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Enclosing Speaker Backs in Plastic?


rangerenthiusiast

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Hey, folks. Hope this is the right place for this thread. My ’92 Ranger Supercab has four blown speakers, so I finally ordered some new Kenwoods through Crutchfield.

When I had the driver’s side door off recently, I noticed that whoever put the last set of speakers in put some heavy duty plastic in there before pushing the speakers into the mounting holes (thus protecting the backs of the speakers from potential rain water that might get down into the doors). I feel like I’ve seen factory-installed plastic sheeting inside of vehicle doors before, presumably for the same reason. The only thing I don’t like about the idea of using more plastic for the new speakers is that it seems to me like they would cause condensation to build up inside.

What do others here usually do about this? Leave the plastic out or put it in? Is there any other material I could use that would shed water from potential leaks, yet be more breathable?

Thanks! :icon_thumby:
 


RonD

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You do the same thing in homes if you use in-ceiling speakers or in-wall speakers if the back side is on an outside wall or unheated attic space, same for electrical boxes or switches, its a vapor barrier and prevents condensation.

So use the plastic, it should wrap around the back side of the speaker and then around the front side edge, so it is held in place by speaker bolted to the door frame, tape where wire goes thru plastic
 

rangerenthiusiast

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You do the same thing in homes if you use in-ceiling speakers or in-wall speakers if the back side is on an outside wall or unheated attic space, same for electrical boxes or switches, its a vapor barrier and prevents condensation.

So use the plastic, it should wrap around the back side of the speaker and then around the front side edge, so it is held in place by speaker bolted to the door frame, tape where wire goes thru plastic
Hey thanks, Ron! So condensation won’t build up inside the plastic? No need to poke a hole in the bottom of it for drainage or anything? :icon_confused:

I really appreciate all your help on my many, many threads. :icon_thumby:
 

rangerenthiusiast

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Sooooooo... I put the speakers in on my one day off - big disappointment. Sounded like crap and no bass response at all. Pushing the volume past about 25% leads to major sound breakup.

I’m guessing that the PO (who’s an idiot), wired things wrong on the back of the head unit so that the power being supplied to the speakers is insufficient. Going to pull the head unit out and check things over. Anything I should be looking for? Don’t have a lot of experience with stereo equipment, but I’m pretty handy...

Thanks for any input.
 

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No, don't poke a hole in the plastic.


Are they Two-Way speakers?

Separate tweeter(small speaker in the center), and woofer(larger cone) behind it

Picture here: https://pisces.bbystatic.com/image2/BestBuy_US/images/products/6065/6065200_sa.jpg;maxHeight=640;maxWidth=550

If so it will have a "Crossover" circuit board on the back where the 2 wires connect.
Crossover sends high frequency "notes" to tweeter and low frequency to Woofer.
And this circuit can fail, but..............only 1 speaker, if both sound bad then not a crossover issue.

Impedance is the resistance thru the speaker's coil(s), most speakers are 8 ohms, but can be 4 to 16 ohms.

Amplifiers are rated for the impedance they can "tolerate" and work best with.
Digital amplifiers are less "tolerant" with impedance out of their range.
0 ohms is a dead short, anything under 3 ohms will cause issues with most amplifiers

As you increase volume the ohms at the amplifier will go down, lower frequency "notes" cause a drop in ohms

It could be one of the wires in the doors is chaffed and shorting to vehicle ground or the other wire, this would cause what you describe, amplifier is crapping out because ohms are dropping under 3.

Pull the radio and test each speaker wire with ohm meter, should see between 7-8 ohms on each pair of wires.
If one pair is lower it will cause what you describe, because it effects all channels on the amp.


WATTS, just FYI
Audio watts are a bit different than electrical watts.
20 watts is not twice as loud as 10 watts
100 watts is twice as loud as 10 watts..............to get 2 times the volume you need 10 times the watts

In a vehicle 20-40watts is VERY loud, so most factory system fall in that range.
And so factory speakers also fall in that range.

To get twice the volume you would need to go to 400watt amp, but you would also want to change speakers to handle the higher wattage.
Changing from a 40watt amp to a 100watt would make much of a difference
 

rangerenthiusiast

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Hey, RonD. Thanks so much for all of the in-depth information as always!

I placed the speakers in some heavy-gauge plastic during installation, as recommended. Didn’t poke any drainage holes in the bottom. And yes, they’re two-way speakers.

I’ll plan to pull the head unit and check things out tomorrow. Hopefully, the wiring will be more-or-less self-explanatory. If I don’t find anything wrong there, I’ll start looking for shorts in the pathway. I do have an ohm/voltmeter, but have only used it a few times for testing voltage. Do I assume correctly that for the tests you’ve outlined, I should be turning the dial indicator on the meter to the “ohm” symbol (looks like the omega character from the Greek alphabet)?

Thanks again for all the help and support. I’ll report back with my findings soon!
 

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That is correct. Meter should be set to ohms (symbol is omega) and only test "de-energized" wires on this setting. Testing live wires on the ohms setting can damage the meter (or worse, depending on how high the voltage )

Sent from my SM-G960U using Tapatalk
 

rangerenthiusiast

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That is correct. Meter should be set to ohms (symbol is omega) and only test "de-energized" wires on this setting. Testing live wires on the ohms setting can damage the meter (or worse, depending on how high the voltage )

Sent from my SM-G960U using Tapatalk
Sooooooo... If I’m understanding things correctly, I should disconnect the wires from the back of each speaker, then connect one meter lead to one wire and the other to the remaining one (with the key off and the head unit powered down).

The resulting ohm reading should indicate what the impedance of the signal sent by the ohm meter is for the loop created by those two wires and the head unit they’re connected to, yes? If the reading is out of spec, then either the wires are hooked up incorrectly on the back of the head unit, the head unit is bad (unlikely), or there is a short somewhere...

Does that sound correct? Thanks a lot, ericbphoto!
 

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Slightly backwards. If you disconnect the wires at the speaker, then you would put you meter leads on the speaker terminals to measure the speaker. However, it might be better to disconnect st the back of the head unit and connect you meter leads to each pair of speaker wires there to measure the whole circuit for each speaker (speaker and wiring combined). In some cases that could show you if there is a wiring problem going to one of the speakers.

As a side note, in case you are interested; your meter will actually be reading the resistance of the speaker and wiring. That is "close enough" for troubleshooting. Impedance is actually a combination of resistance plus the reactance of the circuit. Reactance takes into account inductors (coils, such as the speaker) which resist changes in current flow and capacitors, which resist changes in voltage. But that would be a good Google search for you on a rainy day.

Sent from my SM-G960U using Tapatalk
 

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Yes, +1 ^^^

If your meter has different OHMs settings use 200, lowest setting.

After you select OHMs touch the two meter probes together and you should see meter change to 0 in the display
0 ohms is a dead short

Two speaker wires at the radio end should show 4-8 ohms depending in the speaker.
If you see 7.5 ohms then they are 8 ohm speakers

All speakers should be the same OHMs, i.e. if one set of wires shows 7.6 ohms then the other should show about the same, 7.1-7.9 ohms is the same, if a pair shows 4.5 ohm or under then there is a wiring problem or mismatch speakers, some one installed wrong kind of speaker

Radio wiring diagrams here: http://www.therangerstation.com/how-to/interior-and-interior-electronics/ford-ranger-radio-wiring-diagrams/
 

rangerenthiusiast

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So, I’m at a total loss here. I pulled the head unit out, snipped all of the speaker wires at the butt splices, and tested each pair with the ohm meter set to 200 ohms. Each pair registered between 4.3 and 4.5 ohms. So apparently, there’s no short, but the speakers still sound like crap. I even tested the old Ford factory speakers (since they were out) and got similar readings, so it doesn’t appear as though the new speakers are a mismatch to what was in there originally. What on Earth could be the culprit here?

On a side note when I cross the two probes on the ohm meter (as RonD suggested), it doesn’t go down to zero. It goes to 0.7. Is this an issue?
 

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Do you trust the head unit itself?
 

rangerenthiusiast

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Do you trust the head unit itself?
I don’t know, as I don’t have a spare that I can hook up to test the theory. It was in the truck when I bought it and seems fairly new tech-wise (i.e. - it’s Pandora capable, can receive cell phone input, USB, Bluetooth, etc). Does anyone know of any way to test it that doesn’t involve putting a different one in?
 

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Whats the model number of the Radio?

Look up its specs, it needs an amp rated down to 4ohms.
 

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