Help with 2.1 setup
Feb 23, 2012 at 8:53 AM Post #16 of 37

DAhn626

Head-Fier
Joined
Feb 1, 2012
Posts
76
Likes
12


Quote:
OK, I see that the OP‘s sub is passive as well. Then it seems basically he needs a mono amp to power the subwoofer to complete his setup. But he certainly doesn't need to sell everything and start all over.


Could you expound on this? I have another amp that's just sitting around (HK750). Could I use that here? And how do I hook the two amps together..?
 
 
Feb 23, 2012 at 11:18 AM Post #17 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
Connecting the amps is easy, just connect the pre-outs of your first amp to the line in of the HK750.  But the HK750 is a stereo amp, I dunno how you're supposed to hook that to your sub which takes one channel.  Does it have a mono switch?  Maybe press that and wire your sub to either one of the outputs?
 
Or if you're not afraid of blowing the amp, you could try wiring the red for both channels to the red on the sub and the black for both channels to the black on the sub.  Theoretically this downmixes the channels and allows the two channel's amplifiers to drive the sub in parallel, increasing power, but according to wikipedia you're supposed to add a bit of resistance between the two channel outputs otherwise the amps would overheat...
 
Or you could do your previous thing and hook the sub to the red of one channel and the black of the other?  I don't even want to think about what this means electrically but if it worked for you before...
 
Feb 23, 2012 at 4:25 PM Post #18 of 37

DAhn626

Head-Fier
Joined
Feb 1, 2012
Posts
76
Likes
12


Connecting the amps is easy, just connect the pre-outs of your first amp to the line in of the HK750.  But the HK750 is a stereo amp, I dunno how you're supposed to hook that to your sub which takes one channel.  Does it have a mono switch?  Maybe press that and wire your sub to either one of the outputs?


 


Or if you're not afraid of blowing the amp, you could try wiring the red for both channels to the red on the sub and the black for both channels to the black on the sub.  Theoretically this downmixes the channels and allows the two channel's amplifiers to drive the sub in parallel, increasing power, but according to wikipedia you're supposed to add a bit of resistance between the two channel outputs otherwise the amps would overheat...


 


Or you could do your previous thing and hook the sub to the red of one channel and the black of the other?  I don't even want to think about what this means electrically but if it worked for you before...



 
 


Yeah the sub literally just has the one red n black connector (although it supports RCA)

I'm a little confused..if this is a passive sub, where would it normally hook into on a receiver?

As for the Amps hooking up, would I just need an RCA cable to hook from speaker out to speaker in and voila?
 
Feb 23, 2012 at 6:34 PM Post #19 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
Uh can you post pictures of the back of your subs and two amps?  Your descriptions are confusing me and anyway it would then be easier to describe to you what you need to do.
 
A picture of the front of the HK750 too if you could.  Does it have a "mono" button?
 
Feb 23, 2012 at 10:16 PM Post #20 of 37

Mauricio

500+ Head-Fier
Joined
Feb 4, 2012
Posts
634
Likes
28


Quote:
An active system wouldn't require an amp...correct? Or am I missing something here? 
 



All loudpspeaker systems, active or passive, require a power amplifier.  In an passive system, the power amp lives outside the speaker, between the preamp and the crossover.  In an active system, the power amps live inside the speaker, between the crossover and the driver.  An active system is more efficient and economical because you need no more than half to an eighth of the power (W) to accomplish the same thing as a passive system.
 
Feb 23, 2012 at 10:28 PM Post #21 of 37

Mauricio

500+ Head-Fier
Joined
Feb 4, 2012
Posts
634
Likes
28


Quote:
 
Or if you're not afraid of blowing the amp, you could try wiring the red for both channels to the red on the sub and the black for both channels to the black on the sub.  Theoretically this downmixes the channels and allows the two channel's amplifiers to drive the sub in parallel, increasing power, but according to wikipedia you're supposed to add a bit of resistance between the two channel outputs otherwise the amps would overheat...
 
 

Overheating is one possible consequence.  Another is distortion.  Why is the amp overheating?  Because you are connecting the sub and the satellites in parallel.  Basic electric circuit theory says that two resistives loads connected in parallel look like a smaller resistive load that that of either of the individual loads.  As your amp struggles to provide more current (to a now less resistive load) it will heat up and be driven to the non-linear part of its operation, giving rise to distortion, or shutting down.  Adding a resistor will reduce the current, but it will also reduce the amplification/gain as now the amp drops some of its voltage on this new resistor.
 
The above fix also suffers from the fact that both the sub and the satellites are reproducing the bass frequencies, leading to exaggerated bass.
 
My advice:  sell your speakers, subs and amps.  Cut your losses, wipe the slate clean and start anew with an active system.
 
 
 
Feb 24, 2012 at 12:50 AM Post #23 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
Mauricio I understand you're an "active" active proponent, and I know the advantages of an active system too.  But we're talking about connecting the subwoofer to a separate amp dedicated to driving the subwoofer.  The question of how to wire the subwoofer only came up because we're trying to wire a mono sub to a stereo amplifier (but a different amplifier from the one used to drive the left and right channels).
 
What is the defining characteristic of an active system?  That each amplifier drives only one driver.  In that respect powering the sub with a separate amp is no different from having an active sub. (ok, not quite in this case because there's a passive crossover in the sub; there's still power loss but you do get to avoid the problems of two drivers of different frequencies interfering with each other on the same amp / crossover network)
 
As for frequency response problems,
 
1.  There's a passive crossover in the sub.  You can just set it so it crosses in below the point at which the main speakers lose power.
2.  There's this thing called a software equalizer that you can install on the PC, you can use it to take out any humps in the frequency response.  And there will be plenty of humps regardless of whether the crossover is active or passive, because of room modes.  I run a separate parametric EQ for each channel, I just might connect the sub directly to another channel on the PC and run three EQs, two for the main speakers and one for the sub, altogether serving as my own active crossover network.
 
Feb 24, 2012 at 1:58 AM Post #24 of 37

Mauricio

500+ Head-Fier
Joined
Feb 4, 2012
Posts
634
Likes
28
Fair enough.  I won't run any more interference.  I'll just leave it by clarifying that the defining characteristics of active designs are:
i.) the crossovers are active and handle line-level signals;
ii.) the amplifiers are hardwired to the drivers and designed specifically for the driver's frequency range, impedance and efficiency; and
iii.) the crossover comes before the amp.
 
Feb 24, 2012 at 2:16 AM Post #25 of 37

Ksharp

New Head-Fier
Joined
Jan 31, 2012
Posts
13
Likes
0
If you do decide to sell your amp and can get a Dayton Audio APA 150 amp where you live. It will make your set up much simpler. The APA 150 has a low level in/out. Or find another amp that has this same set up.
 
 
Feb 24, 2012 at 2:28 AM Post #26 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
I'm getting conflicting info about the OP‘s sub. Now most of the stuff I read states that it's a powered sub. Does your sub require mains power input? If it does then it's a powered sub. And you also say it takes RCA input? A passive sub would have no use for that either.

If it's a powered sub you don't need the second amp. It would just be a matter of downmixing the stereo signal to mono somehow if the sub only takes mono input.
 
Feb 24, 2012 at 4:16 AM Post #27 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
On the stereophile review you linked to it says the SW2P is a crossoverless passive sub powered by the MA-1 dedicated mono amp. Is that what you have? But I take it you don't have the amp just the sub?
 
Feb 26, 2012 at 3:11 PM Post #28 of 37

DAhn626

Head-Fier
Joined
Feb 1, 2012
Posts
76
Likes
12
Sorry about the late reply. Yes, I don't have the amp, just the sub. 
 
These are the pictures of the back of the amps. 
 
The Ariston:

 
And I decided to use the other amp because it had 2 sets of speakers I could use. I just activated Speaker 1 and Speaker 2, using one of the sets of the speakers and the other for the subwoofer:


And so I just have Speaker set 1 and 2 activated...just that set 2 has the subwoofer hooked into it. Is this not a good idea? Should I still try to connect both Ariston and the HK amps together and control the subwoofer separately? As for the Subwoofer, I forgot to take a picture, but I found a picture on google:
 
http://img.auctiva.com/imgdata/4/4/3/6/8/4/webimg/480505331_tp.jpg
 
Feb 27, 2012 at 12:23 AM Post #29 of 37

Joe Bloggs

Member of the Trade: HiBy / EFO technologies Co
His Porta Corda walked the Green Mile
Joined
Oct 21, 2001
Posts
11,656
Likes
3,577
Location
Hong Kong and Melbourne
It's better than hooking both the speakers and sub to the same outputs... just that the sub would only be playing only sounds from the right channel.  You could use your first amp to output to the left and right speakers, then use a stereo to mono RCA adapter to mix down the channels output from the first amp to the right channel of the second amp then connect the sub to the right output of the second amp.  That would give you subwoofer output on both channels.
 
With the amp driving just one speaker (the sub) it might be able to output more power to it too... are you sure it has enough power to drive the sub anyway?
 
Since your version of the sub doesn't have a crossover built in it might be a good idea to do bass management on your PC... does your PC have more than 2 channels of output?  Is it possible to configure it to output a separate subwoofer channel?  Then you would connect the first amp to the stereo output on the PC and the second amp directly to a subwoofer output.  On the PC you would configure the crossover frequency etc.
 
Feb 27, 2012 at 10:11 PM Post #30 of 37

DAhn626

Head-Fier
Joined
Feb 1, 2012
Posts
76
Likes
12
My eyes just went @_@
 
Haha I'm sorry, i'm still pretty new at this. I ended up picking up a stereo RCA to Stereo RCA. Should I return it for a RCA to mono RCA? 
 
And would it go something like...
Amp 1 RCA (right)-----Amp 2 RCA (right)
Amp 1 RCA (left)_____|
 
and then speaker cable on the Subwoofer
Red----left speaker output (Amp 2)
Black__|
 
(where the ----- and | are wires)
 
 
As for the PC program, I have a mac :frowning2: and I'm connecting using a RCA to 3.5mm. I feel like I'm going to get scolded for my newbness. I apologize in advance. 
 

Users who are viewing this thread

Top