Wayne
First, we stoped talking when you insulted me and I'm not sure that I am up for playing that game with you again. If you don't discuss this issue in a calm, polite and respectful manner I will stop responding promptly.
I don't completely accept your assumptions, which need to be dealt with first. I am not convinced that the nulls interact with the polar pattern in the simplistic way that you suggest. I am not sure that they don't either. I have no data either way, but I'm not going to simply accept your statements based on hand drawn figures etc. Until I see some real data or simulations, I'm not going to use a narrow vertical pattern because of the nulls.
There is however another reason for narrower vertical control and your mentioned both of those - closer spacing and less floor and ceiling energy.
If it were not so impractical I would probably test an elliptical waveguide, but it is so impractical to do that I have balked at it. All of my tooling for the foam plug and the waveguide contours become obsolete for the elliptical situation and have to be replaced with new tools of a very high degree of added complexity - and cost. At this point, I simply cannot afford the cost or the time to pursue this concept as, at best, it would be a marginal improvement on what I already have. (Read the reviews if you doubt that statement.)
So ideally, I would use asymmetric coverage waveguides, practically, they will be axisymmetric for quite a while.
We had planned to do this at Ai, among a whole list of other things. It takes a lot of resources to do research - it isn't free (unless you are a DIY with nothing better to do).
When I first designed the Summa, I didn't know how to do an elliptical waveguide. I do now. Thats why it started out round.
First, we stoped talking when you insulted me and I'm not sure that I am up for playing that game with you again. If you don't discuss this issue in a calm, polite and respectful manner I will stop responding promptly.
I don't completely accept your assumptions, which need to be dealt with first. I am not convinced that the nulls interact with the polar pattern in the simplistic way that you suggest. I am not sure that they don't either. I have no data either way, but I'm not going to simply accept your statements based on hand drawn figures etc. Until I see some real data or simulations, I'm not going to use a narrow vertical pattern because of the nulls.
There is however another reason for narrower vertical control and your mentioned both of those - closer spacing and less floor and ceiling energy.
If it were not so impractical I would probably test an elliptical waveguide, but it is so impractical to do that I have balked at it. All of my tooling for the foam plug and the waveguide contours become obsolete for the elliptical situation and have to be replaced with new tools of a very high degree of added complexity - and cost. At this point, I simply cannot afford the cost or the time to pursue this concept as, at best, it would be a marginal improvement on what I already have. (Read the reviews if you doubt that statement.)
So ideally, I would use asymmetric coverage waveguides, practically, they will be axisymmetric for quite a while.
We had planned to do this at Ai, among a whole list of other things. It takes a lot of resources to do research - it isn't free (unless you are a DIY with nothing better to do).
When I first designed the Summa, I didn't know how to do an elliptical waveguide. I do now. Thats why it started out round.
soongsc said:
The diaphragm is fairly rigid up until about 10 kHz. So none of the HOM below there will be coming from diaphragm modes. Above that I don't worry about too much.
It would be possible to make a device that structurally generated HOMs, but why would someone do that? Just make it rigid and be done with it. Why worry about things that are so easy to correct?
Now the HOMs that are generated within the waveguide - which is the vast majority - those ARE very hard to control and I pay a lot of attention to this in my designs. I don't worry about the insignificant things in loudspeakers or in life.
Patrick,
Regarding your question about a 90 degree bend in a waveguide.
The "packaging problem".
How about a bend before the waveguide? A sort of 90 degree "phase plug" before the waveguide.
I'm thinking if the overall cross section of the duct(s) was much smaller than the wave lengths of interest, then acoustical phenomena such as HOMs wouldn't come into play. Although turbulence might be a problem at the bend(s).
This is really rough and ready but might be an idea to play with.
Regarding your question about a 90 degree bend in a waveguide.
The "packaging problem".
How about a bend before the waveguide? A sort of 90 degree "phase plug" before the waveguide.
I'm thinking if the overall cross section of the duct(s) was much smaller than the wave lengths of interest, then acoustical phenomena such as HOMs wouldn't come into play. Although turbulence might be a problem at the bend(s).
This is really rough and ready but might be an idea to play with.
If you look at the forces involved Soongsc, even fairly flimsy plastic injection moldings are more than stiff enough to ensure that the structural vibrations they might have contribute so little to the output as not to matter, i.e. they are very small in comparison to the effects of diffraction and reflection within the horn.
Exponential horns have a very abrupt impedance drop at their mouths which causes a lot of reflection, in horns with generally conical type contours with flared mouth sections the impedance transition is much more gradual and the reflection a lot less, just look at the impedance curves of various shapes of horns.
rcw
Exponential horns have a very abrupt impedance drop at their mouths which causes a lot of reflection, in horns with generally conical type contours with flared mouth sections the impedance transition is much more gradual and the reflection a lot less, just look at the impedance curves of various shapes of horns.
rcw
rcw said:
But you have to look at the impedance mismatch at the mouth not at the throat. I don't think that what you are saying is true. I would expect that the mismatch at the mouth would be almost independent of waveguide shape (assuming the same exit angles) and depend only on the mouth area and the impedance of this wavefront. This impedance is complex, varying in complex ways across the mouth and so the reflection is also complex, meaning that HOM are generated here by this reflection. Mouth reflection is a complex problem and it is simply best to radius the mouth and minimize the whole problem altogether.
gedlee said:
I don't recall ever insulting you. If you felt slighted, I'm sorry.
What I do remember was people complaining very loudly that they felt you were rude to them. I always defended you behind the scenes at AudioRoundTable.com. You were always welcome there, but sometimes sparks would fly. We surely didn't want that place to decend into a cesspool of insults like some audio messageboards can be. Sometimes, it seemed like it was difficult to keep the peace.
My concern was always that you had a lot of useful ideas, maybe more than anyone in the industry today, but that your communication style sometimes put people off.
It's like you would insult someone cruelly, and then when they would tell you they thought you were a jerk for doing it, you would chastize them for insulting you and threaten to never speak to them again.
As for my personal thoughts about you, I have a great deal of respect. I'd like consider you one of my friends. We have had some friction, but I think we did a great job of keeping things very civil, both privately and in our public communications. To me, that shows character.
gedlee said:
OK, well, I didn't ask you to agree, accept assumptions or anything like that. I have made measurements and I've published them on my website. I've also seen your measurements published on your website. My illustrations were simply a way of making each of those observations generic, not by naming speakers by brand and model but by showing the radiation patterns from various types of speakers, each with different kinds of horn flares.
It wasn't "arm waving" or assumptions that guided me to make those illustrations, it was a simplifying expression of measurement data that has been gained after dozens, more like hundreds of measurement samples. The illustrations reflect what was seen in the measurements, and they agree with what you have published on your website as well as what I have published on mine.
gedlee said:
That is the biggest thing, I expect. I can appreciate that and I understand completely.
gedlee said:
I've heard your speakers and read the reviews. I liked the sound of your Summas. Frankly, I always thought they sounded a lot like my four Pi model, which also gets rave reviews and has been one of my most popular models over the years. Both produce smooth response through a very wide horizontal arc, filling the room with balanced sound. Both are efficient and use powerful drivers that are loafing along at home hifi levels. They're natural sounding and easy to listen to. Take that as a compliment, as it was intended.
gedlee said:
You, Duke and I are all traveling basically the same road. We have our differences, but the largest part of our design choices are the same. Frankly, I took a great deal of comfort when you introduced the Summa's and Duke later started making the Jazz Modules. Now there are more people familiar with this design style and I think that's a good thing.
Frankly Wayne I don't go to AudioRoundTable anymore and I won't go there again so you can tell my critiques not to worry.
And I didn't think that your speakers sounded like mine.
And I didn't think that your speakers sounded like mine.
Pi Speakers
I don't think your critics are worried. In fact, I don't think anyone really cares. There were just some ruffled feathers, much like what I see here. From what I can tell, nothing much has changed.
You have never heard my four Pi loudspeakers. You may have heard my seven Pi model, which is a larger three-way speaker with a compression driver and horn tweeter, a large midhorn and a bass bin. I also had two Pi towers at that show.
The seven Pi speaker is larger and more expensive than the four Pi speaker, and the two Pi tower is a less expensive model.
All are available as kits or finished speakers, and I also provide plans free of charge, with no purchase necessary. I've always done this with all my designs, as this is about the love of great sound for me. Distribution of my plans is treated like the GPL open source model used in the IT world.
I notice you are starting to make kits now too. I wish you all the best with that.
I don't think your critics are worried. In fact, I don't think anyone really cares. There were just some ruffled feathers, much like what I see here. From what I can tell, nothing much has changed.
You have never heard my four Pi loudspeakers. You may have heard my seven Pi model, which is a larger three-way speaker with a compression driver and horn tweeter, a large midhorn and a bass bin. I also had two Pi towers at that show.
The seven Pi speaker is larger and more expensive than the four Pi speaker, and the two Pi tower is a less expensive model.
All are available as kits or finished speakers, and I also provide plans free of charge, with no purchase necessary. I've always done this with all my designs, as this is about the love of great sound for me. Distribution of my plans is treated like the GPL open source model used in the IT world.
I notice you are starting to make kits now too. I wish you all the best with that.
Wayne Parham said:
Darn! There's no smilie with a hammer hitting a nail on the head!
I'm trying to follow the thread here, and gain some education on the benefits of a waveguide for home hifi. Is the only real benefit directivity?
Well, the worst nightmares of mind are caused by diaphram resonances above 10KHz. They are buried in the slow decay of lower frequencies untill the decay of lower frequency is improved to a point when these resonances above 10K clearly stand out. I don't know how the spectral decay looks within the first 0.4ms, but this is where the differences are often seen.gedlee said:
Since you indicated that HOMs are more significant when the guide is wider, I just pointed out the correlation with the structural modes. If structural modes were not an issue, I see no reason why HOMs would increase with wider guides, rather, it should decrease due to wider dissipation of any reflections that may occur in the guide.
I fully respect your work, and cannot speculate how significant the tradeoffs were when you used foam. But I would like to see what the can be accomplished without it. I'm sure you will say that you have tried all things, as with many designers with so many years of experience in any industry would say; we continually see improvements regardless. So I would like to take an open mind approach to things. If there is anything that anyone is trying and you accurately predict at least one thing not so desireable that will occur, then we know that you have done it before.
MJL21193 said:
Difficult, isn't it?
I've realized I'm starting to find this thread rather depressing in a monotonous sort of way, yet laughable at the same time.
I think I've learned all I will from this thread a long time ago..
If anyone replies to this, I'll probably never see it.
Cheers,
Brandin
How would you get an oval waveguide closer to the woofer. I would have thought the long axis of an oval waveguide to be vertical if vertical response were to be narrowed.
Actually I like the concept because it should generate a more uniform wave front. With direct radiators, the parts outside of the vc former is also vibrating and generating sound, this creates a more complicated wave front. The cleaner the wave front, the more clear sound image becomes.MJL21193 said:
It might be just me and my cloth ears but I don't have a problem with direct radiators - domes work fine for me. The few ribbons I've heard sound good too.
I don't see the advantage of going to elaborate lengths to correct a problem (HOMs) that you've created in the first place. Not for home use anyway and for venue PA use, would it be appreciated?
I don't see the advantage of going to elaborate lengths to correct a problem (HOMs) that you've created in the first place. Not for home use anyway and for venue PA use, would it be appreciated?
pooge said:
A rational comment - how refreshing!!
No actually the long axis is horizontal. Thats where the shorter distance comes from.
I too am tiring of this thread, how it diverges from what it was intended to do. This is of course the way of all threads in the end as they attract diversions from the main topic. I would much prefer to stay on topic and if this bores some people then so be it. The primary topic is important and hardly exhausted. I applaud Wayne's post as it was right on topic, and very important, but of course Wayne being Wayne he had to take it elsewhere and make it personal, which of course everyone had to join in on. Oh if human nature weren't so predictable.
The use of asymmetric waveguides is of extreme interest to me and has been for years and I would dearly love to pursue the topic both with actual designs and constructions as well as technical discussions. But the construction part has alluded me for years owing to the exhorbitant cost increase involved in their fabrication. But discussion is important because it helps to hone the design objectives and so perhaps this should be continued in the hope that someday I will have the resources to pursue the actual designs.
The use of asymmetric waveguides is of extreme interest to me and has been for years and I would dearly love to pursue the topic both with actual designs and constructions as well as technical discussions. But the construction part has alluded me for years owing to the exhorbitant cost increase involved in their fabrication. But discussion is important because it helps to hone the design objectives and so perhaps this should be continued in the hope that someday I will have the resources to pursue the actual designs.
MJL21193 said:
Isn't that enough? Of all of the design objectives of loudspeakers I consider directivity to be the most important. If it isn't of interest to you then waveguides are certainly not going to interest you. But if (or when) you realize that directivity is critical, then you will also come to realize that its not so easy to achieve and that waveguides are the only option. Thats where I think those of us who take interest in these posts are at. If you are somewhere else then I suggest that you go somewhere else.
Somewhere else, huh?
I'm interested in the topic, as I have been following it since the start. I asked a legitimate question.
Here's another:
Why is directivity important in a relatively small space?
I'm interested in the topic, as I have been following it since the start. I asked a legitimate question.
Here's another:
Why is directivity important in a relatively small space?
MJL21193 said:
And I answered your question.
Directivity is more critical in a small space because of early reflections. In a small room it is the early refections that interfere with the sound quality. In a nutshell the narrower the directivity the fewer early reflections that there are, the better the sound quality.
In large rooms the need for directivity is completely different and people often get this confused. It is perhaps pure coincidence that one wants the same thing in large and small rooms, because it is for completely different reasons.
See, I'll answer reasonable questions. The snid remarks are unnecessary.
Thanks Earl, I appreciate these concise answers.
I will have to explore this for myself, to see if it makes a reasonable improvement in SQ.
I would like to try it with a regular dome tweeter though, but in your conversation with rcw, you made it seem as though this would not be a good approach.
See, I'm not always snide. 🙂
I will have to explore this for myself, to see if it makes a reasonable improvement in SQ.
I would like to try it with a regular dome tweeter though, but in your conversation with rcw, you made it seem as though this would not be a good approach.
See, I'm not always snide. 🙂