An externally hosted image should be here but it was not working when we last tested it.
Now its playing.
33 - 110 Hz with both quality and a decent spl. I did not think a small cheap driver like this could give this kind of bass!!! Impresive!
I had to feel with my fingers on the cone of the big tapped horn I have to know that it was not playing too.
Johannes.
Hi Guys,
I am also trying to build a tapped horn for PA use. The outer
dimension of the horn are close to the TH-115 of danleysoundlabs.
The driver i am using is a new one from Beyma, 15P1200ND, with
large Xmax and High FS, strong motor.
I included a few picks of the horn. This is my prototype. Saturday, if
weather permits, i am going to take measurements, impedance and freq. respons in open air with the programm Smaart. After these measurements are done i am going to remodel it and see if i can make a few changes that worth to try.
Making sawdust outdust with this weather outside +/- 2 degrees isn`t fun to do, hope it`s worth.
Cheers,
Marcel
I am also trying to build a tapped horn for PA use. The outer
dimension of the horn are close to the TH-115 of danleysoundlabs.
The driver i am using is a new one from Beyma, 15P1200ND, with
large Xmax and High FS, strong motor.
I included a few picks of the horn. This is my prototype. Saturday, if
weather permits, i am going to take measurements, impedance and freq. respons in open air with the programm Smaart. After these measurements are done i am going to remodel it and see if i can make a few changes that worth to try.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Making sawdust outdust with this weather outside +/- 2 degrees isn`t fun to do, hope it`s worth.
Cheers,
Marcel
Circlomanen said:
Hi Johannes,
I have carried out a “sanity check” on the example you quoted, and everything appears to be in order. I am very interested - what makes you think that the efficiency figure may be incorrect?
The attached screenprint shows the efficiency vs frequency chart for your tapped horn example (disregard references to acoustical impedance). You can see that the efficiency is relatively low across the frequency range of interest, while varying significantly across the full band - peaking at just under 45 percent. Any horn having a slow flare rate and relatively small mouth will exhibit such “peakiness”. The y-axis shows percentage. The “normalised acoustical resistance” at 35 hertz is actually the percentage efficiency (displayed as 1,0178 percent, which rounds to your calculated figure of 1,02 percent).
Kind regards,
David
//////////////////////////////////////////////
SANITY CHECK - VALUES USED
Velocity of sound = 344 metres per second
Density of air = 1,205 kilograms per cubic metre
Reference sound pressure = 2 * 10 ^ -5 newton per square metre (20 micropascals)
Ang = 0,5 x Pi (eighth space)
Eg = 8 volts
Sample results at 35 hertz
Sound pressure level = 111,0948 dB
Electrical input power = 19,1631 watts
Acoustical output power = 0,1950 watts
System efficiency = 1,02 percent
Driver electrical input impedance magnitude = 3,3390 ohms
ELECTRICAL INPUT POWER
If we assume that the driver electrical input impedance is purely resistive at 35 hertz (it is very close)
Electrical input power = Eg ^ 2 / Impedance watts
Electrical input power = 8 ^ 2 / 3,339 watts
Electrical input power = 19,1674 watts
This is almost the same as the Sample result of 19,1631 watts. The slight discrepancy is due to the actual input impedance having a small reactive component at 35 hertz in addition to a dominant resistive component.
ACOUSTICAL OUTPUT POWER
If we assume that the sampled acoustical output power is correct then
Acoustical output power = 0,1950 watts
1 / 8 surface area of 1 metre radius sphere = (4 * Pi * Radius ^ 2) / 8 square metres
1 / 8 surface area of 1 metre radius sphere = 0,5 * Pi square metres
Sound intensity at surface of 1 / 8 sphere = Power / Area watts per square metre
Sound intensity at surface of 1 / 8 sphere = 0,1950 / (0,5 * Pi) watts per square metre
Pressure at surface of 1 / 8 sphere = (Intensity * Velocity * Density) ^ 0,5 newtons per square metre
Pressure at surface of 1 / 8 sphere = (0,1950 / (0,5 * Pi) * 344 * 1,205) ^ 0,5 newtons per square metre
Pressure at surface of 1 / 8 sphere = 7,1735 newtons per square metre
SPL = 20 * Log10(Pressure / Reference pressure) dB
SPL = 20 * Log10(7,1735 / 0.00002) dB
SPL = 111,0940 dB
This is almost the same as the Sample result of 111,0948 dB watts. The results would be identical if the figures used in the above calculations were not rounded to four decimal places.
SYSTEM EFFICIENCY
System efficiency = Acoustical output power / Electrical input power x 100 percent
System efficiency = 0,1950 / 19,1631 x 100 percent
System efficiency = 1,02 percent
This is identical to the Sample result of 1,02 percent.
//////////////////////////////////////////////
Attachments
Thank you very much for checking.
I just dont seem to get that spl when playing on my horns in my home.
My large tapped horn with a Beyma 12LX60 doesnt do 102 dB with one watt. I havent measured, but its not 10 dB more efficient than my BR-box with two 10 inch drivers in. (88 dB/w/m) I have to adjust the sensitivitysetting on my amp about 8 dB. That would make it about 96 dB/w/m efficient.
An externally hosted image should be here but it was not working when we last tested it.
Johannes.
G'day Circlomanen
There is a very good chance that your 12LX60 Tapped Horn has 102dB/W/M sensitivity - when 1/4 space loaded. On the same note, I'd guess your dual 10" BR box is doing better than 88dB/W/M when also 1/4 space loaded.
Interestingly enough, a domestic room is a really poor representation of 1/4 space (or 1/8th space if in a corner) loading. The room is much more constrained that 1/8th space would predict, but then the walls are much more lossy too. You get what you get and you basically have to live with that.
Cheers
William Cowan
There is a very good chance that your 12LX60 Tapped Horn has 102dB/W/M sensitivity - when 1/4 space loaded. On the same note, I'd guess your dual 10" BR box is doing better than 88dB/W/M when also 1/4 space loaded.
Interestingly enough, a domestic room is a really poor representation of 1/4 space (or 1/8th space if in a corner) loading. The room is much more constrained that 1/8th space would predict, but then the walls are much more lossy too. You get what you get and you basically have to live with that.
Cheers
William Cowan
Isn't 88dB/W the nominal sensitivity rating of the 10" drivers?
Consider that you have two drivers together, which gives an extra 3dB/W at LF, and that the floor and one wall are probably quite close to them so they are likely to be radiating into 1/4 space at LF (rather than 1/2) giving another extra 3dB.
I don't know how rooms with light walls behave, but the rooms with heavy concrete walls that we still have here in most buildings help a lot with bass and direct radiators. The same speakers sound like pocket radios when placed outdoors.
Consider that you have two drivers together, which gives an extra 3dB/W at LF, and that the floor and one wall are probably quite close to them so they are likely to be radiating into 1/4 space at LF (rather than 1/2) giving another extra 3dB.
I don't know how rooms with light walls behave, but the rooms with heavy concrete walls that we still have here in most buildings help a lot with bass and direct radiators. The same speakers sound like pocket radios when placed outdoors.
Circlomanen said:
Hi Johannes,
Thanks for the additional information. I have no explanation for the difference in levels you are seeing - assuming that the input to the loudspeaker is actually 1 watt and not 2,83 volts (1 watt into a nominal 8 ohms).
User feedback would suggest that Hornresp SPL predictions at bass frequencies can be surprisingly close to measured results, provided that the test conditions accurately reflect assumptions made in the simulation model.
The comments by GM, William and Eva are relevant.
It's a minor point I know, but technically I think that we are now probably talking about sensitivity, rather than efficiency
.Kind regards,
David
Maybe it's because of all the bends, you have 2 that is 180 degrees
and three that are 90 degrees where the moving air has to change
direction.
Your big TH only has one 180 degrees bend.
I don't know how much that effect the sensitivity, but I think it is worth
mentioning.
Does Hornresp assume the horn is totally straight?
/Petter
and three that are 90 degrees where the moving air has to change
direction.
Your big TH only has one 180 degrees bend.
I don't know how much that effect the sensitivity, but I think it is worth
mentioning.
Does Hornresp assume the horn is totally straight?
/Petter
I have a question, related to tapped horns...
In the course of building his Thor sub, Linkwitz stated: "I did not consider alternate approaches to subwoofer design as acceptable for meeting my goal of accurate sub-bass reproduction. This includes vented, passive radiator and acoustic bandpass woofers. They all rely on resonant energy storage to increase efficiency and to reduce size."
I dont have the background knowledge to confirm this or not, i have to believe in such quotes. I imagine this energy storage just like a string instrument, where one stores energy in the string by plucking it. Then its releasing energy over time, thus creating a pitched noise with the frequency of the string resonance frequency plus harmonics.
My question is: How does this concept of resonant energy storage apply to tapped horns or horns in general?
A second, maybe too general question may be: From which point on does this affect the quality of reproduction? If i imagine maximum resonance and no damping, it would be self oscillation, something filters in synthesizers can do sometimes.
In the course of building his Thor sub, Linkwitz stated: "I did not consider alternate approaches to subwoofer design as acceptable for meeting my goal of accurate sub-bass reproduction. This includes vented, passive radiator and acoustic bandpass woofers. They all rely on resonant energy storage to increase efficiency and to reduce size."
I dont have the background knowledge to confirm this or not, i have to believe in such quotes. I imagine this energy storage just like a string instrument, where one stores energy in the string by plucking it. Then its releasing energy over time, thus creating a pitched noise with the frequency of the string resonance frequency plus harmonics.
My question is: How does this concept of resonant energy storage apply to tapped horns or horns in general?
A second, maybe too general question may be: From which point on does this affect the quality of reproduction? If i imagine maximum resonance and no damping, it would be self oscillation, something filters in synthesizers can do sometimes.
some thoughts on my last post...
(i use concepts here, which i dont understand in depth, so please correct me if i am wrong, since i want to understand a little more)
A perfect horn should be non resonant, as it only matches the radiation resistance of the driver to that of the air.
A compromised (too small mouth) horn doesnt match those two good enough, there are reflections from the mouth back into the horn. In this way, a non perfect horn will also have resonances.
Now, Is a tapped horn a perfect horn in this aspect, at least for its two octave bandwidth?
That behaviour should be measurable in the time domain. Think of a single cylce of a sine wave, with a frequency in the passband of the horn, fed into it. The output should be more than one cycle in a resonant system.
(i use concepts here, which i dont understand in depth, so please correct me if i am wrong, since i want to understand a little more)
A perfect horn should be non resonant, as it only matches the radiation resistance of the driver to that of the air.
A compromised (too small mouth) horn doesnt match those two good enough, there are reflections from the mouth back into the horn. In this way, a non perfect horn will also have resonances.
Now, Is a tapped horn a perfect horn in this aspect, at least for its two octave bandwidth?
That behaviour should be measurable in the time domain. Think of a single cylce of a sine wave, with a frequency in the passband of the horn, fed into it. The output should be more than one cycle in a resonant system.
Circlomanen said:
OK, my $125 question is `What happens if one then takes a nice tapped horn like Circlomanen has made here and extends the single output port in the fashion of a full sized conical or exponential horn for the frequency at hand.`?
One could make some size compromises like output horn length = 1/4 lambda at lowest frequency and mouth smaller to work into 1/4 or 1/8th space in a living room environment.
An externally hosted image should be here but it was not working when we last tested it.
Not nice. I extended the last part with 3 meters and the mouth to 1,44 squaremeters.
Much better to build a regular horn from the beginning.
Johannes.
Failed at modeling in AkaBak
I need help. I've read this thread at least a couple of times and I have tried using AkaBak, but I don't have a clue as to what I am doing. All I want to do is share in the joy that everyone is experiencing with their tapped horns. Can someone tell me if this sub is good for a tapped horn? It's specs close to the MTX 9515-4 driver that Cowan recommended except that the Fs = 25hz. Here are the driver specs:
"T/S from a production sample broken-in for 3-4 hours at 50% excursion. Measurements are with VC in parallel.
XJ-15 Parameters:
Re: 3.95 ohm
Qts: 0.578
Qes: 0.673
Qms: 4.095
Fs: 24.5hz
mms: 130g
cms: .300mm/N
BL: 11
Vas: 284L
Pmax: Lets say 600W which is conservative. If you thermally fry the thing your doing something very stupid."
My only other recourse is to do the trial and error method until I get something that sounds good and that get's expensive.
I need help. I've read this thread at least a couple of times and I have tried using AkaBak, but I don't have a clue as to what I am doing. All I want to do is share in the joy that everyone is experiencing with their tapped horns. Can someone tell me if this sub is good for a tapped horn? It's specs close to the MTX 9515-4 driver that Cowan recommended except that the Fs = 25hz. Here are the driver specs:
"T/S from a production sample broken-in for 3-4 hours at 50% excursion. Measurements are with VC in parallel.
XJ-15 Parameters:
Re: 3.95 ohm
Qts: 0.578
Qes: 0.673
Qms: 4.095
Fs: 24.5hz
mms: 130g
cms: .300mm/N
BL: 11
Vas: 284L
Pmax: Lets say 600W which is conservative. If you thermally fry the thing your doing something very stupid."
My only other recourse is to do the trial and error method until I get something that sounds good and that get's expensive.
Peerless 830515
I have a question for Cowan about the Peerless 830515--is this driver good for a tapped horn? Perhaps a tapped horn that is tuned lower than the 30hz tapped horn on your website? This driver appears to be on sale and if my other driver (in my earlier post) doesn't pan out then maybe I can use this one.
I have a question for Cowan about the Peerless 830515--is this driver good for a tapped horn? Perhaps a tapped horn that is tuned lower than the 30hz tapped horn on your website? This driver appears to be on sale and if my other driver (in my earlier post) doesn't pan out then maybe I can use this one.