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[Grant Rider]

Tom Danley wrote on Tue, 09 October 2007 14:54

Grant brings up a good point too, the Tapped horn only has an advantage when the mouth area is small enough to cause ripples in a regular horn.

Thanks for the confirmation. That's what I thought.

Will you be sending any of your horns to the subwoofer shootout in Tulsa? It would be interesting to compare them side by side with others.

Tom Danley wrote on Tue, 06 September 2005 20:38

The only Tapped Horn comparable in size to the Lab sub is the Vortex, also a Tapped horn which is a little smaller (42 by 42 by 22 ½ in).  I couldn’t find the measurements someone sent me of their single Lab @ 1meter but one for one the Vortex would have less ripple and greater sensitivity. Once you had say 6 Labs (where the mouth is big) then they would be about 50% efficient and would be hard to beat electroacoustically.

It looks to me like both the Labsub and the Vortex would be maxxed out at about 50% efficiency, so both would be about equal in size and efficiency. There is enough mouth area that there shouldn't be any response ripple in a properly designed traditional basshorn so that's a wash too.

What I'm taking from all this is the tapped horn philosophy is probably good for making small basshorns, or when you need to be able to use very few of them. It's a hybrid horn/pipe approach that is great for situations where space is limited. I think once you start grouping horns together, the benefits start to go away because mouth size becomes large enough that mouth reflections aren't a problem. A basshorn begins to work properly when mouth size is big.

The acid test is in the measurements. Does anyone have side by side measurements of tapped horns in groups compared with traditional basshorns in groups of the same size? It would be interesting to see comparisons of say 20 cubic feet to 200 cubic feet, single horns all the way up to large groups, keeping total cabinet volume constant.

Will there be any tapped horns at the hornsub shootout in Tulsa for this purpose?

[Vince Byrne]

Dan Kok wrote on Mon, 08 October 2007 20:54

It seems that others have also thought to introduce the out of phase signal from the back of the driver into the horn at a certain point to smooth out the ripples. How this might affect a patent application I don't know, I'm not a patent lawyer or examiner and I don't hold any patents.

I'm not an examiner, but I've haggled with a few, I have (non-audio related) patents, and I help my colleagues with the patent process.

I have one patent that issued where the examiner clearly should have rejected it based on art that I hadn't been aware of and that he brought forward. He just didn't understand the art. On the other hand, I have seen a few cases where the examiner rejected applications based on art that didn't apply because they didn't understand the art.

In theory, you only need one new idea to claim in an invention to get a patent. Let's say I have an invention has components A-E where:

A = everybody does it
B = a few people have done it
C = Patented in 1953, patent has expired
D = Patented in 1999, patent abandoned as the owner didn't pay the required fees
E = I did it

then I can file an application claiming A+B+C+D+E and get a patent. But understand that I can't protect A+B+C+D without E because A+B+C+D is known from prior art.

Now think about Tom's tapped horn where clearly "B = a few people have done it" applies to "introduce the out of phase signal from the back of the driver into the horn at a certain point to smooth out the ripples" If that is all there is to Tom's claim I'm sure the patent application will be rejected. But I'm also sure that isn't all there is to Tom's claims.

[John Roberts {JR}]

Vince Byrne wrote on Tue, 09 October 2007 12:14

I'm not an examiner, but I've haggled with a few, I have (non-audio related) patents, and I help my colleagues with the patent process. I have one patent that issued where the examiner clearly should have rejected it based on art that I hadn't been aware of and that he brought forward. He just didn't understand the art. On the other hand, I have seen a few cases where the examiner rejected applications based on art that didn't apply because they didn't understand the art. In theory, you only need one new idea to claim in an invention to get a patent. Let's say I have an invention has components A-E where: A = everybody does it B = a few people have done it C = Patented in 1953, patent has expired D = Patented in 1999, patent abandoned as the owner didn't pay the required fees E = I did it then I can file an application claiming A+B+C+D+E and get a patent. But understand that I can't protect A+B+C+D without E because A+B+C+D is known from prior art. Now think about Tom's tapped horn where clearly "B = a few people have done it" applies to "introduce the out of phase signal from the back of the driver into the horn at a certain point to smooth out the ripples" If that is all there is to Tom's claim I'm sure the patent application will be rejected. But I'm also sure that isn't all there is to Tom's claims.

Indeed, that concept is classically explained as the 4 legged stool, improvement patent over the 3 legged stool.  It doesn't give you any right or exclusivity over the 3 legged stool technology. It does give you control over the 4 legged "improved" invention, as long as you can legally secure use of the 3 legged technology too. This is a pretty common game in big business to trade rights in improvement patents to gain rights to basic technology patents.

One of my patents is an improvement on Dugan's automatic mixer invention. Since his original patent had expired the basic technology is public domain, so I was able to add another leg to that stool, and protect at least my improved version. Perhaps of interest, I didn't get a second patent related to that design we filed for because it was superficially similar to an old tube schematic the examiner uncovered. While there was no real functional equivalence between the 1930's circuit and my modern invention, it looked and waked like a similar enough duck, so was close enough for me to abandon.

My understanding of the law is that you not only shouldn't pursue a patent if you become aware of conflicting prior art, but are supposed to notify the patent office if you later discover such a conflict in one awarded to you. You appear to be saying that the examiner's search discovered art that in your opinion conflicted with your claims. You agreed with their assessment but argued against it anyhow, and won, despite your personal understanding that you were wrong.

Perhaps I am reading you wrong, or don't fully understand the law, but I'm not sure I'd brag about this on a public forum, since you are at a minimum diagramming for someone else how to reverse your patent (order the patent wrapper, read the examiners citations and arguments to find the conflict, in plain sight, you are talking about).  

If anything recent changes in patent law are swinging the pendulum in the direction of making it easier to overturn patents. This is good or bad depending on there you sit.


JR

[Iain_Macdonald]

Hi all.

Just wait until the implications of Supreme Court: KSR vs Teleflex ruling kicks in.

Iain.

[Tom Danley]

Hi Grant

Consider that 50% efficiency is a horn “benchmark”, where half the actual  power is radiated as sound, the other half is heat.
From that it may not be clear that going from the very difficult to reach 50% mark to the impossible 100% mark only results in a 3 dB increase in sensitivity.
It is possible to make a horn that is somewhat greater than 50% efficient if it is large enough acoustically and the bandwidth is limited.

Also, it may not be clear that when you say a horn has a smaller mouth, that this mouth is part of a horn that is wrapped up in a cabinet too.  
It strikes me that maybe the white paper doesn’t explain clearly enough what the advantage of the Tapped horn is.

Hoffman’s iron law (the wall of science) limits the maximum efficiency possible given the box volume and low cutoff.
Take a subwoofer like the popular JBL-728 for example that has real measurements, go to the web site and pull up the pdf which has a measured response curve.

http://www.jblpro.com/srx700/728S.htm

Take a snapshot with your pdf viewer, up to 200Hz, save it and stretch it out so it is easier to read in the subwoofer range.

This box has 2X cool18’s in each and occupies 19.25 cubic feet.

On the other hand, take the TH-115, it has one 15” and occupies 14.6 Cubic feet, so its not exactly fair with the 115 being somewhat smaller and lighter.
Compare the sensitivity for one box in the subwoofer range at a few spot frequencies (eyeballing from the graphs).

            TH-115              728

35Hz      96                      93
40Hz     102                     96  
45Hz     105                     97
50Hz     103                     97.5
60Hz     104                     97
80Hz     106                     98
100Hz   111                     99

So, given the TH-115 is both smaller in volume, lighter and only has one 15 inch driver, what is it that makes it about as sensitive as 4 close coupled 728’s would be (+6dB) ?  
That difference (and the reduced phase shift near the low corner) is the Tapped horn advantage.  
Below is a measured response for 4 TH-115’s, measured at 10 meters, each driven at 28VRMS which into an 8 Ohm nominal load (like these) is 100W each.
This is +6 dB over what would give our equivalent 1 W sensitivity, subtracting 6 dB, one finds that say at 50Hz, the 1W sensitivity is 108.9 dB, just about   50% = 109dB
Now, with 58 cu/ft to work with, can you find any other way to get that kind of sensitivity, with that cutoff?  

Given the measured response of a 728 here looks like the mfr’s curve if you add 20dB (for 10M distance)
http://www.prosoundshootout.com/Measurements/2006/JBL_SRX728 S_response.gif

How do these horns look in comparison adding 20dB.
http://www.prosoundshootout.com/Measurements/2006/Tuba36_qua d.gif

http://www.prosoundshootout.com/Measurements/2006/12Pi_dual_ response.gif

http://www.prosoundshootout.com/Measurements/2006/BASSMAXX_T ripp_dual_response.gif

Anyway I am sorry for the long explanation, hope it isn’t too much of a commercial.
Best,

Tom Danley

[Les Webb]

Nothing against you Tom but it really aggravates when people put that Tuba 36 graph up there.  Wayne uses it quite often when comparing subs also.  

The person who built those subs was told numerous times NOT to use the drivers he used.  He refused to listen, built a bunch of one note wonders, and now everybody uses that graqh when comparing Tuba 36s.

That graph is not representative of a Tuba 36.  Load a few EVM12s into a 12pi or put an EVX15b in a TH115 and they will do poorly also.

Les

[Pascal Pincosy]

Also the driver used in the Bassmaxx Trip in that measurement is not the production driver. Take a look at the measurements of the Trip with the production driver and you'll see a very different response.

I also think it's pretty weird that Danley Sound Labs is using measurements from the ProSoundShootout as promotional materials, while at the same time Danley Sound Labs has recently spent a great deal of time attempting to discredit the testing procedures used at that event...

[Vince Byrne]

John Roberts  {JR} wrote on Tue, 09 October 2007 14:32

...I didn't get a second patent related to that design we filed for because it was superficially similar to an old tube schematic the examiner uncovered. While there was no real functional equivalence between the 1930's circuit and my modern invention, it looked and waked like a similar enough duck, so was close enough for me to abandon.

Part of the legend I heard working within Bell Labs is that when they invented the transistor they then frantically patented transistor improvement varients of all the common tube circuits. Good, bad, or indifferent, you may have shortchanged yourself a bit on this.

Quote:

My understanding of the law is that you not only shouldn't pursue a patent if you become aware of conflicting prior art, but are supposed to notify the patent office if you later discover such a conflict in one awarded to you.

I don't really know exactly what happened, but I'm sure the IP lawyers find it more beneficial to their careers and wallets when patents issue as opposed to when they don't. The first office action on this correctly rejected all claims except one based on prior art and rejected the remaining claim as obvious based on prior art. I tended to agree and told the IP lawyers to drop the case. Then about 18 months later I start to get ads in the mail trying to sell me a plaque (I have yet to get notice from my company of a patent issuing before getting plaque ads).

In any case, the company owns the rights and I got the paycheck. The companies money was already sunk cost, they aren't paying the maintenance fees, and none of the IP lawyers were excited about doing anything more on this.

[Tom Danley]

Hi Pascal

I wasn’t aware these had the wrong drivers in them also.
I will look for the measurements, thanks.

Yeah, Wayne’s data was handy (linkable) and with the known quantity (the JBL) aligning, seemed credible (unlike the later one).  
I wouldn’t exactly say I am using it for promotional materials however, just a source of a fairly rare commodity, actual measurements.
I didn’t know that the Tuba’s and Trips didn’t have the proper drivers however.

I have sent speakers to shootouts before and think proper measurements and side by side comparisons vital in getting to reality.  Personally Wayne and I seemed to exhibit a certain “friction” which goes way back and my daughter has surgery that weekend so I couldn’t go anyway.
I was thinking of sending a new box but the first samples, while impressive sounding, were I felt too far short of the computer model.    I (hope) figured out what wasn’t right and have a second set in the works.  These boxes should in a stack of 4 have about 10dB of forward directivity gain in addition to sensitivity and a lower cutoff, but hey, they aren’t measured yet.
Best,

Tom Danley

[Tom Danley]

Hi Less

I wasn’t aware those were the wrong drivers but did see them as actual measurements, of which there are few around.

On the other hand, if these aren’t the right drivers, then at least they are still measurements.
What do you see for his representation of a TH-115's on his website?
How close is it to the actual measurement?
Best,

Tom