fEARful part nine (9)

[greenboy]

Chances are good that's my xover, as i just got a shipping notice

Who knows: I might soon join the rank of passive crossover users.

I'll post a bunch of pics and such when I get it and get into the inside of my cab, probably next weekend. Maybe see the old xover in the classifieds

It'd be great seeing your personal page updated for sure ; }

List of stuff to do:
-rip&replace xover (soldering time, yay)

Really easy stuff as long as you don't do something foolish like using 12 gauge internal wiring which is a liability.

-cut, build and stuff new midrange box

How bad is it? Too small? Not deep enough? I bet it's one of those cylindrical things, aligned dead center. That's an acoustic problem, though if larger it can be helped a lot by sufficient stuffing. Even a cube with driver dead center is an improvement... If you have a 1/2" thick brace going across the baffle, you can build the chamber with 1/4" ply, BTW.

-add bracing to the top

Is this the bouncing microhead thing or is there actually a mushy knock test? Either way, even a 1" stick will knock it back, or a "cross" that need not even reach the edges.

-add a cross brace from handle to handle (tentative)

Is your cab pretty much unbraced? (Pictures?) Check the second detail on my bracing page which can use 1" or 1.25" struts, ties in the back to the sides, provided there is already some girdling. I considered adding a side to side to THAT, for EXTREME BRACERS, but with my cabs I haven't even noticed a need for a couple of struts. Maybe that will change when a IPR 4500 shows up.

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[rpsands]

The midrange chamber is a round one aligned dead center. Most of the bracing issues I notice are on the top where there's no midrange chamber to assist like in your plans (my micro heads move around on top), and right around the handles.

I've only had it opened once, but it had girdle bracing very similar to the fEarful but not very close to the handle. I might not wind up adding any after the midrange chamber goes in, but we'll see.

There's no bracing across the baffle at all just the girdle pieces that hit it along the sides. I've got a sheet of 15/32 arauco so anything I do is using that I think.

I might see if I can do a dowel top to bottom actually, but we'll see once I get inside and start digging. Need to find out where the Xover board is and all that especially before I plan anything too heavily.

 

[lelandcrooks]

Chances are good that's my xover, as i just got a shipping notice

It is.

I've had a helluva time getting all the stuff in to offer these. Still short some stuff. They're also fairly challenging for physical layout on the midrange. Big components.

 

[thudfromafar]

Leland you're doing the right thing by getting in on this. This is a good time for fEARful!

 

[greenboy]

I might see if I can do a dowel top to bottom actually, but we'll see once I get inside and start digging. Need to find out where the Xover board is and all that especially before I plan anything too heavily.

I've done similar in standard 24" x 24" stubby cabs, but frankly it's not the solution you've been told for a 30" tall cab, unless tied into cross bracing all across every so often. Then too, fEARful baffles are so slim front to back crossbracing would be a joke in single woofer boxes. So you end up with only side to side crossbraces making much sense in fEARfuls but that doesn't make much sense without some bracing for the other directions.

...I still see two things bracing should address: localized damping, and the panel rigidity thing.

 

[greenboy]

They're also fairly challenging for physical layout on the midrange. Big components.

Your fingers are just too big ; }

EDIT: I don't know if the board designer envisioned high-power L-pads on the same board.

 

[rpsands]

I've done similar in standard 24" x 24" stubby cabs, but frankly it's not the solution you've been told for a 30" tall cab, unless tied into cross bracing all across every so often. Then too, fEARful baffles are so slim front to back crossbracing would be a joke in single woofer boxes. So you end up with only side to side crossbraces making much sense in fEARfuls but that doesn't make much sense without some bracing for the other directions.

...I still see two things bracing should address: localized damping, and the panel rigidity thing.

Gotcha, that makes sense. The big thing is vibrations on the top panel and the handle area. I might post some pics and ask for your input if you don't mind.

First stop is new feet for my Genz head though. They really are terrible.

 

[greenboy]

rp, are you using distortion/fuzz/OD at gigs?

 

[praisegig]

Hey Lon,

I set a page for you about three weeks back. It's a 12/6, right? So have at it... You guys really need to take a look around ; }

Thanks greenboy. I updated my WIKI page with build pics for my 12/6 cabinet. Hope it helps others in their building process. I see a 15/6 and 15 sub in my future.

 

[rpsands]

rp, are you using distortion/fuzz/OD at gigs?

I use a VT deluxe with four different presets -- only two obviously dirty settings, but one of them is pretty brutally fuzzy.

 

[CDweller]

Speaking of golden, Leland sent me some pics of what he's been doing for a number of people today, to make sure we were on the same page. This is a 15/6's 3015LF and 6ND410 sections on separate boards:

Oh, them's too sezzy for words!

 

[WCunha]

I'm going to start my crossover soon and I am using the wire wound resistors. Does anyone know if it is ok for the body of the resistors to touch each other? I think I am going to use a combination of straps and silicone caulk to hold them in place.

 

[BurningSkies]

I'm going to start my crossover soon and I am using the wire wound resistors. Does anyone know if it is ok for the body of the resistors to touch each other? I think I am going to use a combination of straps and silicone caulk to hold them in place.

If you can get air space between the resistors, please do. Remember, they generate heat...The last one I built has them raised off the board so they get airflow beneath and between.

 

[WCunha]

If you can get air space between the resistors, please do. Remember, they generate heat...The last one I built has them raised off the board so they get airflow beneath and between.

Gotcha and thanks.

 

[lelandcrooks]

You can't see it but there are vent holes drilled under those resistors just for heat reasons.

 

[svtb15]

I was looking at some of the schematics for the 15/6 crossover and often wondered why the Mid drive is to be wired out of phase?
I have seen that in other crossovers too..
Thanks for any info.

 

[greenboy]

I was looking at some of the schematics for the 15/6 crossover and often wondered why the Mid drive is to be wired out of phase? I have seen that in other crossovers too..

Reverse polarity, you mean. Yeah, really it has to do with what is going on with phase and actual driver response in the specific enclosure. With textbook crossover designs/calculators there are guidelines about what polarity is going to work for what order of whichever type (Linkwitz-Riley, Butterworth, Bessel, etc at various slopes) without a big null at the crosspoint. Those nulls are due to phase cancellation where both drivers are making output in the crossover region and polarity choice is made to defeat these gaps.

Since textbook designs and calculators don't take into account the specific drivers being used, with their changing impedances and reactance at various frequencies, and their actual frequency response once loaded into the specific enclosure, they really don't address what might happen in the real world. They are mainly of use as a last resort, or to illustrate principles before going to more complex subject matter.

Serious crossover design {or crude attempts at it;} is done beyond what these simplistic generic calculator-based approaches are meant to predict. With overdamping and underdamping used to shape actual driver response as well as make the crossover, and driver placement on the baffle contributing to phase/response changes, and any driver acoustic source point usually being at different places on the z axis (fron to back), it's often the case that reversing polarity is going to give the best transition, the more even response.

Hey, did I confuse both of us? ; }

 

[svtb15]

Way confused. but i did pick up some stuff that does make sense to me and i can understand... Thank you for the time and answer...

 

[greenboy]

I had some graphs that illustrate the difference but they got lost when my internet hosting became unreliable, and later my computer went down and more tolls accrued when I had to switch to Win7 64-bit. It's amazing how much stuff gets broken when Microsoft is involved ; }

I mean The dog ate my homework, man.

 

[WCunha]

It's amazing how much stuff gets broken when Microsoft is involved ; }

That's why I have a Mac