A friend bought an old Rockford amp (400x4) off me a year or so ago. He just wanted a half decent amp, this suited his needs.

It's about 4x50wrms or so, can't remember exactly. He doesn't have a clue about car audio AT ALL, so he keeps believing the bull, and buying stuff like Boss amps, and I get stuck trying to make them work.

OK. His set up :
Sony Deck, 4x45 wishfulwatts
400x4 amp
clarion splits
6x9 on rear parcel shelf in small boxes
2 12" subs (4ohm svc)

Here's the debate.

1. Run speakers off HU, run the subs off one bridged channel each.

2. Run splits off front channels, bridge the rear channels and run subs at 2 ohm mono.

3. option 2 + take those 6x9 boxes out and smash them on the road, then melt them into coasters.

I know the amp does 2 ohm mono all day, every day, and doesn't complain.

Autobarn would like to do option 1, as "the subs would be louder and have less distortion". Less distortion for subs?? When did that really count?

My personal option is that, even with a massive load on one half of the amp, having the splits amped (not run off the HU) would be more beneficial to his system goals (he turns it up, it distorts).

OK, what he terms distortion is most likely him driving the system beyond his limits, so I'm taking this all with a grain of salt, but....

oh yeh, option 4: rob a bank and scrap the lot - start again!




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All electronic devices are powered by magical smoke.......
when the smoke is released, the device will no longer function

Soundstream.....Clarion.....Soundstream.....Stinger.....Orion.....but mostly Soundstream

rockford work thier amp ratings like this,
XXX.Y
where XXX=total RMS output when run at 2ohms per channel, Y=number of channels
so it's put out 2X200, or 4X50 (at 4 ohms)
or 4X100 at 2ohms,
i don't think they are designed to be 1 ohm stable per channel, but they may handle it ok.
what subs are they?
how much power can they handle?
i'd put a HP filter on the splits and run the subs off a bridged pair of channels each, cause 2ohm mono is risky (IMO)
maybe he can buy an el cheapo amp for the splits?

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'96 Mirage, currently resembling a tin can
uninstalled: Rockford RFX9300, Focal 165W3's Vrx 2.150 & 1.500
Power by: HERTZ audison OPTIMA StingerAerpro
TEAM AUDISON

quote:

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where XXX=total RMS output when run at 2ohms per channel, Y=number of channels

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My memory was pretty good then!

The splits are HP'd via the X-Card in the front pair of channels ATM, so they should be fine.

My main query then, is:

Is the advantage of running the subs in 4 ohm bridged mode (ie one per bridged channel) and the splits run of the HU going to be better than flogging the hell out of the amp by running a pair of channels in 2ohm mono and sending the other two to the splits??

I'm not worried about two ohm mono on the amp, as he had a go at doing this himself nearly a year ago, and has been running the 2 subs of one bridged pair for that entire time (in two ohm bridged).

Remember when RF amps were bullet-proof??



------------------

All electronic devices are powered by magical smoke.......
when the smoke is released, the device will no longer function

Soundstream.....Clarion.....Soundstream.....Stinger.....Orion.....but mostly Soundstream

well if the power rating of the amp at 2ohm mono is double what it is at 4ohm mono, then you'd be silly to run run the splits off the HU as you'd be wasting power.
however, as you're running the amp beyond it's specs (as far as i can recall) the power supply could suffer. resulting in poorer SQ up front, and less bass up back.

SO... i'd recommend runnning them at 1X2ohm mono, then running at 2X 4ohm mono to see which is louder.
i'd also expect the bass to be tighter when running in 4ohm.

it's not like the subs are getting huge amount sof power, the splits should be keeping up when running off the deck.

is this the old BBQ style amps?
the trapezoidal shape one?

------------------
'96 Mirage, currently resembling a tin can
uninstalled: Rockford RFX9300, Focal 165W3's Vrx 2.150 & 1.500
Power by: HERTZ audison OPTIMA StingerAerpro
TEAM AUDISON

as already asked, what subs are they?

it may in fact be sweet to only run one 12" sub teamed with the splits off ch.1/2 on the RF.

good luck

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/////ALPINE audison DYNAUDIO »»»morel polkaudio OPTIMA Stinger LIGHTNINGAUDIO

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quote:

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is this the old BBQ style amps?

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Yep!

quote:

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as already asked, what subs are they?

---

I've been avoiding that: Kenwoods, but uncertain of model/specs, etc. I do know they're 4 ohm, but.....

quote:

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it may in fact be sweet to only run one 12" sub teamed with the splits off ch.1/2 on the RF.

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Not a bad idea! But if I can't even get him to ditch the 6x9's, how am I going to convince him to lose a sub??

Sorry for putting this in SQ, btw.

------------------

All electronic devices are powered by magical smoke.......
when the smoke is released, the device will no longer function

Soundstream.....Clarion.....Soundstream.....Stinger.....Orion.....but mostly Soundstream

[Edited 1 time by dasherhalo on 26 September 2002 at 22:58]

The BBQ amps are true hi current amps so 2 ohms wont be a problem at all. Id run the 2 subs off one bridged channel and splits off the other 2 channels. I like option 3 too although I wouldnt waste the money getting them melted down ;)
peace
Cyberpunky

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quote:

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Originally posted by dasherhalo:
Sorry for putting this in SQ, btw.

[/B]

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We are about optimising systems for best SQ here at any level, so this thread is welcome.


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Mazda SP20 - NOT yellow,Dynamat Extreme and G Spot in front doors
HU - Alpine CDA-7876RB
Audison VRx 2.150EX front stage amp
JL Audio 500/1 Class D monoblock sub amp
Front Stage - Morel HCW 6.5 woofers, Morel MT2 tweeters, Morel MX2.2 x-overs.
Rear fill - stockies with power from HU (not that they get any)
Sub - Kicker S12L72 in 75 litre 30Hz slot-ported display box.
Stinger cables and connectors etc
TEAM AUDISON SQ WITH ATTITUDE

Solution for th 6"x9"s:
Bridge them onto the amp, turn the gains up flat. He'll come back in a few days time with the 6"x9"s cooked. Problem solved

Seriously tho. Seeings as how the amps 1ohm stable I'd consider running the 2 subs off 2 bridged channels @ 2ohm mono. Run the front splits off the other 2 channels and drive the 6"x9"s off the HU.

Now comes the tricky part.. a speaker engineer friend of mine does this. The key factor is the person you do it for needs to be slightly clueless when it comes to audio.
To stop the subs & fronts distorting turn the gains down *der*. To stop the HU driven 6"x9"s doing it chuck a resistor on them to cut down the juice they get and increase resistance to lighten load on the HU's amp. So the powers cut down to a level the speaker can handle and the increased resistance makes the HU's amp more stable.

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WF Festiva: Clarion, Kenwood, Rockford Fosgate, StreetWires Small, Blue, Different
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quote:

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Originally posted by BlackIce:
drive the 6"x9"s off the HU.

chuck a resistor on them to cut down the juice they get and increase resistance to lighten load on the HU's amp. So the powers cut down to a level the speaker can handle and the increased resistance makes the HU's amp more stable.

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alternatively HP them with an inline cap. removing the subbass will greatly increase their power handling.

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/////ALPINE audison DYNAUDIO »»»morel polkaudio OPTIMA Stinger LIGHTNINGAUDIO

Issues of harassment, conflict, vindictive allegations, or unfairness, personal or observed, should be reported to me via Private Messages or at [email="shiny_car@caraudioaustralia.com"]shiny_car@caraudioaustralia.com[/email]

Thanks heaps for the opinions!!

I'm clueless about electronics: can anyone tell me what value caps I could use to HP the 6x9's??



------------------

All electronic devices are powered by magical smoke.......
when the smoke is released, the device will no longer function

Soundstream.....Clarion.....Soundstream.....Stinger.....Orion.....but mostly Soundstream

IMO ~220uF is a pretty universal cap for removing bass and some midbass.
X-over at 108Hz, on a 6db slope, will let some midbass though, but not enough to allow distortion, until high volumes.


------------------
'96 Mirage, currently resembling a tin can
uninstalled: Rockford RFX9300, Focal 165W3's Vrx 2.150 & 1.500
Power by: HERTZ audison OPTIMA StingerAerpro
TEAM AUDISON

hmmm. admittedly i don't sit down and calcuate the xover points from the raw specs of caps, but only go by the jaycar table:

jaycar data library : the .pdf on making your own speaker xover.

as such, a 200uF non-polarised cap (jaycar cat no. RY-6928 $8.95ea) provides a 6dB/oct 200Hz HP filter.

hope that's right.

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/////ALPINE audison DYNAUDIO »»»morel polkaudio OPTIMA Stinger LIGHTNINGAUDIO

Issues of harassment, conflict, vindictive allegations, or unfairness, personal or observed, should be reported to me via Private Messages or at [email="shiny_car@caraudioaustralia.com"]shiny_car@caraudioaustralia.com[/email]