there are for sure old receipes that works !
300 hz circa cut-off is one of the known ones, see V. dickason book.
As the lower XO with firering towards a close front wall... many illustrations not always understood by the magazines reviewers Eg Boston Lynnfield 500 : pass band bass with first electric slope giving a circa 100 hz acoustic third slope firering with rear ports towards the close wall according the owner manual... Quite solid and tight bass... delayed without one can hear it.
front panel tweet-mid at 20" from the rear panel
300 hz circa cut-off is one of the known ones, see V. dickason book.
As the lower XO with firering towards a close front wall... many illustrations not always understood by the magazines reviewers Eg Boston Lynnfield 500 : pass band bass with first electric slope giving a circa 100 hz acoustic third slope firering with rear ports towards the close wall according the owner manual... Quite solid and tight bass... delayed without one can hear it.
front panel tweet-mid at 20" from the rear panel
From post #42
A single low frequency monopole source is bad. A single cardioid source is less bad. You can't get good until you use multiple low frequency sources.
Once you have multiple low frequency sources:
That's where destructive interference low frequency cardioid fails. So if you're using the D&D 8C as inspiration for a DIY design *adding* cardioid low frequency doesn't help you -- unless you have the special case where you don't want to use multiple low frequency sources, at which point you're deciding between the available bad options.
Salas and Geddes identified 200-500Hz as the sweet spot for cardioid.
Kantamaa's master thesis backed them up with double blind listener experiments. Kantamaa's cardioid played down to 80Hz. The D&D 8C plays down to 100Hz. You could design for either of those and safely cover 200-500Hz.
Optionally, it's easy to cover that limited frequency range with active destruction which allows you to place your low-mid driver in a sealed enclosure so you don't struggle with distortion at higher listening volume.
A single low frequency monopole source is bad. A single cardioid source is less bad. You can't get good until you use multiple low frequency sources.
Once you have multiple low frequency sources:
That's where destructive interference low frequency cardioid fails. So if you're using the D&D 8C as inspiration for a DIY design *adding* cardioid low frequency doesn't help you -- unless you have the special case where you don't want to use multiple low frequency sources, at which point you're deciding between the available bad options.
Salas and Geddes identified 200-500Hz as the sweet spot for cardioid.
Kantamaa's master thesis backed them up with double blind listener experiments. Kantamaa's cardioid played down to 80Hz. The D&D 8C plays down to 100Hz. You could design for either of those and safely cover 200-500Hz.
Optionally, it's easy to cover that limited frequency range with active destruction which allows you to place your low-mid driver in a sealed enclosure so you don't struggle with distortion at higher listening volume.
^I can also repeat forever if you continue quoting cardioid bass thread.
In practice stereo cardioid has been valuable down to lowest mode also in small rectangular rigid rooms, though advantages are greatest where front side of the room is the most dominant i.e. walls are non-diffusive, rigid, reflective and close to speakers, and rear side is not all that.
Also consumers probably prefer stereo application ready at once over multi-mono system which probably requires some measurements and tuning of locations and EQ. No need to select the most complex way if stereo cardioid works fine.
Kantamaa uses two small (Genelec) 2-way speakers with delay which cannot produce cardioid lower than 80 Hz. So that study does not try to provide answer how low cardioid could be valuable.
In practice stereo cardioid has been valuable down to lowest mode also in small rectangular rigid rooms, though advantages are greatest where front side of the room is the most dominant i.e. walls are non-diffusive, rigid, reflective and close to speakers, and rear side is not all that.
Also consumers probably prefer stereo application ready at once over multi-mono system which probably requires some measurements and tuning of locations and EQ. No need to select the most complex way if stereo cardioid works fine.
Kantamaa uses two small (Genelec) 2-way speakers with delay which cannot produce cardioid lower than 80 Hz. So that study does not try to provide answer how low cardioid could be valuable.
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This isn't correct.
You can get decent bass from a single monopole bass source with the correct time delay relative to the rest of the loudspeaker system.
IF you couldn't then there would be little point in the entire subwoofer industry: people just wouldn't be interested. (..and a lot of soundbars with subs can sound pretty good.)
As for good: that's the above condition, proximity to the source relative to room modes in front of the source relative to the listener, and other factors largely dealing with electro-mechanical results of the design.
Ex. you can get very good bass (depending on the listener's position relative to room walls) with a single monopole subwoofer right behind the listener.
Then there is excellent, and you won't get truly excellent without a dipole bass system that's positioned optimally relative to the listener. This is a near-field stereo design that simulates a marginal amount of head-shading at lower freq.s via the dipole's null's.
A big advantage of his thesis is it's recent; he collected recent and relevant research up to 2020. I didn't see any citations showing two channel cardioid bass is better than multi-channel monopole. If such research existed it would be a significant omission in his masters thesis. The closest I saw was single monopole compared to single cardioid and multi-cardioid Ferekidis, Lampos; Kempe, Uwe (2005, May 1) Controlling the Mode Excitation of Rooms by using Multiple Low Frequency Cardioids in Multichannel Systems.
Since 2005, no research demonstrating two channel cardioid is better than multi-sub.
We also know directivity supplies no advantage below the room transition range.
So, why continue to repeat all of this? Because it maintains background for discussions that involve speculation about cardioid bass. It also challenges people who think cardioid bass is good to clearly define use cases or find research that adds support.
I've seen people say nearfield dipole is good for apartment listening where you don't want to bother the neighbors. Why is dipole bass better than two small monopoles in that situation? (e.g. a system that can be dipole or cardioid or monopole)
A lot of overthinking about theoretical horse droppings imnsho....
Rooms don't begin to fit models, either geometrically or versus assumed absorption by frequency. Which makes Schroeder a jump ball. And RT60's vary all over the spectrum..
Basic room modes, and additional modes/excitations/cancelations from sub placements (especially multiple placements ) only compound the mess.
Single subs, stereo subs, multiple subs, cardioid subs..... there is NOT a best choice for any or all rooms. Especially small rooms.
One size/type shoe does not fit all.....
Rooms don't begin to fit models, either geometrically or versus assumed absorption by frequency. Which makes Schroeder a jump ball. And RT60's vary all over the spectrum..
Basic room modes, and additional modes/excitations/cancelations from sub placements (especially multiple placements ) only compound the mess.
Single subs, stereo subs, multiple subs, cardioid subs..... there is NOT a best choice for any or all rooms. Especially small rooms.
One size/type shoe does not fit all.....
+1 ... maybe even +2
I use two monopole sealed box subs. I am very interested in alternative bass technologies, cardioid and dipole, ... even though I am extremely satisfied with the bass system I have.
What I would like to see is a little less dogma and a little more respectful debate.
That is a rather strong statement, you think ?
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More experiences with practical implementations in different rooms. Less just empty debate = referring simplified theories and statistical features with zero experience how system really works and sounds in practice.
You can adjust dipole nearfield to where the null for "L" is pointed at the listener's right ear, and vice-versa. It's not a complete effect like headphone listening (..which isn't correct unless it's binaural), but there is enough resulting pressure loss to actually provide the sense of channel separation at low freq.s.
Because of such a close proximity to the listener it has very little to do with room interaction (or lack thereof).
A stupid question surely and I apologize for that...
Does a plan bass emiter is pressurizing the room the same way than a big cone sub driver...the 18" ?
I am not sure to understand how the bass treatment say below circa 80 hz differs for the listener since the power response and group delay have been setuped for the room.
Maybe presurization ca not be thinked anymore in term of power response and wavelength below the Shroeder frequency response of the room ?
Does a plan bass emiter is pressurizing the room the same way than a big cone sub driver...the 18" ?
I am not sure to understand how the bass treatment say below circa 80 hz differs for the listener since the power response and group delay have been setuped for the room.
Maybe presurization ca not be thinked anymore in term of power response and wavelength below the Shroeder frequency response of the room ?
Here's an image containing frequency response from the Ferekidis, Kempe paper. Single monopole, single cardioid, multi-cardioid.
In contrast, companies make DIY products (measure yourself and let the computer do the work) using multi-subs that create a flat response.
I'm not saying bad bass is unacceptable. Humans lived with bad bass in small rooms for decades and no one died from it. But if you're building a D&D 8C then you want to know these things so you can make design choices. Do you try to extend the passive cardioid lower? Do you remove the low frequency drivers from the back and make them independent?
If there are specific use cases for cardioid bass or nearfield then a person might fit into one of those slots. It won't kill them.
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I don't think that's possible because sound waves travel fast and humans process low frequencies slow. But I'd ask if maybe you turn walls that otherwise wouldn't damp low frequencies into low frequency dampers because the energy levels are low. In other words, your low power source effectively creates low frequency room treatment.
Relating to the room:
Well, dipoles excite different modes than monopoles and they DON'T excite the lowest room mode (or more realistically: excite adjoining rooms in a typical "leaky" listening room condition - it's this specific aspect why I use it for my HT).
Still, it's principally because of very close proximity. (..dipole near-field.)
The reason is that it's MUCH louder near the listener relative to the rest of the room: particularly as freq.s LOWER. (..in fact depending on the listener distance (and Qts) you rarely have to boost much (if any) of the lower freq. output of the dipole bass driver despite the fact that pressure loss is rather massive per octave as freq.s lower at/approaching a meter in distance.)
So, even though you've got your dipole subs playing loud near you - elsewhere in the room it's down many decibels (from what the listener is hearing), particularly as freq.s lower.
Well, dipoles excite different modes than monopoles and they DON'T excite the lowest room mode (or more realistically: excite adjoining rooms in a typical "leaky" listening room condition - it's this specific aspect why I use it for my HT).
Still, it's principally because of very close proximity. (..dipole near-field.)
The reason is that it's MUCH louder near the listener relative to the rest of the room: particularly as freq.s LOWER. (..in fact depending on the listener distance (and Qts) you rarely have to boost much (if any) of the lower freq. output of the dipole bass driver despite the fact that pressure loss is rather massive per octave as freq.s lower at/approaching a meter in distance.)
So, even though you've got your dipole subs playing loud near you - elsewhere in the room it's down many decibels (from what the listener is hearing), particularly as freq.s lower.
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A bass planar typically has a much larger surface area (to work properly in the bass region), and much less excursion.
-so because it effects a much larger room area (exciting multiple regions as the bass planar is usually vertically TALL) and each region it effects has less pressure because of the distribution, it is different.
Make a vertical array of 18" dipoles that matches similarly to the bass planar array and the result starts becoming much more similar. (..though you have many other factors other than interaction with the room that expose differences in subjective results.)
thanks Scott for the input, quite a difficult thread to follow. But a cool one for sure.
of course my question was at iso Sd between both planar or cone. (I tried to illustrate it for myself like pressure nods around the listener but distributed differently with each type of bass emitter... power response in a room seems short to describe all the different subjective feeling with bass listening for the basic enthiusiast)
of course my question was at iso Sd between both planar or cone. (I tried to illustrate it for myself like pressure nods around the listener but distributed differently with each type of bass emitter... power response in a room seems short to describe all the different subjective feeling with bass listening for the basic enthiusiast)
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https://www.diyaudio.com/forums/att...ioid-active-speaker-insipired-8c-photo_-_-jpg
^ There is far to much volume here (and particularly the back of the volume isn't near the driver) and the flow resistance isn't "stiff" (more like just stuffing that's ready to "blow out" of the cabinet).
A good resistor often has wire- mesh on both sides (in cabinet and externally on side of cabinet), and is corrugated/pleated: think "return air filter"..
^ There is far to much volume here (and particularly the back of the volume isn't near the driver) and the flow resistance isn't "stiff" (more like just stuffing that's ready to "blow out" of the cabinet).
A good resistor often has wire- mesh on both sides (in cabinet and externally on side of cabinet), and is corrugated/pleated: think "return air filter"..
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I think you may have missed my point. There is no disputing that a monopole bass source in a standard room will have modal responses, and along with that comes various dips and peaks.
If you had said (for instance) "A single low frequency monopole source will excite room modes, with large peaks and dips. A single cardioid source will have somewhat less large peaks and dips. You can't get a more or less flat response until you use multiple low frequency sources."... This would be a factual statement.
But you use the term "bad bass", which is a value judgment, and you throw it around in a condescending way. In order for a bass producing technology to be "bad" it would have to be musically unsatisfying to a significant majority of listeners. This is not the case.
Perhaps, I agree with your initial objection but I think it could be clarified even further. Generally I'm tending to agree with what Kimmo said in #109.
To pick just one point, you can't say that cardioid doesn't radiate front and back so therefore it won't activate a front to back mode. It can be fed that way, and the mode will control the radiation of that energy.. thus taking away the significance, or meaning of the speaker's directivity with regard to it.
To pick just one point, you can't say that cardioid doesn't radiate front and back so therefore it won't activate a front to back mode. It can be fed that way, and the mode will control the radiation of that energy.. thus taking away the significance, or meaning of the speaker's directivity with regard to it.