Cobreflex or Khorn revisited

[dubai2000]

My holidays are about to finish, so there will again be less time for experimenting with my audio gear, but before going back to work Id like to share my latest Khorn experiences.

As a start Id like to thank Q-Man for his mid horn experiments and posting about them!

At the time quite a few people were experimenting with Altec horns (particularly the 511) in place of the stock K-400. I actually stored some pics on my computer because I was somehow intrigued by the looks of that horn. I should also add that at the time I was not only still relatively new to horns, but also more busy with changing from ss to tube amplification.plus I am no DIY person, so I thought changing horns/driver would be beyond my skills anyway.

Enter two weeks ago: I was trying to clean up my computer and ran across those pics. Hey, wasnt there a thread dealing with this mod? might be worth re-reading. Doing so more carefully than in the past, I noticed a horn being mentioned that did not need any adaptor to fix the stock K-55-V driver, no drilling, nothing: the Cobreflex, ex-University, now produced by Electro-Voice.

Mhhhhh, Parts Express was still offering those.perhaps they are even available in Germany? A few phone calls later I had ordered a pair of new Cobreflex II horns.I figured that with shipping costs added, new ones werent more costly than old models.

Enter earlier this week: the Cobreflex arrived and indeed, installing them was no problem screwing in the driver and that was it. Of course the new horn does NOT fit into the Khorns top section, but I am having the decorators model, so all Ill need is another cover for the bass bin and the Cobreflex and x-over will end up on top of that. Problem: what about the tweeter? Well, for the time being I have put it vertically in the opening between the horn flares.eventually it should end up in that space but on top of the horn as the opening in the Cobreflex front is not wide enough.

But now the most important question: how does it sound? Well, I had read Mike Lindsays thread

http://forums.klipsch.com/idealbb/view.asp?topicID=26066&forumID=71&catID=19&search=1&searchstring=&sessionID={92B00357-2075-44F9-BC6C-E2EB3EACB543}

closely, so I expected a difference, but I had no clear image of what to expect. The first CD I tried was an off-air recording of Mozarts Figaro.yes, it sounded differentmore directbut the strings also had a different tone.mhhhh?

Of course this was followed by a lot of familiar CDs.here was a recording of Mahlers Third.had I ever noticed the conductor moving on the rostrum or turning the leaves of the score? Ups, this IS a live recording.until now I am sure I had not noticed those slight audience noises in the background.

Horowitz recorded for TV in 1968. I am sure I had never heard his chair before!

The biggest surprises came last night: a few month ago I had bought a Karajan collection of works by Richard Strauss (DG 474 281-2) because I was interested in his final recording of Four Last Songs. Well, I was really disappointed because the sopranos voice sounded flat and rather sharp. With the Cobreflex I suddenly I understand why her voice is described as creamy in the accompanying booklet. Similarly improved sound (this time massed violins) on Karajans live Mahler Ninth (DG 439 024-2) and my only Living Presence CD (Scheherazade Minneapolis SO/Antal Dorati). Mind, its not that these recordings are suddenly state-of-the-art, but they are undoubtedly more listenable. I am wondering if certain harshness experienced before was not some kind of distortion produced by the K-400 (dampened)?

Summary: so far I think the change to the Cobreflex has brought a more open, more detailed sound. I actually felt after the change that the Khorns had been kind of pedestrian!!!a thought that had never entered my mind before! Saxophones sound more earthy, tube changes and changes in the tap setting of my ALKs seem to register more clearly. So all in all an interesting experiment which has all potential to remain my stock listening optionand other mods (i.e. Altec 311 are probably too complicated for me anyway) .

Wolfram

[pablum]

One important difference between the original "Cobreflex" and the new MK II version you acquired from Parts Express is the very fact the current version is ABS plastic while the original was not. This would seem to be an important distinction leading some to seek a used original. Some might say the ABS model would show less ringing if the original was metal but others might prefer the properties of the original.

Interesting comments. How does the latest CF version mount?

[TBrennan]

Dubai---It's normal to hear more detail when changing components because after doing so you tend to listen "deliberately" instead of naturally, know what I mean? Psychological thing. Of course the horn will change frequency response, a change in response on-axis could lead to certain details "popping out" because they are now elevated in response. One can do such things with an EQ too.

I'm not disputing your preference, just alerting you that perhaps you're giving the horn virtues it doesn't possess. And IME+O that horn has damned few virtues. I think Universal, always a rather low-rent company compared to the heavy-hitters at Altec and JBL, put it to work because it was available. Making a virtue of necessity.

[Q-Man]

I didn't read the old post again, but I do remember most of the results or should I say Mikes and mine opinions. We did A/B the 511-B, K-400, and the Cobreflex along with a couple other horns and drivers that are out of this league. The 511 did do some things better then the 400 and some things worse. The Corbreflex to my ears with music and warble test tones did just about everything better. The cobreflex may sound a little honky at times, but it is a far better choice to my ears.

The Cobreflex was around when Paul was doing his thing. My quess is that he may have not wanted to use it because it would make the building of the top section much more difficult. Maybe he wasn't allowed to use it eather, or maybe he didn't like it. Who knows? Who cares? The horn is worth trying for those who like to experiment. It is a cheap priced 250Hz horn, and you need a 250 to 300 Hz horn for the Klipschorn and LaScala.

[mungkiman]

The Cobreflex is an interesting animal. I have been told that it is not "supposed" to sound good, based upon design principles. I am also one of the ones that think it can sound great, with an appropriate driver (I'm not a big fan of the University T-30). The lens is somewhat clumsy for mounting purposes in my opinion.

That said, I'm a bigger fan of the Altec 511 horn with University SAHF driver, and the tweeter mounted in the mouth of the 511. Many would argue that something is lost above 250Hz, but it sure is sweet to MY ears.

[IB Slammin]

"back when Paul was doing his thing'.......

Q-man, Is everyone shure that PWK never used the CobraFlex? I wonder if the CobraFlex was around in the early 60's. Years ago, I saw a pair of Khorns with CobraFlex mids and the little University tweeter. Could have been a mod but they looked factory built. Maybe sold in kit form? I think Mr. Klipsch called them "bastard klipschorns".

Regards,

Terry

[TBrennan]

IB---The Cobraflex has been around a LONG time. Abe Cohen designed it, oh, ages ago, 1950s I'm thinking.

[dubai2000]

No denying, this danger of wanting to like a new component exists....after all one has spend money, but I was not 'waiting' for such new details, they didn't even all turn up on day one, some of them actually popped up just while listening to music and not to a new horn.

But I am sure there are even better upgrades than the Cobreflex and many people here have a lot more experiences with horns and drivers than I do, but still form me it has been a simple change and it seems to be worth the effort.

Wolfram

[Daddy Dee]

Thanks to the contributors for an interesting thread.

I've been wondering about the Altec horns since reading Al K's Belle transformation. Also, IBSlammin is using a pair with Cornwalls.

I went out to look at the cobreflex online and was surprised to see that they look so entirely utilitarian. Nothing romantic about their looks at all. Don't know if the looks of the 511 or 811 were ever an acquired taste or not. Just remember drooling over those big Altec studio monitors when I was a teen.

[Q-Man]

Look at a top view of the horn, and you will see that it is a folded horn. It's folded twice. If you unfolded it, it would be about 28" deep(front to back).

[IB Slammin]

----------------

On 4/18/2004 1:11:40 PM TBrennan wrote:

IB---The Cobraflex has been around a LONG time. Abe Cohen designed it, oh, ages ago, 1950s I'm thinking.

----------------

Tom, Now that you mention it.....I looked in Abraham Cohen's book Hi-FI Loudspeakers and Enclosures and there is a cut-away of the University bass bin with a CobraFlex inside. The copyright is 1956. Good ole Abe. That book was my Bible years ago. (old testament)

Terry

[TBrennan]

Wolfram---Well you might end up like I did with a basement full of horns, drivers and cabinets.

All I have now are some simple Heresys. And I'm enjoying them mightily.

[dubai2000]

Tom, I smell the danger but fortunately the cellar is already full - on the other hand there might just be space for a different tweeter option .

Wolfram

[soundog]

I replaced a 400 with a cobraflex in the center channel of one of my Heritage Home Theater setups. Both the 511 and the cobra work well with the K55 driver.

[Q-Man]

Wolfram,

Take a look under Updating Older Speakers, at John Warrens JBL 2404-H tweeter.

That is the tweeter to change to if you decide to go there.

I'm glad that you like the Cobreflex, I hate to say too much about some of the changes that I try for fear that someone will try them and not like the difference.

[dubai2000]

Q-Man,

thanks for pointing out the JBL...is it a direct replacement for the K-77, could it be run with ALKs and what about the Beyma CP25?

Wolfram

[Q-Man]

I would go for the JBLs.

I used the 2404-H tweeters with the ALK for a while and then with a Hot Rod AA network that John Warren built for me. I think they were fine with those networks. They sounded a lot better then the K-77. I'm now using the JBLs with the 290 & 311. The network is one that John designed for the 290-16K driver, 311-90 horn, and the JBL tweeters.

[edster00]

Q-Man,

How much cabinet work was required to install the new horns?

On another subject, do you know anyone in the Atlanta area that does refinishing/re-veneering (whichever is needed)? I am particularly interested in refinishing or re-veneering a pair of '74 (vertical horned) cornwalls.

[dubai2000]

Q-Man,

thanks for the info. Once funds permit (or luck...ebay ) that will be my next upgrade.

Wolfram

[Q-Man]

I might part with two of mine that I'm not using. Ask me if and when your ready.