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Franken-Speaker Friday Again, Time For "The BIGGER Smaller Advents"

dc270

dc270

Now Off the Reservation
This is going to be a twist on one of my favorite Advent speakers. It is basically a Smaller Advent on steroids, or done to the “quads” in a classic line array. The cabinet is radical departure from the original ones however. It has a raked minimal baffle plane set up for the woofers and a unique tweeter “rail” system. The rail allows each individual tweeter to be adjusted up or down and in or out on the 2, 3/8" threaded rails and tweeter frame eyebolts. This setup should eliminate baffle board diffraction issues and sympathetic woofer vibrations for a cleaner detail sound.

I choose the Smaller Advents because of their great bass capability, pretty good midrange and good tweeter offering. To maintain the original “flavor” of the Smaller Advents I went with the same tweeters, repainted the frames and added a soft cork piece to the tweeter face to help with any more diffraction issues. The tweeter rails will be mounted to the side of the woofer cabinets with rubber grommets to eliminate vibration transfer. All the woofers have been re-foamed and the cones treated to help smooth out the midrange.

The one caveat to this design will be the obvious size- but the predicted output should be well worth it though. It will be wired in series parallel and should have very good power handling and excellent imaging! It will still be their classic acoustic suspension design with "polyfill" used inside the cabinets. This should still be a 4 ohm system & will include an L pad for tweeter adjustment. I have not decided on a cabinet color or cover scheme, but will it probably be black. Fixed wheels will be attatched to the back for easy manuvering.

The pictures are the early construction phase of the cabinets and the tweeter rail mechanism. I built this same "tweeter rail" 25 years ago using a differant set of tweeters and had pretty good success with it then.

I will post more latter as it developes. Thanks for looking-
DC
 
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Hmmm...........

Howdy, dc270! This looks like a very interesting project, but I can't quite get my head around your "tweeter-rail" concept- or I think I can see it, but......

Will be watching further developments.....willhowl:yes:
 
As you look at the rail, picture it mounted to the cabinet side next to the woofers. As you can see the tweeters are eye bolt mounted on two pieces of all thread and can individually be moved up and down the all threads by losening the nuts under the eye bolts. The pitch of each tweeter can also be adjusted by moving the same eye bolts in and out of the tweeter frame. Hope this helps...
DC
 
dc270 said:
This setup should eliminate baffle board diffraction issues and sympathetic woofer vibrations for a cleaner detail sound.
Click to expand...

:lurk:

Note: you'll still have diffraction at the sharp edges of the tweeter (although I'm not sure what you're doing with the cork so you may be dealing with it) but the delay will be so small that we'll never hear it. Nice looking bass cabs!

Ray
 
Thanks for the comments Ray- would you advise rounding the edges of the tweeter frames? Good feedback I appreciate it!
DC
 
Like I said, you'll probably never hear it as the delay between the radiated sound from the driver and the re-radiated sound from the edges will be miniscule. We're talking about something on the order of .04ms. I really don't think it will be anything audible. Where you might run into some trouble is the re-radiated energy from the edges bouncing off the woofer cab. I don't know how much effect that will have as it will only be one side of the tweeters and if you have them "diamond" mounted like that it won't be coming straight off. Maybe just add some "space" to the high end.

If you want to kill it off I'd make a small frame for the tweeters, maybe 1/2" and put felt on it. That'll probably keep anything from coming off other than from the driver itself.

Ray
 
this is f***in' AWESOME !

you are the king of monster garage speakers DC :thmbsp:

whatcha gonna use for a crossover ?

May I suggest some vintage oil caps :D ?? They sound REALLY nice in my Large Advents . . .

OK . . . it's all your fault DC. I MUST begin a pair of 'Double Stuff Stacked Advents' :yes:

same idea as these, only using Original Large Advent Woofers and Tweets. I think they may need casters :scratch2:

cant wait to see the progress !
 
Thanks again Ray- I will take you suggestions under serious consideration. Now that you mention the woofer baffle interaction I might place a stip of open cell foam between the tweeter rail and the woofer baffle to further break up difractionn issues. Great observations!!

Markus- woah there buddie it only a pair of speakers!!! But hey if it inspires you then I have my end result in the posting. Vintage oil caps would be a good option- I have had very good results using Solens and polys in the past but you have merit from a vintage point! Thanks DC
 
Another cool project :thmbsp: Looks forward to seeing it done. I have 2 sets of KLH 17's i keep looking at for a tower but I think i am going to give a set to a friend as i don't have time for more projects right now. I'll just live vicariously through you. :D
 
CAREFULL kfa..."I boldly go where no man has gone before" with some of my speaker ideas. I don't push the envelope so much as I drag it kicking and screaming to completion- it's my style! I bet your "17's" would make a great tower project- but giving them away is good for the soul too. Beyond the 4 pairs of these SA's I still have 2 more sets, could be a rear surround match later on!

markus......man go for a walk! or maybe not, cause when I go for a walk I see trees and wonder how many or how big a cab I could built from them.....I tried reading but the paper is made from trees as well and the binding probably has good glue to use.....god I AM sick, the soldering fumes have had more effect than I planned...

DC
 
Extra Pics Bigger Smaller Advents

Here are some more pics of the idea in evolution, maybe it will help grasp the idea. The tweeter "rail" is detatchable.
DC
 
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Ever think about adding another tweeter and making it a Bessel array?

Ray
 
Ray I will have to read up on Bessel Array, will it function for 5 tweeters and 4 woofeers? I have 2 extra tweeters just so happens! Your thoughts?

AV- This is supposed to stand up right- or would be an extremely large center channel!!
 
A Bessel array is a design for 5 (or 7) tweeters. The idea is that with the right wiring (2 are in series, the others in parallel with one out of phase) they approximate a point source, i.e. no comb filtering. There's plenty of info around the 'net. If you can't find enough let me know and I'll dig up my references on it. It's a pretty cool concept. Might be worth it to wire up one speaker each way and see what happens.

Ray
 
I took some time and did some homework Ray- looks very interesting! My drivers are all 4 ohm so I may have to run them in series array arrangements for a 14 ohm load. I will probably need padding as well. Is there a particular driver arrangement they are to be set in, IE the out of phase driver at the top or ?
Thanks again for this idea- seems to have a lot of merrit!
DC
 
The way I've seen it done, and the only way I've played with at all is with the top and bottom drivers being the 1/2 power (series) drivers and the 2nd from bottom being the out of phase one and I've only done the parallel version. I haven't played with it much but I remember some McIntosh speakers I saw at a trade show that used a Bessel tweeter array. I couldn't do much of a real listen but they sounded very good from what I could tell.

Ray
 
Here is where I am with these thus far. Got the cabs vinyl coated and the drivers wired up and set in.

No crossover but I did play the woofer section- wow this is a LOT of bass! Wil work on the xover this week and getting them balaned- should be interesting.
DC
 
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