Aftermarket speakers crackling
08-31-2015, 07:51 AM
#11
Elysian - it sounds like your speakers are bottoming out, which is where the voice coil hits the magnet due to over-driving them beyond their mechanical excursion limit. Noises like you describe could be caused by loose mounting like buldozr mentioned, but I'd think you'd hear noises over bumps and rough roads if that were the case. I've also seen loose surrounds or broken lead wires (between the speaker terminals and the voice coil) cause similar problems.
I suggest taking the door panel off and taking a close look at the speaker while you play them loud enough to cause the noise. See if anything is loose or flapping, and see if you can localize the noise. Then turn the system off and carefully push the speaker cone in and see if you hear any noises or see the surround separate from the frame anywhere.
If you think the noise is caused by over-excursion, you will have to change to speakers with longer excursion or add a sub, and then cross-over the door speakers so they are not handling all the bass. Finding door speakers with enough excursion will be hard, as very few car speakers even have excursion ratings. Generally, speakers with higher power handling should have longer excursion specs, but power ratings are so frequently exaggerated that they are almost useless, as are most of the specs provided by manufacturers. The 30Hz response for the Polks sounds nice, but without a dB range (like ±3dB) that spec is meaningless. I'm sure the speakers you have now can produce sound at 30Hz, the question is how much sound compared to the rest of the frequency range? -10dB? -20dB? You don't know, even with the Polks.
Something else to keep in mind - "shallow-mount" speakers will generally have less excursion because the frame and magnet assembly has to be shorter in order to limit the mounting depth. So you might want to avoid shallow-mount and look for speakers that have a mounting depth closer to 3", but that may mean you'll need spacer rings to keep from hitting the window. Since the Polks are shallow-mount too, I don't think they would be much better than what you have, though someone with direct experience with both speakers might provide better insight.
The 445U is a "Universal" design that will work on any head unit, so yes, you will have to cut and splice the wires. The 445A is the "Alpine" version that plugs directly in-line with an Alpine head unit, so no splicing is necessary.
As far as I know they are the same amplifier, and the 445A that I tested at 14.4 volts input provided 33.1 watts into 4 ohms before clipping. I guess their 45 WPC rating is at some other load impedance, probably some optimal impedance that you'll never see in real life. By comparison, the CD-105 Alpine HU I am using produces 17.1 WPC, very close to the rated 18W. Also, note that if I cranked it up to get 45WPC out of the 445A, it and the HU were consuming almost 18 amps on the supplied 15-amp fuse.
I suggest taking the door panel off and taking a close look at the speaker while you play them loud enough to cause the noise. See if anything is loose or flapping, and see if you can localize the noise. Then turn the system off and carefully push the speaker cone in and see if you hear any noises or see the surround separate from the frame anywhere.
If you think the noise is caused by over-excursion, you will have to change to speakers with longer excursion or add a sub, and then cross-over the door speakers so they are not handling all the bass. Finding door speakers with enough excursion will be hard, as very few car speakers even have excursion ratings. Generally, speakers with higher power handling should have longer excursion specs, but power ratings are so frequently exaggerated that they are almost useless, as are most of the specs provided by manufacturers. The 30Hz response for the Polks sounds nice, but without a dB range (like ±3dB) that spec is meaningless. I'm sure the speakers you have now can produce sound at 30Hz, the question is how much sound compared to the rest of the frequency range? -10dB? -20dB? You don't know, even with the Polks.
Something else to keep in mind - "shallow-mount" speakers will generally have less excursion because the frame and magnet assembly has to be shorter in order to limit the mounting depth. So you might want to avoid shallow-mount and look for speakers that have a mounting depth closer to 3", but that may mean you'll need spacer rings to keep from hitting the window. Since the Polks are shallow-mount too, I don't think they would be much better than what you have, though someone with direct experience with both speakers might provide better insight.
As far as I know they are the same amplifier, and the 445A that I tested at 14.4 volts input provided 33.1 watts into 4 ohms before clipping. I guess their 45 WPC rating is at some other load impedance, probably some optimal impedance that you'll never see in real life. By comparison, the CD-105 Alpine HU I am using produces 17.1 WPC, very close to the rated 18W. Also, note that if I cranked it up to get 45WPC out of the 445A, it and the HU were consuming almost 18 amps on the supplied 15-amp fuse.
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