Vehicle: 2003 Infinity G35 Coupe with Bose sound system
Radio: Pioneer AVH-P3400BH (DVD receiver)

After researching and reading a lot of posts on G35driver, and recommendations & advice from Wrathernaut and Top Teke (both whom I respect for their opinion, advice, and knowledge) I have decided to replace my Bose amp as part of my audio upgrade. I will most likely get the JL XD600/6 6-channel amp. Again, this will be a straight replacement/in-line swap of the Bose factory amp. I plan on running RCA cable from the radio to the new amp, and then using the existing power and factory speaker wires (from the amp harness) for the driving the amp and new speakers -- if possible (???).

Here is my current setup:

• Pioneer AVH-P3400BH DVD receiver
• JDM double DIN kit and AC controller
• PAC ROEM-NIS2 audio harness
• Metra AXXESS ASWC steering wheel remote control adapter = $70
• 3 pair of Infinity speakers -- Infinity Kappa for the front door and rear deck, and the Infinity Reference slim profile for the rear seat.
• JL 6-channel amplifier (probably a XD600/6 amp -- t.b.d.)

Note -- I have no intentions of adding any sub-woofer(s) to my sound setup at any point in time.

Let me start by saying that I am no audio/sound expert. I have very little understanding of the technicalities, setup and configuration of most of the sound components, particularly regarding speaker, the ohm rating, and how that correlates to the amplifier, etc.

I started my audio upgrade the wrong way (according the the experts): first I upgraded my Bose radio and replaced it with a Pioneer AVH-P3400BH DVD receiver. Next I decided to upgrade all six speakers. I opted to go for Infinity Kappa 62.9i (coaxial) in the front door, Infinity Reference 6032si slim profile in the rear seat side panel, and Infinity Kappa 692.9i in the rear deck. I will most likely replace the Infinity Kappa 62.9i (coaxial) with Infinity Kappa 60.9cs (component) speakers. I had initially decided to go with these speakers because [originally] I was going to keep the Bose amplifier and these Infinity speakers were a simple drop-in replacement for the 2 ohm Bose factory/OEM speakers already there, and it allowed me to use the existing speaker wiring from the Bose amp to the speakers.
Infinity rates these speakers as 2 ohm speakers but state: "True Four Ohms— All Kappa speakers feature two ohm voice coils. Original factory-installed speaker wiring in many cars is 18-22 gauge. This wire, and heating in the voice coil when power is applied, increase the impedance “seen” by the amplifier or head unit. The impedance of Kappa Speakers has been adjusted to compensate for this increase and can be safely driven by any head unit."

My current setup now consists of a new Pioneer radio/head unit and Infinity Kappa speakers in the door and read deck, and Infinity Reference speakers in the rear seat side panel. Considering the money already invested in the radio and speakers (3 pair) I would like to keep these and continue using them (if possible). Thus I will most likely need a 6-channel (or 4+2) amplifier to replace the Bose amp.

I am thinking of replacing the Bose factory amplifier with a JL XD600/6 6-channel amplifier.

Question 1: Will the JL 6-channel amp be OK to drive the 2 ohm Infinity speakers? Is there a better 6-channel amp to consider for the same (or less) price?

Question 2: What is the relation between a speaker's ohm impedance rating (e.g. 2 ohm vs 4 ohm), the number of speakers (channels) and how it correlates to the amplifier?
Can someone explain this or point me to some posts or web sites where I can do some research and further reading, please?

Question 3: Considering my current speaker setup and that I do not want to add sub-woofers to my sound system am I OK with going with the JL 6-channel or should I get a 4-channel and 2-channel amp and bridge them? What advantage will I get from bridging a 4 and 2 channel amp? (I don't understand the technical advantage of bridging multiple amplifiers versus just getting the amount of channels you need in one amplifier). I am not striving to go for a huge amount of power and overwhelming sound...

Again, I know there are many better components and "better ways" of doing this (e.g. running separate and dedicated speaker and power wires, etc), but I am on a budget, my car is old, I don't know how much longer I will keep my car (1~2 years maybe), I did not want to invest many hours/days of labor into the effort. Plus -- I just wanted "better" audio/sound than the original Bose setup (not "perfect") -- I am not an audiophile or sound junkie that can discern the sound between a pair of $500 versus $2,000 speakers... Also, I am not planning on adding sub-woofers to my audio setup. The bass that I get from my current setup is sufficient for MY taste...

Thanks -- Cameron

 

1) That JL will be just fine running all 6 speakers. It is rated stable at 2 ohms. Also, with 300w for those last 2 channels, you have a lot of mobility should you ever change your mind about having a sub.

2) Amps
Amplifiers are generally stable at multiple ohm levels. IE, the JL you are interested in can run at 4 ohms, it's still fine at 2 ohms, but is it not stable at 1 ohm.

Speakers
Speakers are also rated at certain ohm levels as well. So if you have an amp that runs at 4 ohms, but your speaker is only rated at 16 ohms, you will run into problems.

Here's how they work together
Understanding the relationship these two components share will allow you to get more from your system.
The trick about ohm stability is that some amplifiers can be made to produce different amounts of power at different ratings. For instance, the mono amplifier: these amps have only one channel, but depending on what impedance you run them at they will produce different amounts of power. This Rockford Fosgate T1000bd-CP is a mono amplifier that is rated to produce 700w @4ohms, 1000w @2 ohms, and is capable of producing 1000w at 1ohm.
So if you have a 4-ohm MTX T9512-4 12" subwoofer, you would get 700w out of your RF T1000. However if you added a second MTX T9512-4 and wired them in parallel (bottom), you reduce the impedance to 2ohms and your amp is producing 1000w.

There are multiple variations of this sort of thing. Some speakers with dual voice coils that allow you to accomplish the result above with only 1 speaker, or do the same as above and then get them down to 1 ohm, etc. This is where you can begin your research.

Hope that helps!

 

D'oh! Forgot #3.

3) The advantage of two amps is that if you ever decide to go for a subwoofer you can just swap out one of your amps if you're not satisfied with it. Also, now that you're familiar with impedance, you probably realize you have the potential for having two different impedance stabilities present in your system. Like in the example given in answer 2 - 1 amp could be a mono amp running at 1 ohm for your subwoofer, while the other could be running at 4 ohms powering your mids and highs. That being said, the 6ch JL has a pretty hefty sub channel so for someone who is not currently interested in adding a sub, you still have some growing room if you change your mind.

"Bridging" channels just gives more power to a speaker. If you have a 4ch. amp rated at 200w RMS, then you can wire 4 speakers to it, each receiving 50w (200/4=50). If you were to bridge that same amp, you would be wiring only 2 speakers to it but receiving 100w per speaker (200/2=100).

Phsically, all you need to do to accomplish this is run the positive (+) of channel 1 to the positive (+) terminal of your speaker, and run the negative (-) of channel 2 to the negative (-) terminal of your speaker.

The advantage of doing this with your JL 6ch. amp is the increased power you can send to a subwoofer.

 

Top Teke -- once again thank you for your info and helpful advice!

My dilemma now is: (a) go with the JL XD600/6 6-channel amplifier or (b) go with a 2 x amp setup such as a 4-channel amp + 2-channel amp or 2 x 4-channel amps (with one amp having at least a "preouts" (aka "pass-through preamp output") to allow me to connect the two amps to each other using the same original sound input source).

From a cost point of view the JL 6-channel amp is a little cheaper. But I do understand that having a 2 x amp setup for my speaker's 6-channels will give me more flexibility.

If a go for 2 x amp setup, which is a good budget/value or intermediate brand to consider? I have read some nice things about the Kicker IX and JL Audio XD line of amplifiers. Are they good? Which other brands should I consider, giving my requirements and budget?

Thank you -- Cameron

 

No problem. I'm at work right now and don't have access to a computer, but when I get home I'll do some research and let you know.

The best way to find out though is to listen for yourself - of you have any car audio shops around, go poke your head in there and ask questions. Just be up frot and let them know you're interested in hearing new amps and not ready to buy yet.

 

Top Teke -- have you had a chance to look into some amp recommendations? I an very curious (and anxious) to hear your recommendation. I am leaning towards the JL XD600/6 6-channel amplifier as it is a simple "one" amplifier replacement for all six channels. But then again I like the idea of a 2 x amp setup such as a 4-channel amp + 2-channel amp or 2 x 4-channel amps (with one amp having at least a "preouts" (aka "pass-through preamp output") to allow me to connect the two amps to each other using the same original sound input source) to I have room for growth later on.

Again, cost is my limiting factor...

 

Sorry for the delay. With cost as a factor, I think you're going to get the most power for your buck with the 6ch JL. Here's another option for running 2 amps:
JL JX360/4 ($250ish) & Focal FPP2100 ($299ish)

This is more expensive than the JL XD600/6 and you still end up with a less powerful sub channel. However, the advantage is still that you have to option to easily swap out the sub amp down the road at minimal expense if you ever decide you want more (i.e., your buddy gets a louder setup than you ) bass.

Also, the JL JX360/4 and Focal FPP2100 are both class AB amplifiers, whereas the 6ch. JL XD600/6 is a class D. There is an ongoing debate amongst audiophiles regarding which amp type is the best, but I think for your purposes this is merely a point of interest and a good chance to learn about the basics of amp construction.

 

Thanks for the info -- very much appreciated. I will look into the the options you recommended.

One quick question about class A/B and class D amps. Do I understand it correctly that class A/B amps provide less distortion and are a little "cleaner," especially at the lower frequencies (e.g bass, drums, etc), but that class D amps use less power and generate less heat?

I am considering installing the JL XD600/6 amp in the same spot where the Bose amp used to be, so free flowing air will be a little restricted. In this case I think a class D amp might be a better choice?

Last question (I promise ) -- can I safely remove the Bose amplifier by unclipping the harness connectors and removing the Bose amp? Or is there some functionality provided by the Bose amp and/or wiring harness that require me leaving the Bose amp hooked up?

Thank you -- Cameron

 

1) Theoretically, yep. However there are plenty of folks who say they can't hear the difference. Also, yep. D amps are more efficient.

2) I think you'll be fine in there even if airflow is restricted. Whichever way you end up going, 1 or 2 amps, you'll have plenty of headroom so cooling shouldn't be an issue.

3) Really the only functionality provided would be if you were going with front soundstage components only - then you could still use the Bose for your 4 rear speakers if you really wanted to. But even then I'd fade the rears out