My RWTW1k for spacious sound

[MR_Pete]

This is my reflective-way, two-way loudspeaker system with a 1 kHz crossover frequency. It consists of a closed-box for a 12 inch woofer, and a mid to high frequency range 3 inch paper cone driver and cylindrical reflector mounted on top of the enclosure for the woofer. The dimensions of the box for the woofer are approximately those of a cube 24 inches on edge.

The first photo of the attached photos shows how the pair of speaker systems are positioned in a listening room as seen by the listener, except of course laterally positioned a minimum of six feet apart.

The positioning of the 3 inch driver and reflector is such that none of the sound of the the 3 inch driver is reflected off of the near side wall of a listening room. Also a part of that sound is reflected off of the cylindrical reflector towards the listener while another part of that sound reflects off of the far side wall of the room to the listener. This arrangement of 3 inch driver and cylindrical reflector increases the time delay between the listener hearing the direct sound of each speaker (actually sound reflected off of the cylindrical reflector) and hearing the first reflection of that sound off of a side wall. Also the direct sound and the first side wall reflection of a given sound impulse are heard at opposite ears. This results in an increased sense of spaciousness of the reproduction and some would say reduces coloration and image shift. See the paper by Earl Geddes titled "The Geddes Loudspeaker Design Philosophy".

www.gedlee.com/Papers/Philosophy.pdf

The mid and high frequency paper cone driver is TangBand Speakers W3-926SD. The12 inch dual voice coil woofer is Multicomp Pro 55-1465. The cylindrical reflector is a casting of plaster of Paris, 15 inches high by 11 inches wide and 4.5 inches deep at the ends.

The last two photos show the grill that I added to the speakers this past summer. The frame of the grill is 1/4 inch plywood. The back side of the frame has a 1/8 inch deep by 1/2 inch wide recess along the edges of the frame. The grill cloth is stretched over the frame and hot-glued to the back surface of the frame in the recess. The grill attaches to the enclosure for the woofer with pressfit grill guides (Parts Express # 260-366). The holes for the pins and sockets must be of the specified diameter, not larger, otherwise inserting them into the holes in the frame and box isn't secure. It's almost impossible to insert them into the hole of specified diameter, I found, without first coating the pin and socket surfaces going into the holes with linseed oil.

A previous design of a loudspeaker system including a reflective surface is the JBL Paragon. The reflective surface of the Paragon serves a different purpose than what I've devised. First sold by JBL in 1957, the Paragon was continuously produced by JBL longer than any of its other speakers up until 1983.

 

[Curvature]

Do you have any measurements of the results?

 

[DanielT]

@MR_Pete How do you think it sounds?

You have every opportunity, if you want and feel like it, to experiment with the placement and damping of your 3 inch driver.
Try and find what you like.

Carlsson had similar models with different levels of damping on his speaker models. Some examples:

His apprentice John Larsen (R.I.P) then continued on the same path:


Which in a way addresses the problems, the challenges that Earl Geddes that you refer to raises. Although in a different way.

Then the problematic bass FR which should also be mentioned in the editorial speaker placement and reflexes.

Monitor Placement - Genelec.com

To create the ideal listening experience, several aspects need to be taken into account when placing the monitors within the listening space. First, you need to identify the listening area within the space and consider where the listener will be placed in relation to the space as well as the...

www.genelec.com

Which is true but for bass it must be worked together with, weighed in together with specific bass room modes.

 

[MR_Pete]

Do you have any measurements of the results?

So far I haven't gotten around to taking any measurements. Apparently that is now fairly easy to do with the computer based methods, but I haven't been able to find the time to learn how to do it that way. On other speakers, I have used Linkwitz's tone burst technique to measure mid to high frequency measurements and nearfield to measure bass response..

 

[kemmler3D]

Very interesting design! I am always curious about alternatives to direct radiators or horns, but haven't had a lot of opportunity to listen to them, other than my dad's Bose 901s.

So far I haven't gotten around to taking any measurements. Apparently that is now fairly easy to do with the computer based methods, but I haven't been able to find the time to learn how to do it that way. On other speakers, I have used Linkwitz's tone burst technique to measure mid to high frequency measurements and nearfield to measure bass response..

As far as that goes this site has some nice guides on doing measurements with REW, it's not very complicated once you get set up.

 

[DVDdoug]

So far I haven't gotten around to taking any measurements. Apparently that is now fairly easy to do with the computer based methods,

REW (FREE) and a calibrated measurement mic (about $100 USD).

Of course room acoustics and reflections will affect how it sounds & measures (and room dimensions in the bass range) so the measurements are only valid in your room.

 

[MR_Pete]

@MR_Pete How do you think it sounds?

You have every opportunity, if you want and feel like it, to experiment with the placement and damping of your 3 inch driver.
Try and find what you like.

Carlsson had similar models with different levels of damping on his speaker models. Some examples:
View attachment 487050View attachment 487051
His apprentice John Larsen (R.I.P) then continued on the same path:
View attachment 487052

Which in a way addresses the problems, the challenges that Earl Geddes that you refer to raises. Although in a different way.

Then the problematic bass FR which should also be mentioned in the editorial speaker placement and reflexes.
View attachment 487054View attachment 487055

Monitor Placement - Genelec.com

To create the ideal listening experience, several aspects need to be taken into account when placing the monitors within the listening space. First, you need to identify the listening area within the space and consider where the listener will be placed in relation to the space as well as the...

www.genelec.com

Which is true but for bass it must be worked together with, weighed in together with specific bass room modes.

While it would be difficult for me to have an unbiased opinion, I think that the reproduction of my speakers achieves what I set out to do. In the past I've built several two-way systems with a crossover frequency of 2 kHz. This is my first two-way with a crossover frequency of 1 kHz and I think that I prefer the lower crossover frequency. Also the lower crossover frequency allows for a wider frequency band of increased delay of the listener hearing the first side wall reflection and from the opposite side of the room.

A lot of research on my part went into determining the correct placement of the mid to high frequency driver relative to the cylindrical reflector so that the cylindrical reflector would focus some sound into the listening area and other sound radiaties away from the cylindrical reflector to reflect off of the far side wall to the listener. At frequencies >1 kHz this is geometric propagation, so I'm confident that what I calculated to be correct is actually occurring.

In the past I have encountered Carlsson but at the moment I'm not recalling what he was attempting to do.

Thanks,
Pete

 

[a4eaudio]

....and a calibrated measurement mic (about $100 USD)...

Or even Dayton Audio IMM-6 ($23) or IMM-6C ($45).
My IMM-6 with the factory calibration file is quite accurate as compared to my Earthworks.

 

[MR_Pete]

@MR_Pete How do you think it sounds?

You have every opportunity, if you want and feel like it, to experiment with the placement and damping of your 3 inch driver.
Try and find what you like.

Carlsson had similar models with different levels of damping on his speaker models. Some examples:
View attachment 487050View attachment 487051
His apprentice John Larsen (R.I.P) then continued on the same path:
View attachment 487052

Which in a way addresses the problems, the challenges that Earl Geddes that you refer to raises. Although in a different way.

Then the problematic bass FR which should also be mentioned in the editorial speaker placement and reflexes.
View attachment 487054View attachment 487055

Monitor Placement - Genelec.com

To create the ideal listening experience, several aspects need to be taken into account when placing the monitors within the listening space. First, you need to identify the listening area within the space and consider where the listener will be placed in relation to the space as well as the...

www.genelec.com

Which is true but for bass it must be worked together with, weighed in together with specific bass room modes.

Are the loudspeaker systems that you posted photos of your own creations?

 

[DanielT]

While it would be difficult for me to have an unbiased opinion, I think that the reproduction of my speakers achieves what I set out to do. In the past I've built several two-way systems with a crossover frequency of 2 kHz. This is my first two-way with a crossover frequency of 1 kHz and I think that I prefer the lower crossover frequency. Also the lower crossover frequency allows for a wider frequency band of increased delay of the listener hearing the first side wall reflection and from the opposite side of the room.

A lot of research on my part went into determining the correct placement of the mid to high frequency driver relative to the cylindrical reflector so that the cylindrical reflector would focus some sound into the listening area and other sound radiaties away from the cylindrical reflector to reflect off of the far side wall to the listener. At frequencies >1 kHz this is geometric propagation, so I'm confident that what I calculated to be correct is actually occurring.

In the past I have encountered Carlsson but at the moment I'm not recalling what he was attempting to do.

Thanks,
Pete

Undeniably a slightly odd but exciting design you are working on.

In the past I have encountered Carlsson but at the moment I'm not recalling what he was attempting to do.
Stig Carlsson's idea or speaker design concept he called Orthoacoustics. The idea was to create speakers that integrated well into "normal" living rooms/listening rooms. Speakers were designed with consideration for reflections that occur in such rooms. His models were fairly omni in the 1970s, which perhaps suited the sound ideal of the time. It departed from the omni principle in later designs.
I will leave aside how to make speakers that are well adapted for "normal" listening rooms when this "normal" can look different in design, shape, size, furniture and so on. But that was the principle anyway.
You can read a little about it here:

Stig Carlsson and the listening room – Tech Reviews

www.lbtechreviews.com

Are the loudspeaker systems that you posted photos of your own creations?

There were Carlsson models and a Larsen. I missed writing that.

Carlsson OA-52.3 - CarlssonPlanet

Photo: Provided by Anders Eriksson, LTS As all Carlsson fans know, the OA-52 is the top model in the 50-series. It is an upgraded version OA-52.2 and was Stig Carlssons favourite model in the long row of models. It was the speaker he worked with for half a decade in order to improve and refine […]

carlssonplanet.com

Carlsson OA-50.2 - CarlssonPlanet

“The perfect two-way!” – was what the Swedish magazine Hifi & Musik wrote 1996 in an overwhelmingly review of Stig Carlssons new version of OA-50, the OA-50.2. It really is an experience to hear either one of the last completed designs from Stig Carlssons hand. Reviews from the time they were...

carlssonplanet.com

and

SoundStageAustralia.com - Larsen 9 Loudspeakers

www.soundstageaustralia.com

 

[MR_Pete]

Very interesting design! I am always curious about alternatives to direct radiators or horns, but haven't had a lot of opportunity to listen to them, other than my dad's Bose 901s.


As far as that goes this site has some nice guides on doing measurements with REW, it's not very complicated once you get set up.

Some of the sound of the 3 inch driver of my system does radiate directly towards what would be the front of a listening room, but this is only a small percentage of its total sound. This is nothing like 9 drivers obliquely radiating towards the front of a listening room and only one driver radiating into the listening area.