4344 BUILD, and some questions for the pros :)

[jlwitherell]

Hey guys,

Trying to get finished up on my new build and am stuck on a few items (being a bit of a newbie):

1) Anyone know where to source some L-Pad knobs like original JBLs? And/or, does anyone have the diameter/depth of them (so I can at least make the recesses and help move forward)?
2) Is it OK to mount terminals directly attached to MDF, or, is getting something like high voltage insulation board necessary? The L-pads don't need insulating washers do they?
3) I'm going to build Giskard's charged coupled network (and have very limited electrical knowledge). It calls for a 3 Mohm resistors for the charging. I'm wondering of I'd be safer using two 2.2Moh's in series in case one fails? Or does this never happen?

Thanks for any help in advance, been having lot's of fun! Special thanks (so far): I stole JBLP's router jig design (worked awesome) as well as got a lot of ideas from his amazing build. He also provided me with his baffle layout plans (thanks so much), and Odd gave me the box plans which for me were modified a bit. Some pics of the build:

[JBLP]

You're going fast; you will overtake me!!!
Good work Josh.

[audiomagnate]

[QUOTE=jlwitherell;367153]...calls for a 3 Mohm resistors for the charging. I'm wondering of I'd be safer using two 2.2Moh's in series in case one fails? .../QUOTE]
I would just use what the design calls for and not try to second guess it by changing any component values. Nice work.

[jlwitherell]

JBLP: Thanks man! your project has been much more than just helpful. I've found a fair bit of extra time lately, it's been fun ;) Getting excited to hearing these! I'm hoping to have them running before it gets too cold, but most likely will have to do the final exterior finish come spring time.

audiomagnate: Thank you. I've read (somewhere, and in a few places) that anywhere from 2 to 6 Mohms is fine for the charging, my thought is that if I only use one resistor, and it fails, perhaps the battery could send too much DC to the speakers and fry them, but I'm not sure. This is why I was wondering if two in series (which are still within the total range; (2) 2.2 Mohms in series would be 4.4, and still in range) could possibly be a safeguard, as if one fails I'm still within the acceptable range of resistance... My guess is you're correct and I'm over thinking it..

[Odd]

Very nice woodwork!

1. Parts (https://www.parts-express.com/Search.aspx?keyword=l-pads&sitesearch=true) Express (https://www.parts-express.com/Search.aspx?keyword=l-pads&sitesearch=true) and many others.

If you use the 4355 crossover, l-pad for mids. are 16 ohm
I have only found 16 ohm with short Shafts 3/8"

2. Cut out one large hole in the back panel and mount a plastic plate or other material on the inside and mount terminals on this.

There is no reason for two resistors, it passes no current here

[jlwitherell]

Thank you Odd!

I couldn't find Knob replicas searching around the internet, all I was able to find were the knobs that don't recess like old JBLs do. But, I found a guy on EBAY who makes them out of either delrin or alumimum and I ordered the delrin (hope they work!). The L-Pads I ordered from parts express and apparently when arrived are made by Dayton, which is cool as these are the same capacitors I'm using. They are all 8 Ohms.

Thanks for the tip on mounting, heading to a Plastic shop today to see what I can find.

Still a little confused on the resistor. 3MOhms is a huge resistance value so it is limiting the current from the 9v battery greatly. My wondering is do resistors ever go bad and as such the 9 V battery could sent too much DC to the speakers. If so wouldn't using two of slightly less resistors safe guard this. I apologize if I'm not understanding correctly, or just plain being dumb! ;)

[fpitas]

Still a little confused on the resistor. 3MOhms is a huge resistance value so it is limiting the current from the 9v battery greatly. My wondering is do resistors ever go bad and as such the 9 V battery could sent too much DC to the speakers. If so wouldn't using two of slightly less resistors safe guard this. I apologize if I'm not understanding correctly, or just plain being dumb! ;)

As Odd said, it passes insignificant current, it's just to bias the capacitors. A single 3M resistor is fine.

[grumpy]

seems like ebay seller "sign-shop" (Timmerman) sold foilcals, grill pegs, and other bits... I don't recall if he
also was the person who at one time made replacement L-pad knobs... might be worth contacting
if no one else remembers who it was that had been making these. I might be remembering incorrectly.
Maybe try the sketchy search feature here...

Also, if a 3Meg resistor to fail, the most likely scenario would be an open or intermittent, not a short...
so I wouldn't lose sleep over it.

[hjames]

That's him but it was sign--shop with 2 dashes in the username!

http://www.ebay.com/sch/sign--shop/m.html?item=250690778621&hash=item3a5e55b5fd&pt=Vintage_Electronics_R2&rt=nc&_trksid=p2047675.l2562

Write him directly see if he has the knobs ...

I've gotten speaker grill pegs and various JBL "foilcals" from him in the past and he's easy to deal with!




seems like ebay seller "sign-shop" (Timmerman) sold foilcals, grill pegs, and other bits... I don't recall if he
also was the person who at one time made replacement L-pad knobs... might be worth contacting
if no one else remembers who it was that had been making these. I might be remembering incorrectly.
Maybe try the sketchy search feature here...

Also, if a 3Meg resistor to fail, the most likely scenario would be an open or intermittent, not a short...
so I wouldn't lose sleep over it.

[jlwitherell]

seems like ebay seller "sign-shop" (Timmerman) sold foilcals, grill pegs, and other bits... I don't recall if he
also was the person who at one time made replacement L-pad knobs... might be worth contacting
if no one else remembers who it was that had been making these. I might be remembering incorrectly.
Maybe try the sketchy search feature here...

Also, if a 3Meg resistor to fail, the most likely scenario would be an open or intermittent, not a short...
so I wouldn't lose sleep over it.


LOL, nice, that's who I ended up getting the knobs from! Thanks Grumpy & hjames. Also, Grumpy - thank you very much for the single resistor failure scenario, that is exactly what I was looking for... :)

[jlwitherell]

Progress is still being made, I'll get some pics up shortly but coming up on a couple more questions:

1) As far as tuning; it appears original 4344's were tuned somewhere around 30hz or so (Anyone know the actual tuning Hz?). When I run WinISD 50hz tuning gives almost a completely flat response and steeper slope at around 50. Tuned to 30 gives a much more gradual slope, more on the low end, but losing some higher. What is the consensus on which method is better (what sounds better)? Flat with steep slope, or let her go lower like what appears was original? (I'm guessing that somewhere around 30hz will be what is recommended)

2) Back to the crossovers. For the charge coupled design do I put 3Mohm resisters at each charging spot, or one for the entire crossover and branch off of it?

Thanks for any help guys!
Josh

[Odd]

Try tuning to 32Hz

3 Mohm resistors at each charging spot.

[martin2395]

Try tuning to 32Hz

3 Mohm resistors at each charging spot.

That's a good question actually, why do you need a separate 3mOhm resistor for each pair when they still go to the same point on the battery?

[Odd]

That's a good question actually, why do you need a separate 3mOhm resistor for each pair when they still go to the same point on the battery?


You challenge my old school skills.
Ok, there is a voltage drop across each resistor.

[jlwitherell]

But what about the resistance change being in a parallel circuit (admittedly, within a crossover network I don't know how this actually would measure out). But, in true parallel the total resistance is the reciprocal of the added reciprocals of the various resistors: For four 8 ohm resistors in parallel, the circuit would read 2 ohms. 1/8 + 1/8 + 1/8 + 1/8 = 4/8 (reciprocal) = 8/4 = 2.

[Odd]

But what about the resistance change being in a parallel circuit (admittedly, within a crossover network I don't know how this actually would measure out). But, in true parallel the total resistance is the reciprocal of the added reciprocals of the various resistors: For four 8 ohm resistors in parallel, the circuit would read 2 ohms. 1/8 + 1/8 + 1/8 + 1/8 = 4/8 (reciprocal) = 8/4 = 2.

I do not follow you here. ?

1/8 + 1/8 + 1/8 + 1/8 = 4/8 (reciprocal) = 8/4 = 2. Correct.

Edit.
The 3 MOhm resistors are not really part of the crossover. They provide only a small voltage to the capacitors.

[jlwitherell]

I've read for charge coupled designs that anywhere from 2-6 Mohms is OK. For the crossover below, looking at the 2421 circuit, there are 3 spots where the 3Mohm resistors will be placed. To me it looks like they will be a kind of parallel circuit (but I honestly don't know how this measures within a crossover with caps and coils, etc., hence my question). If they are "acting" like a true parallel circuit, then their actual resistance would be 1 MOhm, based on how resistance is calculated in parallel. (this doesn't even include the other circuits with the many other 3Mohm resistors which would(?) lower the effect overall resistance even more?

[4313B]

It is easier to use the resistor and diode method G.T. switched to several years ago.

The diodes are 1N4935 and the resistors are 10 k ohm +- 10% 1/4 watt metal or carbon film.

This negates the use of batteries.

[jlwitherell]

It is easier to use the resistor and diode method G.T. switched to several years ago.

The diodes are 1N4935 and the resistors are 10 k ohm +- 10% 1/4 watt metal or carbon film.

This negates the use of batteries.

Whoa back the truck up! I haven't heard this before. Can you explain a little more? Where does the charging come from and how would these be connected??

[4313B]

Example:

[jlwitherell]

Thanks, forgive my limited knowledge. Is this right: The "R101" is the 10 k Ohm resistor which is 1/4 watt metal/carbon in series with the diode? where does the other terminal on the diode connect, what is the "A", which end of diode connects to resistor? Also, how does this charge the caps? LOL, sorry again, I have just enough electrical knowledge to be dangerous and thanks again for your help :)

[martin2395]

4313B, charge coupling with no 9V...what kind of sorcery is this? A=Amp or Particle Accelerator? :applaud:
I built my modules tonight, hope they aren't wrong :D Had to reinforce those rubbish pcb's with some epoxy glue.

The connection to the negative speaker terminal and to the capacitors is of course missing, it will be added after I get my component layout done.


http://i57.tinypic.com/2hmzbpw.jpg

http://i62.tinypic.com/15j7z9.jpg

Sorry, couldn't help myself with my old label maker :o:

[ivica]

Example:

Hi
May be some ideas from 4365 network would helpful.

regards
ivica

[martin2395]

I seem to miss the point of this solution. When we use a 9V battery we have a constant voltage on the cap but in the later design there is no constant voltage and the charge is dependent on the output level of the amp? :dont-know:

BTW, i used 3.3meg resistors and after each resistor the remaing voltage is around 2-2.2V (the battery itself measures 9.20V).
So the cap is actually only loaded with 2.15V, is this correct then?

[grumpy]

1) there is no battery to replace or corrode.

2) what is the input impedance of your test meter? ~1Mohm?

[jlwitherell]

Not sure that I'm sold on the diode method, if I wanted easy, I probably wouldn't be building these in the first place - not to mention I have to get the girlfriend to let me put these in the family room, now that ain't easy! ;)

This guy had some interesting points, and doesn't agree with the diode method (again, I NOT a crossover expert).

http://www.diyaudio.com/forums/multi-way/239952-charge-coupling-crossover-without-battery.html

[4313B]

This guy had some interesting points, and doesn't agree with the diode method (again, I NOT a crossover expert).

http://www.diyaudio.com/forums/multi-way/239952-charge-coupling-crossover-without-battery.htmlG.T. couldn't care less what that guy posts.

The cool thing about all this is that no one is locked into doing any of it. :) Use whichever method you prefer, or neither.

I'd personally go so far as to charge-couple the lone protection cap in the M2.

[jlwitherell]

G.T. couldn't care less what that guy posts.

The cool thing about all this is that no one is locked into doing any of it. :) Use whichever method you prefer, or neither.

I'd personally go so far as to charge-couple the lone protection cap in the M2.

I don't know what you mean by "lone protection cap in the M2," lol. I told you I don't know much ;) I take it you don't agree (with previous linked article) that using the rectifier to amp approach can cause noise issues without other filtering (or that it is insignificant)? I have no preference because I have no experience, but, I already have all the components for a fully CC'd network, so I prefer to stay committed to that. The vast majority of CC'd scenarios I've read about use the battery. If the diode/resistor is the best way I wonder why more people don't do it?? Or do they, and I just failed to see?

[4313B]

I don't know what you mean by "lone protection cap in the M2," lol.The M2 loudspeaker only has one capacitor (it is an active filtered system) and that is a protection capacitor between the driving amp and the compression driver.
I already have all the components for a fully CC'd network, so I prefer to stay committed to that.I can't imagine you being disappointed.

[jlwitherell]

Ok, another newbie question. Anyone have a good link to good 3mOhm resistors? I picked some up locally but the leads are hair thin and I'd like something a little more robust if possible. Martin's above appear to be beefier, but maybe it's just the pic?

[jlwitherell]

Cpl more pics.. Getting going on the divider network

[ivica]

Ok, another newbie question. Anyone have a good link to good 3mOhm resistors? I picked some up locally but the leads are hair thin and I'd like something a little more robust if possible. Martin's above appear to be beefier, but maybe it's just the pic?

Hi ,
Why so many wooden nuts for the binding post plane, and how do plan to mask them?

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=63474&stc=1&d=1414291543
ivica

[richluvsound]

The t-nuts are designed to go inside:) ?

Rich

[Odd]

I think the 3 Mohm you have is ok. There is no current through them.

[martin2395]

Exactly, my resistors are indeed beefier but in comparison I'm using 0.3mm2 wire with sillicone insulation because it's very supple.

My networks are more tricky to build as I don't have the correct cap values available in EU (At least, I can't find them).
So for example for my 2x36uF (I build 3155 networks) I have to use 4x18uF (2x parallel and then in series).

[jlwitherell]

Hi ,
Why so many wooden nuts for the binding post plane, and how do plan to mask them?
ivica

I was going for the industrial look? ;) Yeah, when drilling them I figured it may be overkill. Ah-well, if the worst mess up is having to unscrew/screw a couple extra bolts when needing to remove the plate, I'll call it a win.. Just going to paint over them.

[jlwitherell]

The t-nuts are designed to go inside:) ?

Rich

I know, but my plate is hard plastic and, although I didn't try, it seemed that it'd be too difficult to get them installed correctly into the material. I figure no biggy, just have to remove woofer to access, which I'd have to do anyway if I for some reason needed to remove the plate.

[jlwitherell]

I think the 3 Mohm you have is ok. There is no current through them.

Ok, thanks - I guess I'll run them! Thanks Odd.

[jlwitherell]

Exactly, my resistors are indeed beefier but in comparison I'm using 0.3mm2 wire with sillicone insulation because it's very supple.

My networks are more tricky to build as I don't have the correct cap values available in EU (At least, I can't find them).
So for example for my 2x36uF (I build 3155 networks) I have to use 4x18uF (2x parallel and then in series).

Thanks for clarifying. Man, that's a bummer, these networks are challenging and time consuming (and large) enough as it is!!

[martin2395]

It's because those are American coil/cap values :D

I bought Jatzen Crosscaps (nothing really fancy but good as a starting point) and they don't have the values like 36uF, 3.6uF or even 2uF.
Even the coils were actually a special order.

I decided to take the route - "Just follow the schematics, trust the one who designed it and it will be all good" ;)

[jlwitherell]

I decided to take the route - "Just follow the schematics, trust the one who designed it and it will be all good" ;)

I totally get it. I've read somewhere that "close counts" when it comes to cap/inductor values, but I'd do the same thing and just make it right :)

[jlwitherell]

Running into some confusion regarding the 2420 driver. Was ordering some radian replacement 8ohm diaphragms from parts express, when received they measure 3.9 and 4 oHm respectively. I do see that there are many drivers listed as 16 ohms on ebay, but which measure in the 6 to 8 ohm range, which is what I thought the 8 ohm diamphrams should measure. I am building giskards (I posted earlier in this thread) designed crossover and just wondering if these are the right diaphragms or not? All of my L-pads are new, and 8 Ohm. Thanks!

[Odd]

Running into some confusion regarding the 2420 driver. Was ordering some radian replacement 8ohm diaphragms from parts express, when received they measure 3.9 and 4 oHm respectively. I do see that there are many drivers listed as 16 ohms on ebay, but which measure in the 6 to 8 ohm range, which is what I thought the 8 ohm diamphrams should measure. I am building giskards (I posted earlier in this thread) designed crossover and just wondering if these are the right diaphragms or not? All of my L-pads are new, and 8 Ohm. Thanks!


You measure the DCR, the value is normal for 8 ohm driver.
Crossover is designed for 16 ohm driver. Can they be exchanged for 16 Ohm?

If to remove the 20 ohm resistance after the L-pad I think it will work with 8 ohm.

Maybe 4313B can explain.

[jlwitherell]

If to remove the 20 ohm resistance after the L-pad I think it will work with 8 ohm.

Maybe 4313B can explain.

That's what I was thinking, well, they're sending me ones that presumably read 8 ohms. But I guess I'm still not sure if this is correct for the crossover schematic and an 8 Ohm L-Pad (the crossover design does indicate 8 Ohm L-pad, but does that consider the diaphragm at 4 or 8 ohm??) :banghead:

[Odd]

You need to stop worrying so much.
Schematic is correct, many with a lot of knowledge, has built this before you successfully.

[jlwitherell]

Hahaha, you are right!!

[jlwitherell]

Well, well over a year later I finally found some time to finish these puppies up. Just got them up and running and sound great right out of the gate.

I need to figure the best way to test/tweek to get all levels dialed in including the port lenghts. I downloaded HOLMimpulse as a starting point for measurements. It's confusing and so far (just a couple hours) haven't had the best of luck. What software do you guys recommend? I bought the Dayton UMM-6 Microphone. I know this isn't the best system, but looking for a starting point. I may end up getting a pro in here...

Any gurus living in the Seattle area out there?? :) Cheers dudes and thanks again for the help!

[grumpy]

Very nice/clean build! :)

[jlwitherell]

Thanks Grumpy! So glad to have these out of the shop ;) Even happier to be listening to them!!

[JeffW]

You can check the port tuning with a frequency generator, an amp, and a multimeter. By slowly sweeping the frequency up and measuring the current through the woofer, you can detect the resonance frequency. There are how to tutorials online, if you can't find one I bet I can dig one up or somebody will.

[srm51555]

Try either method suggested here (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=388697&viewfull=1#post388697) by Sebackman or here (http://www.audioheritage.org/vbulletin/showthread.php?37659-Project-M2-DIY-Thread&p=388714&viewfull=1#post388714) by POS.

[johnlcnm]

Beautiful job man! I take it the crossover is biased? I did not read the whole thread. Anyway, I use Fuzzmeasure. It has the ability to use mic. cal files. Mine is the one that Mini DSP sells. This mic. comes with the cal. file. Not a plug here for the software, but it is easy and fast to use with a Mac.

Regards,

John

[jlwitherell]

Thank you guys for the recommendations and tips. Yes, crossover is biased...