Possible 3 Way Build - Akai SW-130 Resurrection

Hello All:

I apparently had an account here the last time I was building a crossover from scratch. Maybe almost 20 years ago. ???.

Anyway, I am back and have a new project going in the garage. My son had a pair of Pioneer CS-88 (???) Frankenspeakers that I built for him when he went away to school. These cabinets were plywood construction with nice veneer and those lattice bamboo grills. Oiled and polished, a really nice vintage look. The guts were essentially Cerwin Vega! 10 inch three-ways taken from donors. These speakers got destroyed by water damage when his apartment caught fire. He is getting a larger place now, and wants to put his vintage system back together. So, I have a project in the garage.

I have Akai SW-130s kicking around for no purpose. I only saved them because they are MIJ and the cabinet materials and construction are pretty good. If they come apart reasonably, the sound board can be replaced with non-metric plywood, and the veneer restores well I will use them. Yes, they came apart cleanly and the sound board is easily, but meticulously, replaced. The veneer is looking good.

Disassembly pics...

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Looking to do a 3-way with planar tweeters and soft dome mids. My son hates Vandersteen, but loves Infinity with EMIT tweeters. He likes bright and detailed. He likes my daughter's Infinity Crescendo C3007. (???) With the EMIT.

I am thinking...

Hi-Vi RT1C_A tweeter. PE part number 297-400. Use a high crossover.

Hi-Vi DMB_A soft dome mid-tweeter. PE part number 297-716. Use a wide range with this driver, which should sound great.

Dayton Reference 8.00 woofer RS225. 8 Ohm. PE part number 295-356. ???.

Crossover would start out as a generic 3-way import. I have found a 600 Hz / 4000 Hz and a 850 Hz / 5800 or 6000 Hz. I think the latter would better suit the soft dome "mid" response and allow the higher crossover to minimize any lower-end peaks in the tweeter. From there, mods could be made.

I am concerned that the SPL of the woofer is so much lower than the mid or tweeter, being 86.8 versus 92.0 and 94, respectively. Am I headed for disaster this way? High efficiency would be great, but that woofer is not very sensitive. How would this play out in reality?

There may be an option to use (2) 6.00 woofers, 4 Ohm, in series. The 4 Ohm coil has a sensitivity of 91.8 each. In series, would these present an "8 Ohm" load and preserve this higher SPL? If so, does that not solve a very significant problem?

Dayton Reference 6.00 woofer RS150-4. PE part number 295-372.

Either layout will fit the soundboard. As far as the enclosure volume for a sealed system, the calcs for the 8.00 or the (2) 6.00 woofers looked okay to my limited-experience eyes.

Thoughts? Ideas? Opinions? Hesitations? Run away?

Thanks in advance. I will try to post some data sheets next.

jocko
 
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First of all. have you listened to the Akai drivers? They might sound pretty nice... They certainly look good to me. If you don't use them, you could probably sell them to somebody if they are in good condition. Or, the Hi-Vi tweeter might match up nicely with the original alnico low freq driver.

You might consider a more efficient low frequency driver. An Eminence Alpha-8A or Beta-8A would match up nicely. They trade some low frequency range for higher sensitivity. There are tradeoffs everywhere, it all begins with your intended system design.

It is pretty common for high freq drivers to be more efficient than the low freq drivers. The low frequency driver frequently dictates the overall sensitivity of the system. If baffle step filters are used to boost the bass, then efficiency drops another 3 to 6 db. People often add padding resistors of appropriate wattage ratings in series with the midrange and tweeter drivers. Or use L-pads, they can adjusted to suit the room acoustics and musical preferences.
 
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The original drivers look to be in fine shape; intact and free moving. I could check continuity. I have not tested them, nor have I heard the speakers. 12.00 two-way with paper cones. I would not hold out much hope that they are more than one would expect. I would keep the drivers in case someone wants them. However, it seems that type of stuff just sits in the closet. Generally not worth the trouble and cost of shipping.

Another forum thought the woofers were by Coral based on the appearance and markings. Akai was too small a company to make their own.
 
12.00 two-way with paper cones. I would not hold out much hope that they are more than one would expect.
I guess since my current favorite speakers are 12" two ways with paper cones, that might explain the reason behind my suggestion. I do listen primarily to acoustic music however, they may not be ideal for rocking out to popular music with electronically amplified bass.

If they are Coral, I do believe that they made some very nice drivers. I would highly suggest keeping all of the original parts. I regret throwing away some paper cone tweeters from some nice older speakers because I assumed that they would sound terrible (only because they were not domes) The alnico woofers turned out to be excellent and now I have lost the matching tweeters.
 
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I definitely save stuff... To a fault. They will be free to a good home. I am in western NC. If there is an interest, I will post these and some other free stuff in the Marketplace. New to this site, at least new to what it has evolved into.

I still have the lattice grilles for Pioneer CS-88a. Very nice condition. Someone just might need those. Probably the drivers as well, but the grilles are the important part.
 
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Can anyone definitively say what the SPL of two 4 Ohm woofers combined in series would be? I searched and the answer seems to be 91.8 dB of the single, but now at 8 Ohm. - 3dB (one half), but times two. That makes sense from a conservation of energy point of view.

I guess same would apply to two 8 Ohm in parallel, but a lower impedance load.
 
Two four ohm drivers wired in series would have the same SPL as one 4 ohm driver. You get a 3 db boost from the doubling of cone area, but then lose 3 db in voltage sensitivity by going from 4 ohms to 8 ohms (voltage is same, current is half).

I sent you a message about the Akai drivers...
 
I am taking a different approach now... Lesson learned years ago restoring a pair of Infinity Quantum. Don't get too far ahead with the "fun" stuff, like the drivers and sound boards, until you have a handle on what the grilles will require. The last step that can be a real doozy if you don't have things figured out in advance. Don't think you can put the grilles off until the end. They are probably the most difficult part of the build.

In this case, the original drivers mount from the rear. I will be mounting them flush from the front. Not gonna happen they way these cabinets were constructed. I have got to have access from the front via a removable grille. This will require careful woodworking. I am only going to order parts once I have the grilles figured out and successfully executed. I no not want to get to the end and discover these cabinets ultimately will not work.
 
The grille cloth has faded to a completely different color.

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These are the "Tee Screws" they used in Japan at the time. Never seen that one before. Two of them stripped during removal of their nuts. No surprise. They are just machine screws deformed with a tool.

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These bezels are NOT anodized aluminum. Solid color through the saw cuts, and too heavy. They are solid brass.

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Here is how the brass trim fits into the cabinet. I will have to create removable grille frames to fit these dimensions. All the pieces will need to be ripped to size, since none of these materials are normal dimensions. Check out the pencil line and the nail. Amazing.

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These speakers have been full of surprises. Never encountered anything like them.

The original grilles were a snug fit to the cabinet. The whole assembly then fastened from the rear. The dimensions for the soundboard had to be precisely sized so that the 45s on the brass trim fit nicely, while still fastening to the soundboard securely, including room for the grille cloth and about 200 staples. There were wood shims to lift the brass trim away from the cloth and staples, for a more stable and quieter fit. A lot of effort to go through for a factory built.
 
when you say soundboard are you talking about a baffle ? so the drivers were rear mounted then the baffle wrapped in material then the shims then the brass trim nailed around the baffle then whole thing pulled back from the inside by the machine screws ? you're right they went to a lot of effort but I like the style of some of these older speakers and it's becoming fashionable again I just worry about diffraction I think some angled felt all around the edge might help with that maybe ?
 
Yes. Baffle. Motor board. Sound board. I have working on guitars too much the past years.

I have to wrap my head around these. 3/4 plywood and 3/4 MDF is not a natural fit. Felt would probably be smart. Maybe cut a radius on any 90 degree edges.

I am probably going to have to cut these grille boards out of a sheet of MDF with a router, so that I can get a radius in the corners where a joint would otherwise be. Maybe I can reinforce the joint somehow using standard saws. I am allowing basically 1.00 inch for the grille frame to impact the baffle. It gets tight.

I agree about becoming fashionable again. Both my kids dig the mid-century modern thing. A broad definition that includes old style, but only before everything went plastic in the 70s.
 
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