diy CAOW1 speaker cabinet question

[louis2001]

I am a complete newbie, and have decided I want to build myself some speakers. I thought I would start with the CAOW1 by Dennis Murphy.

I have searched, but have not found any documented builds. I did find nice documentation of the related MB27 speaker as built by "Swerd", but this using a prefab cabinet.

For those familiar with this cabinet:

1) I am unsure of what to do with the holes in the rear panel. Are they simply routed holes? Should they be rounded? Do I have to put a port tube in it? What is meant by the two separate diameters of the inferior hole?

2) If I increase the height of the cabinet, as suggested on Dennis Murphy's website, I need to add more wood inside to keep the volume the same, right?

Thanks,

Zoltan

 

[Swerd]

Zoltan

Welcome to AH! I readily recommend the CAOW1s, they are excellent speakers.

I did build a pair of CAOW1s a few years ago, but never took pictures. I might have notes left over from building the crossover, I'll look tonight.

I suggest you contact Dennis Murphy by email (see his DIY website) because he may have a revised crossover for this speaker, using the SEAS ER15 driver instead of the CA15.

As you have noted, the MB27 speaker and the CAOW1 can use the same cabinet. You could certainly use the same pre-made cabinets from Parts Express. I would recommend using the straight-sided cabinets instead of the curved-sided ones because getting the crossover parts to fit inside will be easier.

1) I am unsure of what to do with the holes in the rear panel. Are they simply routed holes? Should they be rounded? Do I have to put a port tube in it? What is meant by the two separate diameters of the inferior hole?

The upper hole behind the tweeter is for the port tube. A 1¾"×4" tube from Parts Express (part 260-407) is the right size for you. It will fit into a 2" diameter hole and is just the right length.

The lower hole is for a terminal cup. That picture is only an illustration, I don't know if it is the correct size to fit the hole in the diagram. You can omit this and use terminals such as these.

2) If I increase the height of the cabinet, as suggested on Dennis Murphy's website, I need to add more wood inside to keep the volume the same, right?

The increased height of the cabinet is to allow for a drawer (about 4" tall) below the interior of the cabinet that could hold the crossover. It would be a separate chamber from the rest of the cabinet interior. I never built that.

The important dimensions are the cabinet volume, the front baffle width, and the locations of the woofer & tweeter on the front baffle. The port tube may be located in a number of positions, but the easiest location is directly behind the tweeter.

Take pictures & Good luck.

 

[louis2001]

Thanks for your quick response and great suggestions. I can't wait to get started. My ultimate goal is to build the ER18 MTM, so the CAOW1 will be good practice. I have been studying several of the great ER18 MTM builds on this forum.

Zoltan

I suggest you contact Dennis Murphy by email (see his DIY website) because he may have a revised crossover for this speaker, using the SEAS ER15 driver instead of the CA15.

Good idea. I'll see what he says. Otherwise, I'm close to finalizing my parts list. I even contacted Solen Electronics and they are making me a 0.06 uH Inductor! This will be great since both the CAOW1 and ER18 MTM call for this part. I wasn't keen on removing coils from a 0.1 uH inductor.

Zoltan

The upper hole behind the tweeter is for the port tube. A 1¾"×4" tube from Parts Express is the right size for you. It will fit into a 2" diameter hole and is just the right length.

Thanks! I don't think I would have ever noticed the port tube listed under parts list for the mbow1 speaker!

Zoltan

The increased height of the cabinet is to allow for a drawer (about 4" tall) below the interior of the cabinet that could hold the crossover. It would be a separate chamber from the rest of the cabinet interior. I never built that.

This sounds simple. All I'll need are a few tiny holes for the wires to pass through to the drivers.

 

[Swerd]

Good idea. I'll see what he says. Otherwise, I'm close to finalizing my parts list. I even contacted Solen Electronics and they are making me a 0.06 uH Inductor! This will be great since both the CAOW1 and ER18 MTM call for this part. I wasn't keen on removing coils from a 0.1 uH inductor.

If you wish, you can get an LCR meter, such as one like this. Then you can unwind wire from a 0.1 mH inductor, measure the inductance, and when you've unwound enough to get 0.06 mH, cut the excess wire. However, I don't know what it would cost to get a supplier to make the inductor for you, it may be cheaper.

This sounds simple. All I'll need are a few tiny holes for the wires to pass through to the drivers.

It depends on how familiar you are with wood work. I found it much simpler to mount the parts on pegboard, pass it through the woofer hole, and screw it to the cabinet floor.

 

[louis2001]

If you wish, you can get an LCR meter, Then you can unwind wire from a 0.1 mH inductor, measure the inductance, and when you've unwound enough to get 0.06 mH, cut the excess wire. However, I don't know what it would cost to get a supplier to make the inductor for you, it may be cheaper.
It depends on how familiar you are with wood work. I found it much simpler to mount the parts on pegboard, pass it through the woofer hole, and screw it to the cabinet floor.

I didn't know there was such a meter as that. The cost for the inductor is $3, they just have to make it since it isn't stocked as a standard size.

Zoltan
I found it much simpler to mount the parts on pegboard, pass it through the woofer hole, and screw it to the cabinet floor.

I was just concerned since Dennis recommended the approach of adding this compartment since it's difficult to squeeze all the parts in. Did you build the cabinet? If so, sounds like you don't think space was too much of a problem.

Also, I thought I thought I would put Black Hole 5 damping material. Would I put it this only the side, top, and maybe on the exposed back?

 

[Swerd]

I was just concerned since Dennis recommended the approach of adding this compartment since it's difficult to squeeze all the parts in. Did you build the cabinet? If so, sounds like you don't think space was too much of a problem.

Yes I built the cabinets, twice . I badly messed up the veneer on my first try.

The cabinet I built had the standard dimensions. There was no removable front baffle, no interior bracing, and no crossover drawer. I cut the largest size pegboard that could both fit in through the woofer hole and lie flat on the inside cabinet bottom. I then arranged the crossover parts on the board using cable ties and no glue or solder until I was sure the board with components fit in through the woofer hole. Be sure to include the 3 pairs of wires for the rear terminals, woofer, & tweeter.

I was able to get all components for both woofer & tweeter circuits on one board and got it to fit in the cabinet without much trouble. After I was certain things actually fit, I soldered the connections.

After the crossover board was screwed to the cabinet bottom, then I installed the port tube and foam lining, and finally the woofer & tweeter.

Do not forget (as I did) to wire the tweeter's negative terminal to the positive side of the crossover network. The 2nd order crossover requires that. This is the same as I showed with the MB27 built thread.

If I find a list of parts I used, I can post it. Are you in Canada? You mentioned getting parts from Solen. If so, the parts they carry may be different from those I got from Parts Express and Madisound.

Also, I thought I thought I would put Black Hole 5 damping material. Would I put it this only the side, top, and maybe on the exposed back?

Yes, put any damping material on at least one side of opposite walls, such as one wall, the top, and the back. With expensive stuff, like Black Hole, that becomes more important than with less expensive stuff like convoluted foam, which is what I used.

 

[louis2001]

I was able to get all components for both woofer & tweeter circuits on one board and got it to fit in the cabinet without much trouble. After I was certain things actually fit, I soldered the connections.

After the crossover board was screwed to the cabinet bottom, then I installed the port tube and foam lining, and finally the woofer & tweeter.

Do not forget (as I did) to wire the tweeter's negative terminal to the positive side of the crossover network. The 2nd order crossover requires that. This is the same as I showed with the MB27 built thread.

I think I'll build the cabinet as you did. I haven't yet researched the techniques for building the crossover, but will refer to your mb27 pics as well as do additional research.

If I find a list of parts I used, I can post it. Are you in Canada? You mentioned getting parts from Solen. If so, the parts they carry may be different from those I got from Parts Express and Madisound.

I'm in St. Louis MO. Most of the parts are carried by Parts Express. The CAOW1 design didn't specify inductor awg, so I just picked what Parts Express had available (2 in 18 awg and 1 in 15 awg). Similarly, Solen is making the .06 mH in 18 awg.

 

[Swerd]

I think I'll build the cabinet as you did. I haven't yet researched the techniques for building the crossover, but will refer to your mb27 pics as well as do additional research.

Remember, you can place capacitors and resistors anywhere they fit, but inductor coils should be located so as not to interfere with each other. See the diagram at the bottom of this link. I always try to get coils arranged as in #6 or #7.

I'm in St. Louis MO. Most of the parts are carried by Parts Express. The CAOW1 design didn't specify inductor awg, so I just picked what Parts Express had available (2 in 18 awg and 1 in 15 awg). Similarly, Solen is making the .06 mH in 18 awg.

That ought to be fine.

If you are interested in the parts list that I used, send me an email address by PM and I can forward that to you.

 

[louis2001]

Thanks. That's a very helpful diagram.