are DIY SDA 2Bs possible?

jaysmackie

I'm in Norway, little chance of finding SDA 2Bs here, and the freight will be more than the shipping from virtually anywhere.
Is it feasible to get all the drivers, crossovers from polk and make the cabnet?
Would solve the problem of finding a pair and cut down on the weight of those big cabinets. Even with buying all the replacement parts I think it would cancel out cabinet freight.

I would probably build straight to 2BTLs with the 198 tweeters.

OK, so a build from components may be a little fanatical but I want my 2Bs.

strider

Mids and tweeters you can get, don't think the PR is available. There are schematics for the crossovers at the top of this forum as a sticky. Everything else you could source on your own from wherever's more feasible. Might be quite an undertaking, but I know I love mine!

Face

You'll have to watch Ebay for the PR's.

jaysmackie

Yeah, it would be a bit of an adventure, earn a stash of polkie points tho
I'll keep an eye out for the PRs or the SDAs, see what happens first. There is a pair on ebay at the moment, does not say if they are sw120, 121 or 122, i'll try to find out.

edit : I'm guessing sw120 tho, they are being sold by somebody also selling mw6500s, assuming they are from the same polks, the only 12" PR teamed up with them was in rta12a/b i think

zingo

It would be doable, but tons of work as stated above. I feel the hardest part would be the cabs in you can find the PRs. I would give you about a million Polk/brownie points if you did though.

schwarcw

I think it might be possible to build them better than the original Polks. You could make the cabinet stronger, thicker wood, better joints and sealant, build a "point to point" crossover, use top notch crossover components, pick a real nice wood veneer, but the RDO-198 tweeter, wire the crossover to be the 4.1TL configuration, buy the drivers from Polk. Polk is not the only passive radiator out there. Look for similiarly sized passive raditators. I suspect Ken Swauger at Pok would even give you some tips on what to look for in a passive radiator.

Go for it!

schwarcw

For a passive radiator from Parts Express, look Here

ben62670

I have some PR's for you fairly cheap. I have also built some SDA's. If you need help shoot me a PM. I've done them from the ground up So no worries.
Ben

I did these little ones
http://www.polkaudio.com/forums/showthread.php?t=54554
And these big big ones
http://www.polkaudio.com/forums/showpost.php?p=656106&postcount=167

jaysmackie

thanks guys great stuff. I had been thinking polk drivers to make sure the cabinet worked well. but dimensions are not so critical with sealed boxes as long as it keeps the PR happy, gives me options. Maybe I can put a 15" PR in custom 2Bs and size the cabinet based on thaT. Will look at the morel gear for sure.
I'll lets this rumble about the head for a while and see what falls out. I am a woodworker, so building the actual boxes was the least of my worries, just what the sound would be like.

dcmeigs

jaysmackie wrote: »

thanks guys great stuff. I had been thinking polk drivers to make sure the cabinet worked well. but dimensions are not so critical with sealed boxes as long as it keeps the PR happy, gives me options. Maybe I can put a 15" PR in custom 2Bs and size the cabinet based on thaT. Will look at the morel gear for sure.
I'll lets this rumble about the head for a while and see what falls out. I am a woodworker, so building the actual boxes was the least of my worries, just what the sound would be like.

Go for it. It's a very senseable idea. When I hear people complain that the SDAs are out of production, I wonder why they don't do what you propose. I'll have my SDA 2B cabinets open next week for the crossover mod. If you want some cabinet pics, let me know.

ben62670

Stick with a 12. The 15 would be too big for just 2 MW's.

jaysmackie

I started thinking that about the 15 on the way to work too, actually wandered the other way 2 x 10" tuned differently to flaten the bottom response right out. I'll work out a few options and mail the polk gurus, see what they think.
The single tweet 1Cs had not occurred to me, a 1C configured in a single column of drivers could have a nice shape to it, especially with 10" PRs. Not too tall. Boy am I going to be distracted at work today.
This is going to take me quite a while but the mad frenzy of planning at the start is fun.

heiney9

With all due respect to Ben and his homemade SDA's there are some real critical measurements in the baffle that I'm sure are proprietary. I know Ben talked with Ken quite a bit and was given good guidance. I'm sure his SDA's are close.

Speaking personally and only my opinion but I'd stick to a production model SDA and build that as closely as possible using ALL Polk drivers. Don't try to add more cabinet volume or larger PR's, multiple PR's changing the position of the drivers etc, etc.

However, Ben is your man and his SDA's are cool but if I were doing it and they were going to be my only pair of SDA's, I'd copy the manufacturer's spec'd model as closely as possible. The critical part is the angle of the reg. and dimensional drivers in the baffle as well as the distance between the reg. and dimensional drivers in the baffle. 2B's are a good choice because they only have 3 drivers and sound excellent.

Good luck; getting the proprietary info and constructing the cabinets and finding x-overs will be the hardest part. I'd hate to see you buy a perfectly good pair of SDA's and then ask the seller to part it out and send you the parts. It would be a shame.

H9

jaysmackie

I would not pull SDAs apart for it, if a pair came up in europe I would galdly take the real thing. A DIY build is a backup plan to start working out while I have a favourable WAF level, in case it started to turn before a pair come up for sale. Then I can get everything but PRs from polk and build before the WAF is lost

The 2Bs were my first thought because they looked the most manageable to rebuild to spec, but Ben does look to have had success with other options, so that was good news to me.
The crossovers are not a problem, quite confortable building from the schematics.
There is no real need to change the shape of things, a 16" cabinet is not really that wide anyway, I'm just playing what if games to fill in a slow friday.

dcmeigs

heiney9 wrote: »

I'd hate to see you buy a perfectly good pair of SDA's and then ask the seller to part it out and send you the parts. It would be a shame.

H9

I think parting out a US set could be an act of mercy, if you find the right pair: http://www.polkaudio.com/forums/showthread.php?t=66163

And I agree with exact duplication of cabinet details and components. Why reinvent the wheel?

Face

Those are 2A's. I don't know if there are any driver differences, but with a different crossover, they could be made into 2B's.

Boywonder

As H9 mentioned above, if you want the SDA effect, (that's the whole point, I assume) you need the mids side-by-side, so a "single column" cabinet won't get you there. You need the proper horizontal spacing for the mids, which is essentially right next to each other for the 6 1/2" drivers (for the non-SRS SDA's).

Thinking outside of the box for a moment, has anyone considered modifying RTA-12's, monitor 12's, etc into SDA's? Obviously a major crossover rework, and a giant assumption that the cabinet volume would still be correct using one (or more mids) as dimensional drivers. Perhaps converting monitor 10's into "mini-SDA's" One more problem, driver impedance....different driver P/N's etc. OK it's friday and I've been awake for less than an hour....Just start with SDA's or SDA components, it will be much less painful.

If you use a non-Polk Passive Radiator you will also need to spend time tuning it close to Polk specs by adding weight and measuring response, etc. The Loudspeaker Design Cookbook by Vance Dickason is a good reference.

dkg999

I would just watch eBay for the proper SDA version parts, they come up for sale pretty regularly. I'm sure someone on this forum could help you out with cabinet dimensions and internal cabinet details for the version you are building.

FYI - I have 3 DIY sets of drivers/cross-overs for the SRS's, along with one cabinet set good enough to provide dimensions. I have the driver face plate already programmed on my CNC router. Someday I'll get time to finish the project!

dcmeigs

Face wrote: »

Those are 2A's. I don't know if there are any driver differences, but with a different crossover, they could be made into 2B's.

These are 2As but I'm sure some road rash 2Bs will come along if you are patient. The 2Bs have MW6503 and MW6511. These 2As will have MW6510s. Different crossovers too. Won't do at all.

I have both sets and the 2B is my favorite, no question.

schwarcw

heiney9 wrote: »

With all due respect to Ben and his homemade SDA's there are some real critical measurements in the baffle that I'm sure are proprietary. I know Ben talked with Ken quite a bit and was given good guidance. I'm sure his SDA's are close.

H9, etal

I think the only "critical dimentions" are the box geometry and internal volume. No nuclear science here. Ben had a whold different set of challenges.

There's not to much in the way of "high brow" baffling if your simply cloning. Do the internal measurements, make note of the baffles, but I would use some 13 ply birch plywood (3/4"), dowell pins, good wood glue, some nice veneer, upgraded inductors, caps, resistors, no polyswitches, point to point wiring on a flat board for the crossover. You may consider silver wire for the tweeter circuit on the crossover. What I'm not sure about is whether or not I'd add any dampeining material to the sides or bottom of the inside of the cabinet.

Good luck and have fun!