAC. The reading that I was getting on the DMM was a little under or way above the reading I should be getting when the gain on the sub amp was set the minimum. I had the bass setting at +15 on the alpine head unit, as this is for the prevolts.

The bass boost was off, subsonic filter set to 10 hertz, LPF at 80 (I even tried it all the way down and all the way up) and the gain set all the way down at first.

Why would my reading be super high at such a low gain setting? With the volume at 22 or above I was read twice what I should be getting which was 44.7 on the DMM.

Any ideas there? Could it be my DMM? Am I not doing something right?

This is the DMM I have: 7 Function Multimeter

That's because the sub volume was at 15, it should be around 5-7 although some say just enough to get the dial about a 1/4 to 1/3 turn on the amp.

You DDM is one of those you get for free when you buy tools there. It works but it may be a bit off, not saying you need to replace it. Just that if you want more accurate measuring, you should get a better one.

 

[Bayboy]

What I was wondering about is that why can't I set my volume at 20 or 22 if that's my max listening level and then set the amp gain according to that max level as I'll never go higher then that?

A few reasons why that conservative setting is suggested, but the way around that is actually detecting the clipping point and not assume where it happens. The use of an oscope will negate the generalizations about all decks and will help in setting amps too! For those that aren't concerned, the general way is fine. For others who want to maximize gain settings, it's a good idea to snatch up an inexpensive but viable oscope.

 

[Old Skewl]

You need a DMM that measures True RMS voltage. I recently discovered this as well. Went back to tuning by ear. I am much happier now

 

[euro3er]

That's because the sub volume was at 15, it should be around 5-7 although some say just enough to get the dial about a 1/4 to 1/3 turn on the amp.

You DDM is one of those you get for free when you buy tools there. It works but it may be a bit off, not saying you need to replace it. Just that if you want more accurate measuring, you should get a better one.

I thought that on Alpine decks the sub volume is the pre volt signal coming from the head unit and +15 is recommended when tuning with a DMM?

If I tune at lets say +12 and the volume set at 22 or even 25, if I turn up the bass volume to +15 will I change that gain setting on the amp as I'm increasing the pre volts?

I'm a little confused now.

 

[euro3er]

You need a DMM that measures True RMS voltage. I recently discovered this as well. Went back to tuning by ear. I am much happier now

Yeah, after I was getting this high reading I went ahead and just went to tuning it by ear with a 50 hertz test tone.

 

[Alrojoca]

I thought that on Alpine decks the sub volume is the pre volt signal coming from the head unit and +15 is recommended when tuning with a DMM?

If I tune at lets say +12 and the volume set at 22 or even 25, if I turn up the bass volume to +15 will I change that gain setting on the amp as I'm increasing the pre volts?

I'm a little confused now.

What I understand is that if you set the gains at the subs max vol level, you will have trouble hearing the sub, below the 15 sub's level, just like if the other channels were set at vol 35, you would limit the power to max volume and not have any for low vol tracks.


If the amp puts 3 times the sub's rated power, then , a higher subs volume will be safer, if not maybe around 60% of 15 (8-9) close to % used for other channels.

I did mine at 7-8, and yes when I turn the sub's vol to 0 I still hear it a bit. Hardly ever set it above 11, unless I listen to main HU dial volume below 15, something I could not do or I would never hear the sub at main volume 10 out of 35 if the gains were set with max sub vol level

Not sure were the rule to set a sub 15 max vol for Alpines came from, maybe others can share their experience, I also have the sub output DSp level reduced
a bit. With these Alpine's crossover section you can also reduce that output, if you feel you need to.

 

[ErinH]

in general you should max out your headunit volume (every alpine I've had to date does not clip at full tilt), or set your headunit volume to at least 90%. this maximizes the snr at the headunit. everything down the chain should be set the same way (maximum, unclipped output using a 0dB tone). When you get the amps is where you want to make your 'headroom'. I use a -10dB tone and set the gains to clipping. Some use a -5dB tone (I prefer the former as it provides more wiggle room once you start using the DSP to cut channels and EQ bands).

 

[euro3er]

I went back and messed around with the DMM again.

I had the subwoofer level anywhere from +5 to +10 and went back and double checked at +15, then went back to the amp with the DMM and set the gain accordingly.

I had the head unit volume at a max of 22-30 with the subwoofer level in the ranges that I stated above. As I increased the volume depending on which subwoofer level I was at, the DMM was below or above the target of 44.6V.

The lower I set the subwoofer level matching the DMM reading at the amp, the less bass I had at lower volumes and the reading would sometimes be too high as I increased the volume if the subwoofer level was higher.

I believe I'm simply confused to the point that what I thought I knew on how to properly tune with a DMM, regarding matching voltages based on the setup I have and listening by ear to listen for any distortion, has gotten to the point that I'm lost.

Every google search I've done, including reading over this webpage here Gain Settings states that my subwoofer level should be at +15. I read over a thread that talked about specifically setting the amplifier gain with a subwoofer level at +15 because on Alpine decks, the subwoofer level is for attenuation or pre-volt voltages going from the head unit to the amplifier.

However, when I follow these instructions with the head unit volume set at 3/4 volume, my DMM reading is way above 44.6V.

With a max volume of 20-22, subwoofer level of +15 and my amp gain set below the minimum, I was around 44.7V, give or take on the numbers regarding volume. If I go with the 3/4 rule, which would be volume 26 at the same settings, then my DMM reading would be too high.

Do you see how I'm confused?

What could be the problem? Could it be the DMM? Could it be my stereo equipment? Could it be my test tone or could it be me, not doing something correctly?

 

[JVD240]

What are you trying to accomplish by setting your gain with the DMM? Also, you're not measuring RMS voltage... which is what you want to measure.

Are your subs dual 2ohm VCs? That's what you have listed in your gear list but you list the final impedance as 2ohm.

Have you tried setting gains by ear? Ie. Listening for distortion.

 

[Alrojoca]

Good point, yes make sure the math is done with the correct impedance otherwise you will be way off.

What is your target? Ideal Sub voltage gain at sub vol of 15 max?

That means less main vol, but as you increase it passed the lowered main vol setting when playing music the voltage will be higher, and lowering the sub level
may not help either or you will not hear much bass as I mentioned earlier

You want music playing at max vol and not clipping? Then you set your main volume near the max level of 35 for gain setting, as long as the amps dial is at less than half point, the other volumes are not meaningful, it may be common to
have no room to go lower on the gain dial with some amps, I'm still clueless about why the 15 level max should be used for sub gains, since that forces to have the sub level at max level all the time to get decent bass.

You are finding out what I mentioned earlier, don't stress out about it and use your ears.

ADDED EDITED

Also, don't forget, in the audio menu, when you go to crossovers and go to the sub section, you have a normal level of 0 max where it should be when setting the gains, you can always go to that section and lower that level after you set the gains, to balance the output with the other 4 channels

 

[euro3er]

What I've been trying to do is match the amplifier gain signal to the head unit with a DMM to get the power out of my system before clipping/distortion.

I'm running a dual subwoofer setup. The subwoofers are 2 ohm dual voice coil, wired in series at the voice coils and parallel at the speakers to present a 2 ohm load.

My amplifier is rated at 1100W at 2 ohms. If I use the formula for measuring with a DMM, I get the following:

1100W x 2 ohms = 2200W / square root = 46.9

Unless there is a different formula I need to be using for a dual setup, but I thought that it's your wattage on your amp times your final ohm load and then the square root of that?

Originally, I was going with 1000W being the output of my amplifier, but it's 1100W.

The rest is what we've been talking about and if I follow that in terms of setting the head unit volume at 26 (3/4 volume), subwoofer level at head unit at +15 and set the gain with the DMM, my reading is off the charts.

When you're saying I wanted to measure true RMS wattage, does that mean I would need an oscope for that? I know using an oscope is the best way to do it.

Also, when I've done it by ear I've had it to the point where there's no distortion or at least I think so, but I wanted to be sure using a DMM. But when I do that, I see that my tune by ear has the DMM reading off the charts.