How do impedance switches work? [message #28130] |
Mon, 07 November 2005 17:06 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
raintalk
Messages: 3 Registered: May 2009
|
Esquire |
|
|
http://www.kustom.com/products/pa/s...e_impedance.asp http://news.harmony-central.com/New...AccuSwitch.htmlI could see how a 4 or 16 ohm or 8 or 32 ohm switch could work, but how do switches that just double or half the impedance work?
|
|
|
|
Re: How do impedance switches work? [message #28132 is a reply to message #28130] |
Tue, 08 November 2005 11:27 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
raintalk
Messages: 3 Registered: May 2009
|
Esquire |
|
|
Sorry - I don't know how to make links work here. ![](http://www.audioroundtable.com/emoticons/frownie.gif) One is the Kustom MLI monitor speaker. It has an impedance switch to select 8 or 16 ohms. http://www.kustom.com/products/pa/switchable_impedance.asp
The other is the Accugroove bass cabinet - it has a switch to select either 4 or 8 ohms. (But I found a thread on talkbass and apparently the switch doesn't measure up to its claims.) My confusion is how a switch could select just double the impedance. For example: 4-or-8ohms, or 8-or-16 ohms. I can't see how you can series/parallel to get such combinations. It'd sure be handy if such a switch were possible.
|
|
|
Re: How do impedance switches work? [message #28133 is a reply to message #28132] |
Tue, 08 November 2005 13:28 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
![](http://audioroundtable.com/forum/images/custom_avatars/5.gif) |
Wayne Parham
Messages: 18757 Registered: January 2001
|
Illuminati (33rd Degree) |
|
|
The URL you provided shows an attenuator, with what is probably an additional fixed resistance to set the load. To create a higher impedance load, one can simply add series resistance to the speaker circuit, perhaps with some amount of damping resistance or conjugate across the driver to help prevent resonant peaking. But really, I think the impedance switch is a bad idea brought forth by a marketing department, so they may not have cared to use any sort of damper to reduce response anomalies. I think what they're basically doing is using speakers with 8 ohm voice coils, and optionally switching in 8 ohms series resistance to make a 16 ohm circuit.The attenuator is an L-Pad, which has series and parallel resistance elements. The switch probably sets a fixed resistor, which is used as part of a voltage divider. The other part of the divider is a variable resistor. Since speakers are a reactive load, resistance does more than just attenuate, it also acts something as a tone control. But I think that's all way beyond the scope of this discussion. The bottom line is that the switch is just selecting the amount of resistance used in the circuit.
|
|
|
Re: How do impedance switches work? [message #28135 is a reply to message #28133] |
Tue, 08 November 2005 15:11 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
raintalk
Messages: 3 Registered: May 2009
|
Esquire |
|
|
OK thanks. So nothing fancy with a dual VC. Adding a resistance would sure effect overall SPL with but for stage monitors this might be acceptable if one was trying to control volume on one part of a stage. Here's the link to the other switch. http://news.harmony-central.com/News/2003/AccuSwitch.html You have to go to the accugroove site to find out more about it. But as I mentioned - folks who actually measured it say it does't work.
|
|
|
|
|
|