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Multi-Way Conventional loudspeakers with crossovers

Box in a box speaker
Box in a box speaker
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Old 26th August 2020, 09:39 AM   #1
cracked case is offline cracked case  England
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Default Box in a box speaker

I just thought that I'd share an idea for reducing the transmission of vibration from the driver to the enclosure, comments welcome. 1 is the bass enclosure, ( with aperiodic loading ), 2 is the tweeter box and 3 are the spring things that hold them against the front baffle ( with foam gaskets between ) . IMG_20200826_102247.jpg

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The " tweeter " is a full range GAOHOU 52mm 4Ohm driver that has an output that rises above 2,000 Hz, so making the crossover easier. The bass driver is a cheap 6" paper from Maplin (RIP ).
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Old 26th August 2020, 10:00 AM   #2
ewollowe is offline ewollowe  Australia
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Very interesting design
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Old 26th August 2020, 05:37 PM   #3
GM is offline GM  United States
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Old 27th August 2020, 06:47 AM   #4
cracked case is offline cracked case  England
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Old 12th October 2020, 07:04 AM   #5
cracked case is offline cracked case  England
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A bit of an update on my box in a box speakers, I've reworked the crossover, it now has three iron core inductors for the mid/bass the rationale behind this was I was originally going to have 4, my thinking if you double the turns of an inductor the inductance goes up as the square, so instead of one, you double the turns and have four in parallel, twice the turns would double the DC resistance but four in parallel would half if, if that makes sense. But I only had funds for three pairs at the time. Combined they have a DC resistance of 0.2 Ohms; more than I'd like, perhaps I'll strip a battery charger ( or microwave ) transformer and make a hefty E core choke. Anyway, now that I've listened to them for a bit I'm well impressed. I was listening to Rodrigo and Gabriela, who use their guitars more like percussion instruments and the incredibly rapid tapping was conveyed by the BIAB speakers incredibly well. They certainly aren't perfect ( they were meant as purely a crude proof of concept, and they certainly do that; however the finish is pretty bad, the springy things take up to much space reducing the amount os internal bracing and the drivers are cheap. The tweeter is feed by two motor run polypropylene caps and a 4 Ohm resistor ( bypassed by a .33 uf cap negate the roll off of the driver ), this is not ideal, I'd prefer about 10 smaller value caps in parallel. Encouraged by this I'm considering another, possibly using two Dayton audio TCP115-8 4" drivers with a ceramic driver from a mini x speaker as a tweeter. If you have any ideas yourself please let me know. I've gained new respect for the CD format, my Sanskrit 10th DAC, my class D amp and much, much more for the musicianship of Rodrigo and Gabriela.
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Old 19th January 2021, 09:46 AM   #6
cracked case is offline cracked case  England
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I am currently constructing some experimental speakers to see if two bass boxes back to back will reduce cabinet vibration, as my previous box in a box speaker does have some vibration in the side panels, although this could be due to inadequate bracing. 1 is cork between the outer 6mm mdf and 1/8 ply wood, this DOSEN'T work, I was hoping it would have a dampening effect but it makes no difference. 2 is 45 deg baffle braces; these do work, increasing the frequency of resonance from 1,658 Hz to 2,806 Hz, and hopefully introducing some level of deffraction.
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Old 22nd January 2021, 06:54 AM   #7
cracked case is offline cracked case  England
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Although there is still some work to do on them I had a listen to them last night; the whole idea was to be able to rest my hand on the speaker with music playing and being unable to feel ANY vibration what so ever, unfortunately this goal has not been achieved. I think in hindsight that I should have just used an extra piece of 6mm mdf instead of the cork and thin ply on the inside as this would have made it much stiffer and it seems to be that this is the place where the cabinet is flexing. Whilst the primary goal was not achieved, at least they sound decent for small speakers based on two 2 1/2" drivers - they sounded quite good playing Kraftwerk, even though they could do with a bit more running in. It was my idea to use these to test the principle and then make a two way with two 4" drivers back to back, then perhaps a pseudo three way with two 6x9" car drivers back to back, however as I can still feel flex in the cabinet, I'll have to think on making the enclosures MUCH stiffer. I may try gluing an extra piece of 6mm mdf to the outside of these to see if it makes a notable difference. The drivers are wired in parallel ( 8 ohms each ) with 1.9 mh choke for the rear.
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Last edited by cracked case; 22nd January 2021 at 06:56 AM.
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