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Discussion Starter · #1 ·
Hello. I just ordered some Rockets and have a question. Since the Rockets are 6 ohm speakers, should I set the Switch on my DA4ES to 4 or 8 ohm?


Also, I saw in the manual where the power output of the DA4 actually goes down as the ohm load goes down. Isn't that exactly opposite of what most seperate amps do?


What am I missing?


Thanks! David


PS I can't wait to get my Rockets (550 / 200)!
 

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I think the RSC200 center is 4 ohms, still most people in the know recommend setting those to 8 ohms,


The 4 ohm setting may limit the output...or it may just make the Circuit protection be more sensitive ...


I tried both settings on my Yamy, and ended up on 8 0hms, but there wasnt much of a difference. I really dont think those switches do much, but Im no engineer ...
 

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I am new to this as well, so this is just my guess. I think the 4 or 8 ohm settings on the back of an amp are the minimum impedance settings the amp will likely encounter. An 8 ohm speaker will probably have a minimum impedance of about 6 ohms sometimes, and a 4 ohm speaker will likely go evern lower.


I think it would be safest to set your amp to the 4 ohm setting, especially if the speaker is rated at 4 ohms. I run a pair of NHT 1.5's, which are rated at 8 ohms. However I am running them at 6 ohms, I think they sound better at 6 ohms compared to when they were run at 8 ohms.
 

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Discussion Starter · #5 ·
bigwally,


Excellent little piece there! Thanks a lot. That is exactly what I wanted to know.


Now, how about the power issue? Why does the receiver put out less power into less resistance?


Thanks! David
 

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Perry, without considering the switch for a moment, lowering the load impedance will allow an increase in current flow for a given output voltage (dependent on volume setting, until the power supply runs out of current), just as you deemed logical.


The switch compensates for that natural current increase by lowering the output voltage at that same volume setting, which reduces overheating. The article referred to the amp's output impedance, which means the source's ability to not be affected by the load.


As an example, a D-cell has a lower impedance as a source than a AA-cell has, even with the same 1.5 volts. Low output impedance is what determines an amp's damping factor, which is how an amp maintains control over a speaker cone's motion, especially the woofer.


Anyway, the idea is that the switch makes the amp put out less power despite the lower impedance, because of the lowered output current, which is because of the lower output voltage. As you said, this would not occur without resetting the switch.


Let me know if you want to read an extended explanation I wrote about this phenomenon. It is about amp bridging and other stuff.
 

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David,


I also own the Sony STR-DA4ES. I bought it for several reasons including a great price ($608) and the bass and EQ flexibility. I have a satellite/powered sub system (Energy Take 5) that is very easy on the amp. It has speakers that do not drop below 7.5 ohms and has a built in 90Hz high pass filter.


Unfortunately, the amp on the DA4ES is not exactly a brute. You are correct. Theoretically, an amp should produce twice as many watts at 4 ohms as at 8 ohms. In practice, most amps including the amps on medium to high end receivers usually produce considerably more wattage at 4 ohms than at 8 ohms. Some of them don't list 4 ohm specs at all for UL reasons. Always set the switch to the 8 ohm setting only.


This Sony receiver is an exception. It seems to produce excellent results with one or two channels operating, but not equal to some of the competition with all channels operating. There is some question as to whether all channels actually need max power simultaneously in real world music and movies. There are a lot of threads on the Internet about this issue with the DA4ES including reference to the Stereo Review, January 2003, test of the DA4ES and Sony's amp specifications. Check it out.


Speakers frequently vary considerably from what it listed as the nominal impedence. Check for any reviews on your model if they list the minimum impedence. In actual use you might not have any problem at all driving the Rockets with the Sony, especially if you have a powered sub which takes a lot of the power strain off the receiver's amp, or if you don't play at very loud levels. After you break in your new speakers I would put them and your DA4ES thru a work out. Make sure that the combination will play as loud as you like with out any problems. That is, without shutting down the amp or exhibiting any audible complaints. Happy listening with your new speakers.


RR6 :)
 
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