i recently put 2 subwoofers in a tapped horn, i then tried the same drivers in separate ported boxes. using the exact same amp and equipment the tapped horn was much louder.both ported boxes and tapped horns use both sides of the cone (i think) so why was the t.h. so much louder? 6db ive heard but why?
Hi 60ndown,
Maybe Tom Danley's white paper would be helpful: http://www.danleysoundlabs.com/pdf/danley_tapped.pdf
Regards,
Maybe Tom Danley's white paper would be helpful: http://www.danleysoundlabs.com/pdf/danley_tapped.pdf
Regards,
your right 
although these 2 statements seem to conflict?
To illustrate just how much low frequency extension and overall output can be gained from a small horn loaded box using this technique, modeled simulations of a Tapped Horn and a vented box, loaded with drivers optimized for the performance of each one, are compared in Figure 1. Each enclosure has the same outer cabinet dimensions; 40 in. x 22.5 in x 28 in.
While the SPL is comparable for the two units, one of the real advantages of the Tapped Horn is seen in Figure . The diaphragm excursion of the driver is greatly reduced due to the acoustical loading of the horn. With an input of 63 V (500 W) the vented box exceeds 5 mm (0.2 inches) at 90 Hz. The Tapped Horn is well below this until just above 55 Hz. The vented box reaches 9 mm at 55 & 35 Hz while the Tapped Horn’s excursion peaks at just over 6 mm at 46Hz. This decrease in excursion will translate directly into lower distortion and higher output capability from the Tapped Horn.
although these 2 statements seem to conflict?
To illustrate just how much low frequency extension and overall output can be gained from a small horn loaded box using this technique, modeled simulations of a Tapped Horn and a vented box, loaded with drivers optimized for the performance of each one, are compared in Figure 1. Each enclosure has the same outer cabinet dimensions; 40 in. x 22.5 in x 28 in.
While the SPL is comparable for the two units, one of the real advantages of the Tapped Horn is seen in Figure . The diaphragm excursion of the driver is greatly reduced due to the acoustical loading of the horn. With an input of 63 V (500 W) the vented box exceeds 5 mm (0.2 inches) at 90 Hz. The Tapped Horn is well below this until just above 55 Hz. The vented box reaches 9 mm at 55 & 35 Hz while the Tapped Horn’s excursion peaks at just over 6 mm at 46Hz. This decrease in excursion will translate directly into lower distortion and higher output capability from the Tapped Horn.
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your right
although these 2 statements seem to conflict?
To illustrate just how much low frequency extension and overall output can be gained from a small horn loaded box using this technique, modeled simulations of a Tapped Horn and a vented box, loaded with drivers optimized for the performance of each one, are compared in Figure 1. Each enclosure has the same outer cabinet dimensions; 40 in. x 22.5 in x 28 in.
While the SPL is comparable for the two units, one of the real advantages of the Tapped Horn is seen in Figure . The diaphragm excursion of the driver is greatly reduced due to the acoustical loading of the horn. With an input of 63 V (500 W) the vented box exceeds 5 mm (0.2 inches) at 90 Hz. The Tapped Horn is well below this until just above 55 Hz. The vented box reaches 9 mm at 55 & 35 Hz while the Tapped Horn’s excursion peaks at just over 6 mm at 46Hz. This decrease in excursion will translate directly into lower distortion and higher output capability from the Tapped Horn.
Can't see your figure (did you attach it?). When I did the same comparison years ago when Tom first announced the tapped horn, my conclusion was that you could get the same efficiency and maximum output with a tapped horn or a reflex the same size -- but the tapped horn typically needs 1 heavy-cone high-power driver (lots around nowadays), the reflex needs 2 lighter-cone lower-power drivers the same size (not so easy to find -- the B&C 18PS76 was the best choice, but it's now obsolete). Even total weight and cost ended up similar (2 cheap drivers in a simple box vs. 1 expensive driver in a complex box).
So if you can get truly optimum drivers there's no difference, but many drivers nowadays are better suited to tapped horns (or horns) than reflex, they haven't really got enough Xmax to deal with their high power ratings without a horn to reduce cone travel.
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your right
although these 2 statements seem to conflict?
To illustrate just how much low frequency extension and overall output can be gained from a small horn loaded box using this technique, modeled simulations of a Tapped Horn and a vented box, loaded with drivers optimized for the performance of each one, are compared in Figure 1. Each enclosure has the same outer cabinet dimensions; 40 in. x 22.5 in x 28 in.
While the SPL is comparable for the two units, one of the real advantages of the Tapped Horn is seen in Figure . The diaphragm excursion of the driver is greatly reduced due to the acoustical loading of the horn. With an input of 63 V (500 W) the vented box exceeds 5 mm (0.2 inches) at 90 Hz. The Tapped Horn is well below this until just above 55 Hz. The vented box reaches 9 mm at 55 & 35 Hz while the Tapped Horn’s excursion peaks at just over 6 mm at 46Hz. This decrease in excursion will translate directly into lower distortion and higher output capability from the Tapped Horn.
He's talking about sensitivity vs maximum SPL
When I think about THs, I always see in my mind those 19th century engravings sent to the patent office about the most amazing new inventions that double the force of your plow horse, pluck corn grains off cobs, allow people who are diabetic to sew buttons on their pants, or otherwise solve the problems of humankind in profoundly simple ways.
Ben
Ben
In a basreflex one side of the cone is loading 'full' space, the other half is loading a closed box with a bas reflex pipe. Since basreflex (straight) pipes have narrow Q (small band) it only operates in a very small area of the frequency range. Also these pipes are normally tuned the lowest octave possible of the system where efficiency is the lowest already. In other words the basreflex doesn’t add extra gain to the rest of the efficiency and it only 'amplifies' the part where the efficiency already is dropped.
In a TH both sides of the cone load (drive) a tapped horn/pipe. The advantage is that tapped ends are wide band efficient. Although a TH has more in common with 6th order bandpass it the tapped end(s) that makes the difference. While Bandpass system has normally straight pipes the TH uses tapped pipes. Again, straight pipes have narrow Q’s (small bandwidth), tapped 'pipes' have wide Q (wide bandwidth).
The extra efficiency from TH’s comes from the dual type of loading. Both sides of the cone load (drive) a 1/4WL tapped horn/pipe. Therefore the excursion becomes 2 times more effective. So actually if you want to compare a basreflex to a TH you have to use two drivers in a basreflex to get the same amount of loading into 'full' space. The maximum gain from a TH is 3dB gain over a basreflex system. If you double the drivers (2 drivers per box) it becomes 6dB. Another doubling (4 drivers per system) can raise the max output to max. 9dB.
The most genius part of the TH is that both cones sides see a tapped end but in reality these two tapped ends are physically the same tapped horn. This makes the TH in my opinion so interesting for PA use. If you would design a traditional horn from the same dimensions as the TH, you will see lower efficiency below 1/2WL because:
In a TH both sides of the cone load (drive) a tapped horn/pipe. The advantage is that tapped ends are wide band efficient. Although a TH has more in common with 6th order bandpass it the tapped end(s) that makes the difference. While Bandpass system has normally straight pipes the TH uses tapped pipes. Again, straight pipes have narrow Q’s (small bandwidth), tapped 'pipes' have wide Q (wide bandwidth).
The extra efficiency from TH’s comes from the dual type of loading. Both sides of the cone load (drive) a 1/4WL tapped horn/pipe. Therefore the excursion becomes 2 times more effective. So actually if you want to compare a basreflex to a TH you have to use two drivers in a basreflex to get the same amount of loading into 'full' space. The maximum gain from a TH is 3dB gain over a basreflex system. If you double the drivers (2 drivers per box) it becomes 6dB. Another doubling (4 drivers per system) can raise the max output to max. 9dB.
The most genius part of the TH is that both cones sides see a tapped end but in reality these two tapped ends are physically the same tapped horn. This makes the TH in my opinion so interesting for PA use. If you would design a traditional horn from the same dimensions as the TH, you will see lower efficiency below 1/2WL because:
- The smaller than optimal horn mouth size
- One side of the cone is radiating into a compression box.
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Interesting, I understand for roughing out what a TH will do--at a minimum is +6 dB over the efficiency rating of the driver. I'm wondering about the compression ratio's effect on efficiency, 3:1 or 5:1 or... JBells monster 8:1 with the MCM 8" subwoofers.
If two subwoofers in a ported box can produce the same output and size as a single subwoofer in a tapped horn--why build it?
From what I gather, the higher the compression--the more efficiency so a 3:1 compression TH would easily be more than 3dB efficient over a ported box. As always, I will cut up some wood to try it out--trying 3:1 on a 10" sub tuned just below Fs to get the efficiency up. Time to get my Horn Response programming down to really get my understanding before I add yet another ugly box to my arsenal.
Back to Horn Response...
Two things, I didn't state same size for two drivers in a basreflex. The size will be doubled of course for the basreflex cab with 2 drivers. Another advantage of the TH I didn't mention is its directional pattern. While a basreflex radiates omni directional (all energy is radiated 360 degrees around the basreflex box) the TH radiates its energy into a directional pattern (most energy is radiated to the front of the cab where the audience is). This where the 'extra' dB's come from in some (+) 10meter measurements.
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Djim,
Thank you for clearing that up, my TH build is to get as many extra dBs as possible, sound decent doing it, learn something new and "because it's there".
Directional is not a problem, more of a good thing in it's "semi-PA" final usage. It will be loaded in a corner so as long as it's close to even from 90 degrees--all is well. Still wrapping my head around the program and the compression ratio/high pressure/low pressure sides but I'm getting there. Eventually I'll have that "but of course" moment were the sun shines, the bird sings and my wife cringes (how much is it going to cost THIS time?")
Thank you for clearing that up, my TH build is to get as many extra dBs as possible, sound decent doing it, learn something new and "because it's there".
Directional is not a problem, more of a good thing in it's "semi-PA" final usage. It will be loaded in a corner so as long as it's close to even from 90 degrees--all is well. Still wrapping my head around the program and the compression ratio/high pressure/low pressure sides but I'm getting there. Eventually I'll have that "but of course" moment were the sun shines, the bird sings and my wife cringes (how much is it going to cost THIS time?")
I didn't notice Djim explaining that this wave-fraction magic happens only where the wave-fractions add.... and the TH acts rather differently where they subtract.
With a resonant box, you suck-out the system resonance with an anti-resonance and thus have left two residual resonance bumps. It all happens down in the feel-good bass region so nobody is too picky about the specific notes that get boosted or tossed out. Some people think that is wonderful. Kind of similar net results with TH.
Of course, a sealed AR-3 played certain music especially nice too. So in some ways, all speakers are judged in relation to the music you choose to demo them on.
Ben
With a resonant box, you suck-out the system resonance with an anti-resonance and thus have left two residual resonance bumps. It all happens down in the feel-good bass region so nobody is too picky about the specific notes that get boosted or tossed out. Some people think that is wonderful. Kind of similar net results with TH.
Of course, a sealed AR-3 played certain music especially nice too. So in some ways, all speakers are judged in relation to the music you choose to demo them on.
Ben
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I like the simplicity of the vented box. B&C 18PS100 in 7.5 cu ft box tuned to 30Hz. The chart shows 300watts input. The output of 120dB down to almost 40Hz seems more than adequate to me. I read here:
The Subwoofer DIY page v1.1 - How low should a subwoofer go?
that having a subwoofer with a -3dB of less than 30Hz can lead to problems due to room gain. This one has a -3dB of 32Hz.
The Subwoofer DIY page v1.1 - How low should a subwoofer go?
that having a subwoofer with a -3dB of less than 30Hz can lead to problems due to room gain. This one has a -3dB of 32Hz.
Attachments
The radiation pattern from a tapped horn is no different to any other box where the sound exits from the same area -- there's no "magic" which makes it any more or less directional, especially at bass frequencies, the atmosphere has got no way of knowing what's inside the box.
A big array of tapped horns will be directional (as Tom has demonstrated), especially if the flat faces of the boxes form a radiation boundary -- but so will a big array of reflex boxes the same size with the same frontal area.
In answer to the question about compression ratio, it all depends on the driver and the horn -- heavy-coned drivers (actually it's mass density that matters i.e. g/cm2) tend to need higher CR to get the best efficiency and response flatness because higher CR increases the air load on the cone to get better radiation impedance matching.
For some drivers the optimum CR may be 5:1 or even higher, which may lead to cone failure problems and also high air velocities in the throat causing chuffing (like a too-small reflex port) -- especially because heavy drivers tend to have long coils with big Xmax so can push more air in the first place.
Obviously, they cancel each other out, which I assume is the reason for the extremely jagged spl response at higher frequencies. You'd need a 24dB/octave filter to shut that junk off, in my opinion.
A tapped horn gives high efficiency and maximum SPL over a limited bandwidth, usually not much more than 3:1 range. Above this the response is ragged (though not usually as bad as simulations predict) and a fast-cutoff crossover is definitely needed to reduce the effect of this.
Since high-power subs are normally used with active crossovers (often digital ones) this isn't a problem, 24dB/oct or even 48dB/oct Linkwitz-Riley are usually available. Forget about passive crossovers, you can't build a high-order high-power low-loss one with any available inductors, and the load impedance is nothing like resistive either.
Hi iand,
Post #19: "...Forget about passive crossovers..."
It may be of interest to mention, that in a tapped horn a series inductor can sometimes be of help to flatten the passband response (in Hornresp: add the resistive component to Rg and the inductance to Le). This also touches on one of the problems in software simulations, the inductance in the passband has to be known for the simulation to be accurate; e.g.: The Selenium 18SWS800 is one of the few drivers that provides more than the typical voice coil inductance @ 1kHz value (from the data sheet: Le @ FS 7.983 mH - Le @ 1kHz 3.872 mH - Le @ 20kHz 2.064 mH). epa came up with a rule of thumb to double the 1kHz value for use in Hornresp for subs.
Regards,
Post #19: "...Forget about passive crossovers..."
It may be of interest to mention, that in a tapped horn a series inductor can sometimes be of help to flatten the passband response (in Hornresp: add the resistive component to Rg and the inductance to Le). This also touches on one of the problems in software simulations, the inductance in the passband has to be known for the simulation to be accurate; e.g.: The Selenium 18SWS800 is one of the few drivers that provides more than the typical voice coil inductance @ 1kHz value (from the data sheet: Le @ FS 7.983 mH - Le @ 1kHz 3.872 mH - Le @ 20kHz 2.064 mH). epa came up with a rule of thumb to double the 1kHz value for use in Hornresp for subs.
Regards,
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