How to cut holes for drivers with truncated frame

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Hi all,

I would like to countersink a driver with a truncated frame (Peerless 830875), but I don't know how to do the non circular cutout in the baffle. I successfully used a hand router with a simple jig (wood and nail) for round cutouts. Filling the part is not an option.

Thanks, Ralf
 
use the jigsaw with a guide. If teh guide is not attached to the saw, make one yourself out of a straight edge that you clip to you piece you need to cut

Edit: You can use your router the way also. A straight edge on the outside off the router parrallel to your cutting.

I Hope you understand What I try to explain. I know a drawing would be better, but I suck big time at that.
 
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Well assuming you're using more than one driver in your project, I'd suggest making a jig to guide a "flush trim bit" used in your router. Something that you'll have to design to be be easily clamped to your baffle, and have markings to ensure alignment.

Most routers can use an edge guide like this, (trd's suggestion):
http://catalog.sears.ca/wcsstore/MasterCatalog/images/catalog/70/00/092970007_1_271.jpg

Use that guide to develop your truncated edges, and a standard circle jig for the rest.

Jigsaws are messy, and if you do develop a jig any rough cuts will be transferred to your baffle.
 
Make a jig and use a jig guide on the router (see pic). The jig is cut oversize and is related to the bit size and jig guide collar.

Some builders are tricky and route out the round hole but use mouldings in the vertical edges of the speaker which gives the flat surface. See this example from Andy G.
Andy G's Trinity
 

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Thanks for the suggestions.
So the difficult task is to make a good jig.

Ralf

It's no problem with a good jigsaw as you can cut within 0.5mm easily. I use 8mm MDF for the jig and use a 6mm or 8mm bit to do the rebate. I tend to cause more damage to the jig by sanding over the cut a bit to exuberantly.... better left as cut as the router jig guide tends to glide over any anomalies due to the larger radius.

You can use the tweeter mounting holes to locate and hold the jig but generally clamps work well. The jig just has to be large enough so the clamps are away from the router base. Cleats can also be screwed on the underside to lock on the side etc of the enclosure so there is no movement.

A test run on some scrap material is advisable but I generally just get into the enclosure.

You want to try a rebate for a Vifa D26NC with a square heatsink as it's a job from hell. :mad:

Here's some rebated HDS drivers and one also has the tweeter rebate done via a jig due to the flat edge on the faceplate.
 

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Yeah on post #7 the tweeter seems flush to the front.
The other driver's setup makes it in part outside the housing. (if you look from the top 90 degrees to the bottom.) Would it had been possible to put that driver inside half an inch so that the rubber\foam forming the outside suspension of the driver would come
flush the the enclosure when at rest?
 
With that you would end up with a gutter (moat) between the edge of the basket and surround. AFAIK, having the surround extending past the baffle has no detrimental effect and is how 99% of speakers are built.

The HDS drivers do have a chamfer near the edge so even when rebated the basket still extends past the baffle. Drivers such as the PL18 etc can have the basket completely flush but the surround of course still sits proud. The 18W8531 has a radius on the basket so the edge can only be flush and the basket near the surround is about 3mm away from the baffle.

The main thing is to rebate the tweeter and it is not important for the mid woofer. I've built plenty of speaker with the HDS not rebated with no detrimental effects. Some who do that turn the driver 90° (also helps with smaller driver centres) to what I have done and place foam on the flat edge below the tweeter.
HDS with foam on top

I have also left mid woofers non rebated so I can get closer driver spacings as the mid woofer basket overlaps the tweeter faceplate similar to some of the Dynaudio speakers.

What is more important is to get the driver centres correct and for lower order crossovers, the driver offset. There is a study that has been commenced by Troels (maybe his next speaker is going to be a low order crossover going by his recent studies).
Troelsgravesen stepped baffle study
 
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I have also left mid woofers non rebated so I can get closer driver spacings as the mid woofer basket overlaps the tweeter faceplate similar to some of the Dynaudio speakers
I did the same on my last full range speaker build.
I did think about cutting a radius in the tweeter mounting plate to allow the mid driver to be flush and closer centre to centre. Too much work. Try the simple way first. It seemed to work OK.
 
As mentioned, I think this driver is fine for surface mounting. But, if you really want to flush mount it, here's one option for either the baffle or a template:

1. Use a board just a hair wider than the width of the driver at the flat portion and use a circle jig to cut the diameter of the driver at the non-flat part. If cutting the baffle, then just cut the recess here, if making a template, you'll need to clamp/fasten both the top and bottom piece and cut a circle all the way through.

2. If making a baffle (not template) then now cut the through hole. If making a template, ignore this step.

3. Now, glue a board the same thickness on either side. Now, you have a perfect baffle or template with nice sharp "corners". No "free hand" cutting needed, so you don't have as much worry about having a very steady hand...

Rabbitz, thanks for posting that link, great little article.
 
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