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On 10/27/2020 at 12:56 PM, SME said:

That's a fascinating contraption.  The bass appears to be directional down to very low frequencies.  I wonder what happens below 10 Hz?  One source says that the Ripole configuration has its effective resonance below the driver Fs, with the given example being lower by a factor of roughly 1/sqrt(2).  The Ultimax specs indicate an Fs of 19.5 Hz, suggesting a Ripole resonance at 13.78 Hz, but the measurements don't show any drop below there.  Hmm.

It really is interesting.  Pretty sweet to have bass without shaking the room when nearfield.  Never heard anything like it. Very fast and articulate but at nearfield I could localize the bass.  Would need two or three of them to get around both that and also the efficiency issues.  

On 10/27/2020 at 10:46 AM, atltx said:

Ripole is the term I learned for this set up.  Ripole brought me to databass.  Was looking for 18 inch drivers that would give the best result for my tastes in hi fi.  Pandemic killed all the new ideas this website gave me for anything outside of hi fi.  The drivers I collected are stored face down and acting as furniture a few feet away from me waiting on 1 more.  

You found a pot of gold.  Enjoy it like it is or upgrade the drivers.  Build another 1 or 3 and be done for life.  

I really did!  Only thing is they are NOT efficient and can't handle all that much power before they don't sound so hot.  I had three of them I would, indeed be in heaven.  That would be 4 more drivers, though!  I'll tell you what, being able to get that rumble in my seat with my wife not having to endure the beating I like was a win win during movies.  Alas, I've already dismantled and put in two separate sealed boxes, both front and back.  Not sure if it has the same fidelity for music just yet, but with about 1500 watts to the pair, I can really rumble.

Do you always want positive summation with dual subs and then EQ afterward or do you sometimes use the second sub to even out the response at the cost of SPL?  

48 minutes ago, klipsch said:

So the measurements were on axis and off axis in open air / outside with no boundaries? Or the measurements were on axis and off axis in a room / house / space with boundaries? 

Indoors with boundaries. Forgot to add the on Axis (in Room) response.  12 inch away so don't know how much room was a factor.

That's odd.  

So I've been lusting after a Parts express UM18-22 18" with sealed flat pack.  They were out of stock when I looked but I found a CraigsList add for two ultimax's in a crazy looking Dipole box.

Very close to this build here https://www.linkwitzlab.com/woofer.htm

I've been telling people that the bass is directional and no one wants to believe me.

So I finally measure both on-axis and 45 degrees off-axis

The build is incredibly inefficiant as I'm currently bridging a crown K1 at 1100wats 8ohm and have to boost sub output from the Denon receiver quite a bit.  Not so much nearfield but anywhere else I put in the house.

I have a sealed flat packs on the way so I can separate these beasts and pressurize the room better but the fact that I can rattle my brain while watching a movie and have my wife, literally next to me on the couch and she doesn't have to endure the bass that I love is kind of magical.  Not sure I want to take this thing apart now.

Just thought I would share.