X3 (E83) > How To (E83)

Installing MTX Audio replacement speakers


Recently I acquired an X3 3.0i SE 2004, with the standard "HiFi" audio option. It is a really nice car, however... the sound was quite frankly terrible. The previous owner had had installed an Alpine head unit to get iPod connectivity, but nevertheless the end result was clearly duff. I spoke to a few car audio installers about possible solutions, but did not get very satisfactory or affordable proposals. A bit of web research indicated that the MTX TX6.BMW replacement speaker package could be an option: http://www.mtxaudio.eu/products/caraudio/spk/item/tx6bmw - these are available for around £300 if you shop around. As a bit of a hi-fi buff, I thought I'd give it a go, and here is what I had to do.

Let me say these are strictly my experiences on this model car, and "your mileage may vary"...

Tools I needed:
- Car trim panel removal pry tool
- Phillips 1 & 2 screwdriver
- Torx driver set (i.e. ideally not just Torx bits)
- 8mm nut spinner (or 8mm spanner)
- 16mm 1/2" drive socket, extender bar, handle
- Magnet
- Torch
- Craft knife
- Soldering iron
- Portable vacuum cleaner
- Electric drill
- 2mm, 3mm, 8mm, & 10mm HSS drill bits
- Wire side cutters
- Crimp tool
- M5 x 0.8 tap (MacAlister basic tap & die set from B&Q is good)
- 4.2mm or 4.5mm HST drill bit for the above
- Tap & die lubricant (cutting oil)
- Bench vice

Additional parts I needed:
- Insulated crimp terminals, male & female, two colours (e.g. Lucar type from Maplin) - either spade or bullet is fine, ensure female is fully insulated
- 5.3mm uninsulated eyelet terminals (Maplin JH62S)
- Small cable tie base (Maplin SJ14Q)
- Small nylon cable tie (Maplin RY07H)
- Stranded insulated equipment wire 3A, two colours

Initial background information:
- To understand how to access the front in-door speakers, watch: https://www.youtube.com/watch?v=Cnz3djxwN50
- To understand how to access the front under-seat speakers, watch: https://www.youtube.com/watch?v=Ger6JTr4k7w
- Optional: To understand how the front door mirror and interior trim works, watch: https://www.youtube.com/watch?v=FllO9wkfpvw
- Read the "Owners Manual" link on the MTX web page shown above
- Wiring harness information: https://ampire.zendesk.com/hc/de/article_attachments/200109742/X3__E83__2005-_DEI.pdf
- As a general principle on this model, -ve wire polarity is indicated with a brown stripe
- Don't proceed with this project unless you are comfortable with the above and all steps below!

The work can be naturally broken into two phases, which can be done on different days, and this is likely to be easier than attempting to do the lot on one day.

Phase 1 part 1 - Under-seat woofer, passenger side:
My recommendation is to do the work with the woofers first, as the tasks are a bit simpler, and the car will be ready to go immediately afterwards.
- See video #2 above for background
- Open the tailgate and disconnect the positive terminal of the battery, position the connector safely distant from the battery
- Do not close the tailgate as it is a bit tricky to unlock if power is missing; it requires fiddling around inside the lock (see https://www.youtube.com/watch?v=bRlUNvWqkaE)
- Starting with the passenger side, undo the four bolts retaining the seat; you may need to pop off some conical plastic bolt covers with a small screwdriver
- My car had 16mm hex bolts, some models have Torx bolts apparently
- Release the under-seat electrical connector as shown in video #2 above
- Push the front seat back into the rear passenger compartment; it is not necessary to remove the seat from the car as it remains attached to the seat belt harness
- Vacuum the now-exposed under-seat area
- Locate the four Phillips #1 countersunk screws retaining the plastic woofer cover, and if they are corroded use a craft knife to clean the X slot first
- Unscrew the retaining screws and remove the plastic cover; it is quite likely to be somewhat soiled so cleaning it is a good idea
- There is a gauze mesh on the rear of the plastic cover; I chose to peel mine off as I think it is of no value and will muffle the sound
- At this point we can see the four Torx screw heads which retain the woofer in place
- However, this is where I found my first big surprise, which is that on my car a 50mm wide steel member passes over one of the screw heads, rendering it inaccessible
- My solution was to drill out a 10mm hole in the member (after a 3mm pilot hole) to allow access to the concealed Torx head; if there are better options let us know!
- Be careful not to allow the drill to contact the Torx screw head when it clears the hole, if you mangle the screw head you are stuffed
- Possibly if you can find an L-shaped Torx driver it might be possible to avoid the drilling; it would be pretty fiddly though
- The old woofer cam now be gently levered out and the source drive connector unplugged
- You may need to use a craft knife to slice through some felt/carpet and suchlike in the area to free the unit
- Using a magnet, pick up any swarf (iron filings) arising from the drilling and vacuum the area again
- Cut off the old BMW woofer electrical source connector, and strip the wire endings
- As it is very awkward to attempt to connect these wires directly to the new woofers, proceed as follows
- Crimp on two colour-coded insulated female connectors to the wires
- Prepare two short extension wires, each 70mm in length, with appropriate +/- colour coding
- At one end solder on a 5.4mm uninsulated eyelet
- At the other end crimp on a male crimp connector
- Unscrew each woofer electrical input retaining screw with retaining lug, and thread it through the eyelet connector and screw on again
- The new woofer can now be inserted into position and the connectors joined with appropriate polarity
- Arrange the wires in a tidy fashion, and fasten down with new woofer using the retained Torx screws
- Fasten down the woofer cover using the retained Phillips #1 screws
- Move the passenger seat back into place, and reconnect the under-seat electrical connector
- Reinstall the seat bolts, with a similar firm torque to that required to release them
- Reinstate the seat bolt covers, just push them on firmly

Phase 1 part 2 - Under-seat woofer, driver side:
- Adjust the steering column to be as high and as deep in as possible
- Perform the steps in Phase 1 part 1 correspondingly for the driver's side
- Reconnect the battery
- Restore the steering column and seats' positions
- Play some bassy music through the audio system, and by placing a hand on each woofer cover verify that each woofer is working
- The car is now in principle fully operational as usual

Phase 2 Overview:
Review YouTube video #1 above.

The steps below differ in one significant respect from that in the video: my recommendation is that the battery should be disconnected, and then the airbag can be unplugged and left mounted on the interior door panel as the latter is taken off. Perhaps their concern was that disconnecting the airbag will lead to a fault light in the dashboard if this is detected when electrical power is present. Given the explosive power of airbags, I wouldn't want to work anywhere near them with power on. Also my airbag seemed to have a lot more nuts retaining it than theirs.

Regarding the positioning of the new tweeter, there are three basic options:

* As in the video, remove the old tweeter from its plastic mounting by the midrange unit, and install the new unit in its place.
* Leave the old tweeter in place but disconnected, and mount the new tweeter on the interior trim by the window. This requires drilling a couple of holes there, and using the slanted tweeter mounting disc provided in the kit. Some pics are below.
* Obtain the triangular interior front window trim variant which has provision for a tweeter, as used for the top-specification BMW audio installation, and mount the new tweeter inside that.
I went with option 2, which is documented below, but the other options seem perfectly viable. The reasoning is that high frequencies are more directional than low, and so having the tweeter be more oriented towards the ears than the knees would be a better choice. Option 3 is probably best of all in this respect, but obtaining and retro-fitting the necessary trim was a bit beyond what I wanted to undertake.

As seen in the pics below, the MTX logo on the midrange speaker is faintly visible through the grille over the unit: if that is an issue paint over it with a matt black enamel paint first.

Phase 2 part 1 - Front passenger side:
- Open the tailgate and disconnect the positive terminal of the battery as before
- Do not close the tailgate, as before
- Release the interior door trim following the steps in video #1
- Unplug the airbag, electrical switch, door lock cable, audio cable, and remove the interior panel by lifting it over the door lock lever
- Move the interior panel to an convenient work location as there are a fair number of things to do to it
- Cut off the existing BMW audio connector on the wires emerging from the car door, and crimp on two female colour-coded insulated connectors
- Move to the work location where the interior panel is situated
- Cut the wires to the old tweeter; if going for option 1 above, lever it out as shown in video #1, otherwise leave it in place
- Using an 8mm nut spinner, undo the nuts retaining the midrange unit and remove it
- A fine plastic mesh will be seen on the interior covering the trim speaker area perforations
- I believe this mesh does not help the sound quality, so I cut out around the perimeter of the midrange aperture with a craft knife and removed it
- Present the new midrange unit onto the mounting studs (note it has an asymmetrical arrangement of holes)
- Select the T-shaped knurled thumb sleeve nuts to retain the midrange unit and screw them onto the mounting studs
- This is where I got my next big surprise: the mounting studs were M5 but the sleeve nuts were M4!
- Due to the clearances involved no alternative to the use of the sleeve nuts seemed feasible, so I mounted each of the six nuts in a vice, drilled it out with a 4.5mm bit, and tapped it to M5
- The nuts are mild steel, not aluminium, and so this requires careful workmanship using a cutting oil to avoid breaking the tap
- If you are unfamiliar with the use of tap and die tools, watch https://www.youtube.com/watch?v=r6Ijd9o-C10
- Your mounting studs may well be M4 and if so no such work is required, so don't start this until you see what your car has; really, MTX should provide both sizes
- Unfortunately, you won't know until this stage whether the work is required; various similar nuts can be obtained on eBay but all dimensions would need to match exactly
- For option 1 above, mount the new tweeter in the now-vacant tweeter aperture
- For option 2 above, drill a 2mm pilot hole for the tweeter retaining screw, and an 8mm hole for the tweeter signal cable
- For option 2 above, feed the tweeter wires through the trim, screw on the tweeter mounting disc, and mount the tweeter on the disc
- For option 3 above, mount the tweeter as appropriate and feed the wires through to the door area
- If appropriate, join the the tweeter to the crossover via the connectors, and screw the midrange signal connectors to the midrange unit, always respecting polarity
- Crimp male connectors to the audio-in wires corresponding to the female ones above
- Lay out the crossover and wires in a neat fashion on the interior trim, placing the bigger items like the crossover in the hollows of the trim
- At numerous points where the wires touch the interior trim, apply the self-adhesive cable tie base to the trim
- Feed a cable tie through each base around the wire(s) to be retained, pull tight, and cut off surplus cable tie ends
- On completion, the interior trim can now be presented back to the car door
- Reconnect all the previous electrical and mechanical connectors as appropriate; be very careful with the electric window control connector as the pins are easily bent
- Also of course connect the new audio crimp connectors
- Re-fasten the interior trim as in video #1
- Note the interior door locking button may not appear to work properly, this behaviour is related to the central locking and should clear when power is restored

Phase 2 part 2 - Front driver side:
- Perform the steps in Phase 2 part 1 correspondingly for the driver's side
- Reconnect the battery
- The car is now in principle fully operational as usual

Sound impressions and tuning:
- The overall sound is very clear, a really big improvement on the previous very tired-sounding setup
- Bass is accurate and clean; dialled up by +2 to add give further weight to the bottom end; not true sub-woofer sound of course though
- Lower mid is fine, very clear, e.g. on voices
- Upper mid/lower treble (presence/sibilance region) is a little prominent
- Treble is bright and clear, dialled down -3 on the head unit to reduce the extra boost from the tweeters' on-door mounting
- Dialling back the old rear speakers relative to the new front ones is a good option given their relative quality (and the rear ones are nearer your ears)
- Perfectly loud enough with 20WPC output for normal listening, unless you iz a rap fanboy

Outlook and further work:
- A burn-in period is normal and expected with quality speakers
- There are audibly some peaks, troughs and resonances in the frequency response.
- Possible approaches to further refine the sound include:
- A multi-band EQ maybe
- Fixing strips of anti-vibration adhesive damping sheets to the door panels
- Filling the hollows of the panels with acoustic foam, felt, or long-hair wool to control resonances
- In retrospect, it would be much better to fit the damping materials at installation time rather than later

Good luck!

thanks for the detailed write up! do mtx do a kit for an e70 x5?


--- Quote from: mac1986 on September 02, 2017, 01:03:04 PM ---thanks for the detailed write up! do mtx do a kit for an e70 x5?

--- End quote ---
Their web page says:

* Compatible with BMW : E60 E61 E70 E71 E81 E82 E83 E84 E87 E88 E90 E91 E92 E93 F10 F11 F12 F13 F20 F21 F25 F30 F31 F35

Great write up, well done !!



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