30904 attenuator with 902 drivers in AS101's?

In a quest to make my HeathKit AS101's even better I have rebuilt a set of 908 drivers into 902's. I believe these will be a little hotter than the 806 drivers that will be in there currently. My game plan is to eventually cross them over at 1200HZ like the Model 19's but in the meantime can I use these 30904 attenuator's with the stock crossovers and the 902 drivers?
My understanding of the 30904 attenuator's is that they knock down the mid frequency's so that the HF better matches the mids.
They also have a zoble network for the woofers, should I worry about hooking that up at all?
Reason I ask, there was a set of clean looking 30904 attenuator's on e-bay this afternoon that was just listed for 35 bucks. After a quick bit of research I purchased them but I'm not sure it will really do what I want to do.
Thanks for any input.

BillWojo

I thought about buying those also. I read some good things about them from a few trusted people. I am curious about just running the HF section also. I can build the HF section for about 20 bucks with new parts from parts express.

the zobel in the 30904 was designed for the 411 woofer in a sealed alignment. IMO, to assume it is in any way appropriate for a 416 in a vented alignment is an exercise in pure wankery(assuming you're reading Zilch posts).

The other half of the 30904 in addition to all the wonderful things you have read that it will do, will also alter the impedance load the crossover sees from the driver changing it's knee point, and likely other subtle characteristics.

My advice would be "slow down grasshopper! one change at a time, listen, evaluate, proceed"

Just my .02 of course, i'm not a big fan of the vacuum tube either so, you may want to take into account that i don't know "jack".

Quote:

---

to assume it is in any way appropriate for a 416 in a vented alignment is an exercise in pure wankery (assuming you're reading Zilch posts).

---

Thanks for that Bowtie. It has been a long couple of weeks I needed a good laugh. Almost spit coffee on my monitor. :Lmao:

I always enjoy reading the Zilch posts.

bowtie427, I think I have read every post on AS101 and Valencia mods that exist on this forum. I cant's really find any definitive answers as to what works the best. It seems the more I read the more confusing it gets especially with all the lost links and pictures. Things I "think" will help:

1) Raise the crossover to 1200HZ like the Model 19
2) Switch to 902 drivers to raise the HF response
3) Lower the mid portion of the horns to bring the HF portion up
4) Dampen horns if ringing is present

Sorry about that "tube" thing, guess there not for everybody. I kind of like them and they seem like a good match for high efficiency speakers.

My SS system is a set of Carver Silver 7t monoblocks with Carver Amazing Platinum ribbon speakers. So I'm not biased against SS amps. Those speakers are at the opposite end of the spectrum compared to the efficient Altec speakers.

BillWojo

bill if you decide the 30904s don't work for you. I could use them with my 411s. :)

Quote:

---

Originally Posted by bowtie427ss

the zobel in the 30904 was designed for the 411 woofer in a sealed alignment. IMO, to assume it is in any way appropriate for a 416 in a vented alignment is an exercise in pure wankery(assuming you're reading Zilch posts).

The other half of the 30904 in addition to all the wonderful things you have read that it will do, will also alter the impedance load the crossover sees from the driver changing it's knee point, and likely other subtle characteristics.

My advice would be "slow down grasshopper! one change at a time, listen, evaluate, proceed"

Just my .02 of course, i'm not a big fan of the vacuum tube either so, you may want to take into account that i don't know "jack".

---

+1, saved me some typing............ I knew 'jack' once upon a time and still don't prefer tubes except in certain apps and even then not enough to return to that particular aggravation. There is a certain 'synergy' with compression horns and 'full-range' drivers though, so bi-amping is the best of both 'worlds' IME.

Anyway, for any basic point source+horn system, CD horn EQ [LCR network] to level match [tonally balance] the horn to the woofer is required, which in turn unfortunately shelves down the HF, which wasn't a problem when these systems were conceived since there were no recordings with any to speak of and the amp's high output impedance had a built in 'smiley face' EQ to boost the low/high ends, then later they just added bass, treble controls via variable damping [DF] to 'boost' it further.

Most of us nowadays don't have the proper tube electronics to do it up right, complete with the 'flabby'/loose bass as the trade-off, but we can easily do similar by adjusting the horn/woofer's tonal balance with the horn's attenuator and once this is dialed in we can 'lift up' the HF to blend in by adding a by-pass cap around it, i.e. essentially do what the M19's fancy XO allows.

IIRC 0.1-1 uF was the most used range way back when, but let your ears rule since we as a species have incredibly poor HF hearing once we get a little age on us and room acoustics, signal chains varies greatly. Zobels are only really needed for when there's a high output impedance source or have a complex passive XO and even then only if you're wanting a very flat frequency response like is required in a studio monitor type app.

Note women and especially children are [much] more sensitive to upper mids/HF, so they're the ones I used to find the best trade-off woofer/horn balance and cap value. Of course if it's a 'man cave' app......... ;)

GM

I owned a pair of AS 101's and originally joined this forum to get info on rebuilding the crossovers back in February of 2009. Since then, I sold them and now my main speakers are Model 19's and Model 14's. In my opinion (and I'm far from the most knowledgeable person here--but did own a pair of 101's for years) your best best is to replace the stock Heathkit crossovers with stock Model 19 crossovers. You've got a 416/902 combination--similar to the later Model 19's which used 416-8c and 902 combination. I would also experiment blocking off part of your port in the AS-101's to achieve a deeper tuning since the model 19's are tuned to a deeper tuning than the AS-101's (you probably know the 101's use a cabinet tuning similar to Valencias). Good luck whatever you decide. Those AS 101's are great speakers and I'd probably still own them if I swapped out the 806's for 902's and did the other mods I'm recommending you do. Here's a pic of mine (hover over thumbnail with cursor)...

Attachment 3119

Quote:

---

Originally Posted by BillWojo

In a quest to make my HeathKit AS101's even better I have rebuilt a set of 908 drivers into 902's. I believe these will be a little hotter than the 806 drivers that will be in there currently. My game plan is to eventually cross them over at 1200HZ like the Model 19's but in the meantime can I use these 30904 attenuator's with the stock crossovers and the 902 drivers?
My understanding of the 30904 attenuator's is that they knock down the mid frequency's so that the HF better matches the mids.
They also have a zoble network for the woofers, should I worry about hooking that up at all?
Reason I ask, there was a set of clean looking 30904 attenuator's on e-bay this afternoon that was just listed for 35 bucks. After a quick bit of research I purchased them but I'm not sure it will really do what I want to do.
Thanks for any input.

BillWojo

---

Thanks for the info, especially about the port tuning. I've come to my own conclusion several days ago to go after a set of Model 19 crossovers. Reading what you said verifies that decision for me. I've been looking for a set on ebay and have started a parts list if I have to build my own. I'll place a WTB add on here also.
Thanks

BillWojo

I think GPA builds new ones. Their other crossovers are around 175-200 each. Thats probably cheaper than a pair of originals. You would have to recap the originals anyways.

I know Jeff Markwart has a plan on his site. There are some other revised plans out there as well. If you buy good parts the xovers are pretty expensive to build, but at least you have all known good parts.