# To flush or not to flush?



## Christos (Dec 27, 2007)

I am puzzled on whether I should make my CSS FR125SR drivers flush-mounted or not on the baffle.Is it necessary for a driver to be flush-mounted sonic-wise?It is about a mini-monitor full range DIY project.

Thanks in advance..


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## Bill Fitzmaurice (Jun 14, 2008)

Flushmounting is critical when the depth of the mounting flange is a quarter wavelength, lest the wavefront diffract around the flange to reflect off the baffle and then meet the original wave 180 degrees out of phase, causing a response notch.
OTOH if that flange is 1/4" thick, for instance, that's a quarter wavelength at 13kHz. Chances are the driver will be beaming that high anyway and there won't be any diffraction around the flange. But if you use a 3/8" dome tweeter with a 1/4" thick flange then by all means flush mount it. 
Studies have been done over how much difference flush mounting makes, and the answer is that, while response is different when flush mounted, it's not necessarily better. High end speakers tend to be flush mounted because it looks better and because it's expected.


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## JCD (Apr 20, 2006)

Bill has more knowledge in this area than I do, but if I could, I would always flush mount. I thought there was never a downside, and potentially/probably an upside. 

Plus, I just think they look better flush mounted.

Given that, I have a line array that I'm (STILL!!!) working on that uses drivers that are squarish rather than round. I'm just not that good of a woodwooker to even bother trying.

JCD


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## Christos (Dec 27, 2007)

Bill Fitzmaurice said:


> Flushmounting is critical when the depth of the mounting flange is a quarter wavelength, lest the wavefront diffract around the flange to reflect off the baffle and then meet the original wave 180 degrees out of phase, causing a response notch.
> OTOH if that flange is 1/4" thick, for instance, that's a quarter wavelength at 13kHz. Chances are the driver will be beaming that high anyway and there won't be any diffraction around the flange. But if you use a 3/8" dome tweeter with a 1/4" thick flange then by all means flush mount it.
> Studies have been done over how much difference flush mounting makes, and the answer is that, while response is different when flush mounted, it's not necessarily better. High end speakers tend to be flush mounted because it looks better and because it's expected.


Bill, the driver is this one: http://www.creativesound.ca/pdf/CSS-FR125SR-dataS.pdf

So, what do you reckon?Is it "safe" not to flush mount it?

Thank you very much for your time.


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## Christos (Dec 27, 2007)

JCD said:


> Bill has more knowledge in this area than I do, but if I could, I would always flush mount. I thought there was never a downside, and potentially/probably an upside.
> 
> Plus, I just think they look better flush mounted.
> 
> ...


To be honest from a visual point of view I prefer it flush-mounted as well.But if it is to be done this way I have to look for a man that knows how to do it and this is not an easy task.My skills and equipment are insufficient for a job like this one..:innocent:


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## Bill Fitzmaurice (Jun 14, 2008)

Christos said:


> Bill, the driver is this one: http://www.creativesound.ca/pdf/CSS-FR125SR-dataS.pdf
> 
> So, what do you reckon?Is it "safe" not to flush mount it?
> 
> Thank you very much for your time.


I probably would, but only because being a round frame it's a very simple job. OTOH the effect of so doing with such a thin frame would be barely measureable, and definitely not audible.


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## solid7 (Jan 31, 2008)

JCD said:


> Given that, I have a line array that I'm (STILL!!!) working on that uses drivers that are squarish rather than round. I'm just not that good of a woodwooker to even bother trying.
> 
> JCD



You have defeated yourself before even trying. Any old clod can make a router template, and reproduce the same pattern, over and over again....

Personally, I make my (non-critical) templates using a piece of paper contact cemented onto a piece of MDF. You can use the paper to trace the shape of your speaker. Then, a scroll or saber saw to cut the pattern, and some sandpaper and/or rasp to finish out the shape, and you are good to go.


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## Christos (Dec 27, 2007)

Bill Fitzmaurice said:


> I probably would, but only because being a round frame it's a very simple job. OTOH the effect of so doing with such a thin frame would be barely measureable, and definitely not audible.


Bill, you are a star! Thanks a ton! BTW what does _OTOH_ means?


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## Anthony (Oct 5, 2006)

On The Other Hand

Glad I could help


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## Anthony (Oct 5, 2006)

For router templates, I like luan or hardboard first. They don't compress or dimple as the bearing rolls over them (as much).

MDF is usually used, though, since I have so much of it in the shop. They are usually good for 5 or 6 passes before redoing them. However if you have a good MDF template and want to save it forever there are a couple of tricks:

Use the template to make a new one out of a harder material.
Use CA (cyanoacrylate or crazy glue) to harden the edge
Use PVA (wood glue) to do the same thing (not as effective, but still helps).

Oh and rectangular holes are awful. I went through three templates before I got one I liked for the BG Neo3 planar tweeter. Lots of filing, chiseling, routing, and repeating.


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## Bill Fitzmaurice (Jun 14, 2008)

Anthony said:


> Oh and rectangular holes are awful. I went through three templates before I got one I liked for the BG Neo3 planar tweeter. Lots of filing, chiseling, routing, and repeating.


Cut rectangular templates with a router, using a straight guide as a template to cut the template. Rough cut the opening with a jigsaw first to minimize the amount of material that the bit has to remove.


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## Anthony (Oct 5, 2006)

Yeah, I did jigsaw out the bulk of it and used straight edges for the template.

however, you still need to chisel or file out the corners, at least on the final piece. Sadly I found out that chisels are better in regular wood than MDF -- much more room for error. DOH :sad:


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## Jason Schultz (Jul 31, 2007)

I mounted a dome mid and tweeter in soft pine wood. I don't have a router so used a chisel, scalpel blade and lots of care. needless to say it took along time. good result though!


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## solid7 (Jan 31, 2008)

Anthony said:


> For router templates, I like luan or hardboard first. They don't compress or dimple as the bearing rolls over them (as much).


For MDF, a simple coat of glue (thin it a bit with water, if you like) will work wonders on templates. It makes it hard enough not to compress with bearings.

You may want to thin it enough to paint it on with a roller for a good size template.


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