Hi,
That's why I waited so long before getting one, I was afraid it would ruin my system.
Modifying is clearly a good plan. The most important IMHO is to use a linestage with lots of gain in order to not lose resolution. There's lots of info on the DCX2496-group, I would encourage anyone thinking of going this way to check out this info there.
There's also other digital crossovers out there,
they are developing new ones all the time
cheers 😉
Retsel said:
That's why I waited so long before getting one, I was afraid it would ruin my system.
Modifying is clearly a good plan. The most important IMHO is to use a linestage with lots of gain in order to not lose resolution. There's lots of info on the DCX2496-group, I would encourage anyone thinking of going this way to check out this info there.
There's also other digital crossovers out there,
they are developing new ones all the time
cheers 😉
Coolin said:
Greets!
Output without the horn.
No, a PWT tells you the driver's response. For a 'perfect' match, the lens response should be the inverse of the PWT's. Unless I happen to want to use a particular lens I couldn't care less what a driver's response is on it, so normally I'm not even going to consider one that doesn't offer a PWT response.
Right, a high CR driver is pretty much limited to ~4 octaves since the small 'St' required and the air mass in the lens damps the driver's HF response.
Again, we don't want a too small 'St' to ensure that the output is ~flat through the desired XO point's BW to get good summing. It's that, or make a complex phase plug so a small enough 'St' can be used to increase the horn's effective BW far enough beyond the XO point to ensure good summing.
No, if you use these simple rules-of-thumb then the coverage angle is what it is. If you pick some others then you have to adjust either and/or increasing 'Sm', length. The minimum length, 'Sm', 'St', and CR limitations still apply.
GM
re plane wave tubes
A plane wave tube acts acoustically as an infinite horn with the same throat area as the area of the tube.
All horn shapes no matter what converge upon a constant acoustic resistance at a frequency sufficiently above the flare cut off, and the reactive part of the impedance becomes very small.
In finite horns the mismatch between the throat and mouth impedance cause ripples in this that are characteristic of a particular horn, thus the plane wave tube acts as a perfect horn with no reflections.
Since the air is for practicle purposes purely resistive it acts as a stationary medium through which waves are propagated, and this is why the mass corner only has the total driver moving mass in its expression, since for a compression driver the mass corner occurs at a frequency where the air is practically purely resistive.
A conical horn has a far larger transition region between where mass reactance is important and where its impedance becomes purely resistive than an exponential horn does.
As mentioned before the frequency responce in a plane wave tube is a measure of the total acoustic power output of a driver, and this will be the on axis responce only for a cd device, exponential and tractrix horns are not cd and their increasing directivity with frequency gives these an on axis frequency responce that is well above the mass corner.
The total radiated power is however goverened by the mass corner and the expression I mentined before is valid for a driver that is used with a throat area the same as the diaphram area, the mass corner increasing in frequency with the compression ratio.
A plane wave tube acts acoustically as an infinite horn with the same throat area as the area of the tube.
All horn shapes no matter what converge upon a constant acoustic resistance at a frequency sufficiently above the flare cut off, and the reactive part of the impedance becomes very small.
In finite horns the mismatch between the throat and mouth impedance cause ripples in this that are characteristic of a particular horn, thus the plane wave tube acts as a perfect horn with no reflections.
Since the air is for practicle purposes purely resistive it acts as a stationary medium through which waves are propagated, and this is why the mass corner only has the total driver moving mass in its expression, since for a compression driver the mass corner occurs at a frequency where the air is practically purely resistive.
A conical horn has a far larger transition region between where mass reactance is important and where its impedance becomes purely resistive than an exponential horn does.
As mentioned before the frequency responce in a plane wave tube is a measure of the total acoustic power output of a driver, and this will be the on axis responce only for a cd device, exponential and tractrix horns are not cd and their increasing directivity with frequency gives these an on axis frequency responce that is well above the mass corner.
The total radiated power is however goverened by the mass corner and the expression I mentined before is valid for a driver that is used with a throat area the same as the diaphram area, the mass corner increasing in frequency with the compression ratio.
Thanks GM and rcw !
I'm pretty sure i understand.
However i'm not too good with the math. Does anyone have a good link with explanations and formulas for the T-S parameters specifically for horns ?
rcw: checking if i understand what you said about the mass corner.
A 2 inch driver with a 1 inch exit has a CR of ~3:1 thus the mass corner also moves up 300% ? I cant seem to simulate this with hornresponce.
Although irrellavant to the thread i'm starting to design my own first "low" compromise bass horn. Length about 4 meters and the conical also seems to do well in the low end.
It looks like the only way to get a flatter phase trace is to loose all of the drivers mass. (ignoring Le for the highs)
I can use time delay but it will only be optomised for one freq.
Or are there other tricks?
Later, Collin
I'm pretty sure i understand.
However i'm not too good with the math. Does anyone have a good link with explanations and formulas for the T-S parameters specifically for horns ?
rcw: checking if i understand what you said about the mass corner.
A 2 inch driver with a 1 inch exit has a CR of ~3:1 thus the mass corner also moves up 300% ? I cant seem to simulate this with hornresponce.
Although irrellavant to the thread i'm starting to design my own first "low" compromise bass horn. Length about 4 meters and the conical also seems to do well in the low end.
It looks like the only way to get a flatter phase trace is to loose all of the drivers mass. (ignoring Le for the highs)
I can use time delay but it will only be optomised for one freq.
Or are there other tricks?
Later, Collin
re mass corner
No Coolin the mass corner does not increase in that proportion.
References to T-S parameters for horns can be found on Don Keeles site in the pre-print section.
No Coolin the mass corner does not increase in that proportion.
References to T-S parameters for horns can be found on Don Keeles site in the pre-print section.
Re: re mass corner
It looks like his site is being updated at the moment. I cant find any pre-print section. Any other links?
rcw said:
It looks like his site is being updated at the moment. I cant find any pre-print section. Any other links?
re keele
I tried ... www.dbkeele.com and in the official website found the pre prints under AES papers section.
Another classic paper is by Leach in the AES Journal of 1979, "On the specification of moving coil drivers for low frequency horn loudspeakers", this is the paper most horn modellers use as a theoretical basis, but if maths is not your thing you will find it heavy going.
I tried ... www.dbkeele.com and in the official website found the pre prints under AES papers section.
Another classic paper is by Leach in the AES Journal of 1979, "On the specification of moving coil drivers for low frequency horn loudspeakers", this is the paper most horn modellers use as a theoretical basis, but if maths is not your thing you will find it heavy going.
Ive zipped through the paper and indeed its not my thing regarding all the equasions. My personal way of learning is through understanding why things happen/work that way and i cant see much looking at a bunch of formulas. I might be able to use a few but i dont see the larger picture that way.
it occurs to me that most of this has already been implemented in Hornresponce right? This is so much easier for me.
Its also pretty complete as far as i can see.
Or are there any missing functions or flaws in te program that i should watch out for?
On Keeles website there should be some kind of calculator but its not ready yet. Is that any good ?
Regards,
Collin
it occurs to me that most of this has already been implemented in Hornresponce right? This is so much easier for me.
Its also pretty complete as far as i can see.
Or are there any missing functions or flaws in te program that i should watch out for?
On Keeles website there should be some kind of calculator but its not ready yet. Is that any good ?
Regards,
Collin
formula
I haven't checked any of them Coolin so I can't say one way or the other.
Most of them seem to use some variation on the Mappes O'Riorden model, and this is not much good above around 400Hz.
I haven't checked any of them Coolin so I can't say one way or the other.
Most of them seem to use some variation on the Mappes O'Riorden model, and this is not much good above around 400Hz.
RobWells said:
The rear chamber used for the driver of a front-loaded bass horn may be reflex loaded instead of sealed. It has to be tuned so that the additional resonance peak from the reflex is added reasonably below the lowest one from the horn (30..40Hz), thus extending LF efficiency and reducing cone excursion. Obviously, a compromise between 'too big', 'too much standing waves' and 'too small' has to be found for the volume of rear chamber.
I've tried and it works fine. It doesn't show the characteristic colouration from high Qb reflex systems at all.
re w bin
The jbl 4518 "keele" box is a classic example of this type.
The Altec A7 from an earlier era also employed this principle.
The jbl 4518 "keele" box is a classic example of this type.
The Altec A7 from an earlier era also employed this principle.
You both are right, but I don't like how it is implemented in these designs. Altecs have a too wide direct-radiation zone between the lower cutoff of the horn and the 36Hz (or so) tuned reflex. W-bins usually have their reflex pipes placed in the front side and perpendicular to the driver in such a way that a lot of midbass content (and chamber standing waves) leaks through them (absolutely undesirable effect). There is a lot to improve here.
Hi all
I have never tried a vented rear chamber on bass-horns, so have no practical experience ...
W-bins could possibly be vented to the rear but that means that they have to be placed some distance from the wall, making the W-bins appear larger than they actually are in a home envirement.
If meant for subwoofer use W-bins could maybe be reflex vented in front the conventional way, but turned "backwards" to fire into the corners of the room, crossed over to midbasshorns at say 60Hz or so?
I have been thinking of trying a similar soulution for my own listening room, "floor-to-ceiling"
W-bin subs firing "backwards" into the corners of the front wall. Haven't thought of reflex loading them, but it may be an interesting alternative....
cheers 😉
Eva said:
I have never tried a vented rear chamber on bass-horns, so have no practical experience ...
W-bins could possibly be vented to the rear but that means that they have to be placed some distance from the wall, making the W-bins appear larger than they actually are in a home envirement.
If meant for subwoofer use W-bins could maybe be reflex vented in front the conventional way, but turned "backwards" to fire into the corners of the room, crossed over to midbasshorns at say 60Hz or so?
I have been thinking of trying a similar soulution for my own listening room, "floor-to-ceiling"
W-bin subs firing "backwards" into the corners of the front wall. Haven't thought of reflex loading them, but it may be an interesting alternative....
cheers 😉
With venting the rear chamber, what effect does this have on distortion? As I understand, the sealed rear chamber of a front loaded horn is critical in causing the driver to operate in a more linear way. Also what about cone excursion below the tuning? Would that then become much worse and hence need a HP filter?
Please pass the filters!
A horn can be loaded below it's Fs with the output of a port. You know that for sure. Below the tuning frequency of the port it is indeed going to flap wildly. THe best thing in this case is a 6th order alignment. The trade of is that there will be two Eq stages required to keep the output of the horn/reflex system in balance.
The real trick would be to design a horn to the lower end of where the room gain took off. Then use the port idea to pickup where the horn unloads. THis is very room dependant. But will work if the idea is implemented correctly.
Mark
A horn can be loaded below it's Fs with the output of a port. You know that for sure. Below the tuning frequency of the port it is indeed going to flap wildly. THe best thing in this case is a 6th order alignment. The trade of is that there will be two Eq stages required to keep the output of the horn/reflex system in balance.
The real trick would be to design a horn to the lower end of where the room gain took off. Then use the port idea to pickup where the horn unloads. THis is very room dependant. But will work if the idea is implemented correctly.
Mark
Re: re plane wave tubes
Greets!
Please elaborate on this since it's quite contrary to my understanding of how it changes in a compression loaded horn.
TIA,
GM
rcw said:
Greets!
Please elaborate on this since it's quite contrary to my understanding of how it changes in a compression loaded horn.
TIA,
GM
Coolin said:
Greets!
You're welcome!
Contrary to popular opinion, you can horn load anything and get good performance if you know what you're doing, but to get the most performance out of the smallest package severely limits driver selection, so for compression loaded designs best IMO to just consider HE prosound units.
A 2" effective diameter driver with a 1" diameter exit is a 4:1 CR.
FWIW, M = 0.6-0.7 is considered to be the best overall for basshorns.
GM
Eva said:
Greets!
Hmm, with the exception of the large 210/211 theater midbass horns that are tuned to ~35 Hz, all the smaller ones are tuned to ~55-62 Hz depending on whether one or two drivers. Since tuning should be ~a half octave below the horn's Fc, all the VOT cabs are tuned too low for best horn gain extension when driven with SS amps. Driven with a variable high output impedance amp like they were originally designed for and the blend is much better.
Unfortunately, they waited too long and lost too much market share before addressing this issue with the A700 series, so I assume they didn't sell well since I've never seen any other than the demo unit at the local distributor.
Yeah, best IMO to just dump the vent output back into .
GM
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