Today I was looking at the German ebay and found several advertisements for the subwoofer http://cgi.ebay.de/Aktiv-HIFI-MJ-Ja...ryZ96279QQssPageNameZWDVWQQrdZ1QQcmdZViewItem of the MJ-One sound system http://www.mj-one.com/. Normally I would not spend much time on such a system, but this one, at least, looks interesting, both technically (the incorporated functions), cost wise (36 euros, inclusive postage) and socially (the complete failure of peerless and tepax in selling this product) – look at this interesting link, telling about the great plans involved with this product, back in 2001 http://www.prnewswire.co.uk/cgi/news/release?id=63948 . My question is if someone here already opened such a cabinet, looked how it works, or have a technical diagram.
From what I understood it looks like a unit with three active crossovers and three small power amplifiers: one LP crossover for the lows and two HP crossovers for right and left satellite. My idea is to use one “MJ-one sound system” unit to power a DIY speaker: modify the crossovers somewhat, add some extra active EQ and level controls, and power a low cost, phoenix-clone speaker. This all to make a cheap, but hopefully still good speaker (not for my own use – I like valves – but as a gift for a less critic person, other would say: for an enemy).
First questions that arise: should I start to run?
Are there really three crossovers and amplifiers there? Can I use the amplifiers meant for NXT speakers for normal dynamic speakers?
Some points:
- The subwoofer unit is said to weight 6.5kgs…that’s next to nothing…and there is also a 'sub' included in this weight.
- It seems to be on sell just in Germany, a rapid glance at ebay.com did not turn out any result, neither did google point to anything else than Deutschland.
Well, I thank you all for the time spent reading this thread. I know it may sound silly after all, but I am curious!
Erik
From what I understood it looks like a unit with three active crossovers and three small power amplifiers: one LP crossover for the lows and two HP crossovers for right and left satellite. My idea is to use one “MJ-one sound system” unit to power a DIY speaker: modify the crossovers somewhat, add some extra active EQ and level controls, and power a low cost, phoenix-clone speaker. This all to make a cheap, but hopefully still good speaker (not for my own use – I like valves – but as a gift for a less critic person, other would say: for an enemy).
First questions that arise: should I start to run?
Are there really three crossovers and amplifiers there? Can I use the amplifiers meant for NXT speakers for normal dynamic speakers?
Some points:
- The subwoofer unit is said to weight 6.5kgs…that’s next to nothing…and there is also a 'sub' included in this weight.
- It seems to be on sell just in Germany, a rapid glance at ebay.com did not turn out any result, neither did google point to anything else than Deutschland.
Well, I thank you all for the time spent reading this thread. I know it may sound silly after all, but I am curious!
Erik
Hi,
I'd expect the the amplifiers to be fine with normal drivers, once you
identify the power amplifier IC, very likely will suit 8 ohm loading.
It has a switched mode supply, so no heavy transformer, and probably
a lightweight neobydium magnet in the subwoofer, hence the weight.
A simple full range open baffle could work well with it.
🙂/sreten.
I'd expect the the amplifiers to be fine with normal drivers, once you
identify the power amplifier IC, very likely will suit 8 ohm loading.
It has a switched mode supply, so no heavy transformer, and probably
a lightweight neobydium magnet in the subwoofer, hence the weight.
A simple full range open baffle could work well with it.
🙂/sreten.
Hi Sreten
Thanks for the useful information! I do not see this project coming up so soon, but I believe the MJ units will be around for a while, maybe even getting cheaper.
Erik
Thanks for the useful information! I do not see this project coming up so soon, but I believe the MJ units will be around for a while, maybe even getting cheaper.
Erik
Hi Sreten
What exactly do you mean?
What I wanted to say is that they will be available cheap on ebay.de for a while, as there is no one interested in them...or will they throw it into the garbage?
I am running to get my pair 😀
Erik
What exactly do you mean?
What I wanted to say is that they will be available cheap on ebay.de for a while, as there is no one interested in them...or will they throw it into the garbage?
I am running to get my pair 😀
Erik
ErikdeBest said:
Hi,
I meant don't wait around for them to get cheaper, they may dissapear.
So your going to get a pair ? Probably a very good idea as the c/o
frequency is likely quite high a a pair would work much better.
Would also allow the satellites to be bi-amped.
🙂/sreten.
Hi Erik,
I bought two of MJ one subwoofers two weeks ago and opened one to have a look inside. I'm also owning a Mission NXT set with the bandpass subwoofer and the models are quite different. But let me start with the biggest drawback of the MJ one subwoofer. The bass sounds distorted with a lot of overtones. It's a little bit like the sound of a small pocket radio playing together with the bass. I discovered this while I was testing the subbass without satellites. I think the problem is caused by the tight internal construction of the amp module. The power transformer is just 1 cm away from the amplifier board. The problem occured on both models that I tested. So it seems to be a design problem. Some of the noised is covered by the downfiring operation of the woofer. When I moved the transformer a little away from the amp board the hiss was lower. But let's switch to the good use. There is no switching power supply inside subwoofer. Instead you will find a beefy transformer (about 3 kg). The bass is powered by a LM3886 chip amp. The two other channels are driven by a smaller stereo chip amp (I have to look up the number).The speaker is a Peerless 6,5 inch paper cone driver with a plastified paper cone. So you get a lot of good parts for the money.
More info to come in my next message.
Best,
Bodo
I bought two of MJ one subwoofers two weeks ago and opened one to have a look inside. I'm also owning a Mission NXT set with the bandpass subwoofer and the models are quite different. But let me start with the biggest drawback of the MJ one subwoofer. The bass sounds distorted with a lot of overtones. It's a little bit like the sound of a small pocket radio playing together with the bass. I discovered this while I was testing the subbass without satellites. I think the problem is caused by the tight internal construction of the amp module. The power transformer is just 1 cm away from the amplifier board. The problem occured on both models that I tested. So it seems to be a design problem. Some of the noised is covered by the downfiring operation of the woofer. When I moved the transformer a little away from the amp board the hiss was lower. But let's switch to the good use. There is no switching power supply inside subwoofer. Instead you will find a beefy transformer (about 3 kg). The bass is powered by a LM3886 chip amp. The two other channels are driven by a smaller stereo chip amp (I have to look up the number).The speaker is a Peerless 6,5 inch paper cone driver with a plastified paper cone. So you get a lot of good parts for the money.
More info to come in my next message.
Best,
Bodo
Hi,
The pictures clearly show the mains input is 100 to 250V, 50 Hz to 60Hz.
This means it has a switching supply, so it can't be the same model.
🙂/sreten.
The pictures clearly show the mains input is 100 to 250V, 50 Hz to 60Hz.
This means it has a switching supply, so it can't be the same model.
🙂/sreten.
Hi,
Sorry I missed the voltage selector switch on the back, so its not a switched supply.
May be possible to add a copper belly band to the transformer ?
Or a shielding plate ?
🙂/sreten.
Sorry I missed the voltage selector switch on the back, so its not a switched supply.
May be possible to add a copper belly band to the transformer ?
Or a shielding plate ?
🙂/sreten.
Hi Sreten and Bodo
So maybe I should get a pair soon.
Thanks for jumping in Bodo, with your information I get more excited about using this unit for a low cost dipole speaker I am planning for a friend. I am curious about further information you can give, but here already two questions...is the crossover part built with thru hole components? That would make modification of XO frequencies easier (but I am afraid it is SMD). And is there any chance that the 6,5" 'subwoofer' unit is a known peerless unit, with parameters easily available?
Many thanks
Erik
So maybe I should get a pair soon.
Thanks for jumping in Bodo, with your information I get more excited about using this unit for a low cost dipole speaker I am planning for a friend. I am curious about further information you can give, but here already two questions...is the crossover part built with thru hole components? That would make modification of XO frequencies easier (but I am afraid it is SMD). And is there any chance that the 6,5" 'subwoofer' unit is a known peerless unit, with parameters easily available?
Many thanks
Erik
Hi Erik,
here comes the promised update. The stereo chip amp is a LM4766. The active crossover is complete build with SMD parts. I tried to identify the chips, but the letters on the chip are barely visible. Peerless part number of the "subwoofer" is 830608. Impedance is 4 Ohm. A few minutes ago I made another distortion test. Unfortunately the distortion seems not to be caused by the mounting position of the transformer. So I was wrong in my first message.
cannotbe Currently I have no time solving the distortion problem. I think the best idea would be to build your own x-over and just use the power amp part, transformer and loudspeaker. The power supply can also be reused feeding the chip amps and the crossover. If you want I can send you some pictures of the ingredients of subwoofer.
Best,
Bodo
here comes the promised update. The stereo chip amp is a LM4766. The active crossover is complete build with SMD parts. I tried to identify the chips, but the letters on the chip are barely visible. Peerless part number of the "subwoofer" is 830608. Impedance is 4 Ohm. A few minutes ago I made another distortion test. Unfortunately the distortion seems not to be caused by the mounting position of the transformer. So I was wrong in my first message.
cannotbe Currently I have no time solving the distortion problem. I think the best idea would be to build your own x-over and just use the power amp part, transformer and loudspeaker. The power supply can also be reused feeding the chip amps and the crossover. If you want I can send you some pictures of the ingredients of subwoofer.
Best,
Bodo
Hi,
from here :
http://www.audiofil.net/forum/forum_posts.asp?TID=6523&PID=147236
🙂/sreten.
An externally hosted image should be here but it was not working when we last tested it.
from here :
http://www.audiofil.net/forum/forum_posts.asp?TID=6523&PID=147236
🙂/sreten.
Hi
To complete the dissection, I found some pictures of the 'sub'woofer:
http://www.steintrikes.com/audio/peerless830608_01.jpg
http://www.steintrikes.com/audio/peerless830608_02.jpg
http://www.steintrikes.com/audio/peerless830608_03.jpg
Sad that the crossover is SMD, but well, the rest of the parts together are surely worth the money. Just have to add the crossover and EQ. Something like this http://home.comcast.net/~dreite/Davey/Davey.htm or SL's Phoenix - and some extra speakers.
Bodo, I thank you for the offer for more photos, but I believe that the pictures here show all. Or is there something interesting that I am still missing?
Erik
To complete the dissection, I found some pictures of the 'sub'woofer:
http://www.steintrikes.com/audio/peerless830608_01.jpg
http://www.steintrikes.com/audio/peerless830608_02.jpg
http://www.steintrikes.com/audio/peerless830608_03.jpg
Sad that the crossover is SMD, but well, the rest of the parts together are surely worth the money. Just have to add the crossover and EQ. Something like this http://home.comcast.net/~dreite/Davey/Davey.htm or SL's Phoenix - and some extra speakers.
Bodo, I thank you for the offer for more photos, but I believe that the pictures here show all. Or is there something interesting that I am still missing?
Erik
Hi,
I think the published pictures show all important parts of the subwoofer. So instead of uploading additional additional pictures I will try to get the names of the SMD-opamps.
Bodo
I think the published pictures show all important parts of the subwoofer. So instead of uploading additional additional pictures I will try to get the names of the SMD-opamps.
Bodo
I bought two units! They were delivered to my sister in law's place (Aachen, Germany)... I will have to wait until Carnaval to pick them up, but, no problem, I have some other projects going on (probably could wait until the carnaval of 2020 if I had to conclude all my ongoing projects before starting on this one).
The first "peerless midrange units" are popping up at ebay.de. The guy promised he could make a datablatt of the units, lets see if he does it!
http://cgi.ebay.de/PEERLESS-160mm-6...categoryZ141261QQtcZphotoQQrdZ1QQcmdZViewItem
Erik
The first "peerless midrange units" are popping up at ebay.de. The guy promised he could make a datablatt of the units, lets see if he does it!
http://cgi.ebay.de/PEERLESS-160mm-6...categoryZ141261QQtcZphotoQQrdZ1QQcmdZViewItem
Erik
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