Installing Mike's Altec 511B horns

[Q-Man]

This has developed into quite a topic. I don't want anyone running out to buy the cobreflex horn. By the way, it is spelled with two (e's).

There is more comparing to be done, and Mike and I wern't using test equipment. Were just using our ears, SPL meter, and a limited test CD. The CD has frequency test tones we started at 315Hz,400,500,?,?,?,?,?,?,?,?,4000,5000,6300,?,

8600Hz. Mike will have to fill in the blanks. I don't remember them. But, there seems to be some wide gaps between them.

I can't argue with any of the comments on this post. At least not yet. I do appreciate all your opinions and help.

I'm a little worried about what I heard, because louder always sounds better to me. As I said earlier,I'll mess with the network tap settings and the volume control if I have to. I'll balance them and listen again. I just got back from buying some 10 ohm resistors to put across the tweeter post on AL's network and I'm going to set things up tonight.

djk might be right about the 4000Hz crossover point for the horn. I think that's about where the University Classic network changes to the 206 tweeter. The bottom end crosses over at 300 to 350 Hz.

We didn't run any test tones with the Cobreflex, only with the 511B, and the K-400. But, I do remember quite clearly that my Stock University Classic speaker sounds mush better then the LaScala from top to bottom. I'll try to see how this mid. horn sounds with the K-55 and the klipsch and ALK network. I'll add more after I do so.

A few weeks ago my sister brought a friend of hers over to listen to some music. She saw the University Classic bass horn with the Cobreflex horn resting on top of it sitting behind a sofa. Her comment was, " Are you stooping so low now that your stealing bull-horns off of the sides of buildings?"

[edwardre]

Q - Too late!!!! My set is in the mail!! But not to worry, I am nothing but pleased to be able to check it out for myself. FWIW, the 'ear' test is truly the only test I value (except for gross non-conformities). It's one of the reasons I purchased the CobrEflEx's.....based upon several 'unscientific testimonials' which, BTW, are the only type of endorsement anyone ever gets from me!

[djk]

People mis-spell 'cobreflex' so much that EV and Yahoo both list it as 'cobraflex' in their search engines!

Ev Products - Speakers - ... HPT94; MH4020AC; MH6040AC; MH640c; MH640p; MH660c; MH660p; MH940c; MH940p; S-40 Series; S-40T Series; CDP-848AT; CDP-850T; CFID32-T; Cobraflex IIB; Cobraflex III; ... EV Speakers. ...

http://www.electrovoice.com/Electrovoice/products.nsf/allpages/066D59279DD6D93886256B96005D4

Refine Your Search

EV COBRAFLEX

Electro-Voice EV COBRAFLEX III SECTORAL HORN - ... The Cobreflex Series of folded sectoral horns features a patented design that eliminates high frequency phase cancellation and improves intelligibility. ...

http://shop.store.yahoo.com/aicons/evcobiiisech.html

"differences between the original Cobraflex and the II's, III's....Visually, they all look the same to me."

The II is aluminum with a .7" throat, the IIB is ABS with a .7" throat, the III is fiberglass with a 1" throat. The III is also quite a bit larger than the others because of the constant directivity mouth design.

It should be mentioned in passing that using a .7" throat paging horn driver (SAHF, K55V, etc) with a 1" entry horn (the III is 1", as well as the 511B and many others), will lead to slightly increased distortion below 800hz. Atlas and RCF both make adaptors that will match properly. MCM used to carry what they called a 'voice adaptor' that had a 1-3/8"X18 .7" entry and a 1-3/8"X18 1" exit, but it is long disconinued. Because of this I would recommend buying a 1" driver (1823, 1824, 1828, etc) for use with the IIIs.

School gyms that are being refurbished are a good source of cheap (or sometimes a six-pack) paging stuff.

[John Warren]

I listened to the Cflex horns for 5 years when I owned a pair of Classics. At that time I was using a pair of Dyna Mk III amps, pre-amp was a Mc C15, source material was an AR turntable with Grado cartridge. Tubes were Mullards, Genelex and Telefunken. The network was stock. My listening experience with this speaker is mixed and is over the 1979-1984 timeframe. The horn, like the Klipsch mid,

was challenged with complex orchestral passages at moderate volumes and horn rasp (compression overload) was in and out. Piano, strings, voices were off and like Klipschorns, at live music levels I found then hard to listen to for more than 30min without having to pop a couple of Tylenols. The Cflex is a PA horn. Sitting here and critically assessing its ability to reproduce complex musical passages must have Abe Cohen rolling over (laughing) in his grave. Note that the Classic has a respectable bass horn.

Why settle for horn loaded mids when 101-103dB/W/m direct radiators arrays can be used? An array pair of JBL 2012s or 2123s on each side with dedicated amp becomes a whole different experience.

[Q-Man]

My ears were ringing after 2 hours at Mikes 104 to 110 db SPL . I was trying to duplicate what I was hearing at Mikes house. Mike, My son says your nuts, or that us old men can't hear very well. He put in ear plugs to do some of the AB switching for me.

I set up a 400 and Cobre on top of my spare Klipschorns in the back room. I was shocked and still confused, because the Cobre isn't louder then the 400 in this room. They are about equal. I thought that something might be wrong with the drivers that I was using so I took out anothe spare pair and hooked them up. No difference. I switched the networks from left to right,switched amps on the receiver. No difference. Switched Al's tap settings just to see if they worked. They do, they change the volume of the driver.I put them both back to the same setting. I said that I had these horns on top of my Klipschorns, so that means that they are both in the corners of the room. In Mikes room his left LaScala is in a corner.His Right LaScala is more in free space open to another room. Could this be making the volume difference? Tonight I'll flip flop the horns from one corner to the other and try a few more things.

After wasting a good bit of time trying to figure out why the volume from both horns was equal I began to listen to them. One note here, since I find the volume the same for these horns you can use the with the Klipsch stock networks.

You won't need AL's just so you can adjust the volume level.

Sound wise the Cobre still sounds nicer to my ears. The 400

is more nasal, and honky. The Cobre is more open and much better with voices, male and female. It also has cleaner and or louder highs. Now I wanted my 14 year old son to listen and give me his opinion while I did the AB switching. This means that I had to listen to rap type music, because he wanted to listen to material that he was familiar with. I couldn't argue that point. We also turned down tha volume to 90db for him. He hears things instantly all the time and is always asking me "don't you hear that".

I guess it's my older ears. Anyway, his words were. "I can hear the notes better, I can hear things that I can't out of the Klipsch."

Mike, I should have made you come over. I'm going to leave this set up for a couple of weeks and do ome more playing around. I found out that my remote control has an AB switch on it, so I can sit back and do the switching myself any time I feel like it.

My older son is coming home from college today, so I'll sit him down and get his opinion.

I now realize that I like Mike's Scott tube amp. Something sounded better at his house using his two channel rig. It made the spread difference between the horns even wider. I'm using my retired Yamaha RX-V2092 Theater receiver fot this. Now I'm wondering what it will sound like in the theater room using the McIntosh amps.

At low volume I notice less of a difference between the horns. The louder you go the better the Cobre sounds and the worse the 400 sounds. At extream volume my son says the cobre keep on ticking and the 400 distorts.

I'll keep playing with this combo for a while and let you know what's up.

[Mike Lindsey]

Q,

I never looked at the SPL meter when we were listening, but with the volume at 6 - 6.5 on the Scott, it's generally around 100 - 105db at the listening position. I never felt it was too loud where I had to cover my ears. I generally listen with it at 12:00 (set to 5) and depending on the source, that would be right around 90 - 97db. One other thing to consider is there is a wall directly behind my listening position where we were doing the readings from. In your house, there is nothing for the sound to reflect off of so I'll bet you have to have it a lot louder to get the same readings. Of course, I could be wrong here.

As for you not getting a volume difference in your room that is very strange. Your room is much bigger than mine (mine is 15' x 15' x 17' w/10' ceilings and with one wall open to the kitchen). I'm now wondering if there is a difference with one La Scala being in the corner and the other one being more out in the open.

Maybe I can get over there sometime this week or next weekend, and I will bring my Scott with me. I will let you know...

Mike

[Q-Man]

Mike,

I said I have these horns set up in the smaller room. The room off of the theater room. Remember the room with the single pair of klipschorns in it. The size is 16'x20' with four walls.

This way I can leave stuff set up and take my time fooling around with it.

If you decide to come, the horns will probably still be set up. I have to put the 288/805B in there too,because I want to decide how I am going to use it.

[Mike Lindsey]

I didn't catch that about the room, Q. I'll see if Debbie wants to visit her sister this weekend (they live in Cocoa) and I'll just mosey on over to your house...

Mike

[John Warren]

Al-

To see what the inside of a Cobreflex looks go to www.uspto.gov and view patent # 2746558. Note that the

horn was invented by Sid Levy, inventor the compact radial horn projector.

For the record, the University Classic Cobreflex came with the T-30 compression driver not the SA-HF. The T-30 was the recommended compression driver for *hifi* applications and was paired with either the Cobreflex or the H600 horn flare.

[Mike Lindsey]

Q-Man uses the T-30 driver when hooked up to his University Classic. We listened to both drivers when demoing the Cobreflex on the La Scala's and I actually preferred the sound coming from the K55. Even though the T-30 put out more output, it seemed to be a little more harsh and nasal to me. I'm not sure which one Q-Man preferred...

Mike

[Q-Man]

John, Thanks for getting in here.

I'm getting closer.

The K-400 is about 1 1/5 db lounder then the Cobreflex. It's hard to measure without test tones. I'm going to order the Stereophile test CD's and listen more.

I sent my older son (Nick) into the room to play around without telling him any of my younger son

(Jason) and my opinions. Al's network on the 400

is now adjusted to lower the volume to match the Cobreflex. Nick knows the procedure, so I didn't even go into the room with him. After about a half an hour Nick came out and said. " Voices are more natural and real sounding on the Cobreflex." "The high frequencies are cleaner and or louder, cymbals are heard more. " "I'm not sure

if they are exagerated or this is how they should sound, because you hear so much more in the Cobreflex." Then he asked me if the high frequency difference were right or wrong. I told him that the more Jason and I listen we feel that the Cobre is right for us, and that we like the high frequencies better. But, Jason has always complained about the Klipschorn and LaScala top end not being right, so I expected him to like this. He is always telling me that he hears high frequencies out of his speakers that he can't hear out of mine. I have always told him that mine were right. I think I was proven wrong.

Both sons also pointed out that drum sticks hitting the metal rings around the drums sound crisper and real. The three of us prefer the Cobreflex, but Jason says it's not worth building new Klipschorn tops for this horn. He eather hasn't earned his tweaker badge yet or wants more. He is anxious to hook up the Altec 288 and 805b. He said that maybe that horn will be worth the change.

I just hooked up the University T-30 driver to the Cobreflex and I'll add some about this combo later.

John, you may be right about complex material from the cobreflex something about this horn isn't quite right to me, but I'll take it over the 400.

I'm not going to rush this. I want to find out what is best for me.

[Q-Man]

A quick first impression of the T-30 and the Cobreflex combo. Al's networks are now set the same. Remember that the K-55/Cobre SPL was 1.5db below the K-55/400. Now the T-30/Cobre is a lot louder then the 55/400. High frequencies extend even higher, and more detailed yet. Jason now really likes this part. I think it's too bright. Female Voices sound better then in the 400, male voices sound worse. Male voices now sound better from the 400 where before they were much better with the 55/Cobre. Male voices now sound tinny or too thin.

I'll adjust Al's networks to balance the volume and report back. Remember these comments are from only 15 minutes of listening. We did hear some triangles that we can't hear at all from the 55/400.

Jason says that after we get used to this to put a T-30 on the 400 and just compare the horns again.

[John Warren]

Gary- From my own listening experiences with the Classics I heard evidence of significant strain when presented full scall symphonic material (for example, the last movement of Rimsky-Korsokov's *Scheherazade*). They're small format horns and (of course) I'm expecting too much. Also, I never played with the networks, mine were the stock so using premium quality hardware will certainly change the character of the horn. I just don't have any experience here with these mods. I DO recall how rigid the Cobreflex horn was, the folding stiffens the structure reducing the tendency of the horn to ring.

I think your experiments are great! You and your sons are really getting to know how these horns sound. Try listening to the compression drivers "near feild" at extremely low volume without the horns attached, put them near your ears like headphones and compare how they sound to each other. Interesting test, even supposedly *identical* drivers can sound different.

[Q-Man]

I prefer the Cobreflex with the K55 over the 400

and the 55 driver, better highs & voices. It's about 1.5db softer then the 400. If you decide to use the Cobreflex the ALK network will adjust the volume of the midrange driver to match the volume of the 400. I havn't tried it with some of the stock networks yet, but I'm going to.

I've now been comparing the Cobreflex and the University T-30 driver to the Cobre with the K-55 driver. As I said the T-30 adds more highs, cleaner, more detail, about 6db louder,but I don't like the vocals as much as the Cobre/55. Jason prefers the T-30.

I then hooked up two Cobreflex horns with T-30 drivers. One with the AlK network and one with the University N3 network.

I prefer it with the ALK network, the sound isn't quite as harsh. But, they are close. The N3 network crosses over at 350 and 5000Hz.

Next I set up the K55 & Cobreflex ( the combo that I like),

and the Altec 288-16K driver with the 805b horn. Here we go again, more and better highs, more seperation, & detail, but

the vocals sound like they did with the T-30, clean and clear, but a little thin. Not as husky sounding as the K-55.

I'm begining to think that I'm too used to the sound of the 400 & 55. Maybe voices should sound the way the T-30 & the Altec reproduce them. Last night I found myself wishing that I could sit a few of these vocalist down in my room and ask them to sing to me. I would like to know what they really sound like. I can say that I prefer the detail & clarity from the Altec & T-30, I'm just so confused over the voices. If these drivers are closer to the real thing with most everything elce then maybe they are doing the voices right. If this is true and I end up using them, I will have to get use to the sound of all my music.

Next I need to compare the T-30/Cobreflex to the Altec/805B, because I remember the T-30 sounding a lot like the Altec.

I also remember the demo between the University Classic and the LaScala. Any fool would pick the University Classic. So maybe the T-30 is a more accurate reproducer. I'm still only listening the midrange alone, no woofer or tweeter. Once I listen to the complete speaker it might be a no brainer as to what sounds right. Maybe I'm trying to hard to pick out the differences between these horns and drivers.

I ordered the frequency test CD's. This isn't as easy as I thought that it would be.

I would like to hear what T Brennan has to say about the 288 that he bought.

[edwardre]

Recieved my Cobre's last night. Turns out one is a "1", the other a "2". I can identify no differences. Interesting that the Cobreflex is a 'two-piece' horn. Top and bottom bolted together via 9 bolts. Gasket material makes the seal. So Al.....if you're still interested, I'm thinking of ripping one open just to check out the folded internals. I'll be happy to snap a pic or two. Additionally, the horn itself is fairly rigid and robust in construction. Much more so than I had expected. Don't know why but pictures make it look kind of thin and cheap. The 'extras' received were a driver (T-50) and an adapter to mount two drivers into one horn.

Naturally, I spun in a driver and fired it up immediately. A SAHF driver. Same color scheme and basic look, looks like they were made for each other. Opposing channel sported the SAHF/K400 combo for basic R/L comparisons. Network was the venerable Klipsch AA, which BTW moments before I had located and removed the steel inductor screws from. ST70 amp/PAS2 preamp/late 70's vintage Sansui CD player. Media was an Eagles greatest hits CD. The difference in the two setups was more pronounced than I was mentally envisioning. As Q states, against the K400 horn, the C-flex is comparativly subtle to the tune of perhaps a db or 2. The greatest difference was tonally. I never realized just how 'ringey' the K400 is until last night. In this setup, the c-flex is flat out in another league. I am only sorry that you folks cannot come over and hear for yourselves. I find it very ironic indeed that the horn that 'looks' like a PA speaker sounds so suited for home listening while the 'home speaker' horn's output sounds well.....suited for outdoor use.

Obviously this is a very preliminary report based upon 20 minutes of listening. I want to compare against the 511B, with K55's, different nets, yadda yadda yadda....We're hosting a going away 'git together' for friends moving to Minn. tomorrow. Mostly the guys hang out in the garage and BS. The only tunes in the garage is the test bench. Will be a great opportunity to get many opinions from folks that are um....'not into the audio scene as much (if at all)', as well as enlighten any 'Bose-O's' in the crowd.

[Jim Cornell]

Hey guys,

Im ganna barrow a set of Altec 511b horns, to see hoew they sound with my Klipschorns, if there isnt a drastic difference then maybe ill leave the K-400s alone, so far reading this, my room is only 15X10, and if the Altecs are louder thats what i dont want!

Some one please give me the exact measurement from the face of the altec 511b horn, so i can see how much bigger it is!

Will it fit in the K-400 slot, id hate to cut and modify the horn and not like it!

Maybe ill barrow the horns sometime in the next week, untill then im blind on how big they are!

Regards Jim

[jnorv]

Outside flange dimensions are 23 1/4 x 10 1/2. Looks like they would fit into a 21 1/4 x 9 1/4 hole. Depth is 14 inch between the front flange and the horn throat.

Jim N

[edwardre]

Jim, they will most certainly not fit in the slot. In fact, you would have to replace the 'slotboard', either just across the front or including the grill covered wings with a open framework-type grill frame. That is providing you want to preserve the original appearence.

Of course, some take the top section off completely and set it atop the bin. I believe it will fit comfortably within the top section if you cutoff the 511b's upper and lower flange. Then you could remove the grillboard assembly altogether and take your time working out the grill issue.

On the other hand, it's quite a striking item on it's own. It completely dwarfs the K400.

[Q-Man]

After a couple of days of comparing the T30/Cobre with the Altec 288-16K and 805B I now prefer the Altec combo.

The 288/805 has all the highs of the T30/Cobre, but is more mellow and not as shrill sounding. The T30/Cobre now sounds raspy and harsh, and some of the highs and voices pierce through your head like a lighting bolt. The Altec keeps it's composure with everything it reproduces.The Altec is silky smooth and doesn't give up any detail to the T30/Cobre. The Altec is even cleaner with more separation. Jason says after listening to the Altec, that the T30/Cobre sounds like it eckoes.

I want to listen to the frequency test tones between 350 and 600Hz., because the 288-16K is a 500Hz driver and the 805B is also a 500Hz horn like the 511B. I don't think that I'm missing anything with it being crossed over to at 400Hz. If the test tones confirm this, then the 288/805 will replace the K-400 & K55 in my Klipschorns. Then I'll have to get used to the way some of the vocals sound.

This may mean that I'll end up having to build a new center channel speaker. Maybe I can get away with using the Cobreflex in the rear. Will see, I'm rather anal about all my speakers being the same.

[djk]

Q:

If you would like a single 805B and 288K-16 let me know. The driver would have a new diaphragm.