Distortion and Intereference problems with new comps

[RaggedLob]

Recently decided to throw out the standard rear speakers of my 02 Ibiza MK4 as one had blown..

I picked up a a pair of FLI 17cm 220W components from Halfords (which i know to be generally good), and drilled out the crappy riveted speaker brackets, placing the speakers in MDF and bolting in (as many have done)...

When i installed them, i realised the standard H/U amp didn't have enough power to drive them properly, so they couldn't be heard, so i picked up a 2 channel Mutant amp..

My dad wired it up (an electrician, but not a car audio guy, which is why i am suspect of the wiring), and we tried again...

The speakers are definitely loud enough, but to be honest they seem far worse than the ones in the front, distorting almost completely when turned up to a decent volume, while the standard paper fronts play totally clear. I have put AntiVibe sound deadening on the panel behind, an theres foam insulation already in the cutout.
The cones also seem to jump like mental even at low volume, vibrating all the panels ( when in the shop they barely moved about, no matter what volume or bass)-

This is as well as horrid alternator interference, which i've been told can be cured by rigging some sort of capacitor to the power lead from the alt.

Anyone any ideas why it's so bad? these speakers were nearly £50, and as i'm not pumping massive db's, i thought they would be decent...

Cheers

 

[Slimy]

I reckon the input signal is too high, and it's just jumping from positive to negative. Are you using a high level or low level feed, and is it going into the right amp input? On average, a standard head unit will push out a high level signal from the speakers, and on average, most amps work off low level inputs. You need to convert it to get the signal levels to match.

Depending on whether you've run it for long you might have already fried your drivers, but fingers crossed.

The interference may also be caused by the mismatched connections, so get that matched up first.

 

[Slimy]

Just a second though, why didn't the standard h/u drive the units? I wonder whether you might have cooked an output stage on the head unit with the blown rear speaker? I've done that before, all you're left with is an extremely quiet output that is incredibly distorted.

 

[andycupra]

i was going to ask if you were using pre outs fromt he head unit, but if its oem then your not.

As above it sounds like you may have high level wires (the wires that were originally connected to the speaker) connected to the amp. Unless the amp is designed for high level input (most are not) then you need to get a 'high to low' converter. which will basically convert the high level wiring to a low level that you would get from pre outs. However i am not actually sure how thsi would effect the speakers / amp and sounds.

Also id like to know what the specs are for the speakers and amp?
From what you have described i was thinking its too much power driving the speaker, but its surely not that given speakers spec and that at low volume you can see them jumping.
do you have alink to the amp you have used? it would be good to know more about it. does it have a cross over / pass filter? check its not on bass/low.

ps post above this is also a possibility however the one standard speaker that was still working was ok i presume?

 

[RaggedLob]

Cheers for the replies, i am pretty sure my amp supports high level output, and i should've mentioned the interference is only generally caused when the engine is ignited, and is caused by the Alternator itself ( changing in pitch when it is revved). What's the best way to dampen this? I bought a cheapo capacitor from Halfords, but it seems a little bit weedy to do the job.

The speakers do the job, but i'm not getting anything like the performance/clarity and loudness i heard in the shop (possibly because their displayed in a sealed unit)

Here is the link to the Mutant amp: http://www.halfords.com/webapp/wcs/...uctId_264387_langId_-1_categoryId_165526#dtab
Link to the speakers (which are annoyingly half price just after i bought them!) :

http://www.halfords.com/webapp/wcs/..._productId_508417_langId_-1_categoryId_165707

Ta

 

[Slimy]

Amp specs;



* Number of channels: 2 Channel
* Frequency Response: 20-20000Hz
* Bass Boost: 0-+18dB
* Dimensions: 252zx172
* High Pass Filter / Crossover: 40-Hz-600Hz
* Load Impedance capability: 2 Ohm
* Low Pass Filter / Crossover: 40-Hz-600Hz
* Max Power: 2x95w
* RCA Input Terminals: 1
* RMS Power: 2x60w
* Speaker Input terminals: No


The bottom line says it all. You need a high level to low level convertor.

Edit: Tell a lie, the MT1202 manual says high and low level inputs...

 

[Slimy]

By the way, I don't know whether this might help, but from the manual;

We recommend mounting the amplifier to a piece of wood and then mounting the wood to the panel. Do not mount the amplifier directly to car metalwork as there may be a chance of creating a ground loop and introducing interference into the system.

Have you got any of the case touching your chassis? Even if it's mounted on carpet but screwed through to the chassis?

 

[RaggedLob]

Amp specs;



* Number of channels: 2 Channel
* Frequency Response: 20-20000Hz
* Bass Boost: 0-+18dB
* Dimensions: 252zx172
* High Pass Filter / Crossover: 40-Hz-600Hz
* Load Impedance capability: 2 Ohm
* Low Pass Filter / Crossover: 40-Hz-600Hz
* Max Power: 2x95w
* RCA Input Terminals: 1
* RMS Power: 2x60w
* Speaker Input terminals: No


The bottom line says it all. You need a high level to low level convertor.

Edit: Tell a lie, the MT1202 manual says high and low level inputs...

Yeah, that bit confused me, they obviously got it wrong, typical..( i work there part time btw )

I know their not the best speakers, but those specs surely point to performance that's better than the original paper ones? especially amped up...

 

[RaggedLob]

By the way, I don't know whether this might help, but from the manual;



Have you got any of the case touching your chassis? Even if it's mounted on carpet but screwed through to the chassis?

Ive bolted mine to the back of the rear seat in the boot, as far as i'm aware that isn't connected to much...

I've earthed the amp to a metal screw holding the C pillar in place, which is drilled into the painted side panels, anyone think this may be affecting it?

Forgive me, i'm pretty poor with wiring, engines are more my thing

 

[Slimy]

I know their not the best speakers, but those specs surely point to performance that's better than the original paper ones? especially amped up...

To be honest, I quite rate the standard speakers, they've come a long way over the last few years. I was thinking of putting some sort of bass box in my car (a Toledo boot is just asking for it!), but the standard speakers and head unit seem to be able to produce a fair bit of controlled bass. The only thing I need to fix is the dodgy wiring to the tweeter in my front door, it's crackling instead of singing...

The one bit I don't understand about your set up is why they didn't play ok straight from the head unit. I would have expected at least the same volume as stock speakers.

 

[mt audio]

Ive bolted mine to the back of the rear seat in the boot, as far as i'm aware that isn't connected to much...

I've earthed the amp to a metal screw holding the C pillar in place, which is drilled into the painted side panels, anyone think this may be affecting it?

Forgive me, i'm pretty poor with wiring, engines are more my thing

this will be causing your whine when engine started,bolt your amp to a peice of MDF then to the back of the seat.

Have you got the oem tweeters connected still? (cant remember if it has them as standard)

if so youll be throwing out the resistance meaning poor performance

 

[RaggedLob]

this will be causing your whine when engine started,bolt your amp to a peice of MDF then to the back of the seat.

Have you got the oem tweeters connected still? (cant remember if it has them as standard)

if so youll be throwing out the resistance meaning poor performance

Cheers, will try this, although i'm pretty sure the noise was there before the Amp was even mounted in place..

Have been told to put an interference surpressor on the power cable directly leaving the alternator, anyone else had to do this?

 

[andycupra]

amp stuck on back of rear seats is fine dont worry

 

[mt audio]

Cheers, will try this, although i'm pretty sure the noise was there before the Amp was even mounted in place..

Have been told to put an interference surpressor on the power cable directly leaving the alternator, anyone else had to do this?[/QUOTE]



the inteference suppresor isnt needed if you dont bolt your amp straight to the seat

 

[Slimy]

Have been told to put an interference surpressor on the power cable directly leaving the alternator, anyone else had to do this?

As far as I remember, interference supressors died out a few years back. Modern cars don't generate interference by default, it takes a faulty or badly routed connection to generate noise. In any case, it is fixing the symptom not the cause.

 

[dreemer]

how you doing mate upon reading your problem with a whizz noise when you rev i had this problem once i upgraded my live wire and earth wire and it cut it out completey hope that does it for you

 

[dreemer]

also try running the live cables one side and rca to the other keep them apart