What does this mean?

[jon_denmark]

Hi
I am going to build a pair of monitors developed by zaphaudio called zd5. I have to do a modification of the woofers but im not excactly sure what to do.

The explanation by John Krutke:

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Strict requirements if you want this system to sound good: Countersink all drivers, scallop the rear of the woofer opening for airflow with a 1/2" chamfer bit and round over the top and sides with a minimum of a 1/2" roundover bit. A 3/4" roundover bit is even better if your router can handle it The driver locations are important, and the cabinet width must be 7.0". Varying from any of these design elements will make this system be less than the reference standard design it is meant to be.

http://www.zaphaudio.com/ZD5.html

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The sentence i don't understand should be in bold. What i think i understand is that i should do something with the hole on the back of the magnet.
What is a router?
a chamfer bit?
a roundover bit?

I couldn't find these words in my (old) english/danish dictionary.
Thanks in advance.

[Cal Weldon]

Hi Jon,

You are right. What John is saying is the the driver must be flush mounted from the front. This will require a tool called a router. This will recess the wood where the driver mounts and leave the frame flush with the baffle.

He is also says to round off the inside of the hole. This means that unlike a straight 45 degree angle, it will be the same as a quarter round. This helps let the sound out of the back of the driver. This is also done with a router but a different bit.

He is also saying that you should take this roundover bit, slightly larger than the one used for the driver hole, to the front edges of the speakers so the corners are rounded off.

Hope that helps. I'd draw a picture but I am not at my regular computer so I can't do that. Maybe someone else can.

EDIT: After reading it again, he said to chamfer the inside of the driver hole. A chamfer is a straight cut with no roundness to it. I usually round off the inside of the hole. Not sure if the straight chamfer is mandatory.

[:xrow:]

Hi Jon,

There is a link to a PDF file of the box design on the page you listed in your post. Look at the section cut in the drawing and you can see the chamfer cut for the inside of the midrange opening. You can also see the 1/2" roundover cuts at the edges of the front baffle the designer recommends. A router can make these cuts easy and very precise using bits designed for each type of cut.

Examples of routers:
http://woodworker.com/cgi-bin/SEARCH...TLFIND=160.001

A chamfering bit:
http://woodworker.com/cgi-bin/FULLPR...ARTNUM=110-093

A roundover bit:
http://woodworker.com/cgi-bin/FULLPR...ARTNUM=110-129

[jon_denmark]

Hi Cal

Thanks very much. I was on quite a bad track. I thought i needed to round off the back of the woofermagnet hole for airflow. But i see now that John ofcourse are talkning about the speakerbox and not the driver ;o)

Now everything make sense.

regards, Jon.