Scenario: SuperDuty extended cab. Identical component speakers in each door; i.e. the same model numbers. The fronts are a "full install"; that is, both tweeter and woofer, with the crossover in place. The rears are just the woofers.

The fronts sound "acceptable". The rears sound like they're in the bottom of a barrel under a shovel full of dirt -- muddy, boomy lows, and non-existent highs. The absence of highs is easily explainable by the lack of the crossovers and tweeters.

But does the otherwise crappy sound come from poor acoustics in the rear doors? Or another source?

Want to brush up on some theory before tearing the doors apart (uselessly)...

Haven't gotten to install the sub on the factory replacement AudioPhile head unit yet... (sub prices have doubled since I last bought)

-blaine

 

Stock speakers? Play with the stereo settings. Could just be set funny.
The speakers could be bad.

If they have been changed, I say the positive/negative wires could be backwards.

 

This is normal for components when you don't use proper crossovers with matching tweeters.

 

O.k.... guess that means I get to tear the doors apart.

Thanks....

I don't suppose you could explain the "why" behind that, could you?

-blaine

 

Yes, I can.

 

heh... O.k.. WOULD you?



(please?)

-blaine

 

The reason why is 2 parts:

1. You're only listening to the part of the musical spectrum that these midrange speakers are capable of producing.

2. Even though these speakers are capable of producing musical information above their crossover point, they will not sound good above a particular frequency. For Example: If the low pass point of the crossover is set to 3000hz, the speakers CAN play musical information above that, but the crossover (If it were installed) would 'roll off' that musical information above that point. This is designed this way to prevent the midrange speakers from trying to reproduce this musical information. Most midrange speakers usually begin to sound bad at about 2000hz, but those cheap 2-way sets that are on the market usually play them higher anyway. (Which is one of the reasons why the cheap ones sound so bad) You're compounding this issue by allowing the midrange to play all the way up to 20,000hz.

If you're an engine guy, a good analogy would be to think of a camshaft. There are camshafts for racing applications that make the car idle really rough at low RPMs. (1700 or so) The effective RPM of the engine where it makes the most power is going to be in the higher RPM range, maybe 3000-4000 or so. (I'm not using real numbers, nor am I referring to an actual engine. This is JUST an analogy)

Some devices, like midrange speakers, or even camshafts, are meant for a specific purpose. When you use them outside this range, you get crap.

 

O.k....

So what about the low-end sound? the whole "sounds like they're in the bottom of a barrel under a shovel full of dirt -- muddy, boomy lows," part?

-blaine

 

you stated the rears are subs but I bet they are just sitting in the door without an enclosure to seal them

 

I put Polk db571's all the way around in my SuperCab, rears sound boomy around 160 hz, just like you observed. I think its the size of the rear door, not a good enclosure. I also Dynamatted it and sealed the other hole, so its like a big sealed enclosure. I plan on building small boxes for the speakers to go in the door, around 0.2-0.3 cubic ft, sealed, that should help a lot.

 

You've never heard a midrange speaker all by itself before, have you?

Again, it's attributed to more than one thing:

1. Sensory overload. You've got so much garbage coming at you from the top end of the speaker, that you're having trouble with the entirety of the musical information.

2. The speaker is producing the frequencies above its normal operating range, and this can affect the cone control in the lower frequencies.

If you're an engine guy, think of it as buying a camshaft that operates best at high RPMs, but buying an intake manifold that operates best at lower RPMs. To a person who knows nothing about engines, you might think these two things will combine to give you a well balanced, street-able engine, however they actually work against each other. The engine with both parts actually has worse performance than the same engine with only one of the parts added.