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Are the stock speakers behind the seats full range, or "just" subs with a crossover?

5K views 19 replies 8 participants last post by  Rofa 
#1 ·
The existing aftermarket head unit is not functioning well and I have determined that it's the actual HU which is malfunctioning. While diagnosing the system in the car I observed that the fader was not working. However, I'm wondering if one or more of the following might be true.



a) The rear speakers are not a separate REAR channel from the amp, but rather just crossovers using the FRONT channel. This would mean that fading to the REAR using the HU wouldn't produce any sound.

b) The amplifier has a blown rear channel.
c) The HU has a blown rear channel or other electrical malady (it definitely has more than a FEW issues, so this wouldn't surprise me.)


Can anyone verify that the behind seat speakers are full range speakers? And if so, are you able to use the fader on your HU? (I don't know what the capabilities of the stock Bose HU are, so maybe this is just an aftermarket question. Please note what your HU is when replying.)


Thanks to any info you can provide!



Dave O
'98 SLK 230
 
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#3 ·
Hi,

If they are the Factory Fit BOSE items, they are Woofers only, note the distinction, NOT SUB Woofers.

When adding an Aftermarket System, you are best off removing all the old technology BOSE components completely. Swap the Rears for Component Speakers, same with the Door Speakers and to save a bit of time you can pick up the Speaker Wiring at the original BOSE Amplifier Location, and also add an Amp here if you wish.

My System FYI ...............

4 x 6.5" Mid Range Speakers 4 x Tweeters 1x Active 8" 100w Sub Woofer

ERISIN "Factory Look" (not Single / Double Din), 4 x 50w Channels, Android OREO with USB Data / Charge Socket fitted in Centre Console, TPMS and Reverse Camera add ons, plus full Steering Wheel Control's via Retrofitted Modified R171 Steering Wheel and Paddle Shifts >:D

Some Pixels ........















:grin:

HTH, Cheers Dave
 
#5 ·
If they are the Factory Fit BOSE items, they are Woofers only, note the distinction, NOT SUB Woofers.
Good distinction. I was wondering if they were sub-woofers (20-200Hz) which is why I wasn't really hearing any sound when I faded to the rear speakers. If they are indeed woofers (40-2500Hz), then I should have heard music when playing from the rear channel/back speakers. I guess I will find out what the situation is once I get the replacement HU installed.

When adding an Aftermarket System, you are best off removing all the old technology BOSE components completely.
I don't disagree. However, I'm just trying to get the bare minimum invested here to get the car suitable for general driving by my son. The car has some other issues which means I want to keep the investment as low as possible so I can reserve some funds for the required items. But yes, you have a nice looking system set up there. I assume the R171 uses a double DIN? Or did you makes some modifications to fit in the double?


Thanks!


Dave O
 
#6 · (Edited)
Hi Dave,

Serious Modifications to an EBay Centre Console and slight Mods to shave the plastic edges of the Head Unit to get it to fit between edges of the Console. Took hours and hours of plastic trimming to get nice gaps around the edges.

Problem with trying to leave the BOSE Amp in is that it is not really suitable for anything other than Stock R170 H/U and Speakers, which are old tech.

Even if you just want a simple single DIN H/U Change, you will need to ditch the Stock BOSE Amp, then hard wire the Door Speakers to the new H/U, and also remove the Rear Woofers and put in a pair of Co-Axials or 3 ways or Components .............. 6.5" is really the biggest, although if you wanted to go 3 way then you could likely get a pair of 6x9's in there with a little creativity.

Worth you noting .............

My Car came with a retrofitted Pioneer Single DIN, but had no BOSE and no Rear Speakers from the factory!! The Sound Quality and distortion free outright Volume improved significantly as soon as I installed the Pair of Component Speakers behind the Seats, that was my first move ....................

There is not a lot of room and you cannot cut the Rear Bulkhead for structural reasons and Fuel Tank is banged up hard against it from behind :(

That is why I have that Surface Mount Sub in between the 2 Seats .............. Does sound amazing tho >:D

I suggest you have a read of my Cars Thread here on SLK Forum, install is a bit disjointed as it was done over about 3 months or more, stages at a time in spare time, but well worth trawling, there is a lot of info in there.

That H/U I used was designed for a W203 C Class, pre facelift model, it was the only one that was physically the almost correct size to fit R170 Console, and I also liked the Knobs and Buttons styling etc as it was a bit more in keeping with an "Old Skool Roadster" like the R170 :wink:

Thread linky is here, start at Page 2 Post # 30 then keep going, System Install is finished at Page 4 Post # 62 .............

https://www.slkworld.com/performance-mods-r170/533795-slk-320-slk-500-daves-project-2.html

HTH, Cheers Dave
 
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#7 ·
So here's what you have. Your aftermarket h/u is driving the bose system with the pre-amp out only, not the 4x45 side. The bose amp divides the incoming 2 channels to the door speakers and the rear subs. It has an integrated co. As you are only using the pre-out, you have no fader control.

It's really a surprisingly bad system and as Dave said, you're better off ditching the whole thing and starting from scratch. If you don't want to invest the time and money, you could disconnect the subs and buy a powered sub to fit under the passenger seat (assuming your h/u has a seperate sub line out). That would sound many times better than the one note wonder subs you have now.
 
#9 ·
I just went though the same dilemma with changing out audio bits. I decided to change the head unit and add an 8” subwoofer. Sounds way better, I ended up with Alpine head unit as the Kenwood one I order was defective upon install, but hands down the Kenwood sounded better. I marched the head unit with Alpine subwoofer, made a big difference to the low end but I would not really call it a subwoofer, I think two of them would be perfect.
 
#10 ·
I listen to a lot of Reggae, my 8" Active Sub together with the other 8 speakers really Kicks and is loud enough to still be clearly audible at 100mph with Roof down :D

I know for a fact the actual placement of the Speakers, especially Sub Woofers and Tweets, secure mountings and decent sized wiring makes a big difference too ....................

My home Audio System has Column Speakers with double 10" Drivers etc etc, thick gold cables and they stand on Concrete Paving Slabs rather than straight on the Carpet, makes one helluva difference :smile:
 
#11 ·
Hi similar to you if I fade to the rear speakers no sound , and I thought the Bose rears were not working , but I’ve got alpine head unit and after playing with the subwoofer set up I now have a rather delicious sounding system it’s a really clean sound not with night cub levels of bass but the Bose rears are definitely adding bass definition to the sound imho play with settings on the head unit before ripping the rears out
 
#12 ·
Your aftermarket h/u is driving the bose system with the pre-amp out only, not the 4x45 side.
The is a super good assumption. However, I have confirmed that it's actually using the speaker out wires which then go to the Bose AMP. I would expect a boat-load of hiss in this double amplified system, but it's actually not horrible. However, as I think I mentioned in one of my previous messages above, the existing H/U is emitting some horrible noise which is unrelated to the amplifier or car power system.
The bose amp divides the incoming 2 channels to the door speakers and the rear subs. It has an integrated co. As you are only using the pre-out, you have no fader control.
I agree that the Bose AMP is just using the front 2 channels and then splitting it up amongst the speakers. When I fade to the rear channel, it doesn't go anywhere and thus no sound.

I do *greatly* appreciate the input here! Instead of boring you with the "I've got this on order, and then my next plan is...", I'll post back with what I ended up installing and how it's working. I *think* I'm close! (Famous last words!)


Dave O
 
#15 ·
@dorth, if you go that route, and are keeping your Bose amp, bear in mind that the Kicker speaker referred to is a dual coil, 2 ohm each coil. That's the 2 at the end of the part no. They do a 1 ohm as well. I am no audiophile at all, but it seems to me you could either replace your 2 rear speakers with a single 2 ohm speaker wired one coil to the left and the other coil to the right. The amp would see 2ohm then as expected on left and right channels. Or you could fit two of the 1 ohm speakers, each coil wired in series, again to give the 2 ohm expected. Depends on how much you want to squander:)
Hope that makes some kind of sense.
 
#18 ·
The link in one of the previous posts will inform you that Crutchfield believe the rear speakers to be 6.75 inch. A quick look at eBay will show a number of these Bose speakers labelled woofer 6.5 inch. So I'm not sure a 6.75 will fit in. I picked up a 6.75 heavily discounted so I'll find out in due course.
The alternative is to try this, although he also used a 6.5 inch:

https://www.mbslk.de/modules.php?name=News&file=article&sid=810
 
#19 ·
Hi @Rofa ,

/\ /\ /\ That link is exactly how I did my Rear Mid Range and Tweets, then I removed the Centre Pocket between Seats and added the Active Sub Woofer.

I also upgraded the 2 tired MB Door Speakers with the same set as used for my Rear, I brutally used a disc cutter to cut the MB Door Speakers guts out of their Enclosures and then fitted the Component Mid Ranges in, left the original MB Tweets as they were fine.

I used a bead of PU Glue to bond them between the 2 halves of the original enclosure, clamps the glue down nice and tight as you screw the 2 halves back together ;)

I even soldered the MB Speaker Wires / Plug onto the new Speakers for a decent plug and play job :grin:

Here's how I did the Door Speakers in piccies :wink: ...................

























HTH, Cheers Dave
 
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#20 ·
Greetings Dave! I cheated on my front speakers. The guy I bought my 6.5 inch speakers from had adaptors which he'd had on the shelf for years and was delighted to get rid of. The speakers came with tweeters, but like you I preferred the Bose.
This https://youtu.be/aXosx3ejmoQ just happens to be for the speaker I have bought for the rear. Makes for a very easy installation although impedance matching needs further thought. The new ones have 2ohm dual coil. Not at all clear what the old ones are. I suspect 2ohm although later models are probably dual coil as well looking at second hand Bose on eBay.
 
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