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Old 04-11-2007, 02:21 PM   #1
Flytog
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JL 12W6v2-D4 Sub with a Kicker ZX750.1 amp?

I just bought a JL 12W6v2-D4 Sub and I already have a Kicker ZX750.1 from a previous install. The kicker is rated for 750 watts RMS @ 2ohms (birth sheet says its actually 930 watts RMS).

The sub is a dual 4 ohm rated at 400 watts RMS. It can be wired to be either 2 ohms or 8 ohms.

I want to know if I should go ahead and use my kicker and just turn down the gain or get new amp to go with the new sub.

I figure the RMS figures on the amp were calculated with 14.4 volts, so a real world 13.x might lower the figures a little anyway. Would I be losing anything by turning things way down on the amp?

I've heard that it is better to have a more powerfull amp than is reqired (with propper gain settings) for subs because the SQ is better at low volumes and it has plenty of spare power to stop the movement of the speaker allowing it to have tighter and crisper sound.

What should I do? I really don't want to damge my new sub!
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Old 04-11-2007, 02:31 PM   #2
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Youll be fine with that amp. Use the gain setting tutorial on JL's website.

To figure what to set your amp to -

V = sq.rt(400) x 2ohm

So you should set your amp gains to 40volts.

To summarize:
Download a -3db 50hz sound file.
Unhook your sub leads
Turn volume up on headunit to highest attainable level without distortion. Generally 75 percent of max level. (i.e 46/62)
Play sound file on repeat
Check voltage at amp speaker terminal and set gains according to voltage determined.
Hook back up the speaker wire.

It gets more indepth on the JL site with pictures and stuff. Just wanted to give you an idea.
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Old 04-11-2007, 02:32 PM   #3
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Also, if you decide to use bass boost, EQ's and other sound thingies, make sure you set that before you set the amp gains. if you set the gains and alter other settings, you will chance blowing your sub.
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Old 04-12-2007, 08:47 AM   #4
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As others said, amp is fine for your sub as long as it is properly adjusted and you don't get any clipping (distortion) on the sub. I would strongly suggest not using any bass boost on the head unit or amplifier.
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Old 04-12-2007, 11:15 AM   #5
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You'll be fine but just keep in mind repair costs are high with a JL.

Suggest that you go with a sealed box so that the sub has a better power handling capability.
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Old 04-12-2007, 01:02 PM   #6
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Thanks for the replies!

Am I going to be losing anything by turning the amp down (hard on the amp, muddy sound, etc..)? Would I be gaining anything versus an equal quality amp that is 400 watts RMS @ 2 ohms (would the one that is turned down run cooler than the other at equal volumes and sound the same)?

Sorry for all the questions, I'm just trying to make sure I'm going to get everything I can out of the sub. If you think I should get a different amp, give me some suggestions.
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Old 04-12-2007, 01:12 PM   #7
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I wouldn't just turn it down. I would adjust it for optimum gain (max power without distortion), then turn it down if you have to. As far as getting damaged, it's just like an engine. If you drive it hard and stress it, it will last less than if you drive like a normal person, so less strain on the amp = more probability of a longer useful life.

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Originally Posted by Flytog View Post
Thanks for the replies!

Am I going to be losing anything by turning the amp down (hard on the amp, muddy sound, etc..)? Would I be gaining anything versus an equal quality amp that is 400 watts RMS @ 2 ohms (would the one that is turned down run cooler than the other at equal volumes and sound the same)?

Sorry for all the questions, I'm just trying to make sure I'm going to get everything I can out of the sub. If you think I should get a different amp, give me some suggestions.
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Old 05-09-2007, 12:34 PM   #8
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I actually didnt get around to installing everything till last weekend. I set the gain on the amp to around 30 volts (using this calculator: http://www.subwoofertools.com/forum/setgain.asp). That setting had the gain just a hair from being all the way down and the sub was pretty quiet.

I have everything set to flat with no bass boost or anything like that. The volume is all the way up (my HU does not clip at all, according to my oscillioscope). My HU is an Alpine 9885 with 4v pre-outs.

Here is the weird part, if I turn the gain all the way up on my sub amp (with no sub connected of course) I can get it to put out around 80 volts. The most it should be capable of is 45 or so (that would be 950@2ohms). Is that normal? Perhaps something is wrong with my voltmeter and its just reading everything to be higher than what it actually is? Any sugestions?
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Old 05-09-2007, 12:44 PM   #9
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If you have a scope, why bother with the voltage thing? Just set it using the scope only, can not get more precise or quicker results than using a scope.

Also, having no load on the amp might affect things a bit.

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I actually didnt get around to installing everything till last weekend. I set the gain on the amp to around 30 volts (using this calculator: http://www.subwoofertools.com/forum/setgain.asp). That setting had the gain just a hair from being all the way down and the sub was pretty quiet.

I have everything set to flat with no bass boost or anything like that. The volume is all the way up (my HU does not clip at all, according to my oscillioscope). My HU is an Alpine 9885 with 4v pre-outs.

Here is the weird part, if I turn the gain all the way up on my sub amp (with no sub connected of course) I can get it to put out around 80 volts. The most it should be capable of is 45 or so (that would be 950@2ohms). Is that normal? Perhaps something is wrong with my voltmeter and its just reading everything to be higher than what it actually is? Any sugestions?
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Old 05-09-2007, 02:35 PM   #10
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I'm glad you brought that up, no one has actually been able to tell me how I go about doing it with a scope.

I only have the scope because I was using it as a monitor for a spectrum analyzer (ham radio). I got it with that purpose in mind and so I don't have any probes for it and I'm not entirely sure if its calibrated correctly. Nor do I know how to even properly use one!

All I know is I can set it up to view the sine wave and see if it clips or distorts.

So if I hook it up to the output of the amp am I looking for the sine wave to distort in the same way as it would on a head unit, or am I actually trying to get a voltage reading with it?

Since I have no probes, it would be going strait from the amp to the scope with nothing in between. Should I even try doing that?

I'm not an electrical engineer - I know just enough to get myself into trouble!
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Old 05-09-2007, 03:22 PM   #11
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You need a probe. Don't want to burn up the scope. Pick up a cheap or used probe somewhere. Make sure you calibrate the probe once you get it (most scopes have a built-in calibration system)

What I do is first, stick a CD with a test tone in the head unit. Test tone has to be obviously at an appropriate frequency. If you are testing bass, maybe 40 - 50Hz, depending on crossover frequency. For speakers I use 1KHz.

First put the probe on the RCAs coming from the head unit (I cut up a cheap y-adaptor so that the signal passes trhough into the amp and I can tap the probe on the wires). Set everything in the radio to flat (bass, treble, mmx, bbe, loudness, balance, eq, sound processing, etc). Then turn the head unit volume up as far as you can go right before distortion. If you can go all the way up, then congratulations to Alpine, otherwise, just take note of the volume, as this is the max you can get without distortion and should use it for reference, tuning and tweaking.

Then, move on to the amp outputs, set all the bass boost and equalization at the amp to zero, check speaker outputs with the gain at the minimum. Turn gain up until you get distortion. If your scope can handle the high voltage ~100 volts, then just hook it up to the sub output with the probe. If not, you have to use a couple resistors to do a voltage divider and ensure you don't zap the scope. Let me know if you need help with that. I would suggest setting the gain with a live load rather than an open. If you don't want to feed a sine wave signal to your speakers at high-levels, then maybe wire up the coils for 8-ohms. You won't get the full output, but you are only concerned about the signal "shape", not magnitude.

As a "reality" check, your head unit puts out 4 volts, look at the amp gain and imagine the 4 volt mark on it (based on minimum and maximum rated level). Although ratings and settings are not accurate, you would get a feel to whether you are in the correct ballpark.
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Old 05-09-2007, 04:15 PM   #12
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Also, with Alpine decks dont you have to have bass to +15? I would do that and reset the gains.

IIRC, alot of people have this issue on the alpine decks and resolve it this way.
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Old 05-09-2007, 04:32 PM   #13
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Good point. You could scope for max output with no distortion and set it at the max, or pick a mid level (i.e. 2/3's of the way up and use that as a reference).

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Also, with Alpine decks dont you have to have bass to +15? I would do that and reset the gains.

IIRC, alot of people have this issue on the alpine decks and resolve it this way.
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Old 04-14-2008, 10:26 AM   #14
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I also bought the same amp, and am going to use it with sony explode for now untill I buy a really good sub (or subs).
Let me know how is that amp treating you. Also, did you get the output for the amp from the stock amp, or directly from teh head unit?
This amp that you bought is rated at 375 RMS Watt at 4 Ohm.. y dont you wire it at taht and u wont have to worry about your woofers and gain that much??

Thanks.
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Old 12-19-2012, 08:22 PM   #15
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i like the HK i dont think they are unclear so i guess if i notice a difference itll be when i add a third sub, i plan on going with the 8 incher. 200 RMS
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