Foam Core Board Speaker Enclosures?

[klampykixx]

makes my horn look pretty good on the bass side of things :P

see: Foam Core Board Speaker Enclosures? for my graph (grey trace) ill post up the rest of the graph tomorrow.

[xrk971]

Originally Posted by Don Hills

Like this:

                     Throat              +-- Horn 2 -- Radiator
Radiator --Driver -- Chamber -- Horn 1 --+
                                         +---- Horn 3 ---- Radiator

See attached. I assumed 6 cm depth. It doesn't look good... I think the volume (depth) is too small and the horn is tuned too low.



It is what it is. The impedance and excursion graphs (of the 70x70 cm model) show resonances at 61 and 119 Hz. I suspect the bifurcated horn is the problem. The longer of the two "output" horns is 138 cm, which is 1/4 wavelength at 62 Hz. That's why I want to re-sim with equal length horns.

Don,
Thank you for running the simulation. This is good stuff and exactly the sort of thing we should do to improve things. I am not sure if the huge peaks and dips are really there in real life because like I said, this is one of the best sounding speakers I have heard. It may be that I modded my plan and made sharp corners on the insides to act as filters, and I have stuffing in the main chamber and the throat passages. The stuffing probably does more than anything to Smooth things out. I guess someone should do a measurement - I don't have the equipment. However, I have run simple SA on my Android tablet (limited range on freq response due to built in mic) while listening to music and do not see the huge dips or peaks, it is very even in the 100 Hz to 2 kHz range. But this is music and not pink noise....

Regarding the simulation and the bifurcation, I have my doubts about what really happens physically - that is, is it really a bifurcated horn, or is the bifurcation channel (the split) really acting as a divider rib to the longer horn with an average length between the shorter and longer one? Also, could it be additional horn resonances - there are 4 different lengths if you look at the combination of possibilities. Nonetheless, this is awesome what you have done. I am new to using this modeling tool - would you mind attaching the input file/script or whatever is needed to run the simulation as a file attachment to a post on this thread? I am not new to mathematical simulations, as I use Mathcad all the time, I am just not familiar with akabak.
Regards,
Xrk971

[xrk971]

Don Hills,
One more question. Does your sim model the outputs of the radiators combined with effect of room walls to redistribute and mix everything like MJK's models? The room may be the effect that makes these sound great as the output from all edges is key to design, and placement in room is critical.
Thanks,
Xrk971

[Doug R]

Looks nice Cal!

[klampykixx]

I would also be keen on the input screen to the cornu please

[klampykixx]

Also to add ive changed a few things on my Hornresp and achieved a different result. So ill be sure to post up current specs of what im building. Just that the down side is incorrect driver specs. Im basing my sims on the tangband driver....

[iko]

Originally Posted by Don Hills

Like this:

                     Throat              +-- Horn 2 -- Radiator
Radiator --Driver -- Chamber -- Horn 1 --+
                                         +---- Horn 3 ---- Radiator

See attached. I assumed 6 cm depth. It doesn't look good... I think the volume (depth) is too small and the horn is tuned too low.
It is what it is. The impedance and excursion graphs (of the 70x70 cm model) show resonances at 61 and 119 Hz. I suspect the bifurcated horn is the problem. The longer of the two "output" horns is 138 cm, which is 1/4 wavelength at 62 Hz. That's why I want to re-sim with equal length horns.

Don, could you share your simulation script? I'd like to simulate with a different driver and in the same time play a bit with the model.

[SprockeT1597]

Originally Posted by klampykixx

@sprokeT i get mine from officeworks. Its not "cheap" at 10.30 a sheet, but it is compared to the price of wood. And it comes in different colours . Check the posterboard section.

ahh yeah thats where i saw it. I think 3mm MDf might be cheaper. (going to look into that) there is a aussies website that sells it too. The offcuts section looked promising.

[SprockeT1597]

Originally Posted by xrk971

Ouch!!! Even in Australian dollars, $10/sheet hurts.

Ive thought about using old pallets at work, because they are free.
Im pretty sure mdf is cheaper here that plywood. (at least at the hardware stores)

[SprockeT1597]

ok, so its very late here, and im way too many bourbons past being able to work things out matematically....

Would it be possible to scale this up to use the 6x9's I have sitting in front of me. Or would it have to be stupidly big.

BTW Cal, they look top shelf, and are an inspiration!