MBOW1 3-Way Repair

[Rickster71]

I have so many folders and Favorites I didn't think I was going to find the link.
Check it out, interesting: http://www.troelsgravesen.dk/coils.htm

 

[Alex2507]

Speaker building OCD OTOH, if a tweeter is shot and you can't use them anyways, why not ship out the crossovers for a free rebuild while you wait for one to surface? If you're going to sit on your thumb and spin for awhile, might as well get something out of it. IMHO, FWIW, YMMV, IDGARAWYD

So you're going to pay for the parts and he's going to do the work ... knock yourselves out.
You don't need my permission for that. These crossovers aren't straight forward at all. The values I have on my boards don't line up with either of the schematics in the links I posted in reply to Kurt.

Something tells me these parts have already been reused once and aren't worth shipping to re-use again especially if the aim is making them pretty. I would never further disable these speakers to make prettier crossovers.

I'm waiting on word from Dennis about the real importance of matched pairs and maybe a lead to a lone tweeter.

The layouts should be/look identical.

The layouts on the ones YAA pays for and TLS builds will be.

I PM'ed Dennis. My hope is that he has an in on a lone tweeter for right now. That's what I need. While we're all here though, maybe he can provide an 'As Built' schematic for these or maybe a suggested direction for which tweeter high pass to use. These started out as a 2-Way and then got modified to be a 3-Way so the tweeter high pass is like the original 2-Way design I believe but in all likelihood it got changed somewhat ... so I don't know what I have. It's tough for me to take a xo board and see a schematic.

 

[Swerd]

I'm going to look through my Favorites. I have a nice link that shows how the value of a coil changes with regards to its orientation (I realize you already know that) and the proximity to other surfaces. (mostly metal)
Since those crossovers were such a mess, I was concerned a cap with a metal package would/could end up on top of a coil. That would have an affect on the coil's value. That's the only orientation/package that would interact.
Now, some of the values changes are subtle. So I don't know at what point it becomes audible. Let me know if you want it in a PM or I'll just post it here when I find it.
For Alex: (The layouts should be/look identical)

http://www.troelsgravesen.dk/coils.htm

Oh wait, you already posted it .

I just re-read that page, and he added some new info about what happens when a large aluminum plate is near the coil, and when caps are near the coil. That aluminum plate looks very big, and I don't understand why anyone would do that. MPP caps have a very thin layer of aluminum coating the poly film and the total mass of aluminum wouldn't amount to a fraction of 1% of that plate. The change to the coil's inductance due to a nearby cap are relatively small unless a large cap is sitting directly against the coil's hole.

 

[fuzz092888]

So you're going to pay for the parts and he's going to do the work ... knock yourselves out.
You don't need my permission for that.

Hmm, that's not how I read that, but then again I was only skimming. I read that as he was going to reuse the parts already there and just lay it out better, put it on a better piece of board, etc. If he's saying that you're paying for all new parts and he's just putting it together, then I think you'd be better off taking an East coast AH field trip where you hit Walter, Rick, me, Swerd, and end up at Dennis'.

 

[Swerd]

Dennis might have an OW1 sitting around. Depending on what is blown, it might be repaired with a new voice coil and dome assembly. Ask Dennis if he knows about that.

The US Hiquphon distributor is Dave Ellis.

Ellis Audio (by David Ellis)
9 Charley Lake Court North Oaks, MN 55127
phone: (651) 756-8097 - primary
cell: (612) 812-1797 - secondary
email: dave@ellisaudio.com
www: www.ellisaudio.com

I once thought matched drivers were of great importance, but if I recall Dennis said he didn't think it was major.

The MBOW1 3-ways that Alex bought were orginally built as 2-ways, and then converted to 3-ways. In the 2-way, the midwoofer has only a low pass filter plus some BSC. In the 3-way, it must have a band pass filter which includes many more parts. Dennis said he had to do some unusual work to use as many of the existing parts as possible, but I don't know any of the details.

I don't know where Dennis installed the XO boards, but the upper cabinet which houses the midrange and tweeter is small and has limited space. Any new board might have to pass through the hole made for the midwoofer. For someone to build new boards that actually fit, would probably require that they also have the cabinets.

 

[Haoleb]

I am confused here. Did you actually pay money for those speakers pre built? The entire wiring/crossover is probably the worst I have seen to date. A complete hack job at best. You do seriously risk blowing an amp with that crap stuffed back in there.

 

[TLS Guy]

So you're going to pay for the parts and he's going to do the work ... knock yourselves out.
You don't need my permission for that. These crossovers aren't straight forward at all. The values I have on my boards don't line up with either of the schematics in the links I posted in reply to Kurt.

Something tells me these parts have already been reused once and aren't worth shipping to re-use again especially if the aim is making them pretty. I would never further disable these speakers to make prettier crossovers.

I'm waiting on word from Dennis about the real importance of matched pairs and maybe a lead to a lone tweeter.



The layouts on the ones YAA pays for and TLS builds will be.

I PM'ed Dennis. My hope is that he has an in on a lone tweeter for right now. That's what I need. While we're all here though, maybe he can provide an 'As Built' schematic for these or maybe a suggested direction for which tweeter high pass to use. These started out as a 2-Way and then got modified to be a 3-Way so the tweeter high pass is like the original 2-Way design I believe but in all likelihood it got changed somewhat ... so I don't know what I have. It's tough for me to take a xo board and see a schematic.

Now we have finished the Christmas baking, I have had a closer look at this mess. First your crossovers are not suitable for your tweeter which is why you blew it. There is only one inductor on that board, and so this is a first order crossover. That is why you blew the tweeter.

There should be four inductors on that board and not one.

I would replace the tweeters with the current OW 1 those will work fine and are $252 per matched pair. After the abuse the working tweeter has had you need to replace both.

Those are only 3/4" domes with Fs 850 Hz, so for a first order filter the crossover would have to be 5 Khz or higher. The GR M130 need crossing over in the 2.5 KHz area. So a third order filter puts is down about 24 db at resonance which it should be. The bass mid crossover is 450 Hz.

As far as I can tell this is the current crossover for those speakers.

Low pass.

Band pass.

High pass.

As you can see the high pass filter is third order, which it would have to be at least.

The other slopes are second order basically.

The filter is complex however by the use of some resonant filters and resistor damping changing the Q of the filters.

This is the on axis frequency response.

Impedance curve.

Note impedance is 3 ohm from around 120 Hz to 250 Hz.

What drivers are you using?

The bass driver here is Peerless SLS 830668 10" woofer.

The Mid is the mid is the GR M130. Note that the mid is wired reverse polarity. This occurs frequently with second order three ways.

I can build these crossover for you if you wish. I do need to know what drivers you are using for mids and bass.

 

[Alex2507]

Hang tight, Mark. Let's first figure out what xo I have. It's been mentioned that my speakers started out as a 2-Way in which case this link would have my xo schematic. The problem is that the values on the resistors don't match. I'm headed to RS now for resistors. I'll fix up these. When we figure out what they are or what Dennis intended them to be I'll gladly take you up on your offer. Right now I'm off to RS for resistors.

This place has the OW1 tweeters for $219.

Haoleb, I did pay for these pre built.

 

[TLS Guy]

Hang tight, Mark. Let's first figure out what xo I have. It's been mentioned that my speakers started out as a 2-Way in which case this link would have my xo schematic. The problem is that the values on the resistors don't match. I'm headed to RS now for resistors. I'll fix up these. When we figure out what they are or what Dennis intended them to be I'll gladly take you up on your offer. Right now I'm off to RS for resistors.

This place has the OW1 tweeters for $219.

Haoleb, I did pay for these pre built.

I can tell you that you have crossovers that are no good. The first crossover is second order and has four inductors. It crosses over at 2.6 K. Personally I think that is pushing it for a 3/4" tweeter with an Fs of 850 Hz. The second crossover is said to be fourth order, but electrically it is third order.

I have no idea how your crossover was made into a three way, but that would have added a couple of inductors at least. I see only one inductor where there should be six. The crossovers I see in the pictures do not even make rudimentary sense. It is not a three way crossover. The bass driver is cut off I think first order, the bass is not cut off from the midrange but HF is and the HF filter is first order.

So I need to know exactly what drivers you have and then we can talk about crossover that make sense, not Kamikaze ones.

 

[Alex2507]

Mark, that's only the high pass for the tweeter in the link. The rest of the crossover is elsewhere. I have the GR Research mid and an unknown 10" woofer. There are two binding posts on the back of my cabinet. A full signal goes to my tweeter through that xo. A crossed signal goes to my mid for which the xo is elsewhere. I'll get you a snap shot of that later but that's not the xo that we've been looking at.

 

[TLS Guy]

Mark, that's only the high pass for the tweeter in the link. The rest of the crossover is elsewhere. I have the GR Research mid and an unknown 10" woofer. There are two binding posts on the back of my cabinet. A full signal goes to my tweeter through that xo. A crossed signal goes to my mid for which the xo is elsewhere. I'll get you a snap shot of that later but that's not the xo that we've been looking at.

Your tweeters are not the same version of the OW1. So you need a matched pair. You should buy the current 10" woofer, the original is NLA. They are good value, I think they are $56 each. Then I need to build you the three way crossovers I posted above. Then I think you will have an excellent reference system.

 

[Alex2507]

Your tweeters are not the same version of the OW1. So you need a matched pair.

It seems we once again have a difference of qualified opinions. Dennis isn't here yet but I do look forward to his input on this because of cost and I think we all benefit from informed discussion. The quote below from Richard is what has me wanting to hear more about this.

I once thought matched drivers were of great importance, but if I recall Dennis said he didn't think it was major.

These are my tweeters and these numbers at least do match, not that it does me any good because the first one in the pic is fried. I want to make sure we understand each other so bear with me and this story with pictures.




I'm not explaining my situation very well but I'm going to try harder.

You should buy the current 10" woofer, the original is NLA. They are good value, I think they are $56 each.

I already have this speaker system including 10" woofers.






The low pass and band pass portion of the xo lives in the base of the bass cabinet. Notice all the binding posts on the back? Here's how it works. A full signal goes into the lower binding posts on the bass cabinet. A crossed signal comes out of the posts right above them and goes to the GR Research M130 mid which is the lower set of binding posts on the bookshelf portion.

The top binding posts on the bookshelf get a full signal that goes into the high pass portion of the xo which is housed in the bookshelf and has been shown in pictures already. That high pass is the only thing I'm concerned with right now and as I've said, I will fix up the high pass filters that I have but would be happy to participate in a crossover comparison. We'll get to all that.

Then I need to build you the three way crossovers I posted above. Then I think you will have an excellent reference system.

I don't think the crossovers you posted above are what I currently have in place as my high pass has 2 caps and not the 3 your post has. Regarding the need for a 3-Way crossover I'll say again that I already have the low pass and band pass portion of the crossover here:



I thought it was cool that whoever built the cabinet used splines on the miters.



Right now I'm trying to draw out a schematic for the high pass filters that I do have just because it's a tough exercise for me and I want to make sure/see that I have all the wires going to the right places. Schematics are like road maps in a different dimension for me. Right now I'm waiting for Dennis to help me find a lone tweeter and maybe provide a set of 'As Builts' for the high pass filter.

Mark, thanks for being as patient with me. I'm doing my very best make sure that we understand each other. It turns out that going to Radio Shack was a fool's errand but today the real electronics store is open.

 

[TLS Guy]

That makes things a lot clearer. What were the numbers on the tweeters that did not match in the original pictures?

If that 10" woofer is the driver I noted, then the crossover is the one I posted. So you need one new tweeter. See if the importer will sell you one OW 1. It is still available.

Then all you need is neat properly made crossovers and you are set.

The inductor on that board should be 0.82 mh and yours is 1 mh.

The point is none of those crossovers are neat and properly constructed. We don't know if any is correct and the best thing to do is start all the crossovers from scratch. I would absolutely never connect any amp of mine to boards that looked like those.

 

[Alex2507]

What were the numbers on the tweeters that did not match in the original pictures?

Those are serial numbers.

If that 10" woofer is the driver I noted, then the crossover is the one I posted. So you need one new tweeter. See if the importer will sell you one OW 1. It is still available.

I just hand drew a schematic and my high pass filter isn't ANY of those but it bears a strong resemblance to this although the values don't line up 100%.

Then all you need is neat properly made crossovers and you are set. The inductor on that board should be 0.82 mh and yours is 1 mh.

I'm working on the high pass. Like I said, none of the values match.

The point is none of those crossovers are neat and properly constructed. We don't know if any is correct.

They worked and sounded good if that counts for anything. It's just to much money and to be honest, too much soldering for me to assemble the low and band pass xo portions from scratch. Right now I'm looking to swap out 5 resistors and make the board more orderly.

I'm off.

 

[lsiberian]

Wow that's the ugliest crossover I've seen. That reminds me of my single days.

 

[Rickster71]

Don't miss the great deal on these MBOW1's, they said.
You should buy them, they said.
It will be fun, they said.

 

[Alex2507]

Don't miss the great deal on these MBOW1's, they said.
You should buy them, they said.
It will be fun, they said.

It was the weekend special while the wife was out of town deal that was not to be missed. You've got me moving components and breaking leads. That link was just what I needed. Thanks for that. I guess I will have to post pic's of my work. That's a little daunting.

 

[Swerd]

Mark, thanks for being as patient with me. I'm doing my very best make sure that we understand each other.

There certainly has been some misunderstanding that led to some false conclusions here.

Right now I'm trying to draw out a schematic for the high pass filters that I do have just because it's a tough exercise for me and I want to make sure/see that I have all the wires going to the right places. Schematics are like road maps in a different dimension for me. Right now I'm waiting for Dennis to help me find a lone tweeter and maybe provide a set of 'As Builts' for the high pass filter.

Remember that crossover part values need not be precisely what computer-aided design software says it should be. A rough DIY rule-of-thumb has it that varying crossover parts by ±10% has little impact. In practice, I can usually find resistors and inductors (or modify them, see below) with the same values as specified in the design, but sometimes capacitors must vary a bit. For example, if a design calls for 7.9 µF and I can find 8.2 µF, it should be OK to use. (7.9 ± 0.79 = 7.1 to 8.7)

The inductor on that board should be 0.82 mh and yours is 1 mh.

It is certainly possible that Dennis had a 1 mH inductor, unwound and cut off enough wire to make it approximately 0.82 mH, but left the 1 mH label in place.

It seems we once again have a difference of qualified opinions. Dennis isn't here yet but I do look forward to his input on this because of cost and I think we all benefit from informed discussion. The quote below from Richard is what has me wanting to hear more about this.

"I once thought matched drivers were of great importance, but if I recall Dennis said he didn't think it was major."​

It could be that Dennis was not speaking of matched pairs of drivers in general, but was thinking of matched pairs of Hiquphon tweeters. Few if any other tweeters that I can think of are sold as matched pairs. It could be that Dennis meant that Hiquphon tweeters are so uniformly good that there is little difference between matched pairs and unmatched pairs.

 

[Swerd]

Here are more relevant examples:

Capacitor C2011 in the diagram is specified at 7.0 µF. Parts Express, Madisound, and Solen have 6.8 µF caps. It is OK to use one of them.

L2021, an inductor specified as 0.25 mH is accompanied by what looks like a resistor (R2021) with a small value of 0.5 ohm. This is probably the inherent DC resistance of the inductor. If you look up a 20 g 0.25 mH Jantzen inductor at Parts Express, its DC resistance is said to be 0.33 ohms. At Madisound a similar inductor is said to have 0.31 ohm DC resistance. Bingo, use one of those without a separate resistor for R2021.

I just hand drew a schematic and my high pass filter isn't ANY of those but it bears a strong resemblance to this although the values don't line up 100%.





I'm working on the high pass. Like I said, none of the values match.

 

[Alex2507]

I got some pic's to post but we also need to be clear that not only are my crossovers none of the above and beyond that they are not exactly like each other. I ended up taking a 9.2 Ohm resistor and raising it to 9.6 Ohms I think due to a broken lead. I'm not sweating that. Next I'm going to test them out.