Plan ! - D-20 (hz) Macro Sub ..tapped horn by moi.

NOTE (due to some confusion on another thread): SOFTWARE NOT CALLIBRATED FOR SPL AT MIC YET, THE NUMBERS ON THE CHART ARE JUST THE ONES THE SOFTWARE CHOSE. ALSO DUE TO THE FACT THAT TOTALLY FIXED DRIVE LEVELS & MEASUREMENT LOCATIONS WHERE NOT STRICTLY USED, THE SLIGHT CHANGES IN LEVELS ARE NOT REPROSENTATIVE IN SHIFTS OF SENSTIVITY & OUTPUT LEVELS (YET).

heres a neat little something, ever wanted to experience freqs well below the typical 30hz region, with very low distortion ? :)
and have an easy build which isnt going to cost much, or take too much skill, time or space either ?
well, then this maybe of interest to you.

ever wondered what 22hz or so at high spl feels like ? its weird, kind of makes you nausious sometimes.. but oddly you just arent as physically aware as with 30hz. you do however notice when you try to speak in the middle of such a continuious tone, it modulates your voice like someone beating on your chest ! ..this is something like a combination of the pressure difference between lungs and outside air modulating layrinx & ears being effected in one way or another by the tones. very odd, and something to experience ;)

was designed for a friend who wanted to have a sub which could drop to round about 20hz, whilst not costing alot.. for use with his home hifi.
these cabinets are ideal for use in home hifi/cinema & would hide very nicely under those side wall chairs in pubs :)
best used flat on one side on the floor, followed secondly by corner loading upright.


this design is free for personal, non commercial use..
if you want to make more than 4 of them for business uses, let me know and we'll work something out ;)


This design is largely experimental 'tapped horn',
its unusual in inverting the taper of the horn to trade a little efficency for a lower cutoff ..from 30hz odd to 20hz odd :)
I feel it can yet be improved on, thus im leaving it open for forum users to tinker with.. and i will be doing so when i get back round to it too.
at the state of refinement i got this sub to, its good down to 22-24hz'ish with full output & its got a dip in the 50hz region (but is crossed to a system capable of this).

experiments revealed the following:
* a solid exit plank emphasised the lower cutoff, but supressed the upper frequencys.
* no exit plank removed the gain in the lower frequencys we wanted !
* a slotted exit plank seems to find a balance between the two.
* use of wadding seems to prevent some honking issues & also lowers the fc nearer to its predicted cutoff.

characteristics of this cab:
* radiation will be mostly omnidirectional.
* senstivity will be modest, but stacking multiples may well increase this & lower fc further.

further fiddling with the design may well get it even closer to predictions, if you build these.. let us know :)

Also as noted by another horn builder making more conventional tapped horns, some drivers didnt behave quite as predicted & he found that for some bizzare reason, some worked better than others ! ..notably he also saw the dip in the 50hz region with some drivers, then not others..
this design uses the lab-12, so if you have other reasonable excursion 12" drivers ..experiment ! :)

also, assuming the response is flattened overall, then pending a little parametric to tame some of the top end spikes, they should be good for x-over at 80hz or so too :)




Edited by nineleaves - 25 March 2009 at 2:18pm

now i do........

if i get time, i may.
though the point of the project was seeing just how small a box you could get clean '20hz' out of at decent s.p.l. ;)

problem with using other drivers, is that the box will prefer them to have lower resonant freqs to work properly.. no harm in trying, however to ensure that it will actually drop low.. its highly adviseable to ensure they have a low resonance. most large bass drivers are barely below 30hz.


im sure someone else will scale these up for larger drivers, if so.. let us know how that goes :)

Edited by nineleaves - 11 March 2009 at 8:20pm

I expect the Karlson people will be all over this in a bit . Very useful info.

Looking good.

Just to put my mind at rest, is that HR running on a mac. Out of curiosity, what measurment package are you using?

Thought so (ARTA).

Thanks for the info. I believe a certain European member was on here a while back discussing tapped horns and Karlson (the infamous air coupler design...). Can't remember the link. They are similar due to the mouth arrangement.

Yeah. djk I believe tried to model the effect in Akabak a while back, can't remember if it gave any conclusive results or not, But the karlsonites of this world have something new to look to now.