The importance of rebating drivers - World-Designs-Forum

VantheMan · #1 9th July 2007, 12:53 PM

Hi,
As I am going to use a solitary (per box) SEAS coaxial driver where the tweeter is in fact set back a good 2 cms from the bass driver surround, will it be so important to rebate the driver flush into the front baffle. From the speakers I have owned - Totem Arros and Heybrook HB2s (hi Peter), it´s only the tweeters that are in fact rebated, the bass mid drivers usually being fitted onto the front baffle without being flush fitted.
What´s the word on the street ?

Richard · #2 9th July 2007, 01:13 PM

Hi Chris, I'll stick my neck out and say it won't matter a jot. I went through all this with my Pro9 speakers, rebating the drivers after an initail build without, and not an iota of difference. Sure you'll see lots of theory about this, and baffle coverings, grills, and cabinet edges, but I can't hear them. Have a nice day

VantheMan · #3 9th July 2007, 01:39 PM

My nice day is guaranteed after reading your reply. As you may have guessed, I have never used a router in my life.
Cheers

Richard · #4 9th July 2007, 02:04 PM

No neither had I the first time in the 70's. They were a pro tool back then and too expensive for a teenager. I did have a jigsaw though. I broke a blade so it would only reach the depth of the driver chassis, and ground the end to a knife edge. I went round the outline then removed the wood with a chisel. Sounds crude but worked well and I still have that old jigsaw! Latest build, a few years ago saw me buying a router. Easy enough to use but you have to be careful freehand without a template that manufacturers will use. Also, don't try it after painting the baffle as the bit will blunt and burn out pronto

Chipboard soon blunts hss too so get carbide bits. In my case, as reported, this was all in vain. Possibly because I fit and use grills which are 1/2" high anyway, but I hear no difference without the grills either (very light stretch jersey). The xovers out the box, plastic film caps, and tri-wiring, I can hear

Brian · #5 9th July 2007, 05:14 PM

I can hear the difference between crossovers inside or outside the loudspeaker enclosure but can't tell any difference regarding any of the other things you mention, Richard. That includes single, bi and tri wiring.

My current speakers are tri-wired but sound the same to me as when they were bi-wired.

I had a pair of EPOS14's at one stage that I heard both single and then bi-wired....sounded the same to me. I used to suspect the hair inside my ears was blocking the sound or something, but my wife can't tell any difference either.

Scottmoose · #6 9th July 2007, 05:59 PM

With co-ax drivers? Very unlikely you'd hear a difference. Almost certain not to in fact. You've effectively got a midrange - HF horn in there, which is far more directional (I'm not sure that's quite grammar, but I'm slavering for my dinner) than you'd get with a conventional layout.

Of course, if you're building out of ply, you could just draw round the driver, and then with a sharp knife cut through one or two layers & carefully remove with a chisel or similar. I believe Derek Walton did that with a pair of Ariels.As I say though, I doubt it'd do anything other than make the front baffle a little more attractive.

#7 29th July 2007, 01:57 AM

Depends on the configuration of the driver basket and the thickness of the baffle.

If the rear edge of the baffle is going to obstruct the openings in the basket the driver should be rebated, and the rear edge of the hole rounded over.

Taking a typical Seas driver in a typical 18mm baffle, in all likelihood you should rebate it.

I've heard the effect of a builder's failure to rebate a midrange and it wasn't nice.

A good router is an essential tool for speaker building, along with a circle jig like the Jasper.

Primalsea · #8 29th July 2007, 06:57 PM

If your driver was a perfectly flat panel and was engineered to solve the problem of having a flat baffle then yes. As you have a cone driver connected to the basket by, I guess, a rounded piece of rubber then I wouldn't lose sleep over it.

You might want to think about padding the baffle with something like fleece blanket or sticking foam circles around the speakers. These will have much more effect, possibly good effect, than rebating a cone driver.

VantheMan · #9 30th July 2007, 05:27 PM

I think I´ll try the best of both worlds whilst not having to resort to a router i.e. I shall round off the inside edge of the cut out with a file and then "clad" the front baffle with a skin of 5mm MDF with a larger circle cut out to accomodate the outer diameter of the driver.
When you refer to padding the baffle with fleece blanket, do you mean on the outside ??? If so, what good effects might accrue ?

Primalsea · #10 30th July 2007, 08:33 PM

I don't have a full basis for comparison but the idea (which could be misguided) is that the fleece lining (on the outside, covered by leather) absorbs some of the reflections that would normally bounce of the baffle in various directions depending on the width and profile of the cabinet. This would clean up imaging but I can't say for sure if it has worked. I can say however that my speakers do have quite good imaging even in their non ideal position (firing across the short dimension of a long room and only about 2.5 meters away from the sofa).

On the 5mm front plate, this is a good idea if you want to avoid routing. However the best tool for cutting a neat circle is a router as they are nearly always supplied with an attachment to cut circles. You can do it with a jig saw but alot of sanding will be required to make it look neat.