TL Tapering - quick question

bigwill · 22nd April 2005, 08:05 PM

Why are transmission lines usually tapered? Are there any sonic benefits of this over just having a line that's the same area all the way through?

MJK · 23rd April 2005, 12:46 AM

For a given length, a tapered TL will have a lower tuning frequency then a straight TL. So if you want to tune your TL to say 30 Hz, a tapered TL will be shorter.

As a second benefit, the tapered TL's next harmonic will be higher in frequency so there will be a bigger frequency span between the fundamental (1/4 wavelength standing wave) and the next resonance (3/4 wavelength standing wave). Since the 3/4 wavelength resonance occurs at a higher frequency, the fiber stuffing is more effective at attenuating the resonance and reducing the ripple.

You can see some of these trade-offs in my TL alignment tables for classic TL designs.

jackinnj · 23rd April 2005, 03:36 AM

isn't it just as effective to offset the placement of the driver by 1/3 to 1/4 of the TL length?

Tweeker · 23rd April 2005, 05:26 AM

Offseting the driver doesnt change the frequency at which the 3/4 pipe wavelength resonance occurs, though it does mitigate its effects.

bigwill · 23rd April 2005, 11:56 AM

One more thing... the line length of my current design is about 31Hz WITHOUT stuffing. The Fs of my driver is 26Hz. Is the line too long? I don't want to to be tuned below Fs when I've stuffed it

Edit: The line is tapered, so it's probably LOWER than 31Hz

MJK · 23rd April 2005, 02:27 PM

Quote:

The line is tapered, so it's probably LOWER than 31Hz

The first thing you need to do is determine the resonant frequency of your TL geometry. From the statement above it would appear that you don't really know. If you go to my alignmnet tables, you should be able to detemine this frequency.

Quote:

the line length of my current design is about 31Hz WITHOUT stuffing. The Fs of my driver is 26Hz. Is the line too long? I don't want to to be tuned below Fs when I've stuffed it

Stuffing is not going to lower the line's tuning frequency significantly. Stuffing will have less than a 1% impact on the frequency. Stuffing will attenuate the resonance and smooth the SPL response.

bigwill · 23rd April 2005, 02:46 PM

I'm sorry to say I don't understand these tables

Another problem is that I don't have a full set of TS parameters for my drivers. What would happen if I just experimented?

MJK · 23rd April 2005, 03:13 PM

Sounds like you are just going to have to try and make some good choices. It might work out OK or you might learn something that you could apply to the next attempt.

bigwill · 23rd April 2005, 03:15 PM

What a carefully worded version of 'There's no helping you now!'

MJK · 23rd April 2005, 03:22 PM

Unfortunately, that is just about right. In my opinion, if you really want to do your own designs you need to perform lots of measurments, a fair number of simulations, and really engineer the enclosure. I don't know of any other way. A few people can do it by intuitive feel from trial and error building of a few prototypes and get great results, they are much smarter then I am.

22nd April 2005, 08:05 PM	#1
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	TL Tapering - quick question Why are transmission lines usually tapered? Are there any sonic benefits of this over just having a line that's the same area all the way through?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Tapering TL-speaker, why?	MJ Dijkstra	Multi-Way	0	25th February 2007 06:40 PM
Quick quick question !	guitvinny	Pass Labs	6	7th February 2007 05:20 PM
Bessel Or power tapering?	24kilo	Multi-Way	13	2nd October 2005 05:57 PM
Is my power tapering wired correctly?	GuyPanico	Multi-Way	8	6th June 2005 02:25 AM
Help with Line Array wiring_Power tapering	sqlkev	Multi-Way	20	24th July 2004 08:32 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

23rd April 2005, 12:46 AM	#2
MJK Account disabled at member's request Join Date: Feb 2002 Location: Clifton Park, NY	For a given length, a tapered TL will have a lower tuning frequency then a straight TL. So if you want to tune your TL to say 30 Hz, a tapered TL will be shorter. As a second benefit, the tapered TL's next harmonic will be higher in frequency so there will be a bigger frequency span between the fundamental (1/4 wavelength standing wave) and the next resonance (3/4 wavelength standing wave). Since the 3/4 wavelength resonance occurs at a higher frequency, the fiber stuffing is more effective at attenuating the resonance and reducing the ripple. You can see some of these trade-offs in my TL alignment tables for classic TL designs.

23rd April 2005, 03:36 AM	#3
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	isn't it just as effective to offset the placement of the driver by 1/3 to 1/4 of the TL length?

23rd April 2005, 05:26 AM	#4
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Offseting the driver doesnt change the frequency at which the 3/4 pipe wavelength resonance occurs, though it does mitigate its effects.

23rd April 2005, 11:56 AM	#5
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	One more thing... the line length of my current design is about 31Hz WITHOUT stuffing. The Fs of my driver is 26Hz. Is the line too long? I don't want to to be tuned below Fs when I've stuffed it Edit: The line is tapered, so it's probably LOWER than 31Hz

23rd April 2005, 02:46 PM	#7
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	I'm sorry to say I don't understand these tables Another problem is that I don't have a full set of TS parameters for my drivers. What would happen if I just experimented?

23rd April 2005, 03:13 PM	#8
MJK Account disabled at member's request Join Date: Feb 2002 Location: Clifton Park, NY	Sounds like you are just going to have to try and make some good choices. It might work out OK or you might learn something that you could apply to the next attempt.

23rd April 2005, 03:15 PM	#9
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	What a carefully worded version of 'There's no helping you now!'

23rd April 2005, 03:22 PM	#10
MJK Account disabled at member's request Join Date: Feb 2002 Location: Clifton Park, NY	Unfortunately, that is just about right. In my opinion, if you really want to do your own designs you need to perform lots of measurments, a fair number of simulations, and really engineer the enclosure. I don't know of any other way. A few people can do it by intuitive feel from trial and error building of a few prototypes and get great results, they are much smarter then I am.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)