AA networks...

[richieb]

The way Dean and Chief went back and forth on this topic makes me think the Chief would like to see Dean on the business end of that lure -- what a fish tale that would be!

[Deang]

3 hours ago, BEC said:

Remember that I showed you a crossover that PWK used L-pads on.  They were discrete resistor L-pads at least.  I don't think he wanted to use them, but had to use them to get the speaker to work right.  I wonder if Roy is familiar with that crossover.

 

Dennis has a point too, that swamping resistor on those tweeters is knocking things down a bit. Even if just being used to smooth out a broad peak, it still produces some attenuation - and we know PK had a hand in those designs. 

[Deang]

12 minutes ago, richieb said:

The way Dean and Chief went back and forth on this topic makes me think the Chief would like to see Dean on the business end of that lure -- what a fish tale that would be!

 

Lol. I'm too fat, he could never haul me in. 

[mustang guy]

They make those big nets they use on piers in the ocean.

[Deang]

4 hours ago, wdecho said:

 

That is certainly another option but a little more involved for the average owner of heritage speakers. If I were to attenuate an AA network your way is the way I would do it too. I actually have built many crossover designs with Bob Crites 3636 autotransformer and float the secondaries which makes it a breeze changing the attenuation on the fly. I still say for the average guy who thinks his AA's are a touch too bright the L-pads are a fairly easy way to adjust the drivers to your room. IT can help tremendously to make your speakers more enjoyable.  

 

You must be new here. I used to be Al's licensed builder for both the Cornwall ALK and the Universal. I've built and sold hundreds of networks with the swamping resistor on the autoformer. I mostly sold these to people who like to play with different horns and drivers. In my own systems, I always used the A or AA.

 

 

[Deang]

14 minutes ago, mustang guy said:

They make those big nets they use on piers in the ocean.

 

Trust me, I'm pulling him in with me. 

[Deang]

So, until Roy comes back and starts chewing my *** again, let's do something I'm really terrible at (besides building networks) - math. 

 

You have this cool new autoformer that can do 1dB steps, but you don't want to use the swamping resistor. You'd like to attenuate from -3dB to -4dB. 

 

Might as well start from the top. 

 

You have a target crossover frequency, and you know the impedance of the driver at the target frequency.

 

                                1

C = _________________________________

 

  2(pi) x 400 (crossover) x 30 (reflected Z)

 

The driver is 15 ohms at 400Hz, but through the autoformer, the amplifier sees 30 ohms.

 

6.283 x 400 = 2513

2513 x 30 =  75396

1/75296 = .000013263 Farads or 13.263uF

 

Now we need to do something called "impedance scaling". We start by finding the the square of the turns ratio of the output tap we're currently using. The current tap is giving us -3dB, so

 

3(dB)/20 = .15

log10 = 1.4125 (expressed as 1.4125:1)

1.4125 squared = 1.995

 

Next tap is -4dB, so

 

4(dB)/20 = .2

log10 = 1.5849

squared = 2.5119

 

We now have the two numbers we need to get our impedance change ratio. 

 

1.995/2.5119 =  .794

 

.794 x 13.26 (original capacitor value) = 10.5uF 

 

Not so bad. The easy way is to use the data sheet Bob sends with every 3636 - where all of the math is already done! To get your cap value, just divide the number in the "TR/Squared" column into 2, and multiply by 13.

[erik2A3]

wdecho,

 

I follow precisely what you are saying, and we had traveled this ground very well many years ago on this forum.  I had experimented with numerous options for attenuating the mid-horn on both our La scalas and Klipschorns -- virtually all of which were 6dB/octave slopes in order to minimize parts count and complexity -- which is most suitable, in my view, when one is using low horse power amplification.  I also don't care for the sound of shunt elements, impedance equalization (zobel), swamping resistors (which I've used both on big Heritage horns, as well as back loaded horns using very expensive full-range Lowther drivers (which in the cabinet I'm using are a couple of dB more efficient than K-horns).

 

So, a simple first order network with true midrange band-pass, and simple, inexpensive yet entirely effective L-pad on the squawker, sans autoformer.  It was the most transparent sounding of any network I had used, including improved (recapped) klipsch Heritage Types A and AA.  The autoformer in A/B testing, in my opinion (which in my listening room is what matters!) threw a mild veil over things resulting in slightly softened transient response, dulling of leading edges, and so on.  NOT bad per se', but significant enough for me to prefer the subjectively better performance and exponentially lower cost of resistors.

[wvu80]

14 minutes ago, wdecho said:

Not hard to build but one must have a tweeter that will not fry with a simple 1st order crossover.

 

I also found that I do like the highs crossed over at a lower point, 4500hz. I believe the K55 drivers are better if relieved from this duty, reaching out to 6K.

 

We (OK, you, the smart guys) have discussed the AA almost exclusively without addressing the drivers.

 

William, have you swapped out the stock K-77's?  If so, to what?  I presume it was the driver that was the reason for the change to the XO.

 

What mid-driver do you use?  Is it the K-55-V (older) or the K-55-M? (newer with a smoother response at 5500 Hz)

[wvu80]

14 minutes ago, wdecho said:

I went with the selenium D220Ti driver with a selenium horn for the highs

 

Is the 220 mounted in the box, or external on top?

+++

 

I think you earlier mentioned you have tried more than 30 combinations of crossovers.  May I infer from that you could not find a "stock" combination that you liked?

 

There had to be something about the sound you didn't like if you swapped out the crossover, the mid horn, and every driver except the K-55-M squawker! 

[muel]

It is interesting that the designer of the Sonicap recommended Jupiters over the Sonicap for use in the B2 network except as the 20uf shunt.  

[Deang]

You were going into great detail about how an ALK-type filter works, as if I needed that explained to me - so it just seemed to me that you were relatively new here, and didn't know that I'd been building them for over a decade (I wasn't bragging). 

 

This thread started out about a comparison between my Jupiter AA build and the Klipsch AL-4.  I've never had anyone characterize my A or AA builds as making the loudspeaker "bright" or "too bright". The sound is smooth, open, and natural - no l-pads needed. 

[mark1101]

I removed the Jupiter caps from my NBS preamp because they sounded rolled off to me and also produced what I consider to be a "vintage" sound.  They produced a nice 3D image but after a month or so I could not get past how different my system sounded with the NBS in there with those caps in it.

 

I replaced them with Auricaps and my system came back to life.  Not a small change by any means.  The Auricap is much more open top to bottom and it restored life to my system as far as I'm concerned.

 

 

[Deang]

Exactly why I use them for these older designs. The Jensens have more loss, but they sound great too. 

 

You should try some polystyrenes - awesome as coupling caps. Hard to fault the Auricap though - double wrapped, with good lead terminations. 

[muel]

Jupiter rolled off?  Not my experience at all but I just use the 100 volt flat stacks in crossovers.   The NBS is a different application than a crossover.   For the NBS I use Duelands and VCaps in the VRD's.   Must be good synergy. 

[mark1101]

To explain better, I replaced a Peach with the NBS.  I would have expected them to be birds of a feather but they sounded completely different.  I knew something was up.  After talking with a few people everything seem to point to those caps.  Though I hated doing surgery on such a new and beautiful piece I just had to...........and I was right.

 

Maybe a better way to say it is that I found the mid-range to be very forward in the Jupiters.  You have no problems hearing the vocals.  That's for sure.

 

The other thing is that when you hold a Jupiter in your hand heck you could break a window with it.  There must be a ton of copper in those things.  They have serious weight to them.

 

I also removed the Sonicaps from my VRDs and installed Auricaps in those as well.

[muel]

Beeswax must be heavy.

Rolled off highs and forward midrange??  Do you remember or have a picture of which exact version these were?  

Didn't the Peach and Blueberry have Auricaps?  Seems I remember my Blueberry having Auricaps.  The NBS was very close in sound but far more silent background.

Craig left plenty of room to place just about whatever caps you want in there.

Whatever works for you I'd say... gotta stick with what works for you.

[mark1101]

There are pics of the Jupiters that came out of my NBS in the garage sale.  Probably several pages down now.  They are sold by the way.

[Deang]

Did you do the prerequisite 72,000 hours of break-in before evaluating them? :-)

[Deang]

On August 18, 2016 at 2:24 PM, Chief bonehead said:

L pads can make things worse than better.  if the impedance is consistent in the band you are trying attenuate, then adding resistance like an L pad will cause the entire band to get louder or softer.  if the impedance is not consistent in the band, then what will happen is that some parts of the band will get louder than the other parts or softer.  in other words it will not get louder or softer linearly.

 

In case anyone forgot what Roy said about this.

 

If the network is balanced properly, you don't need the added complexity of L-pads. You're having a meltdown because everyone isn't jumping on the L-pad bandwagon with you.

 

I have A and AA measurements out the wazoo. Where are your measurements?