Inspired by other threads, I designed my own version with two 12" car subwoofers. I plan to use it near field. I am curious how high it can play, I would like it to match my dual 3FE22 sealed boxes, which start rolling off around 150 Hz. Or my "Kallax" synergy horns, which should play even lower when finished. 18mm MDF, just large enough to fit the woofers. The chamber inserts are cut in parts to save material. I just need to cut one more side panel with a saw. I am curious how it will turn out.
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cool.
keep those drivers as close together as possible and keep he cavity also small (pushes standing waves out of band).
I would mount them push pull, but that's just my opinion.
keep those drivers as close together as possible and keep he cavity also small (pushes standing waves out of band).
I would mount them push pull, but that's just my opinion.
I glued together the chamber. I thought that the pin holes were in the center, but apparently they were not🙂 Nothing that a bit of filler and sanding would not fix. And this part will not be visible anyway.
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So you put that slot into a sealed box section on the outsides?
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The drivers will be mounted like this,but the backs will be open - like here: https://www.audiocircle.com/index.php?topic=54844.20
That project was the main inspiration.
That project was the main inspiration.
Great idea.
If you manage to keep the distance between your head and the slot on the same order of magnitude (or smaller) than the dipole separation distance, then there is no complete 6 dB / octave loss for you, while there is for the neighbours and for excitation of room modes. This principle is used in some 'noise cancelling' microphones.
https://www.cuidevices.com/product-spotlight/electret-condenser-microphones
If you manage to keep the distance between your head and the slot on the same order of magnitude (or smaller) than the dipole separation distance, then there is no complete 6 dB / octave loss for you, while there is for the neighbours and for excitation of room modes. This principle is used in some 'noise cancelling' microphones.
https://www.cuidevices.com/product-spotlight/electret-condenser-microphones
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![10b[1].png](/community/data/attachments/946/946738-744b4549734d75fa1216f61da789e39d.jpg?hash=dEtFSXNNdf)
Yes, it looks pretty smart and is easy to build. Among others, also cowanaudio recommends this arrangement for apartment listening.
There is a very good chance this sub will operate well to above 150Hz, but it will be easy to locate if it is behind you. I could hear where my OB sub was with a 100Hz crossover frequency. At 80Hz I couldn't tell. Try placing your sub in front of you in an ottoman type arrangement.
Looks good. Thanks for sharing the build and posting the photos.
Going for 150Hz looks easy with 12" drivers? Assuming its mainly based on slot depth 1/4 wave resonance a slot depth of 13" looks good for over 250Hz.
Even an 18" with some cunning corner cutting might do 200Hz?
Going for 150Hz looks easy with 12" drivers? Assuming its mainly based on slot depth 1/4 wave resonance a slot depth of 13" looks good for over 250Hz.
Even an 18" with some cunning corner cutting might do 200Hz?
Hmmm, that is a long and narrow slot. To me it looks like you are going to get something more along the lines of "peaky" than "peachy". Take some measurements in the nearfield to show us how the FR looks. Sometimes these Ripole resonance peaks can be very promonent and you need to cross over much lower (more than an octave). I would be curious if a notch filter will suppress it sufficiently, since high Q resonances can be stimulated by out of band energy (e.g. like blowing on a coke bottle).
See this related post for an example of the peak in a 12" Ripole. The resonance peak is around 20dB tall without filtering. You can see how low in frequency a crossover rolloff was necessary:
https://www.diyaudio.com/community/threads/ripole-with-15-woofers.366261/post-6494383
See this related post for an example of the peak in a 12" Ripole. The resonance peak is around 20dB tall without filtering. You can see how low in frequency a crossover rolloff was necessary:
https://www.diyaudio.com/community/threads/ripole-with-15-woofers.366261/post-6494383
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I will give it one coat of paint and then install the drivers for the first near field measurement without the back covers.The slot size was chosen to provide some loading and I hope it moves the Fs a bit lower. Looking at the Ripole, my slot is relatively smaller and with lower volume, therefore I would expect the resonant things to be higher in frequency.
Just wondering if you have made the measurements and would be willing to post them. It would be great if you had nearfield measurements (at the plane of the opening) taken both in front of the slot and the opposite side. A far field measurement would be great but this is not easy for subwoofers without a lot of room response as well.
Not yet, sorry. I wanted to measure outside and the weather was not suitable in the last week. They are room roughly painted and tomorrow I will install the drivers, need to buy shorter screws. I hope I will have some time for myself during the Easter break, there are lots of visits planned for it though.
I have the drivers mounted and tried to play some sound. This thing really blows air out of the slot. I hope to make in room nearfield measurements tomorrow, just to see what it is like.
That's not too bad if you can listen really, really close. Moving out to even 18" will probably result in some dipole cancellation pulling the low end down. How "near" do you plan to use it?
In any case if you notch out the peak around 210Hz and cross over lower, e.g. 125Hz, it will work out OK. The high Q of the resonance may still resonate slightly even with out of band content, but I doubt you will notice too much.
In any case if you notch out the peak around 210Hz and cross over lower, e.g. 125Hz, it will work out OK. The high Q of the resonance may still resonate slightly even with out of band content, but I doubt you will notice too much.