300B SET question..seriously..

[Hardhead]

You say the center channel isn't "THAT much of a difference." That makes me wonder about the level of the center channel amp versus the left and right channel amps. In other words, the center channel volume may be a little too low. According to Paul Klipsch, his statement being based on Bell Labs audio experiments, the center channel should be 6 dB lower than the left and right channels. That makes the center loud enough to anchor the location of the center channel but soft enough not to interfere with the left and right separation. When the volumes of the three channels are adjusted correctly, the difference isn't earthshaking, but the center channel is much more localized in the middle no matter where you are in the room.

What I'm trying to say is that, when adjusted correctly, the center channel is separated more from the left and right channels no matter where in the room you stand, yet the left and right channels are still strongly separated, too.

[steve]

Hardhead

true..I've measured it with a decibel meter using white noise, or test tones..problem is I don't know where I shoud be taking that measurement..at my listening position? A meter out from each speaker? Anyway, what I've found..is that when I do it by "ear" when it's lower, I don't notice it being there really, and when it's high enough I do notice it, it's detracting from the real stereo effect. I also wonder if the difference is the stock xover in the Belle, and Al K's in my Khorns.

But to tinker is what I like to do..so..do you know where I take this -6db measurement from? Thanx..

Steve

[Hardhead]

As far as from where to take the measurement, as long as you're consistent, it shouldn't matter. If you take your reading at 1 meter away from the left speaker, then take it 1 meter away from the center speaker. Having said that it shouldn't matter where you take the reading, I would take it a little farther away, though, just to give the drivers' outputs a chance to blend a little.

I'm very surprised that you're having a problem with this, since I've never heard anyone else talk about it. In the 33 years I've had my Klipschorns and Belle, I've always been able to balance the levels very quickly and easily by ear. The correct level just seems to snap into place when I turn the volume knob. I'm sure there's nothing wrong with your ears, so that makes me think it may be a room problem or something like that.

I've never had different crossovers or different drivers in my Klipschorns than in my Belle, so that could be a problem as well. There may (or may not) be a tonal difference in the drivers and/or crossover of your Belle compared to your Klipschorns that makes you hear one or more audio bands louder or softer on the Belle. Lots of variables to work with to solve the problem. You might try seeing if your Belle sounds exactly like one of your Klipschorns. If not, you may have a driver/crossover conflict.

[steve]

well, I've always complained about the room..what with a sloping ceiling and all..but it's actually gotten better with room treatments. And I tend to think the difference in tones IS the different crossovers. I just haven't decided to spring for another Al K crossover..yet..as the Belle is so new. But, when hearing the difference between the two, I tend to lean towards Al's crossovers..

I did have the center -6db down at one meter away..guess I had the right idea.

Again, I'm not saying it's BAD..I just am not sure I really needed the center..how far apart are your KHorns? Mine are 21 feet apart..thanx

Steve

[oldbuckster]

Steve, I know what the room problem is.............................It's that Hendrix Mural on the wall, Take it Down..................and send it to Me..........................

I'm sure that was you......[]

[Hardhead]

In their present room, my Klipschorns are 24 feet apart. I've had them further apart (and closer together) in other rooms over the years.

I've never had a problem with the "hole in the middle" effect with just the left and right speakers on, though, even at low volumes. The phantom center is always there, but the center is more solidly there at every place in the room when the center speaker is playing.

What squawker and tweeter drivers do you have in your Klipschorns and Belles? The difference in tone, if any, between the Belle and Klipschorns may not be due solely to the different crossovers.

I also think it may be worthwhile to take a look at your mixing box to see how you've constructed it and whether the resistors you have in there are the optimum value.

[NOSValves]

2nd. The impedance of your speaker may take a dive at low frequencies. Using the 4 Ohm output of your amp will help the amp keep the amplitude at the low impedance dips in line with the rest if the frequency spectrum.

I believe he mentioned he has Al K. networks if so they present a nice constant 8 Ohm load. No variation at all.

This is most certainly the low end frequency roll off of the amp and bridging it will do nothing to help this and like mentioned above would be a detriment to what the amp now does well.

Craig

[steve]

Oldbuckster..yeh, that was my tapestry alright..gotta keep it though, probably makes things sound better!

Hardhead, the drivers in My 83 Khorns and my 05 Belle are stock..I'll have to do some research to see if they're the same..but I'm guessing they're not. Again, I'm splitting hairs here, as I'm sure the sound isn't THAT far off from one speaker to the other..Also, Tom Mobley constructed the mixer box for me..I'll look at it, but have no doubt he used quality materials.

Craig, thanx for the input..and yes, I do have Al's xovers..that was a good investment.

Now if I could just hear a pair of your VRDs!

Sometimes I wonder if having these ultra sensitive, hard to feed Khorns are worth it! Well..at least until I hear someone else's brand of speakers! Then it becomes clear to me why I bother..

Steve

[Hardhead]

I'm sure Tom did an excellent job of putting the mixing box together, but the quality of the resistors really wasn't what I was talking about.

Depending on the input impedance of your amps, you can select values for the mixing box resistors so the resistors work as a voltage divider (they do anyway) between the main and center channels to the effect that the signal going to the center channel is always 6 dB lower than the left and right signal. That way when you change the volume of the preamp up or down, the level for the center channel changes stays 6 dB below the signal for the main speakers. Using the right values of resistors, again depending on the impedance(s) of your amps, you can fine tune the level of the center channel right down to a tenth of a dB if you want, and you never have to adjust it again.

[steve]

Hardhead

ok..I misunderstood the statement, misinterpeting the word "value"..sorry.

Right now, there is a volume control built into the box, but of course, the way you describe it sounds a lot better i.e. no adjustments! So, excusing my ignorance, how does the input impedance translate into dbs? I'm good at math, but no electronics training here!

Both amps are the same, the stereo and mono one, and the input impedance is 100 Kohms. What value resistor(s) would I used in a fixed configuration with no volume control? (that, if I may ask for free advice)

Thanx

Steve

[edwinr]

....This is most certainly the low end frequency roll off of the amp and bridging it will do nothing to help this and like mentioned above would be a detriment to what the amp now does well.

Craig

Good point you make, Craig. So maybe there's something else that could be done to improve the low frequency response without changing amps. Perhaps he could look at the corner seal of the Klipschorns?

P.S. Actually I should stop beating around the bush. Steve, if you want some low frequency 'slam' then you'll have to go for something with more drive - maybe a pp tube amp with 40 to 50 watts per channel. SET amplifiers are not for everyone.

[steve]

Don't forget I tried a brand new McIntosh MC275, and didn't care for it compared to my SET! I guess I don't get the difference between a push/pull and other tube amps. Would that Mac be considered a PP?

[leok]

Steve,

If the McIntosh didn't work (same lack of fullness or was it something else?), maybe it's not the amp at all. Have you tried going straight from the cd player to the amps in stereo only (skip the splitter for now) Does the cd player have a volume control? Otherwise you'll get way more amplitude than you want? Do you have access to a passive volume control? Maybe the preamp is the problem.

I did a little research on your amps. Nothing obvious. Within its amplitude capabilities (which is way more than I generally want), it seems bass should be fine.

Is the KHorn woofer phased correctly with the upper two drivers? Check how they are wired to the crossover.

Did you install the Al K crossovers? Do you have the old ones? In what way was the sound from them different?

Based on everything I've read so far in this thread, including your McIntosh comments, I question whether the amp is the issue at all.

Leo

[LousyTourist]

Dang Steve, maybe the SET amps you are using (of which I know nothing) are the problem.... usually the output xformer has a lot to do with the sound, so you aren't going to find 'cheap' SETs that work well.

When I went SET I went pretty high end and I have never looked back. My amps weigh about 40 lbs apiece so that's 5Lbs/watt.

Good luck!

[steve]

Leo

I have gone straight from the CD player to the amp, but the CD player's volume control was useless. It went from loud on step 1 to overboard on the volume at step 2..I then ran it thru a passive volume control, and I had more control, but it still sounded a bit "thin".

As for the McIntosh, the amp sounded too laid back for me. The McIntosh preamp sounded wonderful with LPs, but like the Adcom, it too sounded thin with CDs. I have tried other CD players with the same results..although the AH! is still the desired player.

I think I may be making too much of this whole thing, and the possible culprit is my not liking a lot of digital recordings..a few, and I mean a few are quite good..they actually do sound "full", and I have some volume control using the preamp. But for most, they sound thin, no (or little) bass, and the louder they go, the worse it gets! The highs get higher, and the lows go away. Before the anti SET camp jumps in here, I get the same thing with SS, only the highs get even more shrill! The bass still takes a nosedive! LPs don't do this, although, yes, any surface noise is apparent.

I was wondering what you meant by the "amplitude"? Would putting that passive volume control between my CD player and preamp give me more control of the volume using the control on the pre? I.E a more gradual rise in volume as I turn the knob? Would I be losing any sonics?

Like I have mentioned before, I think I may be making too much of this. All my complaints, but I have never heard a (local) rig come even CLOSE to what I am running!

And, Lousy Tourist..thanx..but these SETs were built by a reputable name brand company..I don't think they're the problem. And they weren't "cheap" unless 1500 apiece is cheap..and if so..well..OK..they're cheap.

Thanx all for input.

Steve

edit add..Leo, yes, the xovers are correct in phase..and they sound a lot better IMO than the AK2s that I replaced them with..again, I can get wall shaking bass with a handful of CDs and most albums..but not MOST cds..maybe that "amplitude" thing??

[edwinr]

Steve,

If the McIntosh didn't work (same lack of fullness or was it something else?), maybe it's not the amp at all.... Based on everything I've read so far in this thread, including your McIntosh comments, I question whether the amp is the issue at all.

Leo

There's always a chance it isn't the amps. But in saying that, I wouldn't recommend the MC-275 if you're after a little boost in the lower frequencies - I found the MC-275 a bit soft in the bass, that's why I didn't buy this amp.

I do agree that before any major component change, we should make sure that everything is working to it's optimum. Then any changes we do make are for the right reason.

[leok]

Well, If the McIntosh was too laid back (but full enough?) and SET is thin, and the SET sounds the same with a passive volume control, I'd say you are likely to be hearing differences in amps.

Something has occured to me in going over this thread. Again, comparing amps within their proper operating envelopes, there are two considerations: 1) technology (ss, pwm, SET, tube pp, etc, and then 2) implementation (or voicing).

I wasn't happy with my stock Moondogs. I worked on them until they had the frequency extension and dynamics I think the technology can, and should deliver. But others may think the sound of a stock Moondog is great. The technology provides a platform with certain sonic possibilities: with SET, for me, it's vanishing distortion at very low power. The technology can then be customized to bring out certain characteristics. usually there are tradeoffs, some in cost, some in sound.

A differently "voiced" SET may, in Steve's case, do the trick. Maybe he's hearing the "sound" of the traditional air-gapped transformer. Maybe a more expensive transformer or change to ultrapath topology would fill things out .. hard to say.

But, for people who can't customize an amplifier, I guess it becomes a matter of trying different amps until the correct one is found.

Steve, have you tried a pwm amp? I happen to have a loaner P6D. If you'd like to try it as a reference I'll send it. The nice thing about the P6D is, it is extremely neutral with good frequency extension. Let me know if you'd like to try it. Unfortunately, it's not for sale and I do want it back, but it might give you some ideas about how to procede.

Leo

A ss amp, or a tube amp with feedback, such as the VRDs, may

[steve]

Leo

that's an extremely generous offer! What exactly is/does a P6D amp do? Thanx

Steve

[leok]

The P6D is a very small, 8Watt/chan, stereo, pulse width modulation amplifier. It is similar to a few other 8 or 15 Watt (depending on how they are measured) amps around except that this circuit bypasses the input capacitor that other circuits use. I found that any cap I tried in the input had some kind of sonic signature. So I finally figured out a way to skip the cap altogether. The amp has its own volume control, so I recommend initially taking input directly from a cd player or phono preamp. I developed the amp during my initial search for an amp with low distortion at low power. It's based on a Tripath integrated circuit.

The things like about Tripath's pwm is it's quiet, very low in distortion, and neutral to the point of being astonishing.

Send me your address (mail on this bb works) and I'll work on getting it to you, with instructions,

Leo

[Hardhead]

Steve--

I'm sorry, but I don't know how to do the math to figure attenuation, although I know that it would be a series resistor you would use and that the values of series resistors are additive. I looked at this web site and let it do the calculations for me: http://www.troester.org/ls/lpad.html . You would be looking at the single resistor part of the "Calculate Resistor Network" part of the calculator. This calculator lets you plug in the attenuation you want and then tells you the resistor value to use. For 6 dB attenuation into 100K input impedance, it looks like you need a 99.5K resistor for each side of the mixer.

You probably won't be able to find resistors of the exact value the calculator suggests, so you can plug the values of the resistors you can find into the "Calculate Attenuation" part of the calculator to see exactly what attenuation you'll get with each value of resistor you can find.

I ordered several pairs of resistors with close tolerances (the Vishay/Dale metal film 1% are very quiet and sound good as well) so I could test every other tenth of a dB between -6 dB and -7.5 dB. Mouser has a very wide selection at 21 cents each for the 1/4 watt, so the wide selection didn't cost a lot and I got exactly the center channel level that sounded best to me (about -7.1 dB). Your mileage will vary, of course.

Having said all that, unless the current resistors are such a high value that they choke off the high frequencies (doubtful), you probably won't get a tonal change with different resistors, so you would need to look elsewhere to solve that problem if it exists.

Good luck with it.