Open baffle speaker pitfalls

[test1223]

It would certainly be interesting to simulate how different speaker concepts excite a sample room if the speaker position in the room is always identical, but that's not the goal of the thread.

Yes. The spinorama data lack of important insides in the bass behavior of a loudspeaker. Even if you have a look at simpler monopole speakers you can't see much with these measurements. For example take the superior behavior of a stand mount speaker with a bass near the floor vs. a book shelf speaker on a stand. The floor bounce phase offset can't anywhere be found in the spinorama data but will be present with almost any bookshelf speaker placement in a real room.

Now with dipol speakers the complexity is take to another level. As you might have noticed the frequencies where the resonances are will slightly change if you add a solid floor and to place the speaker on a floor is very likely. So should the simulation contain a floor? I would say of cause it should.

The question is where does the speaker end and where does the room beginn and with bass frequencies I would argue that the whole room is the speaker.

It is simply not possible to create a simulation or measurement for every listening room in the world.

A big problem yes. But what did you get from using free field conditions to evaluate speaker designs in the bass frequencies? For monopoles I would say you get some inside but you have to have knowledge about room interaction with monopole speakers. For dipols there isn't much research about the room interaction so your claim

If free field measurements or simulations in the bass-midrange show you errors in the radiation and directivity, then the probability that this speaker will cause problems in your listening room (and measure less well) is much higher than a speaker without design flaws.

has to be evaluated in the first place. I would argue that even for monopol designs the design goal of a flat frequency response in the bass doesn't deliver the highest possibility of a good in room response. A lot of listening rooms are more similar for a speaker class (size) and some assumed room gain is beneficial (have a look at the KEFs bass tuning). So I would claim that for dipole designs there might be much more unexpected behavior which is on average better but doesn't look that good if you have a look at the free field response only.

When we use simulations we are pretty powerful. I think you restrict yourself to established types of presenting data here. But in this context you don't get much from the advantage that you can compare these data to other free field data, since it doesn't tell much without taking the room or at least the floor into account anyways.

 

[yourmando]

@ctrl Thanks a bunch for doing these simulations. This is very helpful!

+1 this is dope

 

[Richard G]

Yes. The spinorama data lack of important insides in the bass behavior of a loudspeaker. Even if you have a look at simpler monopole speakers you can't see much with these measurements. For example take the superior behavior of a stand mount speaker with a bass near the floor vs. a book shelf speaker on a stand. The floor bounce phase offset can't anywhere be found in the spinorama data but will be present with almost any bookshelf speaker placement in a real room.

Now with dipol speakers the complexity is take to another level. As you might have noticed the frequencies where the resonances are will slightly change if you add a solid floor and to place the speaker on a floor is very likely. So should the simulation contain a floor? I would say of cause it should.

The question is where does the speaker end and where does the room beginn and with bass frequencies I would argue that the whole room is the speaker.

A big problem yes. But what did you get from using free field conditions to evaluate speaker designs in the bass frequencies? For monopoles I would say you get some inside but you have to have knowledge about room interaction with monopole speakers. For dipols there isn't much research about the room interaction so your claim

has to be evaluated in the first place. I would argue that even for monopol designs the design goal of a flat frequency response in the bass doesn't deliver the highest possibility of a good in room response. A lot of listening rooms are more similar for a speaker class (size) and some assumed room gain is beneficial (have a look at the KEFs bass tuning). So I would claim that for dipole designs there might be much more unexpected behavior which is on average better but doesn't look that good if you have a look at the free field response only.

When we use simulations we are pretty powerful. I think you restrict yourself to established types of presenting data here. But in this context you don't get much from the advantage that you can compare these data to other free field data, since it doesn't tell much without taking the room or at least the floor into account anyways.

There is some good analysis on the effects of the room on dipoles, including placement of the driver relative to the floor and walls, reflections etc at http://www.dipolplus.de/thema5.html

 

[charlielaub]

There is some good analysis on the effects of the room on dipoles, including placement of the driver relative to the floor and walls, reflections etc at http://www.dipolplus.de/thema5.html

Unfortunately, apart from the first analysis of floor gain due to the proximity of the woofer to the floor, most of the rest is wrong. This is because when boundary reflections reach the listener at least 6msec after the direct sound the brain suppresses them for several tens of milliseconds. This is how we are able to make sense of sounds in a reflective environment such as an indoor space. So you cannot sum the source and its reflection and produce a frequency response showing an interference pattern - that is just not how the human hearing process works and is incorrect/misleading.

For a properly designed dipole loudspeaker that has identical front and rear frequency response and in a room with walls that can reflect all frequencies equally, the room reflections that occur sufficiently after the direct sound are actually beneficial and increase the apparent soundstage. IMO this is poorly understood and only applies to dipole systems. It is also why many audiophiles feel the need to resort to "room treatment" for their boxed loduspeakers, which have very position and frequency dependent acoustic radiation (e.g. for angles away from the direct, on-axis sound). For monopole radiators the room reflections are much more detrimental to the sound stage, etc.

 

[Richard G]

You’ve reminded me of Linkwitz’ article on the delay between reflected signal and the direct signal reaching the listener, and room reverberation time https://www.linkwitzlab.com/listening_room.htm and

 

[deanznz]

You’ve reminded me of Linkwitz’ article on the delay between reflected signal and the direct signal reaching the listener, and room reverberation time https://www.linkwitzlab.com/listening_room.htm

Interesting.. thank you. After reading that someone may like this idea that is abbreviated in this post:

I think I get it. You are using moderately narrow directivity L and R speakers crossed in front of the listening position (LP), plus one Distributed Mode Loudspeaker(DML) fed L+R edge-on to the listening position (LP), so the LP and the front wall are in the DML's dipole nulls and side wall reflections are largely from the DML. Clever.

the thread is here:

DML And Waveguided Speaker Combined?

See graphics below: The loudspeakers AC and DC have relatively narrow dispersion of constant directivity 90° by 60° nominal from about 800Hz on. Otherwise I would consider them ‘perfect’ in regards of available extension, spl, HD, IM, no resonances etc. Nice cousins to JBL’s M2 maybe. When...

www.audiosciencereview.com

For anyone who has an exciter or 2 and a panel or 2, I highly recommend people try this out, it sounds wonderful. Even mono music has more life to it. Being able to vary the volume between the Main speakers and the DML is an important option. If anyone thinks their system is pretty nice, but finds they are still chasing..... something then try this.

Dean.