Jump to content

Bi-Wiring & multiple impedance OPT


DirtyErnie

Recommended Posts

Had a thought about this:

I have a Scott 222C, it has 4,8,16-ohm outputs and two 0-ohm returns/commons. (Edit: per channel!)

 

I also have a pair of KG2.5 and a pair of CF2 speakers, both have WTW arrangement, 8 ohm tweets, and a pair of 8 ohm woofers in parallel. 

 

Thinking of splitting the inputs on the x-over boards, direct wiring the hi-pass filter to the 8 ohm OPT tap and the low-pass filters to the 4-ohm tap. Then each frequency band would be getting fed by the correct tap and reflecting appropriate loads back to the power amp.

 

Any good reasons to stop right there and come back to sanity?

Edited by DirtyErnie
  • Like 1
Link to comment
Share on other sites

Shouldn't harm anything except perhaps the balance between the lows and highs.  In other words, it may help, but it may hurt the overall sound quality only.  Those models were prior to dual sets of inputs being provided?  If so, too bad.  It would be an exceedingly simple way to test the theory...  Though that (separating inputs) could be an innocuous modification in and of itself, and maybe worth a try. 

Link to comment
Share on other sites

I like your idea.  The thing of it is, that by wiring the highs to the 8-ohm tap and the lows to the 4-ohm tap, you'll be sending nominally half the voltage to the lows compared to the 8-ohm tap.  The impedance will be "more properly" matched (likely), but the output level of the lows in relation to the highs will change (likely).  I'm guessing the result will be a brighter sound.  Maybe it will be more a more proper lows-to-highs balance, but maybe (likely?) the tweeters are matched correctly to the woofers in terms of output already and the experiment will fail in that regard.  That said, attenuating the tweeters by 3 dB if necessary (likely?), with both sets of drivers then fed from "proper" taps each, may yield a real sonic improvement (better control over the woofers?).  Maybe not...  Shouldn't cost very much more than your time to find out (and report back right here, of course!). 

Link to comment
Share on other sites

That's a question in my mine, too: where does this wiring scheme put the speaker load on the plate curves? It's likely the low impedance of the woofers was too 'vertical' of an operating line to begin with and they weren't getting powered quite right off the amp (was running from the 8-ohm tap). Setting that Load Line to it's correct position could only help, and with a tube amp that means more left-right (voltage) swing before the load line blows out the top of the plate curve (runs out of current). I'd think re-aligning the load lines for woofers and tweeters could only improve operating conditions for the power tubes and force less correction through the NFB loop. Fun mental exercise, this. Too bad the KGs are in my basement lab, not exactly a 'critical listening' environment.

 

That doesn't matter with solid state, but we're not talking about sand.

Edited by DirtyErnie
  • Like 1
Link to comment
Share on other sites

Question to be answered: if these speakers were designed for solid state drive, the woofers are getting +3dB for being x2, and +3dB for pulling 2x power from a solid state supply. Might bet on Glens thought of tweeters going +3dB...

Edited by DirtyErnie
Link to comment
Share on other sites

7 hours ago, DirtyErnie said:

Not quite sure what that has to do with the discussion at hand.

  My amp thoughts on this is to connect one speaker with the - to ground and the + to the four ohm connection. Connect the other speaker with - to the four ohm and the + to the sixteen ohm. 

  It does not parallel the speakers across any of the output transformer. Compare this to the other connection options. I have to think it will sound better.

Link to comment
Share on other sites

On 4/17/2019 at 1:40 PM, DirtyErnie said:

Had a thought about this:

I have a Scott 222C, it has 4,8,16-ohm outputs and two 0-ohm returns/commons. (Edit: per channel!)

 

I also have a pair of KG2.5 and a pair of CF2 speakers, both have WTW arrangement, 8 ohm tweets, and a pair of 8 ohm woofers in parallel. 

 

Thinking of splitting the inputs on the x-over boards, direct wiring the hi-pass filter to the 8 ohm OPT tap and the low-pass filters to the 4-ohm tap. Then each frequency band would be getting fed by the correct tap and reflecting appropriate loads back to the power amp.

 

Any good reasons to stop right there and come back to sanity?

Quite reasonable.  BTW, if you are posting here, some will question your sanity.  ;)

Link to comment
Share on other sites

15 hours ago, babadono said:

two loads off of different taps of an output transformer? @tube fanatic is this OK?

 

This question comes up frequently and I don't recommend doing it.  I don't have time to do a whole math presentation to make my point, but you can get the idea by looking at these links:

 

https://groups.google.com/forum/#!topic/alt.guitar.amps/6Sz-pDfQ_4I

 

https://www.diyaudio.com/forums/tubes-valves/162727-multi-tap-transformers-dont-windings.html

 

Personally, I doubt that any real difference in the sound would be noted.

 

 

Maynard

 

 

Link to comment
Share on other sites

Read both of the forum post links, neither seems like the situation at hand. Since each tap would be feeding a band limiting filter (crossover), only the pass-band frequencies would be able to get out of any given transformer tap. Third order crossovers would keep the overlap down to a reasonably small amount. Current/power won't be going where it shouldn't go.

 

How the Scott is set up for feeding speakers: there are two identical strips, one for each channel. Each channel has: two 0-ohm/neutral taps, and one each of 4, 8, and 16 ohms. Each tap is a screw terminal, suitable for bare wire or a fork lug.

Ultimately, this is a variation of Bi-Wiring, isn't it?

Edited by DirtyErnie
Link to comment
Share on other sites

Understanding how a multi-tapped output transformer works is relevant to any discussion involving simultaneous use of the taps.  How else is a person to know if what they propose to try is going to be a problem?  As is evident in the links, many have trouble comprehending the relationship between turns ratio and impedance.

 

Maynard

Link to comment
Share on other sites

26 minutes ago, tube fanatic said:

Understanding how a multi-tapped output transformer works is relevant to any discussion involving simultaneous use of the taps.  How else is a person to know if what they propose to try is going to be a problem?  As is evident in the links, many have trouble comprehending the relationship between turns ratio and impedance.

 

As for myself, I've professionally worked with and comprehensively tested transformers up to as big as a two-car garage, so I think I've got a pretty good grasp on turns ratios and taps.  What was suggested by this thread in and of itself could be a very good idea.  So long as sufficient care is taken to maintain impedance when attenuating as necessary, driving the two circuits with more-appropriate taps should prove to be a real benefit.

 

17 minutes ago, mboxler said:

On top of that, splitting the crossover does not create separate 4 ohm and an 8 ohm circuits, if I understand what is being implied.

 

I'm not so sure that you either understand it correctly or that you're right if you do...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...