Revel M105 Bookshelf Speaker Review

[AnalogSteph]

A certain level of sound needs to be reached for the modal effects of the room to stabilize - fancy way of saying room gain ain't there at low volumes.

That would make the room a rather nonlinear affair, and I don't see why this would be the case.

My bets would be on in-room FR + hearing sensitivity curves for now.

 

[Soniclife]

Does this work?

@amirm Did you see this?

 

[NoAudiophile]

That would make the room a rather nonlinear affair, and I don't see why this would be the case.

My bets would be on in-room FR + hearing sensitivity curves for now.

There is a good bit of research on this. If I remember correctly, the idea is that large sound waves in the modal range are absorbed at lower volume level(with things like couches and rugs), but quickly overcome that absorption as volume increases beyond the capacity of the absorbent material.

 

[Archsam]

I am now a very happy owner of the M105. Best sound I have ever heard in my own living room.

To all fellow M105 owners: what speaker stands do you use? I did not purchase the Revel M stands - I think the £300 price is a bit much. But the shape of the speaker being tapered is a bit tricky. Any suggestions?

 

[KaiserSoze]

I am now a very happy owner of the M105. Best sound I have ever heard in my own living room.

To all fellow M105 owners: what speaker stands do you use? I did not purchase the Revel M stands - I think the £300 price is a bit much. But the shape of the speaker being tapered is a bit tricky. Any suggestions?

Congratulations on your new purchase! (Assuming, of course, that you didn't buy the ugly white ones ... )

 

[Archsam]

Congratulations on your new purchase! (Assuming, of course, that you didn't buy the ugly white ones ... )

Yep I am now a proud owner of a pair of white M105!

 

[MediumRare]

I need a cutaway image of the M105 to figure out how I can mount mine. Anybody have a source for that? @maty , you're usually my hero of interior shots!

 

[Archsam]

So this morning I decided to go with a pair of Kanto SP stands:
https://www.kantoaudio.com/speaker-accessories/sp-series/

They look stylish, comes in white, can run the speaker cable inside the column, just about the right height for my listening position (will be even better if it's another 5cm, but I have also purchased some speaker spike shoes that will elevate the speaker by another inch), and the support plate (11x18cm) fits quite well within the footprint of the M105. Reasonably price at £109 on Amazon.

Bonus point for Kanto being a Canadian company

Let's see how good they are when they arrived.

 

[Spocko]

Maybe we can have all those youtube reviewers actually produce something useful and worthwhile for once and provide detailed specs. They may even be able to handle that task--but probably not that guy who I assume wants to have sex with cartoons.

Self-produced and uploaded videos of clueless self-anointed experts reviewing speakers using language that is tantamount to gibberish. The Internet is a wonderful thing.

To be fair, most written speaker reviews are done subjectively and without measurements, and I'd go so far as to say these reviewers romanticize the shortcomings of measuring badly in order to rationalize the absence of measurements. Herb Reichert of Stereophile recently commented during the review of the badly measuring Tannoy Revolution speaker "These speakers deliver a fundamental musical naturalness because of their flaws! Not in spite of them."
https://www.stereophile.com/content/tannoy-revolution-xt-6-loudspeaker

 

[KaiserSoze]

To be fair, most written speaker reviews are done subjectively and without measurements, and I'd go so far as to say these reviewers romanticize the shortcomings of measuring badly in order to rationalize the absence of measurements. Herb Reichert of Stereophile recently commented during the review of the badly measuring Tannoy Revolution speaker "These speakers deliver a fundamental musical naturalness because of their flaws! Not in spite of them."
https://www.stereophile.com/content/tannoy-revolution-xt-6-loudspeaker

Thanks for giving me a chuckle. And to be fair, the people who do the subjective gibberish-laden reviews in established print magazines are an anathema, however the Youtube reviewers can sometimes be annoying because of the preposterousness of some of the beliefs they expound. Like the guy who dismisses the importance of time coherence within the crossover region because he believes that owing to the existence of an overall rotation in phase from low to high frequency that it wouldn't make any difference whether the two interfacing drivers are time-coherent in the overlap. The guy obviously does not understand anything at all about crossovers; if he did he would understand about the need for the two drivers to maintain a consistent phase relationship in the crossover region and the implications of this need with respect to time coherency. But he's got a following on Youtube.

 

[KaiserSoze]

So this morning I decided to go with a pair of Kanto SP stands:
https://www.kantoaudio.com/speaker-accessories/sp-series/

They look stylish, comes in white, can run the speaker cable inside the column, just about the right height for my listening position (will be even better if it's another 5cm, but I have also purchased some speaker spike shoes that will elevate the speaker by another inch), and the support plate (11x18cm) fits quite well within the footprint of the M105. Reasonably price at £109 on Amazon.

Bonus point for Kanto being a Canadian company

Let's see how good they are when they arrived.

The speaker stands will definitely look better in white. And of course I was only kidding about the white speakers being ugly. Most all speaker stands look too industrial to my eye, but they can still look okay depending on the overall room decor. If they seem not quite in place with the rest of the room decor, the tall pipe can be wrapped with medium gray upholstery fabric, or with colorful upholstery fabric according to the flavor of the room. The upper surface of the flat plate at the bottom can be covered with a thin but attractive piece of finished wood cut precisely to fit. It won't look out of place since there is no exposed wood on the speaker or on the stand.

 

[Archsam]

Please let us know how they work out and if they feel stable. The 26" height does concern me as Revels aren't great with vertical dispersion. I must admit that one reason I went with the M16s over the M106s is because I really dislike the Performa3 and PerformaBe line stands and could not find a suitable alternative. Not only too expensive, but that stripe running down the middle is quite amateurish in design to me. The Concerta2 stands on the other hand are pretty slick and are quite stable.

Looks promising:

BTW I really thought it was Jack Black in this video

 

[KaiserSoze]

That's a particularly horrific "review" that shows that perhaps Mr. Reichert should consider retirement. It goes to my point that he is not providing anything of value here. And this is being generous! "Musical naturalness" because of their flaws? Does that mean anything? Does it matter what the product is, ultimately? I mean, let's take your field: Anyone trying to make a career out of subjectively discussing the perceived color gamut of a television today would be laughed out of a career. It's time this happened in the home audio realm.

Edit: I also want to add that I am a fan of your channel.

Some good observations there. You are right in saying that there is nothing of genuine value in that subjective review. And in that subjective review he made statements that can only be interpreted to mean that in his opinion a speaker must measure badly in order to sound good. He said as much in that strange comment that makes you try to figure out the difference between something occurring because of some phenomenon, as opposed to occurring in spite of the phenomenon. This was presented in a way that conveyed the sense of profoundness, but all I was able to glean from it was that he was saying that a speaker won't sound good unless it has flaws that gave it character. It kind of boggles the mind that someone would have the audacity or hubris or whatever to make this kind of a claim, yet it isn't so far removed from all manner of similar crap that this magazine have others have been spewing for decades.

Your comparison to measuring the color gamut of a television is also thought-provoking. There has to be an explanation for why everyone automatically knows that the color gamut of a video monitor needs to be carefully measured and expressed in precise quantitative terms, while most people do not automatically think of sound reproduction in a similar way. Most people prefer to rely on their perception. If they like the way a speaker sounds, that's all they need to know, and if they don't like the way a speaker sounds, that's all they need to know. Most people do not have any ability to look at a set of data or at a graph of any sort and discern from it anything meaningful about what a speaker is likely to sound like to them. For most people, subjective gibberish-laden reviews are more meaningful than quantitative measurements, which are not meaningful in the least to most people. We take a lot for granted, e.g., frequency response measurements both on and off axis, and the value of non-linear distortion measurements notwithstanding the fuzziness in their interpretation, etc., but the typical consumer understands none of this, because the typical consumer has no concept of what sort of numerical value would be assigned to any tone familiar to them.

 

[Archsam]

Please let us know how they work out and if they feel stable. The 26" height does concern me as Revels aren't great with vertical dispersion. I must admit that one reason I went with the M16s over the M106s is because I really dislike the Performa3 and PerformaBe line stands and could not find a suitable alternative. Not only too expensive, but that stripe running down the middle is quite amateurish in design to me. The Concerta2 stands on the other hand are pretty slick and are quite stable.

The Kanto SP stands arrived and I just finished putting them together.

Short summary:
Quality reflects the price, which is so so. It is sturdy but if you are OCD and / or not ready to do some DIY, look elsewhere.

Long summary:

• The smallish package weights 35lb! You are getting a lot of powder coated steel for your money, folks.
• The finish is a matted white powder coating, typical of other stands around this price (I paid £109 on Amazon). There are a few small spots of imperfection but no deal breaker for me.
• The curved corners of the base cover plate isn't cut straight, you can clearly see it is wobbly on every corner. But since the wobbly edge faces down on the floor, I decided to let it go.
• Careful when you bolt the column to the base - it's secured by 2 hex screws and the column DOES NOT SELF CENTER! Pay attention when assembling. Note to designer - in the future use 3 bolts in a triangular configuration.
• The top plate is designed to allow for a degree of rotation, which is kind of this stand's selling point. In reality the connection between the bracket and the column is only a single hex bolt, and the interface is wobbly due to unavoidable tolerances between the plate and column. I fixed this by applying 3 layers of electrical tape below the junction where the column meets the plate:

• Once assembled, the entire stand is solid IF you do the DIY on the underside of the top plate as I described.
• The stand comes with 2 sizes of top plate - one narrower and rectangular, a second one is larger and square. At first I was going to use the narrower plate because it will sit completely within the footprint of the M105, but in the end I ended up using the larger square plate, because it is a lot sturdier for the speakers, and towards the rear only a small bit of plate protrudes past the speaker. I thought it was acceptable for the extra support.

The 26" height is just right for me. And its nice to be able to tug away the speaker cables through the columns.

 

[KaiserSoze]

Actually it does not look bad at all. The electrical tape solution will likely need to be replaced at some point with a more lasting solution. As for aesthetics, the mismatch in the shape of the upper plate and the speaker would bug me. I've built semi-custom stands in the past and generally a custom upper plate is essential. Assuming the plate in the pictures is the larger of the two, your mission, should you choose to accept it, is made easier by virtue of the manufacturer having included a smaller plate. Since you are probably going to paint it anyway, a stack of several thin layers of hardboard ("Masonite") may be most suitable, glued together using epoxy glue. If each layer is cut independently and oversized, the stack can be sanded down to final size after the layers are bonded together. To marry the custom plate to the small included plate I would use double-sided tape to bond them temporarily while I drilled four holes through both plates at once. Rounded bolt heads protruding above the plane are not a problem if they are low in profile and if they have Phillips heads (cross-hatched) rather than single slots which are always hideous. The underside will also be visible so there's also that to deal with. Small pieces of white PVC pipe with inner diameter just the right size to grab the nut might work. If there is no perfect size match, some little bits of tacky stuff should suffice. I like your Yamaha amp by the way.

 

[Archsam]

Actually it does not look bad at all. The electrical tape solution will likely need to be replaced at some point with a more lasting solution. As for aesthetics, the mismatch in the shape of the upper plate and the speaker would bug me. I've built semi-custom stands in the past and generally a custom upper plate is essential. Assuming the plate in the pictures is the larger of the two, your mission, should you choose to accept it, is made easier by virtue of the manufacturer having included a smaller plate. Since you are probably going to paint it anyway, a stack of several thin layers of hardboard ("Masonite") may be most suitable, glued together using epoxy glue. If each layer is cut independently and oversized, the stack can be sanded down to final size after the layers are bonded together. To marry the custom plate to the small included plate I would use double-sided tape to bond them temporarily while I drilled four holes through both plates at once. Rounded bolt heads protruding above the plane are not a problem if they are low in profile and if they have Phillips heads (cross-hatched) rather than single slots which are always hideous. The underside will also be visible so there's also that to deal with. Small pieces of white PVC pipe with inner diameter just the right size to grab the nut might work. If there is no perfect size match, some little bits of tacky stuff should suffice. I like your Yamaha amp by the way.

When I first worked on the top plate I was going to use rubber shims - I have plenty of shims of various thickness in my tool box, but the gap is just too small - after applying the 3 layers of electrical tape I had to use force to slide the top place across the column and into position (otherwise it will still wobble). Then what I did just now is get underneath the stand and use a sharp blade to gently score the tape along the column junction. I was able to peel away the excess tape and it looks 100% clean. The tape that is wedging the gap is in permanent compression so it won't go anywhere.

Now on the custom top plate - I was thinking a little differently, my objective would be to create a plate that allows me to secure the speakers via the 3 pre-tapped screw holes underneath the speakers. Material of choice will be clear plexiglass, I reckon 5mm should do the trick. Because there is already a single pre-drilled screw hole in the middle of the existing base plate (meant to secure Kento's speakers), I was thinking that the new plate can just screw into that using a countersunk screw. To prevent it from rotating I can drill 3 little holes along the left / right / rear edge of the metal base plate and insert small clear acrylic dowels. Then it'll be simply sourcing some lovely mushroom head hex bolts in stainless steel / nylon washers to bolt everything together. I thought this is easy enough to make and should look pretty cool?

And thanks for noticing my Yamaha amp - i owned it for almost 4 years now and I still cannot stop staring at it sometimes. SQ is fantastic - can't imagine using anything else.

 

[KaiserSoze]

When I first worked on the top plate I was going to use rubber shims - I have plenty of shims of various thickness in my tool box, but the gap is just too small - after applying the 3 layers of electrical tape I had to use force to slide the top place across the column and into position (otherwise it will still wobble). Then what I did just now is get underneath the stand and use a sharp blade to gently score the tape along the column junction. I was able to peel away the excess tape and it looks 100% clean. The tape that is wedging the gap is in permanent compression so it won't go anywhere.

Now on the custom top plate - I was thinking a little differently, my objective would be to create a plate that allows me to secure the speakers via the 3 pre-tapped screw holes underneath the speakers. Material of choice will be clear plexiglass, I reckon 5mm should do the trick. Because there is already a single pre-drilled screw hole in the middle of the existing base plate (meant to secure Kento's speakers), I was thinking that the new plate can just screw into that using a countersunk screw. To prevent it from rotating I can drill 3 little holes along the left / right / rear edge of the metal base plate and insert small clear acrylic dowels. Then it'll be simply sourcing some lovely mushroom head hex bolts in stainless steel / nylon washers to bolt everything together. I thought this is easy enough to make and should look pretty cool?

And thanks for noticing my Yamaha amp - i owned it for almost 4 years now and I still cannot stop staring at it sometimes. SQ is fantastic - can't imagine using anything else.

I didn't realize that the speakers have three pre-tapped screw holes - I assume that they have threaded inserts?

Clear acrylic might be nice, however it won't look like tempered glass even if you use a nice thick piece at least 10 mm (15 mm would be better I think). You'll have to polish the edges of course, and it won't look the same as tempered glass. If you cut the custom plate to closely match the speakers it isn't going to show, which is why I expected that you'd be painting it white.

If there is a usable threaded hole on the upper surface of the included metal plate, then certainly this would be the way to marry the custom plate to the included metal plate. To prevent rotation you probably won't need more than a single pin, and the more pins you use the more difficult it is going to be to get them all aligned.

Obviously the design has to consider the order of assembly - do you affix the acrylic plate to the bottom of the speaker and then ... No, this does not seem correct, especially since you mentioned using a countersunk screw to attach the acrylic plate to the included metal plate. After assembling the entire stand including the new acrylic plate, you then will insert screws through the holes drilled through the acrylic and into the threaded inserts in the bottom of the speakers, correct? Will these holes also need to be drilled through the included metal plate? You will make these holes by drilling down through the acrylic plate after you've attached it? I suppose this works, but is it really important for the speaker to be screwed down to the stand? I would be more concerned about the entire stand tipping to one side. How heavy is the stand's lower plate?

You spent a heck of a lot more money on that lovely Yamaha integrated amp than on the speakers. Galvanometers are kind of silly, but I've always been fond of them. Galvanometers always say, "expensive high-end amplifier". Makes me wonder if there are laws in Asia that forbid putting galvanometers in amplifiers that cost less than $2000. I also noticed a matching tuner that looks clean, although on the USA site it is only available in black. But I suppose over-the-air radio is kind of silly these days. Also there are some very clean-looking disc players.

 

[Archsam]

I didn't realize that the speakers have three pre-tapped screw holes - I assume that they have threaded inserts?

Clear acrylic might be nice, however it won't look like tempered glass even if you use a nice thick piece at least 10 mm (15 mm would be better I think). You'll have to polish the edges of course, and it won't look the same as tempered glass. If you cut the custom plate to closely match the speakers it isn't going to show, which is why I expected that you'd be painting it white.

If there is a usable threaded hole on the upper surface of the included metal plate, then certainly this would be the way to marry the custom plate to the included metal plate. To prevent rotation you probably won't need more than a single pin, and the more pins you use the more difficult it is going to be to get them all aligned.

Obviously the design has to consider the order of assembly - do you affix the acrylic plate to the bottom of the speaker and then ... No, this does not seem correct, especially since you mentioned using a countersunk screw to attach the acrylic plate to the included metal plate. After assembling the entire stand including the new acrylic plate, you then will insert screws through the holes drilled through the acrylic and into the threaded inserts in the bottom of the speakers, correct? Will these holes also need to be drilled through the included metal plate? You will make these holes by drilling down through the acrylic plate after you've attached it? I suppose this works, but is it really important for the speaker to be screwed down to the stand? I would be more concerned about the entire stand tipping to one side. How heavy is the stand's lower plate?

You spent a heck of a lot more money on that lovely Yamaha integrated amp than on the speakers. Galvanometers are kind of silly, but I've always been fond of them. Galvanometers always say, "expensive high-end amplifier". Makes me wonder if there are laws in Asia that forbid putting galvanometers in amplifiers that cost less than $2000. I also noticed a matching tuner that looks clean, although on the USA site it is only available in black. But I suppose over-the-air radio is kind of silly these days. Also there are some very clean-looking disc players.

You are quite right about the clear acrylic - I gave it more thoughts after writing, and yes the edge on show is tricky because that is really all you see when you sit at the listening position. One idea is simply to switch to a white acrylic - no need to paint it as long as it gets a nice fine sanding.

Yes there are three threaded inserts under the speakers. They are supposed to work with the Revel M stands.

Assembly wise I thought it is pretty straightforward - since I can measure the holes under the speaker quite accurately I can have the custom plate cut and all the holes pre-drilled. Then the original metal plate is fixed to the acrylic using countersunk screw in the middle, the pins inserted to stabilise rotation, then the plate is fixed down to the column, and finally the speakers are placed on top and the screws goes in from underneath.

But then I thought..... no matter how neat I can make it, the acrylic will likely be thicker than 5mm as I might have hoped. You are right in that the thickness will likely be more, maybe around 10mm - the weight of the speaker held over 3 screws, which in turn is sitting on top of a small metal plate, yeah better make it beefier, but that will ruin the aesthetics... I kind of dig the look of the speakers sitting atop of a 3mm steel plate...... so minimal. I think it's going to be really hard to beat that.

How much will a powder coated, custom cut and drilled 3mm steel plate cost??

Ah my amp - I got a heck of a deal on it from a shop in Edinburgh. Ex-demo but with very light use. If I had to pay full price I would never be able to afford it

Edit: Regarding the weight of the base - You see the thickness of the base in my photo? Underneath that cover there is an equally thick and solid steel plate. I'll say roughly half of the total weight of the stand is in that plate.

 

[KaiserSoze]

You are quite right about the clear acrylic - I gave it more thoughts after writing, and yes the edge on show is tricky because that is really all you see when you sit at the listening position. One idea is simply to switch to a white acrylic - no need to paint it as long as it gets a nice fine sanding.

Yes there are three threaded inserts under the speakers. They are supposed to work with the Revel M stands.

Assembly wise I thought it is pretty straightforward - since I can measure the holes under the speaker quite accurately I can have the custom plate cut and all the holes pre-drilled. Then the original metal plate is fixed to the acrylic using countersunk screw in the middle, the pins inserted to stabilise rotation, then the plate is fixed down to the column, and finally the speakers are placed on top and the screws goes in from underneath.

But then I thought..... no matter how neat I can make it, the acrylic will likely be thicker than 5mm as I might have hoped. You are right in that the thickness will likely be more, maybe around 10mm - the weight of the speaker held over 3 screws, which in turn is sitting on top of a small metal plate, yeah better make it beefier, but that will ruin the aesthetics... I kind of dig the look of the speakers sitting atop of a 3mm steel plate...... so minimal. I think it's going to be really hard to beat that.

How much will a powder coated, custom cut and drilled 3mm steel plate cost??

Ah my amp - I got a heck of a deal on it from a shop in Edinburgh. Ex-demo but with very light use. If I had to pay full price I would never be able to afford it

Edit: Regarding the weight of the base - You see the thickness of the base in my photo? Underneath that cover there is an equally thick and solid steel plate. I'll say roughly half of the total weight of the stand is in that plate.

I think white acrylic should work very well and will be a perfect match to both speaker and stand. You've decided to use a thin steel plate instead, presumably with white powder coating. I have no idea what that would cost, but anything in the way of custom fabrication is likely to cost more than I would want to pay for it. An alternative would be to mix up some epoxy and add white pigment, titanium dioxide most likely. You can get epoxy kits that are intended for pigment to be added. But I don't know whether you'd get by without a sprayer, which means you will need some sort of air compressor and tank. You could also maybe just buy a can of spray-on enamel. Spray paint nowadays seems to be completely different from what spray paint was forty years ago. Much better formulations and even the nozzles on the cans work very well. Some of the spray-on enamel is claimed to be epoxy but since it isn't two-part I have no idea what that means. When I think of epoxy I think of hardening due to a chemical reaction between two parts that have been mixed together. Maybe you could buy a can and experiment with it. But if it were me I wouldn't mess with the thin steel plate. I would go with the 10 mm white acrylic. The ability to easily cut it and shape it yourself is a very significant advantage, and it will probably cost a small fraction of what you will end up paying for the steel plate with custom cutting and powder coating. It could end up costing more than you paid for the stands. The acrylic will be so much cheaper that it would make sense to do it first and then decide whether you're happy with it. As for measuring for the three holes, my experience has been that no matter how carefully I measure something there will be some slight error somewhere along the process that will mess it up. It has to be perfect. If you can find some small screw-in things with sharp points at the center, you could transfer the triangle accurately to a piece of sturdy cardboard (not corrugated obviously). When you do this with the little pointy things go ahead and make three very tiny holes in the cardboard, then take a sharp pointed tool, not something chiseled to a point but something like a big needle and make three tiny marks on the plate. But first use double-stick tape to tape the piece of cardboard to the plate so that it cannot move around. Then all you need is a simple guide for the drill bit, which you can find in a wood working tool shop or in a good hardware store. The only error-prone step will then be when you attach the guide to the plate. You need some way to make absolutely certain that the guide is precisely centered on the tiny mark. If you can figure out a way to be accurate at this step, then this method will likely be better than measuring the sides of the triangle. But of course it also depends on what you're using to take the measurement. Did I remember to suggest using a 10 mm plate of white acrylic instead of bothering with a steel plate and powder coating?

 

[Archsam]

I think white acrylic should work very well and will be a perfect match to both speaker and stand. You've decided to use a thin steel plate instead, presumably with white powder coating. I have no idea what that would cost, but anything in the way of custom fabrication is likely to cost more than I would want to pay for it. An alternative would be to mix up some epoxy and add white pigment, titanium dioxide most likely. You can get epoxy kits that are intended for pigment to be added. But I don't know whether you'd get by without a sprayer, which means you will need some sort of air compressor and tank. You could also maybe just buy a can of spray-on enamel. Spray paint nowadays seems to be completely different from what spray paint was forty years ago. Much better formulations and even the nozzles on the cans work very well. Some of the spray-on enamel is claimed to be epoxy but since it isn't two-part I have no idea what that means. When I think of epoxy I think of hardening due to a chemical reaction between two parts that have been mixed together. Maybe you could buy a can and experiment with it. But if it were me I wouldn't mess with the thin steel plate. I would go with the 10 mm white acrylic. The ability to easily cut it and shape it yourself is a very significant advantage, and it will probably cost a small fraction of what you will end up paying for the steel plate with custom cutting and powder coating. It could end up costing more than you paid for the stands. The acrylic will be so much cheaper that it would make sense to do it first and then decide whether you're happy with it. As for measuring for the three holes, my experience has been that no matter how carefully I measure something there will be some slight error somewhere along the process that will mess it up. It has to be perfect. If you can find some small screw-in things with sharp points at the center, you could transfer the triangle accurately to a piece of sturdy cardboard (not corrugated obviously). When you do this with the little pointy things go ahead and make three very tiny holes in the cardboard, then take a sharp pointed tool, not something chiseled to a point but something like a big needle and make three tiny marks on the plate. But first use double-stick tape to tape the piece of cardboard to the plate so that it cannot move around. Then all you need is a simple guide for the drill bit, which you can find in a wood working tool shop or in a good hardware store. The only error-prone step will then be when you attach the guide to the plate. You need some way to make absolutely certain that the guide is precisely centered on the tiny mark. If you can figure out a way to be accurate at this step, then this method will likely be better than measuring the sides of the triangle. But of course it also depends on what you're using to take the measurement. Did I remember to suggest using a 10 mm plate of white acrylic instead of bothering with a steel plate and powder coating?

Yeah agreed we are making things far too complicated!

How about 10mm white acrylic sheet cut to match the shape of the M106, bonded down to the small metal plate using a compatible epoxy (I'll have to strip off the black foam pad first and sand off the PPC), and forget about the screw holes and just put the speaker on top? I will probably put a few isolation rubber grip pads down for good measure.

In fact, without having to bolt the speaker down to the acrylic, I can reduce the thickness again to, say 6mm. That is more like it!