Round vs Oval shape

[ColdPlays]

If you use a Round shaped speaker, you get a perfect sinus when you measure the outcome of a wave.

- What happens when you use an oval shaped speaker? Is the 'shockwave' still a perfect sinus? I need to know because I'm experimenting with sound behaviour. A right awnser would help me alot.

thx

ColdPlays

[GMichael]

Welcome to AR,

I'm no expert, but it would seem to me that an oval would not have perfect symmetry and therefore add some level of distortion. Build quality may be a bigger factor than shape though. Some oval drivers (such as KEF uses) may be better than some other's round. And the oval shape will let you get more surface area into a thinner form.
Hope this helps for now. I'm sure that others will be along to add or correct.

Mike

[Auricauricle]

Yeah, but now that we're digital, don't we need square speakers?

[GMichael]

Yeah, but now that we're digital, don't we need square speakers?

I have a rectangular driver. Does that count?

[ColdPlays]

I have a rectangular driver. Does that count?

Sure! Why not? :rolleyes: :)

Anyways. Couple of things: Is there any difference in frequency range between the two?
What I mean is: Are oval speakers capable of producing clear sound between 0 and 250 Hz?

Thx

ColdPlays

[Auricauricle]

Are oval speakers capable of producing clear sound between 0 and 250 Hz?

I think that's something for you to know and for us to find out....

Unless yer talking about clear and distinct distortion and the ability to measure deviation of signal that can be graphically represented, clarity is a matter of the ears of the beholder.

Could be outta line, but that's the way I see it now....:ihih:

[GMichael]

Sure! Why not? :rolleyes: :)

Anyways. Couple of things: Is there any difference in frequency range between the two?
What I mean is: Are oval speakers capable of producing clear sound between 0 and 250 Hz?

Thx

ColdPlays

Capable? Sure. A 6x9" oval should be able to go lower than a 6" round. But again, it depends on who's making them and how they're built. Check the specs and give them a listen. There is little reason to exclude oval as an option if it helps you to get more surface area in the space you require them to be in. But if I had the space, I'd choose an 8" round over 6x9 oval. (all other things being equal)

Building something?

[kexodusc]

Sure! Why not? :rolleyes: :)

Anyways. Couple of things: Is there any difference in frequency range between the two?
What I mean is: Are oval speakers capable of producing clear sound between 0 and 250 Hz?

Thx

ColdPlays

0-250 Hz? Well, that's gonna take some work, but it could be done. The shape has less to do with sound clarity in woofers at those low frequencies than other factors. Frequency range is also dictated more by the cone material, mass, and compliance of the suspension than shape. Our ears aren't very sensitive to distortion below 100 Hz at all so you can get away with higher distortion to a point, but too much distortion at too low a frequency and the harmonic distortion becomes louder and more audible than the fundamental frequency itself.

I think an oval shape driver would result in a bit more distortion but probably not enough to really matter at those frequencies.

[Auricauricle]

I remember square speakers produced by Sony at one time or another. Mebbe I was put off by their appearance or soething, but they just didn't sound right....Shoulda done a blind A-B, but that's retrospect fer ya...

[kexodusc]

To be honest, an oval can be an inefficient design for woofers - for a given surface area ( think cone material) the circle maximizes the area (which leads directly to swept volume, SPL, efficiency) whereas a cone could use the same amount of material and end up with less area, and less volume output.

Also when moving, the oval woofer would experience an uneven friction and resistance from the air mass across its surface area, which could only lead to irregular movement or force applied against the cone mass - I'm sure it could be mitigated with consideration to concavity but that's a lot more work for less benefit already...

Edit: I know with car audio, oval woofers are an acceptable compromise to increase surface area in a restricted 2 dimensional area, ie, more width than length to work with.

[basite]

I remember square speakers produced by Sony at one time or another. Mebbe I was put off by their appearance or soething, but they just didn't sound right....Shoulda done a blind A-B, but that's retrospect fer ya...


oh, you mean the APM series?

check www.thevintageknob.org for more information on them btw :)

never heard them, but they were a little different in design from the square designs used today (all of them are in car audio, I presume they think it looks cool or so...), and from the oval designs...

the sony's were different, regular drivers use 1 magnet, in the center of the driver, so the voicecoil pushes the driver forward, so it's 'balanced'
the sony's had 5 magnets & 5 voicecoils, (or 4...) one around each corner, and one in the middle too with larger drivers. So the pressure was about the same everywhere on the driver...

this is, I think, where oval drivers could introduce more disortion (when bad designed), ther would be no difficulties if the driver had a oval voicecoil & magnet (the whole thing would have to be oval, not just the cone...), but this is almost impossible. So they use round systems, in this case the sides have less resistance from the surrounds than the top & bottom of the driver, so the drivers are more prone to disortion...

(I think...), I know it isn't that well explained, but somehow I found this to be more difficult in English than in Dutch (my native language...)

Keep them spinning,
Bert.

[GMichael]

oh, you mean the APM series?

check www.thevintageknob.org for more information on them btw :)

never heard them, but they were a little different in design from the square designs used today (all of them are in car audio, I presume they think it looks cool or so...), and from the oval designs...

the sony's were different, regular drivers use 1 magnet, in the center of the driver, so the voicecoil pushes the driver forward, so it's 'balanced'
the sony's had 5 magnets & 5 voicecoils, (or 4...) one around each corner, and one in the middle too with larger drivers. So the pressure was about the same everywhere on the driver...

this is, I think, where oval drivers could introduce more disortion (when bad designed), ther would be no difficulties if the driver had a oval voicecoil & magnet (the whole thing would have to be oval, not just the cone...), but this is almost impossible. So they use round systems, in this case the sides have less resistance from the surrounds than the top & bottom of the driver, so the drivers are more prone to disortion...

(I think...), I know it isn't that well explained, but somehow I found this to be more difficult in English than in Dutch (my native language...)

Keep them spinning,
Bert.

Made perfect sense to me. And I agree with you and Kex. Oval would not be my first choice, but could be helpful in tight spaces. It would help to know where and how they may be used.

[Auricauricle]

....As long as space is being considered, I remember attending a CES outside Tokyo. I forget the name of the maufacturer--M&K comes to mind as I write this--but someone was representing a massive subwoofer. As I recall its radius was about 1.5 to 2.0 feet: enormous! They demonstrated it by playing some of that big-drum stuff that Japan is famous for. If you saw the movie, Rising Sun, the credits at the beginning of the flick give you an idea.

I thought it might be a good speaker for the Volkswagon, but something changed my mind...

[ColdPlays]

Thx for all your inputs.

So more info asked.. allright:
Im building an anti-sound module - Im going to stop noise with noise (as in V8 engine noise (until 250 Hz, rest is dampened with passive isolation). I allready managed to produce a working module with round speakers. But indeed, as mentioned, the next module has far less space (height) available. So oval shaped speakers would be great to use, but only when their output is pure.
The round speakers cone material was PP ( 6" )
btw. Bert, I know what ya mean » Me is Dutch too.

ColdPlays

[kexodusc]

:
Im building an anti-sound module - Im going to stop noise with noise (as in V8 engine noise (until 250 Hz, rest is dampened with passive isolation). I allready managed to produce a working module with round speakers. But indeed, as mentioned, the next module has far less space (height) available. So oval shaped speakers would be great to use, but only when their output is pure.
The round speakers cone material was PP ( 6" )


Sounds awesome, but I have no idea what an anti-sound module is (I could guess) or what its use/purpose might be? Could you give us some more details? Are you using speakers to generate frequencies in hopes of creating cancellation of sound waves?

[ColdPlays]

Sounds awesome, but I have no idea what an anti-sound module is (I could guess) or what its use/purpose might be? Could you give us some more details? Are you using speakers to generate frequencies in hopes of creating cancellation of sound waves?

Thats precisely right. Im using speakers to generate soundwaves that are the exact opposite of the offered sound. So the sum of the two is zero (theoretical) » they cancel eachother out.
This system is going to be build in the engine room ventilation ducts on a cruise ship.
Does anybody know the best cone material I can use for low frequency that can stand harsh conditions?

[kexodusc]

Thats precisely right. Im using speakers to generate soundwaves that are the exact opposite of the offered sound. So the sum of the two is zero (theoretical) » they cancel eachother out.
This system is going to be build in the engine room ventilation ducts on a cruise ship.
Does anybody know the best cone material I can use for low frequency that can stand harsh conditions?
Cone material? Polypropylene, aluminum, don't think it matters? They're usually anodized or finished with a polymerized coating of sorts.

I've used a poly-coated paper cone material in the 12" woofer the thinly insulated trunk of my car. I live in Canada. In winter we average -20°C for a few months, it drops below -40°C here in January for awhile...then it gets fairly warm 30°C and very humid in the summer months. It's withstood the climate without issue. Just protect the cone with a good, grill of sorts so nothing pokes a hole in it and you'll be fine.

Unless theres some extreme conditions that would be inhospitable to human habitation....In the vent ducts, how much moisture/heat are we talking here?

[basite]

Does anybody know the best cone material I can use for low frequency that can stand harsh conditions?


polypropylene, or paper threated with polypropylene (not regular paper cones, they'll become moistured and break.) aluminium would work too, but I think polypropylene coned drivers would be the most cost effective & would work well...

btw, from were are you? I'm from Mortsel (near antwerp) in Belgium :)

Keep them spinning,
Bert.

[GMichael]

Sounds like a very cool project. (Pun intended)
So you're going to need to reach some pretty serious volumes I guess. What size speakers do you have in mind? How much room do you have? How many decibels are we talking here? I'm thinking that you may not need to get below 20 htz due to the human hearing limits. You'd still be able to feel numbers below that though. A transducer may be an option for the 0-20 htz area, depending on what kind of room you have to work with.

[ColdPlays]

btw, from were are you? I'm from Mortsel (near antwerp) in Belgium :)

From Roosendaal (Wouw) :cornut:

Conditions are +20 to +50 degrees
And, as Bert mentioned, I cant exclude the moist factor (it would be salty since a cruise ship usualy sails on salt water)
I allready used round polypropylene speakers, so I guess I'll stick to the material when testing oval speakers.
Thank you for all the usefull info.

regards,

ColdPlays

[ColdPlays]

Mike - Im reducing between 10 and 12 dB with the module that has round speakers :)
Its pretty crazy. When I turn on the system, I see the speakers move but the volume is being reduced :P
Im not worried about the sounds below 20 Hz since the most dB's come from 100 to 200 Hz.

[GMichael]

You shouldn't need anything too big to hit the 100 - 200 mark. 4-5" rounds can hit that. Maybe even smaller. But at what levels?

[ColdPlays]

max 70 dB

[kexodusc]

Mike - Im reducing between 10 and 12 dB with the module that has round speakers :)
Its crazy. When I turn on the system, I see the speakers move but the volume is being reduced :P
Im not worried about the sounds below 20 Hz since the most dB's come from 100 to 200 Hz.
What's the primary range of frequencies you're cancelling out? I think you'd be better off exploring using multiple speaker (even smaller drivers 5", 5-1/4", etc) than trying to find and use oval speakers. You can find waaay more options in round drivers, better built, better quality. Are you installing the drivers in speaker cabinets or just using them in free air? Speaker cabinets would allow for some interesting tuning options that would extend the range of frequencies of course.

[GMichael]

I gotta say, I love this whole idea. Noise canceling techniques could be used in many places. Cruise ships, jets, train & subway stations, etc. Ever been inside a powerhouse? You can hardly hear yourself think. My dad can't hear anything over 4k htz due to working at one for 35 years.
70 db wouldn't cut it though. They'd need something a little more powerful.

CP, How much room do you have to work with?

[ColdPlays]

The ultimate peak in the sound that has to be reduced is at 130 Hz. Im allready using 6 speakers which are individualy being calculated (live). Im going to use 12 channels in the next module. Each speaker has its own channel ( so the vetilation duct is devided in 6 (or 12) channels.)
_______
|__|__|__|
|__|__|__|
|__|__|__|
|__|__|__|
approx 808 x 1018 x 250 mm (the height is the killer, I also need to install mics in order to calc the anti-sound)

Like this

[basite]

a good 6,5" driver would easily do that, 70 db is not loud, pretty much any driver will do that with less than a watt of power...

what will drive the speakers? I imagine that on a cruise ship, the 'running times' for the speakers would be pretty long, so i'd look for a pro amp of somekind, basically it's just producing the same tone for a very long while, so it can be a cheaper one too :D
since there will be moisture & salt too, especially, look out for oxidation on the basket too, and the wires and such...

Good luck, sounds like an interesting project :)

Keep them spinning,
Bert.

[kexodusc]

max 70 dB

Yeah, shrink down to a 5-1/4" (commonly available at good prices), or smaller as necessary.
That'll be plenty.

What about a helmholtz resonator for the 130 Hz?

[kexodusc]

The ultimate peak in the sound that has to be reduced is at 130 Hz. Im allready using 6 speakers which are individualy being calculated (live). Im going to use 12 channels in the next module. Each speaker has its own channel ( so the vetilation duct is devided in 6 (or 12) channels.)
_______
|__|__|__|
|__|__|__|
|__|__|__|
|__|__|__|
approx 808 x 1018 x 250 mm (the height is the killer, I also need to install mics in order to calc the anti-sound)

Like this

So you have 808 x 1018 x 250mm for each speaker/channel? Or for all channels?

[ColdPlays]

dimensions are for all channels together.
http://img529.imageshack.us/my.php?image=body5inchspeakerax5.jpg
I just drawn oval shaped +/- 5" holes in the body for the speakers - got to say, looks promising.
Ok so the rooms which have the raster on the side will be filled up with isolation. If you look closely you can see the mic holes.
This is what it looks like with +/- 5" round holes.
http://img209.imageshack.us/my.php?image=body5inchspeakerroundgg7.jpg
I think its worth while to test the oval shaped speakers.

[ColdPlays]

a good 6,5" driver would easily do that, 70 db is not loud, pretty much any driver will do that with less than a watt of power...

what will drive the speakers? I imagine that on a cruise ship, the 'running times' for the speakers would be pretty long, so i'd look for a pro amp of somekind, basically it's just producing the same tone for a very long while, so it can be a cheaper one too :D
since there will be moisture & salt too, especially, look out for oxidation on the basket too, and the wires and such...

Good luck, sounds like an interesting project :)

Keep them spinning,
Bert.

All wires will be sealed. The noise of the engines change when they vary thrust. We agreed to focus on stationairy and cruise mode. I named the thing a module, because I want to have the ability to replace it in a very short time should it start to malfunction. That way I have all the time repairing the malfunctioning module while the new one allready doing its job. This is also handy when it comes to upgrades. Well - I thing you get the point ;)

Greets ColdPlays

[kexodusc]

You can test oval speakers, in fact for your purposes there's nothing wrong with oval speakers. The only negative I can think of is possibly quality/cost. More durable, quality oval speakers are just not made in the same quantity as round drivers so they're likely to cost a bit more, but I don't know the pricing in your area so who knows? But there's probably still a lot of options so go with whatever works.

[E-Stat]

If you use a Round shaped speaker, you get a perfect sinus when you measure the outcome of a wave.

- What happens when you use an oval shaped speaker? Is the 'shockwave' still a perfect sinus? I need to know because I'm experimenting with sound behaviour. A right awnser would help me alot.
I use high resolution full range electrostats which employ a large rectangular diaphragm. The shape of drivers is likely responsible more for dispersion. Back in the 70s, British speaker maker KEF made oval woofers that were found on their products and that of others like IMF.

KEF oval woofer (http://cls.audiogon.com/cgi-bin/cls.pl?spkrfull&1219632003)

Most oval drivers these days, however, are cheap car speakers. The Army commissioned sound reinforcement speaker maker Danley Labs to make a huge subwoofer for similar purposes (although they declined to explain exactly what they were going to do with them.) :).

Matterhorn (http://audiojunkies.com/blog/766/the-worlds-largest-subwoofer-wants-to-kill-you)

rw

[hermanv]

A six inch diameter speaker will be smaller than the wavelength (actually a quarter wave I think) below 500 Hz or so. Below that frequency the speaker will output mostly pure sine waves. Like all speakers they will have 2nd or 3rd harmonic distortion which is usually down more than 30 dB at reasonable volume for either round or oval.

The speaker specifications should have the Thielle/Small parameters, they will include X-max (maximum cone displacement) and Fs (speaker self resonance). Speakers have very little useful output lower than the Fs frequency. Note that a cabinet or baffle can influence the Fs spec.

Since you are essentially modeling a woofer many free woofer enclosure design programs are on the net. They will usually model X-max vs input power or output SPL.

The volumes of the individual speaker chambers look a little small to me for efficient 70Hz performance.

[ColdPlays]

A six inch diameter speaker will be smaller than the wavelength (actually a quarter wave I think) below 500 Hz or so. Below that frequency the speaker will output mostly pure sine waves. Like all speakers they will have 2nd or 3rd harmonic distortion which is usually down more than 30 dB at reasonable volume for either round or oval.

The speaker specifications should have the Thielle/Small parameters, they will include X-max (maximum cone displacement) and Fs (speaker self resonance). Speakers have very little useful output lower than the Fs frequency. Note that a cabinet or baffle can influence the Fs spec.

Since you are essentially modeling a woofer many free woofer enclosure design programs are on the net. They will usually model X-max vs input power or output SPL.

The volumes of the individual speaker chambers look a little small to me for efficient 70Hz performance.

Tnx for the info!
I know space is tight, but actually the focus is between 130Hz and 200Hz (a huge peak of a factor 5 compared to the rest of the bandwith)
I dont exactly understand all factors of the woofer design programs though.

The only thing I'm intrested in now is:
Where, for Pete's sake, can I find 5x7" speakers with no tweeters???
I googled my ass of with only 1 set as result: A speaker with seperate tweeter for 200 euro's. I need 12...
Does anybody has an idea?
tnx

CP

[hermanv]

All these 5 X 7 speakers have tweeters, but they are cheap ($20 to $79) disconnect and/or throw away the tweeter.

http://www.partsexpress.com/webpage.cfm?webpage_id=3&CAT_ID=35&ObjectGroup_ID=43

[GMichael]

Another good source for the Legacy's. http://www.audio-warehouse.com/web/mdl/LS572S/detail.asp

These are cheap speakers but work very well. I've used their brand for several projects over the years. Fairly well made for the price.

[ColdPlays]

2 bad that there arent any standard 5x7 speakers without the tweeter (except the ones with separate tweeters: http://www.amazon.com/Infinity-Reference-6820cs-component-speaker/dp/B000MQAX7C/ref=pd_rhf_p_t_2)

I guess we go for the ones with tweeters and remove them as Herman mentioned.
Thanks for the options you guys offered.

Is there any way we could be in contact in the future in some kind of private channel? (e-mail or closed forum)
Since I dont want to expose any more details of this project to the public...
(GMichael
Hermanv
Kexodusc)
Thanks again for some awesome input!
AR rocks

CP

[Rich-n-Texas]

Is there any way we could be in contact in the future in some kind of private channel? (e-mail or closed forum)
Since I dont want to expose any more details of this project to the public...
(GMichael
Hermanv
Kexodusc)
Thanks again for some awesome input!
AR rocks

CP
Tossed aside, once again, like so much debris...

CP, you can Private Message members from within your individual "User CP".

[GMichael]

Tossed aside, once again, like so much debris...

CP, you can Private Message members from within your individual "User CP".

Awesome input Rich-n-Texas.

You rock!

[Rich-n-Texas]

What're you setting me up for GM? :sosp:

[GMichael]

Just trying to be nice. It seemed like you felt left out.

[Rich-n-Texas]

Just trying to be nice. It seemed like you felt left out.
You know me... "Paranoia the destroyaaaaaa"

I just checked Orange County Speaker Repair, which is where I bought my banana plugs, but I didn't find any oval speakers. Here's their link anyway: http://www.speakerrepair.com/

[hermanv]

Tossed aside, once again, like so much debris...
Sometimes you're the windshield, sometimes you're the bug - Dire Straits.

[ColdPlays]

Tossed aside, once again, like so much debris...

CP, you can Private Message members from within your individual "User CP".
Because that was your 1st message here? :D
But is it a last call attempt or something? Cause Im not trying to be a bad guy here :)
oh and basite, I'll keep you posted too.

Just bought some oval speakers today. Removed the tweeters. Im testing next days

[ColdPlays]

The oval speakers produce to much distortion.
http://img185.imageshack.us/img185/748/5x7jf5.jpg (http://imageshack.us)
:yikes:
http://img165.imageshack.us/img165/1060/6roundqb3.jpg (http://imageshack.us)
This was measured at +/- 8 inch distance from the speakers with a 50Hz tone input.

So I decided to go for 6" round speakers. :wink5:

CP

(end thread?)

[GMichael]

The oval speakers produce to much distortion.
http://img185.imageshack.us/img185/748/5x7jf5.jpg (http://imageshack.us)
:yikes:
http://img165.imageshack.us/img165/1060/6roundqb3.jpg (http://imageshack.us)
This was measured at +/- 8 inch distance from the speakers with a 50Hz tone input.

So I decided to go for 6" round speakers. :wink5:

CP

(end thread?)

That sounds about right. Oval is bound to have some distortion. Just part of it's nature. The 6" round should get plenty low enough for you anyhow.

Close thread? Up to you. You never know if someone might come along with a good idea though. May be worth letting it be.

[Woochifer]

I have a rectangular driver. Does that count?

Just found this blast from the past the other day -- it's a write-up on Adire Audio's Parthenon subwoofer. A 24" square diaphragm that can sustain 11 Hz at 134 db! :eek:

http://www.audiojunkies.com/blog/1201/adire-audio-parthenon-revisiting-the-ultimate-subwoofer

http://media.audiojunkies.com/adire-audio-parthenon-subwoofer-side-view.jpg

And remember the Sony APM speaker lineup from the 1980s?

http://homepage2.nifty.com/k-ooki/apm/apm-6-7.jpg

[GMichael]

Now that's just freaky.

[L.J.]

Just found this blast from the past the other day -- it's a write-up on Adire Audio's Parthenon subwoofer. A 24" square diaphragm that can sustain 11 Hz at 134 db! :eek:



http://www.mysmiley.net/imgs/smile/scared/scared0016.gif

[ColdPlays]

That sounds about right. Oval is bound to have some distortion. Just part of it's nature. The 6" round should get plenty low enough for you anyhow.

Close thread? Up to you. You never know if someone might come along with a good idea though. May be worth letting it be.

true true