Amp/Speaker

Hi All

So I've connected an amp to the car. The power, ground and remote wire is all fine.

But to give it a test run I connected a speaker to the left of the amp and nothing is being played apart from a screeching noise?

Is this because I haven't disconnected the speakers in the car that the amp is not recognising it? I did this because I wanted to see everything is working fine before I start splicing or bringing new wires through the front doors…..

Or could be the two phonos (rca) not sending the correct signal?

Help! Thanks

Assuming you have a source going in to the amp…
There shouldn't be an issue with connecting the amp alongside the existing speakers. Is the source going to your amp a low-level input? Wondering if your putting a high-level input into it and it's just massively distorting.
How does the phone come in to the equation?

paceman said

Assuming you have a source going in to the amp…
There shouldn't be an issue with connecting the amp alongside the existing speakers. Is the source going to your amp a low-level input? Wondering if your putting a high-level input into it and it's just massively distorting.
How does the phone come in to the equation?

Hey sorry it should have said RCA cable. I'm assuming that's the input signal from the radio?

Apologies the picture is upside down but the two RCS are connected in the correct position?

What are the other phono sockets?
Nothing wrong with connecting an amp and speakers, as well as direct speakers (not a lot of point mind, but it would still work).

paceman said

What are the other phono sockets?
Nothing wrong with connecting an amp and speakers, as well as direct speakers (not a lot of point mind, but it would still work).

No I'm not planning to have a direct speaker. It was a test run to see everything works before I wire the amp to the front two speakers.

The other rca on the head unit says sub, fronts, and rears…

If you disconnect the RCA's, but leave the amp powered on, touch the centre pin with your finger and you should get a noticeable hum.

paceman said

If you disconnect the RCA's, but leave the amp powered on, touch the centre pin with your finger and you should get a noticeable hum.

Thanks

But when you mean touch the centre pin? Which bit is that?

The centre prong of the rca plug. The outer is ground centre is +ve. Touching the centre pin wont cause you any damage!
It is worth confirming if the rca outputs you are using are actually outputs. You could try connecting the amp to the front rca output as another test.
How many speaker outputs does your amp have? How many rca inputs does it have? How many speakers are you trying to run with the amp?

paceman said

The centre prong of the rca plug. The outer is ground centre is +ve. Touching the centre pin wont cause you any damage!
It is worth confirming if the rca outputs you are using are actually outputs. You could try connecting the amp to the front rca output as another test.
How many speaker outputs does your amp have? How many rca inputs does it have? How many speakers are you trying to run with the amp?

Ah ok thanks that makes sense. I'll give it a go tom.

The amp is a two channel.
It has 2 RCA inputs.
Just two speakers he front left and right.

In that case probably worth try the rca output marked front.

paceman said

In that case probably worth try the rca output marked front.

Yep, "front" would usually be your main line-level output.

Could the ones you have connected be sp/dif (digital)? That might explain the strange sound.

RCA jacks are on the left of the photo above and have a single inner pin.  red for right and white for left IIRC, the ones that you are using are DIFF IIRC…not RCA per say.

I connected them to the front outputs and it's working!

Eventually if I connect a sub would the RCA be ok left at front output?

Excellent!
What would you connect the sub to? A different amp? And take the feed from the sub channel of your head unit? Or does your amp have a dedicated sub output alongside the left and right channels?

paceman said

Excellent!
What would you connect the sub to? A different amp? And take the feed from the sub channel of your head unit? Or does your amp have a dedicated sub output alongside the left and right channels?

Thanks for the help mate.

Admittedly the speakers are alot clearer, but I still have to have the volume on the headunit between 55 (max is 62) for the music to be loud although it is much clearer! I would have thought the amp would have allowed me to have the volume at 40 and it would be relatively loud. The head unit is Pioneer deh80pfrs.

Due this I was considering perhaps I need a bit of a sub.

I have a Kenwood kac726




I have connected the front to speakers to the above left and right.
Could I also connect the rears to these channels?

On the other side of the amp I can see another left and right channel



Slightly confused, may have to read up on my options.

Option 1 connect the rears too if I'm able to with this amp
Option 2 connect a sub if I can?

Thanks

optimusdub said

I still have to have the volume on the headunit between 55 (max is 62) for the music to be loud…

Have you tried adjusting the input sensitivity?

optimusdub said

I have connected the front to speakers to the above left and right.
Could I also connect the rears to these channels?

If you connect them in parallel you will reduce  the resistance. If you connect them in series you will increase the resistance. I would check the rating of the amp and speakers before you attempt it.

optimusdub said

On the other side of the amp I can see another left and right channel

These are "speaker level" inputs. They are for if you are connecting to the head unit from the "speaker out" instead of the "line out" phono/rca connectors.

Following on to what Whip said (all correct), I found a manual - http://manual.kenwood.com/files/B64-1213-00.pdf
I'd definitely try adjusting the input sensitivity.
If you connect rears and fronts to same output, you will need to do them in series, which makes your wiring tricky as you are basically coming out of one speaker and on to the next, so you will only have 2 wires connected to your amp. This will give you a 8 ohm impedance, bit higher than the amp is rated for (so it won't be as loud) but if you did them in parallel you'd be 2 ohm which isn't recommended based on the specs.
If you want to connect a sub, then that's covered on page 8 (tri-wiring) and you'd need to make up your own cross-over (in the manual).

With your current setup I would wire the amp in tri-mode (front and sub) and leave the rears unplugged, or wired to the head unit.

dont run both front and rears from this amp.

I'm intrigued what the original connector that you had the amp wired to was?

IMO rear speakers arent needed anyway unless you are watching movies with surround sound!

so to recap

phonos connected from FRONT on head unit to amp
front speakers wired to the left and right as normal
SUB wired across the terminals marked Bridged.

in order to do this you will need to make/buy a PASSIVE crossover for the SUB (a coil) and possibly add some capacitors in line with the front speakers.

this cuts off the high frequencies from going to the subwoofer (making it sound poo) and stops the lowest frequencies from going to the fronts. essentially you want the amp to "see" just the right speakers at the right frequencies. this stops the apparent impedance (a bit like resistance) the amp is pushing against changing drastically throughout the range of frequencies.

finally the values for the crossovers are dependant on the impedance of your sub.

your front speakers will be 4ohm (normal for a car)
but the sub could be 2ohm, 4ohm, or 8ohm

please check your sub as the manual says not to bridge a sub with lower than 4 ohm impedance.