Hello all,
Please see the attached photo. I'm building another (smaller) portable speaker and before I begin chopping up wood, milling aluminium and soldering boards together I want to get peoples opinions on isolating the left and right mid/full range drivers from the 'subwoofer' in the centre. I have had good results having two fullrange drivers in the same acoustic space driving stereo but I have no experience of the arrangement in the photograph.
In an ideal world I would always isolate mid from low acoustically, but in this design I am struggling to keep to my final dimensions and achieve that (with the drivers I would like to use). The speakers are individually amplified and fed from a SigmaDSP so any signal processing I require is at my disposal.
Any suggestions? Do you think I can get away with it? My main thought is that the back pressure of the woofer may cause the opposite excursion in the L & R and cause them to hit Xmax. The large passive radiator at the rear may help with this though.
Please see the attached photo. I'm building another (smaller) portable speaker and before I begin chopping up wood, milling aluminium and soldering boards together I want to get peoples opinions on isolating the left and right mid/full range drivers from the 'subwoofer' in the centre. I have had good results having two fullrange drivers in the same acoustic space driving stereo but I have no experience of the arrangement in the photograph.
In an ideal world I would always isolate mid from low acoustically, but in this design I am struggling to keep to my final dimensions and achieve that (with the drivers I would like to use). The speakers are individually amplified and fed from a SigmaDSP so any signal processing I require is at my disposal.
Any suggestions? Do you think I can get away with it? My main thought is that the back pressure of the woofer may cause the opposite excursion in the L & R and cause them to hit Xmax. The large passive radiator at the rear may help with this though.
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Hey Edd...
If two speakers share an acoustical space, but not the identical signal, there's interesting complexity. First, there's the possibility of the back wave from driver A travelling out through driver B. I've seen some really super cheap speakers do this when a midrange and woofer share the same space. Ugh.
Then there's an acoustical and electrical interaction that will take place. If the amplifier uses any sort of feedback in the output stage at all, it will attempt to correct for any signal coming from any other speakers in a shared space, so you have wasted power and overall a complicated interaction.
Best,
E
If two speakers share an acoustical space, but not the identical signal, there's interesting complexity. First, there's the possibility of the back wave from driver A travelling out through driver B. I've seen some really super cheap speakers do this when a midrange and woofer share the same space. Ugh.
Then there's an acoustical and electrical interaction that will take place. If the amplifier uses any sort of feedback in the output stage at all, it will attempt to correct for any signal coming from any other speakers in a shared space, so you have wasted power and overall a complicated interaction.
Best,
E
Erik, thanks for your comment. I hadn’t thought about feedback power issues. Efficiency is always a big consideration in my battery based designs.
J, well spotted on the drivers. Especially considering that the ones in the model are just a my quick rough sketch to approximate volume and mounting. I haven’t tested the combo yet but I have high hopes.
I did think of using the single woofer with a pair of tweeters that cross fairly low, but considering that directionality of audio begins way down at around 400Hz I don’t think the stereo effect would be strong enough.
Now I’ve got to try and squeeze a couple of back chambers behind the mids in CAD!
J, well spotted on the drivers. Especially considering that the ones in the model are just a my quick rough sketch to approximate volume and mounting. I haven’t tested the combo yet but I have high hopes.
I did think of using the single woofer with a pair of tweeters that cross fairly low, but considering that directionality of audio begins way down at around 400Hz I don’t think the stereo effect would be strong enough.
Now I’ve got to try and squeeze a couple of back chambers behind the mids in CAD!
You could probably find PVC plumbing end-caps that would fit over the L/R drivers nicely, and would cost less than the 3D print material..
Just to follow this one up, I ended up designing a custom enclosure that seals around the back of the drivers while still using their original mounting screws to secure it. This will mean fewer visible bolts from the front panel.
I do not have a 3D printer (yet) but I have been quoted £10 a part to have these printed locally in ABS, which I think is great.
I need to do some back and forth between CAD and speaker simulation software to finalise the dimensions, but at the moment the isolators have an F3 of around 330Hz.
I do not have a 3D printer (yet) but I have been quoted £10 a part to have these printed locally in ABS, which I think is great.
I need to do some back and forth between CAD and speaker simulation software to finalise the dimensions, but at the moment the isolators have an F3 of around 330Hz.
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