[Acetone]

So anyways, audio-**** measuring aside, do my calculations make sense?
Did I properly design an ABC Box?

[kendogg]

Originally Posted by Acetone

So anyways, audio-**** measuring aside, do my calculations make sense?
Did I properly design an ABC Box?

I would say yes, tuning to 35 should get you closer to the 30/60 you want. Measurement swith a meter would be nice, but meh. Should be fine.

[Acetone]

Sorry for the long delay, I've finally had enough time off work to get building.







Built it a little bit big just in case....

I am at .774cuft in the small chamber and 1.635 cuft in the big chamber ( net ).

Ideally I want .7 / 1.4 to achieve the 1/3 , 2/3 thing.

[Acetone]

Ok need some serious F'ng help here.

braced it, glued it, sealed it. wired it up and it sounds like garbage.

Nothing but buzzing and distortion.


internal volumes are .693 in the small chamber and 1.44 in the big chamber.

sounds like its hitting resonance at like 90 Hz or something like that

[kendogg]

Do you have pictures? What are your ports dimensions? What ar ethe dimensions of the entire enclosure?

[Acetone]

Small Chamber:

-14" X 13.5" X 7.625" =

(.834 cubic feet)

Subtracted volumes


Port A : 3.5" diameter X 5.2" long =.09
Port C :3.5" diameter X 2.4" long =.05


NET= .694 cubic feet

Big Chamber:

- 14" X 14" X 16" =

(1.815 cubic feet)

Subtracted volumes

Subwoofer = .06
Port B:3.5" diameter X 5.2" long = .09
Port C:3.5" diameter X 2.4" long =.05
Plate Amp = .03
Bracing= .12

NET= 1.46 cubic feet

[Acetone]

Here is how it looked before the bracing.



Here it is with bracing ( as you can tell I added a lot to get the volumes correct).



Small Chamber



Big Chamber



up shot

[kendogg]

Why are you using 2 different sized ports? Thats probably the issue. All 3 need to be identical. Hopefully I can view the pics on my home comp. All I see are red X's here.

[Acetone]

All 3 ports are 5.20 " long

port A and B are mounted 1 inch deep into the front baffle so 4.2" is what is in the chamber

port C is mounted in the divider which is 1/2 inch thick so 2.25 in each chamber

I kinda guessed that it should be calculated as a solid cylinder.

[Acetone]

update!

Finally gave in and picked up a roll of fiberglass insulation. that solved 99% of the buzzing

Its real loud and can shake the room apart, but Its really low and boomy. Multi-meter tests will be completed this week.

Also going to throw a simple .5 cuF sealed box together and compare the response.

[kendogg]

Cool. Sorry, I've ben crazy busy the l;ast couple weeks, working 50+ hours a week, and getting ready to leave for vacation ina couple days, so I haven't had much time to look over your stuff. If it's bottom heavy, you probably oversized the enclosure slightly. I noticed that when I built mine as well, because I designed mine slightly oversized, and it was also bottom heavy. Keep in mind, it's going to rolloff very sharply on the upper range as well, so that may be part of the issue too.

[impreza2.0]

There are a million arguments as to why this could happen. Some say that the port should not be on the same panel as the driver, that there are cancellations that will result in audible distortion, others say that this adds efficiency. I think it adds noise, as is the case with every ported enclosure, the port is not going to be aerodynamically flawless, some imperfection is going to create a sound not found in the original recording.

A downfiring single ported enclosure with a very carefully tunedi and *polished* port will be as close to a sealed enclosures accuracy as possible with the benefit of a rolloff maybe a few Hz below the sealed enclosure's.

I realize this does not solve this experiment, but if you are building this speaker to listen to, it is really not practical. If it is to see what happens with this particular driver in this particular enclosure, cool... good work... but it's a compromise between bandpass and bass reflex with none of the advantages of either of them. You are creating a massive labyrinth port behind the driver in hopes to boost a second octave of resonance instead of just one, something that will inevitably wear out the driver much faster than even a very small sealed box. You might consider some form of electronic regulation of driver movement, a few good electronic crossovers are out there, you don't need a digital, just something w/ 24db per octave or thereabouts for a slope. There are RTA programs you can get for free online, just use your computer's mic and at least you can get an idea.

[Acetone]

Hey thanks for the responses !

Yeah I was just building it for the sake of building it. Now that I've got that out of my system.

I'm thinking either a .6 Cuft sealed box. or a 1 Cuft simple ported box.

Does anyone know if you can run a plate amp in a sealed box without running the risk of over heating?

[jjewell]

the only suggestion i have is to round off the edge's of the ports to smooth out the air flow. you may have a little port noise because of that.