Best to not mess with the beginning of the horn (compression chamber)
Seems the mouth can be screwed with without causing the dominoes to fall. I'm no horn expert but I've been reading about them for awhile. I'm a big believer is knowing what I'm doing before I make the first cut. Baltic Birch is some expensive firewood. Correct me if I'm wrong, but I think a front loaded horn would be easier to mess with the length and distance of the mouth? There are those folks that take two horns, put them at a 90 degree angle to each other and add a board across the tops to extend the mouth. That reportedly extends the response down lower so makes it "adjustable".
Multiples of 4 horns will do the same thing, drive the tuning lower. If you want one big sub--tie down strap them together.
The reason I'm learning Horn Response is to figure out how to get what I want with either 2 or 4 horns, tapped or front loaded horn and playing around with mouth extensions. The absolute worse I can do is learn something. The best thing I can do it contribute to the DIY board.
Now back to those vertical line arrays--second 48 tweeter line has been cut.
Seems the mouth can be screwed with without causing the dominoes to fall. I'm no horn expert but I've been reading about them for awhile. I'm a big believer is knowing what I'm doing before I make the first cut. Baltic Birch is some expensive firewood. Correct me if I'm wrong, but I think a front loaded horn would be easier to mess with the length and distance of the mouth? There are those folks that take two horns, put them at a 90 degree angle to each other and add a board across the tops to extend the mouth. That reportedly extends the response down lower so makes it "adjustable".
Multiples of 4 horns will do the same thing, drive the tuning lower. If you want one big sub--tie down strap them together.
The reason I'm learning Horn Response is to figure out how to get what I want with either 2 or 4 horns, tapped or front loaded horn and playing around with mouth extensions. The absolute worse I can do is learn something. The best thing I can do it contribute to the DIY board.
Now back to those vertical line arrays--second 48 tweeter line has been cut.
I think I see the source of the confusion. I am talking about THD figures, but I think weltersys is using the value of the 2nd harmonic, by itself.
I was taking his word, and not really examining his charts very closely.
But when I look at his chart of a dual-LAB12 bass-reflex box, this is what I see:
2nd harmonic - 24dB below the fundamental (~5%)
3rd harmonic - 28dB below the fundamental (~3%)
others above that too, each successively less.
When you add all the harmonics together, the THD much higher than the second harmonic by itself. That would account for the missing ~10dB.
Have you ever listened to a Bose 901 driver without the EQ or the cabinet? You might change your mind.
why pro drivers and not high power/excursion subwoofers in horns?
jut wondering about some basics? x max seems good to me for a subwoofer, pros drivers have 5mm, modern subwoofers have 20mm,
is efficiency really a good substitute for x max when power is cheap?
jut wondering about some basics? x max seems good to me for a subwoofer, pros drivers have 5mm, modern subwoofers have 20mm,
is efficiency really a good substitute for x max when power is cheap?
Hey, good question. I'll do my best to answer a good question.
The simple answer is that a horn is an acoustical transformer, it transforms high pressure low volume close to the driver, to low pressure high volume as it exits the horn. Obviously high pressure low volume (at the driver) requires low xmax, but requires good motor strength to create that pressure.
Think of a body builder punching the air. He's really strong, but not very effective, right? Now have him hold a 2'x2' board and punch, he can move much more air. Give the body builder a 4x8 sheet and he can move even more air. A full 2' swing of his glove (high xmax, low area of the glove) moves less air than a 2" movement (low xmax, high volume) of the 4x8 sheet of wood. That's the goal of the horn, to be able to move a lot of air, at low pressure.
To put this into math terms and give you an idea of how much of a difference we're talking about -- a typical direct radiator is about 2% efficient, while a horn can be 20% or even up to about 40% efficient, because the direct radiator is 'punching the air'
The simple answer is that a horn is an acoustical transformer, it transforms high pressure low volume close to the driver, to low pressure high volume as it exits the horn. Obviously high pressure low volume (at the driver) requires low xmax, but requires good motor strength to create that pressure.
Think of a body builder punching the air. He's really strong, but not very effective, right? Now have him hold a 2'x2' board and punch, he can move much more air. Give the body builder a 4x8 sheet and he can move even more air. A full 2' swing of his glove (high xmax, low area of the glove) moves less air than a 2" movement (low xmax, high volume) of the 4x8 sheet of wood. That's the goal of the horn, to be able to move a lot of air, at low pressure.
To put this into math terms and give you an idea of how much of a difference we're talking about -- a typical direct radiator is about 2% efficient, while a horn can be 20% or even up to about 40% efficient, because the direct radiator is 'punching the air'
True, up to the limits of his strength to 'quickly' move the board. (and many high xmax drivers have relatively weak motors)
An example -- a tc sounds LMS driver with 30mm xmax, and you put it in the SS15 horn.
You run out of power handling below 15mm xmax, so there is 15mm available xmax that is just wasted.
The goal out of this is to 'balance' the horn to the driver, so it runs out of xmax and power handling at the same time -- which is where the math comes in.
"(and many high xmax drivers have relatively weak motors)"
I don't think that is true, most high power driver have very big magnets.
I thought that the reason high power / excursion drivers wern't use was because their compliance and t/s don't match a horns needs well.
I don't think that is true, most high power driver have very big magnets.
I thought that the reason high power / excursion drivers wern't use was because their compliance and t/s don't match a horns needs well.
Jbell means with relative weak motors, the relation between the motor and the mass it needs to move. The T/S parameters do represent the parameters that include moving mass and motor strength.
Yep - most of the big boys have high BL. But also a lot of mass - more than is needed or desired for a lot of horn configurations.
But the line is becoming more and more blurred. At one time, a LAB12 type driver would have only been considered as a mid-grade car/HT sub. Try to build something along the lines of a labhorn where it's really a smaller element of a much larger array, but with even lower cutoff.... the BL and mass requirement both go up. The current crop of super-subs may very well work if the horn is big enough to need them.
A big magnet doesn't always mean a stronger motor. There are other factors at work.
The point is that you need most of that strength to overcome the high Mms.
Then there's not much motor strength left to use the extra excursion capability.
The 6.5" TB driver is a decent example here. In a 25Hz TH (linked on my sig), it will run out of Xmax at ~70w input. Yet it's rated thermally for 50w RMS. Of course, the extra 20w occasionally won't cook the driver. But scale all this up to some 15" drivers, if you need an extra 1000w (1000w to 2000w isn't a lot in SPL, but thermally is a huge challenge) to use the available Xmax, the driver will cook.
Chris
There are other factors at play here as well. Lower excursion means the driver stays more linear. Higher x-max is not without its caveats.
Plus horns sound oh-so-good. Low-distortion, fast rise times... a recipe for great sound.
Plus horns sound oh-so-good. Low-distortion, fast rise times... a recipe for great sound.
As JBell states, it is all about the balance
Granted, amp power is cheap but the amount of electricity from a wall outlet is finite. You can get only 15 to 20 amps and if you have only one 15 amp (residential party for example) All you stuff has to run on just that.
When people ask me how many watts my subwoofer amp outputs, I reply "26 decibel-watts of gain". 😕
If faced with the choice of a speaker at the same price and bandwidth, I choose efficiency first, then frequency response issues and keep an eye on Xmax.... power handling is low on the list. I'd much rather have a 200 watt woofer box that is 105dB efficient than a 89dB efficient woofer box that handles that handles 4,000 watts.
That is the major reason PA subwoofers are generally not made with car subwoofers--even with the power handling, they don't get loud enough on available power from the wall. That huge Xmax means a long coil which lowers efficiency. PA stuff errs on the side of efficiency so when packing them into horns, that design really helps lower the Xmax to keep them alive. Since car subs are meant to be used in sealed or ported cabinets they need the Xmax. Horns can cut stroke by 3 times lower so all that extra coil just lowers efficiency. Just like in cars, you have miles per gallon (KM per litre) and speakers are the same way, decibels per watt or max output with power compression.
Some car subwoofers CAN be used in PA horns, Danley Sound Labs uses a modified MTX 15" car sub in the Matterhorn. Which ones will work and which ones will not? You can calculate it out with a pencil, paper and a couple of pages of equations--or be a lazy, cheating pig like the rest of us and use Horn Response.
The JBL GTO 12" car sub does look interesting--heard it models well in Horn Response when used in pairs so it might be an option.
Granted, amp power is cheap but the amount of electricity from a wall outlet is finite. You can get only 15 to 20 amps and if you have only one 15 amp (residential party for example) All you stuff has to run on just that.
When people ask me how many watts my subwoofer amp outputs, I reply "26 decibel-watts of gain". 😕
If faced with the choice of a speaker at the same price and bandwidth, I choose efficiency first, then frequency response issues and keep an eye on Xmax.... power handling is low on the list. I'd much rather have a 200 watt woofer box that is 105dB efficient than a 89dB efficient woofer box that handles that handles 4,000 watts.
That is the major reason PA subwoofers are generally not made with car subwoofers--even with the power handling, they don't get loud enough on available power from the wall. That huge Xmax means a long coil which lowers efficiency. PA stuff errs on the side of efficiency so when packing them into horns, that design really helps lower the Xmax to keep them alive. Since car subs are meant to be used in sealed or ported cabinets they need the Xmax. Horns can cut stroke by 3 times lower so all that extra coil just lowers efficiency. Just like in cars, you have miles per gallon (KM per litre) and speakers are the same way, decibels per watt or max output with power compression.
Some car subwoofers CAN be used in PA horns, Danley Sound Labs uses a modified MTX 15" car sub in the Matterhorn. Which ones will work and which ones will not? You can calculate it out with a pencil, paper and a couple of pages of equations--or be a lazy, cheating pig like the rest of us and use Horn Response.
The JBL GTO 12" car sub does look interesting--heard it models well in Horn Response when used in pairs so it might be an option.
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Although the words "Pro driver", "PA Driver" and "Car Driver" do suggest their specific use, none of these names are defined with electrical and/or physical capabilities. Therefore there is no such thing as a car driver that can or cannot work in a horn. Most indications, if a driver will work in a specific design concept, can be found in the Thiele-Small parameters.
hey... I resemble that remark !! (and liked it)
all good comments on this topic. It was a well asked question, and good responses from all.
yes, the jbl gto's are good horn drivers.
Even eminence kinda bucked the car audio uber xmax, uber low sensitivity trend with a couple of their 'car audio' drivers.
They realized that most of us use amps 400 watts and less in our cars. Amps that cost less than $500 top out around there, regardless of what is claimed. So they have a line of "car subs" that make the most of that. The new subs aren't too much removed from the Dayton Series 2 (also by Eminence, and which also work quite well in horns).
Wayne,I think I see the source of the confusion. I am talking about THD figures, but I think weltersys is using the value of the 2nd harmonic, by itself.
I was taking his word, and not really examining his charts very closely.
But when I look at his chart of a dual-LAB12 bass-reflex box, this is what I see:
2nd harmonic - 24dB below the fundamental (~5%)
3rd harmonic - 28dB below the fundamental (~3%)
others above that too, each successively less.
When you add all the harmonics together, the THD much higher than the second harmonic by itself. That would account for the missing ~10dB.
The addition of the additional harmonics hardly makes a very small difference in the total, which is why I did not bother with all the math.
For example:
Fundamental tone =100 dB SPL, Second Harmonic =80 dB SPL (-20 dB), Third Harmonic =70 dB SPL (-30 dB), Fourth Harmonic =60 dB SPL (-40 dB)
Sum the squares of the distortion, then take the square root of the sum:
-20 dB =10% distortion, -30 dB =3.16% distortion, -40 dB =1% distortion, so:
(10x10=100) + (3.162x3.162=10) +(1x1=1) =111, the square root of which is 10.535, or 10.5% THD.
If you want to go through all my charts and do the math for about .5% difference, go ahead.
You will find since I rounded up to the nearest percentage point already that the difference will be quite small.
Have fun !
Art Welter
The 16% distortion @50 Hz for the TH design was excursion related, different distortion resulted with different speakers in the same cabinet.
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