[Rudolf]

When I was evaluating some 3” FR drivers on a small 6” wide baffle lately, I got significant differences for the on-axis response to front and back:



My Fostex FE 83 and FF 85K, which can be mounted to the same hole, showed similar results as the Visaton FRS 8. All drivers were mounted in a 18 mm ply baffle with a 45° tapered hole.

Only when I put the FRS 8 on a 3 mm masonite baffle both front and rear response became comparable at 1-3 kHz:



These small drivers really need some open space around the basket to keep them happy. It may be debatable how big the influence of the back radiation of a dipole driver is. But if we know how to do it right, we should do it that way.
You might wonder how similar the front and back response would be without any baffle. To my surprise there was a wider difference than with the baffle:



I believe this aspect has to be considered for drivers up to 4-5". My 7" midrange works well without any taper in its mounting cut-out.

[freddyi]

thanks Rudolf  - that's very interesting - what happens at the listener's perspective on a woofer + fullrange system if  the fullrange is mounted to a perforated Masonite baffle (of larger area)?

[scorpion]

Hi Rudolf,

Not shown in the Mjao thread but I did widened the rear cut out for the MS-100CHQ, wouldn't hurt I thought.
To the better it seems.

/Erling

[Rudolf]

freddyi, you are asking strange questions. 

I would expect pegboard to be some kind of comb filter with the filter frequencies depending on the distance of the holes in the board. Every time when the distance equals half a wavelength the board should become “lossy”. The degree of loss would be determined by the hole size.
But surely somebody else is more knowledgeable about that than me.

I should not use the word "Masonite" any longer.

Rudolf

[PB]

Hi Rudolf and others, this is my first post on this forum.

I wonder how the response would look like if you had mounted driver from back of the 18mm board,
with the cutout in front of course.

Peter

[Rudolf]

Welcome Peter, 

for a newcomer to this forum you are asking an excellent question.

I believe you were asking for the driver radiating into that 45° taper like in a waveguide. I don´t see any difference for the 0° and 180° response, but off-axis response should be interesting. I believe I can measure it this weekend.

Rudolf

[PB]

I believe you were asking for the driver radiating into that 45° taper like in a waveguide. I don´t see any difference for the 0° and 180° response

Maybe my ignorance but why not? The major difference between the 18 and 3mm board, is that you have a higher peak around 2kHz with front mounted driver in the thicker board. Not with the back mounted.

On the other hand, this peak maybe doesn't matter at listening position?

Well, enough pestering you with my strange questions for this day...

Regards,
Peter