From DHAs to ALK Jrs complete

[jhoak]

The conversion from DHA crossovers to ALK Jr crossovers has been completed. All that's left to do is install them and get to listening.

Here's the "before"

And the "after"

I'll be letting them play for a few days before I make any broad comments on the sound or the changes. Frankly I don't expect to hear a "night and day" difference. I found the DHAs to be a bit bright even for my 52 year old ears. I actually prefered plain vanilla Type-As until the volume knob got cranked clockwise then they just sort of fall apart. Hopefully I'll end up with something I like at normal (low) levels and also at occasional room shaking levels. Time will tell.

Many thanks to Al K for the design and to gothover for the idea to to convert the DHAs.

[Guest David H]

Looking good, I am sure you will pleased with the results.

Dave

[jhoak]

Well they're in and playing and have me scratching my head. [:^)]

What I'm hearing is less mids and highs and the result is as though the bass has been turned up. So much so that I've turned off the subwoofer until I can get it dialed back in right. Not in a bad way at all. Just different from what I've been listening to for a while. Now I'm curious as to what if any changes will take place as all the new parts settle in.

Whoever says that La Scalas don't put out any bass has never spent any time with a pair. Mr. Santana and crew are currently reminding me of just how much bass a pair of La Scalas can produce. []

[Al Klappenberger]

Jhoak,

I think Dean Wescott has the explanation for what you are hearing. The DHA is a 1st order network. The Jr has higher order filters on the squawker / tweeter. The result is that there is more total energy coming out of the high section (tweeter and squawker combined) with the DHA. This gives you the illusion of reduced bass. You also have less driver overlap with the higher order filters. I suggest that you take note of the sweet-spot and of smoothness throughout the room. It should be better with the higher order network. You will find this is rather hard to do unless you switch them back and fourth several times. I suppose the DHAs have been stripped for parts making that impossible though. The higher order network will probably seem to have less "ambience" then the higher order network at lower levels. Crank it up a bit as part of your testing too.

Al K.

[Marvel]

I use a DHA2, which adds (among other things), a resistor across the input of the autoformer, turning it into a constant impedance network.I brought my mids down a notch or two, and the balance is superb. I also use an APT150, which I found smoother than the K77.

When I compared them to John Albright's ALKs, I found there to be little audible difference. I don't crank up the gain though. Al's look a lot prettier than mine, but that's a different story, and if money hadn't been so tight, I just would have bought a pair from him. [Y]

Bruce

[Al Klappenberger]

Marvel,

There's a bit more to it to making a constant impedance network than just adding the 10 Ohm resistor. The entire network needs to be designed for it. The DHA wasn't my design but If I had done it, it would have been very similar. It is a good 1st order design. That make this a true comparison of two gentle slope type networks. I think the difference will be small though and will probably show up when the volume is cranked up a bit.

Al K.

[jhoak]

Thank you Mr. K. Your explanation makes perfect sense and accurately describes what I am hearing.

I had stated earlier that I really didn't expect much difference. I was dead wrong. What I am hearing out of my speakers is completely different. It's going to take a bit of getting accustomed to. I always liked them a lot before but now they've moved to a whole new level. Of course the dramatic change in character brought on by a hundred bux worth of parts and a couple of hours of soldering has got me wondering what the "next level" is.

I think the change is best described by the word "smoothness". As a result of a LOT of childhood ear problems and more surgeries than I care to recall I was left with a particular sensitivity to high frequency distortion. What I frequently hear when the volume gets high is buzz much like a blown driver. Over the years there have been very few speakers that have not brought about this buzz at high volumes. Mike Lindsey's KHorns did not trigger this effect and I made a point to mention it to him. My La Scalas could and did occasionally cause the "buzz" in my ears but only at high volumes (100dB+) and only with certain content. I can now report that I do not experience it with my speakers. I'm not sure why but I'm going to enjoy the results.

Suffice to say that I am very surprised at the improvement but enjoying my stereo more than ever before.

So... Mr. K... This begs the obvious question... Would moving to ALK Universal crossovers be yet another “order of magnitude” improvement? If so what is the current wait time for a pair of kits? I really can't afford them at the moment but I'll go on the Ramen noodle diet for a few weeks if I need to.

[Al Klappenberger]

Jhoak,

The buzz you hear is very typical of a driver getting energy below it's frequency range. The most common cause is the tweeter with a 1st order network. I found that a less extreme case of the same thing is when someone tries to upgrade the K55 in a Khorn with a new high quality 1-inch squawker driver. The new ones just can't handle the 400 Hz, even with an extreme-slope network. With the 1st or even 2nd order woofer filters most networks have energy far below 400 Hz gets through! That can show up as a buzz but will show distortion even before the buzz happens. Too much of that and the diaphragm hit the phase plug and it's all over but the crying!

The Universal networks have only one more element in the filter then the Jr. That's not a big difference. The law of diminishing returns gets you from here on. You need to go to an extreme-slope network to see the next big step. As to the waiting time, I have a backlog as usual, at least for now. The rotten state of the economy has me worried though.

Al K.

[Marvel]

The DHA wasn't my design...

I guess I wasn't really clear. The DHA, DHA2, DHA2 modified, are designed by John Albright. He loaned me the pair of crossover he got from you, while I decided what I wanted, Once I built a pair of his design, I returned his ALKs. They both sound great with my system at the volumes at which I listen (2A3 amps @ 3.5 watts). As I said, my build isn't as elegant, but they work fine. Yours are a work of art AND sound great.

Although I don't see him often, John lives about a 45 minute drive from me. It was nice that he loaned me your crossovers, as my LaScalas came to me with a pair of Klipsch type AL. The difference between those was like night and day. If someone has the money, I wouldn't hesitate to recommend your designs or completed crossovers.

Bruce

[Deang]

The DHA needs attenuation on the tweeter, hence the DHA2 - either straight up L-Pad, or resistor with autobulb for tweeter protection.

Old schematics for the alkjr (Super AA) show the zener diodes, however, I never used them in that build. In fact, I stopped using them years ago on the AA and my modified AA as well. The best tweeter protection sits between your ears. If you can't tell when a loudspeaker is being overdriven, find a different hobby. Now, I will say this, if you are going to insist on their use, it seems a bit bizarre to use them on the AA, but not the A - which unloads significantly more energy through that section of the filter.

I wish people would use my layouts when doing these builds. It reduces the complexity of the build and looks nicer too!

[Marvel]

I wish people would use my layouts when doing these builds.

I think you told me to go for it...here's the parts. []

I don't even remember the exact schematic I used. It changed a few times. I'm not using any tweeter protections, but then again, I'm using the eminence driver.

Bruce

[jhoak]

I wish people would use my layouts when doing these builds.

The departure from the "standard" layout was driven by several factors. (1) I didn't have the material on hand to make another pair of crossover boards. Being lazy and cheap I chose to not go buy more plywood. (2) The area where I prefer to mount the crossovers in my La Scalas is a bit restricted in terms of space. My La Scalas are (or were) slot ported in the back. I only have about 1/2" more sidewall to work with than the height of my existing crossover boards. (3) This was a purely "experimental" build. I had no idea going in what an improvement the crossovers would make. Now that I'm a "believer" I'll likely do a "proper" build with the correct parts and layout in the very near future.

By the way DeanG... What are the dimensions of the board used for the standard layout?

[Deang]

For some reason, the forum software isn't taking the carriage returns from my Droid. Oh well, here is a pic of one I built in 2005 -- http://community.klipsch.com/forums/storage/4/653336/MVC-026S.JPG

[Deang]

Bruce, I knew you were an anal retentive type and figured you'd do just fine. :-)

[Deang]

Jhoak, I don't remember the dimensions of the wood I used to build these on, but I pretty much build everything now on 12x8 Red Oak which I sand, oil, and rub out. The paint became nasty business and for the most part impossible to do during winter. You mentioned using "correct parts" when you rebuild -- truthfully, the parts you used are fine, and those Jantzen capacitors are especially nice. As for the air cores, I built my own with and without Litz, and couldn't hear any difference. There is a measurable difference - I just couldn't hear it! OTOH, I've often been accused of being deaf, especially by my wife.

[jhoak]

6" is my absolute maximum top to bottom without reworking the interiors of my La Scalas. The crossovers need to mount to the sidewall because of the cutout to the dog house that makes them ported.

The more I think about it the only installed part that I would consider "suspect" would be the 40mF Dayton capacitor. It is one of their "1% Precision" units but I've just read too many comments about improvements by going from Dayton's to something else. Of course getting 40uF of capacitance using some of the other caps can get a little spendy.

I don't know why but I kind of like the idea of having built the crossovers on plywood from the original La Scalas. At this point the only thing left from the originals is the bass bins and even they've had a rework.

All I know is that I'm really enjoying the sound coming out of my speakers. They played from 06:00 until 23:00 yesterday. Occasionally getting pretty loud. Yes my neighbors love me. []

[Guest David H]

The more I think about it the only installed part that I would consider "suspect" would be the 40mF Dayton capacitor. It is one of their "1% Precision" units but I've just read too many comments about improvements by going from Dayton's to something else.

You could also bypass the 40uF with a good bypass cap. Like a .1 to .47uF Auricap or Sonicap gen 2 film and foil. I have found the Daytons run on the low side for capacitance so adding a bypass will probably get you closer to spec anyway.

Dave

[jhoak]

HMMM... I have a few of the Auricap .22uF that I removed from a tube amp when I installed some PIOs. Would they just go parallel to the 40uF Daytons?

[Deang]

You would need a high quality film and foil for it to make any real difference -- something like a PPT Theta. I would go with the .47uF value that Dave recommended.

[jhoak]

What I NEED to do is nothing. At least not for a while.