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Old 17th February 2012, 07:22 AM   #1
Zubs is offline Zubs  South Africa
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Default First Tapped Horn

Hi all

I found out about tapped horns a few months ago, and straight away I thought I had to try one.I set about learning Hornsrep, with the help of related posts on this and other forums, put together what I think is correct.

Im at the point now where I need to ask the "old hands" for some guidance.As you can see from the pic below the response looks like the top of a castle wall, and nothing I seem to do will flatten it out. I have come to the conclusion the Sub is just rubbish (kenwood KFC-W2512 ) I know its a car sub, but as this is just a learning experience I thought why not.

Click the image to open in full size.

So the specs of the sub are as follows for anyone who is willing to take the time to lend a hand.

fs = 44Hz ( I see its listed as 48 Hz on other documentation , Sigh . )
sd = 350
Qms = 14.047
Qes = 1.821
Qts = 1.612
Xmax = 13 mm
BL = 7.5
Le = 1.15mH
Re = 3.5
Z = 4
Vas = 19.7 L

I'm not even sure if my Hornsrep data is correct, so go easy on me

Last edited by Zubs; 18th February 2012 at 09:17 AM.
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Old 17th February 2012, 04:25 PM   #2
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Hi, like you I'm on the learning curve. I just put your sub into a T-TQWT that another member designed for me and got a similar bump in the 40-60Hz region too, so tried it in a tapped horn design too-also looks like a snowboarders wet dream.

Please double check your values-when I entered in the values and asked HR to calculate others I ended up with different MMD...
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Old 17th February 2012, 05:06 PM   #3
GM is offline GM  United States
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Yeah, the specs calculate a usable max flat BW of ~43.7-52.7 Hz, so a 'one note' wonder. It has enough Xmax to mass load it to a lower Fs/higher Qts that would at least allow a lower 'one note' .

GM

edit: That said, try a basic TL tuned to ~Fs/Qts = 29.78 Hz in ~2.5 ft^3 net. Once stuffed it should be much flatter/extended. If it looks OK to you, then try adjusting it for tapped variants [TTL, TTQWT].
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Last edited by GM; 17th February 2012 at 05:19 PM.
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Old 17th February 2012, 05:41 PM   #4
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Quote:
Originally Posted by Zubs View Post
.
As you can see from the pic below the response looks like the top of a castle wall, and nothing I seem to do will flatten it out. I have come to the conclusion the Sub is just rubbish .
A response curve falling within +/- 3 dB is considered good.
HornResp tends to exaggerate dips and peaks.
Your response chart is within +/- 2.5 dB in the pass band, hardly "rubbish".

If the design as built conforms to the chart, it won't sound bad, and a little EQ could smooth out the "castle" which is far less a problem than room modes (often +/- 6 dB or more) will be.
I just built a sub that has a -6 dB hole that would be the reciprocal of a room peak...

Art
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Old 17th February 2012, 06:33 PM   #5
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Ya that graph looks alright, 2 full octaves, unless you chop off above 80. Still 35-80 is decent. Perhaps you could post the spl response? Lots of xmax to play with.

I must say that qts spec is insane, never seen over 1 qts!

maybe wack the box out with a single fold and play with it.

also the woofer tester from parts express, when its in stock, should help you out now your across the event horizon of the black hole known as diy subwoofer design and building.
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Old 18th February 2012, 08:40 AM   #6
Zubs is offline Zubs  South Africa
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Quote:
Originally Posted by TheBaronGroog View Post

Please double check your values-when I entered in the values and asked HR to calculate others I ended up with different MMD...
Mmm, Just did check the numbers, you were right, Since the MMD was given I put that in and looked at the figures that were calculated, this put everything out,but not by much.This means that something on the listed figures is not 100% correct.

Most errors were at the first and second decimal, it also dropped the fs by 1.4 Hz, I don't think the discrepancies will be to detrimental, as this is my first build ? will they ?
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Old 18th February 2012, 08:51 AM   #7
Zubs is offline Zubs  South Africa
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Quote:
Originally Posted by Etocynned View Post
. Perhaps you could post the spl response?



also the woofer tester from parts express, when its in stock, should help you out now your across the event horizon of the black hole known as diy subwoofer design and building.
Is the graph above not the SPL Response ? ( sorry I'm learning)

The tester would be nice, shipping to South Africa is rather pricey, but on the cards for the future
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Old 18th February 2012, 08:55 AM   #8
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1.4Hz shouldn't make that huge a difference-though I'll conceed otherwise if someone with more experience in this type of enclosure design steps up!
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Old 18th February 2012, 08:57 AM   #9
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Quote:
Originally Posted by Zubs View Post
Is the graph above not the SPL Response ? ( sorry I'm learning)

The tester would be nice, shipping to South Africa is rather pricey, but on the cards for the future
Yup, it is.

I had one shipped to the UK, ended up about the same price in as the unit was in $-I did wait until the Thanksgiving sale so was $89.99 IIRC
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Old 18th February 2012, 09:11 AM   #10
Zubs is offline Zubs  South Africa
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Join Date: Dec 2011
Location: Durban
Quote:
Originally Posted by GM View Post
Yeah, the specs calculate a usable max flat BW of ~43.7-52.7 Hz, so a 'one note' wonder. It has enough Xmax to mass load it to a lower Fs/higher Qts that would at least allow a lower 'one note' .

GM

edit: That said, try a basic TL tuned to ~Fs/Qts = 29.78 Hz in ~2.5 ft^3 net. Once stuffed it should be much flatter/extended. If it looks OK to you, then try adjusting it for tapped variants [TTL, TTQWT].
Right, So I did a few of calculations based on these figures, 29.78 Hz equates to a line length of roughly 285 cm, based on the net volume of 71 Liters (2.5 Cubic feet) I came up with the following, which simulated similarly as a "horn", and " Vented " enclosures ( seeing if I could replicate the result via a different means, Isn't learning fun)

Click the image to open in full size.

Schematic is as follows ( Please someone point out if I'm doing something wrong , or stupid.)

Click the image to open in full size.

Judging by the results here I would guess this TL is not really an option. ( time for some more playing).
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