M&K V-1250THX 125W Subwoofer Wanted!

[Techlord]

Just thought I'd stick my feet in the water to see if anyone knows who might want to sell me there M&K V-1250THX 125W subwoofer, all I really want is the amplifier plate and transformer mounted inside the enclosure.

Shoot me a PM!

 

[j_garcia]

Have you checked with M&K? They are back in business.

 

[TLS Guy]

Have you checked with M&K? They are back in business.

Yes, but they have nothing to do with the old M & K.

Those amps you are looking for are known for severe problems. I would not waste your money. If you want to keep the sub fit modify them and fit an amp from O Audio.

 

[Techlord]

Yes, but they have nothing to do with the old M & K.

Those amps you are looking for are known for severe problems. I would not waste your money. If you want to keep the sub fit modify them and fit an amp from O Audio.

The THX amps are well made in the USA and know many friends that are still running them after 10 years, M&K's amp are even better than the new ones being made in China. Ken kreisel has stated my times that the older M&K amp are far better than these new SB-1250 amps! Ken kreisel said I could even use the

Ken kreisel

Yes, the M&K USA amps were something special.

I would look for an M&K MX-150THX amp or MX-350THX amp.

Have you checked with M&K? They are back in business.

M&K and MKSound is not the same company, MKSound bought the rights to M&K's patent designs and is no longer a USA based company.

 

[TLS Guy]

The THX amps are well made in the USA and know many friends that are still running them after 10 years, M&K's amp are even better than the new ones being made in China. Ken kreisel has stated my times that the older M&K amp are far better than these new SB-1250 amps!




M&K and MKSound is not the same company, MKSound bought the rights to M&K's patent designs and is no longer a USA based company.

I can tell you I have fielded a lot of posts about those blown up amps. The O audio amps are the best OEM plate amps in the business. They are class A/B and not D. You can blow any speaker with just about anything if you put your mind to it.

I think your two best options are to get an external amp, or if you want a plate amp, the O audio will be your best bet and worth the trouble.

Your other option is to build or buy another subwoofer.

I just think buying an M & K amp on eBay would be a risky venture, and get you back in the same boat.

 

[Techlord]

I can tell you I have fielded a lot of posts about those blown up amps. The O audio amps are the best OEM plate amps in the business. They are class A/B and not D. You can blow any speaker with just about anything if you put your mind to it.

I think your two best options are to get an external amp, or if you want a plate amp, the O audio will be your best bet and worth the trouble.

Your other option is to build or buy another subwoofer.

I just think buying an M & K amp on eBay would be a risky venture, and get you back in the same boat.

How similar are these O Audio plate amplifiers crossover compared to the M&K THX amplifiers? It's the crossovers that determine whether or how well these amplifiers blend-in with my MKSound 950THX speakers. The newer SB-1250 non THX amplifiers crossovers have different rolloff and don't even use the same crossovers as the THX amplifiers which is why the don't blend-in as nicely.

 

[TLS Guy]

How similar are these O Audio plate amplifiers crossover compared to the M&K THX amplifiers? It's the crossovers that determine whether or how well these amplifiers blend-in with my MKSound 950THX speakers. The newer SB-1250 non THX amplifiers crossovers have different rolloff and don't even use the same crossovers as the THX amplifiers which is why the don't blend-in as nicely.

There should be no difference. The low pass filter on the O Audio is 40 to 120 Hz fourth order. There is also parametric Eq.

Now THX specs, which I assume the M & K follows, is low pass fourth order at 80 Hz and second order high pass.

If you use most receivers and set the crossover to 80 Hz that is also exactly what you will get. So if you have a modern receiver the sub crossover should not be an issue. But yes, you can get the O audio amp to conform to THX specs.

You should have no trouble with integration than you did with the M & K amp.

 

[Techlord]

There should be no difference. The low pass filter on the O Audio is 40 to 120 Hz fourth order. There is also parametric Eq.

Now THX specs, which I assume the M & K follows, is low pass fourth order at 80 Hz and second order high pass.

If you use most receivers and set the crossover to 80 Hz that is also exactly what you will get. So if you have a modern receiver the sub crossover should not be an issue. But yes, you can get the O audio amp to conform to THX specs.

You should have no trouble with integration than you did with the M & K amp.

I seriously considering the O Audio amplifiers, which amplifier would you recommend, the 500W or 300W version for my 125W M&K woofer? I'm told that just because the M&K amplifiers are rated at 250 watts that that wouldn't be a problem since those are RMS ratings, also would you say that the O Audio amplifiers crossovers give hard hitting fast bass?

I used to think hard hitting fast bass had to do with the woofer, now it appears to do more with the amplifiers crossovers. I have always used the same M&K 12" woofer with very different results using either of the M&K THX and non THX amplifiers which has my puzzled...? Would you also be able to explain why my SB-1250 250W amplifier lacks hard hitting bass when compared with either the older M&K THX amp and/or the O Audio amplifiers?

Thanks Techlord!

 

[TLS Guy]

I seriously considering the O Audio amplifiers, which amplifier would you recommend, the 500W or 300W version for my 125W M&K woofer? I'm told that just because the M&K amplifiers are rated at 250 watts that that wouldn't be a problem since those are RMS ratings, also would you say that the O Audio amplifiers crossovers give hard hitting fast bass?

I used to think hard hitting fast bass had to do with the woofer, now it appears to do more with the amplifiers crossovers. I have always used the same M&K 12" woofer with very different results using either of the M&K THX and non THX amplifiers which has my puzzled...? Would you also be able to explain why my SB-1250 250W amplifier lacks hard hitting bass when compared with either the older M&K THX amp and/or the O Audio amplifiers?

Thanks Techlord!

I don't think it matters which amp you go for, there is less than 3 db spl in it.

There is no such thing as fast bass. Fast requires a high frequency component which a sub can not have. Tightness of bass has to do with driver/box tuning and is a function of total Qt of the speaker system.

So one fourth order crossover should be a good as another.

To really get a drum transient correct requires a totally integrated speaker , with all the drivers lined up and built as a total design.

 

[Techlord]

I don't think it matters which amp you go for, there is less than 3 db spl in it.

There is no such thing as fast bass. Fast requires a high frequency component which a sub can not have. Tightness of bass has to do with driver/box tuning and is a function of total Qt of the speaker system.

So one fourth order crossover should be a good as another.

To really get a drum transient correct requires a totally integrated speaker , with all the drivers lined up and built as a total design.

Then why does my M&K subwoofer sound completely different with the same woofer, same enclosure but different amplifier? Mainly the M&K V-1250THX Certified and SB-1250 non THX amplifier are worlds (universes) apart when it comes to how the woofer sounds when it comes to bass reproduction! Until I understand this relationship I canot move forward! And people wonder why I keep asking for the M&K THX amps.

-Systemlord

 

[TLS Guy]

Then why does my M&K subwoofer sound completely different with the same woofer, same enclosure but different amplifier? Mainly the M&K V-1250THX Certified and SB-1250 non THX amplifier are worlds (universes) apart when it comes to how the woofer sounds when it comes to bass reproduction! Until I understand this relationship I canot move forward! And people wonder why I keep asking for the M&K THX amps.

-Systemlord

There are two possible explanations. The most likely is that the order of the crossovers are different. If it is a certified THX unit then the low pass crossover must be fourth order. What are the orders of the crossovers in the amps you are talking about?

So one fourth order crossover will be the same as another if properly designed.

The other explanation is that the amp with the poor bass was a poor device with a high internal resistance that changes Qt.

All I can say is that I see no reason what so ever, that you can not make your woofer work well with an O audio amp.

 

[TLS Guy]

I have confirmed that the crossover in your THX amp is fourth order LR as it should be and so is the O Audio, so it has to work.

I can't find the spec on the non THX amp, but that is really irrelevant.

 

[Techlord]

There are two possible explanations. The most likely is that the order of the crossovers are different. If it is a certified THX unit then the low pass crossover must be fourth order. What are the orders of the crossovers in the amps you are talking about?

So one fourth order crossover will be the same as another if properly designed.

The other explanation is that the amp with the poor bass was a poor device with a high internal resistance that changes Qt.

All I can say is that I see no reason what so ever, that you can not make your woofer work well with an O audio amp.

I never said that the SB-1250 was producing poor quality bass just that it does not blend with my speaker system, I will ask Ken which order crossover was used in the M&K V-1250THX amplifier.

SB-1250 250W amplifier specs:


Specifications: 250 watts RMS into 8 ohms @ .1% THD, 272 watts into 4 ohms @ 0.2% THD •

Signal to noise ratio: 101dB (A-weighted)
Auto on-off
0 - 180 Phase adjustment knob
Low Pass Filter 40 - 180 Hz and Bypass knob
Bass Level knob
Lo and Hi level inputs
High-Power Class AB Amplifier
Linkwitz-Riley 2nd order shelf
M & K Headroom Maximize Circuit (R)
6 Db bass boost

 

[TLS Guy]

I never said that the SB-1250 was producing poor quality bass just that it does not blend with my speaker system, I will ask Ken which order crossover was used in the M&K V-1250THX amplifier. If you want to go to MKSound and have a look at the SB-1250 spec do so as I will not install Adobe!

There is your reason right there. The non THX unit has a second order crossover with some odd unspecified shelf.

The THX unit is fourth order as it has to be to get THX certification.

Subs should have fourth order low pass crossovers period.

So you can use the O Audio unit with confidence.

 

[Techlord]

There is your reason right there. The non THX unit has a second order crossover with some odd unspecified shelf.

The THX unit is fourth order as it has to be to get THX certification.

Subs should have fourth order low pass crossovers period.

So you can use the O Audio unit with confidence.

Can you tell me how these second order and fourth order crossovers differ from one another as I know next to nothing about crossovers? My THX amp didn't even have a bypass, so I guess the receiver and THX amps crossovers were both active.

 

[TLS Guy]

Can you tell me how these second order and fourth order crossovers differ from one another as I know next to nothing about crossovers? My THX amp didn't even have a bypass, so I guess the receiver and THX amps crossovers were both active.

A second order crossover rolls off at 12 db per octave. A fourth order at 24 db per octave.

If you had your receiver and sub crossovers both set to the same crossover point then the crossover would have cascaded to make an eighth order crossover which would have had a large phase and time shift. Slope would have been 48db per octave.

If you have a modern receiver having a sub amp with a defeatable crossover is essential. You should not have to use the crossover in the sub in any event.

 

[Techlord]

A second order crossover rolls off at 12 db per octave. A fourth order at 24 db per octave.

If you had your receiver and sub crossovers both set to the same crossover point then the crossover would have cascaded to make an eighth order crossover which would have had a large phase and time shift. Slope would have been 48db per octave.

If you have a modern receiver having a sub amp with a defeatable crossover is essential. You should not have to use the crossover in the sub in any event.

When I first put this SB-1250 amp to use I noticed it stayed deep and sounded on the quiet side as far as how loud it would get to properly come up to the level of my satellites 80Hz - 20kHz crossover, does this rolls off at 12 db per octave have anything to do with this? In other words would the fourth order at 24 db per octave come up closer to the 80Hz - 20kHz crossover than the second order crossover would? My receiver has a "fixed" THX crossover that is not adjustable in anyway, yet worked flawlessly with my M&K THX amp that both came out the same year.

 

[TLS Guy]

When I first put this SB-1250 amp to use I noticed it stayed deep and sounded on the quiet side as far as how loud it would get to properly come up to the level of my satellites 80Hz - 20kHz crossover, does this rolls off at 12 db per octave have anything to do with this? In other words would the fourth order at 24 db per octave come up closer to the 80Hz - 20kHz crossover than the second order crossover would? My receiver has a "fixed" THX crossover that is not adjustable in anyway, yet worked flawlessly with my M&K THX amp that both came out the same year.

No it is the roll off after 80 Hz. 80 Hz will be the 3 db down point for both. So the second order crossover will be 15 db down at 160 Hz and the fourth order 27 db down at 160 Hz.

If your receiver has a fixed crossover point and is to THX specs it will have a 3 db point at 80 Hz.

If you cascade them your old, or the O audio, then you will be 6 db down at 80 Hz and 54 db down at 160 Hz. However the sub will be a whole wavelength and a half behind your mains at 80 Hz. Not a good plan.

I think that is about as far as we can go to educate you on a forum like this. If you want to know more you need some formal text books.

You will have to take my word for it, that the O audio will be a perfect replacement for the M & K THX unit.

I now consider the matter closed as anything else will be redundant.

 

[Techlord]

No it is the roll off after 80 Hz. 80 Hz will be the 3 db down point for both. So the second order crossover will be 15 db down at 160 Hz and the fourth order 27 db down at 160 Hz.

If your receiver has a fixed crossover point and is to THX specs it will have a 3 db point at 80 Hz.

If you cascade them your old, or the O audio, then you will be 6 db down at 80 Hz and 54 db down at 160 Hz. However the sub will be a whole wavelength and a half behind your mains at 80 Hz. Not a good plan.

I think that is about as far as we can go to educate you on a forum like this. If you want to know more you need some formal text books.

You will have to take my word for it, that the O audio will be a perfect replacement for the M & K THX unit.

I now consider the matter closed as anything else will be redundant.

I want to thank you for helping me find a replacement amp (getting the 300W version) for my subwoofer, I'm sure it will be as good or even better than the THX certified amps!

Thanks TLS Guy, Techlord!

 

[TLS Guy]

I want to thank you for helping me find a replacement amp (getting the 300W version) for my subwoofer, I'm sure it will be as good or even better than the THX certified amps!

Thanks TLS Guy, Techlord!

You are welcome. Please post pics of the mod to take the O Audio plate amp.