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?

:applaud: :D :applaud:

[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.

[yggdrasil]

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?

:applaud: :D :applaud:

The 60Hz hump was gone after making the cabinets stiffer and putting them down on their own feet.

[Steve Gonzales]

So, it's okay now? GOOD. Your projects impress the hell out of me, I really want to do some veneer work myself too. Nice Hybrid. See, JBL and Altec CAN work together! :)

[Steve Gonzales]

The 411 is for use in a sealed enclosure? My friend had some with a JBL 2440 and a Altec 511b modified to accept them. Great woofers!




KUDO'S to NORWAY!

[yggdrasil]

The veneering technique used for this project was shown here in another thread by greg roberts (I could not open it now). It is not so difficult when you read the whole article, which I didn't do at first...


First I read glue, then iron. After that I ran to work. The glue was boiled dry!

This puzzled me to go back and read the whole article: glue on both cabinet and veneer, dry, then use the iron to melt them together.

[Steve Gonzales]

My biggest problem has been finding a source for veneer that doesn't break the bank. Your project has given me faith that it can be done by someone with good sense and attention to detail. Thank you.

[yggdrasil]

My biggest problem has been finding a source for veneer that doesn't break the bank. Your project has given me faith that it can be done by someone with good sense and attention to detail. Thank you.

I had to pay $100 for 5 square meters of walnut veneer in Norway. I could use almost everything, so I have 1.5 square meter left over. A good start to next project?

[4313B]

Nice project Johnny!


My biggest problem has been finding a source for veneer that doesn't break the bank.I order all my veneers from www.rockler.com (http://www.rockler.com/)

[Steve Gonzales]

I looked at rockler and they have great pricing. Thank you for the lead.

[Ben Clarke]

Cool. Seems like you could fine-tune bass response by varying the height of the feet, as that area is functioning as part of the horn path.

[yggdrasil]

Cool. Seems like you could fine-tune bass response by varying the height of the feet, as that area is functioning as part of the horn path.

Yes I think so. The feet are 13cm high in front, and 11 cm high in the back, so the speakers are tilted 4-5 degrees backwards. The opening area between the feet in front is slightly larger than the mouth of the spiral.

[yggdrasil]

Here's a few pictures of the inside of the cabinet. You'll see the spiral horn lika a staircase on one of them.


To make the spiral horn I cut about 40 small triangular pieces of MDF, which I glued together. Then I took a piece of stiff cardboard and turned 2 times around it. Fast and not aestetic but it works very fine.
You'll also see that the top piece is extended to the cabinet side to make the construction more robust.

[Ben Clarke]

Wow. Ok, I didn't see that from the drawing. Ingenuity at work. I wonder if a piece of PVC pipe might provide a more rigid boundary for the horn path.


This is unlike anything I've ever seen!

[Steve Gonzales]

That is a super cool way to tune an enclosure! OUTSTANDING WORK!! :applaud:

[spkrman57]

I like the unique-ness used there.
Ron

[reVintage]

Hey Panos and all others,

I am lifting this ancient thread as I am currently designing a midbass prototype.

To try the concept I have a pair of Lowther style midrange horns lying in my garage. Same as my friend Bo Hansson of Rauna/Opus3 uses in his Chaverex system. Will use them together with a pair of 414-8A also in my stash.

50026

Will come back when I get home from work to show some sims of a midbass to be be used from something like 100Hz. No shelving but due to the nature of 414 restricted bandwith upwards.