MBOWI 3-Way Phase and Measurement Question

[Alex2507]

You're talking about stuffing in the upper cabinet housing the mid range driver and tweeter of the MBOW1 3-way? And this particular cabinet was originally an MBOW1 2-way that was later converted to 3-way. Right?

It's my understanding that stuffing or lining a cabinet matters for bass performance. When Dennis said not to stuff the upper cabinet, he meant that what had been in the cabinet when it was a 2-way no longer applied once it was converted to a 3-way. Lining or stuffing doesn't have a major effect on the mid range driver because its high pass filter prevents it from doing any bass. I'm not sure if that means the cabinet interior should be left bare. I would guess that lining of some kind wouldn't hurt, and might benefit.

Do those separate sealed bass cabinets have poly stuffing?

The instruction to not stuff the bookshelf was for the MBOW1 2-way. Lining the cabinet is a different matter where he said to stay an inch back from the front baffle to allow for the mid woofer backwave ... or something like that. Lining=yes. Stuffing=no.

The sealed bass cabinets have corrugated foam, yellow fiberglass insulation, white fiberglass insulation, fluffy white non fiberglass fluff ... some peg board to shield the xo's from all that ... stuff.

I yanked the bp and lp from one bass cab yesterday. I can start comparing them to Dennis' schematic.

Before the drivers go back in, I'll have the bookshelves and bass cabinets lined and/or stuffed with materials of known acoustic properties.

 

[Alex2507]

Lining or stuffing doesn't have a major effect on the mid range driver because its high pass filter prevents it from doing any bass. I'm not sure if that means the cabinet interior should be left bare. I would guess that lining of some kind wouldn't hurt, and might benefit.

The bookshelf has foam on the walls backwards seemingly. Pictures will tell that tale.

Please correct me if I'm wrong about that being backwards with that plastic film not being against the walls.

Would it be okay to use 18 ga wire in the crossover?

I'm about to go fetch the 2nd lp and bp boards from my truck.

EDIT: Favorite Halloween costume in Salem:



Edit time is phenomenal. So I got the show and tell thing going now. I've been through these boards before to tighten things up, believe it or not. Now it's time to understand them and make them solid.

Here it is, splayed out, left to right.



Now in sections, the left:



The center with the addition of roach clip man. Just showing toys and coffee.



... and the right.



So I have this 18/2 power cord that's in a black jacket and rated 7 ways to sunday. Probably not in wall though. I also have some 10 ga stuff from an A/C or a stove. I could use that too. What did Verdinut say? In line DCR resistance was the big no-no? Maybe 14 ga in wall rated from 14/4 multi colored wire? That might be useful in my effort to 'see' the schematic when I look at the board.

Moral of the story? When you want it done right, ya gotta DIY ... or you could just pay someone.

 

[Swerd]

Please correct me if I'm wrong about that [cabinet lining] being backwards with that plastic film not being against the walls.

I think that's OK. I've never bought that type of cabinet lining and I forget it's name, but I believe it was meant to be installed that way.

Would it be okay to use 18 ga wire in the crossover?

Do you mean the wires inside the cabinet connecting the crossover boards to the drivers? Yes 18 ga is OK. When I first started building, I tried using 14 ga, and it was too difficult to solder to the much thinner leads of caps or resistors. It took forever to heat up. Now I use 16 or 18 ga. Short lengths of higher gauge wire are not a problem. When Verdinut talked about that, he meant the much longer wire in inductor coils should be lower gauge to avoid insertion (resistance) loss.

 

[Alex2507]

I believe it was meant to be installed that way.

The cabinets are both sealed so rigid fiberglass wouldn't be a problem and the NRC for any kind of FG is better than that of any kind of foam that I'm aware of. In my mind there is no way a layer of Saran Wrap on foam ... actually, for LF, backed rigid FG has better LF NRC's than the unfaced stuff. Hmmm ... knowing would be nice. Before I remove it, I'll look for any writing I can find on that stuff.

Photobucket had an update that has been putting them on and off line for the last two days. They're off line now.

When Verdinut talked about that, he meant the much longer wire in inductor coils should be lower gauge

I knew that! Plus the higher gauge makes the highs shimmer!

I printed out the schematics so I can just write 1 mH instead of trying to decipher and cross reference L2071 every time I see it. Oh, and Verdinut's terminal strips are a game changer for solder joints. I am going to make these boards sing before they even see a driver. <<< That's the coffee talking. Mocha Java from Whole Paycheck 'light' roast from 2 days ago. MOARRR !!!

 

[Alex2507]

Anybody know what this lining is?

 

[Swerd]

The cabinets are both sealed so rigid fiberglass wouldn't be a problem and the NRC for any kind of FG is better than that of any kind of foam that I'm aware of. In my mind there is no way a layer of Saran Wrap on foam ... actually, for LF, backed rigid FG has better LF NRC's than the unfaced stuff. Hmmm ... knowing would be nice. Before I remove it, I'll look for any writing I can find on that stuff.

There used to be several types of expensive cabinet linings. They're no longer sold and I don't remember their name. Maybe @Dennis Murphy can remember. Don't remove it before he chimes in.

Oh, and Verdinut's terminal strips are a game changer for solder joints.

How about a photo, and a link where to buy them?

I am going to make these boards sing before they even see a driver. <<< That's the coffee talking. Mocha Java from Whole Paycheck 'light' roast from 2 days ago. MOARRR !!!

. I had some left over Guatemalan mixed with some nice Ethiopian this morning. They were good together.

This Thanksgiving, I'm expecting a big crowd, 12 adults and 4 kids. Some will be staying at my house, and they're coffee drinkers, so I have to step up my coffee roasting to have enough. Normally I roast 4 lots at a time, 120 grams each lot. That lasts me & wife about 8 or 9 days. On Saturday, I roasted 5 lots, and next weekend I'll do 4 more. I hope that will be enough. I should go to Whole Paycheck and buy some decaff too.

I'm also planning to smoke a turkey, weather permitting. I've ordered a 20 lb. bird and will brine it in an apple cider brine flavored with oranges & ginger. Maybe I'll take photos and make a separate thread about this.

 

[Swerd]

That might be useful in my effort to 'see' the schematic when I look at the board.

What helps me is drawing a picture of the layout and wiring path. It doesn't have to be fancy, just a simple sketch showing parts layout and wiring. Keep correcting it as you change things. If I do that, it helps me remember the real layout as I get there from the schematic diagram.

 

[Alex2507]

How about a photo, and a link where to buy them?

I am getting it, slowly. My head hurts.

That's the lp, btw. I don't know where Verdinut bought 'em.

Edit: I've got about 100 of the 4 prong jobs. Let me know if you want up to 80 or so I suppose.

 

[Swerd]

Those look great. Thanks for the offer to send some. Right now, I'm not building anything. If I do want them, I'll let you know.

In your next photo (below), I see you have a large air core inductor standing on edge. When you're certain about where you want it, trim off some the plastic spool to make a flat side that keeps them from rolling. Heavy duty kitchen scissors easily cut that plastic.

That's one big cap, somewhere in size between a D battery and a Coke can. I like to use 8" cable ties to hold them down. Same with the inductors. I once bought a large plastic jar of several sizes of cable ties at Home Depot. I'm still working on it.

 

[Alex2507]

This is getting closer and it's a dry run, trial fit thing. I've had that yellow wire since Fla.

 

[Swerd]

Here are some photos showing examples of cable ties (the tweeter board of your MB27s),and of trimming the plastic bobbins on inductors (the MB 27 woofer board).

My photos are too large to directly upload. Go to this page and download the attached pdf files. Look in Part 2, page 9, photo 13 (tweeter board),and page 10 photo 14 (woofer board). Both photos 13 and 14 show how I use cable ties. No big surprises, but pictures always say it better than words. Photo 14 shows two inductors standing on edge, but it doesn't show the trimmed edges of the bobbins. Look on the 1st page in Part 3, photo 15 and see the trimmed edges of the black bobbin. I had to cut it so I could get it in through the opening in the cabinet brace.

 

[Alex2507]

Here are some photos showing examples of cable ties (the tweeter board of your MB27s),and of trimming the plastic bobbins on inductors (the MB 27 woofer board).

My photos are too large. Go to this page and download the attached pdf files. Look in Part 2, page 9, photo 13 (tweeter board),and page 10 photo 14 (woofer board). Photo 14 shows two inductors standing on edge, but it doesn't show the trimmed edges of the bobbins. Look on the 1st page in Part 3, photo 15 and see the trimmed edges of the black bobbin. I had to cut it so I could get it in through the opening in the cabinet brace.

I cut the bobbin. But look ...






I'll swap out that resistor for a 10 watt job All the leads have little bends at the terminal strip eyelets and of course plastic ties. Took forever, I never want to do this again.

 

[Swerd]

Took forever, I never want to do this again.

It gets much easier the 2nd time around. You've learned a number of ways that shouldn't be used again.

I see a lot cable ties – I love using them on crossover boards.

It looks like you had a number of caps & resistors with short leads, like you salvaged them from the original board. I like how you used those terminal strips to work with them. But it will be much easier with new parts that have longer leads.

I see you've learned the lesson about using peg board for crossovers. The holes are never where you need them.

I also see you used screws to hold down that big steel core inductor. Where they steel screws? It's not a big deal, but I get superstitious about altering the coil's magnetic field with screws that get magnetized. In the past, I've used nylon, brass, aluminum, or stainless steel screws because they don't get magnetized. That usually involved yet another trip to HD . Now I just use cable ties .

 

[Swerd]

The cabinets are both sealed so rigid fiberglass wouldn't be a problem and the NRC for any kind of FG is better than that of any kind of foam that I'm aware of. In my mind there is no way a layer of Saran Wrap on foam ... actually, for LF, backed rigid FG has better LF NRC's than the unfaced stuff. Hmmm ... knowing would be nice. Before I remove it, I'll look for any writing I can find on that stuff.

This morning, I remembered the name of that expensive type of speaker cabinet lining that you may have. It was called Black Hole. PE doesn't sell it anymore https://www.parts-express.com/black-hole-5-viscoelastic-damping-material-12x--268-886.

Search for 'Black Hole speaker damping' and read about it. I thought it was over-priced – not worth the expense.

 

[Alex2507]

I thought it was over-priced – not worth the expense.

Nothing is too good for my babies.

Thanks for saving me the trouble of yanking it out of there.

It looks like you had a number of caps & resistors with short leads, like you salvaged them from the original board. I like how you used those terminal strips to work with them.

I'm not reusing resistors. They're pretty baked. I put them in place to remind me that they go there. But yeah, the 100 mF cap was much easier to use with the strip. The Weller desoldering tool is pretty cool too but it's slow and for me there's a learning curve. However it does work.

I can't wait to get to the rest of it.

 

[Alex2507]

Capacitor question: If you need a 150 mfd cap and used two caps of 100 mfd and 50 mfh BUT the 100 mfd was rated for 250 volts and the 50 mfd was only rated for 100 volts ... I guess the question is, is that okay? PE says the 100 volt rating is good to 200 watts.

Edit: The 50 mfd cap is also an NPE cap. It's getting replaced probably by an Audyn Q4 47mfd rated for 400 volts. The Dayton 250 volt version is actually a little more money.

Edit II: This is the Bennic cap I am ditching in the 50 mfd position. There's one big 80 mfd cap on the board by Solen that is rated for 400 volts. The other two big 100 mfd caps are 250 volt but I figured making the replacement parts 400 volts for a small increase in cost and size wouldn't hurt anything.

I have the first bandpass apart and sort of layed out. Cleaning up the component leads is work. I think I'll take a couple of caps to the local electronics shop to verify values. There just wasn't a lot of lead to work with and what had been done to it before resulted in a huge amount of solder amounting to a huge cold joint. It was my defining moment as a man of solder. It should work and I wouldn't even be bothering but this stuff gets expensive quick. Anything that takes this much time ought to be free for f^%&s sake.

This edit thing is pretty terrific. My parts list is a done deal. < $85 w/ priority mail. The WT3 replacement is only another c-note AND it does capacitance and inductance readings. Wayyyyyyy under a hundred or practically $200.00 w/ the tester ...

I don't like being responsible. Now I'm running a little late for PT but I gotta say, I want this xo thing to be over. Cheryl said she would have thrown it out the window. I told her I couldn't live without it.

 

[Swerd]

Capacitor question: If you need a 150 mfd cap and used two caps of 100 mfd and 50 mfh BUT the 100 mfd was rated for 250 volts and the 50 mfd was only rated for 100 volts ... I guess the question is, is that okay? PE says the 100 volt rating is good to 200 watts.

Edit: The 50 mfd cap is also an NPE cap. It's getting replaced probably by an Audyn Q4 47mfd rated for 400 volts. The Dayton 250 volt version is actually a little more money.

Edit II: This is the Bennic cap I am ditching in the 50 mfd position. There's one big 80 mfd cap on the board by Solen that is rated for 400 volts. The other two big 100 mfd caps are 250 volt but I figured making the replacement parts 400 volts for a small increase in cost and size wouldn't hurt anything.

Is this for the 150 µF cap (C1021) in the woofer network diagram?

http://murphyblaster.com/content.php?f=MBOW1_3-WAY.html

You plan on keeping what ever 100 µF cap (250v rating) you now have, while you replace the NPE 50 µF (100v) with the Audyn 47 µF (400v) cap?

I don't see anything wrong with your plan.

 

[Swerd]

All the large value caps in that 3-way design can get pretty expensive. In the long run, its worth it.

 

[Alex2507]

Is this for the 150 µF cap (C1021) in the woofer network diagram?

The first post has the schematic for my xo's. This is my low pass filter.

.

All the large value caps in that 3-way design can get pretty expensive.

Luckily somebody else already paid for all that. A trip to our local electronics shop got me a meter for 50 bucks. It came with a free lesson in the form of a cap check. Even the $1.70 50 mfd NPE checked out but you want to knoe what really has me baffled. The 6 ohm resistor in between the 90 mfd and 150 mfd caps is more like 2 million Ohms. I have to move across 2 scales to read that resistor.

Because I'm lucky enough to have the old Peerless 10" driver, my xo schematics were very hard to find.

My local electronics guy had terminal strips from the 80's. They were a little different in that a 1/4" connector would fit on them. I bought 4 for 2 bucks a piece and crimp on heat shrink connectors for that fancy 10 ga I got. Oh, it's gonna be sexy.

BTW, Verinut, if you ever get back around, Madisound is selling 7 mfd Solen caps.

EDIT: In regards to that 6 Ohm resistor that blew in both boards, should I be using 2 resistors in parallel to get the value I want in order to have a greater power handling capability? It's concerning that they both blew. It might have been from the last thing we played on them at the GTG. Bella Fleck's Flight of the Cosmic Hippo, I believe. Dave had that huge Aragon 4004, I believe, driving a bass heavy tune.

Anyway, suggestions on what 2 resistors to use for a 6 Ohm sum would be appreciated.

 

[Swerd]

A trip to our local electronics shop got me a meter for 50 bucks. It came with a free lesson in the form of a cap check. Even the $1.70 50 mfd NPE checked out but you want to knoe what really has me baffled. The 6 ohm resistor in between the 90 mfd and 150 mfd caps is more like 2 million Ohms. I have to move across 2 scales to read that resistor.

EDIT: In regards to that 6 Ohm resistor that blew in both boards, should I be using 2 resistors in parallel to get the value I want in order to have a greater power handling capability? It's concerning that they both blew. It might have been from the last thing we played on them at the GTG. Bella Fleck's Flight of the Cosmic Hippo, I believe. Dave had that huge Aragon 4004, I believe, driving a bass heavy tune.

Anyway, suggestions on what 2 resistors to use for a 6 Ohm sum would be appreciated.

As you realized, any resistor that measures more like 2 million ohms instead of 6 ohms, is a blown resistor.

Usually a single 10 watt resistor is OK. But if you want to handle more power, use a 20 watt resistor or two 10 watt resistor in parallel. The power handling of two 10 watt resistors will be the sum, or 20 watts.

The total resistance of resistors in parallel, follow this rule:

The total resistance of resistors connected in parallel is the reciprocal of the sum of the reciprocals of the individual resistors. https://en.wikipedia.org/wiki/Series_and_parallel_circuits#Resistors_2​

1/Rtotal = (1/R1) + (1/R2) + … + (1/Rn), where n= the total number of resistors.​

​

If you have two resistors (R1 and R2) in parallel, it gets a bit simpler:​

Rtotal = (R1×R2) ÷ (R1 + R2)​

For N equal resistors in parallel, the reciprocal sum expression simplifies to:
1/Rtotal = N×1/R
which simplifies to:
Rtotal = R÷N

If Rtotal =6 and N = 2, R must be 12.

My local electronics guy had terminal strips from the 80's. They were a little different in that a 1/4" connector would fit on them. I bought 4 for 2 bucks a piece and crimp on heat shrink connectors for that fancy 10 ga I got. Oh, it's gonna be sexy.

Need photos when you're done or it didn't happen.