A7 Lost Cymbals

I fired up my new A7's for a test run today, and the cymbals are distinctly missing in an A/B comparison with my other set of speakers, which are nothing special.

Here's what I've got:

808-8A drivers
809-8A crossovers
511 B horns
515-8LF GPA

I assume that the problem is either with the crossovers or the 808s. Does loss - or absence in the first place - of the very top end typically indicate failure in one rather than the other? Do I have the right drivers in the first place? (3,500 sf cabinet shop, all open, no walls, rock and roll) I'd planned to do some crossovers as per Panomaniac in the future, is it time? I'd kind of like to get them up and running for a bit before I start buying more stuff.

I sure would appreciate some help.

Thanks,

Ed

I doubt there's really a "problem".

If the 808-8A's are stock, they have symbiotik diaphragms which have a very rolled off HF response.

Recap the XO's, and if you can swing it, send the drivers to GPA for a re-charge and new 34647 diaphragms, this will restore the sizzle you're missing. Deleting the L-pad and replacing it with fixed resistors of the value that gives the HF level you need can also be an improvement

Yes, and no, the now 802s will still be a bit soft up high on a 511, so assuming one's HF hearing isn't as shot as mine, then experimenting with by-pass caps wired around the XO's attenuator or fixed resistor replacement is desirable with 0.1-1.0 uF being the usual range for most folks, though in a large/loud shop environment up to 2.0 uF or more may be required.

Of course this assumes GPA can bring the drivers back up to spec if they're off much.

On the short term, you can try some larger caps with the existing Symbiotik diaphragms in the 2-5.0 uF range (I'm guessing) to see if that's acceptable. I've never tried it since these tend to shriek like ripping aluminum up high when EQ'd in a PA app, but for a shop app there might be an acceptable 'sweet spot' between adequate HF extension and too shrill a performance.

GM

How do the 'mids' compare between Symbiotics and the other Altec options when used in 808s?

Marshall.

Replace the symbiotic frams.

Ditto - replace!

Even better, remove the symbiotic phragms, sell them on E-Pray, and then send your 808 carcasses off to Bill H at GPA....:2thumbsup:

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Originally Posted by analog addict

Even better, remove the symbiotic phragms, sell them on E-Pray, and then send your 808 carcasses off to Bill H at GPA....:2thumbsup:

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Exactly what I am doing right now, the 808s are at GPa as we speak morphing into 802s, and the symbiotiks are on fleapay.

Thanks all for your good - and consistent - advice. The UPS man just left with the drivers.

Here's what I learned. I took both drivers apart. There were 2 different kinds of diaphragms. The driver with the older style diaphragm had a bit of corrosion on the outside. Oddly enough, on the outside of the driver, someone had written lightly in pencil "bad." There's a clue!

I spoke to Bill this morning; he had some interesting thoughts. He offered to remagnitize and check them out for a nominal fee. He also felt that rather than buying new diaphragms, (I didn't know about the miss-matched diaphragms when we spoke) my money might be better spent buying ribbon tweeters to supplement the 808s. He offered to help me figure out how to cross them over. Great guy.

Here's what I found:

Zaph|Audio

They liked the Bohlender Graebener Neo3 PDR, for about $45 each.

* Power Handling: 20 watts RMS/50 watts max
* Impedance: 4 ohms
* Frequency range: 2,000-28,000 Hz
* SPL: 90.5 dB 2.83V/1m

The price is in the budget, but are they suitable?

Thanks,

Ed

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Originally Posted by mah

How do the 'mids' compare between Symbiotics and the other Altec options when used in 808s?

Marshall.

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For compression horn mids, phenolic is best since it's both rigid and reasonably well damped, then hybrids such as Symbiotik, trading a bit more HF extension for less rigidity/damping, with neither being any good for the > ~5-8 kHz BW depending on the horn loading and personal preference, so a super tweeter system is a must if for other than strictly public address apps. In the case of the 808 then, it sounds a bit 'fuller' than the lighter, more flexible HIFI diaphragms when BW limited.

GM

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Originally Posted by edharbur

........my money might be better spent buying ribbon tweeters to supplement the 808s.

* SPL: 90.5 dB 2.83V/1m

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Yes, ribbons are popular for adding top end 'air' to horns since they're both highly damped, but I imagine your A7s will still be considerably more efficient once EQ'd in-room, so I imagine you'll wind up eating up all this ribbon's nominal power handling/low distortion output in boost EQ to keep pace if you don't use multiples.

GM

Yes get rid of the symbiotiks it gets much,much better.

Quote:

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Originally Posted by GM

...In the case of the 808 then, it sounds a bit 'fuller' than the lighter, more flexible HIFI diaphragms when BW limited.
GM

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Was my experience with 808-8A's (symbiotik) in a three way.

The planars mentioned are characterized as good dispersion (though I saw no specs), but if higher efficiency is necessary, you might consider these other (inexpensive) options:

http://profesional.beyma.com/pdf/CP09E.pdf
(spec'd at: 90?x60? dispersion, Aluminum)

PE had them on sale at one point, real cheap.
Looks like perhaps they cut ties with Beyma though (?), perhaps is why they had a sale.

...or selenium slots:
http://www.parts-express.com/pdf/264-360.pdf
(spec'd at: 120?x40? dispersion, Phenolic)


If anywhere near PHL, you're welcome to borrow mine to try out.

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...or selenium slots:
http://www.parts-express.com/pdf/264-360.pdf
(spec'd at: 120?x40? dispersion, Phenolic)

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I have a couple pair of the older aluminum bodied versions, ST-320, i really like them. In fact, here's all 4 in the "project" room.



http://i107.photobucket.com/albums/m...s/DIYboxes.jpg

Thanks again for the good answers and quick responses. It does me good that a consensus on the ST-320s seems to be developing here - it makes decisions much easier for a complete novice like me.

How did you guys hook them up? In parallel, I assume. Is there a cross over of some kind?

Gearfreak - thanks for your generous offer, but I'm in Ct. Cheaper just to buy a pair, try 'em out, and throw 'em out if hate them, than to drive to Philly.

Bowtie - are those tan horns cored polyester resin fiberglass or fiberglass covered metal or...? If they're 'glass, how "dead" are they? As uneducated as I am about sound and electrons, I am educated about composites. I can knock out a pair of these pretty easily. Worth the effort?

Thanks,

Ed

Quote:

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Originally Posted by edharbur

Here's what I found:

Zaph|Audio

Thanks,

Ed

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I just went here. I've concluded that I'm Sargent Shultz. I know nothing, nothing!!:confused:

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Bowtie - are those tan horns cored polyester resin fiberglass or fiberglass covered metal or...? If they're 'glass, how "dead" are they? As uneducated as I am about sound and electrons, I am educated about composites. I can knock out a pair of these pretty easily. Worth the effort?

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I really don't know my glass very well, but i'd guess they're just basic polyester resin fiberglass. I snagged them for 5 bucks on ebay many years ago when you could still ship stuff for reasonable fees. I know pretty much nothing about them besides the obvious. 1 inch throat, with only 2 bolt holes on the flange, likely a 500hz horn. They have a beautiful white(enamel?) finish on the inside and both sides of the driver flange. I'll drop a good pic of one here tomorrow in the daylight. I've used them a few times when just tossing together something to listen to during a project or repair in the basement. I've been very happy with Renkus SSD1800's on them, never tried an Altec driver. I wouldn't call them "dead" but what little "ring" you can get by banging on them is well below 500hz.

Ed, I just reworked my A7s with 806A driver and 811B horns,, I found after removing the old 800E network completely and just running a cap on the horn feed it really came alive again,, if fact more so than the high end Def Tecs sitting next to them,, still no bass though and will never expect much but my SVS sub does the 50hz and below quite good,,

my Marantz receiver (SR9600) will attenuate the horns "if needed" in lieu of the old L pad that was in the N-800E,,

Derry

Edharbur, here are a couple of other thoughts to throw in the mix. Your compression drivers, like most, have a "mass corner" of around 3kHz., and the power response (total power out) vs. frequency continues to roll off at 6dB per octave above this frequency. Many horns including the 511 beam highs somewhat on axis, which brings the top end back up quite a bit If you're listening right on axis. In your shop you are probably hearing something closer to the power response, so that in addition to the poorer highs of the Symbiotics are stealing your cymbals.

A big, live room such as your shop will often recycle midrange energy like crazy. Too much mids sounds exactly like not enough highs (and lows).

I haven't had good luck integrating ribbon tweeters with compression horn systems. While they often sound quite wonderful in direct radiator systems, their dynamics don't keep up with the horns and of course their sensitivity is usually much lower. The big Heil AMT does better dynamically, but will probably still need a level boost.

Back when I fiddled with two way Altec systems endlessly, I would usually put a small value bypass cap in the h.f. section of the crossover to bring up the top end. Your compression drivers are probably padded 6 to 10dB even in an A7 system, and AFAIK the stock crossover pads down the driver that much over its entire range. By letting the highs sneak around the pad, they suddenly come up that same 6 to 10dB and the cymbals are back. Experiment with cap value and perhaps even a bit of padding in that section to achieve the best overall sound and/or measured response. The aluminum diaphragms will help a lot also.