Separate subs for bass management & LFE in a surround set up
I guess I should elaborate The room is a custom design (golden ratio) Floated floor, bass traps Tons of absorption & diffusion on the walls & ceiling All Martin Logan speakers & subs so well integrated And the Trinnov preamp/processor to tune all the channels to match room response for amplitude, phase & delay But since I've gone that far, I'm just trying to take any last possibilities into play. Companies that record for surround like 2L & Sono Luminus and definitely Steven Wilson purposely put a full range of sound into each speaker on the left side & right side of the array. My question is more, will I lose some of the utility of the 1/4 placement for wave cancellation if both left and right front subs aren't playing the exact same signal i.e. left sub has left side low pass info and right sub has right side. If they both have the summed to mono total of all speakers then they will be playing the exact same signal, hence the bonus of cancelling axial modes. If they don't then I may lose that help in taming the room for a potential bonus of a moderately perceptible (if at all) ability to recreate the effect of using all full range speakers and the same imaging as the recording engineer's mix or better, the ambience of the room where a live recording was made. |
My question is more, will I lose some of the utility of the 1/4 placement for wave cancellation if both left and right front subs aren’t playing the exact same signal Yes. Is it worth $5? Probably not. What I mean is from an absolute testing / measurement perspective would you be able to measure a difference? Yes. Would you hear it with real music? No. E |
Again I agree with Eric. As you must be noticing multi-channel music post production is quite interpretive yet still manages to convey space for the most part. I'm guessing your extra low frequency concerns are more a matter of your rooms reaction to ELF and your personal taste. I've set up my two channel system in three different homes, including one with similar dimensions as yours. Running my TWO subs in plane with the main speakers in stereo was only slightly worse than in mono and was confirmed by my subs built in Room Optimization software. While four subs would completely change my situation I think I'd still be pessimistic regarding ELF stereo imaging unless you run two at unusually high crossover points. With the added flexibility of using four subs experimentation should provide you with far more knowledge and hopefully the results you're seeking. |
Not really what you are talking about but here is another way hook up your subs. JL audio subs will let you play both the LFE from your reciever AND the two channel high pass at the same time but you need a sub for each channel. JL audio inputs are summed. There is a right and left input on each sub. On the right if you send your right preout channel signal to the sub and from the sub to the amp. On the extra “left input” send the LFE channel. Do the same on the left side. This setup allows the subs to be blended with the mains through the crossover but still play the LFE signal. You can then boost the LEF from the reciver like normal and extend the range of your mains at the same time. I have ran mine this way for years with my subs set up for two channel but when using the HT reciver (by pass mode) the subs still play the LFE. For what it is worth I think subs can be localized (in a large proper room) and should sit beside the speaker they are extending. |
Thanks Eric, By the time I finished writing my second post on this, I had come to agreement with you. The room effects cancellation advantage of a four sub system can be adversely affected if they aren't playing the same signal. And I think having that free room fix may be the most important thing I can get from the 4 subs. But James your point relates to the initial reason I asked this and I read something from JL Audio about this exact concept https://jlaudio.zendesk.com/hc/en-us/articles/205061040-Adding-a-Home-Audio-Subwoofer The advantage I have is the Trinnov pre/processor lets me have a couple dozen presets and all the routing for channels is done electronically. Then it builds a custom filter for phase, amplitude =, delay etc to fix as many anomalies as possible before sending signals to all the amps. So I can have one set up where all the bass management & LFE goes to all four and they do their axial mode cancellation. The Trinnov images each speaker in space using a 3-d mic so it will know there are 4 subs in a 1/4 config and apply DSP accordingly. But I can also do a second preset and route the LRC, LS, LRS to the left subs and the right side channels to the right sub for music recorded using actual stereo imaging and mic techniques. This is even valid for surround recordings because if they do a live room right they will have a mic corresponding to each speaker and so the mix will reflect essentially a stereo image left and right to the ears, just with the multiple speakers on the left & right sides respectively as arrays, essentially as a single speaker system just not in the same box. But designed to reproduce all the audio info coming from that side of the room . Anyhow thanks to all for helping me think this through. I will advise as to its effectiveness once its operational |
Have all the subs play LFE and crossover signals unless your room leads bass to be highly localizable. Mad a simple test, only have the rear subs turned on and play a test tone at the crossover frequency, if you can tell it’s coming from behind you, then either lower the crossover point or do what you described initially. However, I would say the benefit of quad subs playing the same signal trumps slight localizable benefits. |
