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2 MJ Acoustics reference 1 MK1

asdonk

Established Member
what can i suspect from 2 MJ subs both connected to the LFE signal
I want to get a better low end in my room
the room is about 13 x 5 m, so not a small room
2 subs should give a 3 db boost , but what about the phase , should it be the same on both subs
 

Steve.EX

Established Member
Might i offer that with a room of that size i believe the purchase of a 'more strident' subwoofer(s) as a definite train of thought.
 

asdonk

Established Member
yes i am about to replace the 2 rel storm 1 subs because of f their age
the MJ subs are brand new in the box, I have already heard one and they are
great
the rel stadium stays for stereo use, first i will try the 2 MJ subs, i good get them for the price off a Monolith , the monolith is also on my list
but maybe 2 smaller subs might be the solution to get a beter bass
 

AleXsr700

Established Member
I own a pair of MJ Acoustics Reference I mkII subwoofers and use them in my room (6x3.6m) and am quite happy with them.
However you are really using them in a huge room. Given the low price of around 600 quid each, maybe you should think about getting four of them as your room is really large.
Unless you are only using part of the room for your theater, I would say rather use more subs in order to get a better spread of the bass.

Unless of course you are planning on running the Stadium with the two MJs. Then I guess three subs, carefully placed in the room would be sufficient. Phase on all should be 90° if I am not mistaken.

However, if those subwoofers are/were new, they should be mkIII and NOT mkI. I bought mine two or so years ago and they are mkII. The current ones are mkIII. So check before you buy because as far as I know there have been quite some changes to the electronics and the quality.

P.S.: You can find all three mks on the website www.mjacoustics.co.uk and compare them. Quite significant improvements.
 

asdonk

Established Member
I know for sure that it is the MK1, it are old stock new in the box
I only use half the room for music and movies about 6 x 5 m with the system playng on the 5 m walls
but i want spl and diep bass, maybe the BK monolith will do the trick
but first i wil try the 2 MJ subs to get a better bass
 

AleXsr700

Established Member
Well, if possible I would prefer two subs to just one. And unless they are dead cheap (even more so than the new ones) I would go for newer mkII or mkIII rather than the really old mkI.
You are buying from new, so unless it's a huge difference in price, I would ask for factory new and not just unused for years.
 

asdonk

Established Member
new means factory new, but that is not the problem , when they do not work
in my set up I can sel them
I have heard 1 single MJ mk1 sub compared to a rel strata III and was very much impressed
the MK II only has 30 watt more power and 2 crossovers, but the same woofer and the same enclosure
 

AleXsr700

Established Member
asdonk said:
new means factory new, but that is not the problem , when they do not work
in my set up I can sel them
I have heard 1 single MJ mk1 sub compared to a rel strata III and was very much impressed
the MK II only has 30 watt more power and 2 crossovers, but the same woofer and the same enclosure
I am aware that by new you mean factory new :)

However I still feel that if you buy factory new, it should be the newest model and not one that has been outdated for three or so years.
But it is a question of the price I guess. e.g. if I was not a big HT fan and just wanted a subwoofer and could have the MJ mkI for 300 quid instead of the mkIII for 550-600, then I might go for the old mkI.
However, being seriously into HT I probably wouldn't go for the mkI. But TO ME, it all comes down to the price.

So, up to you to decide. As far as the differences are concerned, it might be worth it. For one, I would definitly want to be able to set high and low level frequency cut-offs independently, because if you are going to use the Hi-Level, you will most likely be cutting off at around 40-80Hz whereas the Lo-Level will be set to Pass-Through.
And you are gaining 130 Watts if you go for the current mkIII instead of the mkI. You will more than double the nominal wattage.
 

asdonk

Established Member
I get the MK I for 180 quid, so that is a good price, I have also sold my 2 8 and ten years old rel storm 1 subs, and wanted something new, as it is for the same money it is even more worth the try
I will cross the MJ subs at LFE so they get the whole frequence from 20 to 120 hz
the rel stadium is crossed at 30 hz , as my frontspeakers go down to 40 hz
and this goves the best results
tomorrow I will receive the 2 MJ subs and get on with the testings
 

asdonk

Established Member
today connected both MJ subs to LFE and dvd from U2 was playing, dts
fast and deep bass, with 25 hz playing in my room have done some playing with the phase settings and for now first the subs have to get played in
 

AleXsr700

Established Member
25Hz in your room? Testtones or do you just mean deep bass :)

Would be interested to hear about your findings on perfect settings etc.

As I own a pair of MJ Ref1 mkIIs I would also be curious as to whether you noticed any differences when changing the phase etc.
 

asdonk

Established Member
yep 25 hz with a cd with testtones on it, 25 hz was felt in my stomage
phase is set at 0 degrees for starting as it gives the best result
I started with phase at 90 , but as the rel stadium is also playing in DTS and DD mode and has phase on 0 degrees, these setting gave the best results
as i have 5m cables on each sub i will start moving the subs aroound to find the best position in the room
as you have 2 MJ MKII subs , how are they connected
only low level or do you use also high level connections
 

AleXsr700

Established Member
Hmm. The REL is downfire too, isn't it?
Normally all downfire subs would be set to around 90° as you are then in phase with the front-fire speakers you have.

My two are connected via QED subwoofer cable. One cable from preamp to sub A and then out of sub A into sub B.
 

asdonk

Established Member
the rel is downfiring, but can only be 0 or 180 o
in the manual it says that the setting to begin with is 90 o for the MJ sub
 

Nimby

Distinguished Member
damenace said:
Hmm. The REL is downfire too, isn't it?
Normally all downfire subs would be set to around 90° as you are then in phase with the front-fire speakers you have.

Unless I am mistaken phase is not affected by a 90 degree driver orientation.

The relative distance from the listener to the sub and from listener to the speakers affects phase. Not some arbitrary driver inclination.

0 degree is normal where the speakers and subwoofer are at the same radiius from the listener.
 

HiFiRuss71

Distinguished Member
damenace said:
Hmm. The REL is downfire too, isn't it?
Normally all downfire subs would be set to around 90° as you are then in phase with the front-fire speakers you have.
Sorry mate, that's not right.:lesson:

The phase effectively delays or advances the audio signal to ensure that the two waveforms, from your speakers and sub, arrive at the same time at your ears. This only affects the crossover region where both are reproducing the same signal concurrently. It is distance related and is there to adjust for when a sub is positioned at a different distance to you from the main speakers at it's simplest.

It helps if you think of a sound wave as an expanding sphere of air emanating from the driver equally in all directions. As it's bass we're interested in this is practically true. Whether the driver is turned through 90deg or not, the sound emanates from the same point at the same time - there's no change in the phase. If you have two sources of the same sound, with one further away, its phase will be behind that of the source in front - they're out of phase. If a forward firing sub is placed next to a speaker with the baffles level. Phase should theoretically be 0deg. If a downfiring sub was placed in the same position with the centre of it's baffle level with the speakers, it would still be at 0deg.

The phase is simply adjusted to where sounds in the crossover regions sound loudest, ie, there is the least cancellation. At 80Hz the wave length is 4.12m. for my sub to require 90deg of phase adjustment it would have to be 1.03m infront of the main speakers.Speed of sound (330m/sec) divided by frequency (80Hz)= wavelength (4.12m). 90deg = 1/4 cycle so 4.12m divided by 4 = 1.03m. If it were 1.03m behind, it would need 270deg advance of phase adjustment.

In my room the speakers are 4m away. If the sub was placed anywhere around me, even behind, as long as the distance was 4m, phase would still be 0deg. In reality, it's 1/4 of the way up my room against the left wall which places it about 0.6m closer. Phase is 15deg.

In practice, variables such as processing delays, crossover phase within the speakers and the refections of sound within the room itself can all have an effect on where the phase suits best. With an SPL meter and a CD of test tones and a bit of graph paper, try measuring the tones from say 60 to 100Hz adjusting the phase between each sweep. Wherever the highest overall volumes are, or the least dips, that's where your phase wants to be.

Sorry if that's a bit long winded (do I know another way?:rolleyes: ), but phase has very little to do with the orientation of the subs driver.

Nimby (God bless all who sail in him) will be along soon to poke holes in my maths, but I think we'll agree on principle. If not I'm about to learn something too.:)

Russell
 

AleXsr700

Established Member
Thanks for clearing this up for me.

But say, I have one subwoofer standing next to one of the front speakers. Say the driver of said sub is 30cm further to my right.
And my other subwoofer is still on the same wall but is 3m left of the left speaker.
How would I know where to set the phase? I mean, I can't just set phases and see which wave front comes in first. Especially not without help. But even with help, it would hardly be possible to hear.
So, to make it clearer, hopefully, in my room, how would I set the phases correctly?

myroomvz0.jpg
 

Nimby

Distinguished Member
I would move your subs to the positions shown.
(Apologies for the quick Paint room remodelling)

Any distance you can gain by moving everything bodily in the direction of the arrows would be beneficial.

If you could move the large wooden object (at top left) over to the wall to the right of the sofa you would gain much greater flexibility in the overall room arrangements. But there may be windows on this wall which make this impossible. Or you could swap places between the larger object and smaller object.

myroomvz0changeqo9.jpg
 

Nimby

Distinguished Member
Your image is much too large for the forum page format,
If you can delete it then a resized image of your original room layout appears below:

myroomvz0smallnp7.jpg
 

asdonk

Established Member
that looks almost the same as my subs are placed in the room
yesterday they where left and right next to my lcd screan
with both subs further moved into the room the bass is even better, although I still have made no measurements at all
 

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