I've got no experience of EBS designs but Brian Steele has some rules of thumb on his website:
http://www.diysubwoofers.org/prt/ported5.htm
Nice one,
David.
http://www.diysubwoofers.org/prt/ported5.htm
Nice one,
David.
Hi,
Some 10 years ago I experimented a lot with EBS (electronic bas extension) for closed boxes. I did not get satisfying results with the Linkwitz transform. It turned out to be very sensitive to component tolerances and it lacked the opportunity for tuning. I came to a more basic approach that worked very well. The test box consisted of 2 x Visaton GF200 in a 40 L box and was tuned to 30Hz at a total Q of 0.5. The final circuit has more components than the Linkwitz transform but it is much easier to handle and to calculate.
Here you can download some basics behind the work and an Exel worksheet to predict what will happen (250 kb zip file). Please don’t blame me for some typo and grammar errors. It was intended as a quick and dirty engineering note for private use.
In the Exel sheet simply fill in the speaker unit parameters, the box volume and the number of units used in the box. Qe is optional, it is only used for calculating EBP. That’s all there is. In practice you cannot lift the speaker response more than 9 dB to 12 db at the new targeted -3dB frequency.
Note, this equalisation is only for closed boxes. I see no use for BR boxes to extend them electronically.
Have fun, cheers
Some 10 years ago I experimented a lot with EBS (electronic bas extension) for closed boxes. I did not get satisfying results with the Linkwitz transform. It turned out to be very sensitive to component tolerances and it lacked the opportunity for tuning. I came to a more basic approach that worked very well. The test box consisted of 2 x Visaton GF200 in a 40 L box and was tuned to 30Hz at a total Q of 0.5. The final circuit has more components than the Linkwitz transform but it is much easier to handle and to calculate.
Here you can download some basics behind the work and an Exel worksheet to predict what will happen (250 kb zip file). Please don’t blame me for some typo and grammar errors. It was intended as a quick and dirty engineering note for private use.
In the Exel sheet simply fill in the speaker unit parameters, the box volume and the number of units used in the box. Qe is optional, it is only used for calculating EBP. That’s all there is. In practice you cannot lift the speaker response more than 9 dB to 12 db at the new targeted -3dB frequency.
Note, this equalisation is only for closed boxes. I see no use for BR boxes to extend them electronically.
Have fun, cheers
Oops, I intended: “In practice you cannot lift the speaker response more than 9 dB to 12 db at the very low frequency end.”
That means the total gain of the correction filter cannot be more than 9 db tot 12 dB at DC.
(He why is editing this in the original post impossible after a some timeout?)
Guys,
The last three posts have been about electronically assisted alignments.
EBS is an unassisted alignment. I think the term was coiined by the makers of LEAP, but in common usage it is essentially any vented box that is rather larger and tuned rather lower than a typical QB3 alignment. It exhibits a droop in the area above tuning that flattens out into a shelf as you go down in frequency.
There used to be a write-up about almighty subwoofers (or something like that) which illustrated the concept rather well.
Brian Steele's write-up is also a good one.
The last three posts have been about electronically assisted alignments.
EBS is an unassisted alignment. I think the term was coiined by the makers of LEAP, but in common usage it is essentially any vented box that is rather larger and tuned rather lower than a typical QB3 alignment. It exhibits a droop in the area above tuning that flattens out into a shelf as you go down in frequency.
There used to be a write-up about almighty subwoofers (or something like that) which illustrated the concept rather well.
Brian Steele's write-up is also a good one.
As already noted, it's mostly a rule-of-thumb design. I've built many EBS designs over the decades, but before I got on line /the early basslist, I knew them as X-bass alignments, which have worked well for me. I've tried the more extreme shelf versions, but prefer these for most apps.
Where Qt is the total Q of the system:
Vb = 7.95*Vas*Qt^2.21
Fb = 0.471*Vas*Qt^-0.677
Qt is < 0.366:
F3 = 0.21*Fs*Qt^-1.46
Qt is > 0.366:
F3 = 0.33*Fs*Qt^-1.01
GM
thanks GM. i had built a pair of EBS speakers many years (1988) ago without realising what EBS was. I had built a box that was about 50% larger than that specified by the manufacturer (70 instead of 45 liters). then tuned the port by ear (dia was fixed at 4"). i never had any way of knowig how to calculate what sounded to my ear was the deepest bass. I never did measure the bass but these the MTM using 2 8" Focal woofers (8N515) reproduced most rock music at quite high levels. thanks for the formulae.
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