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Old 24th November 2008, 12:42 AM   #1
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Default Critical Tapped Horn Parameters Collaborative

Its seems that the Collaborative tapped Horn Project thread has gone out of Control.

Why don't we start a thread on what the important driver parameters, and ratios are for a successful tapped horn.

The Few Nuggets that I have so far.

Driver:

Should have a higher Fs than intended operating range. (By what amount? an octave?)

Should have a relatively Stiff Suspension (Relatively High RMS?)

Cabinet (horn):

Needs to be a certain Percentage longer than the 1/4 wave of intended low cut. (What is that percentage?)

What sort of Compression Ratio is needed with relation to Driver Sd?


Questions:

What is an Optimal expansion from Throat Tap to mouth.

It would appear that a mouth smaller than the Area of the large end of the horn is useful??? Is there a Ratio for the mouth.

Is a tapped horn that Expands and contracts along its path benificial??

Observations:

I have noticed that many of the first attempts at building a tapped horn appeared to be imitating the DTS-20 but it became obvious upon my own early akabak modeling that they were making their internal path to short.

I built my 3 bend model before, the patent photos for the DTS-20 appeared, and got really lucky how close I ended up. There have been a few out there recently that have been longer paths. Of Various design.

I do see some promising HornResp models posted here but haven't seen too many recent results.

To many people have been modeling their Cabs In Eighth space, and getting bloated predicted results. They should be modeled in Half space unless your putting them in a concrete corner.

I hope we can turn this thread into a relatively un-congested resource for useful tapped horn design info. And links to other useful info.

As the other ones seem to be full of more questions about will this be a good driver for a tapped horn, can you model this design that I arbitrarily threw into this dimension.

It would be nice to just have a place to reference the details rather than sift through 1000+ posts

Cheers Boys!!

Antone-
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Old 26th November 2008, 01:18 AM   #2
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Really is this topic really a turkey???

Is no one wanting to actually compile more definitive information about critical tapped horn parameters?
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Old 26th November 2008, 11:34 AM   #3
MaVo is offline MaVo  Germany
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The problem i see with this is, that the only possible answer to the questions is, that it depends on the driver and the intended response - no specific answer is possible. A horn with little mouth to throat ratio may be a good solution in one case and sub-optimal in another case. Same goes for every system parameter. It all depends on what you have (ie. the driver) and what you want to achieve with it. You can make practically every woofer have a more or less acceptable response in at least one frequency range. But actually this is a good thing! You dont have to find the magic parameter set in horn and woofer, because everything will work if you choose a fitting set of parameters.
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Old 26th November 2008, 12:44 PM   #4
JLH is offline JLH  United States
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100% true MaVo. There are no magic ratios or set rules. It all depends on your application. Besides, an hour tooling around with McBean's Hornresp program is all you need. It's too easy to design a good tapped horn with Hornresp to waste time trying to make up rules that don't always apply.

Rgs, JLH
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Old 26th November 2008, 01:31 PM   #5
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I think for many DIYers the other approch would be interesting:
What driver and horn design do I chose to achieve a target response ?

I agree that you can do this with Hornresponse. But maybe some coarse rules could help to get rid of some iteration steps.

Regards

Charles
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Old 26th November 2008, 02:01 PM   #6
jbell is offline jbell  United States
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On that thinking, I'd earlier proposed to Don, to publish his 6 different TH's that's he's drawn up in cad, in a single thread. (maybe a sticky??) Those 6 span from PA to LFE HT subs, so maybe that would be a good starting point. And then, whenever someone comes up with a great addition that's proven out, add that to the list.

If someone would take a little time to add some commentary on the how's/why's of each driver/design, it could be a mini how-to for using hornresp, and help those just starting out. It might help someone choose an appropriate driver, of if they already have one, look and see if there is a published design that's a good starting point.

And for those who just want a set of plans, and go with a proven design... it's in one place.

That thread would need to be kept clean, no posts, just plans & documentation.
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Old 26th November 2008, 08:47 PM   #7
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I think there are some rules of thumb.

There is probably a relationship between Driver (Fs) and other Critical TS Parameters, and Desired TH. High Pass.

I'm sure by exploring successful TH designs, those relationships can be derived I expect that there are trends.

I'm pretty sure that there is a somewhat a optimal or Ideal percentage of path length longer than the Horns useful High pass 1/4 wave length.

I think a formula can be derived, that one could plug a target high pass knee, and get a rough Total path length.

I also think that a rough Expansion rate should be able to be found with some of the other TS parameters, and compression ratio.

To me an optimal model should, be shoot for, flattest response to high pass knee, SPL, and excursion control.

Those criteria, will steady the target a little. I think it should be easily scalable from those constraints.

Antone-
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Old 3rd December 2008, 10:27 AM   #8
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Antone,

I was interested to see your post, after slogging through about 55 pages of posts on the Collaborative tapped Horn Project last night with very little new info.

I seem to be following some of your (and Tom Danley’s) paths.

Around last January I started checking out the Collaborative tapped Horn Project, and decided to try converting my existing 65” path spiral horns using Lab 12s to a longer path length tapped horn.

The results were disappointing. After reading about your bass cabinets using 2x12” Labs, and after much experimentation, I ended up converting my boxes to dual Lab 12” ported cabinets.

The 2x12” put out more output in the 30-50 range than the 1x12” spiral horns, using 2/3rds the space, only 26.5” x 22.5” x22.5”, weighed the same (100 pounds) cabinets, can do about 130 dB with 2000 watts at one meter half space.

While in the process of that experiment, a friend called up, wanting to add subs to his Peavey system. He is a Peavey dealer, and had 4) low rider 15” that he wanted to use. Since he was using 4) 2x15” cabinets with 2” horns, I doubted that a pair of 2x15” ported cabinets with the Low Riders would keep up, and I suggested he build tapped horns for them.

I have never been a big fan of Peavey, but what the hell, here was a chance for me to get some testing done after someone else made the sawdust!

I designed him a 2x15” tapped horn truck integer cabinet, 32” x30” x 45”, horn path length around 105”, which according to the math should be about a 32 HZ tapped horn. He built a pair, and I went up to assist him in setting up his PA with the new subs out doors for a snowboard competition in Colorado.

Outdoors in the snow, we had little time to do a decent test, but from what I could determine, the 2x15”
at a 20 volt level (50 watts per cone) at one meter, mic on the ground plane, ranged from 116 to 123 dB SPL from 30 to 70 HZ, which averages out to a 99. 25 dB SPL at one meter reading.

The test used sine wave tones at 5 HZ intervals from 30 to 70 HZ. The peak to peak excursion went to 10 mm at 30 hz, only 2.5 at 35 HZ, 6 at 40, 7 at 45 and 50, 6 at 55, 5 at 60 and 1 at 70 HZ.

In Peavey’s literature on this sub, it shows a single Low Rider should do about 94 dB SPL in the range tested in the “Large 4.5 cubic foot cabinet”.

Adding 3 DB expected gain from having two cones to the ported cabinet should show 97 dB SPL .

The tapped horn would appear to be only 2.25 dB more efficient (sensitive?) using a 25 cubic foot cabinet compared to a 9 cubic foot ported cabinet. Not good at all in terms of real estate, unless the TH was way less distorted. Unfortunately I did not test that parameter and had never listened to the Low riders in ported cabinets, so I can’t offer any subjective difference, though I would say that the Low Riders seemed quite “clean” in the tapped horn from what I heard.

That said, the tapped horn subs seemed to “keep up” with 8) 15” above them, which would indicate subjectively that they may have been more quite a bit more efficient.

Bottom line, it would be very interesting to compare real world measured response of specific cones in “optimum” bass reflex cabinets compared to the same real world measurements using tapped horns of the same volume.

I finally have the SMAART program, and excellent test mics, so anyone in the Albuquerque/Santa Fe area that wants to do some real world “before and after” tests could be accommodated.

Without a ported vs tapped horn cabinet size consideration, which for the most part seems lacking in the Collaborative tapped Horn Project, it is hard to make valid comparisons.

Art
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Old 3rd December 2008, 07:27 PM   #9
FlipC is offline FlipC  United States
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weltersys
Like the beginning of this thread said. Not all drivers are good in TH's.
And did you design the enclosure with akAbak or HR?
I have a particular 15 that dosent work so
well in a TH but in a normal horn it bangs. (which I believe is due to the driver having a "loose" cone with allot of Xmax. IE it needs to rear to be enclosed for spring pressure.)

I think the big plus to THs is for small enclosures.
Not hard getting something 4-500 Lt to do good freq/spl #'s BUT to get something say less than 50 to do it is another story. I have an 8" design (Tang Band W8-740P) that is 47.5 Lt's that is 126 db 50-125 with -10 Db being 37 and 166 Hz. (a bit of EQ to get flat above 125 though on roughly 170 watts). I am looking for a different driver for this design. Something as cheap with a higher SPL. (as this one is 84db)
I have built 3 TH's so far.
The first was a test box for the 15 I referred to
in the part 1. The other 2 are single 12" in roughly 102 Lt box (box total is roughly 133). 130 Db 50-275 Hz. -10 is 40 Hz. I only run them to 200 Hz. That is on 430 ish watts. I have used these a few times and love them.

One thing I have found from looking at
other peoples designs are that there are 2 distinctions. Home Vs PA. Home (HT) wants a super flat response graph going down into the teens. Which is pretty simple to do given that the enclosure wont be being moved and also room response. Where as for PA you want SPL then flat response. I design for max SPL at 1 Pi / 2 Pi and not 1w@1m at .5 Pi . (yes those #s above are at 1 Pi)

You might want to look at ScreamUSA's design.
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Old 4th December 2008, 04:19 AM   #10
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Hi FlipC

I am using a Mac, and unfortunately there seems to be no modeling programs that work on the Mac platforms.

I like the fact that various modeling programs can prevent cutting up wood in vain, but there are many things that can only be learned by actually building and measuring the results.

The huge peaks and dips the modeling programs predict in the upper ranges of the TH that actually don’t happen in the real world are a case in point.

Being an empirical type of designer (:^), I like “rules of thumb”, to get in the ballpark before I butcher the wood, regardless of what a computer prediction says.

You said:

“there are 2 distinctions. Home Vs PA. Home (HT) wants a super flat response graph going down into the teens. Which is pretty simple to do given that the enclosure wont be being moved and also room response. Where as for PA you want SPL then flat response. I design for max SPL at 1 Pi / 2 Pi and not 1w@1m at .5 Pi . (yes those #s above are at 1 Pi)

I am not sure of what you mean by 1 Pi / 2 Pi and .5 Pi.

I prefer measurements and predictive programs in 1/2 space, as most of us locate our subs on the ground plane, while the distance to walls varies significantly.

Also, -10 dB SPL response sounds half as loud, while your ear hears progressively less in the low end. In the low frequency range, attention to the -3 dB low corner should be paid close attention in a TH cabinets.

Crap, I have not added anything worthwhile to Antone’s initial thread.
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