Speaker Saturation

[AdeL]

Guys

I don't know alot about sound systems but I am an electronics engineer so understand the principles, so don't hold back on the techie stuff. I have an amp that can produce 400watts bridges and I think about 105 watts per channel (2 channels). I removed my tower speakers because I don't listen to music that much. When I do listen though I now use the stock speakers in the boat, original malibu 50 watt speakers. When I turn the music volume up the two back speakers make an absolutely awful sound, like they are suaturated and can't handle the power. The two front speakers are however OK. Before I replace the two back speakers, I don't know if the '+' & the '-' are going to teh correct terminals on the speakers. If they are all not the same polarity can this cause the saturation, or do I just need to upgrade to more powerful speakers. And if so why don't the front speakers saturate?

[Bartdude]

Try wiring the front speakers to the back terminals and vice versa. Probably the speakers are blown but verify the amp since it's easy to just swap speaker connections.

Reversing the polarity of the speakers will just cause the sound to be out of phase I believe and potentially sound "not right". It shouldn't make the sound awful or blow the speaker.

[Earmark Marine]

Check the polarity by unhooking the amplifier and using a AA battery to click each speaker momentarily. It will move out or move in. All speakers should move in the same direction. Label as you go. When the polarity is opposite the speakers lack warmth, sound like independent sources and sound better with the balance to one side. When the polarity is the same then the speakers have more midbass and sum for more output when the balance is centered. So there are both visual and audible clues.

Saturation is when the electrical power coming into the speaker continues to increase but the acoustic power coming from the speaker begins to fall off as a ratio. All speakers gradually saturate as they are played louder since they heat up, magnetic strength isn't linear, mechanical suspension limitations, range of voice coil sweet spot, fighting inertia, etc. I don't think what you are describing is necessarily saturation.

When a speaker makes an abrubt and foriegn sound (blap) that is timed with music and amplitude demands then check the following areas:

*Amplifier load. Minimum 2-ohms stereo. Minimum 4-ohms bridged.

*A problematic amplifier. Easy enough to check by reversing channels and speakers.

*Lack of front to rear acoustic isolation, like a speaker mounted directly next to an open coaming pocket. An undamped speaker is essentially running unprotected.

*A warped speaker midbass cone, outer surround separated from the cone or a separation between the interior joint of the spider/cone/voice coil. Do a close visual and physical inspection of these parts.

*Speaker damage that can be checked using a multimeter to compare the DCR of all speakers. A 5 percent deviation would be okay. A 15 to 20 percent deviation means you have the beginnings of a failed speaker.

*Manually press the midbass cone in at several even points around the outside...slowly and carefully in a centered manner. If you have substantial VC rubbing/drag the speaker is bad. However, uneven pressure or rocking the cone will make a perfectly good speaker internally rub.

*There should be no equalization or bass boost used on the amplifier.

*Even if you do not have a subwoofer you should still run in-boat coaxials in the highpass mode. A 6.5" will make virually zero contribution below 60 hertz so you might as well protect it from long excursions below the point where it produces.

David

[AdeL]

Thanks guys, some good recommendations, I'll follow your suggestions to try and figure this out.

regards

Adrian

[AdeL]

Guys

It turned out to be a bad earth on the amp. I had a play around today and was watching the LED on the amp as I was testing various things. I noticed that the green LED flashed when the volume was high. I also noticed that some of my gauges, like the water temp went straight to the high stop. I connected the amp directly to the battery and the problem went away. I then used the existing live wire but used an earth straight to the battery and all was well. When I bought the boat I new the wiring needed a do over. This has just raised the re-wire on my priority list.

David, I never new some of the things you suggested and I'm still going to use some of your advice. Thanks for the help.

Ade