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Discussion Starter #1
Hi guys,

Newbie here. Please excuse me for this simple question, but I cant seem to find an answer after searching this forum.

My question is; I'm bridging my 4-channel amp to 2-channel, connected to a 3-way passive component. Therefore the amp can set gains for left and right channel separately.

How do I go about getting the right balance between left and right speakers?
a) Do I just set the gains at equal settings on the amplifier knob? E.g. both knob at 10 o'clock.
b) Should I do it by ear and set the gains until it sounds centered in front of me?
c) Should I use a RTA app on my phone, and set the gains until left and right channel produce equal dB at the driver's seat?

I do not have a standalone DSP, however my head unit (Kenwood DMX718WBT) has time alignment and individual volume level for right and left speakers. Is there any advantage to setting equal gain on amp and adjust the left/right levels on head unit VS setting individual left/right gain on the amp?

Thank you so much in advance!
 

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Set gains properly (if you don’t have the right tools, a basic digital multimeter can help) for both channels. They should be the same.
Then Use TA and other settings on deck to adjust for listening position / imaging etc.
 

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I agree. Set gains with the head settings all flat and use a 1000 hz tone. One side at a time, obviously. Then set time alignment and highpass. The crossover of the headunit is the one to use. Set the amp crossover to full or all pass.
 

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You need to have your gains roughly set correctly first. With both side at equal gain, you should reach about 75% of your head unit's volume range for enthusiastic listening. Play some music that you like to listen to loudly, and set both gains equally so that at 75% of your head unit's volume that particular song is plenty loud, but doesn't sound distorted. It's important that you get this close before moving on the adjust the left and right independently. If you don't get this right now, you'll have to redo the next step a time or two until you dial thing in. You'll save a lot of time down the road if you get this right before moving to adjusting the left and right independantly.

Now that you've got a good idea about where on the gain knob you're working, disconnect the midbass, and midrange from the crossover (shut off the stereo first). Find a song in your collection that has a female lead singer, the higher notes the singer hits the better. Play that song with only the tweeters connected. With just the tweeters playing, adjust your head unit's left and righ balance so that the vocals sound centered between the left and right boundaries of the car interior. When I say centered I mean that that vocals will be appear to come from the center of the car's hood, not centered directly in front of your face while driving. Imagine a point where a hood ornament on a car's hood would be, that's the point your centering on, not the point directly ahead of the steering wheel.

If you find yourself with more than about a 3db difference between the left and right on your head unit to get the vocals centered, then you know that amp gains need some fine tuning. Keep in mind that our ears are closer to the left tweeter than the right. Because of this, it's reasonable for the left side to be around 2-4dB quieter than the right side, based on your head unit's settings. If you need a deviation larger than 2-4dB in order to get female vocals centered, then you need to adjust the amp's gain to bring the louder side down to within a 2-4dB range. Your amp's gain pots should be similar enough that matching them visually should get you within this range, but some gain pots are pretty sensitive, so tweak them as necessary to get the left and right amp gains close enough that you only need small adjustments on your head unit to get a centered vocal image.

After balancing the left and right sides to place high frequency vocals in the center of the stage, this step is done. Turn the head unit off, and reconnect the midrange and midbass.

With the midbass and midrange now playing with the tweeters, the vocals should sound reasonably centered, and you should need around 75% of your head unit's volume knob in order to reach enthusiastic listening levels. If both of those are true, you're done with this step.

But, if the music is loud enough at only 25-50% of the head unit's volume range then your gains are both too high, and you'll need to turn them both down equally, and redo the previous step. Make sure you get the overall gain setting as close as possible before you start balancing each side independently.



At this point we have only centered the high frequencies using left/right amplitude matching. Now it's time to focus on centering the low frequencies. That will be done using the time alignment settings on your head unit. We can go into detail on that step later, if necessary.

By getting the high frequencies centered using gains to balance amplitude, and by getting the low frequencies centered using time alingment, you'll have a very reasonable soundstage.

Running active with a real DSP will give you even more tools to fine tune the staging and imaging, but if you follow the steps above to center the highs via amplitude, and lows via TA then you'll have a pretty respectable sound stage.
 

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Discussion Starter #5
Thank you everyone for the advice!

What I understand so far is that I need to set the gains as you normally would on an amp (regardless bridged/unbridged) to get a clean signal, and since it's on the same amp the final gain setting will be similar for left and right side. Once that is done, then I will use the head unit to fine tune and get a center image.

One more question: My HU has the usual left/right balance settings, but it also has a volume level setting for left/right speakers that can be adjusted from 0db to -8db individually. Is there any benefit of using one over the other?
 

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Discussion Starter #6
But, if the music is loud enough at only 25-50% of the head unit's volume range then your gains are both too high, and you'll need to turn them both down equally, and redo the previous step. Make sure you get the overall gain setting as close as possible before you start balancing each side independently.
Maybe I'm not used to listening at loud volumes, but I find that it's loud enough for me at 50% of the HU volume.

My HU pre-outs are 4V (based on spec, not measured), and amp is bridged providing 200W to a 100w 3-way passive components. Gain is dialed all the way down. It sounds clean at the moment and I think the amp can provide more power, but I'm not sure if I should increase the gain at the risk of damaging the speakers. I've went to several shops and they all have different approach to this.
 

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Find the max clean volume of the headunit first. If it is a newer Kenwood, some don't clip the output even at max volume. If you normally don't listen that loud, fine, we all need headroom for those sources and songs recorded lower.
 

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Discussion Starter #8
Find the max clean volume of the headunit first. If it is a newer Kenwood, some don't clip the output even at max volume. If you normally don't listen that loud, fine, we all need headroom for those sources and songs recorded lower.
I have not tried exceeding 75%, as it sounds loud enough for me. But I do have some songs at a noticeably lower volume than others. Will try using these songs to set the gains so I can have some headroom for them. It's a relatively new HU model, I'll see how high can I go.

Thanks!
 

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If you find yourself only turning the volume up to 50% even during enthusiastic listening, then the gains are too high. You do want some extra at the upper end of the volume knob to account for low volume recordings, but you don't want to leave 50% of the range unused.
 

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Discussion Starter #10
If you find yourself only turning the volume up to 50% even during enthusiastic listening, then the gains are too high. You do want some extra at the upper end of the volume knob to account for low volume recordings, but you don't want to leave 50% of the range unused.
I've double checked, and it was my mistake. The gains were initially all the way down, but the last shop i went to dialed it up at a bit. I've dialed it back down, and now 75% HU volume is still very loud but bearable. Enthusiastic listening at about 65%.

Sound is very clean, doesn't seem to have any distortion. At equal gains the imaging is surprisingly coming more from the passenger side. I played a mainly female vocal track, reduced passenger side by just 1dB and got the imaging at pretty much in the center of the dash. I tried experimenting with imaging directly in front of me, but it doesn't feel right. It feels more natural to have it in the middle of the dash like you said.

Will try to do the time alignment tomorrow. My HU allows for time alignment by inputting the speaker distance. As I'm running passive, should i calculate the distance to midrange or the midbass/woofer? Midrange is on dash next to tweeters, woofer is at lower door panel.

Sorry I'm deviating from the original topic.
 

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I've double checked, and it was my mistake. The gains were initially all the way down, but the last shop i went to dialed it up at a bit. I've dialed it back down, and now 75% HU volume is still very loud but bearable. Enthusiastic listening at about 65%.

Sound is very clean, doesn't seem to have any distortion. At equal gains the imaging is surprisingly coming more from the passenger side. I played a mainly female vocal track, reduced passenger side by just 1dB and got the imaging at pretty much in the center of the dash. I tried experimenting with imaging directly in front of me, but it doesn't feel right. It feels more natural to have it in the middle of the dash like you said.

Will try to do the time alignment tomorrow. My HU allows for time alignment by inputting the speaker distance. As I'm running passive, should i calculate the distance to midrange or the midbass/woofer? Midrange is on dash next to tweeters, woofer is at lower door panel.

Sorry I'm deviating from the original topic.
Typically, you'll reduce the driver side tweeter, since it is closest to you, but with the amp gains being L/R it's not unreasonable to be off just enough to make your 1dB decrease on the passenger logical. Whatever gets you a nice center image.

Regarding time alignment, I would personally measure both the midrange, and midbass, and try both. Phase (TA) is very important to us in low frequencies, but your midbass may be playing enough low bass that localizing the sound to the center may not be as easy. I suspect that regardless of whether you set the TA using the midrange, or midbass, the results will be very similar, since you are only aligning the left and right, instead of an active setup where you'll be aligning each speaker. Measure as accurately as you can. If you have the door panels on, and the speakers behind them, make a reasonable estimate regarding how far back the speaker's voice coil is from the front of the door panel, and add that distance to your measurement. You're trying to measure from a specific point in between your ears to each voice coil, so you may need to add a bit of extra distance to your measurement if you can't measure straight to the speaker's center. Don't obsess over every fraction of an inch, moving your head a tiny bit while driving will cause a bigger difference than being of by 1/4" in your measurements, but be as accurate as you can and you'll have good results.
 

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Discussion Starter #12
Typically, you'll reduce the driver side tweeter, since it is closest to you, but with the amp gains being L/R it's not unreasonable to be off just enough to make your 1dB decrease on the passenger logical. Whatever gets you a nice center image.

Regarding time alignment, I would personally measure both the midrange, and midbass, and try both. Phase (TA) is very important to us in low frequencies, but your midbass may be playing enough low bass that localizing the sound to the center may not be as easy. I suspect that regardless of whether you set the TA using the midrange, or midbass, the results will be very similar, since you are only aligning the left and right, instead of an active setup where you'll be aligning each speaker. Measure as accurately as you can. If you have the door panels on, and the speakers behind them, make a reasonable estimate regarding how far back the speaker's voice coil is from the front of the door panel, and add that distance to your measurement. You're trying to measure from a specific point in between your ears to each voice coil, so you may need to add a bit of extra distance to your measurement if you can't measure straight to the speaker's center. Don't obsess over every fraction of an inch, moving your head a tiny bit while driving will cause a bigger difference than being of by 1/4" in your measurements, but be as accurate as you can and you'll have good results.
Alright, I'm gonna give it a try tomorrow with both the mid and woofer. Thanks again for walking me through this in detail. :)
 

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I’m going to disagree with the above, for maximum signal to noise ratio you first need to have gains as low as possible

there are two ways to set output level, gains matched and attenuate the level in the dsp, or have asymmetric gains and match them in the dsp

The first way will give worse signal to noise ratio, the latter will give way better signal to noise ratio

in other words less hiss and potential for background noise

you want the gains as low as possible on the amplifier and as much signal from a source as you can get... then and only then do you need to reduce signal level into the amplifier

for example in my car the only gain that’s anywhere other than zero is the passenger side front midbass as the output level in my dsp is +5 (this is unclipped and 6v) and it needed a little more to match levels with the drivers side midbass which has minimum gain and only 2db in levels

it’s all about gain structure through the system

b and c are kind of on the mark but not really accurate as you will match the loudest spikes in the pink noise and not the overall levels

if you eq’d both sides and did it by ear you’d be closer, but if you’d eq’d them with an rta you could then adjust the gains to match each other, only when the gains hit minimum should you then attenuate in the dsp 👍🏼
 

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I’m going to disagree with the above,
I'm not sure who you are disagreeing with, but my point about using as much of the head unit's volume knob as possible it to keep the gains further down the chain as low as possible, keeping noise low, as you pointed out.

In a system where strong listening levels are achieved low in the head unit's volume range, the gains are too high, which is likely inducing noise, and also creating a risk of someone accidentally turning the head unit volume up way past where it should be.
 
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