My A7-500s. A journey

[Altec Best]

Yes, port and wings for sure.

I did a little port work today. Thought I'd make a "slot port". I.E. a rectangular port right at the bottom with the box bottom being one wall of the port. So now I have a 4" tall hole at the bottom the full width of the cabinet. Could not get it to tune worth a fart no matter how deep or shallow it was, but it does add a very nice 6dB or more at the bottom. Just what I needed! At 1M, the response has its problems (floor bounce, I suspect), but there is certainly more bass. Back at the listening sofa, it's more a more even response and that's great. Now I gotta bring the horns up.

Experimented with one wing, it does smooth things out a bit in the 200-300Hz range, so I will probably go with two. Progress.

Pano can you snap a few pictures ! A pictures worth a thousand words.

[dominique-tanguy]

Yes, port and wings for sure.

I did a little port work today. Thought I'd make a "slot port". I.E. a rectangular port right at the bottom with the box bottom being one wall of the port. So now I have a 4" tall hole at the bottom the full width of the cabinet. Could not get it to tune worth a fart no matter how deep or shallow it was, but it does add a very nice 6dB or more at the bottom. Just what I needed! At 1M, the response has its problems (floor bounce, I suspect), but there is certainly more bass. Back at the listening sofa, it's more a more even response and that's great. Now I gotta bring the horns up.

Experimented with one wing, it does smooth things out a bit in the 200-300Hz range, so I will probably go with two. Progress.

Congratulations! Good to hear that you are progressing in the right direction. Good luck for the next step! I am interesting to hear about the experiment with the "Horn Port".

[Panomaniac]

GM:
I'm not getting the picture. The 4" slot would be the smallest part of the "horn port" - its throat? And the horn part would live inside the cabinet?

[GM]

Right, visualize it as the last expansion of a folded up BLH and shorten the slanted board to experiment with raising Fb if desired. This was a University 'half horn' tweak I never got around to trying on this cab and forgot to mention the other day as a way to boost the mid-bass down around the front horn's cut-off.

GM

Oh, and to have a bit of 'having your cake and eat it too', if you over boost the mid-bass, raising Fb, you can dial it back by reducing the mouth area [mass loading it], lowering Fb to maybe find an acceptable trade-off without giving up too much bottom end. Learned this experimenting with a discarded '50's era University 'Triumph' ? speaker. The golden age of DIY was during the time when folks were turning perfectly good speakers into 'curbside queens' in the 'upgrade' to stereo/acoustic suspension designs. The pioneers of audio 'left no stone unturned' in trying to extract the most performance from the least amount of power.

[Panomaniac]

OK, let's see if I understand. A the moment, my port is at the bottom, 4" high and only plywood deep.


.
But to make a horn port I should try something as shown below?

[GM]

No, that would turn it into a quasi-TQWT which would lower tuning considerably. Instead, remove the baffle board and angle the vent duct board down to create a large vent mouth and the ~4" slot along the bottom back of the cab.

GM

[VolvoHeretic]

I guess I was understanding incorrectly, but here is my interpretation before I saw Panomaniacs. I will leave this up till Monday and deleat. Have a good weekend.

I am wondering how sound waves like wrapping around sharp corners. Are there any shear forces at play like there would be if you were dealing with moving air? Is that why you are calling for wings?

[Panomaniac]

GM, there is no slot at the back. The back bottom panel is not removable - and I don't want to cut into it.
Oh, Wait. Maybe something more like this?

[GM]

Now you're getting it! One of these days I hope to learn how to draw/illustrate, but then I've been saying this since '94, so don't 'hold your breath'.......... As a first approximation, I envisioned the vent baffle aimed at the back/bottom apex, laeving a gap to create a ~4" slot all the way across to 'drive' the horn vent. If I still had MathCad running, I could sim it to get it much closer to a good enough one using the 'sections' worksheets.

GM

[Old Guy]

GM you might find something useful here, a number of freebies including basic CAD software

World Class CAD Home

another neat freebie

http://sketchup.google.com/