Altec / JBL project

[yggdrasil]

Last summer I picked up a pair of Altec 806-8a on 811b horns, a pair of Altec 411a woofers and N800 crossovers.

I'll take a shortcut and show you the results. The tour will follow.

[yggdrasil]

Primary goal - build a small speaker with acceptable low frequency response and a bass with more punch than my larger JBL's.

While searching the internet for horn loaded bass cabinets i came across this web-site: http://www3.ocn.ne.jp/~hanbei/eng-intro.html

I wrote to the author and he helped me calculate the upsized version of the 3d-spiral horn.

Here's the drawings in metric (cm) measurements.

[yggdrasil]

By this time I was electric! In only a few hours I used materials at hand.....You see all the dust on the horns and the boxes just put on a stand with most of the bottom free so that the spiral horn could blow freely.

You'll also see the wiring from the crossovers placed on the floor beneath.

The bass was quick and dry, and quite deep.

The speakers stood like that for 6 weeks before my wife exploded..... She is really very understanding, this is after all our living room.

To summarize the impressions: mysterious peak at 60Hz, dead above 10Khz and hard upper midrange.

To deal with this I decided to add UHF drivers, and aquired a pair of 2402's and install new crossovers with high quality caps.

The 60Hz was another puzzle. First action was to make the cabinet stiffer. Second I built feet formed like an U pointing the mouth of the spiral horn towards the listener.

[yggdrasil]

Now it was time to make these small speakers look ok.

First I painted the back and all other visible parts that should be black.

Then I started out with walnut veneer. Only my second veneering job, so it took time! 7 hours on the first side. But the result was impressing.

On this picture you still see the tape used to connect the two sheets of veneer. Later removed with terpentine (I think is the english word).

[yggdrasil]

After veneering I treated the speakers with boiled linseed oil and they started glowing.


Here's the lot just before putting it all together.

[Steve Gonzales]

Very NICE! I love to see projects. I was just suggesting a JBL UHF to a augment an Altec two-way in another post, great!. I hope someone can help you figure out that 60hz hump, EQ it maybe?

[yggdrasil]

After playing 4-5 hours I managed to find the computer and microphone. Low quality mic but enough to get a fair picture.
I almost forgot. They are now crossed over at 700Hz and 4000Hz.

And the sound: Impressing. No equalizers used, nor necessary. The bass is there from 25Hz, very dry yet powerfull. The mid-range is very detailed and not hard at all. The UHF: 2402!

The project was a success way beyond expectations.