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Car Forum / Driving, Maintenance, Tuning / Car Audio / September 2004Another one of my JBL problems..
I have a set of 6.5" JBL Decade coaxials, I can't quite remember the model number, but I have them running from the CD player right now (pioneer DEH-1100), as my old amplifier still hasn't been working, but now, what I thought is a rattle, is actually the speaker. It's very odd to me, as they can take 75 watts RMS. The deck is 45 or 40 X 4, if I'm correct, "peak" power. The speaker makes a rattling noise when it is played at a higher frequency, such as 70hz. the lower notes dont seem to do it. Or at least I can't hear it. I took the grill off, and lightly pushed down on the woofer with a finger on each corner, and it felt and sounded like the voice coil was scratching on something. My guess is that from the distortion, the speaker heated up, and "welded" part of the coil. Of what I have read, distortion is the leading cause for speakers to wreck. Am I right on this? However of course, this is a hypothesis based on the knowledge I have. Please help me, I don't want to shell out a couple hundred bucks for a new set of speakers. And is anyone else having issues with JBL? Or is it just me? I have one more amplifier that is still working from them, so we'll see. Thank you. >The speaker makes a rattling noise when it is played at a higher >frequency, such as 70hz. 70Hz is a low-mid frequency. Is the speaker making the sound during mid-low freq. playback or during high-freq. playback? >My guess is that from the distortion, the >speaker heated up, and "welded" part of the coil. That would take a lot of heat. Keep in mind how hot the inside of your doors can get, even when no music is being played. The speakers were designed with this knowledge in mind, and their heat tolerences are pretty high. >Of what I have read, >distortion is the leading cause for speakers to wreck. Am I right on this? Yes. But there are instances where something else damages a speaker. >Please help me, I don't want to shell out a couple hundred bucks for a new >set of speakers. You can get good replacement speakers for $99 a pair and pop them in yourself. But it seems as though you want to try and repair what you have first. If you know how to take the speaker out of the door, you may want to do so and examine it. Steve Grauman I'm sorry, I should have been more secific, I meant higher frequency for bass. But it's around that area. And the speakers are in the rear deck. And the distortion issue was a simple guess. As I am still a newbie. I'll take the speakers out tomorrow, and examine them more closely. But I'm still clueless to what it might have been. > >The speaker makes a rattling noise when it is played at a higher >>frequency, such as 70hz. [quoted text clipped - 28 lines] > it. > Steve Grauman By pressing the cone equally around around the centre you should be able to feel, hear, if voice coil is rubbing. Also playing music at low level will sound distorted when voice coil is rubbing. If as you say there is a rattle at 70 Hz (which is low fequency) this could be something else like the driver not bolted tight enough or something else vibrating in sympathy. In most cases it is distortion from underpowered amplifiers which blows speakers. Never run a system into distortion to avoid risk of blowing speakers. It is amazing how ICE manufacturers have defied the laws of physics ! According to a magazine article many years ago, the maximum r.m.s. power you can achieve from a stereo amplifier powered by a single 12 volt car battery is just 6.3 watts per channel. Maximum of 25 watts per channel can achieved by bridging. The wattages quoted these days are meaningless and should be investigated by trading standards. As regards volume, the efficiency rating of a speaker (db output at 1 watt measured at 1 metre) makes a lot more difference than wattages. 10 watts can be a lot louder say than 100 watts when fed through a speaker of higher efficency. Regards Stefan > I'm sorry, I should have been more secific, I meant higher frequency for > bass. But it's around that area. And the speakers are in the rear deck. And [quoted text clipped - 34 lines] > > it. > > Steve Grauman > By pressing the cone equally around around the centre you should be able > to [quoted text clipped - 15 lines] > by bridging. The wattages quoted these days are meaningless and should be > investigated by trading standards. You should read up on the laest technologies. Switching power supplies generate a much higher voltage resulting in more power available to the speakers. > As regards volume, the efficiency rating of a speaker (db output at 1 watt > measured at 1 metre) makes a lot more difference than wattages. 10 watts [quoted text clipped - 49 lines] >> > it. >> > Steve Grauman |
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