The Frugel-Horn Project

[jleaman]

Originally posted by Harderror



As opposed to all the untrue questions that we have been asking?

I'm Sorry.

[soongsc]

Originally posted by jleaman
I have a true question. adding the phase plug will make the driver more open and have more of a bright top end ?

Theoretically, removing the VC cap and using a Phase Plug instead is to get better high frequency response. In reality, there might be some side effects if the driver design is not considered as a whole.

[jleaman]

Originally posted by soongsc


Theoretically, removing the VC cap and using a Phase Plug instead is to get better high frequency response. In reality, there might be some side effects if the driver design is not considered as a whole.

Thank you.. I'm just trying to understand if i need to do this or not.

[westend]

Originally posted by jleaman



Thank you.. I'm just trying to understand if i need to do this or not.

Dave could better answer this but IIRC the FE126e is constructed so that a dustcapectomy should not be tried. It has to do with the leads and the way they are attached to the cone.
Edit: Found that graphic info: http://www.planet10-hifi.com/FE127.html

[chrisb]

Yep, Dave had success only with the first pair but I killed them when trying to tidy up a bit of the glue residue on the inside of the VC former. After Dave had the same problem with the next pair he tried, we decided it was not worth the gamble. Too bad, cause it definitely helped.

[planet10]

Originally posted by Harderror
How should I make the baffle? Any curvature to the face? As in lathed? Or flat stop sign style?

Some room to experiment here. And compromises to be made.

The idea of the supra baffle is to push down the point at which baffle step starts taking affect to where the gain from the horn starts lifting response. The width determines where BSC starts, but the shape plays a big role in the ripple of the edge diffraction.

As a reference attached is page 23 of Olson's Acoustical Engineering (there is that magic number 23 ). This is my most visited page in the entire book. It graphically illustrates his results of how baffle shape affects baffle diffraction. Ignore the actual frequency in the charts we are more interested in the shapes (Olsen's baffles were 2 feet wide)

The shape of the mid chamber in the B&W Nautalis i probably a good example of what an optimum shape would be (you can be sure a lot of serious R&D money went into this shape). I'll post a pic in the next post. In Olson this would be an enhancement on the sphere.

As can be seen the worst shape is a cylinder with the driver mounted on the end. A practical realization of this in our case would be a flat disk. A stop sign isn't far behind (but from our A126 experiments still an improvement over none).

Note that after the Sphere probably the best shape is the square or rectangle with large 45 bevels and a section going straight back from there. Ron's supra baffle for the A126 fits in this category, and our latest stop sign does as well (with a 45 thru 1.5" of depth with a further 0.75" trailing edge) but gets a tad closer to the sphere. Do note what happens without the trailing edge (see the half sphere)

So how far do you go? Depends on resources (time, wood, skill, & money) & aesthetics -- there are some huge possibilities for artistically rendered shapes.

How big? Part of the juggling comes in with the size of the CC... the smaller the CC the more HF stuff comes out the back of the box... if you look at the FR curves of the FE126 or FE108 you can see that ideally this point is somewhere between about 200 & 300 hz so with a bit of fudging somewhere in the neighborhood of 12" (300mm). And -- within reason -- as deep as you can make it.

Also, should I mount the driver on the baffle and attach that or should I have the baffle flush with the speaker? If I mount the driver on the baffle that will increase my cc as well, this is probably good.

Totally open...

dave

[planet10]

B&W...

[planet10]

extract from the RonHorn A126 drawing...

[planet10]

and the A126 with stop signs...

[Harderror]

Ok, here is how I made my CC. The panel is just pressure fitted int o place and then caulked to seal it and stop any vibration. This is obviously for testing only, but, it seems to have worked quite well.