Tunning Upgraded Subwoofer and Mono Amp

piterek

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Just upgraded the OE subwoofer in my 2019 ST Hatch with an 8" shallow mount Pioneer. Driving it with Alpine MRV-M500, using OE subwoofer wires as speaker-level input. The amp has the following controls... Gain, LPF and Bass EQ (fc=50Hz). I have a remote bass knob in the front, which basically attenuates gain from the value set on the amp to zero.

The head unit obviously has subwoofer control, so now with all the other controls added... is there a good accepted practice to tune the upgraded setup? Where should the HU controls be... middle, 3/4... other?

Something else that came to mind... I recall @ctrmofo noting that the HU is only expecting to see 2 ohms on the subwoofer channel... but these wires are now seeing high impedance (high level input on the amp)... would this affect what the head unit outputs to this channel. I'd normally just tap full range speaker wires, but in this case they were actually disconnected from the speaker and moved to feed the amp.

The sound has improved a lot, and I will continue to experiment... but I am hunting for some of the punch that is lacking in the sound. Not looking to rock the neighbourhood with the 8" shallow mount unit... but I've heard 8" perform much better, Hope someone who's done this would chime in with their thoughts and experience. TIA.
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kperalta

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Just upgraded the OE subwoofer in my 2019 ST Hatch with an 8" shallow mount Pioneer. Driving it with Alpine MRV-M500, using OE subwoofer wires as speaker-level input. The amp has the following controls... Gain, LPF and Bass EQ (fc=50Hz). I have a remote bass knob in the front, which basically attenuates gain from the value set on the amp to zero.

The head unit obviously has subwoofer control, so now with all the other controls added... is there a good accepted practice to tune the upgraded setup? Where should the HU controls be... middle, 3/4... other?

Something else that came to mind... I recall @ctrmofo noting that the HU is only expecting to see 2 ohms on the subwoofer channel... but these wires are now seeing high impedance (high level input on the amp)... would this affect what the head unit outputs to this channel. I'd normally just tap full range speaker wires, but in this case they were actually disconnected from the speaker and moved to feed the amp.

The sound has improved a lot, and I will continue to experiment... but I am hunting for some of the punch that is lacking in the sound. Not looking to rock the neighbourhood with the 8" shallow mount unit... but I've heard 8" perform much better, Hope someone who's done this would chime in with their thoughts and experience. TIA.
You tune the amp the way all amps are tuned. Either multimeter, ear, or with a distortion detector. Set your crossover at 80, and leave your bass eq off
 
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piterek

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You tune the amp the way all amps are tuned. Either multimeter, ear, or with a distortion detector. Set your crossover at 80, and leave your bass eq off
Right... ear it is then. Is 80hz the HU LP frequency on the sub channel? Why would I not leave the HU in charge of LPF. Should the HU sub level be fixed at some value whan doing this? This is one wonky setup... just shooting some questions. Wish I knew more about the HU. Thanks!!
 

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Right... ear it is then. Is 80hz the HU LP frequency on the sub channel? Why would I not leave the HU in charge of LPF. Should the HU sub level be fixed at some value whan doing this? This is one wonky setup... just shooting some questions. Wish I knew more about the HU. Thanks!!
You turn the head unit up 'til you hear distortion, and back it off and leave it. Then you turn up the gain 'til you hear distortion. You can let the HU handle the crossover but whatever frequencies it isn't sending won't be affected by the amp anyways. I don't know the sub channel crossover. I don't usually tap the sub signal using a sub channel.
 
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Something else that came to mind... I recall @ctrmofo noting that the HU is only expecting to see 2 ohms on the subwoofer channel... but these wires are now seeing high impedance (high level input on the amp)... would this affect what the head unit outputs to this channel. I'd normally just tap full range speaker wires, but in this case they were actually disconnected from the speaker and moved to feed the amp.
The sub-woofer is 2 Ohms, but the Head Unit is not "Expecting" to see 2 ohms.
In reality, it is spec'ed to run into speakers as low as 2 ohms, but will work just as well into higher ohm speakers -- but will then deliver less power for a given volume setting.

The fact that you do not have any speaker connected should not upset the amp, (in the way that Honda is using that AMP I/C on their units) .
The DSP unit you are feeding has some much higher impedance, and the amp should be quite happy with that ... in fact it will be happy to run a lot cooler, as it is not required to deliver the power to a 2 ohm speaker any more.

In your case, you are not concerned about POWER that is feeding your new DSP + AMP, but rather the relationship between Volume setting and Voltage out, which should remain the same, despite the higher impedance (without the 2 ohm speaker) drawing far less current.
 
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piterek

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The sub-woofer is 2 Ohms, but the Head Unit is not "Expecting" to see 2 ohms.
In reality, it is spec'ed to run into speakers as low as 2 ohms, but will work just as well into higher ohm speakers -- but will then deliver less power for a given volume setting.
Thanks. Explains why I needed to have the sub level maxed out on the HU... AND have the gain on the amp at least half way to get to a good overall sound level. Not liking to turn any control to its maximum level... but it is what it is. Wonder if a parallel connected ~4 ohm wirewound power resistor would improve signal delivery (or ruin the quality)... just thinking out loud here. I get the volume level, but feel that it comes with a lot of amplification from both the HU and the amp (usually not a good thing). Cheers.
 
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piterek

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I don't know the sub channel crossover. I don't usually tap the sub signal using a sub channel.
Have seen someone claim the LP frequency to be 80Hz on another forum... Accord I think. Have never tapped a sub channel nor just used the open circuit sub wires for input on the amp. Still can't believe this was peddled as a premium system. Thanks for your feedback.
 

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Have seen someone claim the LP frequency to be 80Hz on another forum... Accord I think. Have never tapped a sub channel nor just used the open circuit sub wires for input on the amp. Still can't believe this was peddled as a premium system. Thanks for your feedback.
All "premium" systems are like that. Most people won't buy a car if it has a giant subwoofer in it taking up space which is why most car makes only use 8s
 

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Have seen someone claim the LP frequency to be 80Hz on another forum... Accord I think. Have never tapped a sub channel nor just used the open circuit sub wires for input on the amp. Still can't believe this was peddled as a premium system. Thanks for your feedback.
Also regardless of that, in normal set ups with an after market radio I never use crossovers from the radio. The crossovers on amps are always the better option.
 

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This has probably already been said...

But my experience with speaker level amp outputs is that they tend to have most of their 'usable gain' in the first 25-30% of the dial. It tends to drop off beyond that, in my experience. Certainly you can go higher. But that's where the noise and harmonic distortion begin.

So your sweet spot is at the point of diminishing returns on the dial; usually 3 or maybe 4 on a 1-10 scale.

And I'd let the Honda HU just send the fullest signal that it can send. You can lop it off at your amp.

Good luck.
 

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I have not installed any additional amps in my car, but from what I have read, and what makes sense to me is to adjust by.

(1) Set Honda Unit to Max Volume output.
(2) Adjust addon amp to maximum you can without clipping.
(3) Turn down addon amp to about 25% of the above max, (keeping Honda volume at 100%, and listen/ measure for distortion.

(4) If not distorted, then you are not Overloading the INPUT addon amp when Honda is at max Volume, and you can then go and set the Addon amp back to the setting in step 2, and you are finished,

(5) If it is distorted, the turn down the Honda Volume till it is just not distorted.
You are then putting the Max input to the external amp before the input of the amp gets overloaded.
Then based on that lower Honda Volume level, you will need to attenuate the input to the external amp , so it does NOT distort at 100% Honda Volume, (using some sort of resistive divider network),

(6) Then you are back to a state where you can follow step 4.

Chances are, the amp (or DSP unit), if it is designed to connect to a typical car radio speaker, will NOT have it's Input overloaded by the Honda Unit being at 100% Volume, so step 5 should not be necessary.

The tricky part is determining when there is distortion, and deciding just how much distortion you can accept, as you turn things up to get more and more volume - and just how much of that distortion is due to the AMP clipping, or the Speakers just being overloaded, or not physically mounted correctly.
 

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I have not installed any additional amps in my car, but from what I have read, and what makes sense to me is to adjust by.

(1) Set Honda Unit to Max Volume output.
(2) Adjust addon amp to maximum you can without clipping.
(3) Turn down addon amp to about 25% of the above max, (keeping Honda volume at 100%, and listen/ measure for distortion.

(4) If not distorted, then you are not Overloading the INPUT addon amp when Honda is at max Volume, and you can then go and set the Addon amp back to the setting in step 2, and you are finished,

(5) If it is distorted, the turn down the Honda Volume till it is just not distorted.
You are then putting the Max input to the external amp before the input of the amp gets overloaded.
Then based on that lower Honda Volume level, you will need to attenuate the input to the external amp , so it does NOT distort at 100% Honda Volume, (using some sort of resistive divider network),

(6) Then you are back to a state where you can follow step 4.

Chances are, the amp (or DSP unit), if it is designed to connect to a typical car radio speaker, will NOT have it's Input overloaded by the Honda Unit being at 100% Volume, so step 5 should not be necessary.

The tricky part is determining when there is distortion, and deciding just how much distortion you can accept, as you turn things up to get more and more volume - and just how much of that distortion is due to the AMP clipping, or the Speakers just being overloaded, or not physically mounted correctly.
Our headunits at least in the amplified cars are not clean up to max.
 

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Our headunits at least in the amplified cars are not clean up to max.
I believe they actually are.quite clean ..
The IC used in the AMP has very low distortion, even at Max output into 2 ohms. There is a slight increase in distortion as you reach max out into 2 ohms, but nothing that even the best Audiophile could detect. 99% of the AUDIO heard distortion at high levels are due to the speakers or their installation.

I have personally measure max volume (pre clip) under Maximum Load (2 ohms) with scope and signal generator, and the output is very clean.

see https://www.civicx.com/threads/2018-premium-audio-system.33835/
 

kperalta

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I believe they actually are.quite clean ..
The IC used in the AMP has very low distortion, even at Max output into 2 ohms. There is a slight increase in distortion as you reach max out into 2 ohms, but nothing that even the best Audiophile could detect. 99% of the AUDIO heard distortion at high levels are due to the speakers or their installation.

I have personally measure max volume (pre clip) under Maximum Load (2 ohms) with scope and signal generator, and the output is very clean.

see https://www.civicx.com/threads/2018-premium-audio-system.33835/
Nice. Using pink noise I presume? My experience with the headunits with touch or non touch is a 40hz test tone and I usually see/hear clipping around 36-37.
 
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piterek

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Also regardless of that, in normal set ups with an after market radio I never use crossovers from the radio. The crossovers on amps are always the better option.
True... In this case I assume that the HU sub LPF is fixed at factory (another dumb idea, unless there is a way to change that value). If the HU LPF is set at say 80Hz, then setting the new amp at say 100Hz won't do anything useful, except maybe inject noise. Alternatively, setting the amp at 60Hz will leave a 60-80Hz gap for other channels to pickup if able.

Needless to say... miss my Alpine HU. Only needed 7 channels to sound great.
 
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