Cardioid Bass.... yes, very good!!

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I am going to experiment with trying to get more of a cardioid response from my woofer too. I've been using the Bonded Logic behind the Neo10s , but want to try several layers behind and around the woofer now too.
Greg
I'm hoping to add enough bonded logic around the lower backside of my baffle to get radiation somewhere less than a dipole and more like a cardioid. At least enough so that I get a smoother transition from full dipole to the omni of the subs that sit right next to them. Baffle to sub crossover is currently 60Hz.

I've been experimenting with cardioid using Bonded Logic.
http://www.diyaudio.com/forums/multi-way/211816-waveguie-cardioid-slim-baffle-9.html#post3180842
Achieving a cardioid response by absorbing the rear wave is difficult at low frequencies. I'd say you need at least 3 layers of Bonded Logic to get usable cardioid above 250Hz.


Yes, that's one way to doit.
Using w-frame, For dipole both the front would be (simplified):

Front | Back
(+) | (-)
(+) | (-)

The cardioid setup:
(+)|(+)
(+)|(-)

Hence it cancels at the back.
The cabinet needs to be acoustically small.

If you seal one of the woofers it should probably be:
(+)|
(+)|(-)

Do I understand correctly?


Yes, in an active set-up, one can play with the phase and delay of the rear woofer to tune the system to more of a cardioid response. Something like Meyer does with their PA subwoofers:

PSW-6 : High-Power Cardioid Subwoofer

Or in a passive U-frame style ala JohnK:

NaO U-frame


There are some great examples and explanations of cardioid bass on this site, including how to use a monopole driver in the back.
Cardioid bass
 
I've been experimenting with cardioid using Bonded Logic.
http://www.diyaudio.com/forums/multi-way/211816-waveguie-cardioid-slim-baffle-9.html#post3180842
Achieving a cardioid response by absorbing the rear wave is difficult at low frequencies. I'd say you need at least 3 layers of Bonded Logic to get usable cardioid above 250Hz.


There are some great examples and explanations of cardioid bass on this site, including how to use a monopole driver in the back.
Cardioid bass

What thickness of BL are you using?

Thanks for that site! Lots of good info there.
 
In theory I like cardioids too. They have the potential of allowing them placed very close to the room front wall.

I wish John K... manages to set up his mono-dipo-cardioid speaker and share some impulse responses.


- Elias

I will, but at the moment it is the unset of fall in New England a and I am preoccupied with thing other than stereo and music. Thus will be a littler different because I will be using digital eq and delays to make things absolutely identical.

If we get a couple of rainy days I may be able to throw the old CRAW together and see if it still works. I don't have the drivers it is supposed to be used but some that are pretty similar.
 
What thickness of BL are you using?

Thanks for that site! Lots of good info there.

I'm using the rolls and they are 2 inch thick.
16 in. x 48 in. UltraTouch Denim Insulation Multi-Purpose Roll-60301-16482 at The Home Depot

I wrap a double layer around the driver basket, and then I use a double sheet on top of it. So it's actually 4 layers but there's some empty space inbetween. My measurements show a cardioid behavior to around 250Hz and it turns dipole below that.

Picture 001.jpg
 
Ah yes, I thought what you were using looked thin compared to mine. I'm using the R13 rated stuff, so it is closer to 3.5" thick and rated for excellent acoustical absorption to below 100Hz. Doubling or tripling up should get me where I wanna be. I've even got some of the R19 at the studio if I need it.
 
Hi All


I have drwan it in sketchup, it looks like that and I go build it to try it, because I am curieus about it and we have to try everything in live.
 

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Do you now this? I did found it just when googling.

http://www.kirchner-elektronik.de/~kirchner/DIPOL-CARDIOIDeng.pdf

Hmm old topic, but not a problem I hope.

I looked at this a long time ago, when it was first published. Here is the result of my investigation: dipole_cardioid_woofer

One problem I had was that they indicated a -18dB null at 90 degrees and at the same time 3dB low SPL at the rear. The thing is that to have an -18db null the difference between front and rear SPL would have to be on the order of only 1dB.

The other issue that I have more recently begun to recognize is that whether it be dipole, cardioid or other, the free field response at low frequency is not relevant in a room. In a room these types of sources all reduce to multiple monopoles with different position and phase. The only real difference between dipole woofers and distributed monopoles in a room is that the dipole sources have a net zero volume displacement and can not excite the DC mode.

You can only reinvent the wheel so many time before someone start to catch on. :)
 
Hi John

The article in pdf the inventers give as idea that the efficientie is a lot better with this kind of box, I do not now afcourse I have never test it, os as I did read it is a problem to get the back and front of the speaker isolated,, so a wave can not traffel there and cancel low frequenties, oke, these guys say why not mass load the conus and give sound velocity a push and the wave need more time to get to the front of the speaker.

Did you build the one on your picture? not the double one I did drawn.

The wheel, wel no need for re-invention, but maybe I can let it better rolling.

I do always re-invent te wheel with the audio amps, old idea,s are populair these days, like single ended, and such.

thanks for your link, I go read it. Maybe a better way for cardioid is the use of a delay line (bessel allpass will do perfectly) and a extra speaker..
 
Maybe a better way for cardioid is the use of a delay line (bessel allpass will do perfectly) and a extra speaker..
Small gradient arrays are done much this way. Varying the delay between both woofers alters the cardioid pattern ... fine at lower frequencies. Pattern will still deteriorate as frequencies rise .. this mostly dictated by element spacing.

* Should include that steering woofer would have its phase inverted as well as delay applied.
 
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* Should include that steering woofer would have its phase inverted as well as delay applied.

Yes you are right 180 degree.

For a sub between 20 and 120 hz the delayline is fine, like a bessel who is fase consisted for a couple of octaves.

But I go not make that, room invloence is to big, open field yes that is fine.

I want try this very soon, I have use 1 x Sd for front and 1/3 for both rear openings.

have a good evening/day.
 

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Thanks very interesting article, I try some thi some time, I make a electronic (bessel alpass with opamps) and a 180 degree fase shifter, this is not difficult, and try with two closed boxes back to back, I only need twice as much bass amps, or only one for mono, but music is also stereo in the low tones I have heard?

I want try first the box I drawn, this is from a german guy but it is not really further developed? it is not for the cardioid wich is difficult in normal room but efficienty of this box is higher says the developer that is interesting.

regards
 
Hi All

I have made the box, I have still need measurements and I let now, for the sound, it give pretty good bass, also low end, and it is louder then the dipole/ripole.

here some pics.
 

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...unless you're in the near field.

For me cardioid is not my search, but more efficienty, and near field, tja, in a home it is not a theatre, only big audient places needs cardioid because it give more efficienty because it is more directed to the front..

If i want cardioid then I put me head in the box, then I have a true cardioid, or I make a horn, the best cardioid ever.

But serieus, this thing here sound very well, I go make a bigger one where the part of the box where the magnets are has a volume who is also needed when I have a closed one, or a basreflex one and front of speakers still mass loaded.

I have need a shelf filter for the dipoles, for this one I have more bass, it is punchy and no need for the shelf filter anymore, or maybe very little correction nut first measurements.
 
If bass is "punchy" or not is usually a midrange property. That darn Fourier stuff again. You of course have selected superb mid-range armament. My experience is bass is a matter of managing the peaks and distortion. Are you expecting some sort of un-equal phase cancellation front to back modifying the radiation pattern? Please enlighten me here.
 
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