Ideal speaker box size for...

grafxdesin

grafxdesin

AK Subscriber
Subscriber
I am building a second speaker box (basically a boombox) for a pair of speakers and a 25w amp, my original box was a cigar box and was my first build. It was a lot of fun but now I need to build a nicer looking better fitting box. The speakers I am using are 2 HiVi B3N 3" and a 25w amp from parts express. If someone can help me figure out the proper or optimal box size for these that would be greatly appreciated. I am looking to keep these portable as well, both speakers in the same box. (boombox)

http://www.parts-express.com/hivi-b3n-3-aluminum-driver-round-frame--297-428
 
The main thing is that without an active highpass filter, you will tend to get lots of distortion at relatively low volumes with those. To increase power handling, you want a smaller, sealed box, stuffed well. I'd say 2 liters per driver max, 1 liter for the smallest where you still almost reach the bass range, 0.5 liter per driver for maximum clean output (around 6dB more than 2 liters).

They will also sound pretty thin/bright unless you add a filter circuit according to your baffle dimensions, especially outdoors, but that will cost you more SPL so you may not find it worth it. That's just kinda how it goes with 3" speakers, though.
 
I never have a problem putting in a order with parts express, any tweeters or other speakers that could help out these drivers?
I also have a 6" panasonic woofer that I took out of a sub that I could use, nothing speacial but if I filter the highs to the 3" and the lows to the woofer, might work and be fun to do.
 
For 2-way you're really better off with something else (because you can get either more bass, or more output, or a little of both). The thing is, crossovers are difficult, and you don't really get more bass without more cabinet, so really there's nothing wrong with your dual 3" plan for what you're describing - the issues I mentioned apply to any small speaker.

I don't own the B3N, but there are enough measurements around that I can try to help you figure out an adjustable filter to try if you want. You'd have to figure out your box dimensions first. Making it slim on the speaker baffle side will make the filter parts a little cheaper.
 
dumptruck said:
For 2-way you're really better off with something else (because you can get either more bass, or more output, or a little of both). The thing is, crossovers are difficult, and you don't really get more bass without more cabinet, so really there's nothing wrong with your dual 3" plan for what you're describing - the issues I mentioned apply to any small speaker.

I don't own the B3N, but there are enough measurements around that I can try to help you figure out an adjustable filter to try if you want. You'd have to figure out your box dimensions first. Making it slim on the speaker baffle side will make the filter parts a little cheaper.
Click to expand...

I plan on building the box myself, so we can go any size, but I need help with the size part. Any help is greatly appreciated.
 
Sounds good to me. Post your cabinet design here if you want suggestions for a passive filter. Btw, be careful not to go too thick with the baffle if you can't cut chamfers/recesses out of it to vent the back of the driver - not much room behind the cone.
 
So I am thinking 12" width, 6" height, and 5" depth, that is 360 cubic inches or .2 cubic feet. I plan on adding a small vent on the back of this. I could go larger but what would I gain by that? The spec for them on partsexpress.com say .28f3 for vented.
Suggestions, comments?
 
I suggested an undersized sealed box for reasons I already explained. The only potentially useful thing you can do with a vented box is to go much, much larger (around the 0.28 ft³ per driver) size on the PE page.

That's really a terrible idea on paper due to super low power handling and loads of distortion, but it might have some appeal for a low power portable... I'd have to simulate it all the way with the driver response and a baffle. I am kind of curious about something, maybe I'll try it later today.

Btw, the PE "cabinet recommendations" are just numbers kicked out of a simulator on default settings. Nobody is actually checking what the response looks like, the excursion / power handling, whether a highpass would be needed, etc.
 
Ahh i forgot that is per driver, well my original size was 10x6x4, that's 240 cubic inches and more in the range of what you suggested. I will keep it sealed as well, this is more of what you where suggesting correct?
 
Yes, just remember it's internal volume, and little subtractions (amp, internal crosspiece, hardware, the speaker magnets, etc.) add up quick in a tiny cabinet.
 
dumptruck said:
Yes, just remember it's internal volume, and little subtractions (amp, internal crosspiece, hardware, the speaker magnets, etc.) add up quick in a tiny cabinet.
Click to expand...
That is true, maybe I will make it a touch wider in the back to make up for that, you also mentioned a passive filter, any you suggest? What would the benefit of this be?
 
In the Parts Express description of the drivers the Optimum Size Cabinet Volume is given for sealed and vented. If you want to calculate the dims., just go to www.diyaudioandvideo.com and you will find all kinds of calculators including one where you input dims and it will calculate what volume will those dims give you.

From what I have read filters are not necessary with this HiVi driver, but might be needed and dumptruck is on to something. If you build the appropriate enclosure the lows are very nice for such a small size, the highs only go up to 7 kHz, which is below the frequencies most humans can hear, so you would feel that there is something missing, so consider a small tweeter to take over where this driver falls short. IMO, I would use a tweeter and do a simple first order crossover crossing at 5500 Hz, using a 3.9uF cap and a 0.25mH inductor, and add an LPad (4.3 and 6.5 Ohm Resistors), so the tweeter does not overshadow the very nice HiVi driver.
 
grafxdesin said:
That is true, maybe I will make it a touch wider in the back to make up for that, you also mentioned a passive filter, any you suggest? What would the benefit of this be?
Click to expand...
Here are simulations on an approx. 12"W x 7"H baffle, as if outdoors/away from walls at a distance. The dashed lines are the unfiltered drivers in the cabinet. The solid lines are with the filters (one filter circuit per driver). In the boombox layout, there will be a lot of comb filtering in the 500-3kHz range if you move off-axis more than a tiny bit, which might mess with what sounds subjectively "right". Anyway...

Quick & dirty version. Simply adjust resistor value until it sounds best (change it in approx. multiples of 2, eg. 12Ω, 50Ω, etc.). If you plan to use it mostly outside, check your decision outside:

attachment.php




Fussy version. It is very difficult to get a high frequency EQ like this to work without measuring and adjusting as needed, but I tried to come up with something a little easier to hit than that one Zaph did. Adjust for more/less brightness same as the first version (using the 12Ω resistor here):

edit: changed my mind - make the 0.68uF be 1.5uF instead for the first filter here, and in the second use 40Ω instead of 30.
attachment.php
 

Attachments

  • filter1.gif
    filter1.gif
    29.4 KB · Views: 37
  • filter2.gif
    filter2.gif
    30.2 KB · Views: 35
Last edited:
I'm curious about that Eq network..

Could you point me to some tutorial, or to some info about how it works, and how to calculate the values?
 
Just look up "parallel notch filter". The resistor drops the output, while the inductor lets LF skip past the resistor and likewise for HF through the capacitor.

Here's the electrical response of the second filter I posted. You can see how it's one very broad notch filter, and then a little narrow one on top of it:
attachment.php


Come to think of it, I should have used more like 1.5uF for the first cap in the second version, so it isn't pulling down the top octave at all.
 

Attachments

  • filter2_elec.gif
    filter2_elec.gif
    9.9 KB · Views: 20
You must log in or register to reply here.

Similar threads

grafxdesin
Small stereo speaker help.. dimensions and drivers
Replies
5
Views
388
westend
westend
P
Box size on unique build
Replies
6
Views
556
Poindexter
Poindexter
grafxdesin
Building Sub with 3" speaker for Minimus 7's
Replies
3
Views
188
1108
1
grafxdesin
DIY Line Array Questions
Replies
1
Views
255
evsentry3
E
H
Speaker box dimensions
Replies
1
Views
1K
lndm
L
Back
Top Bottom