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Old 7th April 2010, 02:18 PM   #1
vadi is offline vadi  Austria
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Default what driver for tapped horn?

Hi,
I have an old driver lying around and I wanted to a build tapped horn subwoofer. How can I know if the driver is totally unsuitable according to its TSP?
Thanks!


edit:
Sorry, I didn't look enough, here is what I found at least.
It seems cutoff frequency should be lower than Fs of the driver. A high BL can help move the cutoff higher while preserving flat response. A low Qts means the driver has to be near the end of the horn, mid values are good.

Last edited by vadi; 7th April 2010 at 02:32 PM.
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Old 7th April 2010, 03:26 PM   #2
MaVo is offline MaVo  Germany
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nearly all pro audio woofers can be used in tapped horns, so you can check if the parameters are similar to those. fs 30-50, strong motor, heavy membrane are good indicators. after all, just dl hornresp and check it out, as the box shape can be changed to fit alot of different parameters.
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Old 7th April 2010, 05:30 PM   #3
vadi is offline vadi  Austria
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Allright, thank you. I already looked into Hornresp but I think I have tomeasure the all the TSP first.
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Old 7th April 2010, 07:38 PM   #4
FlipC is offline FlipC  United States
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What is the driver in question?

And i do not agree with "all pro audio woofers can be used in tapped horns"
TH's are very specific. less you want crazy peaks and valleys or an output sub par with compared to a reflex cab.
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Old 7th April 2010, 08:10 PM   #5
vadi is offline vadi  Austria
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It's a Mac Audio Absolute 250 with an aluminium "cone". It has a small sticker with some TSP on it and I found it on the web too: link. I hope I can run this to about 28Hz, that would be very nice. Currently it's running in a vented enclosure I designed with WinISD Pro.

Last edited by vadi; 7th April 2010 at 08:13 PM.
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Old 8th April 2010, 12:54 AM   #6
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by vadi View Post
It's a Mac Audio Absolute 250 with an aluminium "cone". It has a small sticker with some TSP on it and I found it on the web too: link. I hope I can run this to about 28Hz, that would be very nice. Currently it's running in a vented enclosure I designed with WinISD Pro.
Hi vadi,

28 Hz is no problem to reach with a smooth BW to over 80 hz if you can consider a T-TQWT.

b
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Old 8th April 2010, 11:18 AM   #7
vadi is offline vadi  Austria
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Thank you very much for the help Bjorn! The response should be ideal - I will combine this with my open baffle speaker. (Roughly following the design of Linkwitz's Orion but with lower SPL).
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Old 8th April 2010, 08:14 PM   #8
vadi is offline vadi  Austria
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Sorry for the doublepost but I played around with the size of the speaker.
I found an alternative which should play equally loud since the bigger one has a SPL dip at 32Hz. I hope I can build it like that:

- it is 19,4 litres instead of 53,4l
- after I apply a highpass at about 38Hz - which should about flatten the response - it lowers peak excursion and power limit becomes about as important as displacement limit
- the first peaks in SPL and group delay are further away also; I cut the sub at about 60Hz
Attached Images
File Type: gif Untitled.gif (77.9 KB, 226 views)
File Type: gif Untitled1.gif (14.8 KB, 220 views)
Attached Files
File Type: txt macaudio.txt (442 Bytes, 5 views)

Last edited by vadi; 8th April 2010 at 08:30 PM.
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Old 9th April 2010, 08:48 PM   #9
vadi is offline vadi  Austria
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Can't edit my post but I realized the above horn is too extreme. However I'll try a smaller 35l sub which shifts displacement requirements away from 28Hz. Its group delay is a bit worse but I think this should be okay, I want it as small as possible. It increases max SPL too.

Thank you very much bjorno!
Attached Images
File Type: gif ttqwt.gif (87.9 KB, 202 views)
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File Type: txt maca.txt (373 Bytes, 3 views)
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Old 10th April 2010, 05:49 PM   #10
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by vadi View Post
..I realized the above horn is too extreme..
Hi vadi,

Agree.

First, I like to comment the’ visual looks’ of your Impulse response plot here above as it IMO gives a false ‘picture’ view of what can be heard and which design is the best, thus it doesn’t represent a T-TQWT or a TH heard impulse response when not filtered as for a normal sub bas use.

One way to resemble a ‘heard’ situation better visualized is to add an inductance to Le in HR until X (Le)= Re, i.e. adding a 6 dB/ octave pole at the XO point = 80 Hz. (See picture #1)

This is not as steep as you would choose a filter slope in the reality (A 12dB or a sharper LP filter is normally chosen for sub use.) but it’s much better than using no filtering at all, as only the time before about 10mS will hint you if localization cue or image shift will be present and longer pulse time have to be transformed into FR domain before judgeing any timbral effects.

You really want 250 Hz be at minimum 20 dB down before looking at the sub Impulse response. A fake 250 Hz /20 dB down is achieved by placing a 6 dB/octave filter= 20 dB/decade at 25 Hz using a suitable X (Le)= Re at the HR main screen. See the result in picture # 2.

Picture# 3 shows your new design (much more sane than the first you simulated, hint try to keep the compression ratio down, 4:1 at maximum for a aluminum coned driver) but IMO not as good as my suggestions in picture #4. If in the ‘OD’ mode = the driver access lid is completely removed, the T-TQWT is turned into a good Offset Driver TL system too.

b
Attached Images
File Type: gif 1-McAudio-imulseresp.GIF (94.9 KB, 190 views)
File Type: gif 2-25Hz-25mH-impulseresp.GIF (94.1 KB, 33 views)
File Type: jpg 3-vadi_T-TQWT_OD.JPG (546.7 KB, 34 views)
File Type: jpg 4-vadi_T-TQWT_OD-rek.JPG (557.0 KB, 27 views)
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