Tapped Horns - Simulation VS Reality - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th November 2009, 10:45 AM   #11
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Hi,

FYI:More CSI observations It looks like the designer of this TH by a mistake? used a 2P = 2 drivers in parallel simulation seen at the TH input screen here above, but the finished TH-box has only one driver? See picture 1(3) where the suggested 2P driver TH is compared to using only one driver.

The termination (load) from the pipe looks ending too early and not fully(acoustically) enclosing the driver. Actually the implemented speaker looks like a slightly positive taper OD(offset driver) TL terminated at a driver diameter less than the total internal length = 259 cm and thus tuned above fs. This is IMO not a TH.

As can be seen at the excursion plot from about 50-60 Hz: only a very steep(> 24 db/octave) HP filter would protect the 2P drivers from over excursion: See picture 2(3) where also plots of more realistic max SPL is shown for the 2P driver TH and the one driver closed box at the left side of the picture.

The driver in use is IMO almost a text box example of a driver primarily well suited for a small closed box . As Qts is about 0.42 a box volume should stay within 2xVas at max.


Picture 3(3) shows a 2P (two drivers in parallel)T-QWP (tapped quarter wave pipe) compared to the proposed 2P driver TH. Note: the pipe diameter must then be less than 2xSd for both sides of the drivers in order to minimize pass band ripple when tuned at fs.

b
Attached Images
File Type: gif 1-Ultra-LV-10_TH.GIF (168.6 KB, 461 views)
File Type: gif 2-Ultra-LV-10_TH_maxSPL.GIF (138.5 KB, 433 views)
File Type: gif 3-Ultra-LV-10_T-QWP-comp-TH.GIF (163.6 KB, 418 views)
  Reply With Quote
Old 28th November 2009, 01:22 PM   #12
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by bjorno View Post
Hi,

FYI:More CSI observations It looks like the designer of this TH by a mistake? used a 2P = 2 drivers in parallel simulation seen at the TH input screen here above, but the finished TH-box has only one driver? See picture 1(3) where the suggested 2P driver TH is compared to using only one driver.
Good catch. There actually is only one driver in the box.


Quote:
Originally Posted by bjorno View Post
The termination (load) from the pipe looks ending too early and not fully(acoustically) enclosing the driver. Actually the implemented speaker looks like a slightly positive taper OD(offset driver) TL terminated at a driver diameter less than the total internal length = 259 cm and thus tuned above fs. This is IMO not a TH.
Furthermore, the rear of the driver is actually loaded by a chamber. See diagram below:

Click the image to open in full size.

How would you model this in HornResp?
  Reply With Quote
Old 28th November 2009, 01:58 PM   #13
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Did the spider to former glue joint fail?

With no deformation of the back end of the former, why did the coil come apart?

I see a hard rub, and a coil delamination from improper adhesive and/or cure.

Every system should have a cut-off filter below the tuning frequency.

Amplifiers need clipping eliminators, or soft clipping on their inputs (to prevent amplifier clipping from producing loudspeaker dynamic off-set).

I'm not sure about the 'tapped horn' being the blame here.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 28th November 2009, 11:14 PM   #14
diyAudio Member
 
davygrvy's Avatar
 
Join Date: Mar 2007
Location: Oakland, CA
Blog Entries: 1
David, How does HR calculate max SPL? It doesn't happen to do sqrt(P*Z) where Z is a calc'd impedance does it? If so, that's a bit odd as power amps are constant voltage systems, not constant power. What I mean is, if at 110Hz Z is 9 Ohms @ -42 degrees, but rated impedance is 4 Ohms and is being driven by 500W amp, that's still 45V max output. To get 500W across 9 Ohms is 67V. The amp is already clipped, you aren't going to get there. There really would be a voltage ceiling as well to maxSPL.
__________________
Think out of the box
  Reply With Quote
Old 29th November 2009, 04:34 AM   #15
diyAudio Member
 
Join Date: Nov 2009
Quote:
Originally Posted by djk View Post
Did the spider to former glue joint fail?

With no deformation of the back end of the former, why did the coil come apart?

I see a hard rub, and a coil delamination from improper adhesive and/or cure.

Every system should have a cut-off filter below the tuning frequency.

Amplifiers need clipping eliminators, or soft clipping on their inputs (to prevent amplifier clipping from producing loudspeaker dynamic off-set).

I'm not sure about the 'tapped horn' being the blame here.
No the Glue did not fail / looks as if the coil started to unravell from the bottom hitting something in the gap...
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
__________________
Doe's the Noise inside my head bother you ???
  Reply With Quote
Old 29th November 2009, 07:40 AM   #16
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by davygrvy View Post
How does HR calculate max SPL?
Hi davygrvy,

Hornresp calculates normal SPL response using a constant input voltage Eg. Maximum SPL response is calculated using a constant input power Pmax (except when the Xmax limit is reached at any frequency).

The attached screenprint of the sealed box example discussed earlier, illustrates the difference.

The gray trace shows the SPL for a constant input power of 500 watts. (Xmax set to 99.9 mm to ensure that the response is not displacement limited at any point). The black trace shows the SPL for a constant input voltage of 40 volts.

Note that the diaphragm displacement at 40 hertz for an input voltage of 40 volts is 13.4 mm, whereas the diaphragm displacement at 40 hertz for an input power of 500 watts is 29.0 mm.

As I said in my previous message, it is important to understand the difference between input power and input voltage :-).

Kind regards,

David
Attached Images
File Type: jpg Compare.jpg (43.7 KB, 55 views)
__________________
www.hornresp.net
  Reply With Quote
Old 29th November 2009, 09:01 AM   #17
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Thanks for the close up of the coil damage.

I agree, it looks like it bottomed out on the backplate.

Dynamic off-set can destroy woofers in the blink of an eye. It is very important to hard limit (or clip) the input signal to the amplifier so the amplifier feedback loop never clips.

I used a 1KW amplifier on a sub tuned to 23hz with about 6dB of boost. It would bottom out the instant the amplifier clipped. The same sub could be bottomed out by a 100W amplifier driven into clipping. You could see the cone jerking back-and-forth in an irregular maner (it lookeed like it was between 2hz~8hz), even though there was a filter at 23hz (part of the EQ for the sub).
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 29th November 2009, 04:01 PM   #18
diyAudio Member
 
Join Date: Nov 2009
I have the signal set with an O-Scope / NO SQUAREWAVES
using an Alpine 9887 ( Imprint ) & Kove Audio Aphex Ax1 Signal Processor, have a CLEAL 6v through the Rca's / Clean Signal on the Oscope...
Gain on the amps is set on the floor maybe 1 notch up from Zero (0) / no bass boost

please keep in mind that i am only a Weekend SPL Warrior / during the week i have an SQL Enclosure loaded
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
__________________
Doe's the Noise inside my head bother you ???
  Reply With Quote
Old 29th November 2009, 07:45 PM   #19
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by Brian Steele View Post
How would you model this in HornResp?
Hi,
I would model this outlay almost like a straight pipe where S1 and S2 have constant equal CSA, L12+L23 set to the first chamber length using the TH Wizard.

As the termination opening is IMO too large for a 'tapped purpose',I would end the length calculations as for an 'OD' system model ( See the picture) that is invoked at the main input screen.

A length reduction, about 9" i.e. Total L = L12+L23+L34+L45 -9" is then necessary as seen in the picture.

After returning from the TH Wizard screen to the main input screen in order to
calculate an 'OD' speaker the red colored label 'TH' must be changed to a red 'OD'.

Then if the calculation button is pressed, the driver to 'terminus' distance must be inserted pressing 'Tools' and from the drop down list select the 'Combined
Response...' and enter for this case a distance of about 4.25" or about 11 cm.

b
Attached Images
File Type: png LBs10inch.PNG (73.4 KB, 144 views)
  Reply With Quote
Old 29th November 2009, 08:20 PM   #20
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by bjorno View Post
Hi,
I would model this outlay almost like a straight pipe where S1 and S2 have constant equal CSA, L12+L23 set to the first chamber length using the TH Wizard.

As the termination opening is IMO too large for a 'tapped purpose',I would end the length calculations as for an 'OD' system model ( See the picture) that is invoked at the main input screen.

A length reduction, about 9" i.e. Total L = L12+L23+L34+L45 -9" is then necessary as seen in the picture.

After returning from the TH Wizard screen to the main input screen in order to
calculate an 'OD' speaker the red colored label 'TH' must be changed to a red 'OD'.

Then if the calculation button is pressed, the driver to 'terminus' distance must be inserted pressing 'Tools' and from the drop down list select the 'Combined
Response...' and enter for this case a distance of about 4.25" or about 11 cm.

b
Hmm... will try that when I have a few minutes to spare...

I forgot to include that the internal height of the box (not given in the picture) is 11".
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
jbell's set of four tapped horns davygrvy Subwoofers 480 19th March 2014 01:27 PM
Dampening in Tapped Horns?? atilsley Subwoofers 25 20th June 2009 08:24 AM
how to model tapped horns? weikertball Subwoofers 2 11th January 2009 09:43 PM
Your thoughts on simulation compared to reality Mr Evil Everything Else 12 1st March 2005 03:45 AM


New To Site? Need Help?

All times are GMT. The time now is 02:51 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2