WFW FAST / WAW with SBA racetrack woofers and SB65

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The idea came from xrk971’s 10F/RS225 FAST thread.

I was looking at woofers I could get around here since the Daytons are not available locally, and shipping here is prohibitive.

A distributor with good pricing recently showed up for SBAcoustics, and it got me excited that I may find a suitable woofer, as I already had the Visaton B80 laying around.

Going through the SBA website is no joke! There are so many products, it’s easy to get confused.
I was going nuts trying to find a match to the RS225, then I stumbled onto their new 5x8” race track woofer.

It looked ok to try and I shared the idea on the 10F thread.

That’s when BYRTT pointed out that c-to-c using the 5x8 woofers and a small full range driver would be very interesting, and how about a MTM, or in this case WFW?

The data that BYRTT shared pushed me in that direction easily. Having played with XSim and the manufacturer’s curves, I thought it had great potential.

So, I contacted the distributor, and 2 days later, all 6 drivers showed at my door, COD for only $6 shipping cost! That’s service!

BTW, as a plug, this is the distributor in Taiwan, should anyone be interested. They are very nice, and they speak, or write, Chinese as well as English.

thlaudio web site pages

So, this will be a thread on how it will turn out in the end.
I have an idea, but I may change a few things along the way according to measurements, I’m not inflexible.

Shall we start?

So, as we already know, the woofers will be the 5”X 8” SB15SFCR39-8. Two of them per enclosures.
The enclosures will be sealed.

Inside, sandwiched between the 5x8s will be a 2½" SB65WBAC25-4. It will have a sealed space inside the enclosures. This driver has been reviewed as having a great dispersion and great high end reach… close to a tweeter.

These are BYRTT’s measurements of this driver, in FR and dispersion… pretty good!

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MTM, or in they case WFW, improves the vertical polars, as more data shared by BYRTT showed here

720061d1544007135-10f-8424-rs225-8-fast-ref-monitor-polar_perceval-png


After I build them an enclosure, I’ll first try a simple 1st order XO, but will probably settled on a more elaborate one later on…

720090d1544017406-10f-8424-rs225-8-fast-ref-monitor-xsim-wtw2-jpg


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I’m sure I forgot something, but this is the beginning, so, I’ll keep adding up.
 
Craig, I'm pretty sure I don't have a hole cutter that big, except the one for foam!
But, I'll keep it in mind.

Only had time to put the drivers through DATS, and that's right out of the box. I will have to let them play a bit then measure again.

The good news is that impedance matches completely with online specs, but T/S are a little off... not that much, and might get closer to online specs after break in.

So far, so good!
 

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Alright, finally moving on this...

It was a windy, rainy and cool day here, so I decided to make a box.

Went optimal with 60 litres. I was expecting big, but this might be a little too much.
I think I can go down to 40 litres, and only lose 3Hz at f-10.

Didn't have time to get the parts for the more complicated XO, so I rigged this with 4.8mH and 3 Ohms on the woofer, and 52uF on the tweet.

Also, I know I could put the woofers closer to the tweet but this is XPS foam and I was afraid it would weaken the baffle too much. When I'll do them in wood, they will be closer.

Just played a bit of music, I need to let the drivers break in a bit... but that SB65 is very nice! Loads of details. And the woofers are nice and tight in this sealed enclosure.

This looks like it might not need much tweaking but I'll still play with the box shape, and probably make a second one at 40 litres to compare.

Measurements will come soon.
 

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This has me wanting to try my own WAW build for my first project (in addition to the others that I'm pondering)... Seeing stuff like this makes it tough. I dunno which of my ideas to finally pull the trigger on!

The oval woofers are definitely cool. Love the close CTC ability. Has that old school look to em without being unobtanium.
 
I was listening to them this morning, and I just couldn't wait to get initial findings!

So, after only 8 hours break in, here's what it looks like.

X, yes, this is the simple 1st order XO with a 52uF cap and a 4.8mH inductor with 3 Ohms attenuation.

In order, first we have the horizontal measurements at 0, 15, 30 and 45 degrees.

Then, it's the vertical measurements at 0, 15, 30 and 45 degrees.

Group delay from a sealed box, so that's good enough.

4th is the distortion. I was not expecting much... remember this is a XPS foam glued together in half a day, it's got some bracing but I think I can forget anything under 200Hz. 1st and 2nd harmonics are 30 to 45dBs lower, and then a drop at the 3rd.

Finally, the impulse and Step. We can see the SB65 (inverted) arriving much ahead of the woofers. Surprisingly, there's quite a lot of small wobbles from the SB65 all the way to 1ms.

Next step is to make a smaller box and move the SB65 back. I'm not sure how I will do that, as the frame is very thin, and there's not much space between it and roll. Mounting it behind the baffle might prove to be a challenge. I might try with the woofers angled in on the baffle, a little like the Usher CP-777.
 

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