A7 Lost Cymbals

[edharbur]

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

[bowtie427ss]

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

[GM]

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

[mah]

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

Marshall.

[RonSSS]

Replace the symbiotic frams.

[Panomaniac]

Ditto - replace!

[GM]

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

Marshall.

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

[gearfreak]

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

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.