In my opinion the question above is the main issue, and I don't accept your answer. "Radiating" versus "injecting" is a bit too much hand waving IMO, and "pressure follows laminar flow"? I don't think that would stand up very well under investigation. I would bet that there is a significant amount of HOM due precisely to the midrange ports.
And not all reviews of the Synergy are as glowing as they are here - I refer you to the direct comparison between the Abbey and a Unity (I believe) over at Audiogon or somewhere I forget - by people other than the owners. I'm not knocking Tom's design for what he designed it for, extremely high outputs, it probably excels at that, but the problems created to get to these outputs are not easily resolved. I have asked for "good" data on this design so many times that I stop asking, so I am not sure of the level of the problem, but I do know that theoretically there is going to be one and from reports that I have read its there. I don't think that we can so easily wave our hands about and say that there isn't one.
I have no issue with better drivers at all; if you can suggest some I will buy them and try once I have it all working to my satisfaction as it stands, ie Miscos and DE25.
But at the same time it reinforces the point that until you have wrung the best performance out of the topology, changing passives beyond decent PP caps and coils is hand waving.
I have 4 AE TD15 drivers, proto-ing with a pair/side as I recall speaking with William and he never changed out his single 15LW1400 for a pair. I had intended to go W-U-W, but W-U may be more than enough for a 20m^2.
There needs to be a clear distinction made between a Unity and Synergy horn. While they might look similar, the Synergy has some very exacting criteria that make it quite different. A comparison between a Unity and Abbey is not very relevant because the Unity has not been available for some time now. Any such comparison should be made with a Synergy horn and not the outdated Unity horn.
Depending on a person’s taste and goals opinions will always vary. I’ve never seen a product get 100% positive reviews before. There is always going to be a critic that is prejudice toward the product, or it just doesn’t work in their setup. My goodness, I know the OS wave guide concept has received at least the same level of condemnation that Tom got with the original Unity concept. However, in both cases as people gain experience with the product the acceptance level begins to grow. However that acceptance came too late to save the Unity. The hostility that is shown to each new product grows very tiresome.
I agree that there is a level of frustration in the lack of “good and solid” data that we all seek. Until the data is available we will just have varying opinions on what is significant and what is not. It is my opinion that the perceived HOM generation due to the midrange ports is greatly exaggerated.
Depending on a person’s taste and goals opinions will always vary. I’ve never seen a product get 100% positive reviews before. There is always going to be a critic that is prejudice toward the product, or it just doesn’t work in their setup. My goodness, I know the OS wave guide concept has received at least the same level of condemnation that Tom got with the original Unity concept. However, in both cases as people gain experience with the product the acceptance level begins to grow. However that acceptance came too late to save the Unity. The hostility that is shown to each new product grows very tiresome.
I agree that there is a level of frustration in the lack of “good and solid” data that we all seek. Until the data is available we will just have varying opinions on what is significant and what is not. It is my opinion that the perceived HOM generation due to the midrange ports is greatly exaggerated.
Earl I'm puzzled.
Are you talking about the possible HOMs produced by the waves from the HF driver encountering the MR range ports? They are irregularities on surrface of the horn but are quite small compared to the size of the whole apparatus and some inches away from the throat of the HF driver so I'm thinking it's possible the HOMs produced might be quite low level compared to the direct sound.
More hand waving: Given the symmetries of device's shape and position of radiating apertures at that narrow end of the horn, how much of those HOMs might cancel each other out?
Given the wavelengths under consideration, wouldn't the Synergy midrange ports be analogous in function to a phase plug on a compression driver? I've got a B&C de500 in front of me and it doesn't look like sound waves in it's usable range could be produced until the pressure impulse exits the phase plug. Similarly, in the synergy type horn I don't see how much in the way of HOMs could be produced at that point because the port mouth is the sound radiating surface. Have I got that right?
Are you talking about the possible HOMs produced by the waves from the HF driver encountering the MR range ports? They are irregularities on surrface of the horn but are quite small compared to the size of the whole apparatus and some inches away from the throat of the HF driver so I'm thinking it's possible the HOMs produced might be quite low level compared to the direct sound.
More hand waving: Given the symmetries of device's shape and position of radiating apertures at that narrow end of the horn, how much of those HOMs might cancel each other out?
Getting time to post has been tricky, so lots to respond to.
So far, I haven't done all that much physically to the U15's. I've removed the grilles (mandatory, they sound horrible with the grilles on), and made a hacked-up homebrew foam plug modeled after the ones that Geddes uses. I have significantly more ambitious ideas about what could be done, but I haven't yet undertaken them; this is mostly because everything to this point has been 'reversible', and I can still sell the U15's as PA cabinets. I strongly suspect that the next steps will be non-reversible (starting with a new cabinet), and will kill any resale opportunity. My resale thoughts have nothing to do with the performance of the U15's, but solely due to the fact that I'm simply not listening to them all that much due to their location in the basement, and so I'm wondering whether the time/effort/money I'd spend on the next round of upgrades/mods might be better allocated to a system that fits our main living space better (more on that later).
My reference to the U15's as a 'project' is more a caution against expecting to pull them out of the box and hook them up and have 'perfect sound forever'. They really need EQ IMHO, which implies measurement capability and a way of applying EQ transparently.
The ideas for further mods include
- breaking out the xover connections to allow passive bi-amping (the U15s are bi-ampable in stock form, but this bypasses the woofer xover so you have to provide an active xover on the woofer branch).
- ditching the passive xover entirely and doing a FIR-based DSP xover (in theory I have all the necessary pieces for this, but it would be a major undertaking)
- new cabinets built directly into my corners, possibly including a back-set on the horn to allow a new large-radius mouth termination
- possibly some investigation on modifying the midrange ports in line with the ideas in the Synergy patent. I'd be really hesitant on this though, as the horn may not be replaceable.
So far, I haven't done all that much physically to the U15's. I've removed the grilles (mandatory, they sound horrible with the grilles on), and made a hacked-up homebrew foam plug modeled after the ones that Geddes uses. I have significantly more ambitious ideas about what could be done, but I haven't yet undertaken them; this is mostly because everything to this point has been 'reversible', and I can still sell the U15's as PA cabinets. I strongly suspect that the next steps will be non-reversible (starting with a new cabinet), and will kill any resale opportunity. My resale thoughts have nothing to do with the performance of the U15's, but solely due to the fact that I'm simply not listening to them all that much due to their location in the basement, and so I'm wondering whether the time/effort/money I'd spend on the next round of upgrades/mods might be better allocated to a system that fits our main living space better (more on that later).
My reference to the U15's as a 'project' is more a caution against expecting to pull them out of the box and hook them up and have 'perfect sound forever'. They really need EQ IMHO, which implies measurement capability and a way of applying EQ transparently.
The ideas for further mods include
- breaking out the xover connections to allow passive bi-amping (the U15s are bi-ampable in stock form, but this bypasses the woofer xover so you have to provide an active xover on the woofer branch).
- ditching the passive xover entirely and doing a FIR-based DSP xover (in theory I have all the necessary pieces for this, but it would be a major undertaking)
- new cabinets built directly into my corners, possibly including a back-set on the horn to allow a new large-radius mouth termination
- possibly some investigation on modifying the midrange ports in line with the ideas in the Synergy patent. I'd be really hesitant on this though, as the horn may not be replaceable.
Be careful drawing conclusions on this. That comparison is the session I referred to in my earlier post, and was between the Yorkville U15 and the Abbey. The Yorkville is a Unity design (not a Synergy), and is not a Danley design at all but was done in-house at Yorkville with a simple license of the patent. It's also a cost-compromised design, although a very well done one.
I think this is a fair question, but one that is going to be rather difficult for anyone at a DIY level to answer with any authority. I think a simple measurement of the off-axis response of the tweeter in isolation and the mids in isolation might show some things, but even that is a potentially tricky undertaking if we want sufficient resolution, and won't provide the whole picture anyway.
There is also the practical problem that all of the Unity/Synergy designs are aimed at Pro/PA use, and so don't have the same degree of refinement in terms of mouth termination and diffraction control, making it a bit tough to separate out problems in the Unity/Synergy arrangement from more conventional problems.
It's always been 'in my plans' to try to do some of these measurements, but finding time has been very difficult and doesn't really look to be any easier in the near future.
That might be an interesting thing to think about, although I'm not sure it would end up being more practical than a simple co-ax. In order to make it small enough for desktop use, you won't get all that much directivity control; which is too bad - directivity control would be a REAL benefit in desktop use where you have a monitor and flat desk surface generating reflections.
I have another 'problem' that would appear to be a good candidate for a Unity. We recently re-arranged our main living area which resulted in a TV placement in which there is literally no place to put speakers on the ground. The ONLY option I have is on-wall or ceiling. I currently have a pair of the Mirage omnisat's placed in the upper room corners, which leads to the idea of building a Unity *into* the upper corners of the room. This would be a 3-sided 90-degree setup. One of the possibilities I thought of is to omit the third side (i.e. the ceiling) and simply replace it with absorption, giving one tweeter at the apex, and then a 2-sided symmetric array of mids and woofs - one either wall. IF you can keep the distances between drivers and from driver to ceiling in the 1/8 - 1/4 wavelength range, I think this might work quite well. My biggest concerns are
a) whether it will be realizable with a passive xover due to the variable boundary loading.
b) 'mouth termination'. The cabinet would have to be deep enough to contain the drivers, which gives you a 3-4" mouth transition. (plaster over brick walls, so no opportunity to flush-mount the drivers which would be the ideal approach)
c) bandwidth. This would have to be really small, which probably means sealed. You may not get enough bandwidth/headroom to make it workable.
The practical advantage to a 2-sided setup is that it is much easier with conventional hi-fi drivers.
Another idea I've been kicking around for this design is whether the bandpass arrangement on the mids is actually necessary or not. What about the idea of omitting the bandpass ports, and simply covering the mids (and woofs, if a 3-way) with a speaker grille material which is fine enough to moderate any diffraction effects on the tweeter? Possible? Dumb? Dunno, but it would certainly simplify things.
Of course, the corner-mounted idea may well also work as computer speakers too 🙂
Last edited:
This is what I meant, but it would go both ways as well. The HF "see" the mids ports as a discontinuity in the transmission line and a reflection/diffraction WILL occur. And likewise, the mids will see the compression driver. At what level? thats TBD, but we just cannot wave our hands arround and say that the problems don't exist, because they will.
I don't see how HOMs could cancel, at a point sure, but global cancellation of two displaced wave sources in a 3 dimensional field is not possible - they interfer, but cannot cancel.
I didn't draw any conclusions, I'm trying to keep others form doing so as well. The comments in this thread sound way too biased towards the "synergy design" IMO.
Measuring the potential problems wouldn't be hard, but no a DIY is not going to do that and the manufacturer is certainly not going to show the warts. So in effect we have never seen data on the Synergy either way.
And your point is exactly my point. The Summa was designed to be the cleanest possible reproduction of a sound source, not the maximum output. Tom's designs all go after maximum output and compromise on performance to achieve that. Both design objectives are fine, but you have to remember that they are different and should each excel in that venue for which they are targeted. To your last point, its all one design and doesn't require "seperat(ing) out problems in the Unity/Synergy arrangement from more conventional problems". A problem is a problem.
Last edited:
I remember when the original Unity was being discussed on the old "Bass List" and don't recall very much condemnation at all. Tom and Nick were very respected members and the only problem I recall was that some had never heard a good horn and certainly didn't understand initially how the Unity concept would work. Generally, I'd say the people were pretty enthusiastic about the whole thing, so I'm not sure where the "condemnation" you speak of was generated. I personally wanted to buy a pair, IIRC the Bass List members were offered a special price, but unfortunately couldn't afford it at that time.
Best Regards,
TerryO
Last edited:
Just a request, can anyone give a URL for the Unity and Synergy patents? I will admit that I've never had much luck doing searches and my computer has gotten pretty "buggy" to the point it occasionally just times out.
Thanks in Advance,
TerryO
Thanks in Advance,
TerryO
If your intent is to evaluate the speakers as fixed offerings, then I wouldn't disagree - the source of a problem may be of academic interest, but it doesn't change the performance.
From a DIY perspective though, I don't quite see it that way. What I mean is that it's quite feasible for me to modify my U15's by building out a 2-3" radius termination on the horn mouth. This should be a noticeable improvement in reducing cabinet-edge diffraction as well as better impedance termination of the horn. To me, this is addressing a practical design fault of the U15, which is completely independent from any problems that are inherent in the midrange radiation mechanism and/or any impact the midrange holes have on the compression driver.
Now, you'd be correct in saying that this is now really a new creation and the performance wouldn't necessarily be indicative of other "Unity" systems, but since this is a DIY forum I think it's reasonable to differentiate between things that are potentially fixable and those that are inherent in the design.
Agreed - I was talking about fixed offerings as that's what the title of the thread implies. If we are talking about theoretical extrapolations on existing designs, then most of what has been said is irrelavent. There are no extrapolations on the Summa design that I am aware of and it ONLY exists as a "fixed offering". It then should not be compared to something that is a moving target.
Here's how you can cheat
The trick is to use a boundary to extend the waveguide. Here's an elliptical OS waveguide in my car, using the windshield and the dash to extend the curve. I built this one three years ago
The size of this mold is ridiculous, but check out the edge. You can see that the dash and windshield are virtually the exact same angle. That's why you can cut it down to size.
In 2009 I *really* chopped the waveguide down to size. I seriously believe you could remove 75% of the waveguide if you terminated it very VERY carefully to the boundary. This waveguide actually has superior polar response compared to the big one from 2006, even though it's half the size.
An externally hosted image should be here but it was not working when we last tested it.
For a computer speaker, I would use two or three LCDs, and the monitor would extend the waveguide. With 24" LCDs, this makes for a VERY big mouth.
I have run them as two ways. With limited testing, I find a slight preference for running with the mids. Can't say what that is due to, as I haven't done enough testing to know much - even if that's a consistent preference. My sense is that it's due to the larger range covered in one horn. I think this is an attribute of the multi-driver horn approach which does distinguish it from a single driver horn that is crossed higher to a large woofer. So it's not *just* a matter of designing for highest output. Not claiming better or worse that the Summa approach. I have said before, that if I were starting over I'd go for the lower complexity, as the differences are fairly subtle and I could happily live with either.
As far as creating diffraction from the compression driver, the size of the mid holes will be a factor. Mine are much smaller than the original - modified as per John Hancock: http://www.diyaudio.com/forums/multi-way/17642-first-pics-new-speaks-2.html#post628588
As it stands, I have very little flexibility on where I can cross the mids with the compression driver, as there is little overlap. I'd like to cross somewhat higher but that means moving the entry point of the mids - which is as close now as it can get with the standard mids. I plan to try a smaller mid and mount on on the corner of the horn, instead of the flat of the walls. I could use a single entry slot in the corner, for each driver, instead of two holes, and move it closer to the apex. A single slot vs. two holes would minimize diffraction effects, as well as better normalize the path length from cone to entry hole, for better "phasing".
I'm not sure the distortion performance of the mids should be too important, as they are limping along at the low end of their capacity. But, if I can do better, fine. Which Peerless were you referring to?
Sheldon
I have the Synergy patent application in PDF format. I can't post it here because 1.22MB size is too large for the forum.
Romy did post it on his web site - I hope he does not mind me pointing you guys to it.
http://www.goodsoundclub.com/PDF/Synergy_Patent.pdf
Once you do read the Synergy application a lot of things become clear. Not all of it is spelled out; you just need to be able to connect the dots. It could be cool to post the application paragraph by paragraph in a new thread. We all could then analyze it together and get a better overall understanding.
The Unity horn patent is located here--> http://www.pat2pdf.org/patents/pat6411718.pdf
U.S. patent 6411718
JLH,
Thank you very much. This will give me something to read and pounder in the days (months? I'm a little slow.) to come.
Best Regards,
TerryO
Thank you very much. This will give me something to read and pounder in the days (months? I'm a little slow.) to come.
Best Regards,
TerryO
I think Tom is going to have a lot of trouble with the claims in the Synergy patent because they appear to me to "read on" the Unity patent. If you read the two sets of claims the second set (Synergy) are very very broad compared to the first set. This would then appear to be an attempt to broaden the applicability of the Unity patent - well worth trying. The Patent Office frowns on such things, but hey, you never know what they will end up accepting. I'd be very interested in reading the final claim language if it issues.
I have the previous Exodus driver (ex-6.5) and I think it's an interesting candidate for the woofer in a 3-way Unity, but is entirely unsuited for use as a mid.
This new Tang Band might be a more interesting alternative to the W2-852 due to the aluminum cone.
Parts-Express.com: Tang Band W2-800SL 2" Aluminum/Mg Full Range Driver | Tang Band W2-800SL aluminum cone fullrange Tang Band TB Speakers compact speaker neodymium driver
detailed specs here
http://www.tb-speaker.com/detail/1230_04/w2-800sl.htm (if specs are to be believed Fs=160, Qts=0.25)