Use of Felt, and Speaker Alignment in an Optimal Cabinet.

[mistertrent]

After about 3 weeks of construction, I am ready to drill my holes for my new nearfield monitors. ... I just had a question for anyone who might know. I do not have a router, and was considering just mounting the speakers front mounted... but someone said I should use felt if I do front mount the speakers, but if I make a route and flush mount them, do I still need this felt?

Also, In an optimal prism cabinet design... is there an optimal speaker placement, or do I just measure the distance I have left over after C2C alignment, then halve it and place the speakers there... Bottom <-- Measurement --> Mid/woofer <-> Small Gap using calculated C2C <-> Tweeter <-- Measurement --> Top... as such?

Here's a picture of the best cabinets I have ever constructed. I am completely 100% happy with my work.





Sorry about the bad focus, lol. It was a last minute Cameraphone picture.

[TheSeekerr]

The felt is used to build the front baffle up to meet the edge of the driver, in order to minimise diffraction. If you flush mount the driver, you don't need to use it on the front baffle, although it won't hurt to use it to line the inside walls.

As for driver placement: off centre is best. Typically a little above centre vertically, a little left of centre on one speaker and a little right of centre on the other.

[moray james]

take the time to find natural wool felt. Any percentage of synthetic will not sound as good as 100% pure wool. The absorption of synthetic felt is not as wide band nor as uniform as that of natural wool.

[mistertrent]

Well, I might take the cabinets down to Bunnings one day and ask if some wood guy there can route the speaker holes down for me so I can flush mount, ... shouldn't cost me too much, there'd have to be someone there who would/could do it.

With the damping/lining the natural wool felt you mention... any particular thickness, do I just put it on the back panel, the sides, and bottom and top... but not the inside of the baffle?

[moray james]

if you are building a sealed cabinet then yes you could line the five wall all over. How much thickness is a loaded question as it will depend upon the density of the felt but a good starting ponit would be 3/8 of an inch thick and work up from there. In a sealed sub cabinet you could easily use an inch of felt. You might try experimenting with a blanket layer of felt 1/16 inch thick in the centre of the cabinet dividing the cabinet in two. That may have to end up just at the rear of the woofers magnet assembly.

[mistertrent]

Blanket Layer of 1/16" Felt... mmm all these ideas make me end up with no idea at all. lol.

I'll read up more about felt and damping and stuff I guess.

I still don't have any internal bracing inside the cabinet, but it's an MDF Sandwich, 32mm baffle, 24mm everywhere else. It seems pretty sturdy so far.

[mistertrent]

So, the speakers alignment should be kinda like this ... ?

[LineArray]

Hi,

i guess what TheSeekerr meant was to build the speakers pair-symmetric.

To have both drivers (woofer and tweeter of one speaker) centers in a
vertical line (and as near together as possible) is advantageous.

But that line should be off center, preferably in an incommensurable
relation of left and right distance.

Same applies to the vertical distances Woofer-Bottom and Woofer-Ceiling.

Kind Regards

[TheSeekerr]

Yep, listen to LineArray, he has the right idea.

[mistertrent]

So everything should be basically... centered? Joy. I'll make some final adjustments then cut the holes in the morning. I have no measuring equipment to find out how good this will sound when I'm done. But I'm guessing... awesome.

I'll place the mid/woofer and tweeter centres symetric to each other... then centre both in the box centre, then move that centre up about 5mm, and right about 5mm... or left for the other speaker. Sounds good?

As far as the felt goes, I'll assume to try and source some 3/4" for all the interior walls and see what happens when I get more to that part in a few days.