PSA: Short Unused Speakers and Subs in the Listening Room

Speakers move when input voltage applied to the coil creates a magnetic field that attracts it towards, or repels it away from, the fixed magnet. Moving the cone with your finger does the reverse, creating a voltage in the output. This is exactly the way a microphone works.

Shorting the terminals creates a situation where the same voltage being generated by moving the cone with your finger, is simultaneously putting voltage right back into the coil resisting this same motion. As a result it moves hardly at all.

If the speaker is sealed design then you have pretty much turned it into a closed box. But if it is ported then you have created a speaker sized Helmholtz resonator.

Shorting the terminals creates a situation where the same voltage being generated by moving the cone with your finger, is simultaneously putting voltage right back into the coil resisting this same motion. As a result it moves hardly at all.

Is that why it works? Makes sense. My assumption was that with an open circuit, only voltage is created and with a closed circuit, current can flow and the internal resistance of the wire and speaker eats up the power in the circuit. I hadn’t put too much thought into it. I think I like your explanation better.

If the speaker is sealed design then you have pretty much turned it into a closed box. But if it is ported then you have created a speaker sized Helmholtz resonator.

That would be a good thing right? Or is it only a good thing if your room has a nasty resonance peak at the absorbing frequency of the shorted and ported subwoofer?

By the way, I think the low frequency performance of my system increased after shorting the unused subwoofers. I was only able to listen to one song (that wasn’t especially bass heavy) after I made the change but it seemed clearer in the bass frequency department.

@millercarbon You're back!

Rooms are more similar than most think. Geddes paper, the gold standard study and paper on this, is linked below. The one thing I would add, we didn't know enough back then (this was more than 30 years ago) about the importance of isolating speakers in order to avoid them mechanically exciting room resonances. Without isolation, vibrations generated by speakers and subs flows right into the floor, walls and ceiling, with the result the whole room structure is mechanically set to vibrating. Walls in effect become radiators of sound, speakers, themselves. 

As with so many other things that happen so often we've probably never heard anything else, it is difficult to even know this is what's happening, and even harder to appreciate the extent to which this is going on- until it's gone!

Most typical solutions involve lots of monstrously large bass traps. The best room I've been in, faux walls were incorporated that hid bass traps the size of a large walk-in closet! Wonderful sound, but who has the room and construction budget for that? When my subs were isolated on Nobsound springs the improvement was greater than a large tube trap that had been used. When they were moved to Townshend Pods the improvement was profound! The extent of this was hard to appreciate until another visit to the best room, and this time when coming home was no longer disappointed in my awful bottom end. This experience was repeated at a friends, when we moved his Pendragons onto Townshend Podiums. He was shocked, it was like a whole different room! 

Here’s my question: If you only care about one listening position, are multiple subs really better? I just can’t shake the thought that multiple subs (4 or more) spread throughout the room wouldn’t integrate that well with each other. Would the bass be smooth and full? Good lord, yes. But true to the original signal? I am not sure on that. Perhaps it’s the best we can do though. 

Oh nooo!

Welcome back @millercarbon !

roxy54- Yes I am back. Thanks.

ratboysr- You are one of the reasons why. Well, sort of. In a way. In the sense you represent the sort of readers I never really knew about, but are out there. Something that didn't hit home until I launched my website an instantly had a huge (for what it is, which ain't much) influx of visitors. So many thanks, it is much appreciated.

mkgus- Yes multiple subs are really better even if all you do is sit in the same place. That's what I do, and the improvement is massive. 

As for true to the original sound, with a lot of recordings that is anyone's guess. But come listen to Tchaikovsky. Or Belafonte at Carnegie Hall. Or anything faithfully recorded in a large venue. The way that is recreated is uncanny. Heck even Peter Gabriel Secret World Live, the unmistakable sonic signature of a huge space is captured like nothing else. The only other room I heard anything like this was an impeccably acoustically designed and tweaked out room that also had two huge racks of subs, not a classic distributed array exactly but with 4 on each side stacked 5ft high not all that different either.

When you hear it, in like 5 seconds you will jettison all doubt. 

Welcome back MC. The more minds, ears and opinions the better when looking for something so slippery as audio nirvana. Your expertise was surely missed.

The only other room I heard anything like this was an impeccably acoustically designed and tweaked out room that also had two huge racks of subs, not a classic distributed array exactly but with 4 on each side stacked 5ft high not all that different either.

Reminds me of the Infinity IRS V speakers which have 6 stacked bass drivers per side. The sound was jaw-droppingly good! Why use 1 subwoofer when you can use 12? Just don’t forget to short them if you aren’t using them when listening to music. Actually, I’m quite sure you can accomplish the same effect as shorting by simply turning on the amplifier but don’t feed it a signal. I get the same effect tapping on the cone and hearing silence by turning on the amplifier as I do with shorting. I wonder what the technical reason is. 

I did a double-take!!  Nice to see your post, MC!!  

MC,

Long time!

The extra speakers myth was debunked in the 80's by the Boston Audion Society with none other than Linn's Ivor. Look it up.

Multiple subs are for more even bass throughout the room not accurate bass at the LP. Read Toole's book. 

see ieLogical DBA Sim

+1 millercarbon

Welcome Back....

Ivor required dealers to store extra speakers in another room, the astute also shorted them…. of course this was…thirty plus years ago…. hardly a “ new discovery “. …..