Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Two subwoofers?

As you can see in my signature I have a G68/G98 system with analogue fronts and the rest Meridian speakers (DSP5000HC, DSP33, D1500). I have now accuired a Velodyne DD-12 subwoofer, and I want to try if the two subs can work together instead of the DD-12 replacing the D1500.

The system is placed assymetric in our 32 sqm (344 sqf) room, so two subs would come in handy. But the first question is of course this: 1) "Is this configuration - with G68, D1500 & DD-12 - possible?"

If so, there are other questions:

2) I can place the subs on the outside of each front speaker, that seems like the "default position". But the system will then be pretty "crammed" along a wall - between a corner and a door - so there will be no "find the best placement for each sub". So, what are the rules and strategies when trying to find another combination of spots for the two subs?

Here is a drawing (of how the room looked a couple of years ago...) which may help some:



The "Home Theater" is at the right part of the room. But where the scetch has just a "Plasma TV" marked it actually now looks something like this (but with carpets):



So, physically, there are just a few possible places for the subs. Up in the right corner is the D1500 currently placed. Up in the left part of the "Theater Area" there's a speaker to the right of the door, that speaker is in reality further to the right and leaves room (just) for the DD-12. Down right, there's room for a sub (especially the slightly smaller DD-12) either in the corner or between the plant and the easy chair (moving the plant more to the corner). Another possible place is down left in the Theater Area, between the DSP33 (which isn't pointed as in the scetch, btw) and the small table. Also it might be possible to have a sub to the right, between the easy chair and the terrace door.

3) OK, there are a few possible placements. I have an SPL and now also the Velodyne measurement system (which I have to learn) to help me. But apart from which spot to place them on, how about direction they should fase and their phase?

4) Normally, when you have a Meridian system and one or two Velodyne subs, you first run the room correction program for the Velodyne(s) and when it is adjusted MRC is next in line. Is there any difference to this when there's also a Meridian D1500 sub involved?

The good thing is that I'm the only one at home that really care about the difference between good sound quality and very good, so the sweetspot for the system can be quite small. The middle of the sofa. If I can get a bass dip to the left in the sofa, where my wife sits, it's a plus

Any help and suggestions are welcome.

From what I have seen in MConfig, there is only one possibility to connect both a D1500 and a DD-12. One of them will have to go as a mono "Front Centre" and the other as a mono "Rear Centre".

But I don't think that's too bad, is it? Is there really much benefit for subwoofers to be configured as a stereo pair?

With both subs as mono subs, I guess it's "just" to find the two spots acoustically best for them? They don't have to be placed in a "front centre" and "rear centre" position, might just as well be beside each front speaker?

An interesting question is of course this:

"If I configure my system with the DD-12 as an "Analogue Front Centre Subwoofer" and D1500 as a "Digital Rear Centre Subwoofer" - what restrictions for Bass Management to the two subs does exist?

I will look into that myself using MConfig, but I haven't used that much so I'm not 100% confident I don't miss something that's possible to do or misinterpret something the program tells me...

Well, having checked in MConfig the Front Centre can only get bass redirected from the three front speakers, the Rear Centre can only get bass redirected from the surrounds. But I guess both will also play the full LFE track?

My fronts are normally set as Large, they go comfortably down to 35Hz (but drops off pretty steep after that). Then I have the DSP5000 center and the DSP33 surrounds. What if I would set all speakers as Small, but the crossover as low as 50Hz (and then measure and try what seems most suitable)? Am I correct in thinking the crossover only affects Bass Management, not the LFE track (for LFE there's the "LFE low pass filter")? What could be a good frequency to start with for that filter? 80Hz? Is there any problem with having the Crossover and LFE lowpass at frequencies wide apart? Will eventual LFE material above the lowpass filter freq be "lost" - or distributed to other speakers in the system? But only if they are set as Large?

Or should the LFE lowpass filter be set to "Flat" for the DD-12? But not for the D1500?

No large interest in this subject, but if I insist then maybe someone will comment...

This is more how the Home Theater is placed right now. I have marked possible places for the two subs with red letters, A to G. At position G, the sub has to be further left than the letter indicates, saw that a bit too late...



Since I have one sub that is connected analogue (the Velodyne DD-12), and the D1500 that is connected digitally, I can't have the subs as a stereo pair. They should instead be a mono front sub and a mono rear sub.

Which sub should be the front sub? The DD-12 is the better sub that goes lower and outputs a higher SPL. So it ought to play "the most" bass. Usually a movie or multi-channel music mix has more bass at the front. Seems like the DD-12 should be the front centre sub. But my Bc Acoustique are large front speakers with good bass capacity, better than my DSP33 rears. So maybe the DD-12 is more needed at the back? I would guess at the front anyway, but that's just a guess.

Some possible combinations of sub spots are: "A + E", "B + G", "B + E" and "A + G" (I don't differentiate between D and E here). What do you think would be a good combination? All doors to the room are closed when the system is used, three of them are glass and one wood.

I also think a little about Bass Management, here's a picture from MConfig, it's easier when having a picture nearby. The settings are random, nothing I currently use:



The Crossover setting, does it only affect the sub, the frequency under which Bass Management should send bass meant for other speakers (when set to small) to the sub? Or is also the bass meant for the other speakers, lower than the crossover, removed from them? Or is the "Size" setting for the speaker when calibrating deciding this? So you can have an overlap of frequencies? Any correspondence between speaker "Size" and highpass frequency for that speaker? When to let frequencies overlap, and when not (to lessen available combinations)?

Velodyne says to use the crossover in the sub instead of the reciever, but possibly a G68 does a better job than the DD-12 with the crossover?

Should the best placement for the two subs be done totally independently, or should I first try to find the best spot for the D1500 (using the sweep generated by the DD-12, the mic and the frequency response display) and then let it play while searching for the best spot for the DD-12? And calibrating the DD-12?

Hi Tommy

It's certainly an interesting combination of analogue and digital you are trying to blend!

Mono front and rear subs is clearly the best way to go as two very different subs would probably not make very good stereo pairs. I would put my favorite sub at the front and base (no pun intended) my cross-over decision on what sounds best with this in conjunction with my front speakers. Then play around with the position of the second sub.

I may be wrong on this, but I seem to remember reading that when you set speakers as small there is no differentiation between the LFE and the 'other' bass in the rest of the channels.

I now have two subs but simply haven't got a convenient space for the smaller one so don't have your dilema.

Cliff

Hi Tommy,

Sorry I am not able to add any value to your sub query here, but, you definitely get the prize for "Best Looking Question"

Seriously, it's refreshing to see a question posed with as much info.

I would suggest that the best way to figure out your options is simply to test. When I previously ran a sub, it took quite a while to figure out the best placement and x/o. I imagine 2 subs will take time also as you'll be introducing interaction between subs as well as the rest of the room and kit.

Subs are probably not a strong suit for this forum IMHO, so, you may find help over on the AVForums

cheers

Well, just putting the question forth solves some of the issues - like my confusion above with the crossover and size. I believe the "Size" you get for a speaker when you calibrate correspons to a subsonic/highpass filter - the speaker shouldn't get frequencies below that. And I also guess there is just one crossover frequency, you don't want the sub and your other speakers overlap more than what you get at the slopes of the highpass/lowpass filters. A gentler slope would give some overlap, could help if you have a huge dip and set the crossover just there.

I do have set up systems with a sub before - but not two - but when it's once or twice in a few years you just look in the manual and then forget about it. And now I thought better ask first and maybe find out something I have missed.

One alternative would of cours be to have only the centre and surround speakers set to small and let the D1500 help the centre and the DD-12 help the surrounds. And both of course playing the LFE.

And yes, ncpl, of course the main solution is to test what sounds best and looks good on graphs - but I'm trying to minimize the avaliable variants before I send my wife away to visit a friend so I can play sweeps back and forth in the meantime without her needing to stay over night...

Well - I'm back...

This picture from Mconfig seems to indicate that if you have two subs as front centre and rear centre they handle the bass for "their" small speakers:



But in the manual they write "If you include two or more subwoofers in the layout, irrespective of the size of the main speakers the subwoofers will handle the bass and LFE for the system." Since they don't write "...will handle LFE and the bass for the small speakers in the system" and they talk about "irrespective of the size of the main speakers" they seem to mean that the subwoofers will play also the bass for the large speakers. Do you know what they mean?

I think I believe more in MConfig than the "Configuration Program Guide", or maybe it's just bad/ambigous wording in the manual...

Tommy, flip to the "Multichannel Movie" tab please

That's almost an identical twin...