Making good rear speaker system

This is my first post and I am tackling this tricky issue of a good sound.


The aim was to spent as little as possible but make a speaker system which would sound good.
I decided not to install subwoofer boxes as these would take space on the floor and require extra amplifier and more power from the battery.
I have medium wheelbase MB Sprinter box van which I am in the process to convert to a campervan.
I thought about putting speakers in to the back doors as in my old Hiace van. Hiace has a lifting rear door and there was a good space for speakers. I got a good sound on the Hiace so I was confident I can repeat the process in my Sprinter.

Looking at the doors I found that I would have needed to do quite bit of metal work which is not my strong field of expertise.
So I flagged the door placement of the speakers.

Instead I decided that I need to make speaker boxes out of wood and place 2 or 3 element speakers into it with crossover network.

I heard a radio garage sale program on the local radio station in Whakatane, 1XX http://www.1xx.co.nz/OnAir/tabid/61/Default.aspx. One chap was selling unused 3-element Boschmann speakers. I went over and got a bargain at $ NZ100, I guess. I thought those type speakers were new about $300? I could have got them cheaper perhaps but I was too keen as I saw they were beter quality speakers.

Titanium oxide speaker cones on 8" woofers looks nice. So I checked Internet how to make speaker enclosure. Plenty of good advice and I made the decision of using MDF for the boxes.

This choice was the cheapest and easy to work with as I could use tools at my mates motorhome building company.
Then I dumpster-dived some suitable off-cut pieces of MDF outside of a Kitchen Cupboard manufacturing company. They obviously save a lot letting people take away their waste bits

Making the boxes was a straight forward exercise but took a long time as I was learning as I made them. Working at my mates business had the advantage of asking howto questions from Bruce who has worked as a boat builder before starting his own business of fitting motor homes.

So first I cut a board big enough to fit all 3 speakers and long enough s[an the distance of back door and the rearmost rib on the van roof. 600mm long to be exact. The width I chose 350 mm leaving just enough space for the brackets to be fitted into the rivnuts I installed on to the holes on the ribs.

Then the outward facing sideboard was glued ans screwed on to the first panel and baffles added for support.
https://sprinter-source.com/forums/attachment.php?attachmentid=25357&stc=1&d=1281162442

To be continued as I need to do some cooking

As you see in my previous post I have only two holes cut for the speakers. The tweeter is surface mounted so I could choose the position for it later.

The baffle in the middle was placed there for extra rigidity.
I cut a hole in the middle with a band saw. The woofer uses whole area inside as the airspace.
The shape of the sides and the central baffle were cut close to the shape of the roof curve. Since it is hard to bent MDF, I made the curve against the wall and roof in 3 pieces of 12 mm MDF.

I did not take much pictures as I was busy doing the work. Anyway you would not be able to get those speakers anymore as I searched the Internet I found this long expired auction. http://www.trademe.co.nz/Trade-Me-Motors/Car-stereos/Speakers/auction-34040429.htm
So it looks like the guy I bought the speaker kit from have had the speakers in the garage for a few years. And I bought them from him as new.
I have not seen too many separate speaker install kits for cars like this. They might not be popular because of the complexity of the installation for average Joe. It does not worry me as I am an electronics technician by trade and wiring these is quite simple.

Back to making the box.
I had to make sure that the box was air tight, to achieve a good bass you need quite big speaker box which is air tight.
I have seen some woofer speakers installed on a ply without the box enclosure on some cars. Pretty useless as with low frequencies you get an acoustic short circuit canceling out the work done by the speaker.

To make sure my glued seams did not leak I applied sealer like silicone. Messy job and if I used surgical cloves it would have saved from washing my hands for 10 minutes afterward.

I made hole for the speaker connector athe the back. http://www.nexxia.co.uk/pics/NX-ST-004.jpg

Fitted the speakers and made the cables to connect them to the crossover network. The contact screws are clearly marked as Woofer + and _ Midrange + and - , tweeter + and - and input + and -. You have to make sure the polarities are not crossed over at any stage as this would mean poorer sound quality.
If you wiring only two speakers it is easy to swap the wires over on one speaker and listen how it sounds but with many speakers you can not rely on your luck to get it right. As Murphys law states if you have two possibilities to get it right or wrong it will be more often wrong

So to clarify, to make a simple two speaker installation to sound good: you need two good quality speaker elements installed in an airtight box or doorpanels using thick enough cable. The original cable on most speakers you buy is to thin and should not be used.
Then check the phasing so speakers are working in tandem and not canceling each other out. The way to check this on already installed two speaker system is to compare the volume by changing the balance from left to right. when the balance adjustment is in the middle you should get highest volume. If not you have to change the polarity of one speaker. For four speaker system you do the front speakers first and then do the front left and rear left together. Next fader adjustment to the rear and check the rear phase.

Continues soon...

Van Campa,
Great stuff! Looking forward to your next installment. I feel that I'm actually learning something.

steve hatfield said:

Van Campa,
Great stuff! Looking forward to your next installment. I feel that I'm actually learning something.

Click to expand...

That is good Steve, good that I spread can my knowledge

Hopefully tomorrow, I have time to complete the story what I have done this far. The speakers are up and running and sounds are worth the effort I have put into making the boxes. Needs finishing touch on the boxes to make it look good.

I just had couple of drinks with my mates so better not write too much

Cheers

That's a nice box. If the 4" isn't a sealed midrange the larger 8" woofer may cause interference with it since there's free air exchange between the two volumes. If you can get fiberfill polyester- the white puffy stuff from pillows and such- it makes a great deadener and should improve the "Q" of the system lowering the tendancy of bass in cars to pound. I put two 8" woofers in my van as well and they sound great.

The midrange is sealed so no problems. I filled the boxes with suitable amount of polyester insulation as well.
Phasing of the speakers or polarity of the speaker connection is very important. Here is a good guide how to do it: http://www.richardfarrar.com/are-your-speakers-wired-correctly/

The speakers are now functional and installed with heavy duty brackets so they will stay up there.
They sound pretty good but I might run them past some Hi-Fi enthusiast to get a second opinion.
Now I need to tackle the front speakers as I seem to get some distortion on the front speakers installed on the corners of the dash by previous owner.
I might make smaller speaker boxes on the front somewhere?

As you see on my previous post, I rounded the corners by cutting off a wedge on the corner, glueing a piece of MDF and then rounding the edges using an angle grinder.
I also made a raised surround for the woofer using 4 pieces of MDF and again using an angle grinder to smoothen the edges.

I am yet to finish the boxes. I might but a soft carpet over it rather than painting? As my bed is just below there is a possibility of banging ones head against the speakerbox

If your front speakers are OEM, then anything will be an improvement. I put some $50-a-pair Pioneers in there and I'm still amazed at the difference. The swap-over is ridiculously easy. One guy posted that he did it while stopped in traffic.

They are not OEM but replaced by previous owner. The make is Fusion and they have heavy magnets and impressive looking construction. There is a distortion coming from the other speaker. I cleaned them as it looked there might have been some iron filings
I am not happy with the placement of the speakers as they can gather rubbish which cause distortion.
If the speakers were overhead it would sound better perhaps. I might buy a pair of the same size, make small boxes for them and try them at different places.