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craig3972

amp power for 2 JL13w6 subs

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craig3972

I have two JL13W6D4 subs running in series , 4ohms total, driven by one JLHD1200/1 amp.I have the gain up to about 5/8 of full range. The subs sound good but I think they could deliver more. When i turn the gain up beyond 5/8, I get a red led indicator light come on the amp and the power shuts off to the subs.The little HD1200/1 gets really hot but doesnt thermally shut down. I was just wondering if this is enough power for these subs? It is what is the maximum rms recommended by JL. I am using the infrasonic and the 24db octave filter. am I doing something wrong?

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Bobby Light

So you've got the subs wired Series/Parallel? Amp shouldn't shut down like that. That is minimum power for the setup.

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craig3972

thats what i thought. I thought the gain on that amp would be wide open. I ran the speaker wires for that set-up about 3 yrs ago and now i suspect that I do not have them connected in series correctly. The subs are dual VC and come prewired in a 2ohm jumper configuration. That amp likes to run between 1.5 and 4ohm to operate most effectively.

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jk13

Did something change recently? Is this a new problem, or was it like this for the last three years since wiring the subs?

First thing I recommend is to take a multi-meter and check resistance at the speaker wire--it will usually be slightly lower than actual working impedance (approx 3ohms for a 4ohm working load) and go from there. Otherwise pull the woofers and verify proper wiring.

Two dual 4 ohm subs will net either a 1ohm load (too low) or a 4 ohm load (should work great).

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Bobby Light

thats what i thought. I thought the gain on that amp would be wide open. I ran the speaker wires for that set-up about 3 yrs ago and now i suspect that I do not have them connected in series correctly. The subs are dual VC and come prewired in a 2ohm jumper configuration. That amp likes to run between 1.5 and 4ohm to operate most effectively.

I'd check your wiring to ensure you don't have the 2 subs wired in parallel at 2 ohms each, that would probably cause your amp to shut down at higher levels.

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MLA

The gain dial is not a volume knob to use to get more output. I would not want to see the gain higher then half way IMO. If the output is not to your expectations, I would investigate the rest of the amps settings, the enclosure design and its location.

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craig3972

These are my boat shaker subs that reside in the lockers. I know what everybody says about putting subs in lockers, but when I took out the old 12's i got complaints from the dancings girls that it wasnt as good as before. After i put them back in I blew one of the old kicker comp VX12's and so i replaced the pair with the 13W6's and the HD1200/1. I just used the old speaker wires and didnt check the impeadance, and i assumed that the wires were configured in series. So the total speaker coil impeadance can be measured with a multi-meter?

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Earmark Marine

Whether both voice coils are seriesed and the woofers are paralleled OR both voice coils are paralleled and the woofers are seriesed the outcome will be an identical final 4-ohm load. A strictly regulated amplifier will behave exactly the same with a broad range of loads so 4-ohm is as good as any other load in this case. Just make sure that everything is still connected properly and that everything is wired consistently according to the intended scheme. Also, do a DCR check on all four voice coils individually just to verify everything is in good condition. They should all read the same within a reasonable fraction. A DVC woofer will perform the same (other than the obvious difference in load) whether in series or in parallel. However, if only one coil within a woofer is operational and the other is unused in a paralleled application, then this creates real problems.

Sometimes the thermal ratings can be a bit conservative. And, regardless of the particular brand in question, 600 watts per each 13.5-inch driver with a larger diameter voice coil can be a bit on the light side, especially in an open air environment. So I wouldn't be afraid to up the power. Again, that is a lot of surface area, mass and voice coil times two woofers.

David

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Earmark Marine

Also worth mentioning now that I have read the application is that if these woofers are in a storage locker then you can easily lose 5 to 6 dB of output because they are not direct radiating. That would mean that an amplifier has to work four times as hard to deliver the same acoustic output. Bass EQ in this situation would be especially taxing. You might consider raising the lowpass filter a little higher. This is one way to increase the perceived output. The higher the frequency the more music material you will encounter. There is a dominant amount of energy in the octave from 60 to 120 hertz. And the particular application is attenuating the upper bass more than the lowest fundamentals. The problem is there is simply less information and inherent amplitude in the lowest registers.

David

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craig3972

The gain dial is not a volume knob to use to get more output. I would not want to see the gain higher then half way IMO. If the output is not to your expectations, I would investigate the rest of the amps settings, the enclosure design and its location.

The 13w6's should take everything that amp (600wrms/channel) when properly connected. Amp Gain on a sub in a boat should be set at the highest possible output before distortion occurs.

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Murphy8166

I personally think you are underpowering them. I have 1000 watts going to a 12w6 which was a upgrade from the 600 watts I had last year.

I have it tuned correctly and I am careful with it.

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nyryan2001

The gain dial is not a volume knob to use to get more output. I would not want to see the gain higher then half way IMO. If the output is not to your expectations, I would investigate the rest of the amps settings, the enclosure design and its location.

Box design causing an amp to cutout??

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MLA

Box design causing an amp to cutout??

I was speaking towards the current output level of the subs.

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craig3972

Weekend update:

Yes - the speakers wires were connected in paralell causing the amp to see a 1 ohm load. I changed the wiring to series and measured a 2 ohm load to ensure it was connected properly. I did a quick amp tune up in the driveway before heading to the lake. I was able to get a bit more from the HD1200/1 (gain at full). I tested it for just a couple of minuites and then off to the lake. After about 1 hr of cove partying with stereo on full the amp began to get hot and thermally shut off on the big bass hits. I began to back off the gain until the amp would accept the bass notes and not shut off.

I am going to install a fan on the amp bank to try to keep things cooler, but I was thinking about sharing the the amplification duties with a second amp. one for each 13W6. I have a spare MHD750/1 - run one sub on the 750 and the other on the 1200, hoping to keep things a bit cooler. it does sound a bit crazy but i wanted to get some other opinions before doing the work.

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shawndoggy

I can't believe that the gain could possibly be set properly at full unless your source unit is a dimestore am radio?

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Bobby Light

Why don't you just take the guesswork out of this gain issue and set your gain with a digital voltmeter? You don't even need your sub hooked up to do it. For a 2 ohm load JL says the output should be 49.0V. This is your maximum unliclipped signal.

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craig3972

Why don't you just take the guesswork out of this gain issue and set your gain with a digital voltmeter? You don't even need your sub hooked up to do it. For a 2 ohm load JL says the output should be 49.0V. This is your maximum unliclipped signal.

I can do that. I dont think that will solve my thermal overload problem though. I would like to believe that 49.0v is probably about 3/4 gain, this will overheat the amp after an hour or so.

Have you had much success using fans on amps? The heat sinks on the JL amps are so small I cant imagine a fan having too much of an effect.

Head unit is an Alpine CDA-118 - functional , but not a great unit

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Bobby Light

I can do that. I dont think that will solve my thermal overload problem though. I would like to believe that 49.0v is probably about 3/4 gain, this will overheat the amp after an hour or so.

Have you had much success using fans on amps? The heat sinks on the JL amps are so small I cant imagine a fan having too much of an effect.

Head unit is an Alpine CDA-118 - functional , but not a great unit

Might be 3/4 gain but might not be. At least you'd know. I use fans for my amps but they are enclosed so it's a must, I can bang all day 8+ hours without any issue whatsoever.

Edited by Bobby Light

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craig3972

Might be 3/4 gain but might not be. At least you'd know. I use fans for my amps but they are enclosed so it's a must.

Mine are enclosed - sort of - under a lift up seat. I will open the compartment when the stereo is playing to get some air flow.

Earlier in this thread I had asked about the amount of power to run a 13W6, some suggested about 1000wrms was adequate. My question; is the 1200 watts split between two 13W6's making the amp work too hard for these subs? would two separate amps run more effectively/ efficiently?

Bobby - the three way valves you suggested work fantastic for my extra ballast bags - thanks for the tip!

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jk13

Also make sure your amp is on stand-offs for airflow underneath and there are no lifejackets or other gear stuffed in around them. Then use fans as needed.

And yeah, set the gain properly, don't just guess.

Amp will only do what it will do. Only cares about input voltage (setting gains) and output resistance, which you have corrected. It's not "working too hard", just doing what it was designed for. Wether the system needs more power is up to you. But if I used two amps on two matching subs, I'd do my best to use matching amps.

Edited by jk13

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Bobby Light

Mine are enclosed - sort of - under a lift up seat. I will open the compartment when the stereo is playing to get some air flow.

Earlier in this thread I had asked about the amount of power to run a 13W6, some suggested about 1000wrms was adequate. My question; is the 1200 watts split between two 13W6's making the amp work too hard for these subs? would two separate amps run more effectively/ efficiently?

Bobby - the three way valves you suggested work fantastic for my extra ballast bags - thanks for the tip!

No problem those little valves are nice.

As far as the subs, I think you said they are sealed? You might want to build some new boxes and go ported if you're looking for more output. I think you've reached the threashold of your current setup.

Two separate amps will give you more headroom if they have the right specs and lead to greater efficiency if it's setup properly.

Edited by Bobby Light

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Earmark Marine

Take the good advice given above on using a voltmeter to set the gain according to a particular output load. It's the most objective method available if you are not concerned with level matching to other components. If you do that the thermal issue is likely to go away.

Also, keep in mind that when the voltage drops all amplifiers (transistors in particuler) dissipate heat less efficiently. While the amplifier may be strictly regulated and therefore maintaining a constant voltage to the output section, the power supply is still challenged by low voltage.

Choking the supply with inadequate wire gauge, cheap aluminum alloy wire or poor terminations can really contribute to an amplifier over-working.

Stand offs are a good idea. Fan cooling effectiveness is multiplied many times with the use of a shroud.

Keep in mind that the 750 and 1200 share the same heatsink mass so the 1200 has to dissipate 250 watts of heat at full power versus 150 watts on the 750. This would be a non issue in an air conditioned vehicle cabin. But you are definitely pushing it in a boat during the summer months.

Many people are running much more power on similar subs with comparable voice coil sizes so I like the idea of running two amplifiers. 600 watts per each sub is a tough load on the amplifier and light on power as compared to the subs' potential.

Please consider all of these things. Hope it helps.

David

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craig3972

Take the good advice given above on using a voltmeter to set the gain according to a particular output load. It's the most objective method available if you are not concerned with level matching to other components. If you do that the thermal issue is likely to go away.

Also, keep in mind that when the voltage drops all amplifiers (transistors in particuler) dissipate heat less efficiently. While the amplifier may be strictly regulated and therefore maintaining a constant voltage to the output section, the power supply is still challenged by low voltage.

Choking the supply with inadequate wire gauge, cheap aluminum alloy wire or poor terminations can really contribute to an amplifier over-working.

Stand offs are a good idea. Fan cooling effectiveness is multiplied many times with the use of a shroud.

Keep in mind that the 750 and 1200 share the same heatsink mass so the 1200 has to dissipate 250 watts of heat at full power versus 150 watts on the 750. This would be a non issue in an air conditioned vehicle cabin. But you are definitely pushing it in a boat during the summer months.

Many people are running much more power on similar subs with comparable voice coil sizes so I like the idea of running two amplifiers. 600 watts per each sub is a tough load on the amplifier and light on power as compared to the subs' potential.

Please consider all of these things. Hope it helps.

David

one last question - running one sub off the 750 and the other off the 1200, do you see any operational problems with this setup? Remember these are the boat shaker subs in lockers.

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Earmark Marine

Craig,

I see no issue unless you try and make the smaller amplifier keep pace with the larger amplifier. I would set the input gains on both amplifiers to match the voltmeter reading as intended for the smaller amplifier. That way you will have a balanced 750 watts to each woofer and double the thermal capacity as compared to your present circumstance.

Just remember how much harder a boat shaker (both the amplifiers and the subs) is having to work from within a compartment versus a direct radiating situation (four times as hard for the same output). The rear bulkhead and engine/storage hatches are built specifically to attenuate engine noise. As a result the voltage drop at rest is accelerated four times faster. And, that voltage contributes to the thermal challenge. The resulting bass attenuation in this application also makes it much harder to hear the audible signs of clipping so product failures are more frequent.

David

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craig3972

where do i get the sine wave reference CD signal to test the voltage? what do others use?

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