M&K Sub Dying... - Blu-ray Forum

Xenomorph · 03-26-2010, 04:31 PM

I'm afraid my faithful M&K MX150 sub is on its last legs. Lately I've noticed a huge loss of power coming from this sub. The drivers are moving but not putting out the bass it once was.

I've taken the whole sub apart looking for any type of problem and found nothing.
It's not the receiver, I've tweaked everything I could..even cranked up the signal to the sub.
I've swapped cables.
Opened up the sub and checked the amp itself. No blown or swollen caps, no fried fuses, no loose wires. All wires inside and to the drivers are good.
Even swapped the drivers themselves out with a couple of Daytons. Nada.

This thing used to shake my house and now it's barely putting out anything.

One thing and this has been an ongoing thing for years, the gain knob on the back needs to be turned back and forth a bit sometimes. If it's in a certain spot (well, several spots actually) there will be no bass at all and you need to wiggle it a bit.
Could it be a bad pot? Would that be the source of all the problems? If it is I'll kill myself because I've been lugging that heavy thing back and forth for 2 weeks looking for the problem.

Any ideas would be very much appreciated!

kingofgrills · 03-26-2010, 06:01 PM

Xenomorph, I'm so sorry to hear that your M&K MX-150 is going out on you! I have a MX-125 Mk II, and it is nearly identical to yours. It's definitely worth it to get your sub back on its feet again.

I think your assessment of the pot going out on the speaker gain is probably right on. M&K subs don't fail too often, and that can be a known trouble spot. If you are comfortable and knowledgeable with electronics, you can try swapping out the gain knob yourself. Otherwise, I would find a local speaker repair shop that is familiar with working on M&K subs. Chances are it's the gain switch, and your drivers and amp are okay.

Good luck!

Xenomorph · 03-26-2010, 06:13 PM

I hope so. It can't be the drivers because I swapped them out with a couple of 12's I had laying around.

I just talked to Ken Kreisel and he gave me a site where I could buy a new 250 watt amp if it comes down to that. Hopefully not though.

I'll hit up Radio Shack today and try soldering in a new pot. Maybe I'll shoot some contact cleaner in there first.
It's always the easiest solution that I usually overlook.

Thanks!

Xenomorph · 03-26-2010, 11:27 PM

The plot thickens...
Contact cleaner got rid of the crackling and "dead spots" on the gain knob but there's still the original problem.
Funny, the drivers are moving in and out like crazy but there is no output. Almost like they're gasping for air.

kingofgrills · 03-27-2010, 12:03 AM

Quote:

Originally Posted by Xenomorph

The plot thickens...
Contact cleaner got rid of the crackling and "dead spots" on the gain knob but there's still the original problem.
Funny, the drivers are moving in and out like crazy but there is no output. Almost like they're gasping for air.

Exactly what drivers did you replace the stock ones with, and what is their Ohm rating? Are your stock drivers completely hashed, or can you reinsert them to see if there is any improvement? Also, would you please send me a link to the amp source Ken mentioned? I'd like to keep it handy in case either of my M&K amps need replacing.

BTW, how is Ken doing? Last I chatted with him he was looking to start speaker designing again. That was early 2008 though, I think.

Big Daddy · 03-27-2010, 02:11 AM

I had a similar problem with one of my DIY passive subwoofers. The driver was moving, but hardly any sound came out of it. The amplifier was a 20 year old heavily used Carver amp. I changed the amplifier and the subwoofer was back in business. I found a place that repairs Carver amps. I will probably send it out to be fixed as it was a very good amp.

crazyBLUE · 03-27-2010, 02:18 AM

Quote:

Originally Posted by Big Daddy

I had a similar problem with one of my DIY passive subwoofers. The driver was moving, but hardly any sound came out of it. The amplifier was a 20 year old heavily used Carver amp. I changed the amplifier and the subwoofer was back in business. I found a place that repairs Carver amps. I will probably send it out to be fixed as it was a very good amp.

I think you just wore that Carver out BD

Of course after that amount of time I am sure it more than served its purpose

Big Daddy · 03-27-2010, 03:10 AM

Quote:

Originally Posted by crazyBLUE

I think you just wore that Carver out BD

Of course after that amount of time I am sure it more than served its purpose

It will cost about $200 plus shipping for a complete overhaul of the amp. It may be worth it. This is the amp that Bob Carver designed to mimick the sound of a much more expensive Conrad-Johnson amplifier. He had quite a big dispute with the Stereophile magazine about 20+ years ago when he challenged the magazine that he could make his amplifiers sound like any overpriced amplifier recommended by Stereophile in less than a couple of hours. The case finally ended up in courts. As a result, you did not see any Carver ads or reviews in the Stereophile magzine. The bad blood may have carried over to Carver's new company, Sunfire.

crazyBLUE · 03-27-2010, 03:25 AM

Quote:

Originally Posted by Big Daddy

It will cost about $200 plus shipping for a complete overhaul of the amp. It may be worth it. This is the amp that Bob Carver designed to mimick the sound of a much more expensive Conrad-Johnson amplifier. He had quite a big dispute with the Stereophile magazine about 20+ years ago when he challenged the magazine that he could make his amplifiers sound like any overpriced amplifier recommended by Stereophile in less than a couple of hours. The case finally ended up in courts. As a result, you did not see any Carver ads or reviews in the Stereophile magzine. The bad blood may have carried over to Carver's new company, Sunfire.

An amp with that track record & background , More than deserves to be reborn at any cost I would think ! If it was that good for that long , A refurbish would have it going that long again

Xenomorph · 03-27-2010, 12:54 PM

Quote:

Originally Posted by kingofgrills

Also, would you please send me a link to the amp source Ken mentioned? I'd like to keep it handy in case either of my M&K amps need replacing.
BTW, how is Ken doing? Last I chatted with him he was looking to start speaker designing again. That was early 2008 though, I think.

Here's a link to the amps..
http://www.apexjr.com

Man, I tell ya. That guy has got to be the most dedicated person I've met. He answered all my stupid emails within minutes and was more than helpful. He's "restarted" his own company "Ken Kreisel Professional Sound".

http://www.kkprofessionalsound.com/index2.htm

BTW...found out what my problem was. I went over the amp again and found 2 broken solders under the board. Also had to reverse the wires on the bottom driver.
Resoldered, plugged it in and put in 2012 for a quick test. Between that and cleaning the contacts everything's perfect. Works great!
Like I said, it's always the simple solutions I tend to overlook.

Steve · 03-27-2010, 09:12 PM

Glad you got your sub back up and running, and at no cost too. Good job.

kingofgrills · 03-29-2010, 09:00 PM

Quote:

Originally Posted by Xenomorph

Here's a link to the amps..
http://www.apexjr.com

Man, I tell ya. That guy has got to be the most dedicated person I've met. He answered all my stupid emails within minutes and was more than helpful. He's "restarted" his own company "Ken Kreisel Professional Sound".

http://www.kkprofessionalsound.com/index2.htm

BTW...found out what my problem was. I went over the amp again and found 2 broken solders under the board. Also had to reverse the wires on the bottom driver.
Resoldered, plugged it in and put in 2012 for a quick test. Between that and cleaning the contacts everything's perfect. Works great!
Like I said, it's always the simple solutions I tend to overlook.

Xenomorph, I'm really glad to hear you got your sub working again. That's a big relief. BTW, what drivers did you use for replacements in it? Did you match the ohm ratings for the original drivers? Given the push/pull setup of the dual drivers, matching the ohm ratings will be crucial so you don't fry the amp.

I'm glad to hear you're back in business! And thank you for the links to Ken and the replacement amps!

Xenomorph · 03-31-2010, 08:33 PM

King..
I used 2 Dayton Titanic MK III's (recommended by Big Daddy in the sub repair sticky) and they sound great!
I think better than the M&K drivers. Much bigger magnets and better materials. And yes, they're both 4 ohm so no worries there.
I just need to break them in a bit.

kingofgrills · 03-31-2010, 09:35 PM

Good deal. I considered buying a couple of backup drivers when M&K liquidated before reforming, and I completely forgot about the ohm issue from having dual drivers. I almost bought two 8 ohm single drivers, designed for use with M&K's single driver subs, and that would have been an issue.

Have fun with your newly revamped M&K sub!

03-26-2010, 04:31 PM	#1
Xenomorph Active Member Member since:Feb 2009 Home Theater Gallery:3 Trading Score:1	M&K Sub Dying... I'm afraid my faithful M&K MX150 sub is on its last legs. Lately I've noticed a huge loss of power coming from this sub. The drivers are moving but not putting out the bass it once was. I've taken the whole sub apart looking for any type of problem and found nothing. It's not the receiver, I've tweaked everything I could..even cranked up the signal to the sub. I've swapped cables. Opened up the sub and checked the amp itself. No blown or swollen caps, no fried fuses, no loose wires. All wires inside and to the drivers are good. Even swapped the drivers themselves out with a couple of Daytons. Nada. This thing used to shake my house and now it's barely putting out anything. One thing and this has been an ongoing thing for years, the gain knob on the back needs to be turned back and forth a bit sometimes. If it's in a certain spot (well, several spots actually) there will be no bass at all and you need to wiggle it a bit. Could it be a bad pot? Would that be the source of all the problems? If it is I'll kill myself because I've been lugging that heavy thing back and forth for 2 weeks looking for the problem. Any ideas would be very much appreciated!

03-26-2010, 06:13 PM	#3
Xenomorph Active Member Member since:Feb 2009 Home Theater Gallery:3 Trading Score:1	I hope so. It can't be the drivers because I swapped them out with a couple of 12's I had laying around. I just talked to Ken Kreisel and he gave me a site where I could buy a new 250 watt amp if it comes down to that. Hopefully not though. I'll hit up Radio Shack today and try soldering in a new pot. Maybe I'll shoot some contact cleaner in there first. It's always the easiest solution that I usually overlook. Thanks! Last edited by Xenomorph; 03-26-2010 at 06:18 PM.

03-27-2010, 02:11 AM	#6
Big Daddy Blu-ray Champion Top ranked HT gallery Member since:Jan 2008 Location:Southern California Home Theater Gallery:79 Blu-ray collection:122 Trading Score:1	I had a similar problem with one of my DIY passive subwoofers. The driver was moving, but hardly any sound came out of it. The amplifier was a 20 year old heavily used Carver amp. I changed the amplifier and the subwoofer was back in business. I found a place that repairs Carver amps. I will probably send it out to be fixed as it was a very good amp. Last edited by Big Daddy; 03-27-2010 at 03:01 AM.

03-31-2010, 08:33 PM	#13
Xenomorph Active Member Member since:Feb 2009 Home Theater Gallery:3 Trading Score:1	King.. I used 2 Dayton Titanic MK III's (recommended by Big Daddy in the sub repair sticky) and they sound great! I think better than the M&K drivers. Much bigger magnets and better materials. And yes, they're both 4 ohm so no worries there. I just need to break them in a bit. Last edited by Xenomorph; 03-31-2010 at 08:36 PM.

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03-26-2010, 06:01 PM	#2
kingofgrills Blu-ray Guru Top ranked HT gallery Member since:Dec 2007 Location:PDX Home Theater Gallery:31 4K collection:5 Blu-ray collection:81 Trading Score:31	Xenomorph, I'm so sorry to hear that your M&K MX-150 is going out on you! I have a MX-125 Mk II, and it is nearly identical to yours. It's definitely worth it to get your sub back on its feet again. I think your assessment of the pot going out on the speaker gain is probably right on. M&K subs don't fail too often, and that can be a known trouble spot. If you are comfortable and knowledgeable with electronics, you can try swapping out the gain knob yourself. Otherwise, I would find a local speaker repair shop that is familiar with working on M&K subs. Chances are it's the gain switch, and your drivers and amp are okay. Good luck!

03-26-2010, 11:27 PM	#4
Xenomorph Active Member Member since:Feb 2009 Home Theater Gallery:3 Trading Score:1	The plot thickens... Contact cleaner got rid of the crackling and "dead spots" on the gain knob but there's still the original problem. Funny, the drivers are moving in and out like crazy but there is no output. Almost like they're gasping for air.

03-27-2010, 09:12 PM	#11
Steve Blu-ray Knight Top ranked HT gallery Top contributor Member since:May 2008 Location:Anna, TX 4K collection:128 Blu-ray collection:416 Trading Score:41	Glad you got your sub back up and running, and at no cost too. Good job.

03-31-2010, 09:35 PM	#14
kingofgrills Blu-ray Guru Top ranked HT gallery Member since:Dec 2007 Location:PDX Home Theater Gallery:31 4K collection:5 Blu-ray collection:81 Trading Score:31	Good deal. I considered buying a couple of backup drivers when M&K liquidated before reforming, and I completely forgot about the ohm issue from having dual drivers. I almost bought two 8 ohm single drivers, designed for use with M&K's single driver subs, and that would have been an issue. Have fun with your newly revamped M&K sub!

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