how is it possible? - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 05, 2017, 04:09:41 am
content: I bought some new speakers for my computer on impulse, I was tired of looking at my '90s-styled "multimedia" PC speakers with the paper suspension speaker and telephone-quality sound.Got Creative T20s.Wow. How the hell can 2 inch woofers generate so much bass? OK I get it, it's not rattling the neighbor's plates like my Paradigm Monitor 5s in the living room, but it generates a lot of satisfying bass for something just barely larger than the 20 year old speakers.Is there some sort of new magical theory about ports or horns or what?Oh and had I known, I'd have sprung for the T40s right away!

author: amyk
author_rank: Super Contributor
timestamp: February 05, 2017, 06:53:41 am
content: Stiffer cones with longer travel will enhance bass.This happens more with the cheap Chinese unbranded/off-brand speakers, but I wouldn't be surprised if the amp inside was designed to boost the low frequencies much more too.

author: bobaruni
author_rank: Regular Contributor
timestamp: February 05, 2017, 07:39:40 am
content: This is a somewhat complicated topic but thanks to Thiele and Smallhttps://en.wikipedia.org/wiki/Thiele/SmallWe now understand how to measure, mathematically predict and therefore optimize bass reflex and sealed box design, this stuff was known decades ago.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 05, 2017, 10:01:25 am
content: Acoustic version of "electrically small antenna". Drive it harder, deal with the extra reactive power, and equalize it before the power amp. (In this case, it'll be more AC power to the speaker, since speaker efficiency is crap to begin with. DC power need not be too much higher, because a class D amp will recirculate whatever reactive power the speaker returns.)Tim

author: David Hess
author_rank: Super Contributor
timestamp: February 05, 2017, 03:09:47 pm
content: Quote from: Alex Eisenhut on February 05, 2017, 04:09:41 amIntermodulation distortion - lots of intermodulation distortion gives speakers that "boomy" sound.QuoteThere is nothing new under the sun except what manufacturers can get customers to accept. Build a couple of big critically damped bass reflex speakers and your windows will rattle before it sounds loud.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 05, 2017, 03:32:51 pm
content: Except it's not boomy. I was expecting that boomy muddy bass like on my full size Paradigms. I guess there's some sort of pre-distortion going on in the amplifier.It "thumps" more than I thought it would.I guess there's some reading I got to do somewhere.

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2017, 06:07:42 pm
content: Here is a more advanced explanation of how to get low frequency out of a small speaker, done properly:http://www.solusaudio.com/h-pasRead the text and watch the video if you like. BTW this guys small 7 inch speakers can knock you out of your seat /with a VLF breeze with only 100 watts.

author: Fungus
author_rank: Super Contributor
timestamp: February 05, 2017, 07:57:07 pm
content: Something has to give but without listening to them it's hard to say what.They may just be boosting the bass by a ridiculous amount in the amplifier and moving the cones a long way. If you tune the boxes to 50Hz(ish) it will sound alike a lot of bass if you're close up. If you stand a bit further away you'll notice a massive 50Hz peak in the frequency response.That's what most mini-HiFi systems do. It sounds horrible once you know what to listen for.

author: David Hess
author_rank: Super Contributor
timestamp: February 05, 2017, 09:23:28 pm
content: Quote from: Fungus on February 05, 2017, 07:57:07 pmI agree. People are so used to boomy or in the case of Alex Eisenhut, thumpy bass, that it has become the standard sort of like "east coast" versus "west coast" sound.I first really noticed this with a home theater system that had 10" woofers in individually tuned base reflex enclosures while watching Aliens; the drop ship scene was not "loud", but it was shaking the room and windows. Tuning an enclosure can be done with a low frequency oscillator and AC voltmeter; adjust the combined resonance peaks to produce two roughly equal peaks by monitoring the impedance.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 05, 2017, 09:50:53 pm
content: Well, it *is* difficult to convey in words what I'm hearing, like Zappa said, it's like dancing about architecture.

author: amyk
author_rank: Super Contributor
timestamp: February 06, 2017, 01:23:12 am
content: Quote from: David Hess on February 05, 2017, 09:23:28 pmI guess there is now a standard "far east sound" --- extreme bass with almost no treble.It's easy to see why "bass sells" --- if you put a bunch of different speakers together, the majority of the common people are going to pick the one with the loudest and most "powerful" sound, which means boomy, physically-felt bass rather than the tinny, ear-piercing shrill squeals you'd get with the same power levels but at higher frequencies.After all, there's an overpriced brand called Beats, not Shrieks...

author: xavier60
author_rank: Super Contributor
timestamp: February 06, 2017, 02:46:54 am
content: I am always amazed by how pleasant the HK speakers on my Toshiba laptops sound with their 15mm diaphragms. There is noticeable fundamental output at 150Hz and the rest of the response is acceptable with a few slight resonances.There is enough bass to make speech sound natural.

author: Someone
author_rank: Super Contributor
timestamp: February 06, 2017, 04:35:24 am
content: Quote from: Alex Eisenhut on February 05, 2017, 04:09:41 amAre you in the nearfield? Performance can be exceptional close in.

author: mikerj
author_rank: Super Contributor
timestamp: February 07, 2017, 02:15:39 pm
content: Quote from: T3sl4co1l on February 05, 2017, 10:01:25 amExactly this. More powerful amp and lots of equalisation to compensate the natural roll off of the speaker at low frequencies. The small "under seat" sub units for cars use exactly the same scheme, though it can only go so far. Needs to be a sealed cabinet rather than ported since low frequency roll off in a reflex design is much steeper and ridiculous cone excursions would be needed. The driver cone and suspension needs to be physically strong since quite high pressures can be generated within the cabinet.

author: Fungus
author_rank: Super Contributor
timestamp: February 07, 2017, 05:13:46 pm
content: Quote from: amyk on February 06, 2017, 01:23:12 amMost people also want something small that fits on a shelf instead of huge speakers that take up half the room. I think manufacturers have responded to this which has lead to all the crappy 50Hz-tuned systems out there.Remember that there's no perfect speaker. Small speakers have more detail and stereo image, big speakers have more bass. Choose your poison.Me? I prefer small speakers near the center of a room and sit quite close to them to hear the bass (ie. 'nearfield' listening).Big speakers near a wall sound much too thumpy/muddy to me. To put speakers against a wall you really need to put good sound-absorbing material behind them. Double-thickness material if you put them in corners.

author: David Hess
author_rank: Super Contributor
timestamp: February 07, 2017, 08:08:22 pm
content: Quote from: mikerj on February 07, 2017, 02:15:39 pmEqualization by itself is not sufficient compared to a bass reflex design.The problems include large signal non-linearity in the cone travel which causes intermodulation distortion and separately FM modulation when multiple tones are handled by the same cone. The former is solved by lowering the impedance seen by the transducer which minimizes linear travel and the later by using multiple speakers covering different frequency ranges.You can visibly see the effect in a base reflex versus infinite baffle enclosure. In the former, the cone movement *decreases* at the tuned resonate frequency because the speaker is now effectively using both sides. Less movement makes it more linear producing less intermodulation and the FM distortion is also minimized.You identified the disadvantage of doing this though. While the low frequency cutoff is lower for a bass reflect design, the slope of the roll off is twice as steep.Quote from: Fungus on February 07, 2017, 05:13:46 pmThen they either were not tuned correctly or the wall interfered with the port on the back which is a good reason to put the port on the front. I had never looked but I bet someone has tried to make a rear ported enclosure designed to use a wall corner as part of the tuning. Downward facing subwoofers have the advantage of legs holding them a prescribed distance from the floor.

author: retrolefty
author_rank: Super Contributor
timestamp: February 07, 2017, 09:04:38 pm
content: Quote from: Alex Eisenhut on February 05, 2017, 09:50:53 pmIt's the same problem 'golden ears' have trying to justify the costs of their choices in electronics/speakers.

author: David Hess
author_rank: Super Contributor
timestamp: February 07, 2017, 11:09:08 pm
content: Quote from: retrolefty on February 07, 2017, 09:04:38 pmI do not worry about it too much. A signal generator and voltmeter can make an objective measurement of the base reflex tuning just like I can push on the bumper of a car and observe the step response to determine that the shock absorbers (dashpots) are shot. Remedy the easily fixed big things before the difficult to fix minor things.Beyond that, while large signal mechanical transducers produce most of the distortion, remedying it is so difficult that it is hardly worth it and they are good enough especially considering things like theLoudness War.

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: February 08, 2017, 03:10:10 am
content: I have the Creative T40 Series II's. They do sound very good, even at various points in the room. Much clearer lows and highs compared to most computer speakers. The drivers do move quite a bit on bass, and you can definitely feel the displacement through the port on the top.The only issue I've had with them is some resonant/droning type noise with Metallica's ...And Justice for All. It's the only album I've found that upsets the speakers, but I have heard that adding speaker fluff/dampening inside the cabinet helps.