The Frugel-Horn Project

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
J

jleaman

Banned
Joined 2002
plus.google.com/photos/104656656065604242634/albums/5725366675475046257?banner=pwa&gpsrc
soongsc said:


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.
Click to expand...


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

chrisb

Member
Joined 2002
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

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
Paid Member
Harderror said:
How should I make the baffle? Any curvature to the face? As in lathed? Or flat stop sign style?
Click to expand...

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.
Click to expand...

Totally open...

dave
 

Attachments

  • page23-olson.gif
    page23-olson.gif
    36 KB · Views: 1,308
C

chrisb

Member
Joined 2002
Harderror said:
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.
Click to expand...


Tom, we're pretty much on the same page - if you're happy with the performance once the 126's are installed and fully broken in, you really need to try in baltic birch. Just watch Dave's posts for further refinements.
 
J

JohnnyBoy

Member
Joined 2004
planet10 said:

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.
Click to expand...

Awesome! I was hoping I'd come across this information again. I first saw it early last year when I was trying to determine what would be the best shape to use in fabricating my stainless steel enclosures. I originally was going to go with the sphere but after some consideration opted for an 8 liter vertical cylinder. The Jordan JX92 works extremely well in this arrangement with astonishingly deep bass and that with no BSC.
 

Attachments

  • jx92s.jpg
    jx92s.jpg
    38.9 KB · Views: 1,272
DaveCan

DaveCan

Member
Joined 2005
One thing I was wondering is if there is a limit to the size of a horn for the 108? If waf didn't matter and someone just wanted to do an all out no holds barred design ,would it be crazy big like the Klienhorn or more like a Ronhorn etc? Anyhow looking forward to maybe building the Frugel's and will gladly give a donation for all the hard work thats gone into the whole process. Dave:)
 
planet10

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
Paid Member
DaveCan said:
would it be crazy big like the Klienhorn
Click to expand...

Probably. Maybe a bit smaller. Mouth size determines low end... Klein horn is 42 Hz (full-space) ... you might not want to try to get the 108 to try to load a horn that low. If you only wanted to go to 50 hz, the mouth could be under 6' square. assume you are going to use them on a floor and you could get it down to 4' square.

dave
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom