Amp vs head unit for rear fills

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swede

Copper - Posts: 125

Joined: July 31, 2004

Location: United States

Posted: May 22, 2005 at 9:45 AM / IP Logged

I currently have a Clarion head unit (DMX5555z) thats 40x4 (14x4 RMS). I really only have the room to add one amp - it is 110x4 RMS @ 4ohm.

My hope is to run the fronts (Boston 6.53) at 110w, then to bridge the rear (280w) to the sub (Boston 12.5Pro). I know that some head units are more accurate and under-rated for their outputs then others.....will the Clarion run the rear fills (Boston 6 1/2 coax) adequately?

Thanks in advance.

Subtlety is EVERYTHING.

sedate

Silver - Posts: 1,173

Joined: July 03, 2004

Location: Colorado, United States

Posted: May 22, 2005 at 10:29 AM / IP Logged

I've wired cars this way a few times... the problem you run into isn't the *amount* of power delivered from the HU, more like where that power is delivered along the volume knob. HU's usually start clipping WAYYYY before a preamp-output will.... so it gets real hard to get the gains and volume just right w/o turning the sensitivity on the front speakers way, way up.... I've found installs done this way, while tonally balanced, often have horrid alternator whine when the vehicle is actually moving b/c the gain needs to be set so high to match up with how low on the volume knob the HU power will start clipping.

Better decks, (and Clarion is, IMO, a better deck), can get around this somewhat by judiciously fading the HU to the front.. you might find it all matches up perfectly. Do it and see how it sounds.

BTW, that looks like a killer system you got listed there... I'd be exited. What kinda amp are you using?

"I'm finished!" - Daniel Plainview

swede

Copper - Posts: 125

Joined: July 31, 2004

Location: United States

Posted: May 22, 2005 at 12:05 PM / IP Logged

Thanks very much :) The gain issue had crossed my mind (still does), I was just concerned about such a lopsided power output from front to rear. I had even thought about scrapping the rear fills altogether.

My car is a wagon that I use alot so it can't be turned into a boombox on wheels - I like hidden "stealth" installs anyways with complete original usability of the vehicle - make it look like it came that way Amp vs head unit for rear fills -- posted image.

Amp vs head unit for rear fills -- posted image.

My sub box is molded to fit inside the spare tire well (sub requires 1 cu ft, mine figures at .979) while still keeping - and accessibility - to the spare.

I REALLY wanted a JL 500/5 - but the space was just too close - was a squeeze BEFORE wires - heh heh. There was an area to fit it but I wasn't happy with the ventilation. I have an Infinity 7541a - good power that fits. I have never had one before but have heard (and read) great reviews on it. Just wish it had a 5th channel in the same housing.

Know anything about it?

Subtlety is EVERYTHING.

hawn13

Copper - Posts: 171

Joined: April 13, 2005

Location: Hawaii, United States

Posted: May 22, 2005 at 5:50 PM / IP Logged

another idea if your amp is 2 ohm stable most are you can run all speakers off front only draw back if it matters you won't be able to fade front to rear with your speakers

swede

Copper - Posts: 125

Joined: July 31, 2004

Location: United States

Posted: May 22, 2005 at 8:32 PM / IP Logged

I thought about that too :) The fronts will handle loads of power - and it seems with all the Bostons I've had, they're power hungry anyways. The rear fills (NX67's) are rated to 160w, so I suppose they'd all take it.

Subtlety is EVERYTHING.

sedate

Silver - Posts: 1,173

Joined: July 03, 2004

Location: Colorado, United States

Posted: May 23, 2005 at 10:04 AM / IP Logged

swede:

Your taste in equipment is excellent. The entire 'slash' series of amps from JL gives me goosebumps, the 500/5 especially. =) The Boston stuff I know sounds out of this world.. I kid you not I slapped a pair of NX65's in a friends' Sentra getting a PlanetAudio amp and they sounded better than my JL VR series componets... the sound was *amazing*

Haven't heard anything about the Infinity amps at all... prolly very comparable to JBL stuff (same parent) and I've had great experience with them.

Are you running componets or coaxials up front? When I first read "Boston65.3" I thought it was a 3-way comp set just looking at the number.. but I can't find that on Boston's website..

Anyway, I'd be hesitant to wire a car anyway that doesn't provide for rear-volume adjustment in some, even if a roundabout way.. I'd try your original wiring idea with careful gain and fader settings.. if that leaves you cold you could try paralleling all the cabin stuff but that could very possibly have alot more sound behind you than in front... I think this is gonna be one of those things you just have to hook-up and find out. Post back man let us know how you did it and ur results.

"I'm finished!" - Daniel Plainview

swede

Copper - Posts: 125

Joined: July 31, 2004

Location: United States

Posted: May 23, 2005 at 12:24 PM / IP Logged

Sedate - thanks very much for the compliment. Coming from some of you guys on here means ALOT.

The car has a couple of storage bins on the sides in the back that I use to hide tool kits, jumpers, etc. If I can, I'm going to try to re-arrange some things and get everything onto one side. That would allow me the room to mount a 500/5 vertically (anyone have anything to forewarn me about doing that - please let me know now Amp vs head unit for rear fills -- posted image.

), using the storage bin as my extended space. Its all black oem carpet so it should be easy(er) to fab and make it look like they meant to do that.

Glad to hear the NX series are true to form. I took the NX's because they seemed to have better ratings than most "cheaper" speakers plus they would handle 160w. A good long term "filler" - heh heh. My girlfriend has 2 sets of Boston Ralley componets in her car (4.5Frt - 6.5Rr), that although they sound great, aren't what I expected from a Boston component. I won't make a final judgement on them til she gets a larger amp (currently an old Hafler 40x4) - if I can fit the JL in mine, she'll get the Infinity - that ought to wake up the Ralleys. But yeah, the Bostons are like politicians....real power hungry Amp vs head unit for rear fills -- posted image.

And you're right....I can't find anything on the 6.53Pro's either (?!) Yep, they're the 3-way components - I was in a shop that had just installed a set in a Porsche.....finest speakers I had ever heard - and that in a rear engine (noisier) car.

Yeah man.....I'm excited and will definitely get a Pbase or CarDomain acct with some pics when its all said and done.

Subtlety is EVERYTHING.

blg748

Copper - Posts: 194

Joined: October 29, 2003

Posted: May 23, 2005 at 12:55 PM / IP Logged

Hey i was thinking of the same thing. on my HU though it puts out 18WRMS*4. But i planned on using my front component amp and run the rears exactly as hwan suggested. BUT i was adviced to put 8 oHM sandston resistors inline with the rears and this would provide a 6db cut off to the rears. However with my HU i have ability to fade from front to rear. So i might just stick rears to HU power. Anyways good luck with your setup.

stevdart

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Joined: January 24, 2004

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Posted: May 23, 2005 at 4:25 PM / IP Logged

If you run all four in parallel, do so only as a temporary measure until you can get another two channel amp installed. The sound won't be nearly as good as running at the rated 4 ohm impedance. But if you want to attenuate the rear speakers, use this calculator and enter the impedance and the desired attenuation...and connect the resistors like it shows in the diagram.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

swede

Copper - Posts: 125

Joined: July 31, 2004

Location: United States

Posted: May 23, 2005 at 7:29 PM / IP Logged

After doing some extensive measuring, I find it would be easy to install 2 smaller amps (size, not watts Amp vs head unit for rear fills -- posted image.

) so now I have several new options open.

As nuts as this may sound, from the brands I have or am leaning towards, I actually like the ratings (and price) of bridging a 2 channel for the sub rather than just running a a mono. MB Quart, Infinity, possibly JL (my first choice but the largest in size of the 3).

I have a new headliner being made - have re-spray dyed all of the interior panels, and have new carpet on order, so its not like I have to decide by midnight tonight. I've been collecting parts/components for about 6 months now, so another week or two "deciding" between the red Ferrari and the black one isn't going to end the world. Amp vs head unit for rear fills -- posted image.

Sorry if this is skewing from the original topic. Seems the "using the head unit" option is moot at this point - heh heh.

Subtlety is EVERYTHING.

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Amp vs head unit for rear fills

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