2005 W203 Subwoofer

[Bemmy]

I've recently changed the head unit in my 2005 W203 (4 door) and want to fit a non-Bose original MB sub on the rear parcel shelf. There's plenty of used ones on eBay but I've a couple of questions
1) Will I need a separate amp? my head unit has RCA's for speakers and bass speaker
2) If I need a separate amp should I get 2 channel amp? - Looking at the MB sub it takes signal from both left and right channels
3) Can I just use signal from the rear door speakers if no amp needed?

I have an Erisin ES7718C-E24 head unit everything else is standard. I dont want loads of thumping bass, just want to beef the sound up a bit.

 

[John]

You will want to amplify a subwoofer as this will be the most demanding speaker application.

If you don't, the signal to the speakers will clip and the subwoofer will distort, sound awful and last a short time once the voice coil is burnt out.

With RCAs from your head unit, you will be able to run RCAs down the car front to back (I'd run two anyway as they are usually a pair even if you only use the green mono sub out on that head unit - if something happens to the one you are using, you have another ready to go!).

Make sure you run a remote control wire at the same time to connect to output "5".

You don't need a 2 channel amp because you are only driving 1 channel (1 sub) - so you could buy a mono. However, multiple channel amps will usually "bridge" so 2 channels combine to drive a single channel.

If you think you might want to run other speakers off the amp, I would buy a 5 channel amp. It won't cost a lot more and it gives you scope in future for connecting other speakers. If you really don't think you will, then stick with a 1 or 2 channel and save some cash.

I wouldn't use your existing MB sub as it will be shyte at best but by all means try it as you have nothing to lose and they are usually in a position to get more bass into the car. The problem with saloons is getting bass in the car can be tricky. You can replace your sub with an aftermarket but you may get lots of rattles that need deadening.

You could spend a bit of cash on a much better aftermarket subwoofer but it will need to be a reasonable power to hear it in the car. You can buy some highly effective but small 8" enclosed units these days from companies like JL Audio which I've heard myself and have been really surprised how much they've improved since I used to install upgraded car audio in the 90s and early 00s. They've come a long way.

You can tap into rear door speakers for a "high level" input into an amp (make sure the amp supports it) - I would assume the rear speakers receive a "full range" signal from the audio source but you want to be sure it is. Manufacturers on more modern cars have a tendency to mess around with the output to suit.

If you run RCAs from the head unit, you can at least be guaranteed a full range so you are not losing low frequencies being filtered by anything.

All of this depends on how much quality you want from the system and your budget.

If you just want a bit of extra bass, a 1 or 2 channel amp won't cost a fortune and you could certainly try the existing subwoofer to see...

 

[Bemmy]

Thanks for the reply John.
I'm not after audiophile quality and have no plans (at present, but i'll run all the cables through "just in case" ) to run any other speakers off of the amp so I think my best route is to use the OE Sub and get a 2:1 bridgeable amp.
If I use the mono out (Green [6]) I guess I need a RCA lead that goes from 1 connector to 2 to connect to the R & L inputs on the amp?
The OE sub has 2 connectors - ie 4 wires - going in to it - How do I connect the line outs to the sub? Do I need to joinn some of the sub wires together or not connect one side?
Sorry if the questions are a bit basic or nonsensical but I have no tech knowledge of this at all and just picking it up as I go along!

[Credit Wardsweb for the pic ]

 

[John]

We've all got to learn sometime - I picked up most of my knowledge learning myself as I went along and made plenty of mistakes albeit none too costly fortunately.

For the single RCA out, get a splitter so split a single RCA into two. Modern amps may be happy with a single RCA connecting to just one channel and some may have that labelled i.e. mono input (I think I have seen that before ages ago) but to be safe, I would use a splitter for £3!

If the subwoofer has 4 wires going into it, it's a Dual Voice Coil (DVC) subwoofer. So it might actually not be too bad although I will stand by my initial assessment!

At the end of the day, it's about minimising the dollar and maximising bang for buck for me... so if it sounds good to your ears and you are happy with it, that's a winner.

In terms of connecting, you would connect a mono speaker amp output +ve to one of the +ve connectors on the speaker. Then connect the first +ve in series to the second +ve.

Then connect the mono speaker amp output -ve to the -ve but the opposite way (so the first -ve it connects to is next to the 2nd +ve connection you made before and then the -ve connection next to the 1st +ve).

I'm not certain if you can connect them inline (so both red and black wires connect in series to the same respective connectors) but the way above is how I've seen it done before.

When you are putting that together, when you crimp the first spade-socket connector, crimp in one end of the next wire at the same time (so two wires in one spade-socket).

Although it's probably easier to cut the OEM wires to the sub and crimp ends on to those so that the plugs fit the sub perfectly.

Basically plan it out first before you do it so you know what goes where.

Always use a socket on the +ve end of connections if you can so you don't accidentally short anything e.g. if you are crimping on to the first +ve output on a wire from the amp, that wants a socket.

 

[Bemmy]

Thanks again John - don't go anywhere there may be more questions!!

 

[Bemmy]

I think I've understood what you have said - I've drawn up a basic diagram, hope I've translated it correctly. Please let me know if I haven't!
There will also be a fuse in the power line to the amp which I haven't put on the drawing

 

[John]

I think I've understood what you have said - I've drawn up a basic diagram, hope I've translated it correctly. Please let me know if I haven't!
There will also be a fuse in the power line to the amp which I haven't put on the drawing

Spot on!

Doesn't matter if the diagram isn't perfect... it's more a bit of planning ahead so you get it right first time (although it does help you identify things you might have forgotten about).

The worse-thing is starting something like this and you are missing something or you have to go back and take trim panels off / re-wire... not the end of the world but immensely irritating especially if you have to use your car and it's in bits!

I tend to think it out a few times and then crack on but I get the same results.

You want to keep grounds to as minimum-a-length as possible and ensure you both expose clean metal at the ground point you choose to make a good ground.

 

[Bemmy]

So today I've ordered a small 2:1 amp which should give me 180 watts when bridged to a single channel, wiring kit and OE shelf sub. All should be with me within a week.

Can I use some posi-tap connectors on the speaker wires? Whats the best way?

 

[John]

Sounds good.

I think the ultimate is soldering wires but life is too short I think.

I've always used bullet-connectors and spade-connectors and the respective opposites but just because I'm old school and I've always worked with them since the early 90s.

However, you need a decent crimper to work with them and they can be a little bit fiddly.

The posi-tap connectors look like they might be easier and requires no crimper.

As long as they make a sound connection and don't easily let the wire go, they should be fine.

 

[Bemmy]

OK, just waiting on the RCA splitter cable but everything else is here. I've used cable connectors temporarily on the sub just to make sure its ok, if it works I'll upgrade the sub and get the wires soldered properly.
Next issue is how to get the power cable through the firewall? I've seen a post saying there's a grommet above the battery but I can't see it. There is one between the fuse box and the brake servo, is this any good? It's the opposite side of the car to the battery though and I'd rather go down the passenger side.
Where to earth the amp in the boot?

 

[Bemmy]

I found a post on this forum that linked to a MBW**** forum thread about getting the power through the firewall but the pics hadn't been posted so I hope this may help anyone trying the same thing.
Under the glove box drop the cover (2 x T25 Torx screws) and up in the top left hand corner you'll see some cables running through a line of grommets [Pic 1] these go through to the engine space behind the battery [Pic 2] perfect you'll need to pull the grommet out, as it's capped, to get the cable through.

Just need to sort the earth in the boot now

 

[Bemmy]

Fitting the sub isn't straight forward. Headrests off, back seats out, C pillar trims out and a big lump of foam under the parcel shelf!
I marked out from underneath (in the boot) how much foam to cut out, mistake, use the sub as a template! The foam is a nightmare to cut!
There's a hole right next to the sub in just the right place for the sub wires.

 

[John]

You want the Earth wire to be as short as possible and to make as good-a-connection as possible.

When I fitted a subwoofer into a W211, I found a suitable ground in the rear somewhere.

I don't have pictures of my original install now but if you look at the following picture, there are a few brown wires all connected to a bolt.

That's an OEM ground so I used that!

 

[John]

Fitting the sub isn't straight forward. Headrests off, back seats out, C pillar trims out and a big lump of foam under the parcel shelf!
I marked out from underneath (in the boot) how much foam to cut out, mistake, use the sub as a template! The foam is a nightmare to cut!
There's a hole right next to the sub in just the right place for the sub wires.

I mounted mine subwoofer underneath the parcel shelf.

This is the location where I mounted mine but I did it differently and cut out some MDF "gaskets" - so sheets of MDF with a circular hole in the middle and then the subwoofer is mounted up to those and the top sheet was then bolted to the parcel shelf.

 

[Bemmy]

Thanks for the reply John, yes, there is an earth in a similar location in the W203.

 

[Bemmy]

I mounted mine subwoofer underneath the parcel shelf.

This is the location where I mounted mine but I did it differently and cut out some MDF "gaskets" - so sheets of MDF with a circular hole in the middle and then the subwoofer is mounted up to those and the top sheet was then bolted to the parcel shelf.

Did you get any issues with vibration? I've read some posts which suggested using MDF across the whole shelf to stiffen it up to stop this happening.

 

[John]

Did you get any issues with vibration? I've read some posts which suggested using MDF across the whole shelf to stiffen it up to stop this happening.

I think I did as I remember Dynamatting the whole underneath and certain parts of the shelf above.

I don't listen to music at crazy volumes so not a huge issue.

If you have the time and inclination, anything you can do to stop vibration means sound energy is not wasted by being converted into resonance!

Boot lid and rear quarter wings might need the same (inside).

The hard bit is you won't know what will resonate until it does...

But if you are adept at accessing the areas afterwards, you can sort out what rattles.

They are pretty-well screwed together so you might not get loads.

 

[Bemmy]

Getting the C pillar trim off was the trickiest bit but now I've done it once it should be easier if I have to do it again. (Cutting the foam was an a*** of a job as well! )
Is it worth putting an amp in-line control unit?

 

[John]

Getting the C pillar trim off was the trickiest bit but now I've done it once it should be easier if I have to do it again. (Cutting the foam was an a*** of a job as well! )
Is it worth putting an amp in-line control unit?

A lot of doing this kind of thing is an rse of a job. It's worth it when it is all done though.

Absolutely on the remote control unit.

Anything like that makes your life easier later on when it comes to setting the subwoofer how you want it to sound.

Otherwise you have to keep getting out, going to where the amp is, adjusting, going back etc.

My amp has just a volume remote that can either adjust all output volume or just sub - which is what I have.

You have the LPF adjustment on that too which is also useful.

I don't need this as I know what frequencies I want to cut off to various speakers so I set this on the amp.

 

[Bemmy]

My amp has just a volume remote that can either adjust all output volume or just sub - which is what I have.

You have the LPF adjustment on that too which is also useful.

I don't need this as I know what frequencies I want to cut off to various speakers so I set this on the amp.

I have a "REM" connector on the amp which goes to the blue "Remote" on the back of the head unit (blue wire)
What is "LPF"?
I've read the amp instructions about setting the "gain" but not really sure what it means - I'll plug it all in and see how it sounds!
Can I do any damage to anything??