First attempt for DIY - three way home cinema fronts

[supercharged]

Hi guys,

Now please be gentle, I am new to working with wood!

I have never taken on a project like this before, but fancied a challenge and a chance to spend some quality time with my father over the Christmas holidays.

I have a setup in my living room for home cinema, a 50" plasma and some pretty basic surround equipment. My fiancée and I both really enjoy films and the TV has really enhanced the whole experience, however the sound was always a bit lacking, and now the AV amp is calling it quits after years of use. So time for an upgrade!

The idea was to use the drivers and crossover from some old mission 702e's that were sitting unused, the sound ahs always been good, but the design and finish lacking.

So this is where I started -



To provide some more bottom end reinforcement a pair of 10" neodymium magnetted automotive audio drivers would be pushed into service.

I also had a pair of old wharfedale speakers in a beautiful teak finish, the drivers have long since expired, so rather than throw them away I have used the cabinet and built a new baffle and driver system to suit.

So, so far I have some mission driver and crossovers, a pair of 10" bass drivers, some old wharfedale cabinets, and a few ideas!



As you can see, initially I wanted to do a 1/4 wave folded horn for the bass drivers (infact I still do!), however taking into account the time constraints I decided to simplify the design and make the bass cabinets a simple ported enclosure.

I had done some basic modelling and lots of sketches, the cabinet volumes and port lengths were taken from the manufacturer’s recommendations.
I did full size drawings of the separate items and the cutting could begin [IMG]file:///C:/Users/michi/AppData/Local/Temp/msohtml1/01/clip_image001.gif[/IMG]

The speakers would be four separate cabinets set in two pairs, the top cabinets would contain the mid bass and treble drivers, these would be a tapered triangle shape with curved front edges and constructed from 18mm MDF.
The lower cabinets would be built using the wharfedale carcass and a baffle constructed from 18mm MDF, the port would be built in so that the surface curved into it, making it 11.5" long 12" wide and 1" tall, and also blocking off a small volume at the bottom of the speaker (that can be loaded) to make the cabinet the correct volume.

We started with the tops and bottoms of the mid-bas treble speakers, one was cut and shaped carefully, then the others roughed out and the first item used as a template with a template router bit.







To create the cabinet sides, the 18mm MDF would have to be curved, not and easy task, after some exploratory work using some scraps, the table saw was pressed into service starting the first of what would become over 120 cuts! The result was fantastic, a brilliant example of how the right tools can make a job so much easier.





Bonding the sides to the end plates was a fractious affair, we ended up using duct tape to pull the whole lot together while the glue set, it was ideal as the fabric backing did not stretch.

Here you can see the duct tape in place -



No pictures during the gluing, too much going on and my fingers were too sticky to operate the camera!



While these were drying the wharfedales were gutted ready for the next step -





The baffles for the bass units were to be cut and bent in a similar fashion to the tops, although the pieces were larger and the shape more complex to achieve the correct port length.

Top baffle first -





The lower baffle was cut and then bonded into the bottom of the cabinet -



Then the upper baffle added -







Here you can see the port entrance into the chamber -



The front and rear panels for the tops were again cut on the table saw, the bevelled edges proved to be a little difficult, but time and patience was to triumph. The bass drivers were added while the glue was setting on the tops again -



Then the mission drivers were added on Christmas day, so I could so initial trials, I could not wait to hear them!







Once transported home they were put in position temporarily, currently it is too cold to do any of the finishing work, I have decided to wax the teak of the bass cabinets, and have a gloss battleship grey for the baffles. The tops will be getting the same battleship grey for the front, back, top and bottom, the sides will be getting a walnut veneer to match the cabinet doors (between the speakers).





(sorry for the poor pictures, the lighting does not agree with my camera!)

So how do they sound? Well I think that the bass cabinets could do with some more poly fill inside them, but overall the sound is much improved over the previous speakers, a new amp and a box for the 15" PA driver I have is next on my list so it can only get better!

Thanks for reading!

J

[andy2]

Thanks for posting. Great looking speakers. I was able to learn how to do a curved cabinet from your pictures.

[Moondog55]

Whqat?? Surely NOT your first attempt, too good for that!!
Very nicely done but how do they sound??

[nac134]

Thats very impressive work. One question though - did you add any bracing to the bottom cabinet? I didn't see any in the pictures.

[nac134]

You said that you thought you needed more fill in the bottom cabinet. Is this because you are finding the sound to be boomier than you hoped?

[DQ828]

Excellent work, well done

David

[Brett]

Very nice work. Congrats.

As a not very experienced wood worker I found your pictures very helpful.

[ostripper]

Great pictures, awesome work , I will be doing this next (need better speakers).\

OS

[supercharged]

Thanks for all the kind words!

I do a lot of automotive based fabrication, so im pretty handy with metals and composites (really fancy doing some carbon cabinets in the future!), however wood is a real unknown for me, it would appear that you need a slightly more tender touch than with metals

I'm glad that the pics have assisted in getting more curved cabinets! The maths ended up being pretty easy in the end, it was the difference in internal and external radii, this is the amount to be removed with the saw. The thickness of the saw blade divided by the amount to be removed gave the number of cuts, then that number divided over the length of the outside radii gives even spacing!

Now for the sound

At the moment I am having to bear in mind that the amplifier is really holding the whole system up, it is a galactic step backwards compared to the rest of the system.

Bearing the in mind, the tops are brilliant, the sound is fast and accurate, imaging is quite fantastic, I guess that is because of the rounded edges of the cabinet helping to reduce any spikes in the frequency response. Lamb's "What is that sound" made my nape prickle, the clarity was just fantastic.

The bass speakers are astounding, the power compared to the previous system is, well, uncomparable! The only issue is, as previously mentioned by nac134, they are a little boomy, I can add some bracing to improve the cabinet ridigity and some more polyfill to see if that can smooth out the response a little.
I have adhered to the manufacturers recommendations regarding the cabinet volume, port size etc, to achieve in their words "flattest response curve possible", Not too sure!

Next I shall be putting the finishing touches to these speakers, then I think that making a new centre speaker will become top priority. I have a load of carbon and kevlar in the garage, anyone for a ultra rigid compotise sandwich centre speaker?

Cheers,

J

[nac134]

What are you using for a crossover for the bass cabinets?