[fdandrews]

While looking at speaker porn in the "Let's see your O.B. speakers" thread,  , I noticed some designs that are slot loaded with vertical slots. I am familiar with the Nelson Pass slot loaded bass design that has the slot down at the floor, and the reasoning behind it. But I asked Mr. Pass if he thought the same effect could be had with the slot loading up off the floor, and he didn't think so. (Actually, I asked him if the same effect could be had with a round hole in front of the woofer but only 1/3 the area of the cone.) I wonder if anyone has compared conventional open baffle, with the opening roughly the same size as the speaker cone, with slot loading using the same woofer but with the slot off the floor, whether vertical or round or whatever else. Has anyone tried the Alpha 15, for example, both ways and did they find an audible difference?

[JohnR]

I guess you will lose some bass reinforcement if you lift it off the floor. Also, if you just have a hole instead of a slot I'd guess there's be more chance of turbulence/noise.

Just wondering what your design is/why you want to do that?

[matevana]

I did some testing with slot loading drivers in my Djinn project thread located here: http://www.audiocircle.com/index.php?topic=147509.msg1577937#msg1577937

Goal 2 of the project, along with the recap, has some comments on the perceived usefulness of slot loading. I experimented with various locations on the baffle (floor bounce) as well as one third and one quarter surface area of Sd.

My current OB rig (which is a test mule) continues to use the woofer design configuration shown in the project above. The top portion of the baffle can now be retrofitted in seconds to more easily accommodate (and switch between) various drivers that are sent to me for eval.

[fdandrews]

Thank you both for the replies. I was asking because I have a pair of Alpha 15s that I want to use with a pair of Fostex 166en fullrange drivers. (listed as 94 db/watt) I had planned to mount  the Alphas in an ordinary round hole, but then I saw some slot-loaded projects and was curious. The Djinn speakers are very attractive, even if the main difference is visual.