Help with impedance matching volume controls on large system

[tmman]

Hi All,

I need some help understanding what I should be setting the impedance matching on my volume controls at. Here is a Google Drive link to my wiring schematic I put together: https://drive.google.com/file/d/0B4UrCT385LKlczU3V3VHWnF6S0k/edit?usp=sharing

I believe all volume controls are currently set at 2x (or no impedance matching). Where should they be set and why? I have noticed that the amplifier goes into protection mode when the volume knobs are turned down quite a bit, or all the way. Why is this? The amplifier also gets very hot when those knobs are turned down.

Another observation is that when I keep the volume control knobs at about half way and lower the volume via the per channel knobs on the amplifier, protection mode does not go off and the amp runs cooler.

Ultimately, I want to make sure I am running this system in the most efficient and effective manner possible as I am told there are some fairly decent components here. But I have no idea how impedance should be set to work best.

Thanks in advance for any advice/explanation you may be able to provide.

Best,
Travis

 

[TLS Guy]

Hi All,

I need some help understanding what I should be setting the impedance matching on my volume controls at. Here is a Google Drive link to my wiring schematic I put together: https://drive.google.com/file/d/0B4UrCT385LKlczU3V3VHWnF6S0k/edit?usp=sharing

I believe all volume controls are currently set at 2x (or no impedance matching). Where should they be set and why? I have noticed that the amplifier goes into protection mode when the volume knobs are turned down quite a bit, or all the way. Why is this? The amplifier also gets very hot when those knobs are turned down.

Another observation is that when I keep the volume control knobs at about half way and lower the volume via the per channel knobs on the amplifier, protection mode does not go off and the amp runs cooler.

Ultimately, I want to make sure I am running this system in the most efficient and effective manner possible as I am told there are some fairly decent components here. But I have no idea how impedance should be set to work best.

Thanks in advance for any advice/explanation you may be able to provide.

Best,
Travis

That diagram is not help as there is not enough detail.

Obviously what you are doing is wrong and going to blow up your system. I strongly suspect you have your controls wired backwards, so that as you down the volume you are creating a short circuit.

Impedance matching controls are auto transformers.

You need to wire them according to the manufacturers instruction. The controls should have a chart for the correct tap for the number of speakers of a given impedance to be connected to. There are often jumpers between taps that need to be installed or removed in various situations.

If you don't have the instructions that came with the controls, then go to the manufacturers web site.

Until this is wired correctly by you or a professional, stop using your system immediately.

 

[tmman]

What are you basing your hypothesis off of (from a mal-wiring perspective)? I should mention that turning the VC's down does only causes the system to go into protection when many of them are turned down at once. Other than that, it works fairly well and has been for about 8 months now. I can also ensure that the VC's are wired properly as per manufacturer suggested instructions. I have a feeling that much of this can be alleviated with proper setting of impedance levels at the VC but I unfortunately don't understand how to set them properly (what the values should be). Any further information would be helpful.

 

[agarwalro]

Seems you are misreading the impedance matching situation. The VC switch is a multiplier to get the impedance seen by the amplifier channel as close to 8 Ohms as possible. It needs to be on 1x unless you use more than 1 pair of speakers per VC.

Looking at Pg. 6 of the manual (mainly to confirm my aforementioned statement) for OSD SVC, for 1 pair of 8 Ohm speakers the switch needs to be at 1x setting.

2x is needed only if you have 3 or 4 pairs of 8 Ohm speakers per volume control or a combination of 4 and 8 Ohm speaker pairs per volume control.

On both the AudioPlex MJ1's, again from the manual, set the Protection switch to 'IN' and the VC connected to them at 1x. By setting Protection to 'IN' the MJ-1 does the impedance matching to 8 Ohm based on the number of speakers connected. That is why the VC is set to 1x.

I believe this setup will relieve you impedance mismatch situation.

NOTE: You should get another opinion. Distributed audio is not my forte.

 

[tmman]

Thank you for providing the information... I will make sure everything is set how you have described. Thanks again!