Two closed-box subwoofers in true stereo - benefits?


Active Member
Has anyone had any experience with using two closed-box subwoofers in a true stereo setup? What are your thoughts on the sound quality in the bass range?

Many subwoofer installations appear to be single-channel versions. At least from a purely theoretical standpoint, with stereo recordings this seems to be far from ideal. Blending the low-frequency output from the left and right channels just seems like it will detract from the authenticity of the entire sonic experience.

Also, vented subwoofers seem to have major theoretical problems with transient response, being 4th-order systems (VB4). If it's an electronically equalised vented box (VB6 alignment) then a 6th-order roll-off rate is usually the norm. Sure, smaller enclosures result from using VB4 or VB6 vented enclosures, but what's the price that is necessarily being paid in terms of sound quality?

My experience has been that a stereo pair of closed-box subwoofers is to be preferred. The closed-box enclosure is larger for a given low-frequency extension, but the transient response is always going to be better than that of any vented-box subwoofer. You take your bigger box volume and you get your bass response in return.

Many years ago I had the pleasure of listening to a pair of Quad ESL63 loudspeakers, complemented by a stereo pair of Duntech closed-box subwoofers. The sound staging and naturalness of the sound was particularly impressive. This included the low-frequency range being handled by the stereo subwoofers. I haven't heard that sort of reproduction since.

I can understand that some large rooms require vented subwoofers to help get appropriate SPLs in the low-frequency range of interest. Distorted output might be preferable to no output in those circumstances. However, if true high-fidelity in a mid-size room is of interest to the listener, wouldn't closed-box subwoofers prove to be the better choice? A vented-box subwoofer just seems to be an engineering compromise that suits the desire for small enclosures, but unfortunately at the price of ultimate sound quality.

What are some good closed-box subwoofers that can be recommended?

Member 639844

Former Advertiser
First off, the mono output of an LFE sub pre-out is the stereo signal combined into one. The reason is that sub bass under the 80 hz threshold is omni directional so has no real need to be in a stereo setup, you would get none of the stereo soundstage effect.

The main reason for a twin sub setup is an integration. With 2 subs properly setup you can even out the in room response so its more accurate and it's this that will give you the improved quality your experiencing. This is not to say it's impossible to do it with one sub, but generally speaking you can do it better with 2 or more.

As for ported design verses sealed, well this is all down to the design of the box. Certainly cheaper subs use ports to boost spl output and create 'fake bass' if you will, but this isnt the case with well designed higher end subs. There is of course the issue of port chuffing and similar effects you get from ported designs that you may wish to avoid by going with a sealed design and thats fine, you just have to remember that if you want the same spl levels you need to spend a bit more. For example the sealed JL fathoms are excellent subs, they are a bit faster and tighter (from what I hear) than my SVS Ultra sub, but I gain more depth and SPL from my ported design. You can probably extrapolate from that some sort of back up to what your saying, but in sealed mode my sub still goes deeper and louder and thats down to good design, the ports merely give you tuning options to play with. There is also tha fact the fathoms cost twice what my sub does and this is where it becomes a bit of a cost/performance trade off and you really have to start looking into the entire package to see if it deliver what you truely want. Properly setup, twin Ultras or Fathoms will give improvement over a single sub in many a rooms but its all down to what you want. It seems to me the Fathoms are probably a bit better with music, but mine is better for HT. My personal take is that I want my speakers to make up for music failings of my sub but this is a personal choice.

Really its down to what you want, a properly designed sealed sub will be amazing but so will a properly designed ported one (seaton submersive, ED subs or Epik subs anyone?). You need to look at your room, your system, your requirements, your budget, your preferrred sound, then put it all together to get the product thats right for you.

You have noticed how 2 subs setup properly can give a better response, but it needs to be 2 good subs, by that I mean cutting your buying budget in half to buy 2 subs isnt the way forward. You can even out the response of the two subs to maximise the results they produce, but they still cant exceed what their design dictates. For most of us this invariably means our whole budget goes on a single sub to get the most from what we can afford.

One thing I haven't mentioned here is the ability of some subs to use a high level stereo connection, but without diving into that to much, IMO it has little bearing on any of the above as even if you used this method you still have 2 subs producing an identical signal and its nothing like the 2 separate channels of your front stereo speakers. Most of what you heard in the experience you recall is simply a very well setup system all working well together, and it shows the importance of good speakers to go with your good sub and to properly set it all up.
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