Crossover Roadshow

[Budman]

welcome to the club tk, i'm completely blown away with my new ALK's in my k-horns and went ahead and ordered a set for my cornwalls.

its a dam shame these works of art Dean builds can't be seen when installed

[tk49]

Beauty and the Beast

[Deang]

"It's a dam shame these works of art Dean builds can't be seen when installed."

I appreciate those words Russ, I put a lot of time and effort into my builds. Someone once remarked that since they go behind or in the loudspeaker, what's the point in worrying about how they look? What's the inference here, attention to detail isn't important since no one is going to see them? Seen or not, the quality should be there.

"I'd love to see a Chorus or KLF crossover, I'd be all over that. I've read some pretty great things about the benefits of the ALK networks in the Forte and Cornwalls, just wish I could get something similar for either of those. Crites rebuilds them, but to me that's more of a cap refresh where the ALKs would be an upgrade."

Unlike Al, I actually like the stock crossovers, I have no problem with them whatsoever. However, I don't think it's necessary to replace all of the parts on the crossover when the only parts that really need help are the capacitors and resistors. If one is willing to forego replacing the coils and autotransformers, that means more money can be applied to the replacement of the parts that are the worst offenders. There are some very well made and great sounding capacitors available that don't cost much more than what most are using (for example, the ClarityCap ESA and Mundorf oil impregnated EVO series). A simple capacitor replacement job can produce a significant improvement in sound, and though it's not a "new design", it's every bit "an upgrade".

[Marvel]

I spent some time with Dean's Super AA crossovers. Review to follow...

Bruce

[Marvel]

Weird! The text wouldn't show up... [*-)]

[Marvel]

First off, I am making a comparison between three different
crossovers. In 2006, when I first got my '89 La Scalas, I found the original AL
crossovers to be terrible to my ears. Fortunately, John Albright loaned me a
pair of ALK Universals (I think) until I was able to build a pair of crossovers
he designed for his brother. These have had a few changes, but are pretty much
designated DHA2 crossovers. I have been living with these crossovers for a few
years now. The woofer, and mid driver on my LS are stock, while the tweeter has
been replaced with an Eminence APT-150. This is the same driver that Bob Crites
still uses, made by a Tonsil in Poland. I have it mounted on a baffle and
physically aligned with the K55 at the back of the cabinet.

These are powered by my Welborne Labs Moondog 2A3 amplifiers.
The preamp used is a JMA Merlin, a gift from forum members when my wife was
struggling with Stage 4 Melanoma. CDs only for the testing, the CDP being a late
'80s JVC model.

I traded my AL crossovers for a pair of battery biased AAs
done by Speakerfritz, and after checking to make sure the batteries were still
good, swapped them into the LS. The battery biased ones that Speakerfritz sent
to me aren't balanced. The mids are way too hot (Tom Brennan would agree!),
meaning I have to turn the gain way down, then the bass seems nonexistent. This
is probably due to them not being a constant impedance, and my 2A3 amps don't
like them.

I only left these in for an evening of listening, and then
put in Dean's Super AA crossovers. These have bypass caps installed. Wow! So
very smooth and a sound very, very similar to my DHA2 crossovers. As Dean
pointed out to me, the main thing I might hear is the difference between a 3rd
order (Super AA) and 1st order (DHA2) on the tweeter. For sure, at first I
thought something was wrong, as the tweeters didn't seem to have much signal
coming through them. Still, they sounded really, really good, the balance from
bottom to top works very well. Transients are great, and don't seem squished,
even with the Moondogs turned up. I haven't pulled out my DHA2s to check my tap
settings, but I know that I have the mids pulled down some, which makes the bass
seem a lot more full. The Supper AAs and DHA2s are constant impedance which
seems to really help my low power tube amps.

[After listening again to my DHA2 crossovers, the difference
between the 3rd order and 1st order for the tweeters really stands out. With
Dean's Super AA crossovers in place, you hear very little coming from the
APT-150 tweeters. With the DHA2s, a lot more sound is coming out. ]

On to the music.

I started with some Bela Fleck and the Flecktones/UFO TOFU,
Nora Jones/feels like home, Dave Weckl/Heads Up (cranked it up for the
drumming!), Atlanta Symphony Orchestra w/Sibelius' 3rd and 7th symphonies - nice
detail and sound stage. Pretty easy to pick out the placement of all the
sections. Yo-Yo Ma, Edgar Meyer, Mark O'Conner/ Appalachia Waltz, Hilary
Hahn/Mendelssohn & Shostakovich w/ Oslo Philharmonic Orchestra. One of my
favorites is a Mercury Living Prescence CD, a 1958 recording of Respighi/Ancient
Dances and Airs for Lute Suites 1, 2 & 3, with Antal Dorati. I actually
listen to this three or four times a week, so I know how it sounds on my system.

Other than the mids being a little hotter, the sound is as I
am used to hearing it. I would certainly give a thumbs up to Dean's Super AA
crossovers. They are a bit more complex than the DHA2s that I currently use
(certainly built better), perhaps the addition of the bypass caps is helping.
I can't fault them in any way. I am looking forward to my budeget allowing me to
purchase a set of these for a second set of LS that I have been working on.

Bruce

[The Dude]

Thanks for the write up, I am looking forward to trying something like this out. These will be my first to try anything other then Crites a/4500 crossover. I am looking forward to it.

[mikebse2a3]

The Supper AAs and DHA2s are constant impedance which seems to really help my low power tube amps.

Hey Marvel thanks for the review but would you please explain in more detail how you feel the constant impedance seems to help your low power amp?

miketn

[Marvel]

Mike, Thanks for the question... From what I have heard on here and understand, tube amp performance can greatly benefit with more stable load than most crossovers provide. Since the impedance can vary greatly, porviding a constant impedance (or nearly so) helps a lot. This isn't quite as big a problem with larger PP amps, but SET amps can use all the help they can get. This will also provide a more even freq. response.

I know that's not very technical, but most of what I understand. Perhaps Dean could add to this. I think most of Al K's networks are also constant impedance.

Bruce

[mikebse2a3]

From what I have heard on here and understand, tube amp performance can greatly benefit with more stable load than most crossovers provide. Since the impedance can vary greatly, porviding a constant impedance (or nearly so) helps a lot. This isn't quite as big a problem with larger PP amps, but SET amps can use all the help they can get. This will also provide a more even freq. response.

The idea that the constant impedance networks makes it an easier load for low power set amps or any amplifier versus the older Klipsch networks seems to be a common misconception on this forum. To bring the rising impedances of a network means you have to parallel a lower impedance element or elements to the network for compensation. This increases the current demand from the amplifier and without question makes it work harder. The only benefit is as you stated the less frequency variation due to impedance interacton between amplifier and network/loudspeaker. miketn

[Deang]

To bring the rising impedances of a network down means you have to parallel a lower impedance element or elements to the network for compensation.

That's true, and that's the purpose of the swamping resistor on the autotransformer.

This increases the current demand from the amplifier and without question makes it work harder.

I don't agree with this statement. An amplifier is a current source, it's job is to deliver current -- delivering more current doesn't mean it's "working harder", it just means it's doing more of what it was designed to do in the first place. An amplifier is working more, not harder, and I don't think "harder" comes into play unless you begin running the amplifier near the limits of its operating parameters.

The only benefit is as you stated the less frequency variation due to impedance interacton between amplifier and network/loudspeaker. miketn

I wouldn't trivialize this as the benefit is significant. I deal with owners of single-ended, zero feedback amplifiers quite a bit, and all report a subjective improvement in the sound.

So, how bad is the frequency variation? Give me a few minutes to find the plots.

[Vital]

Email sent...

[Deang]

Attached is page 3 from Richard Heyser's review of the Klipschorn - the plots show the complex impedance.

The following link is from Stereophile's review of the Cary CAD-300SEI (single-ended integrated).

http://www.stereophile.com/content/cary-audio-design-cad-300sei-integrated-amplifier-measurements

Based on the information from these two sources, what does one think the frequency response of a Heritage speaker might look like driven by one of these type amplifilers (single-ended, zero feedback)?

Review page 3 of 6.pdf

[seti]

I measured a friends Khorns with George Wright SET 2A3 amps.

The curves were almost identical to Khorns with higher powered McIntosh amps. There was a bigger difference switching between 4ohm and 8ohm taps.

[kaiser SET say]

Dean, the Aletheia site looks very clean and professional like your work. I would like to try your Super AA's in place of my Crites A/AA's, my biggest fears are I'm going to have to have them once I hear them! Is the offer still open and what if so is your list looking like? My other dilemma is (and I know you prefer oil caps) is do I need (want probably) to upgrade to the oil caps versions[:|] THX

[Deang]

I measured a friends Khorns with George Wright SET 2A3 amps.

The curves were almost identical to Khorns with higher powered McIntosh amps. There was a bigger difference switching between 4ohm and 8ohm taps.

I believe that design employs moderate feedback. He also utilized/designed an output stage that pulled 4 watts out of the 2a3.

[Deang]

This thing will run until no one wants to hear them. The list always seems to stay around four or five. Right now, I only know who has them, I don't know who's next or how many are after that because that info is on my home computer and I'm at work right now.

I like the PIOs in the old filters, it sounds real nice. When the part count and values increase like they do in the Super AA -- it really does become cost prohibitive for most. So, you have to do something different or you don't move anything. I do offer a version of the Super AA built using Mundorf EVO oil filled polypropylenes and I can bring them in at price that's not in the realm of the absurd. I just got done building a pair of using VH Audio OIMP V-caps for Muel -- I would consider that approaching "the realm of the aburd", but he's going to be very happy.

[anarchist]

Dean,

I have reviewed your thread and your webpage etc. A 30 second conversation with you would guarantee that you would tell me I absolutely need to replace the cross-overs in my Khorns (also need to replace something in my KSP's as they went up in smoke and my sub no longer works, but I digress.) My problem is this... these are such works of art, I would put them in glass on top of my KHorns and my existing cross-overs would continue to need replaced. I haven't figured out how to justify buying 2 sets of cross-overs just yet.

[kaiser SET say]

Those are sweet Dean, I'm sure Muel is going to be one happy camper. I don't belive that stuff about these babies not getting seen, I leave the back doors off my Industrials on purpose just so folks can peer inside and see the 400 horn and x-overs[]

If I read your site right the entry Super AA's are $350.00 and the EVO models were +$225? Might could justify that upgrade if I let the A/AA's go, of course I don't think they will bring quite that much (could take some sexy pictuures of them and their cedar planks for the eSlay crowd)[] Sign me up and I'm thinking black boards since my Las are jet black. I second Robert's post that they deserve art under glass treatment the ALK Uni's are beautiful as well as the Klipsch A/B & E's[Y]

I'm thinking I could pm Muel for that absurd pricing but I would be happy just seeing those when finished[8-)]

Are you getting shipping info through pm's? THX

[muel]

... approaching "the realm of the absurd"

hmm... I like that. Perhaps that should be my new slogan? I'm sure my kids would agree.