Hmmm...
Right, I'm going to assume a little knowledge of physics here, but I'll try to keep it simple.
Speakers, fundamentally, work by converting electrical energy into air pressure, which then propagates across the room to our ears.
When the speaker cone moves forward, toward your ears, it makes positive pressure immediately in front of the cone. By the same argument, there's negative pressure behind the cone - the cone has moved away from where it used to be, making a small amount of suction.
If we leave it at that, the positive pressure will rush around to meet the negative pressure, and cancel out perfectly. That only happens at zero Hertz (Hertz = number of complete cycles per second, one movement outward, one movement inward) - the cone is forward, and stays there indefinitely.
Music consists of lots and lots and lots (you get the idea) of sine waves. Fourier theory tells us that. So, for each note, there's an associated oscillation of the speaker cone. Forwards, backwards, forwards, backwards.
In front of the cone: positive pressure, negative pressure, positive pressure, negative pressure.
Behind the cone: negative pressure, positive pressure, negative pressure, positive pressure.
Right. If the cycle is suitably slow (ie, a low frequency), most of the positive pressure will be able to rush around, meet the negative pressure, and cancel it out. We call these dipole losses. At lower frequencies, there's more cancellation, as the two pressures effectively have a longer time to meet.
The wavelengths of sound range from very short (10kHz=3.4cm), to very long (100Hz=3.4m, and that's not a particularly low frequency).
We can relate the low frequency performance of a dipole loudspeaker to the "path difference" between the two sources (positive and negative, each side of the cone): the maths gets a bit complicated (check LinkwitzLab for more), but here's an equation: the low-frequency rolloff starts at 172/D, where D is the path difference in metres.
For your baffle-less 8" speaker, that's 860Hz.
You'll need to boost 6dB per octave below that.
A decibel is a weird logarithmic unit that makes a lot of sense for sound. We can just about hear a 1dB change in level. 3dB is quite obvious, and 10dB sounds like it's doubled or halved in volume. 3dB is double power, so 6dB is quadruple power, and 10dB is 10x the power.
An octave is a double or half of a frequency: an octave up from 100Hz is 200Hz.
So, lets say we want reasonable low-frequency performance from your baffle-less speaker, and we'll aim for 53.75Hz (you'll see why in a moment).
Going from 860Hz to 430Hz at the same volume needs +6dB, so that's 4x power from, say, 1w nominal input.
So that's 4w.
Next, 215Hz puts us to 16w.
107.5Hz means 64w
53.75Hz means 256w.
So if the driver would normally put out 89dB@1w@1m, it'd need 256w input to hit 53.75Hz at the same 89dB.
That much power will...
1 - burn out the speaker
2 - mechanically destroy the speaker - the cone will fling itself onto your floor
Does this sound good?
https://www.youtube.com/watch?v=q_zTpqZBok4
If you're happy with very very limited sound levels (say, 70dB, maximum), you might get away with a baffle-less speaker - the power would scale down to only a couple of watts input at low frequencies, but you'd still need to sit close to get any volume out of it. That'd be less than ideal.
My advise would be to either...
1 - use a baffle (increasing D would mean less power at low frequencies)
2 - use a box (a whole new set of things to calculate, but power requirements drop considerably)
Feel free to ask any questions you like. The stupid questions are the ones you wish you'd asked, before you let the smoke out of something.
HTH
Chris
Right, I'm going to assume a little knowledge of physics here, but I'll try to keep it simple.
Speakers, fundamentally, work by converting electrical energy into air pressure, which then propagates across the room to our ears.
When the speaker cone moves forward, toward your ears, it makes positive pressure immediately in front of the cone. By the same argument, there's negative pressure behind the cone - the cone has moved away from where it used to be, making a small amount of suction.
If we leave it at that, the positive pressure will rush around to meet the negative pressure, and cancel out perfectly. That only happens at zero Hertz (Hertz = number of complete cycles per second, one movement outward, one movement inward) - the cone is forward, and stays there indefinitely.
Music consists of lots and lots and lots (you get the idea) of sine waves. Fourier theory tells us that. So, for each note, there's an associated oscillation of the speaker cone. Forwards, backwards, forwards, backwards.
In front of the cone: positive pressure, negative pressure, positive pressure, negative pressure.
Behind the cone: negative pressure, positive pressure, negative pressure, positive pressure.
Right. If the cycle is suitably slow (ie, a low frequency), most of the positive pressure will be able to rush around, meet the negative pressure, and cancel it out. We call these dipole losses. At lower frequencies, there's more cancellation, as the two pressures effectively have a longer time to meet.
The wavelengths of sound range from very short (10kHz=3.4cm), to very long (100Hz=3.4m, and that's not a particularly low frequency).
We can relate the low frequency performance of a dipole loudspeaker to the "path difference" between the two sources (positive and negative, each side of the cone): the maths gets a bit complicated (check LinkwitzLab for more), but here's an equation: the low-frequency rolloff starts at 172/D, where D is the path difference in metres.
For your baffle-less 8" speaker, that's 860Hz.
You'll need to boost 6dB per octave below that.
A decibel is a weird logarithmic unit that makes a lot of sense for sound. We can just about hear a 1dB change in level. 3dB is quite obvious, and 10dB sounds like it's doubled or halved in volume. 3dB is double power, so 6dB is quadruple power, and 10dB is 10x the power.
An octave is a double or half of a frequency: an octave up from 100Hz is 200Hz.
So, lets say we want reasonable low-frequency performance from your baffle-less speaker, and we'll aim for 53.75Hz (you'll see why in a moment).
Going from 860Hz to 430Hz at the same volume needs +6dB, so that's 4x power from, say, 1w nominal input.
So that's 4w.
Next, 215Hz puts us to 16w.
107.5Hz means 64w
53.75Hz means 256w.
So if the driver would normally put out 89dB@1w@1m, it'd need 256w input to hit 53.75Hz at the same 89dB.
That much power will...
1 - burn out the speaker
2 - mechanically destroy the speaker - the cone will fling itself onto your floor
Does this sound good?
https://www.youtube.com/watch?v=q_zTpqZBok4
If you're happy with very very limited sound levels (say, 70dB, maximum), you might get away with a baffle-less speaker - the power would scale down to only a couple of watts input at low frequencies, but you'd still need to sit close to get any volume out of it. That'd be less than ideal.
My advise would be to either...
1 - use a baffle (increasing D would mean less power at low frequencies)
2 - use a box (a whole new set of things to calculate, but power requirements drop considerably)
Feel free to ask any questions you like. The stupid questions are the ones you wish you'd asked, before you let the smoke out of something.
HTH
Chris
Hi,
The very short answer is a baffleless speaker sounds appalling
and a subwoofer cannot fix the ensuing hideousness. Put it in
a small box if you cannot handle the right sort of baffle sizes.
Choose your driver properly for purpose. 4" in a box will
cream a 8" baffleless to integrate with a subwoofer.
rgds, sreten.
The very short answer is a baffleless speaker sounds appalling
and a subwoofer cannot fix the ensuing hideousness. Put it in
a small box if you cannot handle the right sort of baffle sizes.
Choose your driver properly for purpose. 4" in a box will
cream a 8" baffleless to integrate with a subwoofer.
rgds, sreten.
Note that the "box" does not need to be box-shaped. Eg. Orb, Gallo, Overkill Audio, Joey Roth (who uses TangBand), B&W Nautilus etc.
With that driver and 15" deep wings on an open baffle, there was no bass (in a big room, not in a corner).
He's right, by boosting the bass needed (especially running it wide open on no baffle), the voice will sound like someone is gargling.
I think that is a good driver, but pricy for needing equalization (or a notch circuit minimum) and lack of dispersion from (my opinion) the relatively deep cone.
You can play with the betsy drivers for 1/2 the cost, and they have a floppier qts (better for open baffle).
Norman
He's right, by boosting the bass needed (especially running it wide open on no baffle), the voice will sound like someone is gargling.
I think that is a good driver, but pricy for needing equalization (or a notch circuit minimum) and lack of dispersion from (my opinion) the relatively deep cone.
You can play with the betsy drivers for 1/2 the cost, and they have a floppier qts (better for open baffle).
Norman
Well I certainly don't want 1 or 2 to happen from above!
I hope I'm using the right terminology, open baffle means open backed right?
I'm hearing about how great full range open backed speakers can sound and the Tang Band was highly rated.
Check out this link, they are selling the Tang Band with two 50 dollar woofers below it, (no amp) for 2000 Euro or 2700 dollars in an open plywood box!
PureAudioProject | Open Baffle sets, speakers and drivers
I've since looked up the Wild Burro site. Interesting and a Q of .7 so that's good right? I saw them recommended somewhere else also. Maybe I don't have to spend 200 for a good driver.
There has to be some advantages to an open back crossoverless design right? There's some pretty nice headphones on the market that utilize this idea and aren't Planar's and Eletrostatics similar. I don't mind building an enclosure if I have to. That's not a problem, just hearing about the amazing imaging and soundstage of the open design??
I hope I'm using the right terminology, open baffle means open backed right?
I'm hearing about how great full range open backed speakers can sound and the Tang Band was highly rated.
Check out this link, they are selling the Tang Band with two 50 dollar woofers below it, (no amp) for 2000 Euro or 2700 dollars in an open plywood box!
PureAudioProject | Open Baffle sets, speakers and drivers
I've since looked up the Wild Burro site. Interesting and a Q of .7 so that's good right? I saw them recommended somewhere else also. Maybe I don't have to spend 200 for a good driver.
There has to be some advantages to an open back crossoverless design right? There's some pretty nice headphones on the market that utilize this idea and aren't Planar's and Eletrostatics similar. I don't mind building an enclosure if I have to. That's not a problem, just hearing about the amazing imaging and soundstage of the open design??
A whole pile of back-horn loaded speakers would beg to differ!
<offtopic>
(I'll see your .454 and raise you a .458 SOCOM - I love those "wildcats")
</offtopic>
Yes, the dynamics of an open baffle (OB) are very appealing because there is no reflected back wave to mess with the sound coming from the cone and the impulse response is very clean and tight. The back wave reflected from walls then gives added ambience to the sound making it sound more like 'live' music. If you want to experience OB sound just to see if you like it, try mounting some full range drivers in a large sheet of cardboard about 24 in wide x 3 feet tall, place it at least 4 ft from back wall and listen to the mids and highs as there is no bass. But the ambience and dynamics will be there and you don't need wood to experience the sound before committing to a wood build. For bass in an OB the extension is very limited due to front and back wave cancellation and serious EQ'ing and xmax are needed in 15 inch plus woofers to get any real bass. You need some baffle though if it is open backed otherwise the front and back waves cancel and the cone is acting like a blender rather than a piston. It is possible to have very small enclosures - the smallest would be a sealed back midrange used in PA cabinets. No baffle needed but no bass either (maybe 400 Hz). A sphere, gourd shape, tear drop, or a compact snail like spiral are all good designs that minimize the reflected back wave from reaching the cone again.
If you want clean dynamics and no reflected box like sound from back wave, an enclosure that absorbs the back wave like the Nautaloss will give the same measured frequency response and impulse response as an OB. The only difference is the lack of rear wave 'ambience' which may or may not be a bad thing. The Nautaloss is much more compact and easy to place than an OB.
Using a sealed subwoofer IMO, is a much more compact way to achieve the dynamics of an OB woofers with a much reduced size. Again, the difference being the lack of a reflected back wave to give ambience and a dipole sub is not as subject to room effects like a monopole sub. Disadvantage is need for EQ, high xmax, large size, and very low WAF.
The Betsy is a highly regarded driver for OB. Large dia full range drivers suffer from 'beaming' though (very directional). If you want a proven OB design that is rather cost effective, check out the Manzanita which uses a Vifa TC9FD as the tweeter and a rather complex crossover. The same drivers can be driven with a lower cost bi amp and miniDSP solution that can be tailored to your in-room effects.
Good luck.
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Thanks for the encouragement! Yes that live sound is what I am after. It was a while ago I stumbled into a store that used to be in Phx called Audio Nut, I think it's gone now, but the guy was very nice and happy to fire up his Magico's. Wow, it was a jaw dropping experience hearing that 50k speaker. It was so real it was like my mind's eye was trying to put together the band. I've since taken my son to LMC Home Entertainment , also here in Phx, for some decent headphones, and the salesman was also happy to oblige us with his wares. To tell the truth though I couldn't tell much difference between the inexpensive, relatively speaking, Lynn Audio set and the Wilson's we heard. They both sounded amazing. So I started wondering how I could put together something inexpensively that might fill the bill. I've also discovered, since I've been listening to headphones lately, that you don't have to spend a lot to get good sound, and that out of a tiny full range driver! But I'm missing the dynamics that speakers offer.
So since I don't have the technical background I figured I'd start with some good full range drivers and play around. I don't listen to music at terribly high volumes either and I've always been a fan of a good powered sub too (btw I hear Creative Sound has some excellent ones?) so it seemed a good way to get started. Thanks again for the recommendations.
So since I don't have the technical background I figured I'd start with some good full range drivers and play around. I don't listen to music at terribly high volumes either and I've always been a fan of a good powered sub too (btw I hear Creative Sound has some excellent ones?) so it seemed a good way to get started. Thanks again for the recommendations.
Hi Dave, if WAF is not an issue and space is available. I have tried the Audio nirvana 12 in open baffle with 15 hawthorne audio augies for the bottom and they are pretty good. I have read and have spoken with a guy that uses the 15 audio nirvana in open baffle and loves it. I think jumping on the audio nirvana 15 will make for good long term investment. Check out glowinthedarkaudio for some info.
Hi Dave, if WAF is not an issue and space is available. I have tried the Audio nirvana 12 in open baffle with 15 hawthorne audio augies for the bottom and they are pretty good. I have read and have spoken with a guy that uses the 15 audio nirvana in open baffle and loves it. I think jumping on the audio nirvana 15 will make for good long term investment. Check out glowinthedarkaudio for some info.
" if someone says baffleless"
then I would think he/she's wise.
Making something with a decreasing angle/surface like the Olson (?) studies of the fifties of the past century and the kind-of-showing the response at the step impulse with a cleaner "curve" with less "composites" that happen to be due to the fact that any baffle is firstly reflective so it makes a "compound" together with the driver & associated lengths.
then I would think he/she's wise.
Making something with a decreasing angle/surface like the Olson (?) studies of the fifties of the past century and the kind-of-showing the response at the step impulse with a cleaner "curve" with less "composites" that happen to be due to the fact that any baffle is firstly reflective so it makes a "compound" together with the driver & associated lengths.
The WAF would be quite low I think on the Nirvana set. Not sure how low, but I'm guessing the formula goes something like this: WAF is inversely proportional to the size, plus cost of project plus quality of bass output. It sounds like a lot of fun though, as they say there's no substitute for displacement right. I bought some 5" full range Tang Bands to play around with and the budget beater Pioneer knock off 8" to start with. Hurry parts express!! The first order of business is to find the most elegantly simple way to give them great sound while not resorting to placing them in the middle of the room behind or behind an inordinately large piece of plywood. And by great sound I'm primarily focusing on a live 3D sound at a reasonable volume (most speakers sound pretty live to me at high volumes). What do you serious audiophiles call it, "soundstage," or "imaging?" If that means going open, or wings, or using foam board I'll give those a try. The 2nd order of business will be a good powered sub (for when the wife is shopping) that will make them really come alive.
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