Dual 8" tapped horn = TH-SPUD - diyAudio
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Old 5th December 2008, 08:32 PM   #1
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Default Dual 8" tapped horn = TH-SPUD

Danley sound labs is introducing a new tapped horn called
TH-SPUD

I think this is an interesting concept and so I tried to model a diy version.

I'm thinking of using two B&C 8NDL51 drivers. They have a 7 mm xmax which I think should be enough for my small living room.

Planned layout +/- 120 x120 x 25cm:

Click the image to open in full size.

Respons graph in Akabak with quarter wave resonating tube at 65Hz and 60Hz low pass:

Click the image to open in full size.

Hornresponse input:

Click the image to open in full size.

So what do you think? Will it work? Any design faults?
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Old 5th December 2008, 11:19 PM   #2
MaVo is offline MaVo  Germany
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I didnt sim it, but 7mm xmax sounds really low for this low tuning. Check at what input power it runs out of excursion.
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Old 6th December 2008, 07:32 AM   #3
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Yes the power handling of this is not so high.
It runs out of xmax at only 12V rms

Click the image to open in full size.

This should give around 118dB max with corner placement.
Would this be enough or should I better be looking for a more high excursion car audio driver? How would these car drivers compare on a distortion level against the PA driver I'm using now?
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Old 10th December 2008, 12:42 PM   #4
hm is offline hm  Europe
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Hello,

better try two enclosures,
different tuning,
3,7 and 2.5 m long,
you get a better IMP and lower movement,
look my double horns,
a double TH for 5"

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 10th December 2008, 01:50 PM   #5
Eva is offline Eva  Spain
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In a tapped horn the phase varies wildly across the passband and above. Using enclosures with different tuning is strongly not recommended, it results in bad summing or cancellation. Phase matching a mid/bass system and a tapped horn is already difficult enough.
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Old 10th December 2008, 01:56 PM   #6
hm is offline hm  Europe
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Hello,
did you read my double horns? :
SAXOPHON, TROMBONE, POSAUNE,
KORNETT and SUB FANFARE,
special the measurements,

best read "about what" in the middle:
http://www.hm-moreart.de/11.htm
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Old 21st December 2008, 11:54 PM   #7
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G'day geitmans

The Tang Band W8-740 looks great in a box like this. 12mm X-max helps out the power situation quite a bit, too.

Cheers

William Cowan
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Old 22nd December 2008, 01:08 PM   #8
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An interesting driver for a low profile box:

http://www.parts-express.com/pe/psho...38&ctab=2#Tabs

In an 18hz TH a series pair will be 96dB (at 20hz) in 2Pi and take 40V without exceeding x-max. Average about 118dB/40V, ±2dB from 18hz~60hz.

Of course room gain or 1Pi loading would add to this.
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Old 23rd December 2008, 02:22 PM   #9
Clarkcr is offline Clarkcr  United States
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Anyone knwo where I can get that modeling software for my own folded horn project?

THANKS!!!! :-)
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Old 23rd December 2008, 03:11 PM   #10
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AkAbak and Hornresp are what is generally used here.

Hornresp is easier to learn.

Hornresp
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Old 24th December 2008, 06:59 AM   #11
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the W8-740P indeed looks like a good alternative. Its cheaper and has a higher Xmax. I will try to model it.

I tried to model the mechanical behaviour of the cabinet if I would build it with OSB. The first renonance occurs at around 103 Hz. The weakest part is as expected around the mouth of the horn.

Click the image to open in full size.

But 103Hz seems quite low to me. I don't know if anyone has a rule of thumb of how much the first renonance of the cabinet and the maximum operating frequency should be separated?

Maybe it is better to build it using birch plywood. When I find some good mechanical data for plywood I will try to model the effect of it.
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Old 24th December 2008, 02:47 PM   #12
Clarkcr is offline Clarkcr  United States
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I've never seen solid modeling software like that. I don't understand exactly what I'm looking at, but it looks cool!

Also, why are you using OSB? I'm assuming you're actually referring to MDF, which has a much higher density and is preferred over all other types of cabinet material.

Nice work!!

C
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Old 25th December 2008, 09:20 PM   #13
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OSB is about the same strength as MDF, weighs less, and glues up better. If anything it is slightly better than mdf as far as strength goes. BB Plywood is the best though.
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Old 25th December 2008, 11:39 PM   #14
bjorno is offline bjorno  Sweden
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Quote:
Any design faults?
IMO, I fully agree with Eva:

Quote:
‘In a tapped horn the phase varies wildly across the passband and above.’
See the bad phase response in picture: 2(7)

Quote:
It runs out of xmax at only 12 V rms
No, earlier and even if you intend to use this design with most ordinary commercial bass-amps that often uses a 12 dB HP filters at 20 Hz for subsonic frequency protection. See picture 1(7)

Quote:
This should give around 118 dB max with corner placement.
Yes, but only if you count the SPL above 60-70 Hz Hz. See picture 3(7)

IMO a better use of the 8NDL51 drivers for Tapped Horns: See the pictures 4(7) – 5(7) and if SQ is the most important goal: See the smaller BP-TQWT in pictures 6(7)-7(7).

b

1(7)
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File Type: gif 1-x-max-hp-12db_bad.gif (64.3 KB, 3922 views)
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Old 25th December 2008, 11:41 PM   #15
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2(7)
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File Type: gif 2-2 x 8ndl51_th_bad.gif (75.4 KB, 3882 views)
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Old 25th December 2008, 11:42 PM   #16
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3(7)
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File Type: gif 3-spl-0.5xpi_2 x 8ndl51_th_bad.gif (60.7 KB, 3742 views)
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Old 25th December 2008, 11:43 PM   #17
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4(7)
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File Type: gif 4-spl_2 x 8ndl51_bp-th-opt.gif (72.3 KB, 3733 views)
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Old 25th December 2008, 11:45 PM   #18
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5(7)
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File Type: gif 5-spl-0.5xpi_2 x 8ndl51_th-opt.gif (62.3 KB, 2129 views)
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Old 25th December 2008, 11:46 PM   #19
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6(7): BP-TQWT
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File Type: gif 6-spl_2 x 8ndl51_bp-tqwt.gif (73.7 KB, 2166 views)
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Old 25th December 2008, 11:48 PM   #20
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7(7): BP-TQWT
Attached Images
File Type: gif 7-spl-0.5xpi_2 x 8ndl51_bp-tqwt.gif (69.5 KB, 2176 views)
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Old 26th December 2008, 02:11 AM   #21
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Hi Eva, bjorno, all

A couple thoughts;
Eva said “In a tapped horn the phase varies wildly across the passband” and “Phase matching a mid/bass system and a tapped horn is already difficult enough.”

Perhaps in what you’re looking at but normally a measurement trumps a computer model. Simply, some features that are predicted in Akabak don’t exist in the physical item.
If your going to have faith in a prediction it has to be founded on some track record comparing with measured results. I can tell you Akabak which I use has some issues, it would be no fun at all to tell you what to do anymore than pointing out a trail.

If your first statement were true, where exactly do you see this in the measured response of say a th-215? Keep in mind, in the Tapped horns that aren’t as flat with just one unit, if you choose to eq them flat, you generally correct the phase response.
Also some Tapped horns have as little as approaching half the measured GD associated with it’s low corner compared to a vented box with the same corner F (due to it being a quarter wave 90 degree resonator and not an 180 degree inverter). This much of a difference might be audible and why they sound different.

http://www.danleysoundlabs.com/pdf/T...ec%20Sheet.PDF

The spud is a new product, we have not done the normal formal outdoor half space measurements yet pending time and weather.

So far as using them in a full range system, a Tapped horn is part of at least five of our full range products including the SH-50.
Keep in mind, our stand alone subwoofer products are normally used below 70-80Hz as the spud is for home theater use.
Merry Christmas, Happy Holidays and good sound to all!
Tom Danley
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Old 28th December 2008, 07:01 PM   #22
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The problem with tapped horns are the two propagation paths from the speaker to the mouth having very different lengths. This causes several jumps in group delay. Hornresp does *not* model this in any way. Horn phase plots produced by Hornresp are completely useless.

My experience is based in real double 15" super-scooper type cabinets. These are much better behaved than tapped horns in the midbass region, yet they are quite difficult to integrate with other midrange and subwoofer systems due to the phase jumps, requiring extensive phase shifting and EQ for proper on-axis summing.
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Old 28th December 2008, 07:39 PM   #23
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I am wondering how long is a *good* long and how long is *too long*?

If I'm building a sub that I want reasonably flat down to 20Hz, with the Dayton Titan MkIII 15" driver:

Frequency range: 19-500 Hz * Magnet weight: 136 oz. * Fs: 24 Hz * SPL: 91.7 dB 2.83V/1m, 88.7 dB 1W/1m * Vas: 5.46 cu. ft. * Qms: 6.75 * Qes: .52 * Qts: .49 * Xmax: 20.5mm

,,,,,then how long is too long and how short is too short? In my current drawing, I'm looking at a distance of 9 feet on each side of the driver that twists and turns through a cabinet.

If both passages are of the same length, then wouldn't this balance out the equilibrium problem?
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Old 29th December 2008, 06:13 AM   #24
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Hello,
look what happens by using two different horns,
you get more bass and a partiell delete over 100 Hz,
where normally such horns rise the SPL ~10 dB,
so it is useful up to 200 Hz, BUT driver position in the horn mouth
is for HiFi only useful up to 100 Hz.

I made two alternative studies for 16 cm driver
http://www.hm-moreart.de/108.htm
scoll down

here the imp of the SUBfanfare:
both
single a
single b
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 29th December 2008, 11:22 AM   #25
Clarkcr is offline Clarkcr  United States
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I think I just attempted to highjack this thread. My appologizes!
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