New Amplifier

[Cletus]

Trying to improve the system in my Torana.

As part of my birthday 3 years ago, nopics arranged to have a system installed in my SL/R replica.

Pioneer headunit, some crappy 4inchers in the front, 6 1/2s on the rear shelf, and a sub. They used my old Alpine 4 channel amp 4x50 to drive the rears and the sub.

It sounded shit, and I needed the volume up to 30 (40 is max) to even hear it while going along at 110 kmh.

So I took it to Tonkins here in Adelaide, and splashed out on some Polk splits for the front and some soundproofing for the front doors. http://www.polkaudio.com/caraudio/mm/index.php?s=mm6501
They changed the setup so the amp drives the splits and the sub. Headunit drives the rears.

Pretty disappointed with the results, still feels like the sound is coming mostly from the rear shelf and the sub lacks punch.
So I'm thinking a new amp will fix the problem. The splits handle 125W continuous and the sub can take 200W, so a 4x100W amp is what I'm thinking about.

Is this overkill? http://www.alpine.com.au/showItem.php?item_id=75 Alpine 4x100 amp.
I'm attempting to get the system in my Torana to somewhere near the factory system in my Soarer, which I think is a superb system.

[Ben.]

factory soarer sound systems are arse anyway.

honestly, sounds like you should just smash up the 'gain' setting on the amplifier. that and play with head unit settings to fade it to the front. what you have now, should be able to sounds pretty decent, especially by comparison to a factory soarer system

[Fraud]

It sounds like when it was all initially installed, because you only had the 4 inch speakers up front and amped the rears, they might have put the gains down a fair way on the rears, and then may not have adjusted this when they amped the fronts

Assuming the sub runs on a separate (ie. non-fading) output, fade forward on the headunit to turn down the rears, then turn up the gains on the channels running the front speakers. (you may only need to do one of these things)

Are you happy with how the sub runs (guess it is hard to tell if the levels aren't right elsewhere)

Any reason for that amp in particular? Its been a while since I've played with this stuff, but the power specs seem odd

Per channel into 4 ohms (≤1%THD+N): 100W x 4
Per channel into 2 ohms (≤1%THD+N): 100W x 4
Bridged into 4 ohms (≤1%THD+N): 200W x 2

you should gain power at 2ohms, unless they have some circuitry in there to protect it or something... just seems odd... normally a 4X100wrms @ 4ohm amp would be more like 4X200wrms @ 2ohm, and then bridged into 4ohm would be 2X330ish (off the top of my head based on the old Jaycar 4X100 amp - which certainly didn't cost $600!)

[BMWTurbo]

Doubling the power will sound 3dB louder, which isn't much in reality.

A quiet soarer will always sounds leventy times better than a noisey Torana.

I 'suspect' this will be most of the problem as you need to overcome the ambient noise which will be in your bass/midbass regin depending on your exhaust. Do the highs and midrange sound 'okay'?

[Cplus]

Fraud - new alpines are "balanced" amps. New hotness tech, no gains at lower impedance.

Dont understand the attraction personally. Have always run subs at 2ohm or less personally.

[Fraud]

Fraud - new alpines are "balanced" amps. New hotness tech, no gains at lower impedance.

Dont understand the attraction personally. Have always run subs at 2ohm or less personally.

interesting... I wonder if this a: improves sound quality/makes sound quality more stable at any given impedance, or b: makes them cheaper to produce.

I'm gonna go with B.

Also BMWTurbo might be onto something... how noisy is the car otherwise?

[Cletus]

A quiet soarer will always sounds leventy times better than a noisey Torana.

I 'suspect' this will be most of the problem as you need to overcome the ambient noise which will be in your bass/midbass regin depending on your exhaust. Do the highs and midrange sound 'okay'?

Yes ambient noise is an issue (twin 2.5" exhaust, but 96dB legal), and I'm looking into soundproofing the car with Resomat in the next month or so.
It's not a new amp. I've had it since about '96, an MRV-F505. It was just sitting in my shed after I sold my last car, and I figured why not use it.

The problem is general volume. I'm just disappointed that the fronts don't seem to be putting out anywhere near as much as the rears do. If I fade the rears away, I need to wind the volume right up, which reduces the loudness bass boost and leaves the whole thing sounding 'tinny'. If I boost the bass, then when I reduce volume, it sounds crap. So I spend a lot of time mucking about with levels. If the fronts had more volume, I'd be much happier.

Despite what Ben thinks, I LOVE the factory system in the Soarer. I use a tape adapter for my Ipod and it sounds great. No distortion, the bass is always punchy and at 1/2 volume, is enough to cover all road noise at 110kph.

[Cletus]

It sounds like when it was all initially installed, because you only had the 4 inch speakers up front and amped the rears, they might have put the gains down a fair way on the rears, and then may not have adjusted this when they amped the fronts

Assuming the sub runs on a separate (ie. non-fading) output, fade forward on the headunit to turn down the rears, then turn up the gains on the channels running the front speakers. (you may only need to do one of these things)

Are you happy with how the sub runs (guess it is hard to tell if the levels aren't right elsewhere)

Any reason for that amp in particular? Its been a while since I've played with this stuff, but the power specs seem odd

Per channel into 4 ohms (≤1%THD+N): 100W x 4
Per channel into 2 ohms (≤1%THD+N): 100W x 4
Bridged into 4 ohms (≤1%THD+N): 200W x 2

you should gain power at 2ohms, unless they have some circuitry in there to protect it or something... just seems odd... normally a 4X100wrms @ 4ohm amp would be more like 4X200wrms @ 2ohm, and then bridged into 4ohm would be 2X330ish (off the top of my head based on the old Jaycar 4X100 amp - which certainly didn't cost $600!)

I've got Sunday arvo off, so was going to climb into the boot of the Torana and take a look at the setting on the amp. Thanks for the info.

[dodgyd]

Couldn't see stats on the Polk website but are the front speakers low efficiency compared to the parcel shelf speakers? Is it a good install or is there vibration / air gaps which are robbing power? Tweeters facing the front seats or facing your legs?

[Cletus]

Couldn't see stats on the Polk website but are the front speakers low efficiency compared to the parcel shelf speakers? Is it a good install or is there vibration / air gaps which are robbing power? Tweeters facing the front seats or facing your legs?

Tweeters are mounted in the top of the doors, facing me.

Got in the boot, removed the sub and took the cover off the amp.



Channel 1/2 (top) is the splits, and the gain was halfway
Channel 3/4 is the sub, and was on about 3/4.

So I maxed out both gains, and I reckon the splits sound much better at the front. Sub doesn't seem to improve as much.

Do I need to change any of the other settings while I have the amp exposed? (it's a pain in the arse and lower back to remove the sub)

[Fraud]

put both to ~3/4, you don't want to overrun the thing (I say this without knowing the voltage of the outputs on your head unit or the tolerance of the amp)

I'd play with the filters while you're there just for fun..

Assuming the fronts are set to highpass only, turn that down to ~80hz (looks like its set to ~150 at the moment)... this means the front speakers will play lower frequencies, closer to what the sub is playing, which should make them blend a bit better..

and assuming the sub channels are set to lowpass only, turn that down to ~80hz as well.. this stops the amp from wasting power amplifying frequencies that the sub can't really play anyway.

if that doesn't change it much then put it back...

if its some weird bandpass setup then i have no idea... model number of amp?

Its possible the sub wants more power, but its also possible that the relatively small sub in a relatively small sealed box in a largish, not-quiet car, with a boot that is fairly well sealed from the rest of the car may struggle to be noticed...

Also worth checking for obvious things - is the sub wired up correctly? ie. +ive to +ive, -ive to -ive? If not, fix it... If it is the right way around, experiment with reversing it, I've known people with largish cars to improve sound quality by reversing the polarity of the sub (I've never had this myself mind you)...

[Fondles]

Buy a decent sub and put it in an appropriate enclosure, that slimline deal aint even gunna kick your ass.

[Cletus]

The Amp is an Alpine MRV-F505, manual here http://narbi.free.fr/manuels/Amplis/Alpine/MRV-F505.pdf

From what I could see of the cabling, they aren't using the 4V preouts from the head unit. I'll try and get a photo of the cable side

[Fraud]

bump: was sorting through some of my old car audio junk the other day looking for some stuff, and was reminded of this thread..

How'd you go after fiddling with it? any improvement?

[Fraud]

bump: was sorting through some of my old car audio junk the other day looking for some stuff, and was reminded of this thread..

How'd you go after fiddling with it? any improvement?

[Cletus]

Sub is way better.
Increasing the gain on the splits has made it a bit better, but I'm hearing general hissing/static and some electrical noise. The noise is a popping sound at low revs, comes and goes.
I need to take the headunit out and check if the amp is connected to the 4V preouts or not.
Thanks for your help

[Cletus]

Sub is way better.
Increasing the gain on the splits has made it a bit better, but I'm hearing general hissing/static and some electrical noise. The noise is a popping sound at low revs, comes and goes.
I need to take the headunit out and check if the amp is connected to the 4V preouts or not.
Thanks for your help

[dlux]

That 505 amp will have more than enough power to do what you want.
I think your sub box is killing you system, get a decent sized box and it will make a world of difference and bolt it down.

[Cletus]

The sub is usually bolted in, it's just mounted right in front of the amp, so I need to remove it to get to the Amp.

After tweaking, I'm happy enough with the sub, it turns out the gain for it was orginally set to about 1/4, so it picked up pretty well.
Upping the gain for the splits has made it a bit better, but now I'm getting background hiss and some 'popping' noise into the system. Which frustrates me because I spent $200 at the auto elecs 3 years ago after it was originally installed trying to sort out engine noise. I haven't changed any wiring, I think just having the gain so low was hiding the noise.
Next I'm going to pull the headunit and check how it's wired up. I'm hoping they have messed up by running the sub/splits off the front channel output, instead of the 4V preout. I think that would help reduce the background hiss.

I put a new alternator in it last week. Got rid of the engine whine I originally had, just need to figure out the popping sound.

[Cletus]

The sub is usually bolted in, it's just mounted right in front of the amp, so I need to remove it to get to the Amp.

After tweaking, I'm happy enough with the sub, it turns out the gain for it was orginally set to about 1/4, so it picked up pretty well.
Upping the gain for the splits has made it a bit better, but now I'm getting background hiss and some 'popping' noise into the system. Which frustrates me because I spent $200 at the auto elecs 3 years ago after it was originally installed trying to sort out engine noise. I haven't changed any wiring, I think just having the gain so low was hiding the noise.
Next I'm going to pull the headunit and check how it's wired up. I'm hoping they have messed up by running the sub/splits off the front channel output, instead of the 4V preout. I think that would help reduce the background hiss.

I put a new alternator in it last week. Got rid of the engine whine I originally had, just need to figure out the popping sound.

[BMWTurbo]

Running higher gain will always increase the noise floor.

Only a high end HU will have a low noise floor, the reason being is even with a high end HU the signal to noise is 100dB + so by turning the amp gains up all you do is make this floor louder.

I might have missed it but what HU do you have?

Re hiss :- I run about 1/4 gain on my amps and I have a fairly high end head unit, custom made RCA leads, dedicated HU and amp feeds etc, the whole nine yards and I still have a very small amount of 'hiss' throughout quiet sections in material, there is no way around this without affecting the original recording unfortunately.

[Shonky]

That would be noise floor of course

To set your amps the best in terms of noise, turn the amp gains to minimum. Turn the head up to 80-90% of maximum. Then turn the amp gains up until you get it as loud as you want/need. The idea is that the head unit outputs as high a level as possible and therefore the ratio between the real signal and any other crap is the maximum.

[Shonky]

Double stupid.

[Cletus]

This thing is still beating me...

Took it into an audio place today, looking to try and fix the mild engine whine, and the electrical ticking noise.
Guy was good enough to suggest a number of fixes before bringing it back to him.

He thinks the ticking noise is definately ignition, probably leads.
Suggested that I buy a new suppression lead, and go through the plugs seeing if one of them is causing the sound.
Current leads are 12 years old, done about 20,000kms. 9mm 'race' leads. Ignition is Holden electronic (installed when I converted to straight LPG).
In the dark shed tonight, I started it up and could see very faint blue arcing from EVERY lead where it meets the plug, and an occasional one from somewhere on the dizzy.
Is this normal? Time for new leads?

Whining noise is probably earths. So new battery leads and terminals.

I've also noticed that the switch on the side of the amp that selects 4V preout isn't on. Turning it from 'Nom' to '4V' reduces the sound significantly, and pretty well cuts out the Bass.

I'm not sure how to get the head unit out though, in order to check how it's wired up.

[myliberty]

Lol. Not normal for electricity to escape. Your leads/boots are fucked.

[Cletus]

OK, will go and score a new set.
Even with all the slight sparking (it seems like its just around each plug, where the lead meets the top of the plug), it doesn't seem to affect the running of the engine at all.

[maddy]

This guy has some good advice

The Ten Commandments

I. The best cure is prevention. I cant overemphasize this point. If youve ever spent an entire weekend tearing an installation apart in order to eliminate some noise, you know what I mean. Take the time to sketch the system out before you begin the install. This graphic representation of the installation will help you to avoid introducing ground loops and will serve as a road map for eliminating noise if it is present.

II. Dont introduce ground loops. Ground loops are created whenever an audio ground is established at more than one location. Theoretically, the only place the audio ground should be connected to the chassis ground is at the source unit. In my experience, Ive found that in systems that have noise problems, a ground loop is the culprit nine times out of ten.

III. Never run signal wires alongside power cables. This is especially true in installations where high powered amplifiers are used. Large amplifiers are capable of drawing large currents. These currents vary with the musical demand of the program material as does the electromagnetic field surrounding the power cable. The more current that flows through the wire, the bigger this field becomes. If audio cables are located in close proximity to this fluctuating electromagnetic field, noise could be induced into the system.

IV. Always use 100% shielded audio cable. This will insure maximum protection against induced noises by power cables and other sources of electromagnetic interference. Good audio cables are not cheap. If you prefer to make your own cables, I would recommend using a wire with a foil shield surrounded by a drain wire.

V. Never use the ground wire in the vehicles OEM radio harness. This wire usually makes a very poor ground due to its length, small wire gauge, close proximity to other power wires, and unknown termination point. Instead, ground the source unit directly to the chassis or firewall.

VI. Make sure the amplifiers have a good audio ground reference. In order for the amps to function properly, the audio ground must be referenced to chassis ground at the source unit. If it is not, the amplifier could oscillate. To check for a good ground reference, take a volt-ohm meter (VOM) and measure the resistance between the chassis of the radio and the shield of the RCA line level outputs of the radio. This reading should indicate a direct short. If this is not the case, grounding the shield of the RCA line level outputs to the chassis of the radio will probably be necessary.

VII. Keep amplifier power ground wires as short as possible. The longer a wire, the more resistance it has. When a current flows through a resistance, a voltage drop is produced. Because of this, the ground reference at the amplifiers circuit board is no longer the same as that at the chassis of the vehicle. This ground potential differential can lead to noise and improper operation of the amp.

VIII. Dont connect all of your amplifier ground wires under one bolt. Contrary to belief, this is not required if the rest of the system is installed properly. If you do connect more than one power ground wire under a single bolt, you run the risk of amplifier ground modulation. This is caused by the current demands of, for example a woofer amp, modulating the power ground wire of a tweeter amp. This results in a squeaking noise that can be heard over the tweeters whenever bass notes hit.

IX. Make sure all levels are set correctly. Level setting is a critical part of the installation process. If done properly, maximum system signal to noise ratio can be obtained. Keep in mind that you want to drive the audio cables that feed the amps in the rear of the car as hard as possible. To do this, reduce the gain of the amplifiers to minimum. Turn up the volume on the source unit to 80% of maximum. Now adjust the input sensitivity of the amplifiers upward until the maximum intended loudness is obtained.

X. Noise filters can only reduce noise, not eliminate it. A noise filter is just that, a filter. And like any other filter (crossover network, etc.), it works by modification, not elimination. Some installers rely on filters heavily. In some instances a filter may prove necessary, but I believe that if the system is installed properly, a filter is usually not required.



Btw good buy on the polks - they love to be cranked.