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Discussion Starter · #1 ·
Hello All,
I've a busted MK MX150 THX sub (plate amp gone) and have determined the drivers are in good shape. I've also a spare crown amp laying around (400w) and got to thinking:
After a unsuccessful search for a plate amp replacement I was going to throw the sub up on Ebay for parts and thought what have I got to loose by trying to gut the cabinet, keep the drivers and acoustic material and add speaker terminal posts and drive it with the external amp? Might be a fun project.

So, I understand the design is a push/pull and think I have to wire the drivers out of phase of each other and if memory serves me, would have to be wired in series (2 drivers 4ohm each) for a total of 8 ohms seen by the amp.

What is your opinion of trying this and would anyone be so kind as to give me a point (diagram) on how to actually wire it up.

Thanks.

Mike.
 

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You can wire the subs together in series for an 8 ohm load, or wire each sub to a channel of the amp for a 4 ohm load each. The subs are wired in phase with each other, not out of phase as far as I know.

You are going to need a hi-pass filter since the Crown amp doesn't have one, the Reckhorn B1 would be the cheapest solution.

http://creativesound.ca/details.php?model=B-1


Just out of curiosity, were the subs originally wired in series for an 8 ohm load?
 

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Discussion Starter · #5 ·
You can wire the subs together in series for an 8 ohm load, or wire each sub to a channel of the amp for a 4 ohm load each. The subs are wired in phase with each other, not out of phase as far as I know.
Understood on the wiring. Mike, not challenging your expertise but I thought when a push/pull configuration was used one of the 2 had to be out of phase with each other. Again, you are the expert here and I'm just trying to understand.

Also, if 2 channels of the amp were divided (1 for each driver in the cabinet) how would one set the levels on the amp? My question on that stems from trying to understand (in my mind) if both output levels were not exact how would the drivers react?


You are going to need a hi-pass filter since the Crown amp doesn't have one, the Reckhorn B1 would be the cheapest solution.
Would the receiver's x-over suffice for the HP filter?[/QUOTE]


http://creativesound.ca/details.php?model=B-1


Just out of curiosity, were the subs originally wired in series for an 8 ohm load?
Have not a clue on that question.
 

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Understood on the wiring. Mike, not challenging your expertise but I thought when a push/pull configuration was used one of the 2 had to be out of phase with each other. Again, you are the expert here and I'm just trying to understand.
I'm no expert on push/pull, I'll get Moonfly to drop in here as he is the resident guru with this.

Also, if 2 channels of the amp were divided (1 for each driver in the cabinet) how would one set the levels on the amp? My question on that stems from trying to understand (in my mind) if both output levels were not exact how would the drivers react?
The levels of each channel should be close enough as to not cause any problems with the subs.

Would the receiver's x-over suffice for the HP filter?
The receivers crossover is a low pass, you need a hi-pass to block the lower frequencies from causing the sub to bottom out. The original plate amp that came with the sub had one.

I'll guess that the original wiring of the subs was for 8 ohm load as there aren't to many 2 ohm stable plate amps out there. The original plate amp was 150 watts, The Bash 300 would be a good replacement amp and produce 150 watts if the subs are wired in series for a 8 ohm load.
 

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Discussion Starter · #7 ·
I'm no expert on push/pull, I'll get Moonfly to drop in here as he is the resident guru with this.
Thanks Mike.



The levels of each channel should be close enough as to not cause any problems with the subs.
Cool.



The receivers crossover is a low pass, you need a hi-pass to block the lower frequencies from causing the sub to bottom out. The original plate amp that came with the sub had one.

I'll guess that the original wiring of the subs was for 8 ohm load as there aren't to many 2 ohm stable plate amps out there. The original plate amp was 150 watts, The Bash 300 would be a good replacement amp and produce 150 watts if the subs are wired in series for a 8 ohm load.
Understood.
 

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If both of the cones fire out then you'd wire both drivers in phase electrically and acoustically.

If one driver is magnet out and the other is not then you need to wire the driver which is magnet out electrically out of phase so that they stay in phase acoustically.
 

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Discussion Starter · #9 ·
If both of the cones fire out then you'd wire both drivers in phase electrically and acoustically.

If one driver is magnet out and the other is not then you need to wire the driver which is magnet out electrically out of phase so that they stay in phase acoustically.

Thanks Ricci -
I think I've got it. To be sure:
when the plate amp is off, looking into the sub, I see the magnet of the driver that faces into the room. The other driver (cone) faces / fires into the cabinet and the magnet is exposed underneath the cabinet pointing at the ground. So, I will wire that driver electrically out of phase thus making the pair acoustically in phase.

Mike P.
I will call CSS today and purchase the Reckhorn B1. Also while I'm at it might as well get the Anti-Mode 8033.

Thanks to all - looking forward to doing this!

Mike.
 

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Hi guys,

I'll try be useful where I can here.

The wiring needs to be out of phase. When you wire the drivers electrically out of phase, they then operate mechanically in phase due to one driver being inverted to have its drivers face firing into the box.

Wiring, personally I prefer to wire in parallel. If you wire them in series the drivers will affect each other which I dont like the idea of, especially as the drivers used in the MK subs are fairly cheap and unremarkable ones. If the 2 ohm load is too much for your amp then you can wire them into a channel each assuming you dont want to wire in series. Another issue of wiring in series is that the 8 ohm load offers fewer watts, which could be an issue. To balance the channels perfectly, you would need a voltage meter connected to the speaker terminal on the amp, play the sub test tone, then adjust the gain for each channel accordingly so the reading for each matches.

I've never actually looked how M&K wire their drivers into their amps (series or parallel) so cant answer that question, but I run my own sub in parallel and find it works very well, so I have settled on this.

The issue you might have with this amp, and the implementation of a HPF, is that the M&K amps used an integrated Linkwitz Transform circit to eq the bottom end in. This was designed into the amps by Ken and nobody has the exact details of this. If you want to use your crown amp its going to be a bit of a suck it and see on the results front. Same goes on the HPF front, exactly if and how you would need to implement it would be a bit of trial and error.

I may however be able to go one better and help you out on the amp front here. This will remove any issues for HPF's, linkwitz boosts etc. The only issue you may have is that its not 400 watts, but bear this in mind, the only difference in the models throughout the MX range was the power supply to the amps. The increase supply allowed more watts from the amp and that was about it. This gives more max volume, but unless your in a very large room your not going to have an issue, even the lowly 125 watt models can fill pretty decent sized rooms well. Everything else within the range was the same, so there will be no issues at all using this amp. The linked amp is 250 watts, so you would expect probably something like a 2db drop in max output, which is pretty negligible. On the plus front, your replacing an MX150 amp which was originally only 150 watts (only the super rare and mighty MX 5100SF used a 400 watt amp), so your onto a winner really, and as I mentioned, the drivers and cab are perfectly fine with this amp.

Just to clear things up on driver wiring and operation, the below image should help illustrate how the drivers need to work, and why it is necessary to wire the drivers out of phase.

 

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Discussion Starter · #11 ·
The issue you might have with this amp, and the implementation of a HPF, is that the M&K amps used an integrated Linkwitz Transform circit to eq the bottom end in. This was designed into the amps by Ken and nobody has the exact details of this. If you want to use your crown amp its going to be a bit of a suck it and see on the results front. Same goes on the HPF front, exactly if and how you would need to implement it would be a bit of trial and error.
Moonfly - thanks for the reply! However based on Mike P. post above I've ordered the Reckhorn B1 to handle the HPF, Subsonic, etc. duties.

To balance the channels perfectly, you would need a voltage meter connected to the speaker terminal on the amp, play the sub test tone, then adjust the gain for each channel accordingly so the reading for each matches.
I think I understand you instruction however, If I to wire drivers in series (with bottom driver electrically out of phase) for 8 ohms I will not need to perform this voltage check / balance - correct?

The replacement amp you suggest looks good but this is getting way more $$ than I wanted to spend for this busted MK sub. I'd rather invest the $$ for a new SVS or venture into doing a diy from scratch.
 

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Moonfly - thanks for the reply! However based on Mike P. post above I've ordered the Reckhorn B1 to handle the HPF, Subsonic, etc. duties.
Shame, as the MK amp already has this on board.

I think I understand you instruction however, If I to wire drivers in series (with bottom driver electrically out of phase) for 8 ohms I will not need to perform this voltage check / balance - correct?

The replacement amp you suggest looks good but this is getting way more $$ than I wanted to spend for this busted MK sub. I'd rather invest the $$ for a new SVS or venture into doing a diy from scratch.
If you wire both drivers to a single speaker output you dont need to perform this test.

Not sure where your going on price though, that amp is about $140 by the looks of things, and you wouldnt have needed the HPF you have shelled out on :sneeky:. If you get it running right though, you'll find this busted M&K sub rocks :yes:

Anyways, I hope it works out for you and look forward to seeing the results :T
 

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I apologize for digging an old post up, but it directly relates to my situation so I assumed this was better than starting a new post. I'm in the same boat that mstailey was in with a broken MK MX-150 THX MkII sub. I took it to get serviced only to be informed that the company went under and there is no hope for replacement parts. As you can probably guess, I'm not "in the know" on the latest and greatest equipment nor am I a dedicated techy. I just enjoyed my sub and wish to repair it if possible.

In any case, while doing some searching I came up with mstailey's older post on this site where someone recommended the Dayton SA240 (PN# 300-804 at parts-express). Having not seen this post where moonfly recommends the amp from apexjr, I already ordered the Dayton and will be aiming to install it tomorrow.

I have three questions related to installing this amp:

1. As the amp only has one output channel, should I wire the push/pull drivers in serial or parallel?

2. In order to wire one of the drivers "out of phase" does that just mean wiring the positive wire to the negative terminal on one of the drivers?

3. In addition to replacing the plate amp, should I remove the other two boards that are screwed into the inside of the housing?

Sorry for the ignorant questions, I've done plenty of reading, I just want some confirmation before proceeding.

Thanks very much!

--
Chris
 

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Welcome to the Shack, Chris!

Since both subs are 4 ohm you'll have to wire the subs in series for a 8 ohm load as the Dayton amp won't handle a 2 ohm load form a parallel wiring. I'm not sure how to wire in series with one sub out of phase. I asked Dan to join in as he has experience with push/pull subs.

On the MK amp, is it one channel or two?
 

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Thanks for the welcome Mike!

I'm not sure how to tell if the MK amp has two channels. The main amp board has a nine pin connector on it with three wires coming from the two other boards I mentioned in addition to two sets of red/black wires each going to a driver.

Hopefully Dayton isn't know for producing garbage amps if it isn't able to handle a 2ohm load. But as I mentioned earlier, tinkering at this level of audio hardware isn't a daily occurrence for me so I just found someone else's recommendation and went with it. Please let me know if I should stop now and order a different amp as it looks as though I'm going to have to enlarge the main hole to allow for the Dayton. So, if it is a bad choice I'd rather not cut into my housing for it.

As for wiring it out of phase in serial, my thinking is that I would simply connect the red wire from the Dayton to the positive terminal of driver 1. Then connect the negative terminal of driver 1 to the negative terminal of driver 2. Then connect the black wire from the Dayton to the positive terminal of driver 2. Hopefully Dan can confirm this.

The other two boards that are mounted inside the sub contain some massive capacitors as well as a transformer. I was wondering whether I should leave them inside and just cut the wiring to them or remove them entirely when I replace the plate amp. By removing them, I'd be leaving 10+ screw holes in the housing and I'm not sure if that would somehow have any discernible effect on performance.

Thanks

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Chris
 

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Dayton amps are good, they're just not designed for a 2 ohm load, very few plate amps are.

I'd be leaving 10+ screw holes in the housing
If you mean the screw holes go through the cabinet panel then either leave the boards in or remove them and seal the holes.

Here's the proper series wiring for push/pull on a single channel amp:

Text Line Font Diagram Parallel


 
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