SDA 1C-Tube friendly impedance? and other questions

Boywonder

I have a pair of SDA 1C's and have recently gotten the tube bug. I am presently running a newly aquired Athem PRE1 and a B&K ST-140 power amp that I have had for years, and I am considering a tube power amp.

There are lots of web discussions about speaker impedance curves and their effect on tube amps, ie tube friendly impedance curves that don't dip too low and are a not too capacitive (phase angle).

So, after searching the site here, I am wondering if anyone has any impedance curves for Vintage Polks. I am also trying to determine if it is possible to measure phase angle easily with minimal test equipment. Impedance plots should be easy with a function generator, multimeter, power amp, and a series resistor.

The 1987 review of the SDA 1C from the www.polksda.com site (Stereo Review) states that the minimum impedance measured 3.9 ohms but said nothing about phase angle.

Here is another (unrelated) question. Has anyone tried a single RD-0194 tweeter in the SDA-1C while leaving the bottom SL-2000? I assuming the top tweeter is the one that is not rolled off........I have a new pair of RD-0194's waiting to be installed in my monitor 10's when the veneering project is finished, and I am tempted to throw them in my 1C's while I am working on the other project.

Lastly, has anyone considered a sticky thread with "known-to work" mono amps?; there seems to be a number of folks sucessfully running dual mono's here but the data is scattered among lots of posts.

F1nut

Tube amps shouldn't have any problem driving your 1C's as long as they have at least 50 wpc.

00p225

Boywonder,

I've been running my 1C's with a vintage Eico HF-87 for the last couple of years. Prior to this with a solidstate McIntosh MC2100 - 100wpc, a solidstate soundcraftsmen PM840- 200wpc, and Jolida SJ801 tube integrated - 70wpc.

I believe the nominal impedance of the 1C's is 6ohms. I ran these for a few months connected to the 4ohm taps on the 35wpc eico. Nice sound, but a bit bloated in the 50hz and below region, and a bit too warm for my tastes. Tried the 8hm taps, bass is tight, soundstage and speed opened up by a wide margin. No issues yet using the 8ohm taps (I was worried) with about 3000 hrs of use.

Soundwise, the tube amp really eats the others alive. Volume wise, the little 35wpc Eico sounds 80% as powerful as the Soundcraftsmen. I don't remember the db ratio, but I think it takes 4 times the power to sound twice as loud db wise. Someone can chime in on this one. The 70wpc Jolida sounded comparable in power to the soundcraftsmen. With much better midrange, but compressed soundstage (mediocre parts, caps pots etc., I should have upgraded some internals). Try a tube amp, I don't think you'll go back to solidstate.

Boywonder

Great info, thanks. I believe that it is 10x the power for double the volume (+3db), since it's logarithmic.

I recently picked up an anthem PRE1 on the local CL and now I've got tube fever. The pre brought more "life" into the music. I'm running it with a stock B&K ST-140 to hold me over until I find a tube amp. Prior to that I was running a Parasound P/HP-850 and Yamaha M4, which is a little bright, especially with the stock SL-2000 tweeters in the 1C's in my very "live" uncarpeted room. I am limiting my search to stereo tube amps (Primaluna prologue 5, CJ Premier 11 or MV75-all used) since I am a little nervous about the common ground issue. My SDA's are pretty mint and I don't want to blow them to smithereens being an idiot. I suppose that I could buy/build the IC that allows non common ground amps to be used.

I'll probably end up with something between 35-70 watts, although I'm trying to lean more toward 70 watts in my search. I am also planning on trying both the 4 ohm and 8 ohm taps on whatever I end up with.

00p225

Interesting, I also ran the Parasound P/hp-850 with my 1C's, and at the time the soundcraftsmen. I agree, mine was pretty strident also. I contribute this more to my stock tweeters with that spike around 13k I believe.

Best of luck on the tube amp. It should really be a tasty combo with your new preamp.

Btw, I also ran my brothers Scott Nixon Tube dac with my tube pre and amp combo. Sounded wonderfull.:p

george daniel

I've got a little 40 watt anthem tube amp connected to mine and they could not be happier,,,you might want to give a listen to something from the Manley line of gear. Good luck.:)

00p225

I've read a few reviews on the Primaluna prologue 5, and their strengths point to a huge soundstage, strong bass, and smooth midrange . Sounds like a perfect match for SDA's. Also, have you thought of upgrading your tweeters? I'll be upgrading mine in the future. Last I checked they would run just under $200 for 4 to a club polk member.

Boywonder

Yes, I have a brand new pair of RD-0194's waiting to go into my monitor 10's when that project is completed. I imagine once I hear them, I will be ordering another 4 (or maybe even 6, ouch!) to do the 1C's and maybe the RTA-12C's.

I am contemplating putting them into the top tweeter position on the 1C's while they are not being used. Or, better yet, put the pair into one of the 1C's for a L/R comparison, leaving the SL-2000's in the other 1C.

Marty913

Boywonder wrote: »

Yes, I have a brand new pair of RD-0194's waiting to go into my monitor 10's when that project is completed. I imagine once I hear them, I will be ordering another 4 (or maybe even 6, ouch!) to do the 1C's and maybe the RTA-12C's.

I am contemplating putting them into the top tweeter position on the 1C's while they are not being used. Or, better yet, put the pair into one of the 1C's for a L/R comparison, leaving the SL-2000's in the other 1C.

I'd be very much interested in the results. I have a pair of 2's & 1C's and the dimensional tweeter isn't worth the upgrade from 2000's. On the other hands, if I could get benefits in both sets with just 4 tweeters, that would be worthwhile. Let me (us) know whatever you decide to try.