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Old 4th March 2008, 06:24 AM   #11
Badeck is offline Badeck  Philippines
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Hi,

As a follow up, and using your driver's spec, a sealed enclosure design with a Qtc of 1 would yield a box volume of 1.105 cu ft. with an f3 of 50 Hz. That is without the HR partition.

Then you run a sim for the driver in the calculated volume to get the resulting resonant frequency (the peak in the resulting impedance curve). That is the target frequency for the HR to damp. Plan for a partition placement, then calculate Veff. Veff is used to determine the HR port length, tuned to the resultant frequency above.

When the HR port is tuned to the box + driver frequency, you will notice a single impedance hump centered at the target frequency, but with a lower Q. Q can be further lowered by damping the port openings. The impedance plot can then be used to estimate the resulting Qtc, which would be by then lowered from the value of 1 that was without the HR.


Thanks,

Dexter
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Old 4th March 2008, 06:41 AM   #12
Badeck is offline Badeck  Philippines
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Hi All,

Sorry for the monologue. If it's OK with you, I will upload my actual enclosure impedance plots (before and after tuning) tomorrow.

Please note also that this is not the same as aperiodic design, as aperiodic blindly targets damping (plus it vents outside the enclosure) while the internal HR selectively targets the box resonant frequency.

Thanks,

Dexter
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Old 4th March 2008, 03:42 PM   #13
dre7 is offline dre7  United States
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Thanks, DCRs are something I know little about. Most of my BR experience comes from poor sounding consumer grade stuff.

I also have a pair of SP8Bs rescued from the dumpster, and IIRC that what Augspurger used in his original design. Wish I could find a link to his article. That way I can judge on the merit of the design and not have to blame my math skills

Andrew
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Old 4th March 2008, 04:00 PM   #14
sreten is offline sreten  United Kingdom
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Default Re: EBS with high qts ceiling speaker?

Quote:
Originally posted by dre7

I'd like to try them in a bass reflex. The Qts is less than ideal (.7) and when I model them in WinISD beta, it suggests a very large enclosure (7 cu ft.) tuned well below the driver Fs. The plot shows a slight "hump" at the frequency the port's tuned to. Is this an EBS design and would it be worth building? Here's the info on the driver

Andrew
Hi,

The short is No, it is not an EBS and No, 7cuft boxes would be pointless.
Open baffle with another driver or subwoofer is likely your best bet.

/sreten.
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Old 5th March 2008, 04:08 AM   #15
GM is offline GM  United States
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Quote:
Originally posted by dre7

So you're saying a (roughly) 25x11x19 enclosure moved back towards the wall would do me?

Or would a terminus close to the floor (hardwood with area rug in front) be preferred?
You're welcome!

??? You're putting a ~full range driver into a box height better suited for a sub? I designed the TL to put the driver at ~seated ear height. Regardless, TLs benefit from floor loading, though with such a short height I doubt it matters much where you put the terminus short of down-firing.

GM
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Old 5th March 2008, 04:49 AM   #16
dre7 is offline dre7  United States
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GM

You're absolutely right, that's probably carrying WAF a bit too far.

Actually, what you're proposing is a larger scale version of some 1/4 wave pipes I made for the PE 269-469 which I have on either side of my desk as computer monitors. And yes, considering the small footprint and placement close to the rear wall, they won't be nearly as intrusive as the old speakers.

Plus it can be done with one sheet of ply. Right on! I'll give it a go.

Andrew
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Old 5th March 2008, 03:05 PM   #17
GM is offline GM  United States
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Please let us know how they perform as I'm not familiar with this brand and others may be interested too.

GM
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