The non-ultimate dipole: Sinfonia
I guess I've decided that today is a good day to get all of the speaker design ideas out of my head and onto virtual paper. This is the evolution of my dipole project, which as some of you know has been stalled for a while.
In essence, I've thrown in the towel on getting dipole full-range, largely because of the cost of good dipole tweeters (and/or the complexity - see Linkwitz LX521) and decided instead to see what happens if I match the radiation pattern at the front using a waveguide. I may experiment with a rear-firing "ambience" tweeter later.
Now that I've drawn it up, it occurs to me that it could easily be considered as merely a hybrid of Linkwitz' earlier Phoenix and Orion designs. Oh well. The use of the waveguide and one design detail of the lower section are different at least.
It's called Sinfonia which is (per Bach) "a three-part invention."
Comments
Revised as below, as I bought a pair of tweeters that should work well with a low(ish) crossover to a cone mid. This one might actually become real, I'll see if I can set up a prototype this week...
Is there any particular reason why the top section is stuck in the middle of the bass box rather than the front (where it can more easily braced)?
The main reason is symmetry front to back. If you put the top section at the front, then you need to use delay on the top drivers, which means that at the rear you are effectively delaying the bottom section. In the extreme case, the delay would correspond to about 0.6m or half a wavelength at about ... er, um, around 280 Hz. Which is above the crossover frequency, but not by a lot.
I guess I was thinking the top section would be free-standing.
Not a hope in hell. Think about the mass moving about up there. It's not much and it's not far but that plate is supposed to be dead...not like that it won't.
Here's a quick test combining the AMT with a 12" dipole woofer. Crossover at 1250 Hz. It works, the tweeter seems to be able to handle it but the whole thing doesn't sound right. Was just curious as to whether it could be made into a 2-way (it can't, I've decided, at least not with this 12" driver). Will try the 8" driver next.
Seano, maybe sand-fill in the top baffle?
Maybe...worth a try at least if the configuration is akin to the photo. Screws are easier though!
Today's test mule - 3-way as shown in diagram above. (Haven't hooked it up yet)
Yah Mule!!!
"when I say go, I means go!"
I wouldn't even know where to buy pipe cleaners
Graham, that's why I'm running the class!
Actually the mule sounds much better than the donkey. I think Nigel will like these tweeters, they even have an ESL-like sweet spot. Going to try some super tweeters, currently in a mild mannered cardboard box being held for ransom by UPS.
I need to do some more measurements tomorrow, some dimwit wired the two woofers out of phase and then wondered why the woofer amp kept clipping. Hm... Maybe I shouldn't be running that class after all.
We've all done it John, even the one's that swear they never did.
They Did!
There are 2 kinds of speaker builders in this world...
Those who have wired speakers out of phase
Those who are going to wire speakers out of phase
How done it sounds, John ? the last iteration sounded v nice bar the tweeters, so I am expecting an even better result this time.
How about I pick Graham up at the airport and we come over for a bbq? or will you take the whole thing to Terry's?
BTW- some more changes to my system last night - getting there.....yummy!
Graham? Airport? In October or earlier?
Ooh, now that sounds tempting Nige.
Let me think about it...
Can we add to Bathurst weekend? Dunno how that works for you.
I am a bear with a small brain when it comes to flying things.
How do I determine how to fly from Melb Tullamarine to Bathurst?
Joz flew up to Syd and hired a car one year Syd-Bathurst-Syd then return trip.
Quicker.....Joz is made of money though....
Graham, if you want to extend your Bathurst trip to include Syd, I have a spare bed (and 3 more if I send my son to stay at his mum's). Plenty of rheum and as you know plenty of ways to get into trouble in Syd.....
Cost more to fly from Syd to Bx than Melb to Syd. Prob. I can ferry too.
Ooh, now it's getting interesting.
I lurv having options
I'm gunna create a new thread for Btx 2014, so it does pollute others %-(
Wow!!! A new thread! Here??
