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Rockford vs. JL amplifiers


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otter 
Copper - Posts: 61
Copper spacespace
Joined: November 28, 2005
Location: United States
Posted: March 10, 2006 at 11:16 PM / IP Logged  
Hey all, I am confused as to what I have just heard in my car.
First, here is my system configuration:
Pioneer AVH-P7500DVD head unit
MB Quart QSD-213 (5.25 inch Q components) front speakers
stock rear speakers running off of deck power
Boston G5 12" sub in custom fiberglass box
all in an 06 Subaru STI
I have had a Fosgate Power 551x (4 channel) running in a Bi-Amp configuration (not sure if this is the right term, I am running the woofers from one set of outputs and the tweeters from the other set of outputs, which would usually be front/rear)
For the sub I have been using a fosgate Power 550S (2 channel, bridged)
Today I took the amps out of my car to paint them, and get them ready for the final install. I replaced them with some JL slash series amps, not expecting to hear any noticeable difference. Unfortunately there was a difference.
The amps that are now being used are JL's Slash 300/4 and 500/1
the highs are cleaner, the vocals are clearer, and the midbass is tighter. What gives? Why would these JL amps sound so much better than my Fosgates? I always thought that my Fosgates were tip top.
coppellstereo 
Silver - Posts: 785
Silver spacespace
Joined: November 21, 2005
Location: United States
Posted: March 10, 2006 at 11:25 PM / IP Logged  
Their old stuff was really great!!! Seems that the more 'commercialized' they become the more downhill their product slides. Ever since retailers have started carrying their stuff ... we have all been sad
Can you give us the specs on your speakers, and tell us which speakers are running from which amp? Maybe we can help you figure out what is going on!
otter 
Copper - Posts: 61
Copper spacespace
Joined: November 28, 2005
Location: United States
Posted: March 10, 2006 at 11:38 PM / IP Logged  
The fosgate amps are a few years old... one from 00 and one from 01 (not sure if this constitutes old). The MB Quart Qs are running off of either the 551x (rockford) or the 300/4 (JL) and the sub is running off of the 550S (rockford) or the 500/1 (JL).
the front speaker specs are:
Power Handling     
70 - 150 W
Impedance     
4 ohms
Sensitivity     
3,2 W (90 dB/1m)
Frequency Response     
50 - 32.000 Hz
Crossover Frequency     
2.400 Hz
Crossover Slope     
12/18 dB/octave
I'm not so worried about the sub. It hammers with either amp, and is quite clear and crisp.
willdkartunes 
Copper - Posts: 250
Copper spacespace
Joined: February 01, 2006
Location: United States
Posted: March 10, 2006 at 11:40 PM / IP Logged  

coppellstereo is right. I used to think very highly of Rockford. I still have some of their old subwoofer series that they no longer make. That was almost a decade ago and now I'm not too sure about RF's product line... It seems all right I guess, but nothing what it used to be. I agree they have been going down hill.

As for the JL Audio amplifier switch, that's pretty much a no-brainer. JL makes some very awesome amplifiers that are built to the highest quality. Their amplifiers have very low THD and are efficient and reliable when it comes to their power output. I love JL's amplifiers and if you can afford them, they are a very good amp to purchase for someone who wants their speakers to sound clean and loud. Keep in mind that many other companies can deliver this great performance too at a much more affordable price.

I do really like JL Audio, I just think they should come down on their prices a little. But hey, as long as their products are selling then why lower the price, right?

Do whatever makes you happy in life without diminishing the happiness of others
coppellstereo 
Silver - Posts: 785
Silver spacespace
Joined: November 21, 2005
Location: United States
Posted: March 10, 2006 at 11:49 PM / IP Logged  
Are you using a crossover for the mid's and tweeters?
Or are/were you just running them off of seperate channels of the amp? If you were, then you would be sending the same signal to both sets of speakers, this isnt a good idea. A crossover will seperate the signal into highs and lows and distribute to the speakers.
The only thing you changed was the amps? Did you change the way that you hooked them up to each component?
otter 
Copper - Posts: 61
Copper spacespace
Joined: November 28, 2005
Location: United States
Posted: March 10, 2006 at 11:57 PM / IP Logged  
The front and rear have seperate crossovers (active) that I have crossed seperately, also the components have passive crossovers crossed at 2,400Hz.
The amps were the only change, exact same wiring etc.
otter 
Copper - Posts: 61
Copper spacespace
Joined: November 28, 2005
Location: United States
Posted: March 11, 2006 at 12:14 AM / IP Logged  
whoops, I should have said that those active crossovers are built in to the amps. Seperate inputs (Front for woofers and rear for tweeters)
I think that answers itRockford vs. JL amplifiers -- posted image.
boardinbum 
Silver - Posts: 358
Silver spacespace
Joined: February 07, 2005
Location: United States
Posted: March 11, 2006 at 12:06 PM / IP Logged  
Yeah, I wouldn't really even consider JL amps and RF amps to be on the same level. JL produces a much higher quality product.
jvillefinest 
Copper - Posts: 255
Copper spacespace
Joined: December 29, 2003
Location: Florida, United States
Posted: March 11, 2006 at 1:14 PM / IP Logged  

JL amps are a little more pricy but you get alot more technology then you would with another amplifier. Even an amplifier that is on the quality level as JL. JL amps are fully regulated. Which something that only a handful of companys do. Between 1.5 and 4 ohms its putting out full power, and between 11 volts and 14.4 volts your getting full power out of the amp. Any of the slash series amps are TERRIFIC amps, there are better out there but not much better, and for the amount of technology the price is justified.

2007 Acura TSX
SQ setup in the works
otter 
Copper - Posts: 61
Copper spacespace
Joined: November 28, 2005
Location: United States
Posted: March 11, 2006 at 3:22 PM / IP Logged  
I guess I'm just gonna leave the JLs in then. Wow, and to think I almost sold them, without even listening to them. Thanks for the info guys,
oh yeah, one more question:
The Boston G5 sub is a 4ohm sub (dual 2ohm voice coils, with 1 set of connecting posts)
I bought the 4 ohm model b/c I was using a 2 channel amp to run it (2 channels bridged to 4ohm speaker = 2ohm load at amp)
Now the JL is seeing a 4ohm load b/c it is a monoblock amp.
Am I understanding the literature correctly that it will still put out 500w RMS?
Are there any downsides to running it at 4ohms?
thanks for all of the help guys
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