[stef2]

Hi. Here is my problem, maybe someone can help, I am a bit confused with those impedance matching things...


I am using a Kenwood AR404 amplifier for my whole house audio system. It has two sets of outputs (A and B). There is a four way splitter on the A output and another one on the B output, both splitters are model BTech BT913. Here is the description of the splitter from BTech's site (sorry I cannot link to the original page):

Quote:
BT913

PREMIER 4-WAY LOUDSPEAKER CONTROL

(with HEADPHONE SOCKET)



The BT913 Controls up to 4 pairs of loudspeakers connected to one stereo amp. Also has a headphone socket for monitoring. 4mm gold plated sockets accept banana plugs or bare ended speaker cables.


200 Watts per channel

Headphone socket with amp protection

Accepts cable up to 6mm in diameter

Screw terminals ensure solid connection

Using headphone socket doesn't mute speaker sound


The BT913 employs a special Parallel and Series switching circuit to protect the amplifier. Regardless of which loudspeakers are switched on, the amplifier load will not fall to less than half that of the loudspeakers in use. i.e. If using 8 ohm loudspeakers the minimum load will be 4 ohms. Nearly all amplifiers will accept a load of 4 ohms.

That way, I have eight pairs of speakers in my house perfectly working in any combination.


The problem happens when I try to add in-wall volume control to those speakers. I have bought two NON impedance matching volume controls for two pairs of those speakers. When I connect those controls, other pairs of speakers begin to play badly (not the pairs directly connected to the controls). Their sound becomes faint and distorted on one of the other pairs, on another pair one of the speakers stops playing. Everything plays well when I bypass the volume control...


It seems to me that this problem has something to do with impedance...but I am not sure. I think I should try impedance matching volume controls, but before buying those, I would like to know if there is any chance this will help, since I cannot return those.


Any Idea? I would be very happy to see (or hear) my setup finally working properly!

 

[Brian B]

Is A and B paralleled or serial on your Kenwood?

 

[stef2]

Well, I just re-read the manual, but unfortunately I cannot answer your question...is there any test I could do to detremine if it's serial or parallel???

 

[Brian B]

Disconnect speaker B and select A+B on the receiver. If the sound goes out when you turn B on (with A already selected), then they are in series.

 

[stef2]



Quote:
Originally Posted by Brian B /forum/post/13039396


Disconnect speaker B and select A+B on the receiver. If the sound goes out when you turn B on (with A already selected), then they are in series.

OK. I tried it and the sound doesn't go out when I turn B on with only the speakers connected to A. So A and B should be in parallel? Then how can I solve my problem???

 

[CVanMeter]

The problem is your running two speaker selector boxes, each designed to provide a 4 ohm load for the receiver via their impedance matching circuitry. Little doubt your A and B speaker jacks are ran parallel off the receivers amps. So basically it's amps is seeing two sets of 4 ohm speakers connected to it, requiring a 2 ohm load which it is not designed to run. The only way I can see trying to make what you have work is to wire the speaker selector boxes in series. Not certain it will work, but worth a shot.

The sure fix would be to replace them with a single 8 zone speaker selector such as the Phoenix Gold DSSM-8 or

Speakercraft SWTS-8500 along with standard volume controls on all 8 zones. A cheaper and just as effective solution would just be 8 impedance matching volume controls as you stated. You can often find inexpensive versions such as those made by NXG for around $20 per volume control.

 

[stef2]



Quote:
Originally Posted by CVanMeter /forum/post/13042499


The problem is your running two speaker selector boxes, each designed to provide a 4 ohm load for the receiver via their impedance matching circuitry. Little doubt your A and B speaker jacks are ran parallel off the receivers amps. So basically it's amps is seeing two sets of 4 ohm speakers connected to it, requiring a 2 ohm load which it is not designed to run. The only way I can see trying to make what you have work is to wire the speaker selector boxes in series. Not certain it will work, but worth a shot.

The sure fix would be to replace them with a single 8 zone speaker selector such as the Phoenix Gold DSSM-8 or

Speakercraft SWTS-8500 along with standard volume controls on all 8 zones. A cheaper and just as effective solution would just be 8 impedance matching volume controls as you stated. You can often find inexpensive versions such as those made by NXG for around $20 per volume control.

Well, the problem is that all of my speakers play very well in any combination when I connect my first 4-way splitter to output A and my second to output B. The problem happens when I try to add a volume control to one (or any number) of speakers. Would it work using an impedance matching volume control? and if so, how many pairs of speakers should I tell the volume control to *see* ? I mean a total of eight pairs are wired, but not every pair will be selected all the time, sometimes one, sometimes two pairs,. etc...Does this affect in any way the jumper selection on the volume control?

 

[fedders]

Installing a non-impedance match VC between your BT913 and the speakers should not make any difference on your current set-up. The impedance that your receiver sees should remain the same.


I'm frankly surprised that your receiver is even able to handle the 2 BT913's that you have hooked up. The IC amp based Kenwoods usually don't do well with anything less than 8 Ohms.


You may want to consider impedance-matching VCs for all your speakers to insure the receiver always sees 8 Ohms or less and the volume in each room is not dependent on whether you turn on more pairs or not.


Or, as CVanMeter suggests, get a quality 8 pair speaker selector that has impedance correction built-in.


Carl