Basic question about sub integration

[David100]

I have a 2 channel system, with a 2 channel pre-amp (from Plinius), 2 channel amp (also Plinius) and ML Summits.

I read that some people are adding a sub in the system. I am considering this from time to time because my room is quite big and a sub might help the Summits to compress the air...

So, Is this possible to add a sub in a 2 channel system without having to change the preamp ? And if yes, how ? Or would I have to buy a multi-channel preamp ?

Thanks a lot for your answers to this very basic question.

 

[twich54]

So, Is this possible to add a sub in a 2 channel system without having to change the preamp ? .

Yep, depending on the output configuration of your 'pre' ....... if you have a secound pair of 'main outs' run a L/R pair to your subs inputs, if not a Y or 'splitter'(if you will) cable. Basically your sub is being fed the same signal as your amplifier.

You then make crossover / slope adj @ your sub, along with room EQing, etc.

BTW, I'm assuming your running a 'powerd sub'

 

[adanny]

I have a 2 channel system, with a 2 channel pre-amp (from Plinius), 2 channel amp (also Plinius) and ML Summits.

I read that some people are adding a sub in the system. I am considering this from time to time because my room is quite big and a sub might help the Summits to compress the air...

So, Is this possible to add a sub in a 2 channel system without having to change the preamp ? And if yes, how ? Or would I have to buy a multi-channel preamp ?

Thanks a lot for your answers to this very basic question.

I am considering exactly the same thing for my Summits but am also of two minds. I have a 2-channel and a 7.1 channel system in the same (family)room, with a pre-amp for the 2 channel and a HT processor for the 7.1 channel. All other components are shared. I narrowed my choices down to a "How to connect" decision and a "what to buy" decision - and turns out they are linked. I also decided that if I am adding a sub, I will add two. Why settle for one when you can get two for twice the money :music: And 2 subs help reduce unwanted peaks and trough. So here is my summary:
1. If I buy ML descent i's, they have a built in high pass crossover as well as RCA out jacks for your main (Summit) speakers. That means you can run your current pre-amp outs into the Descents, pick a high pass crossover frequency on your sub controls, and connect the RCA outs to the amps that are driving your Summits. This is the easiest connection. It also has the added advantage that you can run your Summits full range or crossed over and experiment with that. The descent will allow you to choose a high pass crossover at 40 Hz or 70 Hz which are probably the only frequencies you would experiement with for the Summits anyway.
2. If I buy JL Audio f113 fathom subs, they DO NOT have a built in high pass or out jacks for the main speakers. That means if you want to experiement with running the Summits full range or not, you would have to buy an active external crossover (for me, probably a Marchand but not sure yet...) . The crossover would go between your preamp and amp/subs, splitting the pre-amp signal into a high-pass that goes to your Summit amps and a low-pass that goes to your subs. If you are 100% convinced that you will run the Summits full range, you can either split the outs on your pre-amp with a Y-connector, or your pre-amp might have more than one set of outs e.g. RCA and XLR or multiple RCAs

hope that helps. let me know what you decide. I thought I was convinced that I would buy the fathoms but haven't pulled the trigger yet, and still haven't decided firmly on what crossover I would get...

cheers
adanny

 

[David100]

Hello Dave,

Thanks for your answer - Indeed it seems it can be much simpler than I had initially expected - Good news for me ) Your post helps a lot so start to understand the options - thanks a lot.

Hello Adanny,

Just after having initiate this thread, I saw yours a few lines below. They were so similar I thought about removing mine - but then I kept it in place because my question was even more basic. With the answer of Dave and yours, I now completely understand the options.

I read the JL Audio f113 are very good indeed. But I had not noticed that they had no high pass / jack out to filter the summits.

So, I have a new very basic question : Is a crossover really necessary for using a sub. Is it a problem to feed directly the sub from the preamp (with the second audio outs) and play the summit full range (directly from the main amp) ? Or do I really have to integrate a cross-over to prevent the summit from playing below a given frequency. Would the sound be more dirty with the summits playing full range combined with the subs ? Or not ?

Thanks

David

 

[adanny]

Hello Dave,


I read the JL Audio f113 are very good indeed. But I had not noticed that they had no high pass / jack out to filter the summits.

So, I have a new very basic question : Is a crossover really necessary for using a sub. Is it a problem to feed directly the sub from the preamp (with the second audio outs) and play the summit full range (directly from the main amp) ? Or do I really have to integrate a cross-over to prevent the summit from playing below a given frequency. Would the sound be more dirty with the summits playing full range combined with the subs ? Or not ?

Thanks

David

For connections, learning a bit more etc, I always find it helpful to read the owner's manual of whatever I am considering buying. I tried to attach the descent and fathom owner's manuals to my post above, but they turned out to larger than forum rules. You will find the manuals here...
http://www.martinlogan.com/products/descenti
http://home.jlaudio.com/products_subs.php?prod_id=371

In answer to you second question, i think the jury is divided. Crossing over typically makes sense for one of three reasons....
1. It reduces the load on your amp since the amp will only have to amplify signal above the crosser frequency, and the low frequencies demand a lot of power.
2. The quality of the woofer in a sub will likely be better than that of a full range speaker
3. At the lower end of the range of the main speaker, the bass is likely to be muddied

For Summits, the first two reasons almost certainly dont even apply. First, the woofers in the summit are self powered by 2x200w amps/ch, and are not drawing any power from your amp anyway. Second, the woofers are very high quality 10" aluminum cone drivers which I would wager are nearly identical to those in the descent (which has 3 10" aluminum cones, although in a totally different geometry. Actually, I would be very curious to know from someone in this forum if they know for a fact whether the Summit cones are the same, similar or different from the Descent i cones??

So the only reason to crossover the Summits would be reason 3 above. Folks on this forum have experimented with both. One of the regular posters (I forget who...) is convinced that the sound is more clean when they crossover the Summits (I think at 40 Hz but not sure...I think they own a Marchand crossover...). Some older posts discuss this theme although not directly or in much detail. What is for certain is that it will be highly room dependent.

If I buy the descents (which I am leaning against), I can experiment and decide what is best for my room. if I buy the fathoms, I will probably buy a crossover but mostly from a desire to fiddle In theory, running the Summits full range should be fine for the following reason:
a. They are very, very high quality woofers
b. More subwoofers in a room reduce peaks and troughs (provided the different subwoofers are identical/similar in quality) so running full range might actually help
c. You can always use the 25 and 50 Hz controls on each Summit to at least dial back 2 important bass frequncies

Long way of saying you should be fine NOT crossing over and just connecting the subs directly to your preamp. You can always experiment with a crossover later. I am in a loquacious saturday morning mood so you got the long essay for a short answer..

 

[twich54]

So, I have a new very basic question : Is a crossover really necessary for using a sub.

Nope, assuming your talking external

Is it a problem to feed directly the sub from the preamp (with the second audio outs) and play the summit full range (directly from the main amp) ?

Again...nope, that is exactly how I integrate my Spire / sub combination.

Now , here's my explanation David.........first off your Summitts are blessed with two level controls (25&50Hz) which can be used to 'blend the mix' , this combined with a quality room Eq software (SMS for example, there's others of course) will then allow you to get as flat a response as possible given your rooms acoustic signature.

Now with this being said I'll go out on a limb and say you probably don't need your sub to perform beyond the first octave. FWIW and IMO, it's best to bring ones sub in at the point where your Summitts begin to roll off. My rule of thumb is the higher freq that the sub is 'cut in' the higher the cooresponding slope (basically the more the sub is asked to do the quicker you want to get it out of the way !)

FWIW, with my set up the sub is integrated @ 65Hz with a 24db slope.

David, hopefully some of our other resident sub / room Eq experts (JonFo , DTB300) will chime in here as well.

 

[David100]

Thanks again Dave and Adanny,
It becomes clear now. My Plinius M8 pre-amp does not have two completely separate audio outs, but I have RCA and XLR. So I will continue to feed the main amp with the XLR and use RCA for the sub. I still have to check if If the pre-amp allows that (use both XLR and RCA outs) - The user guide says nothing about that.

But, when it comes to Electronic room control / Equalizers I prefer not to use that kind of devise - I prefer to keep the sound the more transparent as I can.

When you add salt to your dish, you not only change the 'saltiness', you also change other taste balance, that you have in turn to compensate, so you are progressively moving away from the original (well - this is what Paul Mc Gowan, CEO of PS Audio has to say) - And I think it make sense to me.

So I am happy with the situation where I can add a sub without having to integrate additional devices ( + I have to re-engineer my back and front yard - And I have to spare some cash )

 

[MOON]

Hi David,

That's exactly how I do it. Run the amp off of the XLR out and the sub off of the rca out on your pre. The best placement I have found for a Martin Logan sub is centered in between your speakers with the front facing woofer out the same distance from the wall as your speakers.

It is a seamless integration and provides the smoothest most powerful bass with no boominess. I have moved my equipment around and now have the depth at the side of the room so I can see the equipment, but the performance is nothing compared to the central location.

I am contemplating picking up a second depth and keep them to the sides. I would recommend the central location hands down.
Cheers, Greg

 

[adanny]

Thanks again Dave and Adanny,
...
When you add salt to your dish ...

So I am happy with the situation where I can add a sub without having to integrate additional devices ( + I have to re-engineer my back and front yard - And I have to spare some cash )

Totally agree with you. My philosophy and system design, precisely. For 2-ch, I literally have "digital out from source -> pre-amp/DAC -> amp -> speakers. For multi-ch, I do have a processor, but no room correction, despite having a highly sound-unfriendly room. And frankly, multi-ch is SO overrated. I think even the actual sound in movies, TV etc is better when I use just 2 channels but you lose the effects.

I am personally not keen to add a crossover either. I spoke with the maker of my TADAC tube pre-amp (Paul Gryzbek) and he strongly advised against using a crossover. That said, I might get one just to fiddle and see what effect it has on clarity of Bass...