Infra-bass

Discussion in 'Sound Science' started by Niouke, Oct 13, 2017.
  1. Niouke
    Greetings all,

    I've been discussing speakers on a facebook group and I've been told that audophiles seek a linear reponse all the way down to 20Hz, and that since my RP-250F have a "db" (?) of only 35Hz I should consider adding a subwoofer to my setup.

    I looked up facts and the official specs say "FREQUENCY RESPONSE 35-25kHz +/- 3dB" and the freq curve of a larger model (RP-280F) seem to indicate that the response does drop off under ~35hz.

    Now I have a couple interrogations:
    Is it a real problem? I like bass, I slightly EQ for more bass on the amp and am generally happy with the thump the speakers give, but am I missing something in the 20-35Hz band? To me there is not much musical content in that range..

    How can I fix it? I didn't try to software EQ that narrow band, but as my speakers are bass reflex I presume it would be useless, as the membrane doesn't actually produce the deeper frequency, but the resonnance does?
    I looked at a few subwoofer and the cheapest that goes this low I found is the Earthquake CP-8...355€ for a 15Hz band is it worth it? the whole system without a source cost me about 1200€...

    Feel free to move this thread even tho I'd prefer answers from the sound science crowd. Cheers!
     
  2. bigshot
    Balancing the frequency response is much more important in the core frequencies than the far edges of hearing, but it's still good to balance your bass as low as your speakers go and deal with room acoustics issues particular to bass. Sub bass does play a part in music, not so much for musical notes as for the rhythmic thump. If your speakers are only rated to 35Hz at +/- 3dB, odds are in your living room there will be even less bass in practice. A subwoofer can help fill in by taking over all the power hungry frequencies below 80Hz, which will take a load off your amp and maybe make your mains perform better. But of course, if you're happy with the sound of your system, you don't absolutely need those bottom two octaves.

    When choosing a subwoofer, the focus shouldn't be on how low of a frequency it can produce, it should be the smoothness of the bass through the range and how much power the internal amp has. Really good subs aren't cheap.

    Hope this helps!
     
  3. 71 dB
    As you said, most music has very little if any musical infomation below 40 Hz. Organ music and movie soundtracks can have low bass content. You have a problem only if you make it one. Reproduction of 20 Hz is difficult. It takes power and size to move air enough at so low frequencies. 20 Hz is 8 times more demanding as 40 Hz and 64 times (!) more demanding than 80 Hz. As this wasn't enough trouble, hearing treshold at 20 Hz is very high, about 75 dB, so 90 dB at 20 Hz isn't that loud. The only help comes from room acoustics which tend to amplify low frequencies 10-20 dB and the placement of a sub can maximize the output at lowest frequencies. 20 Hz is more of a sensation of vibration sensed by body than a sensation of sound.

    Because of acoustic short circuit, bass reflex loudspeakers produce hardly any sound below reflex frequency (in your case about 40 Hz). You may even harm your speakers if you drive 20 Hz at high level into them.

    You can try blocking (very tight) the reflex ports with foam to make your speakers closed. This would reduce the bass response around 40 Hz, but increase a little under 35 Hz. If you don't like it, just remove the foam.
     
  4. bigshot
    In better recordings, there certainly is sub bass- classical music and jazz in particular. My sub gets as much of a workout with contemporary recordings as it does with movies. Music wouldn't sound the same without it.
     
    ev13wt likes this.
  5. Niouke
    alright thank you that's good info I'll digest it and may come back with more questions on monday.

    Actually I find the bass reponse of my setup quite satisfying. They are more bassy than the IEM's I own. I bought the speakers without hearing them first as they were at -40% and I just got lucky with the sizing against the room I believe.
     
  6. bigshot
    Sub bass isn't more bass. It's just a lower frequency range for the bass. The same as when you have a filter rolling off high frequencies. Sub bass is two octaves, so it isn't huge, but when it's there, you can hear it and feel it.
     
  7. gregorio
    That's not a question which can be easily answered, it depends on various factors. One factor for example is what sort of music do you listen to? The lowest note of any classical music instrument has a frequency of about 31Hz and that note is rarely composed. Exceptions would be the very bottom of an extended piano, a church/pipe organ and some very low rumble frequencies produced by an orchestral bass drum. So in general there's relatively little to gain if you listen to classical music or jazz. Rock based genres also have relatively little below about 40Hz of any musical consequence. Some of the electronic music genres can have content of consequence below 35Hz though.

    As a general rule, providing your speakers are pretty good down to 35Hz, then a sub will probably not provide substantial benefit and there's always the issue of a sub creating substantial acoustic problems. However, many speakers actually provide relatively poor performance below 50-60Hz, despite specs implying fairly decent performance down 35-40Hz, and if you ever play TV/Film through your speakers there is a far more substantial benefit to having a sub, particularly with action/adventure/sci-fi content.

    G
     
  8. bigshot
    I get benefit in having a subwoofer for classical and jazz music in particular. I have full range speakers, but the sub does a better job of defining plucked bass and tympani well, and the sub fills the room a lot better. It might not make as much of a difference in a small room. Subs aren't just for the bottom two octaves. With a crossover at 80Hz, relieving the mains of the 40 to 80 range goes a long way to guaranteeing a better response all the way down.
     
    Last edited: Oct 13, 2017
  9. Strangelove424
    Depends on what you listen to, and how much you value sub bass. It is rare in classical acoustic sources, but is an important component to pipe organs, so if you like fugues it is central. Outside of acoustic sources, you can also find it in electronic music and movie soundtracks. Though sub bass occupies an extreme of the audible spectrum, I find it to be a very enjoyable and important part of sound reproduction. It is one of the most tactile elements, a rumble or sense of pressure you can feel through your whole body. There is an immediate presence and power to it.

    A subwoofer is the only solution for a reasonable cost. It doesn't need to go below 20hz, that's really into infrasonic territory, but I think it should do atleast 20hz at no less than -3db or so. You can find a few budget subs that will perform excellently, I recommend something from Hsu, SVS, or KRK.
     
    Last edited: Oct 13, 2017
  10. bigshot
    I recently bought a multichannel SACD that had absolutely no content below 80Hz. My sub was stone silent when I played it. Reviews on the internet forums of the disc were glowing. To me, it sounds like the bass is chopped off at the neck. Perhaps when you listen to small speakers and headphones, you forget what bass sounds like. I'm curious... do any of the people here who say that subwoofers don't offer much for music listening actually own a subwoofer that they use for music listening? Because what is being said doesn't correlate at all with what I experience every time I fire up my stereo.
     
  11. 71 dB
    Is the disc 5.0 or 5.1 ?
     
  12. gregorio
    1. Yes, I do and in the majority of cases the difference is very little. In fact, on more than one occasion I've had my sub in bass managed mode when listening to a piece of music without even realising.
    2. How well that correlates to your experience depends on various factors. If, for example, your left/right speakers have relatively poor bass reproduction, then adding a sub should make a much more obvious difference (depending on room acoustics).

    G
     
  13. bigshot
    It was 4.0 and bass management was on. There was nothing under 80 on the whole disc. It seems that makes little difference to some people. The reviews all said the sound quality was spectacular. Maybe they just didn't know what a symphony orchestra is supposed to sound like.

    I'm thinking the size of my room is the reason my sub is so necessary. It's large with high ceilings. It takes a lot to fill it. I've got great JBL 15 inch drivers in the mains that are fine in most rooms, but it's much better with the sub helping out in this one. It also might be the music I listen to. I don't listen to a lot of 70s rock music engineered for the limitations of LPs. In recent orchestral music and stuff recorded very well back in the late 50s and 60s, there's plenty of sub 80 content, and a good amount of sub 40 too. My little Sunfire is small, but it kicks out a LOT of sound. It's always in bass managed mode unless multichannel overrides that. Perhaps some of you are using a lower crossover too. Mine is set to 80Hz.
     
    Last edited: Oct 14, 2017
  14. 71 dB
    That's interesting. What SACD is it?

    Lower crossover frequency gives stereo bass lower so I'd go as low as the main speakers can go with ease. If you have 15" drivers why not try 50 Hz?

    Sunfire is a wicked little cube! I remember measuring it for a hifi magazine 10-15 years ago.
     
  15. bigshot
    It was a Dutton Vocalion disc of Stokowski doing the Gotterdammerung Immolation Scene. There are other Dutton Vocalion SACDs I have that have the same problem.

    I've tried lower crossovers, but it was easier to balance the response at the crossover at 80Hz. The mains can go below 80 easily, but it starts getting harder to EQ down low.
     

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