conduction

[grindstone]

Advance apology if this is inappropriate here; hoping this is a fair spot for an off-brand corner horn wonder. Quite rambling, too, but I'm working this out aloud in slow-mo. Should politely dip a toe for inappropriateness but life seems to allow very little time for audio let alone well-formed inquiries so I'll do a major-dump and hope for forgiveness later. Simple wonder, just complicated setup.

Basically, currently-engaged in resurrection of Georgian 600's (eg attached please find the current state of utility cab candidate no1 for ref) and stumbled on something that spun my gourd tonight.

So I'm listening to the other (untouched & fully-dress-cabbed yet) unit while working, right? Pots are toast, caps are 50-something, etc., the number of drivers that pass signal at a given time is highly variable Serendipitously, tonight I lose everything but the woofer. Usually the squawk works and I stick my head in the top woodhorn (reentrant phenolic 828 does 300-600 or something outta that thing + usually get the 600-to-3k+ outta the same 828 front radiation in the little horn easily visible in prev pic (t350 missing/removed in that photo)). For ref, LF cut target is 300 in this particular deal (x336).

Well, pure conduction was producing non-trivial sound out of the 300 Hz horn. Didn't/couldn't measure in the garage. Hopefully I can get some numbers outside before winter hits here in the UpNorth.

For completeness, I need to say I've been messing with speakers for long enough to have a fair idea about panels and radiation and stiffness and all that--in fact, anything more than a 5" span unsupported doesn't happen in any box outta my hands anymore. That-disclaimed in advance, I was blown-away by how much sound--howevermany dB down--I got by sticking my ear to the top woodhorn. Best guess is it's a '58 so the half-inch ply is from when ply was still half-decent ply. The 300 Hz top horn is glued (with cleats and nails) on top of the bass bin. Pretty-rigid/well-coupled, that way.

Well, obviously the first thing I thought of was sawzalling that top unit off, adding a bottom/baseplate, and getting some isolation between the basshorn and the rest of the rig. And yeah, I realize that there are probably waaaay better 300Hz horns--maybe I'll get there sooner than later, but I'm still cleaning mouse turds and bleaching mildew Baby-steps...

I've never owned a capital-K actual forum-sponsored khorn, but I see some differences in top-module risers vs. "more integral" top units and I wonder--esp in view of the discussion about how high the LF units were crossed vs. say Middle C or whatever else, blah blah. In short, a common criticism of muddiness, basshorn crossed too high, etc.

Instantly upon hearing only the W conducting out the 300Hz horn, what I thought was that it's not just the basshorn delay due to path, but maybe (?) what is partially responsible for the pounding taken on the discussion boards for years is just plain wood conduction mucking in there, too?

I don't expect anyone to dummy-up R's on legs of their squawk & tweet, but I also figured some such maniacs as frequent this place might've already covered this turf.

I guess it's the same as anything--choose your method of dealing with panel excitation. For me, that amounts to tiny unsupported spans toward the goal of making the sub-span tough to excite by whatever passband happens in that local space. Well, it's not like this thing is concerned with precision wave-formation but still I wonder what the best method might be to stiffen that thing above it's passband. "Do the usual" except as exoskeletal-as-practicable?

Experiences, opinions, rants, hypotheses, bald conjecture, and just plain blow-holery welcomed with gratitude.

Thanks for the time.

PS Is there a better/more-approp. spot for EV stuff?
PPS Not a complete poseur--'81 Cornies are cooking Cannonball Adderley while all these electrons were being dispatched and my feet seem to be tapping

[moray james]

Great post: any way to provide either more pictures or a plan drawing of the beast? There is a liquid compound used to treat wood rot which soaks into the wood and then sets up hard (it is in fact an epoxy) I will find the name, you might consider something like that to help. You can also add in as many small hard wood cleats struts and battens as is possible to stiffen up the structure internally so put your engineering cap on. One other possible option after you have braced and epoxy coated might be to inject urethane foam into any cavities to provide additional stiffening and damping and to prevent acoustical coupling. Hard to make many more suggestions than that without more visual to go by. Best regards Moray James.

a link to the penetrating epoxy compound

http://www.rotdoctor.com/products/cpes.html

[Daddy Dee]

Very cool project. I'm no help on tech stuff, just would offer that there is no need for concern about your post being OK in this forum. Good luck on the adventure of restoring this beast.

[Marvel]

There is a liquid compound used to treat wood rot which soaks into the wood and then sets up hard (it is in fact an epoxy)

Rotdoctor is one product...

http://www.rotdoctor.com

Bruce

[grindstone]

Thanks for the hospitality and the responses. I had no idea of such products. No plans I know of (hard to find anything in-fact), but they're a sort of "compact" version of the original Georgian IV's--maybe 50 lbs lighter and only around 4 feet tall--still 15wk's and pretty much khorn bass units of the time if I have that straight. 6x12 throats and the sinuses are used. Took a lot of pics during tear-down but they're all close/detailed/limited. This is about the best I can do for relevant photos right now.

Really, what I heard was just a horn being a horn and I have no defense except blaming beer for why that seemed profound-enough to post about except for thinking of khorn crossing region discussions.

Today, I'm a little more ambivalent in the sense, that, however-imperfect, what the thing does is what it does and maybe part of my stewardship of these lovely giants might be to let them be. Waffling. Also was thinking I'd like to rig something by way of reversible/removable clamps to hear what's to be heard. That stuff is pretty far-out, realistically, at the current rate I get to work on them and they're in quite bad shape. Either way, I'm interested in the data so hopefully I can take some soon.

Tried to listen again tonight but the intermittent-contact-gods weren't with me--the MR was working

Can't seem to figure-out how to do multiple images so maybe a following post for that.

Thanks again.

[grindstone]

for once there's plenty of room for bracing...

[grindstone]

About done with the drilling-out fasteners, vacuuming, blowing, scrubbing (and scrubbing and scrubbing). Went through a couple belts hitting nails and miscellaneous stuff. Bottoms still need a good bit of attention. Turns out they were gloss and I got a coat of flat on. Started raining before they got dry It can all come-off again if it has too--these things make time and space conform to them (we have a respectful standoff for now after they hosed my back). Have not yet acquired rotdoctor but learned a Great Deal when sanding the woodhorn. Holy cr*p for loud Primary offender is the (largest-unsupported span) top. Bot and sides were no peach, but running a sander on the top and standing right in front of the mouth was instructive

[grindstone]

Here's the flat vs. the orig color of the brackets. Thing had individual runs to 8 terminals plus the inputs on the back for approximately one zillion feet of tinned stranded zip cord. Got the magic phenolic reentrant (MT30 i think) off the 828HF and blasted the tweeter and squawk brackets today.

[grindstone]

First AC and attempts at measurement this past week. Made some faux corners with plywood and whatever else laying around. Impossible to measure in the city with everything happening. Much to do and temperatures are falling.

If any khorn-people are still out-there on my monologue-thread: how much space do these things need to really work? My experiments say I just start to get bass right at about 8-10 feet? I don't know where to measure that stuff, for one, but I'm also (re)considering where they might land.

(And yes, one day I promise to return to the topic of the mud and all that--thanks for the bandwidth).

[Marvel]

You won't get much bass until those are snugged up tight into solid corners. Your pic with the plywood staning up making corners isn't going to give much of a real sense o what these will sound like.

You were worried early on about whether or not it was appropriate to post about your work on these. Check out Woodog's thread on his acquisition of some Patrician 800s and refurbishing. It should be an encouragement!

Bruce

http://community.klipsch.com/forums/t/160876.aspx?PageIndex=1

[grindstone]

Thanks for that and for the support. I'd seen some of the photos on another site but didn't know of the thread. They were really in comparatively quite good condition before the top-notch effort--I bet they're amazing. Glad to see the really rare stuff saved (and glad I'm not the only poor sot learning exactly how much work this stuff is). These particular units are about endurance in every act; removing staples alone is a growth opportunity.

There looks to be a lot of useful information in that thread. I'm not even started on the shell and in-fact the other cab is untouched completely. I'm just happy at least half the drivers seem to mostly work at this point

[grindstone]

Neanderthalled the second decorative cab off unit 2 today. This one is was different in that the tailboard was glued. Pretty sure the utility cab hasn't been out of that thing for the whole time. Fewer things lived in it and more things lived on it

Someone pitched a label and a knob inside the basshorn--a nice surprise to find between bouts of wailing on an impact driver and drilling hardware. Sick of drilling fasteners, mildew, mold, rust--and really pretty stoked.

Classic stuff...do maybe 25 screws in 10 minutes and then an hour or something for one. It's at those times it's really nice to have one upped and running so 30 minutes of barehanding a hacksaw blade sails right by

The basshorn grille frames are fir--the sort of stuff that's been long-gone for a while, or at least something I certainly never see. Apology for lousy photos again. So here's the newly-exhumed utility job on the right next to the runner on the left. And the Magna Carta has nothing on that label for brittle.

[grindstone]

Pretty big-hour weekend effort. Got the other one almost caught-up to the first--scrubbed, sanded, & painted utility cab, built XO, inverted woofer and rewired, got second one running. Spent the afternoon & evening wearing a dust mask pulling staples and completing neanderthal work on the basshorn grille frames and de-cane-ing those. Cleats were glued and screwed and the screws of course have been rusting for ages so every one was a caveman focusing exercise. Chisel, gnaw, repeat. Little clouds whatever was growing on them fly out with almost every smack. The theme of patience continues, but it's even easier to work while listening to two of them than to just one.

The environment is more like monitors running both in a single-car garage, but it was some good fun and a nice reward. Mostly listened to jazz and a bit of blues today and used a few boards propped for corners. Bass will not be a problem and the presentation made it worth a great deal of drudgery. There are a lot worse days in life than a day in the garage messing with cab-stuff while listening to two of these things even if it was freezing cold.

There is still work to do on the bottoms of both utility cabs, but I was antsy to get them running and see what was to be seen. Full-disclosure, I'm racing winter in my uninsulated and unheated garage, too.

[grindstone]

Maybe one thing glossed-over was the bit of XO's. First, well, they're potted so I had to un-pot and fish-out the L's. Not really recommended, but I was sort of gung-ho about trying it with the values that shipped and well there was only one way to know that. The L's measured really close to the specs.

One thing I wondered was how the EV engineers could pack so many L's so close together and toss them all in a steel can and call it done Seemed strange for men of science to use air cores crammed together inside steel cans...

I don't have my notes, but, after I got the first can empty, I played games with my LCR meter and two chokes at various positions inserted into the can. It may be that I ran insufficient current, but I was surprised at the effectively negligible difference in readings between the parts in or out of the can. Still and all, it's not like these corner horns are about minimal space so my hacked-up board has a bit more space and will still fit in the woodhorn sideways if they end-up in-use.

The filter responses are a little weird, too, but I trust those guys to have arrived at something useful and again I wanted to hear that. I just used extra barrier strips to be able to roll caps and make some fun. I never bought full-audio-nuts boutique caps before so I splurged on this project to see if I can hear anything. So far, I can't tell much if any difference but it's not much of a test in the garage, either.

And I can't get too bent on the filters until I can convince myself of having a decent measurement of that unmeasurable reentrant + front expo compound horn. I don't even know what makes sense to measure and that's going to take a while to think about.

[grindstone]

Lots of work, little to show--mainly, sanding, filling, and painting basshorn grille frames. Drilled-out the last few broken screws. Still one broken frame to repair. Would have been smarter & faster to rebuild the basshorn frames from scratch, but it seems the fir needs to stay where it belongs so the little holes, broken staples, and dings each need some time.

Starting (barely) to rebuild bottoms. Chose and cut some red oak to replace fir feet. Got sidetracked watching football instead of finishing the feet.

Sat and listened to them a lot this past week (instead of working on them like I should have been). Ran a lot of material through them to try to learn their secrets. Walked around, craned my neck, moved them around, twiddled the pads, flipped through a lot of material. I can never guess which recordings they'll do better or worse with, and that's new for me. The only thing I know for sure so far is that they do not suffer poor recordings well. If something is poorly made, they are (giant) microscopes. Probably safe to say that the T350's are some good parts, too. They do the alnico slinky-ness and they can startle as well. For that matter, the whole rig can do startling dynamics sometimes. They do space better than I'd have guessed based just on running mono for a while. Can't separate them enough to be fair in the garage yet so that's pretty-much the end of reportage on sound-stuff for now.

[grindstone]

Cold spell dashed progress for a while. Finally finished the bottoms and got the rails on and bunged-in some furniture glides. Somehow hit yet one more screw when assembling cleats so one last drill-fill-sand-paint short loop on that spot. After reinverting and rewiring, just sat and listened (still in the garage and within 5 feet of each other). Did a lot of listening this weekend. Soooo, utility cabs pretty close. Be nice to get some insect-barrier similar to what Greg does across the rear end, but not sure about the form just yet...do casters somewhere down the line...permanently mount the xo and controls. Beyond that, not sure what's next. Still (loosely) trying to figure out what to do with the dress cabs. A lot of thinking, actually, all dependent on how they sound longer-term.

Been picking at making a model for the (848HF) compression driver to be able to sim the reentrant expo + conical low-midhorn but that's tough-going and I can't get my ripple to line-up with the ripple in the measurement. Not anxious to disassemble the driver to try to measure internal V's yet either. Still also thinking about what started all this--the woodhorn conduction and isolation of same, etc. That can go a lot of directions but space is tight under the dress-cab. Definitely more to come on that at a later date. If there's anyone out there still reading this stuff that has thoughts on the current compound (PA?) drivers vs. the old one that'd be good stuff for me to hear.

They do a lot of things very well. So much so I've been forced to confront some personal biases about the compound PA drivers and some other things. A couple times they've made me start giggling like a little kid. Still learning the sound and struggling with putting words to it.

A neighbor happened by during today's testing and he was really surprised and enthusiastic. (He asked what I spent so far and I said about 200 bucks for xo parts, repair/finishing supplies & hdwe and maybe 300 bucks for craft brews...)

Still it's been a rewarding use of every spare minute since late August. For now, the plan is to maybe horse the utility cabs inside for the winter and go from there. Be nice to get another set of measurements done outside if weather permits. Need to complete basshorn exhaust frames with the cane and all that. Not sure when the work on the dress cabs starts (or what that objective even is).

[Axz Hout]

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