Hi All-

When installing new speakers in the rear parcel shelf, is it better to leave the bottoms of the speakers fully exposed to the inside of the trunk (as in my 108) for air supply (not the 80's band...) or to enclose them with some kind of bass box or similar to minimize the amount of sound lost into the depths of the trunk?

Just read a thread about the 123 chassis, and rear shelf- it has a full metal bulkhead beneath the shelf that essentially closes off the speaker apertures from the trunk- read that this reduces the amount of bass the speaker can produce-

I am confused- do I want to enclose my 108 rear speakers or let them remain exposed to the trunk interior?

If they should be enclosed, any recommended methods? The parcel shelf itself appears to be some kind of plastic.

Thanks,

JAS

__________________
94 E320
71 350SL

I'd leave the speaker bottoms exposed. My '72 250 has the original rear shelf speakers with the metal panel blocking the speaker bottoms and it kills the bass. I improved mine considerably by adding a pair of 6 x 9 Sony coax speakers in the under-dash cardboard panels.

Happy Motoring, Mark

__________________
DrDKW

Hello Mark.

You should enclose the speakers.
www.crutchfield.com sells foam baffels just
for this purpose.
They insert behind the speaker.

Hey JAS, if this was true.
Why do stereoshops put subwoofers in boxes?
If an eclosure kills bass then this seems like
a waste of time,effort and money

An enclosure or box is designed to control the
cone movement thus making the speaker work
in an optimal enviroment.

That is why you can't use a non free air subwoofer
without a box.
The free air sub is designed to have a lot of cone
movement/travel so it can compress the air in
your trunk(read big,to big enclosure).

A non free air sub needs the right size box to perform
best and this is done by controling the cone movement/
travel by using the pressure created in the box.

A sealed box will have tight punchy bass because
of the compressed air in the airtight box.
The output is less than a vented box but you
have better bass extention(transfer of bass to air
or object).
You can use a higher wattage amplifier.

A vented box will sound louder but has to be
designed correctly or otherwise it will sound
horrible,it can even destroy the subwoofer.
It will take less wattage to power the sub
but if overdriven again this will result in damage
to the sub.

There are a few more but are a combination
of the previous ones.

The reason why there is no bass for the
rear speakers in the parcelshelf is because the
enclosure is most likely full of holes and second,
the enclosure is to big for the speakers.

Mark,for cleaner crisper sound you'll want to
enclose all speakers(foam inserts,ask your local
stereoshop for them,they come is all sizes).

For REAL BASS you'll need a subwoofer(s) and
a power amplifier(s)
If your on a tight budget you can go with a
power bass tube.
Bazooka has been in business for a long time
and makes close to the best.

I hope this aswers most of your Q's

Louis.

SORRY GUYS I have the names mix-up

Louis

In the past, most factory car stereo speakers were flush-mounted in the rear shelf, without enclosures. This is the arrangement I have in My '84 Honda Accord. I upgraded the blown-out Jensens that the P O had, to a pair of Coax Pioneers without enclosures and they sound superb. Possibly, a properly designed and matched pair of enclosures could make them sound even better, but for me it isn't worth the trouble.

I'm talking about full-range or coax speakers connected directly to the radio, not a subwoofer, which may require an enclosure and power amp, or those monster-blaster systems the kids put in their Civics to rock the whole neighborhood!.

On the other hand, my '72 250 has a double wall rear shelf with factory speakers in housings that can not be flush mounted because then they would hit the second metal wall that is about 1 inch below the speaker holes. I presume the double-wall shelf is for added body strenth and also for a firewall between the cabin and the trunk area, so I'm reluctant to cut holes in this panel. So I lived with crappy sound until I added a pair of 6 x 9 coax speakers under the dash.

If your W108 speaker holes are open to the trunk, go ahead and try them without enclosures. You can always add them later if you're not satisfied.

Happy Motoring, Mark

__________________
DrDKW

Okay, thanks, that explanation makes sense-

So, I think I will try simple foam baffles- this will prevent the Polk 2-way speakers in the rear shelf from being overwhelmed by the amount of space (air) that they are otherwise exposed to in the trunk-

(To get this clear in my mind, on the other hand, being very tightly enclosed, like in cars with the double bulkhead at the rear shelf, also can kill bass).

For a non-amped, non-subwoofer system, in order to take best advantage of the rear 2-way speakers, the foam baffles seem the best bet. Am I correct with this conclusion?

-JAS

__________________
94 E320
71 350SL

Yes you are JAS.

Attached pic of baffles.

Louis

Attached Thumbnails

 

In my 250, the double wall construction on my rear shelf prevents any kind of flush-mount speaker installation. The factory rear speakers are mounted in flimsy plastic housings that raise them up about an inch above the speaker holes and, combined with the the 1 inch space between the shelf walls, doesn't provide an adequate enclosure. A friend has a '72 220 (same body as my 250) that the original owner cut through the double wall and installed a pair of 6 x 9s, without enclosures. They sound much better than my 250's factory speakers ever did.
If your speaker holes are already open to the trunk, you will probably get decent sound, with or without enclosures.

Happy Motoring, Mark

__________________
DrDKW

Thanks a lot, guys, for your advice.

I think I should be in good shape, with the speaker holes open to the trunk. Baffles will help the speakers out, too. Also, not mentioned yet as a consideration- the baffles should help keep road/trunk noise from otherwise entering the cabin of the car through those speaker apertures, right? Best of both worlds- keep unwanted noise out of car, while providing the right enclosure for the speaker to be able to do its job.

I'll let you know how it all turns out, should be finished in about a week.

-JAS

__________________
94 E320
71 350SL

Mark.

You could make 1" wooden spacers to raise the
speakers.
The baffles are made of foam and compress to fit
the hole.

How much space is there between the speaker
magnet and the metal baffle?

Hard to be exact but a guess is close enough.

You only need 1/8" of clearance on the bottom of
the magnet.


I have seen other people do the same as you,
with the 6x9's,but it just leaves a nasty looking
hole when you remove them,in order to sell the
car.
I like all my stereo installs to look stock and be
fully transferable to stock without having to
buy new panels.


I have a W123 83 300 Turbodiesel wagon.
All my stereo gear will be custom installed,so
that it all looks OE, but that I can remove
everything and return all to stock.

I'm going to move the radio up,closer to climate
controls(this is one of the few things I'll need to cut,
but easily replaced).

Install a 4x6" speaker for center channel(building
5.1 surround sound system)

Build custom kickpanels for 6x9's.(for front channels).

Integrate 4" or 4x6" speakers in the headrests(rear front channels).

Install a 4" or 4x6" speaker under the front armrest.
(rear center channel)

Custom build sealed box with 15" subwoofer behind
rear seat.(part plexiglass,part fiberglass and part mdf,
mdf= meduim density fibreboard).

Custom dual tier plexiglass amplifier rack behind the subbox.
(3 or 4 amps),and some other goodies.

Custom speaker pod(for 6x9's) suspended from the rear roof
where the OE speakers are.(for rear channels


I can already hear everyone saying, another boomer.
But if you look closely you'll realise that this is a surround
sound system wich is geared to sound quality and not
to booming.

Altought it could pound with it's 1500+watts but if I really
wanted to rattle the windows I would install 2-3 subwoofers.
This would really be overkill.

I've slowly started on this system ,but I'm also fixing up
the wagon at the same time.

I'll keep all up to date and post pics as I progress.

Louis

Sounds like quite a system. I tell you what, the system in my 84 TD sounds pretty bad. I just did a new head unit and replaced the stock size speakers, which are admittedly very small. Wasn't looking for more than adequate sound from it, really. I want to do a better job on my 108, which is what I drive.

I totally agree with your notion that things should look stock. In the 73 108 chassis, evrything I am doing fits under stock grilles, only the head unit will be non-stock looking- but an original Becker could be installed easily- same size.

Good luck on your TD- I'll keep you posted on my install.

-JAS

__________________
94 E320
71 350SL

Louis,
Since I refuse to cut holes in the doule-wall shelf in my 250, I've given up on improving my rear speakers. I could have put a nice pair of self contained 2-way cube speakers on top the rear shelf, but I didn't want to invite thieves.
My original rear shelf speakers are now just filling in background sound, as my primary audio is coming from the 6 x 9 coax Sony speakers I installed, out of sight, under the dash.

Happy Motoring, Mark

__________________
DrDKW

Mark.

That is what I'm trying to say.
You don't need to cut any metal at all.

I attached a drawing to explain this.

If you wish to do this or for others that would like
to do this.

I'm sure there is some space between the top of
the rear shelf and the double wall.
So the 1"spacer+ the space from the rear shelf
down to the double wall should give you more or
less 2"-2 1/2" of mounting depht.

You remove the flimsy plastic spacer.

Each new speaker set comes with a template that
you use to trace a hole in wood or other material so
that the speaker fits in the hole.

Now you trace the inside and outside of the template,
(instead of just the inside)this gives you(in this case)
a 1"wooden spacer ring instead of that flimsy plastic one.

You attach the spacer ring to the shelf by way of the
original mounting holes.
You then drop in the foam baffles.
Then drop in the new speaker and mount it to the
wooden spacer with the provided screws(drill pilot
hole in wood before you screw in the screws)

Use more or less same size speaker as OE.
This should keep the mounting depth the same,eliminating
any clearance problems.

This kind of set-up can be used in front doors also,but
will need custom work on the door panel if you want
to use 6.5",6x9" or 8" or bigger subwoofers.
The foam baffles only come in sizes 6.5" and lower.
The baffles also seal of the speaker from any moisture.

Louis

Attached Thumbnails

 

Thats like what I have now but without the foam cups or baffles. The original rear speakers are mounted about 3/4" above the holes in the shelf, which are there mainly to provide clearance for the speaker bottoms. The cheesy factory plastic housings are thin and resonate and the 1" space under the speakers makes a poor sound chamber.

Awhile back I was thinking about something like you've described to adapt a pair of 6" coax speakers. For the 1" spacer I was thinking about something ready-made and heavy that wouldn't resonate, like a pair of 7" cast iron fry pans with the handles and bottoms cut off, but I feared that with only a 1" air space under the shelf it would still have poor sound quality, dissappointing after all that work.

I'm satisfied enough with the 6 x 9s I added under the dash that I won't mess with the rear speakers for now. Thanks anyway for the information. I may try those foam cups on my next speaker installation.

Happy Motoring, Mark

__________________
DrDKW

For any resonance, dynamat or the like can be applied to
any metal surfaces to dampen the resonance.

Louis.