Extremis / ??? 2 way mains

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Ok, here is my situation. I'm looking to complete a whole bunch of projects I have laying around, namely a couple of amps, a set of bookshelf/computer speakers, a sub and a set of mains. So, funds are a little on the short side, I'm afraid. :(

I do have quite a bit already however, including for the mains two Adire Extremises (Extremii?) in the closet and an Avalanche 18" on it's way for sub duties. The box for the Avalanche is ready to go, it's 7.5 cubes (212 litres).

What I'm looking for some advice with is my mains. The room that they're going into right now is medium sized, but it'd be nice for them not to be dwarfed should my listening room get bigger. I'm interested in trying an open baffle project, but I worry about the Extremises running into issues with extension with no box and a low (~60Hz) crossover point.

For the upper crossover point, I'm unsure where to put it. I think I'd like to keep it out of the 500 Hz area to avoid it affecting vocals too much, but want to avoid beaming issues off-axis, so a crossover much above 2500 is probably a bad idea. I've been looking for drivers to fill the top range, and have come up with some small wide range units.

The Tang Band W2-880SC is low cost and seems like it could cover the range I need, though it's a little ragged on top.

The Hi-Vi B1S is even less expensive and is alot smoother on top.

Can anyone help steer me in a productive direction so that the time my young wife does let me spend messing with different configurations is better spent?

Thanks alot guys.
 
with the extremis you're definately OK up to 2.5Khz.

I cross mine around 3k to some vifa tweeters. I forget which series tweeter, but they're not very expensive (~$30 each) and I'm using 12db/octave crossovers that I made myself with some electrolytic caps and air core inductors that I would myself. I do think the crossover could use a bit more tweaking to perhaps get better alignment in the time domain, but I really lack serious testing equipment.

The extremis is a good choice for midrange... except that horrid efficiency
 
For an enclosure the extremis is pretty versitile. Since you're running an avalanche below it I'd suggest sealed boxes for the low group delay and higher F3. Open baffle doesnt sound like a bad idea either and I think you might be able to make it down to 60hz in a Uframe or something, but I'm not really very experienced with OB
 
I have my extremises in a TL right now and I'm satisfied with the performance. It was my first TL and I designed it myself(so its definately not optimal) but it still sounds decent. Now.... if you could get GM to design you an extremis TL I'm sure you would love the results!

If you wanna spend an extra 200 dollars and can live with 80db effiency then go for the OB!


Why does adire use a dipole tweeter above 1.8Khz? I thought linkwitz said using dipole above 2khz was detrimental to sound quality.
 
audiobomber said:


It doesn't look like a single pair of Extremi will give you a viable system. Efficiency is l-o-w!

http://adireaudio.com/Home/KITDDR.htm
That's not a function of of the Extremis, as much as it is a function of a dipole speaker. The DDR has a low efficiency because the crossover supplied compensates for the roll-off on the low end, to achieve flat response down to 100 Hz on a 12" wide baffle. ANY dipole system with a 12" wide baffle will have low efficiency when extended down to 100 Hz.

Dan Wiggins
Adire Audio
 
no comment on the dipole tweeter above 2k Dan?

I might have to buy another pair of extremises and a Neo3pdr(plus a nasty long list of crossover components) and try it out.

I find it interesting that the tweeter is in reversed polarity with the extremises also.... Did you design this yourself Dan?
 
So Dan, using one Extremis per side OB wouldn't give anywhere near the extension I'd need. What would you recommend for an enclosure Dan? The 33Hz 21L box would allow me to cross it over before the phase and group delay really rise.

Are their any graphs of the 30 degree FR of the Extremis anywhere?
 
The NaO's, use a rear-firing tweeter, so it may be a matter of differing opinion.

I'm not very knowledgeable about the NaO design except that it's an OB MTM with a rear firing tweeter(which can be switched on or off)

The rear firing tweeter may be of the same polarity as the front firing one or it may not, I do not know.... But there is a thread labeled "ambience tweeters" and I was told there that the point in a rear firing tweeter is to flatten power response and the rear firing tweeter is supposed to be of the same polarity as the front(bipole).

I'd like to hear what dan wiggins has to say about this and it's relation to the DDR...
 
Bass,

I figure is you want dipole, go dipole. Electrostats, planar magnetics, etc. are all full range (well, wide range) dipoles. Using a NEO3PDR with the rear cup off will also make it a full range dipole. Same frequency response front and back.

As far as the XO goes, pretty much all crossovers that have 180 degrees between the stages (2nd, 6th, etc) will have the polarity of one of the drivers reversed. It's nothing weird.

And yes, I designed the crossover.

Mr. Teal,

If you need more extension, then an OB is not the way to go, unless you want to make the baffle a LOT wider (like 60" or so). Dipole speakers just won't play low without a lot of EQ and power, or a really wide baffle.

Most people go for the 21 liter, 33 Hz tune alignment as it reaches plenty deep, but isn't too physically large.

Dan Wiggins
Adire Audio®
 
Nope. ANY dipole speaker is low efficiency. With an active crossover, you still have to compensate for the dipole roll-off on the low end. Rather than cutting the top, you boost the bottom. Of course, that means you still need the extra power to get the SPL required on the low end.

Remember, most active dipole solutions use 10-15 dB of boost on the bottom end, meaning that the lower frequency efficiency is cut that much. You still need a LOT of power to get extension on the bottom end.

With a passive XO, you do cut all ranges, but only need one amp. Since it's assumed you have at least one big amp (remember, with active you still need a lot of power on the bottom end because of the EQ gain), then why not use it full range?

Dan Wiggins
Adire Audio
 
DanWiggins said:
Nope. ANY dipole speaker is low efficiency. With an active crossover, you still have to compensate for the dipole roll-off on the low end. Rather than cutting the top, you boost the bottom. Of course, that means you still need the extra power to get the SPL required on the low end.

With an active XO you'd still have low efficiency, but surely you'd gain at least 3dB overall?
 
audiobomber said:


With an active XO you'd still have low efficiency, but surely you'd gain at least 3dB overall?
Nope. If you have a woofer on a 12" wide dipole you will lose ~18 dB output at 100 Hz compared to the 1 kHz output. That is the acoustic loss of the driver/baffle system, and is completely independent of the type of crossover or power. It's the ACOUSTIC loss of the system.

Dan Wiggins
Adire Audio
 
Thank you much for the quick response Dan;)

I think I will probably be building the DDR as soon as I can afford the extra drivers and crossovers.

Dan.... Have you listened to Linkwitz's Pluto or Orion, if so what would you say about the overall sound quality of the DDR compared to those(from 80hz on up)? Thanks again Mr. Wiggins
 
So, let me see if I understand this right.

The low efficiency is due to the front and rear wave interfering with each other. Widening the baffle lowers the frequency that this happens at, but is less aesthetically pleasing.

You can lower the extension by using a linkwitz transform type circuit to attenuate the high end, or by boosting the low end, but you'll still be limited by the Xmax or Pmax of the driver, and might not get the overall SPL needed to integrate with the other components of the system.

Are there any free or demo software packages that can model dipole speakers?

Thanks guys
 
Hi Dan and everyone else,

I heard a single DDR at Dan's shop and it has a ton of potential and should be a really fun project. The cabinet is really simple (just a baffle) and a bunch of different versions could be made rather quickly for educational purposes.

Oh and Dan, I know of a couple dipole loudspeakers that hit 90db efficiency from 90Hz and up ;)
Starting some time next week, we are building a pair of the big ones. When you get back you need to come by the shop and check them out!

Take care

Nate
 
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