Advent Tweeter Comparison

[Guest sbalfour]

I've got boxes and drivers, original crossovers and custom ones

I've made to upgrade or replace them. For my own use, I needed

to know what can match what, and do the claims for any of the

boxes and drivers hold up? Where Advent didn't do something

reasonable, I will.

I've got samples from four series of Advent Tweeters:

* Advent Large orange fried egg tweeter (1971-1979)

* New Advent ferro-fluid fried egg tweeter (1977-1979)

* Advent 5002 1" black dome tweeter (1981) square magnet

(also used on 25th Anniv. Limited Edition 1994)

* Jensen 1" dome replacement tweeter for Advent Large

(1999+) round magnet

Here are the parameters as measured:

Large 5002 New Advent Jensen

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

Re 3.1ohm 5.1ohm 2.2ohm 5.2ohm

Z0 3.4ohm@1600hz 6.0ohm@4925hz 2.8ohm@3875hz 5.8ohm@4020hz

Le 427uH 244uH 111uH 155uH

Fs 670hz 1870hz 1900hz 2330hz

Zs 18.5ohms 7.9ohms 4.6ohms 7.9ohms

Qms 6.81 1.00 2.72 2.23

Qes 1.37 1.82 2.57 4.29

Qts 1.14 .65 1.32 1.47

Legend:

Re - DC resistance of voice coil

Z0 - nominal impedance

Le - inductance of voice coil @1000hz

Fs - free air resonance

Zs - impedance at resonance

Qms - mechanical Q

Qes - electrical Q

Qts - total Q

All four of these tweeters have been in the same 1.6cu.ft. box

paired with the same Advent later model (1975) stamped aluminum

frame woofer. All the resulting systems were advertised as upgrades

or reincarnations of the original Advent Large. The stamped frame

woofers do appear to be drop in acoustic replacements for the

masonite frame ones.

When people toasted the fried egg tweeters on their Advent Larges,

they hopefully installed the lookalike ferro-fluid tweeters of

the New Advent. Advent claimed that they had extended high-frequency

output. They actually had LOWER output at all frequencies after

correcting for resonance, rolled off at a lower frequency on the

high end, and at a much higher frequency on the low end. Audiophiles

weren't impressed. Those who did the opposite in frustration, replacing the ferro-fluid tweeter on the New Advent with the original

tweeter, and set the coutour switch to decrease, actually got a

pleasant improvement. Of course, Advent Corp. disavowed both of

these alterations. But the gig was up: the whole ferro-fluid idea (motor oil and iron filings) and the New Advent itself were white

lies. Nothing about the tweeter or system was what they claimed.

The New Advent and cheaper sister Model 1 were the first and last

products to employ the ferro-fluid tweeter.

None of these tweeters are interchangeable with any other. It's

infeasable that the resulting systems could remotely resemble each

other in timbre. In particular, the Jensen tweeter can NOT

replace the original fried egg tweeter or any other tweeter without

a redesign of the whole system. They're just handing you whatever

they have on the shelf. With elliptic Q's, the Jensen and New Advent

tweeters would be very hard to integrate into a 2-way - they'd need a

rolloff at least an octave above resonance, and two octaves would be

better. Notch filters would need large precision components.

Clearly, these two tweeters are poor.

The 5002 tweeter looks decent, and they damped the resonance

well - it's going to be a friendly driver to work with.

Henry's original tweeter had a near-elliptic Q, but very low

resonance. Henry knew how to handle that. I think that's part of

the explanation for the high-Q (>1.0) high-pass filter; he needed

to clip off the resonance sharp. Henry's original is a quirky

one-of-a-kind. You won't find a plug-in replacement for that one.

Apparently, there's a 5th Advent tweeter, another replacement for the

original fried egg on Advent Large, which has a hard catenary shaped

dome described at Layne Audio (out of business - no one answers phone

or email - but website remains). If anyone knows who makes that one,

or where to get it, I'd like to test it, too. I've not seen one on

Ebay, so it may have been proprietary to Layne Audio.

Stuart

[Carlspeak]

"....Apparently, there's a 5th Advent tweeter, another replacement for the original fried egg on Advent Large, which has a hard catenary shaped dome described at Layne Audio (out of business - no one answers phone or email - but website remains). If anyone knows who makes that one, or where to get it, I'd like to test it, too. I've not seen one on Ebay, so it may have been proprietary to Layne Audio.

Stuart"

Madisound has a 4 ohm tweeter that fits your description. I just installed a pair in some Allison Model 7's. They sell it as a replacement for a Spica loudspeaker. It's one of the few 4 ohm tweeters they have available. Nice sound and very efficient. No specs.

It's all about the music

Carl

Carl's Custom Loudspeakers

[Pete B]

The only catenary dome tweeter that I know of is from Audax.