Wierd

[eharri3 10+ year member]

So I had an Alpine 9883. Hooked up an Eclipse 4 channel EA4200 to it wired to the speakers at 4 ohms and an Alpine MRP M500 for my sub, also wired to the sub at 4 ohms. When I checked the gain with tones I found clipping set in on the Alpine at 29 out of 35. I set the Eclipse 4 channel gain by ear using tones and a throwaway speaker then double checked with a DMM. Both front and rear gain dials ended up almost precisely at the 2 volt mark to match my HU's rated voltage output.

I set the sub by ear and double checked with a DMM. Ended up at a tad below .5 volts out of an input sensitivity range of .2-4 volts on the gain dial.

Changed head units to a 4 volt radio and added Hertz speakers to replace my eclipses, then bridged the amp to the HErtz HSK 165s. Re-checked gains again. The eclipse seemed to end up perfect at almost exactly 4 volts. The Alpine, I re tuned by ear to listen for distortion at 28-30 and to ensure it increased sub volume in as linnear of a manner as the mid/high amp. Then today I just double checked multiple times with a DMM. At a volume level of 27 out of 35 with a 50 HZ 0 DB test tone, I'm getting the proper voltage on the meter and everything sounds perfect but the notch is only barely above the .5 volt mark and still not at the half-way point between .2 and 4 full volts. Measurements are taken with EQ flat, crossovers on full, and Sub volume on 15 at the head unit.

Im just curious as to other's opinions on why the gain settings on the Alpine keep ending up so far off from the markings on the dial: Could this be attributable to the amp's gain dial markings being way off, could the sub pre-amp out be putting out significantly less voltage than the rest of the HU outputs, or could there be some sort of problem in the wiring preventing my amp from receiving the proper voltage from the head unit? It sounds perfect and I'm not inclined to mess with it unless someone in the know thinks it signifies some sort of problem that should be diagnosed. Maybe if people could tell me where their gain dial is set by the markings and where it ended up using textbook tuning techniques it would help.

It's been like this through a 2 volt and a 4 volt HU so Im inclined to believe it's either a normal quirk for this amp or else a problem with it or its wiring.

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[eharri3 10+ year member]

Bump with cliffnotes:

When I use the DMM to tune my 300 watt MRP M500 to deliver 300 watts to my 250 Watt Pioneer Premier at 4 ohms off a 4 volt head unit input sensitivity level ends up at only a bit more than .5 volts. Setting was done with Sub level at 15, EQ flat, volume at 27 out of 35, then I backed off a tad from there and still am not even at the halfway mark on the gain dial. Sounds perfect but wondering if this could signify a problem with my setup that its a 4 volt head unit but the amp's gain dial isn't even close to 4 volts.

 

[eharri3 10+ year member]

After doing some research I am hearing that Alpines have been notorious at various times for having weak sub pre-outs and that alot of people have had to set their sub gains at a very different numerical level than the mid/high amp gains to get the same output. Just wondering if anyone else running Alpine's newer line has seen the same issues.

 

[gunz4me 10+ year member]

I have a CDA-9885 in each vehicle and I can say with certainty that with the subwoofer level @ 15, the output still isn't on par with the front/rear outputs. Think of anything under 15 as a cut to the 0 dB threshold!

With all that said, I have found that the subwoofer gain level has to be slightly HIGHER than the front/rear gain levels. Using my 25 to Life Power 1000 as a reference, the subwoofer output on it is about 1/4 turn HIGHER than the front gain. The rear gain is all the way down because I hate rear fill.

One of these days I will get bored, put an o-scope on the front/rear/sub outs and see what the output voltage is at clipping on all of them to verify that the subwoofer output channels are slightly weaker.

 

[eharri3 10+ year member]

The more I research it, the more I believe this has to be the case since the wiring for both amps was done by a very reputable shop and I've gotten the same results with both head units. When you check around other people make this claim about alpines and are told they're crazy but I think it's true. People who measured 4 volt head units found about 3.9 volts on the front and rear pre-outs just before clipping but 1.7-1.9 on the sub pre-outs. This about jibes with what I'm seeing as if I left myself no headroom and went for max sub output at max undistorted HU volume with zero clipping the dial gets close to what I guestimate to be 1.75-1.9 volts. Now that I know it's not just me I'm not worried about it but it seems a bit of a gyp on Alpine's part. After all, all arguments about whether voltage makes a difference aside, they advertise it and they charge for it.

Also more proof of why setting gains just by matching the dial's markings to the head unit rating is hit or miss.