Subwoofer causing treble problems - Help!

[smrex13]

Hi everyone,

I just hooked up a subwoofer to my stereo setup for the first time and got an odd result. I am currently running an Acurus DIA 100 with Focal Chorus 706v stand mount speakers. I like the sound, but I wanted to add a bit to the bottom end. I got an SVS SB 1000 and hooked it up. The Acurus doesn't have a pre-out. So, as suggested in the directions, I ran two speaker wires from each of the binding posts - one to the speaker and one to the subwoofer. The result has been a rather obvious reduction in the detail and transparency of the treble. The amp also doesn't seem to play quite as loud as it did without the sub. Any thoughts on what might be causing this? I've used bi-wired speakers in the past with my Acurus (and the same speaker cables) without issue.

Thanks for any help!

Scott

 

[TLS Guy]

Hi everyone,

I just hooked up a subwoofer to my stereo setup for the first time and got an odd result. I am currently running an Acurus DIA 100 with Focal Chorus 706v stand mount speakers. I like the sound, but I wanted to add a bit to the bottom end. I got an SVS SB 1000 and hooked it up. The Acurus doesn't have a pre-out. So, as suggested in the directions, I ran two speaker wires from each of the binding posts - one to the speaker and one to the subwoofer. The result has been a rather obvious reduction in the detail and transparency of the treble. The amp also doesn't seem to play quite as loud as it did without the sub. Any thoughts on what might be causing this? I've used bi-wired speakers in the past with my Acurus (and the same speaker cables) without issue.

Thanks for any help!

Scott

Connecting the sub via speaker leads is a lousy way to connect a sub. It is the means of last resort. Obviously the inputs are loading your amp in a way it does not like.

Your options are to install preouts, or have someone do this for you. That amp looks pretty open and it should be a straightforward mod.

Get a different amp.

Return the sub and do without it.

 

[lsiberian]

You need a minidsp to go between your sources and the amp if you still wish to use it.

 

[ReUpRo]

So, as suggested in the directions, I ran two speaker wires from each of the binding posts - one to the speaker and one to the subwoofer. The result has been a rather obvious reduction in the detail and transparency of the treble. The amp also doesn't seem to play quite as loud as it did without the sub.

Scott, I'm curious where you got these directions since this is not the correct way to wire the sub. The reason your amp is playing softer and muddying the details is that you've effectively connected two parallel electrical loads and it is not being able to supply the required power.

You need to connect it like this, amp speaker outs to sub speaker level binding posts only. From sub speaker out to the Focal binding posts.

As TLS mentioned, this is a last resort connection scheme. As Isiberian mentioned, you need an outboard crossover or switch to an amp with bass management to properly set up the 2.1 setup.

 

[TLS Guy]

You need a minidsp to go between your sources and the amp if you still wish to use it.

The trouble with that solution is that he has no line out. So he has to create line outs to properly use that sub with his rig. That will require some knowledge and skill.

His best solution if he does not want to buy another amp, is to have preouts added to his integrated amp and power amp ins. The he can connect the preouts to the left and right ins, and the line outs of the sub to the amp ins. The sub will then do the bass management. That is his best solution. If he does not want to mod the amp and wants a sub, he needs to replace his amp with a unit that does bass management.

 

[markw]

There's nothing wrong with using the speaker level inouts.

Properly connecting the speaker outs to the subs speaker inputs should not alter the signal to your main speakers. May people have been doing it quite successfully for years wit no negative results.

but, if you set the subs crossover(being used as a low pass filer here) too high, it could muddy up the lower end of your mains range. It should be set to just where your mains drop off to avoid cutting into their range.

 

[Adam]

Scott, I suggest that you contact SVS in addition to posting here. They've always been very helpful to me in the past.

Scott, I'm curious where you got these directions since this is not the correct way to wire the sub. The reason your amp is playing softer and muddying the details is that you've effectively connected two parallel electrical loads and it is not being able to supply the required power.

You need to connect it like this, amp speaker outs to sub speaker level binding posts only. From sub speaker out to the Focal binding posts.

That was my initial thought, and then I took a look at the SB1000. It has no speaker-level outputs, and Scott connected it exactly the way that the manual says to do it on page 10.

I'm curious what the load of the sub on the amp is, as it's not using that signal to power anything. It's just extracting the audio data.

 

[ImcLoud]

Scott, sadly I think your best bet is to get a new amplifier that will take care of your sub crossing.. Or a preamp and amp you can get away pretty cheap USP1 for $369 and a dayton dta100 for $70 or any inexpensive amp you can tuck behind your preamp that controls sub crossing... Or even a stereo receiver, I did this before, they have sub out but not all of them {very few actually} will cross the lows from your mains, so you buy one that has full preouts with main ins {you will notice the jumpers on the rear panel} install a pair of fmods in between the preouts and main and it will not send any bass to your mains, some of them will need a splitter to go to your sub others take the pres from the same source and you can still use the sub out...
I can not stand the sound when the mains and subs are reproducing the same signal, so crossing the mains is a huge part of suing a sub to me, if you do this correctly you will notice better mids and highs from your mains, not worse...

 

[TLS Guy]

Scott, I suggest that you contact SVS in addition to posting here. They've always been very helpful to me in the past.



That was my initial thought, and then I took a look at the SB1000. It has no speaker-level outputs, and Scott connected it exactly the way that the manual says to do it on page 10.

I'm curious what the load of the sub on the amp is, as it's not using that signal to power anything. It's just extracting the audio data.

Although the sub will not take significant power, the characteristics of the input on the sub and in particular the capacitance of the input are important. From the OP's description it seems likely the capacitance of the load is the problem and likely upsetting his amp's output stage. It might even be inducing supersonic oscillation in the output stage, which would account for the power drain, and might well damage his amp, if he persists. If I was the OP I would not persist with this a moment longer.

 

[TLS Guy]

Scott, sadly I think your best bet is to get a new amplifier that will take care of your sub crossing.. Or a preamp and amp you can get away pretty cheap USP1 for $369 and a dayton dta100 for $70 or any inexpensive amp you can tuck behind your preamp that controls sub crossing... Or even a stereo receiver, I did this before, they have sub out but not all of them {very few actually} will cross the lows from your mains, so you buy one that has full preouts with main ins {you will notice the jumpers on the rear panel} install a pair of fmods in between the preouts and main and it will not send any bass to your mains, some of them will need a splitter to go to your sub others take the pres from the same source and you can still use the sub out...
I can not stand the sound when the mains and subs are reproducing the same signal, so crossing the mains is a huge part of suing a sub to me, if you do this correctly you will notice better mids and highs from your mains, not worse...

His amp would be very easily modified to provide pre outs and amp ins.

This is the circuit.

You could easily interrupt the circuit between the balance control and the amps. The case would have to be emptied for precise drilling in the shop, then re instal with the four RCA sockets.

The case is nice and open and would be an avenue for him. That is what I would do, but I have the facilities.

Actually on reflection, I think that unit is not worth the trouble. It has a passive preamp. Audiophools think this is an improvement, because it eliminates some active devices. They are dead wrong as they introduce worse problems. This is shown by JA in that in that unit the input impedance varied with volume setting. Now the negative feedback feeds back to the first stage of the power amp where the passive preamp connects. JA did have this amp go into supersonic oscillation under test. So I believe the sub connection is sending his amp into supersonic oscillation via the the negative feedback, which goes from out put to input.

If that amp is to be modified, the a IC buffer amp should be designed to go between the passive preamp and the power amp. That would add complexity, but not be very difficult. In addition to solving the OP's problem, I believe it would substantially improve the unit.

However it might be better to sell it along to an audiophool and buy a Creek integrated. These have preouts and amp ins and are designed properly, which this Acurus is not. That is assuming the OP wants to stay with an integrated amp.