Cigar Box Bluetooth Speaker

[JonB]

Hi all - new guy here.

I found a cool cigar box that I want to turn into a bluetooth speaker. Internal volume is fixed at 0.077-0.86 cubic feet (larger volume is if I remove the inserts that help seal the lid in a cigar box.) So not a lot of room to work with.

I am hoping to use 2x of Dayton Audio ND65-8 2/12" full range driver or the ND55-4 full range driver. Note: same size, just 8 vs 4 ohm. Also I want to add in the NDPR 2 1/2 matching passive radiator.

Amp: Undecided so far, but probably one of the Dayton Audio 2.x15 or 2x30 bluetooth amp.

Any thoughts / pointers / suggestions on how to proceed? I realize it won't be the best sounding box due to the size, power, etc - but should be enough to sit on the table in the back yard to have some tunes.

Specs on the speakers say 0.03 cubic feet for sealed box volume per speaker, so I am hoping the cigar box has enough interior space (will loose a bit with the amp, wires, etc).

If there is enough room, possibly add the add-on 3x18650 battery pack, but not a hard requirement.

Do-able? Or will sound like crap?

[Chris Roemer]

A pair of the 8ohmers (ND65-8) in 0.08cf, using a pair of ND90-PRs should tune that space to near 80Hz, with a bottom-end reach a bit below that.

OR

Use a pair of port tubes that are 1"id x 9" long. THAT would tune the box into the mid 70s giving an F3 of nearly 60Hz. Cheaper and deeper !

[JonB]

No way to fit a 9" port - I think the box is like 8" long total (outside dimension). So that's why was going with the sealed route.

Never used PR's before. Should I section the box off into two chambers to prevent issues between the driver/pr pair for each channel? In other words, create two chambers, each with 1 driver and 1 PR in each.

[Chris Roemer]

Yes. It would be best for each channel (side) to have its own space for the driver and PR (or port).

Ports CAN be bent. Also, you could get by with a 3/4"id port tube that was 5" long (one for each side).
(In sims - with around 8wRMS, at 70Hz the ported box should be able to play +9dB louder than the PR version.)

[JonB]

Now you have me thinking...I have a well tuned 3D printer and can make a port tube easily enough in different shapes. If that gives a bit more +dB and eliminates the need for the PR's but will still have the same (or better?) overall sound quality.....

[3rutu5]

A pair of the 8ohmers (ND65-8) in 0.08cf, using a pair of ND90-PRs should tune that space to near 80Hz, with a bottom-end reach a bit below that.

OR

Use a pair of port tubes that are 1"id x 9" long. THAT would tune the box into the mid 70s giving an F3 of nearly 60Hz. Cheaper and deeper !

I agree with Chris, i did 1x ND65 with a pair of ND90 prs and went great and bacially doing another project with a ND65-4 paired with a ND90PR on each side and around that 0.034cuft enclosure sizing (each) and floating around that F0 of 75/80hz with the PR being tuned for around 5/10hz lower with a little bit of weight on it. Great driver and really performs out of its skin for something that really is closer to a 60mm driver. If you can fit it, the ND140PR will give you the lower tuning with 30/40grams on the PR, well at least thats what WiniSD was showing me. I really wanted to try it but dont want to increase my build to fit it in.

[JonB]

I agree with Chris, i did 1x ND65 with a pair of ND90 prs and went great and bacially doing another project with a ND65-4 paired with a ND90PR on each side and around that 0.034cuft enclosure sizing (each) and floating around that F0 of 75/80hz with the PR being tuned for around 5/10hz lower with a little bit of weight on it. Great driver and really performs out of its skin for something that really is closer to a 60mm driver. If you can fit it, the ND140PR will give you the lower tuning with 30/40grams on the PR, well at least thats what WiniSD was showing me. I really wanted to try it but dont want to increase my build to fit it in.

Thanks for the info - I’ve seen a couple of your projects on here and dig the creativity. So maybe a newb question, but why the ND90 vs the ND65 passive? I could make the ND90 work by cutting holes in the side of the cigar box (need to measure and double check). I was looking at the ND65 PR as I can fit 2 of them on top along with the speakers. Basically no modification to the box - everything fits with the lid closed. But if the ND90 PR is better option then I can cut into the sides of the box easy enough.

[3rutu5]

Thanks for the info - I’ve seen a couple of your projects on here and dig the creativity. So maybe a newb question, but why the ND90 vs the ND65 passive? I could make the ND90 work by cutting holes in the side of the cigar box (need to measure and double check). I was looking at the ND65 PR as I can fit 2 of them on top along with the speakers. Basically no modification to the box - everything fits with the lid closed. But if the ND90 PR is better option then I can cut into the sides of the box easy enough.

I beleive you need at least twice the SD of the active speaker for it to work properly, so you might need 2x ND65 PR's per driver. Just depends on what you want to get out of it, it was recommended to me to try the ND65's with the DMA45 build i did, but i modelled it in WinSD and liked the graph a bit better with the larger PR. Have you grabbed WinSD to look at the transfer function magnitude for both the speaker/PR combo? .

the yellow line is my current design and im still debating about adding a few grams of washers as it does affect both graphs slightly, but not sure how the PR is affected going under the F0. I did have another option i was once looking at that shows the ND65 with a set of twins ND65 passives with 3 grams of weights on each and you can see how it is similar function for the speaker driver but the passive dip about -4dbs below.

i'm liking the idea of a cigar box speaker as i have a couple i got many years ago in the garage, but using them for other functions i find myself using my various projects in my home office and it gives me a great sense of achievement while i actually do my day job. Just wish i had more ears as that ratio between projects/person is a bit one sided.

[djg]

So organized, sigh.

[JonB]

I appreciate the info on the PR size. I do have WinISD but no idea what I am doing with it yet. My normal ‘tinkering’ hobby is Arduino and other such microcontrollers. This is the first speaker design project so I have a bit of a learning curve to end up with something that lands more on the ‘good’ side of the equation when the project is complete.

I appreciate you guys answering my questions and offering up your knowledge!

[3rutu5]

I started tinkering with a esp module to get an animated gif of.a.cassette going. Got in working and now just need to print the rest haha.

If you are using a similar size feel free to use my graphs or maybe I can send you my project file and you can tinker with it