SDA-1(C?) impedance for new Onkyo receiver?

003

Hey guys I have a pair of SDA-1 speakers. They do not say A, B or C, but they look exactly like the SDA-1C speakers pictured here:
http://polksda.com/sda1c.shtml

Anyway I just got a brand new Onkyo TX-NR5007 receiver and for the impedance, there are two settings on the receiver. One setting is 4 ohms which says is for speakers with an impedance of 4 ohms or more but less than 6, and the other setting 6 ohms, which says it is for speakers with an impedance between 6 and 16 ohms.

Now I have tried to find the specifications of the SDA-1C speakers (I do have and am using that cable that runs between the speakers), and I found that the 1Cs are 6 Ohms, so I currently have the receiver set to 6 ohms.

Then I found people saying amps should be set to 4 ohms for the 1Cs and I am confused now. They seem to be working very well set at 6 ohms.

george daniel

you can try them on the 4 ohm setting,,won't hurt em',,look for any inprovement in bass/lower midbass, I have mine connected to the 4 ohm tap on my amp--good luck.

003

Just out of curiosity why are people recommending 4 ohms when the speakers apparently are 6 ohms? Also these are old speakers... is there any chance the rubber surrounds on the drivers could become brittle or anything? Any tips on caring for them so they will last a very long time?

Vette C6.r

003 wrote: »

Any tips on caring for them so they will last a very long time?

Don't crank the heck out of them.

george daniel

003 wrote: »

Just out of curiosity why are people recommending 4 ohms when the speakers apparently are 6 ohms? Also these are old speakers... is there any chance the rubber surrounds on the drivers could become brittle or anything? Any tips on caring for them so they will last a very long time?

Well, I have a choice of 4 or 8 ohms--after listening to both,I prefer the 4 ohm tap,, seems to have a tad better control over the bass/midbass--seems tighter,,or in one word,,,,experience

ChrisD

Leave it at 8 ohms. It's just a current limiter to prevent the receiver from potentially overheating, and as a result limits the amount of power the speaker can draw. This also causes the receiver to clip earlier.

dpowell

Grab a really nice common ground 2-channel amp and use your AVR as the pre. You'll enjoy your 1C's way more than running them from an AVR.

BTW, welcome to Club Polk!

cnh

WELCOME TO CLUB POLK!

dpowell and others are right. I run my SDAs with an integrated amp that can handle 4 ohm loads--it makes a difference.

Impedance is a 'relative' number. And the SDAs CERTAINLY do dip below 6 ohms quite often. That's one reason why so many use separates to power them. They are a power hungry speaker....no, they LOVE power. The more the merrier. But they also like QUALITY power (for example a 30-50+ watt tube amp will do wonders for them).

Lots of people have fried SDAs and their amps by not running enough power or running at too high of an impedance--like 8 ohms!

Also, when you set that Onkyo to 4 ohms it effectively LIMITS the current output and its power ratings drop SIGNIFICANTLY....probably down to about 60 or 70 watts at best. It becomes half the amp it was at 8 ohms and two channels.

Good Luck...

cnh

003

Thanks guys. Unfortunately I have absolutely zero room for another component, that's why I went for Onkyo's best receiver. If I had room and more money, I'd love a separate amp.

So are you guys saying that I can actually damage the speakers with the receiver on the 6-16 ohm setting, or it just won't sound quite as good?

I'd really like to not put it at the 4 ohm setting, because based on this report, the 5007 will drop to around 65wpc at the 4ohm setting, while it's around 150wpc at the 6-16 ohm setting... As always, wish I had more money and more space

I only have the Polks connected to the reciever, and then a small set of stereo speakers for zone 2. The reciever supports bridged amping, could I run it at 4 ohms and have the Polks bridge amped for more power at 4 ohms?

EDIT:
Well the receiver manual says you can seriously damage the reciever if you bridge speakers that are under 8 ohms... Will it really be that bad with ~65 wpc? polksda.com lists the 1Cs as recommending 50-500 WPC and a sensitivity of 90dB

Ron Temple

As others have said, the switch on the receiver is a current limiter, not a tap. Leave it at the 8 ohm setting and watch the heat.

003

Ron Temple wrote: »

As others have said, the switch on the receiver is a current limiter, not a tap. Leave it at the 8 ohm setting and watch the heat.

Well now I've set it at the 4 ohm setting and it still sounds fine. I really don't notice much of a change, if anything.

So if I have it on the 6-16 ohm setting, there won't be any greater chance of damaging the speakers or the receiver, provided there is sufficient ventilation?

Ron Temple

003 wrote: »

Well now I've set it at the 4 ohm setting and it still sounds fine. I really don't notice much of a change, if anything.

So if I have it on the 6-16 ohm setting, there won't be any greater chance of damaging the speakers or the receiver, provided there is sufficient ventilation?

I'm not sure how the limiter works, but if it's a brickwall at 65 watts, then you're limiting dynamics to stay within a safety zone. You might not hear this if you never push it. The 1Cs do dip below 4 ohms in a few places, but I wouldn't think you'd damage anything in the unlimited 6-16ohm setting and gain back the dynamics at spirited levels. That said, I wouldn't push it above 100dbs output for extended listening due to heat buildup (depending on the size of your room). You can test this by putting your hand on the AVR. It's been years since I've tried to run my 1Cs with just a receiver, but I do remember they sounded fine if I didn't push it.

003

Ok thanks for the info. I really don't hear a difference at the 4 ohm setting, so I'll leave it for now. I have a second question. Does anybody know if the TX-NR5007 is common ground? On the back of the speakers, it says to never used them with an amp that does not use a common ground.

dpowell

If you have a VOM, set it to the continuity test position and touch the black speaker outputs for the L and R channels. If you have continuity, you have a common ground.

003

You mean a digital multimeter? Yeah I have one but I am not to great with it. I took a picture, are you able to tell me what to set the dial to in order to test for continuity, or if I even can? Here's the picture (click to enlarge):


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Would I do this while the receiver is on and the speakers are playing audio?

dpowell

003 wrote: »

You mean a digital multimeter? Yeah I have one but I am not to great with it. I took a picture, are you able to tell me what to set the dial to in order to test for continuity, or if I even can? Here's the picture (click to enlarge):

Hard to tell from the picture. It is a bit blurry. If I had to guess, it would be the setting 4 from the top counting left. Usually at this setting, you can touch the two testing points of the VOM together and the VOM will beep and show a '1' on the display if there is continuity.

003 wrote: »

Would I do this while the receiver is on and the speakers are playing audio?

No. I would ensure all is powered off just to be safe even though there is probably little risk to doing this while it is powered on.