also
if one would be to use line array of almost 8' tall drivers right in front or near front side of the mouth of this horn,
would the sound + delay affect the movement/waves of the woofer/tweeters working in front of the exit ?
what if this line array would be of an OB type?
( lets say dipole flat baffle for the sake of the example)
i'd think that a horn with that size and powerfull output could make the small woofers move ??
if one would be to use line array of almost 8' tall drivers right in front or near front side of the mouth of this horn,
would the sound + delay affect the movement/waves of the woofer/tweeters working in front of the exit ?
what if this line array would be of an OB type?
( lets say dipole flat baffle for the sake of the example)
i'd think that a horn with that size and powerfull output could make the small woofers move ??
JinMTVT said:
Yes a corner is regarded as 1/8th space (0.5pi)JinMTVT said:
Consider the delay first. The delay can be calculated.But remember you have TWO sources,this makes it more complicated. The likelyhood is that the delay is inaudible if you crossover low enough.
Often people assume this...
The small woofers your midranges have DAMPING(both electrical Qes and physical Qms) so the basshorn shouldnt destroy them.
Patrick Bateman could discuss this further.
I think for you the decision is to choose cutoff/volume,and then use the right woofer.Using a larger woofer gives a shorter horn for the same cutoff,a 12" might not be suitable.The shiva does have good middle of the road specs though.
delay ...
isn't it going to play with the phase relation of all the drivers?
i also still don't undestand how the front and the rear of the driver will play together with phase VS frequency..
i know we are considering this for low freq..but still
i've played with HornResp quite a bit today ..
tried to get decent output from a 18 and 21"
( 6174 and DP2152 something .. )
was fun ..but hard to understand at first
i don't see much difference even going with wild horn sizes ...
isn't it going to play with the phase relation of all the drivers?
i also still don't undestand how the front and the rear of the driver will play together with phase VS frequency..
i know we are considering this for low freq..but still
i've played with HornResp quite a bit today ..
tried to get decent output from a 18 and 21"
( 6174 and DP2152 something .. )
was fun ..but hard to understand at first
i don't see much difference even going with wild horn sizes ...
If you can see that a front loaded,rear sealed horn will have a delay relative to the horn length.Thats simple. It become more complex when you have two sources,in phase,sometimes. Thats what the software is for,to graphically present it. Perhaps when modeling you should start with some one elses design as listed,and adjust it. Post some small screenshots here of your progress.JinMTVT said:
A question for those who have actually built AND simulated a tapped horn in hornresponse:
Is there a large differenc between the simulated and the actually measured response ?
I ask because the program only allows calculations for conical taper while the practical implementations all use parabolic taper sections.
Regards
Charles
Is there a large differenc between the simulated and the actually measured response ?
I ask because the program only allows calculations for conical taper while the practical implementations all use parabolic taper sections.
Regards
Charles
Designs like post #410 and #509 are definitely not conical but consist of parabolic sections due to the definition of parabolic and conical horns:
Parabolic horn: The cross-section expands proportionally with with distance from throat.
Conical horn: The cross-section expands proportionally to the square of the distance from throat.
Maybe the first one is called a conical horn nowadys just like the sloppy language that is used in many other places today (like bandwidth instead of bit-rate in data-communications).
Regards
Charles
Parabolic horn: The cross-section expands proportionally with with distance from throat.
Conical horn: The cross-section expands proportionally to the square of the distance from throat.
Maybe the first one is called a conical horn nowadys just like the sloppy language that is used in many other places today (like bandwidth instead of bit-rate in data-communications).
Regards
Charles
phase_accurate said:
Hi Charles,
While I can't comment on predicted versus measured results, I think that it would be fair to say that the flare rates used in bass tapped horns are usually so low that there is unlikely to be any appreciable difference in the theoretical results for a conical profile compared to a parabolic profile.
As an experiment, for a given tapped horn design in Hornresp, try swapping the three segments from Conical to Exponential and see how much the results change. This should give you some idea as to the sensistivity of the design to flare profile changes, even though in this case we are using an exponential rather than a parabolic flare for the comparison.
Kind regards,
David
David McBean said:
It just get's back to Hoffman's Iron Law - no matter what kind of enclosure you are using, you're not going to get a dramatic increase in SPL without a dramatic increase in box size.
Of course, the tapped horn is very clever, because it almost "cheats" Hoffman's Iron law, by leveraging a great deal of the REAR wave from the woofer. If it was 100% perfect, you'd see a 6db increase in SPL across the entire frequency range. Naturally, this is impossible.
i am still in the clouds when it comes to understanding this device ...no one as pointed out exactly the benefits of the tapped horn
( i can understand easily that we are using both rear and front waves ..so this increases the efficiency )
how exaclty does the front wave behave in this case?
does it get works out by the remaining part of the mouth/horn up to the output
or does it also goes in the horn up to the back of the driver and back up ?
in wich case i assume it may interact with the rear wave...
( i can understand easily that we are using both rear and front waves ..so this increases the efficiency )
how exaclty does the front wave behave in this case?
does it get works out by the remaining part of the mouth/horn up to the output
or does it also goes in the horn up to the back of the driver and back up ?
in wich case i assume it may interact with the rear wave...
Sabbelbacke said:@David
I just recognized a new hornresp version. GreatWhat´s new this time?
Hi Sabbelbacke,
In Version 16.30, 'Copy Driver' and 'Paste Driver' commands have been added under the 'File' menu to make it easier to change the driver on an existing design. Just select the master record for the driver you want, click the File > Copy Driver menu command to copy the driver parameter values, move to the record you wish to change, click on the Edit button and then click the File > Paste Driver menu command to replace the current driver parameter values with the ones taken from the master record. The value of Nd does not change.
In my own case, I save master driver records using a standard format. Comments are prefixed by "#" so that after the Hornresp.dat data file has been sorted and the Find tool is used, all driver records are grouped together in a "driver library" just under the default record 001. "#" can also be used as a Find tool search parameter to display only the driver records if desired. I use the following standard comment format for master driver records: "# Driver manufacturer and model number : Xmax = value mm : Pmax = value W".
Kind regards,
David
For reference, please go here:
http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=64542&highlight=olson+djk&r=&session=
And then load both gif on different pages.
Now open another page and load this gif:
http://www.prosoundshootout.com/Measurements/Tuba24_28v.gif
What are we looking at?
Fig.5.10 (100hz horn with different mouth sizes)
Fig. 5.11 (100hz horn with different throat sizes)
Tuba 24
Figure 5.10 shows what happens when we have a 100hz flare and change the mouth size. Look close at A and E. A is too small of a mouth, E is an infinitely large mouth. Of acedemic interest, with an infinite mouth we have no output at cut-off. Strangely, the too-small mouth has quite a bit of output near cut-off. See how the dotted curve dips negative about a half-octave above cut-off on A? Look at the Tuba 24, see the dip at about 60hz? Guess why it's there.
Figure 5.11 shows what happens as you shorten the horn by using a bigger driver. Note that 5.10B and 5.11A are the same.
Paging horns are sized like 5.10B and 5.11A, this seems to give about 10dB in variation in the bottom octave, 5.10C looks like about 6dB. You can run this through HornResponse if you want to put real numbers on it, all we are concerned about is relativity at this point.
For a bass horn it looks like we would need something like 5.10C or 5.10D, 5.11C shows a large driver/throat on a 1/4W horn with the mouth the same size as 5.10B
Now we can see why too short of a horn, or too small of a mouth is a problem. Before HornResponse these figures are what we looked at.
We might be able to live with a large throat 5.10C scaled up to 25hz. That would be about 120" in diameter, about 10 foot! With a large throat like 5.11C we could make it 1/4W long (11.3 foot), and end up with it reasonably flat to about 40hz. Theory says we could make it a half-moon shape with the ground making a mirror-image (restoring the full-moon shape). That's still about 40 square feet of mouth (think in terms of multiple LAB 12s stacked).
Back to looking at 5.10B and where the solid curve dips down, and the dotted curve goes negative. We see that this gives the big dip as in the Tuba 24 curve.
What if we could fill in this hole somehow?
The driver position down the throat a bit seems to help this out. The driver ouput radiates on both sides in this dip area. It also causes the suck-out about two octaves above cut-off as seen here:
http://diy.cowanaudio.com/images/Test10to13.gif
Here is an example of what can be done with a tapped horn. This is four cabinets, each with a single 15" driver. Each cabinet has a mouth only about 20" square. The jpg I have stored is from AkAbak, but HornResponse should give similar results:
http://i56.photobucket.com/albums/g196/dkleitsch/3015LFX4.jpg
Note that it is about 3dB down at 40hz, with the typical dip two octaves above (about 160hz). This is modeled in 2Pi with a 4' high by 6' wide wall (inherent in the fronts of the four stacked cabinets). While 112dB/W is shown, it will probably be a bit lower in actual use as no wall or cabinet is a perfect reflector at very low frequencies.
http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=64542&highlight=olson+djk&r=&session=
And then load both gif on different pages.
Now open another page and load this gif:
http://www.prosoundshootout.com/Measurements/Tuba24_28v.gif
What are we looking at?
Fig.5.10 (100hz horn with different mouth sizes)
Fig. 5.11 (100hz horn with different throat sizes)
Tuba 24
Figure 5.10 shows what happens when we have a 100hz flare and change the mouth size. Look close at A and E. A is too small of a mouth, E is an infinitely large mouth. Of acedemic interest, with an infinite mouth we have no output at cut-off. Strangely, the too-small mouth has quite a bit of output near cut-off. See how the dotted curve dips negative about a half-octave above cut-off on A? Look at the Tuba 24, see the dip at about 60hz? Guess why it's there.
Figure 5.11 shows what happens as you shorten the horn by using a bigger driver. Note that 5.10B and 5.11A are the same.
Paging horns are sized like 5.10B and 5.11A, this seems to give about 10dB in variation in the bottom octave, 5.10C looks like about 6dB. You can run this through HornResponse if you want to put real numbers on it, all we are concerned about is relativity at this point.
For a bass horn it looks like we would need something like 5.10C or 5.10D, 5.11C shows a large driver/throat on a 1/4W horn with the mouth the same size as 5.10B
Now we can see why too short of a horn, or too small of a mouth is a problem. Before HornResponse these figures are what we looked at.
We might be able to live with a large throat 5.10C scaled up to 25hz. That would be about 120" in diameter, about 10 foot! With a large throat like 5.11C we could make it 1/4W long (11.3 foot), and end up with it reasonably flat to about 40hz. Theory says we could make it a half-moon shape with the ground making a mirror-image (restoring the full-moon shape). That's still about 40 square feet of mouth (think in terms of multiple LAB 12s stacked).
Back to looking at 5.10B and where the solid curve dips down, and the dotted curve goes negative. We see that this gives the big dip as in the Tuba 24 curve.
What if we could fill in this hole somehow?
The driver position down the throat a bit seems to help this out. The driver ouput radiates on both sides in this dip area. It also causes the suck-out about two octaves above cut-off as seen here:
http://diy.cowanaudio.com/images/Test10to13.gif
Here is an example of what can be done with a tapped horn. This is four cabinets, each with a single 15" driver. Each cabinet has a mouth only about 20" square. The jpg I have stored is from AkAbak, but HornResponse should give similar results:
http://i56.photobucket.com/albums/g196/dkleitsch/3015LFX4.jpg
Note that it is about 3dB down at 40hz, with the typical dip two octaves above (about 160hz). This is modeled in 2Pi with a 4' high by 6' wide wall (inherent in the fronts of the four stacked cabinets). While 112dB/W is shown, it will probably be a bit lower in actual use as no wall or cabinet is a perfect reflector at very low frequencies.
JinMTVT said:
A sealed box offers the smallest box size, along with the lowest efficiency.
A ported box utilizes the rear wave to extend the low end response. The problem with a ported box is that the front and the rear wave are out-of-phase. That's why it's overallsensitivity isn't any higher than a sealed box.
In a tapped horn, the rear wave is delayed so that it's IN PHASE with the front wave, but over a limited bandwidth.
That's why a tapped horn has higher efficiency, but over a narrower bandwidth than a ported box.
How's that?
Patrick Bateman said:
well that helps quite a bit in pointing the original intention in using a tapped horn
now how "limited" is that bandwith for a sub bass horn?
and what happens where we get near the limits of this limited range ?
where does a front loaded horn with absorbed rear wave stands in all that ?
would it provide with a better sound quality and good efficiency ?
JinMTVT said:
These are great questions, I really appreciate that you are asking them. I think there are a lot of 'lurkers' on audio forums who want these questions answered.
Before I answer them, think for a moment what a speaker is doing. It's simply moving air. That's it.
Now if our speaker is "moving air", how can we make it move air more efficiently?
A horn raises the efficiency by simply narrowing the beamwidth of where that air is going. As you can imagine, this is a lot like putting a lens in front of a lightbulb.
Which raises the question, why wouldn't we just use a conventional horn for sub bass? The answer is simple also - the wavelengths are too damn long! A 20hz sound wave is about as long as a CAR. Yes, a CAR length!
So a front loaded horn is just completely impractical for sub bass. There IS one exception to this rule.*
So now that we've ruled out front loaded horns, what does that leave us?
All we have left then are a handful of designs that utilize the REAR WAVE to move more air. Remember, this isn't voodoo - we're simply trying to move air efficiently.
I described ported boxes in the thread above. There are a few other boxes which ALSO use the rear wave.
TRANSMISSION LINE: Delays the rear wave so that it's it's in phase (but delayed) relative to the front wave. EVERY design which does this suffers from an Achilles Heel. The rear wave is only "in phase" at one frequency. At other frequencies, the difference in phase causes peaks and dips in the overall frequency response.
Peaks and dips are BAD right? So a transmission line uses stuffing to reduce high frequency output from the line, where the peaks and dips are most obnoxious.
TQWT: Quite similar to above. Something like a cross between a ported box and a TL.
DUAL REFLEX BANDPASS: Very similar to a single-reflex bandpass. Uses two ports at seperate frequencies. In my opinion, very difficult to get "right," because the front and the rear wave are NOT delayed.
TAPPED HORN: In my opinion, a tapped horn is very similar to a TL. Major difference is that there is no stuffing. In a TL, this would cause ragged response across the entire bandwidth. In a tapped horn, it's tuned to create a "notch" at a single frequency. Above that frequency, the tapped horn is not usable. But the "notch" makes it easier to cross it over for subwoofer duty. It's a clever compromise that offers higher efficency than a ported box, but sacrifices bandwidth.
The bottom line is that there's no "perfect box." If you want to raise efficiency, you have to sacrifice bandwidth, or use a bigger box.
nice info as always ...
i might be quite a bit OT
I have still to understand how you can have a smaller mouth area and still work in the same freq range ...
and how exactly does a tapped horn work in terms of waves and loading ? what is the front wave of the driver doing ?
what would be the size of a front loaded horn that would work for 20hz? ( base theorical size )
i do have alot of space avaialble for my HT sub bass unit!
i might be quite a bit OT
I have still to understand how you can have a smaller mouth area and still work in the same freq range ...
and how exactly does a tapped horn work in terms of waves and loading ? what is the front wave of the driver doing ?
what would be the size of a front loaded horn that would work for 20hz? ( base theorical size )
i do have alot of space avaialble for my HT sub bass unit!