Impedance curve......

rabbitz · 30th August 2003, 01:01 PM

The is the impedance curve I got in LSPCad for 2 Vifa TC11s in parallel - see any problems?

My amp should should be able to handle it as it is:
115W 8 ohm
160w 4 ohm
175w 2 ohm

mikee12345 · 1st September 2003, 01:56 AM

ur amp is 2ohm capable?

nice!

kelticwizard · 1st September 2003, 05:05 AM

High impedance is no problem for an amp. If it is an amp designed to give out 8 ohms, an impedance peak well over 8 ohms will give it no problems at all.

Low impedance is the problem.

I see that your lowest impedance is about 2.8 ohms. An amp rated for 2 ohms will handle it with ease. It is low impedance that causes the problems. High impedance is a piece of cake.

rabbitz · 1st September 2003, 04:19 PM

I think the graph is a bit misleading as I believe the impedance would start to rise from 400Hz on based on the Vifa's graph. I can't measure this. Seems similar to the impedance for the LR speaker in chapter 12 in the Loudspeaker Design Cookbook - bottoms at 3 Ohms. Probably classed as a 4 Ohm speaker.

The amp manual is interesting as it states "if you use one centre speaker, the impedance of the speaker must be 4 ohm or higher, if you use 2 centre speakers, the impedance of each speaker must be 2 ohm or higher". I thought that with 2 speakers you would need 8 ohms or higher.

Nappylady · 1st September 2003, 05:59 PM

They're probably assuming that you'll wire them in series.

ucla88 · 4th September 2003, 01:39 PM

I think you will be fine. The impedance will be a bit low, but not much power will be going into these TC11's-they can't handle that much. Really, only a couple of watts at the low end before they start to distort. See my impedance curve and comments. I suspect your impedance will be around 2.5 ohms.

Link to Vifa TC11 project

rabbitz · 4th September 2003, 02:52 PM

Thanks Mark.

These will not see much bass below 80Hz as they are setup for rear speaker duties with the speakers set to small. Since the 2 drivers are in parallel, this will halve the cone excursion. The box is tuned to 66Hz which helps some more.

1st September 2003, 05:05 AM	#3
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	High impedance is no problem for an amp. If it is an amp designed to give out 8 ohms, an impedance peak well over 8 ohms will give it no problems at all. Low impedance is the problem. I see that your lowest impedance is about 2.8 ohms. An amp rated for 2 ohms will handle it with ease. It is low impedance that causes the problems. High impedance is a piece of cake. __________________ "A friend will help you move. A really good friend will help you move a body." -Anonymous

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1st September 2003, 01:56 AM	#2
mikee12345 diyAudio Member Join Date: Nov 2002 Location: NZ	ur amp is 2ohm capable? nice!

1st September 2003, 04:19 PM	#4
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	I think the graph is a bit misleading as I believe the impedance would start to rise from 400Hz on based on the Vifa's graph. I can't measure this. Seems similar to the impedance for the LR speaker in chapter 12 in the Loudspeaker Design Cookbook - bottoms at 3 Ohms. Probably classed as a 4 Ohm speaker. The amp manual is interesting as it states "if you use one centre speaker, the impedance of the speaker must be 4 ohm or higher, if you use 2 centre speakers, the impedance of each speaker must be 2 ohm or higher". I thought that with 2 speakers you would need 8 ohms or higher.

1st September 2003, 05:59 PM	#5
Nappylady diyAudio Member Join Date: Feb 2003 Location: Salt Lake City	They're probably assuming that you'll wire them in series.

4th September 2003, 01:39 PM	#6
ucla88 diyAudio Member Join Date: Dec 2001 Location: rocklin, CA	I think you will be fine. The impedance will be a bit low, but not much power will be going into these TC11's-they can't handle that much. Really, only a couple of watts at the low end before they start to distort. See my impedance curve and comments. I suspect your impedance will be around 2.5 ohms. Link to Vifa TC11 project

4th September 2003, 02:52 PM	#7
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Thanks Mark. These will not see much bass below 80Hz as they are setup for rear speaker duties with the speakers set to small. Since the 2 drivers are in parallel, this will halve the cone excursion. The box is tuned to 66Hz which helps some more.