StatuSCheckA

iTrader: (1)

I was wondering if you can help. I am using ohms law and the equation P=sqrt (watts X resistance) I have a 1100w amp 250w rms @ 4 ohms. That equals 31.6 volts. I can not get my headunit to crank out 31.6 Volts even with the gain up and LPF adjusted. I use a mono amp that is connected to one sub.
Any tips on how to tune it? Stock HU.

biglilsteve

iTrader: (2)

I am running a JL 500/1v2 @ 2 ohms to my 12W6v2 sub. This calculated to a target identical to yours: 31.6v. The head unit has no problem pushing this out.

What test tone are you using? Do you have your multimeter set to AC voltage (NOT DC)?

Check out my post here from a couple years ago. Should have everything you need to get your setup correct.

https://www.scionlife.com/forums/sho...5&postcount=48

StatuSCheckA

iTrader: (1)

Well I tried all that and still no go. Here's the scoop:
I disconnected the sub and hooked up the multimeter directly to the amp. Made sure base boost was off along with everything else. I turned up the gain all the way and still barely get 30V. Even with the HU Sub-W setting at max.

What I ended up being content with is using using the sqr root of 250X2
That gives me 22.3. And I have my Low Pass about half. And gain only about half. It sounds really good but I just don't know if I'm getting all the juice possible.

DaWiz711

There are a couple of factors at work here, I don't feel qualified to comment but posting your question to the guys over at the diyma forums might get you the answer you seek.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

oujerzy

Can you give us the details of your system? Model of your amplifier and subwoofer. Make sure you are calculating the desired output voltage based on the impedence(resistance) of the particular sub you are using. I only ask because you mentioned 250w RMS@4ohms but stated your amp produces 1100w. Assuming you are not mixing RMS with peak wattages your amp would need to take on a 1 ohm load or less to get near 1100w RMS. If you have an amp that is stable at that level I would be confused why you shelled out the extra money for a bad ___ amp if you're only going to power a single 4 ohm sub.

As another member suggested, make sure you are using a constant test tone...50hz or something like that. Here is a link to download if you don't already have one. http://www.ronelmm.com/tones/ If the track is short just set it on loop. Ideally you don't want your speakers hooked up during this test as it may be a bit much for them. If you have a TC you can just temporarily disconnect the amp under the driver seat and that will at least stop your head unit from magnifying the sound.

Reading this may help a bit as well. the12volt.com is a great resource for any and all car stereo questions. http://www.the12volt.com/installbay/....asp?TID=84618

StatuSCheckA

iTrader: (1)

Thank you. I will read some of those links. I just wanted a budget system that sounded good, not looking to shake the pavement. I have not heard many complaints about the following items.
Maybe if you can look at the products' Peak and RMS numbers you may be able to help me out. I appreciate the feedback.

Max Power @ 2 Ohms: 1100 Watts
RMS Power @ 4 Ohms: 250 Watts
Powering..
800 watts peak power handling (200 watts nominal); 4 ohm impedance

oujerzy

Ok, that info helps to clarify. First off, always ignore any "max" or "peak" power rating numbers. Normally any manufacturer that advertises with peak/max numbers does not make very good equipment but you already own that set up so it is what it is. Just use RMS to do the math and set your gain. Your amp is capable of 250W RMS@4 ohms and that is the current your particular sub is drawing. Since your sub can only handle 200W RMS, the amp should have enough power to push it. The math would be as follows. voltage desired = square root of (watts desired-200 X impedence of sub-4), which calculates to 28.28. This is the number you should be tuning for using your gain level adjustment while your voltmeter (set on AC volts) is connected to the speaker terminals on the amp. Again, it is best to drive a constant test tone through your system when setting your gain but it will put a heavy load on your speakers if you do not disconnect them, or at least the factory external amp like I mentioned in an earlier post. Let me know if you have already done this process step for step and I will try to help more if I can. I am not a stereo technician but I do have years of experience setting up my own systems and have learned a good bit, sometimes the hard way.

StatuSCheckA

iTrader: (1)

I can only reach 28.3 if the gain is all the way up which is not natural. I did everything you said with the voltmeter and 50hz sound.
I just set it back to 22volts and it sounds pretty good. For such a small package I am pleased with it, I just wanted to bang it right. I'll probably leave it as is, it sounds good and nothing is being overworked.

oujerzy

The gain is simply a sensitivity level adjustment. You can turn the gain all the way up if that is what is needed to reach the voltage to properly match the head unit's output to get the target power. An amplified signal doesn't damage speakers, a dirty signal damages speakers. I can't speak to the quality of your amp but the standard is <1% THD (total harmonic distortion). Regardless, if you are happy with the sound produced when pushing slightly less wattage to your sub then no problem with leaving the levels as such. At the end of the day, what sounds good to you is the ultimate test of your own stereo.

oujerzy

BTW one last thing I should have mentioned earlier. You are aware that you can adjust the signal output level to your sub amp from your stock head unit? I don't remember what it is set at by default but it does range from -24 to +6 I believe. If it is set anywhere below 0 this could definitely be the reason you are struggling to reach the desired voltage when setting your amp.