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by **wonderloaf** » Sun 17 Oct, 2010 13:34

Silly question I know, but I've recently bypassed (ie removed) the original BMW speaker amp from the footwell spaeker, and installed new speakers and head unit. Out of curiosity I reconnected the original BMW Business Unit head unit (still without the speaker amp though) and to my surprise it all sounds fine. To my ears it's actually better than the new head unit so I'm keeping it for the moment.

My question is though what does the BMW speaker amp do, as it all sounds fine without it? Also can I damage anything by not using the amp? :?:

Website · by **astropa** » Thu 07 Apr, 2011 17:08

What method did you use to access the Front speakers? Which pieces of the interior have to be removed to gain access to the speakers in the foot wells?

by **wonderloaf** » Thu 07 Apr, 2011 18:53

I followed the BSW directions, page 5 onwards:

http://www.bavariansoundwerks.com/produ ... adster.pdf

Although it's for a left hand drive car the steps are the same, you've just got think in mirror image!

Also found it easier to pull up the sill covers before taking off the kick-panel, but it does take quite a bit of force to do so.

Website · by **astropa** » Thu 07 Apr, 2011 20:24

Great link mate. D

It was much easier to access the foot well speakers than i tought. I've removed mine this evening. :

by **wonderloaf** » Thu 07 Apr, 2011 20:59

Glad it all worked OK, mine were a right pain the first time, but now takes a couple of minutes to get the speakers out.

by **chris1984_99_99** » Fri 08 Apr, 2011 08:12

When I first got my car the amp in the passenger footwell wasnt working. Infact I didnt know there was one! I changed the head unit and got 2 new speakers behind the seats and the sound was still terrible! clipping and popping as soon as i turned it up to a volume level where i could actually hear it.

Took the car to a car to halfords to get speakers for the footwells and the guy there told me theres an amp and it isnt wired in right. So off i went to a mate and got it up and running.

....I havnt touched the setup since. It sounds fantastic. Plenty of bottom end bass, even with the roof down.

by **theduck** » Fri 08 Apr, 2011 08:33

the footwell amp is what is known as a 'power amp' and it in simple terms, is the muscle.

The volume control on the headunit adjusts a low level (normally line level) signal which it sends to the poweramp, which then increases it by a fixed rate upto 'speaker level' so that is the correct level to drive the speakers.

HTH

by **siwilson** » Fri 08 Apr, 2011 09:02

The BMW head unit is a standard low power head unit with speaker outputs that drive the rear speakers and door tweeters directly. I imagine BMW thought the foot-well speakers would need more power, so they added the speaker amp as a booster. The speaker amp takes the front speaker outputs from the head-unit, boosts them and sends to the mid-bass foot-well speakers.

Since this speaker amp takes speaker input as opposed to line level (RCAs) is it important to bypass it when adding an aftermarket head-unit since most aftermarket head units are high power (25W to 50W per channel).

by **wonderloaf** » Fri 08 Apr, 2011 11:18

In my zed I've got a Kenwood KDC-w7044u head unit with just about every sound customization going, with Fusion components at the front and Kenwoods in the rear. Initially I bypassed the footwell amp and played around with the sound settings, but just couldn't get it right, the sound didn't seem to have any 'oomph'.

I then reconnected the footwell amp and now have the oomph that I'm after, only problem is if I turn it up too loud I get a bit of distortion.

I notice I have some RCA connectors (lower level?) for connecting to Front outputs a seperate amp, would I better off using these to connect to the footwell amp, but keep the existing speaker connections for the rears?

As you can tell I'm a bit of a :dunce:

at ICE!

by **siwilson** » Fri 08 Apr, 2011 12:45

wonderloaf wrote:In my zed I've got a Kenwood KDC-w7044u head unit with just about every sound customization going, with Fusion components at the front and Kenwoods in the rear. Initially I bypassed the footwell amp and played around with the sound settings, but just couldn't get it right, the sound didn't seem to have any 'oomph'.

I then reconnected the footwell amp and now have the oomph that I'm after, only problem is if I turn it up too loud I get a bit of distortion.

I notice I have some RCA connectors (lower level?) for connecting to Front outputs a separate amp, would I better off using these to connect to the foot-well amp, but keep the existing speaker connections for the rears?

As you can tell I'm a bit of a at ICE!

I am surprised the footwell gave you more ooomph. What is the output power of your head unit?

I suspect the distortion you heard was over driving the foot-well amp. Its not that great really.

If you want more then a separate amp is needed. don;t try to drive the foot-well amp with RCAs it's not worth it.

by **wonderloaf** » Fri 08 Apr, 2011 19:23

Power of my HU is 50W per channel max, 30W DIN 4534 (RMS?).

Just been out and removed and bypassed the amp again to give it another go, maybe I had the HU set up wrongly previously as it was new and I was unfamiliar with it.

by **siwilson** » Sat 09 Apr, 2011 06:37

wonderloaf wrote:Power of my HU is 50W per channel max, 30W DIN 4534 (RMS?).

Just been out and removed and bypassed the amp again to give it another go, maybe I had the HU set up wrongly previously as it was new and I was unfamiliar with it.

That 50w per channel will overdrive it. The BMW unit is much less.

What you might be experiencing with poorer sound comes from the door tweeters now being driven way too hard compared to the mid-bass in the foot-well. In the standard setup the foot-well mid-bass units get boosted by that little amp, but the tweeters do not. The tweeters run directly from the head unit and no doubt BMW took this into account when balancing the system. When you bypass the foot-well amp and use a high power head unit you are now 'boosting' both mid-bass and tweeters. As a result the tweeters are getting much more power and this is affecting the balance. You may also be over-driving the original door tweeters, but less likely.

What you do next depends on your appetite for removing the door cards and replacing the tweeters.

by **wonderloaf** » Sat 09 Apr, 2011 07:24

Sorry should have explained myself better, have also replaced the tweeters in the doors with those that came with the component speaker set. Only thing is that I didn't use the crossovers that came with the set as I couldn't see an (easy) way of wiring through the door hinge. Will this make a big difference?
I've got Fusion components and I read somewhere that the tweeters have built in crossovers, don't know if that's true or even possible.

BTW thanks for answering these posts, these are things that have been on my mind but never got around to asking!

by **siwilson** » Sat 09 Apr, 2011 07:36

wonderloaf wrote:Sorry should have explained myself better, have also replaced the tweeters in the doors with those that came with the component speaker set. Only thing is that I didn't use the crossovers that came with the set as I couldn't see an (easy) way of wiring through the door hinge. Will this make a big difference?
I've got Fusion components and I read somewhere that the tweeters have built in crossovers, don't know if that's true or even possible.

BTW thanks for answering these posts, these are things that have been on my mind but never got around to asking!

When you replaced the tweeters, did you remove the capacitor as well or leave it in place? It was in the door, quite close to the tweeter.

It would be a good idea to install the crossovers as the new speakers were designed to use them. A way you can install these is to connect the crossovers into the wires that come from the head unit where you bypassed the foot-well amp. You can hide them above the panel under the glove box. These wires from the head unit also go to the door tweeters, so connect them to the tweeter output. Then run new wires from the crossovers to the head-unit and connect to the front speaker output. You can patch into the head unit at the ISO to BMW adapter. Also run new wires to the mid-bass in the foot-wells.

by **wonderloaf** » Sat 09 Apr, 2011 08:27

Just did a like-for-like swap with old tweeters so guess the capacitors are still there.

When I installed the hew HU and speakers it was mid-winter and I have to work on drive so wanted to get things done ASAP, but now the weathers warmer and drier will take a look at rewiring things properly.

Thanks for all your advice, much appreciated

by **XVar** » Tue 26 Apr, 2011 12:22

The capacitor is just before the actual tweeter, after the yellow plug. If you disconnected the plug and took out the whole lot, then the capacitor won't be there any more. I recently did a full replacement of the front speakers, take a look at my thread for pics etc: http://www.zroadster.net/forum/viewtopic.php?t=30471

by **theduck** » Sun 01 May, 2011 11:55

This thread is full of technical nonsense. 'Oer driving' a speaker WILL NOT cause poor sound quality. Poor sound quality is caused by an amplifier 'clipping' the signal as it is under powered for the amplification levels being requested of it.

Also, ignore wattage figures, they are useless for the most part.

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So exactly what does the speaker amp do?

So exactly what does the speaker amp do?

Removing front speakers

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