Can't figure out Zaph's design...

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(Yes, I've used the search function...)
Anyone here must have built John Krutke's low diffraction box for the TB 871 driver?
http://www.zaphaudio.com/audio-speaker11-box3.gif
Basically, I wonder how the baffle detail would look from behind.
If I would stand inside the box and look out through the driver, how would the box look?
I've attached a image with my questions marked out.
Any help would be much appreciated.
Thanks / C.J
 

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That's actually a very good question. The reason that dimension is shown isn't very clear.

Basically, the hole in the 2nd baffle layer starts out as a straight thru hole of 4.38" diameter. Then I used a 1/2" chamfer bit to chamfer the rest of the inside.

That little flat area you see is where the ball bearing for the chamfer bit went around. That is why it's not a straight chamfer, the ball bearing needed a surface to ride on.


Ps. If anyone needs a pair of these enclosures and lives in the US, I have an ugly pair here which I will give away for free as long as shipping is paid for. They are black truck bed liner finish, with whispermat damping inside. They are not the best looking but they work.
 
Thank you for the quick answer!
If the hole in the first baffle layer starts out with a diameter of 3 inches, and is chamfered at an angle of 45 degrees,
that must mean that the hole ends with an diameter of 4.5 inches (increments 0.75" at each side.)
But the 2nd baffle layer hole starts with a diameter of 4.38". I'll guess this mean the inside angle is not exactly 45 degrees, but somewhat less.

I'm sitting far out in the swedish woods...for these things, internet is just perfect.

PS. Any plans on putting that cheap 8" subwoofer design online? Or maybe drop it in my mailbox :) ?
 
cjnordquist said:
PS. Any plans on putting that cheap 8" subwoofer design online? Or maybe drop it in my mailbox :) ?

There's a reason I chose not to put that design online. Mainly, I think the general public would find that it does not have enough output. It goes very deep and sounds excellent, but I've heard a few complaints from people who were disappointed with it's low output. (even though I warned about it on the web page)

For a better, smaller and louder option, see the attachments on the end of my post here.
 
diyAudio Member
Joined 2004
Zaph said:


There's a reason I chose not to put that design online. Mainly, I think the general public would find that it does not have enough output. It goes very deep and sounds excellent, but I've heard a few complaints from people who were disappointed with it's low output. (even though I warned about it on the web page)

For a better, smaller and louder option, see the attachments on the end of my post here.

I suspect its because its actually naff outside of a curiosity.

Bass is a funny old thing... well actually it isn't, its contradictory :)

I have a love hate relationship with bass, when its good you really know it, very very few systems do it exceptionally, quite a few do it well.

An 8" isn't really ever going to reach down and provide you with what I'd call realistic levels of bass. 15" minimum for that exceptional bass with a good design for your chosen alignment.

Anything over 20% THD at 20hz 90dB isn't acceptable IMO as far as top notch sub-bass goes. For an 8" driver it wouldn't be uncommon to see 200-300%+++ harmonic distortion.
Other more important factors also come into play such as power compression, the harmonic breakdown and the energy time frequency spectrogram when measuring a subs performance.

Take a look at some test a few of us got together and did with commercial subs here:

http://www.avtalk.co.uk/forum/index.php?t=thread&frm_id=50&rid=0&SQ=0

Virtually all the Velodynes including the DD18, HGS18 and SPL series were tested along with the Paradigm Reference Servo and powercube10, Plus quite a few others from Rel, SVS and the like.

Frequency plot, THD by component and sum of components, power compression, group delay and ETF spectrograms were all the main tests for each sub.

If you look at the small 8" and 10" subs they were all pretty terrible including the expensive rip off's from Rel.
 
ShinOBIWAN said:
An 8" isn't really ever going to reach down and provide you with what I'd call realistic levels of bass. 15" minimum for that exceptional bass with a good design for your chosen alignment.

Well, people who buy 8" subwoofers aren't looking for or expecting 90dB at 20Hz. In most cases, they aren't even expecting much more depth than 40 hz, and just enough output to keep up with their minispeakers.

15" as a minimum is too excessive, in my humble opinion. Of course it all depends on what an idividual considers exceptional. I have a 15" sub and a 500 watt amp right now and I rarely exceed a mm of excursion even though I have +/- 20mm available. I'm probably going to get rid of it and go with a more reasonable setup, not to mention something a little smaller than 5 cubic feet.


mazeroth said:
Zaph, any idea how much shipping will be to 43026?

If it's reasonable, I'll take dibs :D

Thanks!

I'm at work right now, but I would guess maybe 10 lbs total in a box of maybe 10 x 12 x 18. That should give enough room for some safe padding. I'm in 54915, Appleton, WI. Anything roughly close to the correct shipping charge is fine by me. If you want them, I'll send you my paypal address.
 
diyAudio Member
Joined 2004
Zaph said:


Well, people who buy 8" subwoofers aren't looking for or expecting 90dB at 20Hz. In most cases, they aren't even expecting much more depth than 40 hz, and just enough output to keep up with their minispeakers.

15" as a minimum is too excessive, in my humble opinion. Of course it all depends on what an idividual considers exceptional. I have a 15" sub and a 500 watt amp right now and I rarely exceed a mm of excursion even though I have +/- 20mm available. I'm probably going to get rid of it and go with a more reasonable setup, not to mention something a little smaller than 5 cubic feet.

I wouldn't call any box with an 8" a subwoofer. Low bass more like and for this to have a use I'd say your mains would have to be pretty tiny. A PC sub maybe?

Also you don't need huge enclosures even with large drivers, if your smart about your driver choices and EQ.
 
ShinOBIWAN said:
Also you don't need huge enclosures even with large drivers, if your smart about your driver choices and EQ.

I would still prefer that large drivers be placed in large enclosures, unless they are feedback controlled.

Basically, I feel that swept cone volume needs to be a certain minimum ratio of enclosure volume to avoid distortion resulting from non-linear internal air pressure/vacuum. Not an issue with feedback control, but placing a driver in a tiny box, EQ'ing it back to flat generally results in distortion. I hear that kind of distortion often in large Xmax commercial subs used in typically smallish boxes.

Anyway, this isn't a thread meant to debate subwoofer issues, so I will bow out gracefully here.
 
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