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Discussion Starter · #1 ·
First off thanks for reading and helping out.

Here is my system Basically all Crown vintage stuff. DL2 preamp controller, EQ2 equalizer, PSA-2 power amp and an OC150 control center, which is just for speaker switching and power monitoring.


My speakers are Rectilinear III's . What I am trying to do is to add the Rectilinear XI's. Not to improve sound quality, the III's are great. It's a big room and I'm trying to improve the sound field dispersion.


When I play them through the OC150 control center (they are hooked up in parallel) they sound good, but I get reduced bass output from my III's. That's a no no since the III's have great bass through the Crown equipment. They are both nominal 8 ohm speakers. This gives a nominal 4 ohm load to the amp. What I think is happening is the current draw through the both lines of the parallel circuit will be nominally equal, of course this assumes that the impedance is a constant which it is not. Given that simplicity the big woofer of the III will be starving for power, at least that is what I think.

If I'm not right tell me and tell me how to fix. I was going to put a 32 ohm resistor in series with the XI's that will raise the overall impedance that the amp sees to 6.67 ohms and more importantly reduce the current draw to the XI's. Aside from the heat of the resistor will this work, or am I all messed up? What will help?



Thanks


Jim
 

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^^^


possibly... although it's likely that they'd clip if starving for power....


more likely... the second set of speakers is causing cancellations in the lower frequencies...
 

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I seriously doubt that you are overloading a PSA-2 at 4 ohm nominal impedance. If you were, the IOC would let you know. Assuming you have already checked phasing, try changing speaker locations. I would first set the IIIs and XIs side by side and make them play nice together before moving them apart.
 

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Discussion Starter · #4 ·
I agree, I don't think the PSA-2 is overloaded by any means. I just thought that maybe in the parallel circuit that the woofers on the III's were not being starved by the XI's. What I also tried which makes me believe that to be true is that as I raise the volume the little XI's get louder faster. I can't turn the system up too much for fear of hurting them. I still have not fused the system. I will check the phasing again to make sure all my black and red wires are in sync.

I was thinking of putting a volume control in series with the XI's that way I would have a variable resistor to control volume and power going to the little guys.


Any more thoughts?


Thanks

jim
 

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Quote:
Originally Posted by authorjim /forum/post/19589154


I agree, I don't think the PSA-2 is overloaded by any means. I just thought that maybe in the parallel circuit that the woofers on the III's were not being starved by the XI's. What I also tried which makes me believe that to be true is that as I raise the volume the little XI's get louder faster. I can't turn the system up too much for fear of hurting them. I still have not fused the system. I will check the phasing again to make sure all my black and red wires are in sync.

I was thinking of putting a volume control in series with the XI's that way I would have a variable resistor to control volume and power going to the little guys.


Any more thoughts?


Thanks

jim

A series resistor may help a lot for balance in the room, but I would first make certain the phasing was correct. The easy way for woofers is with a flashlight battery. Just make sure all 4 woofers move the same direction when you touch speaker wire to battery. A finger held lightly on the cone makes it easier.


I would next place all the speakers close together, and connect only the IIIs. Using a mono signal, pan L to R to L several times. The sound qualities should not change as it moves from speaker to speaker. I would then repeat this procedure with the XIs. If everything is fine so far, connect the IIIs to the left channel and the XIs to the right and repeat panning the mono source. The sound quality will change, of course, but frequecies shouldn't drop out as you pan through center.


I could be way off-base here, but if I am interpreting your post correctly I suspect one driver out of the lot is miswired.
 

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Being vintage equipment, it won't be the first time that electrolytic capacitors (either coupling or power supply) have gone soft.
 

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Quote:
Originally Posted by Speedskater /forum/post/19611143


Being vintage equipment, it won't be the first time that electrolytic capacitors (either coupling or power supply) have gone soft.

I agree. I think the OP should try hooking the speakers directly to the amp without the control center to isolate the problem.
 
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