I was wondering if anyone has built and M&K style subwoofer?
An externally hosted image should be here but it was not working when we last tested it.
A 2 woofer sub that uses push-pull to reduce 2nd harmonic distortion — not an issue if you use decent woofers.
If you have 2 woofers for your box i feel you are way ahead loading the drivers in a tightly coupled push-push pair — the active reactive force cancellation dramatically reduces box load which makes it alot easier to build (& lift) the box.
This sketch does not how the necessary coupling between the drivers — i usually just put a tight brace between the magnets, but one can go over the top (see the illustration at the bottom: toobz woofer
dave
If you have 2 woofers for your box i feel you are way ahead loading the drivers in a tightly coupled push-push pair — the active reactive force cancellation dramatically reduces box load which makes it alot easier to build (& lift) the box.
This sketch does not how the necessary coupling between the drivers — i usually just put a tight brace between the magnets, but one can go over the top (see the illustration at the bottom: toobz woofer
dave
Have a look at PPSL type enclosures.
Push pull slot loaded boxes have two woofers loaded into a small cavity with one reversed to try to significantly reduce distortion from the drivers by eliminating the difference between front/rear magnetic and suspension asymmetry.
Those who have built them swear by them.
Push pull slot loaded boxes have two woofers loaded into a small cavity with one reversed to try to significantly reduce distortion from the drivers by eliminating the difference between front/rear magnetic and suspension asymmetry.
Those who have built them swear by them.
Patrick is right, second-order harmonics is not harmful to the ear, what is more, it often leads to imporvements in bass reproduction - bass is warmer, richer, etc. The real problem is third-order haromonics resulted from BI product and suspension mechanical limitations and it should be avoded as hell. This is not so easy as to place two drivers together. This type of distortion audibly compress bass impact and along with various acoustical mis-alignments deffinitely is the source of complaints that my bass is 'not that fast as it could be'.
EDIT: Low-distortion drivers do not sound weird. They sound RIGHT. We are not used to fair sound reproduction. It often gets better with high SPL level close to real sound sources. High SPL & low distortion together is a real pain to achieve with typical playback systems.
EDIT: Low-distortion drivers do not sound weird. They sound RIGHT. We are not used to fair sound reproduction. It often gets better with high SPL level close to real sound sources. High SPL & low distortion together is a real pain to achieve with typical playback systems.
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Well, traditionally folks have argued that second harmonics are at least somewhat musical and perhaps as judged by ear. Watching sine waves on a 'scope as you raise a signal to distort it supports that impression too. Does anybody know any research related to how much is OK and/or compared to odd-order harmonics?
Went to a "Mike and the Mechanics" show last night in Fort Lauderdale.* Nice show, but I bet their music would sound absolutely unappealing if they had low distortion subs (at least to their audience's taste).
How do you make recordings of such groups? Do you take the relatively clean contact mic signals and add crap at the recording consoles or do you record the sound coming from their gawd-awful "musical instrument speakers"?
But as for playing Mahler at home, think I'll stick with the cleanest speakers I can make. And I leave it as an exercise for the reader to consider how to record the system used on-stage when the bird recordings are played during Respighi's famous piece.
B.
*with NR35 earplugs and smartphone SPL meter.... 112dB(MotoG phone)... in case you are wondering, one of the musicians is a cousin
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My understanding is that the point of low distortion speakers is to make sure one is not adding additional distortion to whatever is in the recording - the artist can record whatever they like, but we don't want to add to it.
112dB, though? Not sure how that accords with Health & Safety guidelines of, what, a couple of minutes at 'only' 85ish dB?
No one can dispute your pious if naive homily. But the question is how to reproduce the experience of hearing Mike and the Mechanics in your modest music room... unless the notion itself is so ridiculous as to not bear deeper consideration.
Is that best accomplished (as earlier posters have suggested) by having unclean speakers with a bit of distortion (as the recording engineer prolly believes) or by having the kind of speakers the band uses (heaven forbid) or by having perfect speakers (as MemX implies)?
(But the question you missed entirely is how the signal to your speakers is produced. For example, by cramming the band and their speakers in a little dead studio and recording it with a mic?)
B.
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1) Klipple has done lots of research into the subject, and you can determine your own sensitivity to a variety of distortions with this double blind test and compare it to others results:
Listening Test
That said, I can't get the test to work anymore since various "updates" to my computer now seem to have rendered it useless. Previously I had found it difficult to reliably detect distortion less than 10% on the music tracks, but could detect around that level on LF sine wave tones.
When testing push pull subs, which lower even order distortion, I found that at high distortion levels, the lack of even order with the remaining odd order distortion sounded "odd". While in the driver's linear range, with typical pop music, I could not notice a difference.
The reason being:
2. There are plenty of harmonics present in pop group's musical output without needing to rely on additional distortion added by the reproduction system. Groups like "Mike and the Mechanics" are at a level where the system provider will bring enough rig for the gig, sub distortion would be less than most home systems, though your home system may not be capable of 112 dB at your listening position.
Decent subs and headphones have low distortion levels, the low frequency on "All I need is A Miracle" sounds fine at levels that I have measured to be under 1% THD.
3. Most pop groups guitars and bass are recorded with the sound of the musical instrument amplifier speaker, though bass will often be a mix of direct sound from the pickup and the speaker output. Tube compressors or digital emulation of their "good sounding" distortion is often used for bass and vocals.
Kick drums often use dual mics (dynamic and condenser) and the mixed sound is then noise gated and processed with a variety of effects to shape the harmonics and dynamics to sound like what ever is currently popular to the engineer. Most rock kick drums, live or recorded, sound very little like the drum.
Keyboards now have samples of the sound of "classic" distortion like Fender Rhodes vibrato cabinets, Hammond/Leslie combinations, and digital emulations of harmonic-rich analog synthesizers sounding like Moogs or Arps, with which you could "dial in" the waveforms. Since the samples sound so much like the "real thing", their direct outputs are replacing the classic keyboard instruments and amps.
In some respects, the harmonic richness of the era when bands often had 20 or more players has evolved (or devolved) to 5 or so rock musicians using 4 times the distortion to achieve similar levels of harmonics.
Cheers,
Art
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Thanks. Very nice of you to post such good information.
So, just like Art's engineer, a distorted speaker would be OK if it introduced sounds that were supportive of the character of an instrument. But then no speaker could introduce distortions that were characteristic of any and all instruments.
Sounds kind of like my 1957 Karlson-15 that was an absolutely uncanny speaker for cellos.
So the take-away is that uncoloured "East Coast sound" speakers are best.
B.
So, just like Art's engineer, a distorted speaker would be OK if it introduced sounds that were supportive of the character of an instrument. But then no speaker could introduce distortions that were characteristic of any and all instruments.
Sounds kind of like my 1957 Karlson-15 that was an absolutely uncanny speaker for cellos.
So the take-away is that uncoloured "East Coast sound" speakers are best.
B.
Ben,
Most instruments have both even and odd order harmonics, and decent speakers have progressively less higher order harmonics, so for most music the distortion added by speakers played out of their linear range is not terribly objectionable until Frank Sinatra starts to sound like Joe Cocker ;^).
Karlson cabinets do have a sound of their own!
If by "East Coast Sound" you mean the sound of acoustic suspension sealed box speakers characterized by 1970's and 1980s Acoustic Research, Boston Acoustics, and KLH, they were fine for listening to at polite levels, but not capable of reproducing the SPL of live rock or big band dynamics. If one had enough clean power to attempt to reproduce concert levels with those speakers (when inflation adjusted power cost was around $10 to 20 per watt), the driver's voice coils would burn up before distortion was particularly objectionable even in the days when recordings had twice the dynamic range of much of the stuff mixed now.
Art
Most instruments have both even and odd order harmonics, and decent speakers have progressively less higher order harmonics, so for most music the distortion added by speakers played out of their linear range is not terribly objectionable until Frank Sinatra starts to sound like Joe Cocker ;^).
Karlson cabinets do have a sound of their own!
If by "East Coast Sound" you mean the sound of acoustic suspension sealed box speakers characterized by 1970's and 1980s Acoustic Research, Boston Acoustics, and KLH, they were fine for listening to at polite levels, but not capable of reproducing the SPL of live rock or big band dynamics. If one had enough clean power to attempt to reproduce concert levels with those speakers (when inflation adjusted power cost was around $10 to 20 per watt), the driver's voice coils would burn up before distortion was particularly objectionable even in the days when recordings had twice the dynamic range of much of the stuff mixed now.
Art
Thank you!112dB, though? Not sure how that accords with Health & Safety guidelines of, what, a couple of minutes at 'only' 85ish dB?
Thank you for relating your experiences, Art - they are always a pleasure to read
Revisiting your previous questions, NIOSH is more stringent than OSHA, which permits 90 dBA SPL (slow response) for up to 8 hours, 110 dBA for a half hour. Both NIOSH and OSHA use "A" scale, which progressively rolls off (ignores) low frequency response below 1kHz, down about 30 dB at 50 Hz.
With the 10-20 dB LF "haystack" common in concerts, one could read a USA permissible noise exposure of 90 dBA (Slow) with actual LF levels still reaching well over 120 dB (unweighted, flat) peak response.
Phone app SPL meters generally become inaccurate above 110 dB because of microphone clipping around that level.
Art
That seems... loud... lol
I'm amazed people standing at the front of concerts have any hearing left whatsoever!!
Standing directly in front of stage at a rock concert is loud, and does cause hearing loss given enough exposure.
Low frequency (<100 Hz) level is not responsible for typical noise induced hearing loss (NIHL).
NIHL is centered around 4kHz, also the frequency band that hearing is most sensitive on average.
My early DYI days in the shop with no hearing protection, too many high speed miles with the windows down, and too many 120+ dB shows (at the mix location!) back then took their toll. The noise exposure has left me with around a 50 dB "hole" at 4kHz (slightly differing frequencies L/R) but the rest of my hearing is normal for my age group.
Unfortunately, the 4kHz band has the fricatives needed to distinguish many words from each other, conversation in noisy rooms is difficult over a few feet away.
I am getting progressively better at reading lips ;^).
Cheers,
Art
For me, it was too many shitty bar gigs, with insane drummers and much-too-small stages. I've had 18" crash cymbals practically cut my hair.
After my left ear "retired." the suitcase Rhodes and Porta-B did my back in.
Ah, the life of a musician!
A 2 woofer sub that uses push-pull to reduce 2nd harmonic distortion — not an issue if you use decent woofers.
If you have 2 woofers for your box i feel you are way ahead loading the drivers in a tightly coupled push-push pair — the active reactive force cancellation dramatically reduces box load which makes it alot easier to build (& lift) the box.
This sketch does not how the necessary coupling between the drivers — i usually just put a tight brace between the magnets, but one can go over the top (see the illustration at the bottom: toobz woofer
dave
Why do you want to mechanically couple them?
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