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Hello All,
This is my first post and I have come about 12 years late to this topic.
A couple of weeks ago I auditioned the Duevel Bella Luna Diamante omnidirectional speaker and was very impressed.
First of all the Duevel sound is effortless. I listened for a solid 2 hours and it was completely non fatiguing and natural sounding. The speakers completely disappear and the soundstage is immense. The soundstage seems to "adjust" to the recording space whether it be a concert hall or an intimate setting.
Since I am a hobbyist woodworker I got to wondering if I could build a set of my own similar in design, and after some internet research found Mr. Neubec's Mentor I and Mentor II projects.
The level of effort and documentation Mr. Neubec has put into his posts on the topic are absolutely amazing and of professional quality. After going through the posts (and there were many) I have a couple of observations and some questions.
1. Was the "Duevel-like" version of the project ever completed? In reading the posts it appeared that when the Duevel like diffusers were used in concert with a waveguide for the tweeter, the frequency response was excellent both and off axis. I am curious why this version of the project was shelved?
2. Mr. Neubec referred to high efficiency woofers and compression drivers for the tweeter. Is there a particular reason why they were not used in the project? His posts suggest that use of such drivers could have simplified the Mentor design since only 2 drivers would be required.
3. Would Mr. Neubec have any thoughts on a TQWT design where the port of the transmission line is in the top of the speaker cabinet? I recently built a prototype speaker using this idea, and found the soundstage dramatically expanded, and to be honest somewhat similar to the Duevels. The main driver faces the listener so the result is a hybrid omni directional approach. I am pondering whether a Duevel like diffuser placed atop the circular port would result in a more balanced omnidirectional sound stage? I got the TQWT design from this calculator:
Observations re the Duevel design.
The down firing tweeter is definitely a compression driver with a horn wave guide which is the same shape as the diffuser, and it fires into the top half of the diffuser. Of possible interest, the crossover between woofer and tweeter is at 1000 Hz, and the acoustic diffusers are about 13 inches in diameter which is the wavelength of a 1000 Hz tone. which begs the question: should the diffuser diameter be the same as the cross over frequency wavelength for best results?
The closest tweeter I could find to the Duevel was made by Rfc in Italy which has a response from 500 Hz to 20 Khz. The up firing woofer has a response from 40 Hz up to around 2500 Hz, resulting in a good overlap between the woofer and tweeter response. When the diffusers for the 2 drivers face each other, the waveforms of the woofer and tweeter intersect resulting in a perceived sound source coming from the intersection of the diffusers. In other words a 360 degree point source.
Based on the company literature the cabinet is internally damped and ported at the bottom 4 corners.The cabinet sits on a plinth which is a couple of inches thick. There does not appear to be a diffuser at the bottom of the cabinet.
Many thanks for any thoughts the community may have on this topic.
Dean Hummel
This is my first post and I have come about 12 years late to this topic.
A couple of weeks ago I auditioned the Duevel Bella Luna Diamante omnidirectional speaker and was very impressed.
First of all the Duevel sound is effortless. I listened for a solid 2 hours and it was completely non fatiguing and natural sounding. The speakers completely disappear and the soundstage is immense. The soundstage seems to "adjust" to the recording space whether it be a concert hall or an intimate setting.
Since I am a hobbyist woodworker I got to wondering if I could build a set of my own similar in design, and after some internet research found Mr. Neubec's Mentor I and Mentor II projects.
The level of effort and documentation Mr. Neubec has put into his posts on the topic are absolutely amazing and of professional quality. After going through the posts (and there were many) I have a couple of observations and some questions.
1. Was the "Duevel-like" version of the project ever completed? In reading the posts it appeared that when the Duevel like diffusers were used in concert with a waveguide for the tweeter, the frequency response was excellent both and off axis. I am curious why this version of the project was shelved?
2. Mr. Neubec referred to high efficiency woofers and compression drivers for the tweeter. Is there a particular reason why they were not used in the project? His posts suggest that use of such drivers could have simplified the Mentor design since only 2 drivers would be required.
3. Would Mr. Neubec have any thoughts on a TQWT design where the port of the transmission line is in the top of the speaker cabinet? I recently built a prototype speaker using this idea, and found the soundstage dramatically expanded, and to be honest somewhat similar to the Duevels. The main driver faces the listener so the result is a hybrid omni directional approach. I am pondering whether a Duevel like diffuser placed atop the circular port would result in a more balanced omnidirectional sound stage? I got the TQWT design from this calculator:
Observations re the Duevel design.
The down firing tweeter is definitely a compression driver with a horn wave guide which is the same shape as the diffuser, and it fires into the top half of the diffuser. Of possible interest, the crossover between woofer and tweeter is at 1000 Hz, and the acoustic diffusers are about 13 inches in diameter which is the wavelength of a 1000 Hz tone. which begs the question: should the diffuser diameter be the same as the cross over frequency wavelength for best results?
The closest tweeter I could find to the Duevel was made by Rfc in Italy which has a response from 500 Hz to 20 Khz. The up firing woofer has a response from 40 Hz up to around 2500 Hz, resulting in a good overlap between the woofer and tweeter response. When the diffusers for the 2 drivers face each other, the waveforms of the woofer and tweeter intersect resulting in a perceived sound source coming from the intersection of the diffusers. In other words a 360 degree point source.
Based on the company literature the cabinet is internally damped and ported at the bottom 4 corners.The cabinet sits on a plinth which is a couple of inches thick. There does not appear to be a diffuser at the bottom of the cabinet.
Many thanks for any thoughts the community may have on this topic.
Dean Hummel