Hello, newbie here with 902-8B drivers on the way...

[chopsrr]

Honestly, I don't think I will want to remove the loading caps. I play my system rather loud and have the 902s crossed over at 375Hz with a 1st order filter. I don't want to run the chance of damaging them and/or blowing them.



I boosted up the contrast to help show the inside of the driver. I'm assuming that "star" shaped thing is the phase plug. Is this or is it not the tangerine phase plug, or was that only on the 800 series drivers?

And here's a full bandwidth Pink Noise plot that I just took today of the Klipsch K33/Altec 902 combo...

[boltupright]

The orange "star" shaped thing is the Tangerine phaze plug & is designed to give more extended highs, the 902's sould satisfy in the high fequencies, I can't figure out why they wouldn't sound good to you unless they are not the proper diaphragms inside or they are just not working properly, mind you if your ears are tuned to the super high frequencies of the JBL 007 super tweeter, maybe it's just that you've grown so accustomed to the sound of them, that nothing compares to them.
There is definately a difference when you run such a tweeter no doubt.

[chopsrr]

BTW, I thought you guys might enjoy a few pics of my speakers. I guess they are now considered (as some of the guys on the Klipsch forum refer to them as) Alcorns. "Al" being for Altec and "corn" for the Cornwalls. I'm sure you all probably already knew that though.

Anyway, on with the pics... Enjoy!

[chopsrr]

Well guys, I'm having an issue with these 902s rolling off quite a bit sooner than I expected.

Is there any way of squeezing a few extra kHz out of these things, or am I stuck having to go back to a 3-way setup?

I've read a few things about removing the bug screens, but I highly doubt the screens are attenuating the treble this much. And I am ON axis with the horns when seated.

And replacing the loading caps with felt only helps the midrange if I'm not mistaken.

Many thanks in advance!
Charles

[GM]

Greets!

Based on your FR plot, your drivers measure better than the factory's official plot or my own measurements from long ago! Anyway, 511s are CD horns, ergo require CD EQ (R/C network) to tonally balance them, IOW flatten their response so that the driver's highs are at ~the same amplitude as the horn's output. Remember, the horn's HF-6 is around 6900 Hz, so the rest of its HF BW is direct radiating, with some reflection losses to improve its polar response rolling it off even quicker than if there was no horn attached.

Obviously, the horn's effective efficiency wil be lower, so less attenuation will be required to balance it to the Cornwalls and the CC will have to work harder to keep up with them once it is level matched, so a super tweeter will be required if this trading eff. for ~flat BW isn't acceptable.

WRT removing the bug screens, back when I still had HF hearing, doing it to 802, 806 drivers added a bit of top 'air' around the instruments, making the sonic experience a bit more life-like on good recordings, ergo it made vinyl noise more irritating and some CDs to 'bright'/harsh, but today, it would be wasted effort.

WRT your XO point/slope, if you're going to continue to use the loading caps, then ideally it needs to be re-done to get rid of the broadband hole it causes in the BW that has the greatest dynamic range, unless of course you're intentionally using it as a compressor. Still, a ~flat in-room FR in this BW with a shallow broadband dip through our acute hearing BW apparently sounds the m0st natural for music, while DD/DTS mixing reference is flat from 20-20 kHz for HT for all but the LFE channel.

GM

[GM]

Greets!

I'm not familiar with the K33's HF response, but the 902 w/loading cap and 1st order XO likes a ~2 kHz XO point and regardless of XO point/slope, either an impedance matching amp or an R/C network is required for flattest, most extended response.

'CC' refers to your HT's center channel.

Anyway, you're heading in the right direction............

GM

[chopsrr]

A 2kHz crossover point?! What on earth for?

I'm not using the 902 as a tweeter. At my listening seat, about 13-14' in front of the speakers, in my 13x17 room with 8' ceiling, I'm only reaching peaks of maybe 105dB at best, and a sustained output between 98-101dB.

I have already played the 902s this loud at the lower 375Hz crossover point without a hitch, and now at 600Hz, I'm sure to never run into a problem.

There's a guy in the Klipsch forum with the basic same speaker setup as me, except he has his 902s crossed at 400Hz, and he runs a constant 110-115dB in his room, also without problems. He's had this configuration for the past 2 years.

If these 902 drivers are rated at 106dB loaded into a 511B horn at 1 watt input, then I'm probably only putting about 3 watts max into my 902s. That's well below the rated 15 watt max that Altec claims.

I honestly think I have nothing to worry about using these at 600Hz with a 1st order network in my room.

[Jim Easley]

GM,
How is the 511 horn considered a "CD" type.
I am assuming "CD" is meant as "constant directivity".

[GM]

Greets!

Charles,

Please re-read what I posted, nowhere did I state, allude to, or insinuate that it takes a high XO point to protect it in a HI-FI app. You can run them without loading caps at least as low as 400 Hz/1st order on a 511 without hitting the phase plug in a HI-FI app, but it sounds like $#@! to me and many others. As always though, YMMV.

I was referring to sound quality (SQ) due to the underdamped peaking the loading cap causes, hence the 'like' reference, but I guess 'my bad' for being too cryptic for a horn 'newbie'.

Anyway, don't knock it till you've tried it along with the EQ, preferably with a higher SQ woofer than the 'workhorse' K33.

Jim,

Correct. The 511's expansion begins as conical in the driver for its highest BW, using the horn mouth's vertical slats to disperse them somewhat, then morphs to a modest vertically slot loaded section to pattern control (horizontally 'fan') its mids/lower HF response, with its terminus driving the exponential radial flare for the lower octaves. An excellent performing CD horn overall, trading ultimate pattern control for extended HF BW compared to many later CD designs, but much better off axis response than a proper horn such as the WE15, etc., though not as good as a multi-cell, which is the 'grandaddy' of CD flares.

GM

[Russellc]

Remove the loading caps, they will not only extend more, but there will be more air as well. In short, they will sound better. while apart, note the diaphram number and make sure you dont have the symbiotic diaprhams, which dont sound bad, but not as good as the regular aluminum ones. A kit of six short screws and two felts can be had for around 10 bucks from great plaines. Dont worry about damaging the diaphrams for home use, your ear drums will blow out long before they (diaphrams) will for home use. It is easy to switch back, but I can assure you that you will have no desire to. If you loose them, I have a whole box full of them. I also removed the screens, and kind of wish I didnt, for protection from small objects, etc. It did seem to help a little, but not nearly as much as the removal of the loading caps. Plenty of altec drivers dont use them, and it is no trouble, unless you are using them in a PA application at wide open volumes in large auditoriums. For home use, it is a non issue. I have never cooked one ever at home,
and have been using them off and on since the 70s.

Russellc