Help with a 2.1 setup configuration

[YoniV]

I currently use a pair of JBL LSR305 conneceted to a d50s+Atom on my working desk.
I'd like to add a subwoofer, and was considering the (recently reviewed) Rythmik L12. Two questions:
1. Would it be a suitable choice for a roughly 3 x 3.5 m^2 (10 x 11.5 ft^2) room?
2. What is the proper way to connect the system? Should I split each channel coming from my preamp and send one to the speaker and the other to the corresponding sub input? Or do I need to do something more than that, e.g. a preamp with dedicated outputs?

 

[adw]

1. I don't know

2. I think the proper way is using active crossover and the fastest and easiest way is to split pre-amp output.
Since the JBL LSR305 did not have line-out, you have to control the volume in the D50s, or the atom if volume knob is also control line-out level.

 

[YoniV]

Thanks for your reply!
The Atom indeed controls both headphone and RCA outs.
What do you mean by active crossover? And does splitting the preamp out amounts to a simple Y connector?
In that case, will the volume knob of the Atom increase the volume of the speakers and the subwoofer by different amounts due to differences in sensitivities? (such that if they are balanced in one position of the volume knob, they will be unbalanced in a different position.)

 

[adw]

What headphone outs? If Atom is an amplifier and it has volume control and RCA out that can be use at the sametime and the volume is also controled by volume knob. Just connect the subwoofer (L and R) to the Atom RCA outs.

No need external active or passive crossover as it is already available on the sub itself.

In that case, will the volume knob of the Atom increase the volume of the speakers and the subwoofer by different amounts due to differences in sensitivities? (such that if they are balanced in one position of the volume knob, they will be unbalanced in a different position.)

No, it won't.

 

[Chrispy]

What headphone outs? If Atom is an amplifier and it has volume control and RCA out that can be use at the sametime and the volume is also controled by volume knob. Just connect the subwoofer (L and R) to the Atom RCA outs.

No need external active or passive crossover as it is already available on the sub itself.

No, it won't.

Looking at the L12 info it only appears to have the typical mislabeled low pass filter as "crossover". It does apparently employ a high pass filter as a rumble filter, tho.

 

[YoniV]

I'm still a bit confused regarding my original question: how am I to connect the system?
The Atom is a preamp (+ HP amp), not a power amp. Both the LSR305 and the L12 are active.
However, I have only two RCA outs, but the above 2.1 would require 2x(L+R) ins.
So - is the way to do it is with a couple of Y connectors from the Atom, or do I need something extra to make it work properly?

 

[Chrispy]

Might just consider the JBL 310S matching sub, it also has an actual crossover.

 

[Doodski]

Does the Rythmik L12 sub that you want to buy have stereo inputs?
Yes, it appears to have them.
Then you can use a Y-cable at the pre-out of the headphone amp and run one to the sub and the other to the JBLs.
Then use the level/volume/gain adjustments to balance out the sub and mains speakers volume levels.

 

[Doodski]

You will need to unplug the headphones if you want to use the pre-out from the Atom headphone amp.
There should be a low enough output impedance from the Atom to run both the sub and the JBLs.

 

[YoniV]

You will need to unplug the headphones if you want to use the pre-out from the Atom headphone amp.
There should be a low enough output impedance from the Atom to run both the sub and the JBLs.

Of course, this is what I am already doing.
Thanks for the answer, Y connector was what I thought I needed to do, but wasn't sure if I should expect problems that I haven't thought of, having never owned a sub (e.g. impdance issues etc).

 

[Doodski]

Of course, this is what I am already doing.
Thanks for the answer, Y connector was what I thought I needed to do, but wasn't sure if I should expect problems that I haven't thought of, having never owned a sub (e.g. impdance issues etc).

No worries. You should be good to go. There is a slight chance the output of the Atom might be low but that's a very small chance.

 

[YoniV]

Currently, on the 305's only, it has plenty of headroom: with the 305's gain set to ~5/10, I only make about a third of a turn on the Atom to reach satisfying volume (d50s maxed). Hope that's going to be enough!

 

[Doodski]

Currently, on the 305's only, it has plenty of headroom: with the 305's gain set to ~5/10, I only make about a third of a turn on the Atom to reach satisfying volume (d50s maxed). Hope that's going to be enough!

Sounds like you should be good to go.

 

[Chrispy]

As to connections t o a sub without a proper crossover (which can also vary whether it's via low or high level inputs depending on sub amp), without a mono sub pre-out, splitting the line outs with your speakers and using a sub with L/R inputs to sum would work.....whichever sub you decide on be sure to look at the available connection options....

 

[YoniV]

What do you mean by proper crossover? Or, what is active crossover, as adw mentioned? The L12 has a crossover setting; do you mean a dedicated crossover device/feature in a receiver?

 

[Chrispy]

What do you mean by proper crossover? Or, what is active crossover, as adw mentioned? The L12 has a crossover setting; do you mean a dedicated crossover device/feature in a receiver?

A crossover is a combination of a low pass filter for the sub and a high pass filter for the speakers, where they "cross over" at a given frequency. Many subs even though labeled as a crossover is just a low pass filter (and the L12 appears to be this type as there's no mention in the literature of the high pass filter connection/setting for the speakers). Perhaps some of their subs has such but I don't see it for the L12; the JBL 310S I mentioned does have such.

Other ways of managing crossover include adding something like a minidsp 2x4 to provide an external active crossover, few 2ch pre-amps have such, though. AVRs have such (and more extensive bass management in general).

 

[YoniV]

Ah, makes sense, thanks for the explanation!
In comparison to the rest of the 3 series from JBL, I didn't hear many great reviews about the 310s, although it is on my list to audtion for quite some time. Once things clear a little with the coronavirus, I will try it out.

I guess that without a crossover on both ends, it is probably inevitable to need to eq-out a hump/dip in the crossover region after balancing the volume of the speakers vs sub. You'd probably need to do it even with a proper crossover anyway, perhaps to a lesser extent.
In any case, intuitively it sounds quite correctable, unless the crossover region happens to correlate with a room mode or something.

 

[Jmudrick]

The two clear advantages of the 310s is that it's plug n play with the 305 and you can get two for not much more than one Rhythmik (if you have room). I paid $250 each for my pair, Harman has them for a little over $300 delivered on sale.

 

[YoniV]

An interesting point, although I'm not sure I do have room for two, as the intended room is not that big and already hosts some musical instruments including 2 guitar amps competing for real estate.
I also didn't read enough into the huge discussion I know exists for the comparison of two subs vs one.
Finally, in this case, I am again confused at how one should connect the setup. Did you split the preamp out with a Y-connector feeding the two 310s, then took one of them and fed the speakers?

 

[Doodski]

Hmmz the JBL LSR310S subs with JBL LSR305 speakers.
Yes, you would need to use more Y-cable adapters and then adapt to the balanced inputs versus the single ended RCA input of the Rhythmic sub.
There will be a larger expense for cabling when using the JBL LSR310S subs.
Now the load impedance of the speakers and sub for each channel will be getting pretty low but it should still be manageable.
There's only one way to find out if the signal levels are sufficient and that's to connect it all and test drive it.
There shouldn't be any grounding issues and such so it's just a matter of output impedance supplying the input impedance with enough power transfer.(Shouldn't be grounding issues does not mean won't be any.)