JonW

Currently looking at amping my ICE - the Infinity 6.02CS just sap the power from my Sony headunit so badly.... ;-(

So whats Ive currently got is the 6.02CS up front and the std Subaru rears disconected. was thinking of buying some better (but not stunning rears - Makro had some 6x9 JVCs at about £35 quid that have to be streats better than the std crap...)

So with this in mind I thought I need a 4 channel amp to amp that lot with decent cabling and make it audible at speed.

Current favorites seem to be Alpine (its a brand I trust to be quality) and ive seen the MRV-F307, the F407 and the F357 (specs ripped from Edworthys site appear below).

From what I can tell the 357 is the 307 with an extra Sub output and the 407 is a more powerful version of the 307

- So... do I want the 5th channel for a sub?
- Is the output too weedy in a jack of all trades amp anyway for a sub?
- Would I be better spending my money on a 407 instead?

Also....
The prices for these amps from the ad for Mobile world (in Hounslow and Tottenham Ct rd) from this months In-Cars mag is a bargain 168.99 for the 307, 218.99 for the 407 and 229.99 for the 357... Anyone dealth with these people and wish to comment?

Jon.

------------------ SPECS --------------------------
Alpine MRV-F307 amplifier(Reference #MRV-F307)
MOSFET power supply. DC-DC PWM power supply. Auto temperature protection. Built in crossover. Speaker level inputs. Gold plated power terminals. Gold plated speaker terminals. Max Power 90W x 4 (4 Ohm stereo). 240W x 2 (Bridged 4 Ohm). RMS continuos power (Watt)(at 12.0V, 20-20kHz). 4 Ohm stereo (0.04% THD) 30W x 4. 2 Ohm stereo (0.03% THD) 40W x 4. Bridged 4 Ohm (0.3% THD) 80W x 2. RMS continuos power (Watt)(at 14.4V, 20-20kHz). 4 Ohm stereo (0.04%THD) 50W x 4. 2 Ohm stereo (0.03% THD) 60W x 4. Bridged 4 Ohm (0.3% THD) 120W x 2. S/N ratio 100dBA. Frequency Response (=0, -1dB) 10-50kHz. Bass engine ready.
Price: £243.99

Alpine MRV-F357 amplifier(Reference #MRV-F357)
MOSFET power supply. DC-DC PWM power supply. Auto temperature protection. Built in crossover. 5 Channel bass EQ circuit. 5 channel subsonic filter. Gold plated power terminals. Gold plated speaker terminals. Max power 90W x 4 + 300W (4 Ohm stereo). 240W x 2 + 300W (Bridged 4Ohm). RMS continuos power (Watt)(at 12.0V, 20-20kHz). 4 Ohm stereo (0.04% THD) 30W x 4 + 100W. 2 Ohm stereo (0.3% THD) 40W x 4. Bridged 4 Ohm (0.3% THD) 80W x 2 + 100W. RMS continuos power (Watt)(at 14.4V, 20-20kHz/*20-200Hz,0.3%THD). 4 Ohm stereo (0.04% THD) 50W x 4 + 150W. 2 Ohm stereo (0.3% THD) 60W x 4. Bridged 4 Ohm (0.3% THD) 120W x 2 + 150W. S/N ratio 100dBA. Frequecy response (+0,-1dB) 10-50kHz. Bass Engine Ready.
Price: £282.99


Alpine MRV-F407 amplifier(Reference #MRV-F407)
RMS continuos power (watt) at 12.0V, 20-20kHz, 4 Ohm stereo (0.04% THD) 40W x 4, 2 Ohm stereo (0.3% THD) 50W x 4, Bridged 4 Ohm (0.3% THD) 100W x 2. RMS continuos power (Watt) at 14.4V, 20-20kHz, 4 Ohm stereo (0.04% THD) 60W x 4, 2 Ohm stereo (0.3% THD) 80W x 4, Bridged 4 Ohm (0.3% THD) 160W x 2, S/N ratio 105 dBA. Frequency response (0,-1dB) 10-50kHz. MOSFET power supply. DC-DC PVM power supply. MOSFET final outputs. Top panel multi status indicator. Bulit in crossover. Subsonic filter. Top panel adjustment. Dual soded terminal layout. Gold plated power terminals. Gold plated speaker terminals.
Price: £350.99

john banks

The five channel idea is nice, but 100WRMS just isn't enough to drive a sub, esp. if it is in a sealed box. Better outputs can be had by bridging two channels. So unless you find a 6 channel amp you are a bit stuck for amping the rear speakers too. Also, to get over 100WRMS per channel at 12V and decent THD costs a lot of dough. So I bridge the fronts as well, which is a value way of getting big power. Now your posher components will prob. take more power than mine, which sound substantially better from 2 channels bridged for each side - although they probably reach the limit of cone excursion before they would distort from amp clipping. The extra power (rated 150WRMS) may seem excessive for 90WRMS speakers, but they have a 270W peak, which may explain the extra authority of the loud bits - you smile rather than turn it down! Barry heard the difference with it bridged in my car and agreed it sounded much better. So you end up needing eight channels! Or six if you run the back ones off a headunit. Seriously, I put some £100RRP Kenwood speakers in the back, and have gone back to factory and can't tell the difference. I wouldn't even bother spending £35 on 6x9, cos then you'll think - I've got these speakers that can handle all this power and you will "waste" amplifier channels on them. Save it all for good speakers. If you are using a sealed sub, you could of course go for a separate dedicated sub amp - Class D, digital and monoblock are all phrases banded around with enthusiasm by those in the know. I don't need it as my bandpass box hits 129dB off only 100W, but if you want big bass from sealed boxes you need a lot of power, and ideally DVC subs or multiple subs to get the impedance low and extract all the juice from those nice American amps we all rave about. In Barry's recent thread I put a few caraudiodirect links to some nice looking amps for under £400. What about the Dragster 6 channel? The Lightning Audio amps have also had good reviews (they are a branch of RF) - I have a bottom of the range 2 channel one and it is really quite nice. Or you could go the whole moo and get RF or PG - but even then, it is the low impedance figures which get really exciting!

JonW

Hi John, thanks for the info...

I agree the 5 channel amp doesnt seem very useful once you start to realise how little power its got. Think I will get the 4 channel amp and then bridge em to get maximum power up front.

So if my rear speakers dont do much, and I have them disconected at the mo, why cant I replace these with two sub units, using the boot as a unsealed-ish box? this would mean the luggage space wouldnt be compromised...

Jon

JonW

Just seen the acoustic box for the side boot fitting in another thread... yum.

Since I am considering buying an Empeg/Rio unit which has no internal amp how would I wire a sub?

Head unit (or unamped Rio) will have outputs that connect to the inputs of the amp. The amp has 4 channels out to speakers... I cant see where would I wire in my sub?

Sorry for the numpty questions...

Jon.

[This message has been edited by JonW (edited 07 August 2001).]

john banks

I would go for the box every time. What you are describing is a "free air" sub with particularly stiff suspension. You would encounter extreme vibration problems in the rear shelf and would have to be meticulous in sealing the front of the driver from the back to stop leaks. And it wouldn't give you the same SPL as a sealed or ported box. Try a

JonW

John,

Again thanks for the great info. I did as you said and decided a free air sub is not for me. I decided to go for a box (will get the 'stealth' built in unit for the Scoob on the sub positioning thread)
I nipped (its 70+ miles from me but I was coming back home from a biz trip...!) down the shop lastnite and bought the MRV-F407 amp and an infiinty 120.1SE sub... am ordering the box today.

The manual contains all the wiring guides as you say and I was pleasantly suprised not to be using bits of wire to bridge the connectors but instead just switches - very smart. (but Id agrue an amp that retails at 350quid in some places should be at least a bit clever... ;-)

Just got to get my tame installer to cable that lot in with good quality cable and im away...

Cheers again, Jon.

john banks

It is usual not to have to do anything to bridge an output - certainly no bits of wire required usually. On all three of my amps you just connect the -ve of the speaker cable to the right half of the bridge rather than the left half. Leaves two of the four terminals of a pair unconnected. Only switches are usually to double up a single input - say if you are bridging full range speakers and want your lefts on the lefts and rights on the rights rather than some crazy reverse phased summation! For a sub, usually just connect a stereo phono lead and then wire in the speaker cable. Its one of those things that is very easy ONCE YOU HAVE DONE IT! Check and double check all the connections before powering up, and start at minimum gain/minimum headunit volume.