Advice needed on mini-monitor cabinet wood

[flashgo]

I had some spare Hiquophon tweeters, so I decided to build some mini-monitors. (Not the greatest logic, I know, but such is the mindset of this hobby.) At this point, I’ve also acquired some KEF B110 mids and appropriate X-over components and hardware. The plan is to build some Falcon Acoustics clones that are similar to (but better than) KEF Ref 101s. I also have the help of a professional carpenter friend who has experience building speakers. Oh yes, I’ve never built speakers before.

I need advice on wood. The Falcons are sealed boxes constructed of 12mm baltic birch. I’m told that this wood gives a little so that the boxes effectively absorb the back wave off the mids. (What do I know?) However, the KEF B110 has a mounting flange that takes up most of the thickness of the birch ply, so there’s no way they’ll be supported on the 12mm front baffle. I've never seen a Falcon, but I have some KEF Ref 101s, and they appear to have a thicker front baffle that accommodates the B110s.

Alternatives we’re considering:

1. use an 18mm thick baltic ply on the front, but that would require buying a huge chunk of wood for $50, only to use a few bits,
2. glue an extra 12mm wooden frame behind the B110 flanges, or
3. make the cabinets out of solid 18mm local mesquite wood.

With either birch ply or mesquite, the speakers will have style. Here’s a picture of a drawer constructed of the birch ply by my friend. Check out the finished end grain!

I love mesquite, but I fear it’ll affect the sound. My friend can also do a 3mm mesquite veneer over the birch, but will that adversely affect the sound since it’s a relatively thick veneer?

 

[Pete MB&D]

Hi,

You could surface mount the driver or double up the baffle making it 24mm. I would avoid solid wood no to pieces are the same nice uniform plywood is best, the veneer option sounds good but make sure its balanced by veneering it on the inside with some thing the same thickness.


Pete

 

[flashgo]

Sorry, I should've posted a picture of the B110 flange as well. Here it is next to a grooved side panel ready for the build:

You can see that the flange sticks out (down in the picture) and is about 1/2 the thickness of the 12mm ply. Surface mounting would leave the flanges protruding ~6mm above the surface. If we routed out the baffle to accommodate, there would be < 6mm holding it in place. Sounds like the best solution is to double up the baffle around the B110 flange.

BTW, that's mesquite showing in the foreground. I'm sorely tempted to veneer the cabinet with that. What's the logic of veneering the insides?

 

[Pulse Studio]

Hi Herman

I have recieved your mail many thanks So you finally succumbed to the Ref 101's nice work, did you you get them for a good price?? they are very competent monitors but obviously they will lack the weight of your Briks

So you are building the Falcon Mini Monitor deep cabs, using a B110 and Hiquphon tweets, they will sound quite respectable if you chose the x-over carefully, will you be making the Falcon recommended x-over which is basically the LS3/5a design but not using the auto-transformers, but can be made to sound just as good using Ferrite cored transformers or better still Laminate cored inductors. You will nee to employ a toatlly different network for the Hiquiphon tweeter to that of the Kef T27 though, but maintain the Falcon x-over for the B110 section, this is quite critical.

On the Falcon assembly details it suggests that the B110 should be rear loaded, this is to comply to the BBC 3/5a spec to rid a nasty resonant node that is set up with the B110 front loaded, if you observe the chassis basket of the B110 it will become clear that when this unit is front loaded onto 12mm thick baffle the air movement from the back of the B110 cone will be restricted due to the baffle thickness. what you will need to sourse is some rubber 'U' channel strip to place around the edge of the B110 chassis to form a seal, this was available from Stirling Broadcast along with the 10mm thick felt diffraction strips for the tweeter, click on the link on this site for more info.

Hope this helps

Paul

 

[flashgo]

Hi Paul, great to hear from you!

So you finally succumbed to the Ref 101's ... they are very competent monitors but obviously they will lack the weight of your Briks

The Ref 101s are very impressive for such little squirts, with lots of air. When I first hooked them up in my home system, I wondered whether I had wasted all that effort on my tri-amped briks. In the end, it was just a passing mini-skirt -- I still love my brik system. But the 101s are great hanging off the wall in my wife's studio. They get impressively loud!

will you be making the Falcon recommended x-over which is basically the LS3/5a design but not using the auto-transformers, but can be made to sound just as good using Ferrite cored transformers or better still Laminate cored inductors. You will nee to employ a toatlly different network for the Hiquiphon tweeter to that of the Kef T27 though, but maintain the Falcon x-over for the B110 section, this is quite critical.

Yes, I'm doing the LS3/5a X-overs (on your recommendation ), although I went with some over-kill components. Michael Percy is closing out his alpha-core inductors, so I got a set for these X-overs. I'm planning to just wire the components together, but the X-over will be large and weighty compared to the speakers. I had planned to put the X-overs on the bottom inside of the cabinets (with bi-wire terminals), but I'm wondering if I should/can mount them on the back.

Hmm, different X-over for the Hiquphons? I'll double check.

On the Falcon assembly details it suggests that the B110 should be rear loaded, this is to comply to the BBC 3/5a spec to rid a nasty resonant node that is set up with the B110 front loaded, if you observe the chassis basket of the B110 it will become clear that when this unit is front loaded onto 12mm thick baffle the air movement from the back of the B110 cone will be restricted due to the baffle thickness. what you will need to sourse is some rubber 'U' channel strip to place around the edge of the B110 chassis to form a seal, this was available from Stirling Broadcast along with the 10mm thick felt diffraction strips for the tweeter, click on the link on this site for more info.

Paul, no link came through. Could you send again? The rubber U channel sounds like a necessity with the rear mount. So the cut-out in the baffle should be a simple circle? And how does the bolt hardware work for the B110s? Should I use a flat head bolt, so it'll be flush on the front of the baffle?

Cheers!

 

[Pulse Studio]

Hi Herman

here is the link to Stirling Broadcast:

http://www.stirlingbroadcast.net/

and here is another useful link for the 3/5a clone assembly:

http://www.ls35a.com/

The rubber U channel is a definate neccessity
I use M5 allen key button cap black engineering bolts for securring my B110's, with a fibre washer, flat washer, shakeproof washer and nut on the rear of the B110 chassis.
The BBC licenced speakers used M5 countersunk engineering bolts to secure their B110 in the pukka 3/5a design, yes the hole cut out is s simple circle, look on the Falcon assembly details I sent to you, the size for the cut-out is on their info, or it can be found somewhere on the unofficial ls35a site I have linked you too.
Oh yes you must use a suitable x-over section for the Hiquphon, I guess a pair of Kan MkII would be about correct, or indeed the top section of your Briks, they will not be that far away from the real deal, out it this way, far better than the standard T27 x-over section which is tailored specifically to this tweet, do not use

Finally don't simply wire the components birds nest style, not a good plan, use some good quality plain fibreglass board with no copper track, look at the Falcon x-over layout and simply drill small 1.2mm holes to suit the component layout and feed the component leads thru, use some double sided tape or self adhesive thin foam between board and components to hold them securely and avoid rattles, then join all the leads on the underside of the glassfibre board to follow the circuit topology, I can send you some pics of my DIY completed 3/5a x-overs if you wish?? but these are using copper clad board that I traced out and etched.

Paul