Thank you jwmbishop, I was wondering why they would have done that. Now, if I am finding it lacking with my hardtop off and I don't want to degrade the marginal sound quality any further, will getting a better amp resolve the issue or do we need to change out speakers/sub as well?
I would say that depends on how much of an audiophile you are. Some people only need a radio - some need 10K in radio, amp and speakers.
When I was in my 20s with good ears and a well rounded taste in music I would have been tempted to replaced the entire unit (radio amp and speakers) to keep sound quality high. But as the wrangler is versatile (top and door option) the "stage" changes drastically. Imagine Carnegie hall or the Sydney opera (both being places where the spoken and unamplified human voice reaches all seats pretty close to equally) with a roll open roof. The acoustics change so much the object of good clear sound throughout the environment becomes a fast moving target and may even be so drastic as to be un-tunable with gain...
At the US Festival back in the 80s they set up in a natural amphitheater (basically a bowl valley) that was so far across in order to get the high and low freqs to converge at the center and at the same time (time and place convergence of waves makes a huge impact on sound quality - which is basically what modern stereos do with speaker placement and DSP that lets you select between all, front only, rear only, driver only etc for sound quality) Steve Wozniac designed a sound board that would delay the the output enough that when the highs were sent out of the driver (they travel faster) the lows had already been sent! enough so that they would get there (center of amphitheater) at the same time as the highs. The end result was you could see the drumstick strike a full second before the drivers fired and the entire performance looked like bad lipsyncing (but best outdoor concert sound I have ever experienced)!
I can set DSP to front only in my Caddy, go sit in the back seat and its just not as "loud" or defined as in the drivers seat (and my teenager with good ears actually said it sounded like crap)! Set to all its sounds equal in any seat.
to simplified explanation of resonance (speed of sound waves). Note in the equation v = 4f (H + 0.4D) Velocity equals 4Xfrequency times H + 0.4D. Note that as freq (f) is multiplied by four - freq is the LARGEST piece of the puzzle. That's why the wrangler unit sounds different - the freqs are being modified via gain! Not the volume! The more sensitive you7re ears are to this the more noticeable it is. Thats why the jumper wire "works for some" but not others. Its working - but the individual is not experiencing the same physical eardrum response as the the next guy.
Having lost my hearing and wearing hearing aids - mis convergence of multiple freqs becomes noticeably "blurred" to me - ie more volume equals less understanding of subtle vocabulary sounds (like did he say cat, bat, rat or hat etc) when watching TV. Can easily fill in one word by the sentence context - but miss two or three in the sentence and the whole sentence makes NO SENSE. If I play Zepplin on my Jeep stereo I "hear" every word note and sound - simply because I KNOW it so well. But play a new song I have never heard before and I cant understand a single lyric! But in my Caddy (12 speaker bose, 1000 watt) I can catch about 70% of even a totally unfamiliar song. With the roof of the Caddy off I would probably not catch any as the sound goes away from me - not bounced back.
If modifying a wrangler I would first focus on the speakers and their direction. Top off you want them to fire directly at you from in front (the dash speakers could be angled upward more rather than down to the floor - I'm sure our knees enjoy Deep Purple but its our EARS that NEED it - lol) - not down only to be blown away by the wind and momentum (doppler effect condenses the waves ahead of and expands the waves behind a moving object) as the overheads do. Back seats really benefit from the overheads. Top on that would be uncomfortable and not sound as rich. A high end stereo shop can really do a lot here as they have the equipment to measure (without regard to individual ear sensitivity - sensitive to both volume AND direction). But overall I think trying to get quality sound out of a MOVING open air vehicle is chasing rabbits down tea holes. Wind, doppler, other sounds all are working against the goal. Just make it loud enough to hear at 60 and enjoy quality when you arrive at the top of the mountain and have lunch, dinner, beer etc!!!