Sub Woofers another opinion

Discussion in 'Audio Visual' started by Hi-end Head, Oct 13, 2021.

  1. Hi-end Head

    Hi-end Head Member

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    While there is much discussion about the use, output, benefits, etc,etc of a Sub Woofer, and it's a fact that everyone has a different opinion both for and against, This offering from another forum may shed a different light on the subject. In short it's well worth your time to read.. And of cause comment.


    Barry Ober has more than 35 years research into the best methodology for the easiest and most comprehensive subwoofer integration and system alignment, including speaker imaging.

    I've read most of his website and used his techniques to integrate my JL Audio F212v2 with my 2-channel system. Bass dynamics, imaging, and clarity are significantly better than any 2-channel system I've experienced at RMAF, Audio showrooms, or in my home. All but a very few ported speaker systems with separate bass towers should have subwoofers to experience evocative low frequency bass.

    The following are excerpts from his extensive website: (The Sound Doctor)

    A ported speaker is ALWAYS nothing more than a cheap way to attempt to get free bass out of an enclosure and /or driver that's too small. It's a holdover from the 1930's when because of driver inefficiencies (especially when compared to today's units) you had to do everything possible to increase the useable output over the desired range of low frequencies.

    When the manufacturer of a speaker cabinet defines the frequency response (I.e., 37 Hz - 20kHz +/- 3dB) this is what is defined by the entire arrangement of the port and the air in the cabinet and the driver. At some low frequency the port air is exactly out of phase with the driver air pressure and since they cancel, there is NO output from the cabinet into the room. Therefore with a ported cabinet, the entire sloppy concept is this juggling game between the response of the drivers under air pressure, the passive crossover inside the box, the port size and placement.

    Simply connecting a sub to existing mains speaker (or amp) terminals is the WORST POSSIBLE WAY to do this. EVERYTHING scientific and acoustic about this method is wrong, from the additive delay issues to the back EMF of the mains affecting the LF signal. However there are plenty of people who simply do not understand correctly integrated bass, and they will be reasonably happy simply sticking another box on to their system without regard to timing, phase and frequency issues, and they will think it sounds "ok" or "good" and for those people it doesn't really matter.

    Some audiophiles don't want to introduce yet another active "thing" in their precious signal path, not realizing that adding the crossover is very much the lesser of two evils.

    Actually adding a crossover is really a WIN-WIN situation:

    WIN # 1) Since you are now NOT putting in 20 Hz - 80 Hz into the mains you are not using up the available LF cone movement with bass, so the LF cone in your mains is able to play its higher freqs (up to IT'S crossover point) much more cleanly. You get an apparent 6dB or more dynamic range. You can play your system LOUDER, and also with less compression distortion in the LF driver when you're having that Saturday night dance party and you're playing urban bass technopop at 110+ dB. Really.

    WIN # 2) Since you are not putting bass into that same driver you are not Doppler modulating everything between 80 and 600, or whatever the next crossover point is. This means cleaner mids. By far.

    WIN #3) You are not sucking current out of your main power amp at low frequencies, so there is more current reserve to play those highs louder...

    WIN # 4) Since the cones aren't moving as far at the low freqs the driver itself is not generating as much back EMF therefore the damping factor and all of its issues are greatly negated. And you don't need to run silver plated cold water pipes to your mains as speaker wires because there is less current draw by the speakers.

    WIN # 5) Freqs below 80 are now NOT causing transient intermodulation distortion with the higher freqs (and vice versa) in your power amp. Cleaner still.

    If you have a 2-channel only system if you do not correctly use a crossover you are both wasting your time and you will be frustrated.

    If your speakers are ported, you SHOULD close (seal) the ports. Towels will do for a test but you might consider purchasing a 3", 4", or 5" thick slab of "foam" at a notions / sewing store. What you are trying to accomplish is to NOT have multiple sources of differing phase relationships (the main driver, the port air, and the sub driver) at or near the crossover frequency.

    Invert the polarity of the MAIN speaker the sub is CLOSEST TO. Disconnect all the other speakers in the room. Place your head equidistant between the sub and the speaker it is closest to. Play the 80 Hz tone. Adjust the phase control AND the level control and both settings of the polarity switch until you hear a distinct NULL. (IT MIGHT EVEN DISAPPEAR COMPLETELY) There should be some setting of the two controls on the JL sub which will provide a rather sharp null - this is a CRITICAL setting and you might find it to be very sharp. Now put the wiring back the correct way to that one speaker. Reconnect the other speaker and you're done.
    ________________________________
     
    RnR likes this.
  2. stiben

    stiben Member

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    I can agree with the importance of correct integration, a miniDSP SHD is the best thing since sliced bread in my system. All my previous efforts at integration were futile by comparison.
     
    JSmithDTV likes this.
  3. neRok

    neRok Member

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    I'd been meaning to fiddle with my system. Just using some old yamaha digital receiver with my pc, along with matching sub, but had never gone through the menus to config it. So the fronts were set to large, which means all frequency, so I changed to small, which means <90hz sent to configured bass speakers. Then the bass speaker was set to both (fronts and sub), so change that to sub. Also had the distance set to 2.3m, so put that down to 0.9m. Put the socks in, and it still sounds good. So, will give it a few days and see if there is an improvement.

    My setup gets more budget by the day :Pirate: Those speaker stands are hummus buckets full of sand btw :lol:

    spkr.jpg
     
  4. Holdenkicks

    Holdenkicks Member

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    Good read.
     
  5. Sarsippius

    Sarsippius Member

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    I didn't realise it was "a thing" to add a sub and not use a crossover, I understand some wouldn't know but "audiophiles" purposely not using one :confused:

    I don't have a great deal of experience with sub integration but I have a good set of floorstanders, TL design and I was always pretty happy with the low frequency output. I decided a sub would be a good idea for movies so I designed and built one myself, using a plate amp with a built in dsp that would high-pass the output to my 2-ch amp.

    I'm a bit lazy so I ended up just tuning it by ear but it made a huge difference, not just movies but music is much better as well. I ended up crossing over a bit higher than I expected, high-pass at 95Hz and low-pass at 90Hz. I could/should probably put a bit more effort into tuning but like I said I'm lazy and it already sounds so good.
     
  6. Audionut

    Audionut Member

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    Oh, I just found my alley. Ports are a lazy man's method of increasing SPL at the expense of quality.

    https://soundoctor.com/whitepapers/subs.htm
    This one will drive home the importance of electronic crossovers and separating the frequency response amplification.

    jtlden over at Home Theatre Shack is very knowledge with using Room EQ Wizard to time align drivers*.

    Some other links of interest, some may be out of date.
    https://mehlau.net/audio/room-correction-peq/
    https://www.diysubwoofers.org/misc/holmimpulse/ta.html
    https://data-bass.com/#/?_k=c03l1q
    https://www.linkwitzlab.com/rooms.htm
    https://forum.blu-ray.com/showthread.php?t=48286
    https://www.hunecke.de/en/calculators/room-eigenmodes.html
    http://tripp.com.au/sbir.htm
    http://www.acousticmodelling.com/porous.php

    edit:* It's been so long since I've had to do this, but from memory I used the impulse graph to get the sub and mains in the ballpark, and ensure the sub wasn't a cycle or 2 late, then used the combination phase+SPL graph for the smoothest response through the crossover region.
     
    Last edited: Oct 25, 2021

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