Building Your First DIY Speaker - The MB27

[STRONGBADF1]

This was the best write up I've seen on these boards. Great job Swerd!



BTW, don't forget to place a dead trout in them... you know, as a "damping material".

 

[slipperybidness]

That's my favorite picture too.

I wish I had a photo of three 1.0 mH inductors, 14 g, 16 g, and 18 g side by side. The size difference is large. So is the price .

I think the photos imply this, but I'll say it outright. Getting these crossovers to fit inside the curved cabinets was very difficult for me. I only took a picture when I finally got it all in. Notice that nothing was soldered in that photo, as I was still rearranging parts. And none of the photos show the blood from the scraped knuckles I got during the trial & error fit process. Both cabinets got some blood on them, so they are still a matched stereo pair .

I would strongly advise anyone who wants to build one of these speakers to switch to the pre-made rectangular cabinet (it has more useable space inside) or use 18 g wire inductors instead of 16 g.

Yes, the greater DC resistance of 18 g coils will generate more insertion loss, but nothing is worse for sound quality than crossover boards that won't fit in a cabinet !

That's also part of what's so nice about large floorstanding speakers. There is lots of available space for the crossover board.

If I remember correctly, and these are the same ones I'm thinking I read about on the murphyblaster site, then DM says if you buy the pre-made cabs from his cab guy, then they are a couple inches taller than the plans indicate, with a compartment at the bottom for the crossovers. He gives fair warning from the beginning

 

[mattsk8]

Very nice write up!! Nice job on the cabinets as well! I've heard you mention using a morticing bit for your recesses, but couldn't wrap my mind around it for whatever reason. I've been using a 3/4" dado bit; looks like now I'm going shopping ! Nice router BTW too! I have the same and would argue it being if not the best, definitely one of the best plunge routers available.

I'm not sure if I missed it, but I'm guessing these are a rear port? If so, can you put pics of the backs? And, would it change anything (aside from potential chuffing) to do a front port?

Also, how would these work in an HT situation? Is there a center you would recommend using? And a sub?

 

[Swerd]

Very nice write up!! Nice job on the cabinets as well! I've heard you mention using a morticing bit for your recesses, but couldn't wrap my mind around it for whatever reason. I've been using a 3/4" dado bit; looks like now I'm going shopping ! Nice router BTW too! I have the same and would argue it being if not the best, definitely one of the best plunge routers available.

I'm glad to hear those pictures of the tweeter recess made sense to you.

The only reason I got a 1¼" bit is because the Jasper jig holes are marked assuming you use a ¼" bit. With a 1¼" bit its easy to do the arithmetic in my head: find the diameter mark on the jig that I want, and subtract 1 from it. And I had no other bit that had bottom cutting edges. Your ¾" dado bit should work if it has cutting edges on the bottom as well as the sides.

Yes, I like my DeWalt 621. I was given some good advice by another DIY speaker builder who said "save yourself some grief and money and never buy cheap tools." There are other good plunge routers (Bosch and Hitachi for example) but I've never had them in my hands.

I'm not sure if I missed it, but I'm guessing these are a rear port? If so, can you put pics of the backs? And, would it change anything (aside from potential chuffing) to do a front port?

I cut a 2" diameter hole in the back, directly behind the tweeter. I used shelf paper just like on the fronts to protect the finish. It was so simple that I forgot to take a picture of that. I used Parts Express port tubes that are 1¾" × 4" and don't need any trimming. I used 100% silicone sealant under the lip to seal the edge of the hole.

Also, how would these work in an HT situation? Is there a center you would recommend using? And a sub?

Always with the center speaker questions . I don't know of a specific design, but there ought to be plenty of decent options around.

The MB27 goes down to about 55 Hz. There ought to a number of suitable subwoofers that can mate with that.

More related to the ER18 MTM speakers, if you or someone else builds a cabinet for a sideways MTM for ER18s and your tweeter of choice, and send it to Dennis Murphy, he will come up with a crossover for it.

 

[TheWarrior]

Great write up! Thank you!

I am hoping to dive in to speaker building this winter, once I get some house projects handled. Aside from the endless hours of cabinet construction, I now know how detailed I need to be if I want to share the experience on the interweb.

Totally fascinated by crossover design! I think I'll ask Madisound to only assemble one of the crossovers for the ZRT so I can practice against the work of a pro.

So are you happy with the sound?

 

[slipperybidness]

What do you think the total man-hours were on this build?

 

[Swerd]

Totally fascinated by crossover design! I think I'll ask Madisound to only assemble one of the crossovers for the ZRT so I can practice against the work of a pro.

The most important thing is having the crossover parts in your hands and knowing how much space is available inside the cabinet.

If your cabinet already has the front baffle glued on, then the term "available space" is limited by what you can pass through the woofer hole.

There are some standard "rules of thumb" at this web page (scroll down to the bottom), about how to arrange inductor coils so their magnetic fields don't interfere too much with each other. I probably pushed those standard rules of thumb a bit for the MB27 .

Resistors & capacitors can go just about anywhere.

I practice arranging the crossover parts on a piece of paper cut to the size of the board. Then I cut a board and drill holes for cable ties to attach the parts to the board. If I don't like an arrangement, I can easily cut the cable ties and try again. Don't bother with using glue.

So are you happy with the sound?

Yes, they sound nicely balanced and smooth across the entire mid range. I think the fancy audiophile words are coherent and focused .

What do you think the total man-hours were on this build?

LOL Somewhere between 10 and 100 hours give or take a whole bunch!

 

[Alex2507]

The woofer board, with 1 small and 2 large inductor coils, was more difficult.

I was looking at all the winds on the tweeter board connections thinking 'what a pain' and then I read the above quote. More difficult ?!? Ugh ...

Both cabinets got some blood on them, so they are still a matched stereo pair .

Hilarious !!! I would have settled for like discreetly placed initials but blood works and for me the blood was worth it. Having the shop finished curved cabinets is on a different plane of existence. Your hands are probably already all healed up.

I had only ever heard about one other MB27 at a DIY meet. Apparently it held it's own in that environment and that's really not so easy to do.

 

[Swerd]

I was looking at all the winds on the tweeter board connections thinking 'what a pain' and then I read the above quote. More difficult ?!? Ugh ...

I meant that getting a workable layout for the tweeter board was simple. With enough space between parts, connecting the wires is not difficult with my average sized hands.

As for making the connections, I used to twist wires together. If both wires were of similar thickness, as in resistors or caps, that usually worked OK. The thicker solid wire of the inductor coils was difficult to twist with the smaller wires. That's what led me to wind one wire around the other. It holds together better and looks better. After you solder you can't see it so well.

Hilarious !!! I would have settled for like discreetly placed initials but blood works and for me the blood was worth it. Having the shop finished curved cabinets is on a different plane of existence. Your hands are probably already all healed up.

I should have left bloody initials on the inside. Too bad I didn't think of that. There wasn't enough blood to write anything more clever.

I had only ever heard about one other MB27 at a DIY meet. Apparently it held it's own in that environment and that's really not so easy to do.

I've been listening to them on and off this week and still like them. When I have more time, I'll do a direct comparison between the CAOW1 and the MB27. I already know the MB27 is a little less sensitive and has less bass than the CAOW1, but they sound good anyway.

The amp driving them is an old B&K ST140 with 100 wpc.

I was looking at the grills that came with the cabinet and could see where the outer rim of the woofers hit the inside of the grill frame. My daughter tells me she left her Dremel tool in the basement. If I find it, do you want me to try and work on the grills to try to get them to fit? I think some washers behind the front baffle bolts plus a little Dremel work should do the trick.

 

[Alex2507]

... do you want me to try and work on the grills to try to get them to fit?

Yes, please. Nothing would make me happier.

I've got an entertainment center to finish up. Later. Thanks.

 

[Swerd]

Today I spent some time listening to the MB27s and directly compared them with my CAOW1s. I had initially thought I would be able to hear differences between these speakers, that the MB27s would be less sensitive and have less bass, but I was wrong. They aren't identical, but they are so close on most musical passages that I had trouble telling the difference.

I listened to various tracks from these CDs:

Dire Straits – Brothers In Arms
David Grisman – Hot Dawg
Paul Simon – Graceland
Harry Nilsson – Son of Schmilsson
​

The short version is that I like the MB27s a lot, just about as much as I like my CAOW1s. Considering the price difference, the MB27s are excellent.

Please note that I did not check how loud the MB27s could get without sounding compressed or distorted. And I did not listen while significantly off axis. It may be that differences between them and the CAOW1s could be heard, but I was happy with their generously wide sweet spot and overall volume level. The amp I used was an old B&K ST140, 105 wpc, and the listening room was large, roughly 14'×19' with a 9' high coffered ceiling. That room has rather good sounding acoustics.

Both speakers have essentially the same sensitivity. I compared by ear using the same musical passage, switching the speakers without changing the volume settings. They were close enough that it wasn't worth getting my SPL meter.

Bass depth was similar sounding on both speakers with the music I chose. On Hot Dawg, there was an un-amplified upright string bass that I thought sounded ever so slightly weaker on the MB27. But it was close to the sound on the CAOW1, and was definitely not dissatisfying.

Both speakers sound very good with percussion, reproducing the impact from bass to upper midrange / lower treble that makes for good percussion sound. Graceland is a good CD for this.

As for voices and midrange in general, what can I say? These speakers share the same sound that all of Dennis Murphy's speakers have. Those who have heard Salks or Philharmonics will nod in smiling agreement – while those who haven't heard them will think "there goes that fanboy talk again".

My final comments are that the MB27 is an excellent small bookshelf speaker that can be owned for a rather modest price combined with some of your own labor and effort.

 

[mattsk8]

We need pics of the finished product

Or is that it on page one?? Thought that was a pic of someone else's

 

[Adam]

We need pics of the finished product

I thought the pic in the first post was of the finished speaker.

EDIT: You post editor, you.

 

[Swerd]

We need pics of the finished product

Or is that it on page one?? Thought that was a pic of someone else's

Adam is right. The picture on page 1 is one of the finished MB27s that I built.

 

[Alex2507]

We need pics of the finished product

Or is that it on page one?? Thought that was a pic of someone else's

Technically it's both ... the one he built and someone else's.
Forgive me for gloating. Really ... it's beneath me.

Seriously, I'm happy to hear that they're similar to the more expensive CAOW1s. I'm just waiting for word to drive south and pick 'em up. I know we're just about there time wise. I need to wrap up my entertainment center install before I leave though. Leaving my living room torn up like it is while I go get more gear ... surprise gear at that, would be the hammer.

 

[Adam]

Technically it's both ... the one he built and someone else's.
Forgive me for gloating. Really ... it's beneath me.

These are the speakers?! Man, I should have tried to snake those out from under you.

Very impressive build, Richard - and thanks for the explanation and photos! And, congrats, Alex. I know that you've been drooling over these for a while now.

 

[Alex2507]

These are the speakers?! Man, I should have tried to snake those out from under you.

... and I thought nothing slipped past you.

Very impressive build, Richard - and thanks for the explanation and photos! And, congrats, Alex. I know that you've been drooling over these for a while now.

Thanks, Adam. Swerd seems to be our new resident DIY guru. He's building a bookshelf version of the ER18 for dkane as well. I'm hoping for a few pic's and a listening impression of those as well. I know surprisingly few details but now that these MB27s are done I'm wondering what the cost is of Dan's speakers and what cabinet Swerd chose for that.

Store bought cabinets rule. I've heard maybe a dozen DIY designs and they all sounded good. Most of the cabinets were unfinished MDF. That tell you anything? I guess I'm like most. At first it's all about audio and then looks really start to count.

 

[Swerd]

He's building a bookshelf version of the ER18 for dkane as well. I'm hoping for a few pic's and a listening impression of those as well. I know surprisingly few details but now that these MB27s are done I'm wondering what the cost is of Dan's speakers and what cabinet Swerd chose for that.

I'm building those cabinets from MDF. Dan will get them unfinished – one of these days when I finally get them done. An unfinished cabinet plus drivers has to go to Dennis for his crossover design work. Then I can make the crossovers and get them to Dan.

Store bought cabinets rule. I've heard maybe a dozen DIY designs and they all sounded good. Most of the cabinets were unfinished MDF. That tell you anything? I guess I'm like most. At first it's all about audio and then looks really start to count.

It might be interesting to start a thread of all the sources of pre-made cabinets for DIY speaker builders.

Swerd seems to be our new resident DIY guru.

duly noted .

It's easier to be a big fish if the pond is small, like the DIY forum here. My goal is to get a few people interested enough to try it themselves. I'd be much less noticed at the PE Tech Talk forum.

My approach is simple. Follow the recipe for designs that are already known to be good. It's much harder to design your own and come up with a good result.

 

[Swerd]

Some one is certain to ask what is the sensitivity of the MB27?

The woofer, a M130 from GR Research, is the same woofer in the A/V series kits that GR Research sells. I just checked that web site, and the enclosure for the A/V-1 is 12" tall × 8" wide × 11.625" deep, with a reflex port tube that looks the same 1¾" diameter × 4" long. Not identical to the MB27, but almost the same. Certainly the interior volume is very close.

GR Research says the A/V-1 in that cabinet has an F3 of 55 Hz and a sensitivity of 86 dB. I think it's safe to assume the MB27 is the same.

This 8 ohm speaker is easy to drive, and GR Research recommends amplification from 5-100 watts.

 

[slipperybidness]

Yes, list of pre-made or at least knock-out cabinets would be awesome. That's my biggest hangup right now. I like the electronics work, but don't care for the woodworking. I don't have all the tools, it's messy, and it's too freaking hot for about 9 months of the year in TX to work in the garage.