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Is My New Alpine System Underpowered???

rpr

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I just installed my new system and I am a bit disappointed. I'm trying to figure out where I went wrong, or whether I was just expecting too much of the HU's internal amp.

Here is the setup: Alpine CDA-7894 HU powering Alpine SPR-174A 6.5" coaxials. I did not think I would need an external amp with the 27W per channel RMS the HU puts out (60W per channel peak). I am not looking for sonic booms here, just a decently powered and matched system.

I replaced the stock HU first with the Alpine 7894 and that made a huge difference from my stock setup. But replacing the stock 5"x7" Ford speakers with the Alpine SPR-174A coaxials really didn't seem to give me a noticeable improvement. I expected a drastic difference with the upgraded speakers (they are rated at 40W RMS and they use an external 12db crossover).

Is my 27W per channel RMS Alpine HU just underpowering my 40W RMS Alpine speakers? I really expected more out of this setup. Any thoughts would be greatly appreciated. Tx!
 
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icon34

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More than likely the answer is yes to expecting too much from your HU amp. You should use an external amp to power the speakers whenever possible. Even though your HU is rated at 27RMS that was likely measure using a 14.4 volt source which you will not be able to deliver. I would be on the look out for a nice 2-4 channel amp(depending on if you replaced 1 or 2 pairs) that can output 50 or so watts RMS.

Or I could just be plain wrong, in which case, someone will surely correct me.
 
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rpr

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I have a very old (maybe 8 to 10 years old) Kenwood 2 channel amplifier (KAC-8200) I just dug out of storage. Specs are as follows: 95W per channel @ 10% THD; 75W per channel @ 0.5% THD; 60W per channel @ 0.03% THD.

If it still works, see any problems in using this to power either my Alpine coaxials (rated at 40W RMS, 160W peak) or my Alpine component set (rated at 50W RMS and 200W peak)? Will this amp overpower these speakers (and risk blowing them) or am I within a safe tolerance margin? :confused:
 
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rpr

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Actually, there are a couple of other things that could be causing a problem:

1) The length of the speaker wires. They are the same on both sides, but I left quite a bit of coiled wire on both sides that is not needed (all the wire provided with my crossovers were not needed since I tapped into the stock wiring, but I left them coiled in the door and did not cut the excess off). I did a search on this, and it seemed that most people were of the opinion that this should not matter.

2) I don't have the HU grounded directly to the chassis. I tapped into existing chassis ground leads in the factory harness. They were pretty thin wires. I'm not sure what symptoms would be associated with a weak chassis ground. Could this cause my speakers to sound underpowered and breakup/distort easily?
 
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icon34

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I doubt that the extra length of the speaker wire is the problem unless we are talking about 75-80 foot worth and even then I doubt that it would be a lose of signal strength that would be noticable.

Looks like the specs on that Kenwood amp should be fine to run the new Alpines as long as the ohms rating is equal with the speakers. You don't really damage speakers unless you cause distortion or clipping. Try the amp and let us know the results.
 
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Explorer94GV

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Ya i think you excepted to much out of the hu. Trust me you can get them to sound good i have the Alpine SPS series 6.5 speakers and have a rockford fosgate 100.2 powering them and than when i hook them up to my 200.4 there is a big difference. That extra 25 watts rms can make a big difference. Amp them with the kenwood it will be worth it.
 
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jonny 5

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rpr, do you have any pics of the alpine in your truck, I just want to see what they look like in an Explorer.
 
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impulsebrklyn

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ok im sorry but the hu amp sucks. There is not enough rms output on the thing to do any speaker any good. Get an external amp. I have a alpine 7873 with infinity kappa 5x7's i put an external amp in. Its a whole new world. Talk about loud, clean distortion free music. I purchase a kicker 800.4 amp so im pushing 100 watts to each speaker @ 4 ohm. If you want to save some money just power the front with an external amp and power the back(fillers basically) with the hu. Next for me is a nice set of components. Chris
 
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rpr

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OK, I just hooked up a ~15 year old, 2-channel Kenwood amp (KAC-8200) I had in storage. It made a world of difference. Maybe in theory power doesn't determine SQ, but it sure seems to have improved the sound in many more ways than just "loudness".

I almost have to wonder if the internal amp of this HU is working. Using the fader, I can barely hear the fronts (that are still powered off the HU), while the rears (that are now powered off a 75W per channel RMS amp) are loud enough to wake up my neighbors.

So I guess I am know in the market for a 4-channel amp. Thanks for all the help!
 
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jonny 5

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Did you run a 10 gauge cable from the battery to the head unit? The new Alpine HU (60x4) suggest doing this for more power. My advice, you won't find a 10-gauge kit, so just buy an 8-gauge kit for an amp and use that.
 
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jonny 5

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???
 
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rpr

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I already had the HU wired directly to the battery with 10AWG wire.

I just purchased JL Audio XR 5x7 components and XR 5x7 coaxials to replace the Alpine SPR's. Hopefully, I will have them installed by the end of the weekend.
 
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Brian's98XLT

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That 60x4 ratting is max power. The headunit is about 15-20 watts rms max
 
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jonny 5

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27 RMS
 
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Rscotts1

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Mounting speakers

Hey rpr, sorry to hear that you are having such a hard time with your door speakers. You were not happy with the first speakers you bought I think they were Alpine SPR-176A's, now you are having problems mounting the new set. As mentioned above, you will need to cut some MDF and make some mounting plates. I know this sucks and is time consuming but hang in there:D . I had to make some plates myself (used 1/2" MDF) to mount my Alpine's, along with Dynamat Xtreme and they sound totally awesome!! Flush mounted the tweets near the side mirror switch...looks very nice.
 
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rpr

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Yeah, I just resigned myself to making the MDF adapter plates. I made them for the 6.5" Alpine's, and didn't think it would be necessary for the 5"x7" JL Audio's, but I am just not happy with the way the 5x7's sit on the stock mounting plate.

I'm a little nervous about the 1/2" MDF though. The JL Audio speakers came with a 3/8" spacer that is necessary for rear clearance. With that installed, the tweeters on the JL Audios are only about 1/4" away from the plastic door panel. Simply by pressing the door panel in a little bit, I can feel it hitting the tweeter.

If I replace the 3/8" spacer that came with the speakers with 1/2" MDF, then there will only be 1/8" of space between the tweeter and the plastic door panel. And the JL Audio 5x7's do not come with grills so there is no protection there. Little too close for comfort if you ask me. However, 1/2" MDF is the thinnest I can find, and 1/4" hardboard just doesn't seem to hold up well enough (the first adapter plate I made was with 1/4" hardboard and it just crushed at the screw mounts when I tightened up the speaker).

So unless anybody has any other suggestions, I guess I will just have to hope that my rear passengers (and rear cargo) do not apply any pressure to the rear door panels near my tweeters.
 
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