[rajacat]

These particular 15" or 18" waveguides wave guides work well with a 15" woofer. Time delay? The depth of the woofer and the waveguide are similar and if it's an issue it can be mitigated with dsp or adjust the cabinet a bit.

Well... I will soon see if it works 'cause I'm just finishing up my bass bins for the TD15Ms'.  The SEOS18/compression drivers waveguides will be mounted on top in removable boxes that will allow a little adjustment for depth spacing. The SEOS18 holds pattern control to ~ 650hz. The 1" comp. driver I'll use goes down to 650hz so it'll be about there where I'll crossover.  Since I'm crossing this low maybe time delay issues won't be so important.
If you go elsewhere there are many testimonials to the sound quality of similar SEOS based speakers. Geddes speakers employ a round WG which have a greater center to center distance than SEOS and he also had to deal with time delay issues too.

[Danny Richie]

These particular 15" or 18" waveguides wave guides work well with a 15" woofer. Time delay? The depth of the woofer and the waveguide are similar and if it's an issue it can be mitigated with dsp or adjust the cabinet a bit.

It actually doesn't work that way. With a big wave guide and a big woofer the center to center spacing can be 16" or more apart. Now you can use common DSP crossovers (which sound horrible) to adjust for time delay on axis and get them in phase. However, as you move a microphone up vertically you'll see that the change in distance between the two drivers will cause them to be out of phase and cause a cancellation that can be a 15db hole. So while the horizontal off axis looks great, the vertical can be a mess.

Well... I will soon see if it works 'cause I'm just finishing up my bass bins for the TD15Ms'.  The SEOS18/compression drivers waveguides will be mounted on top in removable boxes that will allow a little adjustment for depth spacing. The 1" comp. driver I'll use goes down to 650hz so it'll be about there where I'll crossover.

That will be your saving grace (the low crossover point).

Since I'm crossing this low maybe time delay issues won't be so important.

650Hz is about 20.5" long wavelengths. If you can keep the acoustic centers less than that then it won't be too bad.

If you go elsewhere there are many testimonials to the sound quality of similar SEOS based speakers. Geddes speakers employ a round WG which have a greater center to center distance than SEOS and he also had to deal with time delay issues too.

I have heard that those have a significant hole in the vertical off axis, but have not measured a pair myself.

I think you have a good understanding of the principles. Hopefully it will work out well for you.

[jtwrace]

Another problem that is always overlooked by these guys

Are you referring to these guys linked in the above article?

Credit where credit is due:
 
I first heard of time-intensity trading with speakers in an AES paper about
development of the DBX Soundfield One loudspeaker (google for more info).
 
Don Keele, Earl Geddes, Tom Danley, Wayne Parham, Duke Lejeune, and Zilch
have discussed these concepts, as applied to horn/waveguide based
loudspeakers, in various articles and forum posts..

[Danny Richie]

Are you referring to these guys linked in the above article?

Here is my whole sentence.

"Another problem that is always overlooked by these guys is that the biggest reflection point in the room is typically not the side walls. It's the ceiling. And you want just as smooth and even response in vertical off axis response as well as the horizontal off axis response."

Not referring to anyone specifically but with most large wave guide designs the horizontal is emphasized while the vertical off axis is overlooked. 

[rajacat]

Another problem that is always overlooked by these guys is that the biggest reflection point in the room is typically not the side walls. It's the ceiling. And you want just as smooth and even response in vertical off axis response as well as the horizontal off axis response.

Wouldn't it be more optimum to have a tighter control of the vertical response since the the ceiling is typically closer to the speakers than the walls? It seems logical that an elliptical or rectangular WG would be better than a round WG for most rooms.
Granted you'd like a smooth and even response regardless. It follows that a typical dome tweeter generally  has equal dispersion 360 degrees, therefore not the optimum for most listening rooms. In my situation, the ceiling is about 7'-10".

[Danny Richie]

Wouldn't it be more optimum to have a tighter control of the vertical response since the the ceiling is typically closer to the speakers than the walls? It seems logical that an elliptical or rectangular WG would be better than a round WG for most rooms.
Granted you'd like a smooth and even response regardless. It follows that a typical dome tweeter generally  has equal dispersion 360 degrees, therefore not the optimum for most listening rooms. In my situation, the ceiling is about 7'-10".

The type of wave guide used usually isn't the issue. What I see often is a wide driver spacing and that of coarse means the crossover really needs to be lower to compensate for that, but it is not always the case. So when you move to a vertical position that represents a little bit of what you will get from a ceiling reflection then you see cancellation in that plane.

Here is an example of a speaker I measured that is time and phase coherent.



Unfortunately that coherency doesn't exist in the vertical plane. The drivers are out of phase.

So the ceiling reflection will show that.

[goskers]

Here is my whole sentence.

"Another problem that is always overlooked by these guys is that the biggest reflection point in the room is typically not the side walls. It's the ceiling. And you want just as smooth and even response in vertical off axis response as well as the horizontal off axis response."

Not referring to anyone specifically but with most large wave guide designs the horizontal is emphasized while the vertical off axis is overlooked.

The most logical counter to the vertical response being as important as the horizontal response is the fact that we have ears on the sides of our heads and not the top and bottom.  Is the vertical irrelevant? Of course not.  Our brain is better at overlooking different arrival anomalies than others.

[Nick77]

These particular 15" or 18" waveguides wave guides work well with a 15" woofer. Time delay? The depth of the woofer and the waveguide are similar and if it's an issue it can be mitigated with dsp or adjust the cabinet a bit.

Well... I will soon see if it works 'cause I'm just finishing up my bass bins for the TD15Ms'.  The SEOS18/compression drivers waveguides will be mounted on top in removable boxes that will allow a little adjustment for depth spacing. The SEOS18 holds pattern control to ~ 650hz. The 1" comp. driver I'll use goes down to 650hz so it'll be about there where I'll crossover.  Since I'm crossing this low maybe time delay issues won't be so important.
If you go elsewhere there are many testimonials to the sound quality of similar SEOS based speakers. Geddes speakers employ a round WG which have a greater center to center distance than SEOS and he also had to deal with time delay issues too.

Do you have a build thread going on somewhere? Sounds really similar to my Pi4 build and Mikes modified 2226 design.

[rajacat]

Do you have a build thread going on somewhere? Sounds really similar to my Pi4 build and Mikes modified 2226 design.

No build thread yet. I'm not sure which forum to use for the build thread. I am documenting much of the build with photos.

[JDUBS]

Are you referring to these guys linked in the above article?

Nice intentionally manipulated context! 

-Jim