• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Box building Question

PioneerGuy75

PioneerGuy75

Certified Lurker
New at box building here and I have a question regarding size.

OK Design #1 has 5" woofer with .5 C.F. sealed box. (Numbers somply for demonstration.)

If I decide to do a double-woofer design do I need to double box size?
1 C.F. box with two 5" woofers.

Regarding ported boxes what applies to the port size/quantity?
Two ports same size as for a single woofer box or one bigger one?

Any help much appreciated!

:banana::DCheers:beer::beerchug:
 
Register to hide this ad
Download a box modeling program like WinISD or BoxPlot.

Answer: Yes, double. You have to calc the ports.
 
For an isobaric design, you'd cut the box size in half so it would be .25 cu ft. Although, unless space is at an absolute premium, I don't think an isobaric design is really a good route to go. You are just throwing away output for the sake of a smaller enclosure.
 
When using two woofers, whether sealed or ported, double the box size as compared to one.

For your example, 0.5 cft for one woofer, 1.0 cft for two woofers, 1.5 cft for three.

Also, ports, You can work out a single larger port, but also, if your single woofer ported cabinet required 1 port, say, 1.5" x 2" long, then for two woofers in the 1.0 cft cabinet, you would use 2 ports, each 1.5" x 2" long.
You could do as Zilch said, use a modeling program, and find a 1 port solution.

Isobarik is a concept used in designing some subwoofers, but a 5" is anything but a subwoofer. Using two 5" woofers in an isobarik config would do nothing that a larger woofer wouldn't do better.

But 5" woofers do make excellent two way speakers due to the good extension up into the midrange. And they are great for D'Appolito config cabinets.
 
dnewma04 said:
For an isobaric design, you'd cut the box size in half so it would be .25 cu ft. Although, unless space is at an absolute premium, I don't think an isobaric design is really a good route to go. You are just throwing away output for the sake of a smaller enclosure.
Click to expand...
I believe I read that if an isobarik design is used in a box designed for a single woofer, the bass response will be extended by about 1/2 octave over the equivalent-sized single woofer box.
 
WOW!

Thanks for all the quick replies and good info! :D

Never have heard of isobarik desing so no I'm not considering that.
What is isobarik design?

Thanks again! :banana:
 
In an isobarik, the box is divided internally so that one woofer fires out into open space, and the other woofer in on the middle divider, internal in the speaker. It's sole function is to act in a way as to change pressure in the box section between it and the outer firing woofer so that the other woofer thinks it is in a much larger box.

The woofer that you hear is no louder, but more power is used. The tradeoff is a more complex design and more power consumption in return for a smaller box and lower f3.
 
Paul, it would have the same or very very similar F3, just an enclosure 50% of the size of one required for one woofer. Sometimes, the method in which you wire the two woofers together can result in a bit of a hump and marginally different F3, but in any case, it would be rather negligible.

Isobaric (isobarik) also tends to limit you to sealed enclosures, as port lengths tend to get unweildly in tiny enclosures. Then again, you could always go with a PR. I'll stick by my thought that unless there are serious space concerns, I wouldn't give an isobaric any serious thought.
 
sealy said:
I believe I read that if an isobarik design is used in a box designed for a single woofer, the bass response will be extended by about 1/2 octave over the equivalent-sized single woofer box.
Click to expand...

For the same Qts, it requires half the box size of a single woofer. If you wanted to stay in the same size enclosure, you would have the potential to gain some lowend extension (half octave might be a little excessive of an estimate unless the box started out with a fairly high Qts). I've seen box tuning drop 10-15hz from going from a .8 to a .65 qts with what you are describing, but F3 remains very similar. You do get more bass extension at F6 and F10, though.

Also, someone can correct me if I am wrong but I believe you also lose output vs a single woofer. I think you lose 3 dB right off the bat, 3 more if you wire the two woofer in series. You can gain potentially 3dB back from an amplifier that provides 2x as much power into a load with half of the impedance, but in practice, not as many amps do that as should and the additional resistance added by the wire will always prevent it from ever attaining the same output.
 
dnewma04 said:
For an isobaric design, you'd cut the box size in half so it would be .25 cu ft. Although, unless space is at an absolute premium, I don't think an isobaric design is really a good route to go. You are just throwing away output for the sake of a smaller enclosure.
Click to expand...

With a 5" in a .25cuft enclosure, unless you go with a simple clamshell and have one sticking out in the room you'll probably gain back most of that .25cuft you dropped building the isobaric chamber. IOW you'll end up with structure the size of a .5cuft enclosure anyway with the only real gain being possibly lower distortion.

Ray
 
Thanks again!! :banana:

Great information on the isobaric altho not what I am trying to achieve.


Thanks!

Always plenty of great info on here! :banana:
 
You must log in or register to reply here.
Back
Top Bottom