re horns
Another way of looking at it Bass is that the output from the horn at around and below cut of is the same as that from the port output of a reflex box having a driver of the same Qt as the driver mounted on its air chamber.
If you were to have complete isolation between the port out put and the driver output, then the horn out put is in fact the very high Q resonance that you get from a high qt driver in a reflex box that is also tuned high, this is in fact what a fourth order box is, a reflex with only port output.
Another way of looking at it Bass is that the output from the horn at around and below cut of is the same as that from the port output of a reflex box having a driver of the same Qt as the driver mounted on its air chamber.
If you were to have complete isolation between the port out put and the driver output, then the horn out put is in fact the very high Q resonance that you get from a high qt driver in a reflex box that is also tuned high, this is in fact what a fourth order box is, a reflex with only port output.
BassAwdyO said:
Greets!
For the same reason you don't use a T/S max flat vented alignment in a corner app, unless a 'boomy' response is desired of course.
They're easy enough to design, especially with Leach's math, though it's best to over-size the compression chamber a bit and reduce it if required. Basically, you just find the Vb that puts the driver's impedance peak at the horn's Fc (Fh).
Done right, it doesn't sound like either a sealed or vented design since it has way more gain, flatter response, but with a highly damped sysQ. With today's low Qts, high Xmax drivers, cheap power and digital EQ though, I don't see the point in a HI-FI sub app since plenty loud, low distortion performance down into the teens can be had using a multiple driver IB or several low Qts sealed cabs.
GM
Re: re horns
rcw : No doubt,horns are resonant,nothing is non resonant.
I find your view curious in its stance,but not unfounded.
So a horn only sounds as good as a BP4 but because its big it must sound betterAre you perhaps also saying that the transient response is nothing improved over BR or BP4 but simply low harmonic distortion due to driver loading??
Regarding subjectivity and mystical horns beating your BP4 ABX,Im sure if you were keen you could ABX it with a large enough sample size (you).
Im also sure that some people might think your comments about this as being nasty,but I see your technical point whether I agree with it or not.
Mike.e
rcw said:
rcw : No doubt,horns are resonant,nothing is non resonant.
I find your view curious in its stance,but not unfounded.
So a horn only sounds as good as a BP4 but because its big it must sound betterAre you perhaps also saying that the transient response is nothing improved over BR or BP4 but simply low harmonic distortion due to driver loading??
Regarding subjectivity and mystical horns beating your BP4 ABX,Im sure if you were keen you could ABX it with a large enough sample size (you).
Im also sure that some people might think your comments about this as being nasty,but I see your technical point whether I agree with it or not.
Mike.e
johninCR said:
Do you mean a BLH with a large front chamber?
You can design a horn with no wasted space,with a maximally flat FR for the boundarys present,and a driver of nominal linearity and Vd driving it and achieve the best result possible.
Realistically speaking,nothing hugely better can be done in the near future. This is why there is no labhorn beater. Just different compromises.
We are still looking at a horn in the 4000litre volume for the cutoff in question
re horns
The point being that if you use a horn in that region it is neither fish nor fowl, neither a bandpass box or a horn, and not much chop at either.
You would at least in theory produce a much more optimum system if you built a dedicated bandpass box for that region, crossing over to a horn at around 80-100Hz.
At these frequencies you can make a straight horn that has exemplary
acoustic transformer performance and a mouth that's large enough.
This is something like the A7 type of box, without the compromise of trying to do two jobs with the one driver.
The point being that if you use a horn in that region it is neither fish nor fowl, neither a bandpass box or a horn, and not much chop at either.
You would at least in theory produce a much more optimum system if you built a dedicated bandpass box for that region, crossing over to a horn at around 80-100Hz.
At these frequencies you can make a straight horn that has exemplary
acoustic transformer performance and a mouth that's large enough.
This is something like the A7 type of box, without the compromise of trying to do two jobs with the one driver.
I believe RCW's saying that the eq'ing of a horn below its cutoff will give the horn the same characterstics as the bandpass box - but only below- it's cutoff frequency.
The difference is above the horns cutoff though. ie: build a horn with a cutoff at 30Hz, eq it flat to 25. 25 - 30Hz could well be similar to a BP enclosure, but as soon as the horn starts loading the similarities are gone. If you use a BP box all the way to 80Hz then you've got the BP signature right up to 80Hz. The region below 30Hz is pretty much 'unhearable' compared to the rest of the audio spectrum so I doubt you'd notice the difference on the horn. Also roomgain would ease the use of eq, as would the horns overall output, which would never be reached in a home environment.
Saying that, I'm planning on crossing the labs I'm building to sealed boxes at 30Hz/48dB/oct. But I want flat to 15Hz at least.
Rob
The difference is above the horns cutoff though. ie: build a horn with a cutoff at 30Hz, eq it flat to 25. 25 - 30Hz could well be similar to a BP enclosure, but as soon as the horn starts loading the similarities are gone. If you use a BP box all the way to 80Hz then you've got the BP signature right up to 80Hz. The region below 30Hz is pretty much 'unhearable' compared to the rest of the audio spectrum so I doubt you'd notice the difference on the horn. Also roomgain would ease the use of eq, as would the horns overall output, which would never be reached in a home environment.
Saying that, I'm planning on crossing the labs I'm building to sealed boxes at 30Hz/48dB/oct. But I want flat to 15Hz at least.
Rob
"when you do hook an amplifier to it things can frankly get as outrageous as you want them to. These hit extremely low. Paul and I measured a flat response still at 22 Hz."
Thats what Steve Deckert said about this little setup.
More about the Jensen Imperial:
"Along the journey we quickly found out that nothing man made that you could buy in any stereo shop could ever come remotely close to this cabinet as a subwoofer. It would make bass come out of almost anything. A 25 watt 10 inch pioneer woofer shook items off a neighbors shelf in the house across the street. Distance: 220 feet. It did that with one channel of a 22 watt class A receiver. The same woofer in the box it came out of with the same signal wouldn't shake a pencil, in fact, by comparison it was inaudible. It was in that moment I saw the light. It's been almost 20 years since and the passion it ignited actually created DECWARE. Since then, I've had the opportunity to hear most of the best speakers in the world. I bring that up because even today with all I've heard nothing in the consumer marketplace that's not custom built seems to be able to kick its ***.
In the years that followed we built several more of these cabinets and used them as subwoofers in large night clubs. This continued R&D gave us the opportunity to try a variety of things that otherwise would have been too costly. You're probably thinking who needs a bunch of thick heavy bass - night clubs always have sucky bass. Well, ironically the bass from the Imperial was just the opposite. Fast and effortless it was the benchmark of clean, flat, low bass
On one occasion a club owner wanted to hear what one would do in his own place so he called us up. On the spur of the moment we had to take what we had so we packed up a single Imperial, my frequency generator, and an old Harmon Kardon Reciever with one channel blown. Just before we got this call, we had been experiementing with a unique driver arangement. We removed the 15 inch woofer, and replaced it with a 12 inch woofer that was already mounted in a 1 cubic foot sealed cube. The response of the woofer in the cube was 3 dB down at 120 cycles. Basically ZERO bass. We installed this cube into the Imperial with the woofer facing the back of the encosure. The original 15 inch speaker opening was sealed. Installed the response was a bit different. Starting at the same 120 cycles and measuring the SPL at 90 dB in the room we slowly started to sweep the frequencies down until at 28.5 cycles the SPL had risen to 118 dB. That's a 28 dB of gain at 28.5 cycles! I really can't begin to describe what happens at that frequency when you hit that SPL, but it's serious. We saw a mouse stagger out of a crack in the concrete floor and die.
We gave the same demonstration in the night club for its owner, using only a single 12 inch woofer and 80 watts we were able to move the ash trays on 51 tables throughout the facility. It was an effective demonstration. He bought it, and we placed it into service with the 12 inch woofer that you couldn't move for the sealed box behind it - just to see how long it would last with 800 watts driving it all night long. The woofer lasted about 1 week and we got a service call. Upon inspection I was shocked to see 1/2 of the pulp speaker cone missing. It was all still inside the cube in the form of a powder. The largest fragment was less than 10 milimeters across. We saved that woofer for over 10 years just to look at it."
Read the whole article here
http://www.decware.com/imperial.htm
re bandpass
The point that I was trying to make Rob is that a single ported bandpass box has the same second order roll off as a sealed box below its f3 and you can design it so that it is 6db. more efficient.
This means that you can get 6db. more output from the same amplifier driver combination, i.e. you will need 4 sealed boxes and drivers and four times the power for the same output.
If you apply the same sort of equalisation then you can expect to get the same frequency responce and output as you get from 4 sealed box es as you get from the single second order bandpass box with the same equalisation, all the time noting that in fact your horn is acting exactly like the bandpass box in the same range anyway.
The difference being that the overall system is smaller and more ideal in its performance since you can design each section for optimum performance over its range instead of fiddling the horn box in such a way as that compromises its performance in order to make it smaller.
The only benefit accruing from this being that you maintain the illusion that it still is a horn when in fact it is some sort of psudo horn/ bandpass device that is not particularly good at either.
The point that I was trying to make Rob is that a single ported bandpass box has the same second order roll off as a sealed box below its f3 and you can design it so that it is 6db. more efficient.
This means that you can get 6db. more output from the same amplifier driver combination, i.e. you will need 4 sealed boxes and drivers and four times the power for the same output.
If you apply the same sort of equalisation then you can expect to get the same frequency responce and output as you get from 4 sealed box es as you get from the single second order bandpass box with the same equalisation, all the time noting that in fact your horn is acting exactly like the bandpass box in the same range anyway.
The difference being that the overall system is smaller and more ideal in its performance since you can design each section for optimum performance over its range instead of fiddling the horn box in such a way as that compromises its performance in order to make it smaller.
The only benefit accruing from this being that you maintain the illusion that it still is a horn when in fact it is some sort of psudo horn/ bandpass device that is not particularly good at either.
Hi RCW,
I believe that you'd only need 2 drivers, and twice the power to get +6dB, as long as they're close enough to couple acoustically.
The argument you have put forwards is for conditions below the horns cutoff. Above the cutoff then the horn will surely pull forwards from the 4th order box in performance, no ?
ie: Bretts labs 30Hz - 80Hz will have better performance than a 4th order BP box 30Hz - 80Hz. But below the 30Hz mark Bretts 4x12 drivers in the labs will have similar performance to the BP box.
Just trying to understand what you were saying earlier.
Personally I've always just added a second driver rather than port, but thats just my preference. I don't think there will be a sonic difference below 30Hz either way.
Rob.
I believe that you'd only need 2 drivers, and twice the power to get +6dB, as long as they're close enough to couple acoustically.
The argument you have put forwards is for conditions below the horns cutoff. Above the cutoff then the horn will surely pull forwards from the 4th order box in performance, no ?
ie: Bretts labs 30Hz - 80Hz will have better performance than a 4th order BP box 30Hz - 80Hz. But below the 30Hz mark Bretts 4x12 drivers in the labs will have similar performance to the BP box.
Just trying to understand what you were saying earlier.
Personally I've always just added a second driver rather than port, but thats just my preference. I don't think there will be a sonic difference below 30Hz either way.
Rob.
John
I'll try some modeling to. Maybe our two hamsters spinning on squeaky wheels will come up with something. The idea of lowering the limit of the horns response is great. But it has to be done with the same clean sound that we crave from the beasts. With what I have read it is really an expanded version of reactance annulling. The idea being that there could be a smooth roll off of 12 db/octave below the horn system cutoff. Come to think about it why could it not be equalized a bit and get the true sub cut off?
Regarding the size of boxes and the pic posted.
Sure there are smaller horn subs. I have studied a great many. Some are even reflex loaded below horn cutoff. They have definite peaks and dips in their output. The boxes are manageable in size.
I said what I did because from the direct radiator side of the argument they will come up with a 4 cubic foot over amped and Eq'd that has response to 14hz. They exist. And they have output down to the basement and volume to match. The kicker is the amount of power that they require. Kilowatts! Plus there is a difference in the distortion components the two different boxes produce. Short of using a servo.
But then again if you use a level playing field a servo could be incorporated in a horn to. The servo combined with John's idea would get the most bang for the buck. There is also Graham Maynard's phase coherent low end Eq circuit. The point to keep in mind is that the response below horn cutoff decline steeply at 24 db/octave. With an enlarged rear enclosure it should roll off at 12 db/octave. The active Eq will take a lot of power but work.
Mark
I'll try some modeling to. Maybe our two hamsters spinning on squeaky wheels will come up with something. The idea of lowering the limit of the horns response is great. But it has to be done with the same clean sound that we crave from the beasts. With what I have read it is really an expanded version of reactance annulling. The idea being that there could be a smooth roll off of 12 db/octave below the horn system cutoff. Come to think about it why could it not be equalized a bit and get the true sub cut off?
Regarding the size of boxes and the pic posted.
Sure there are smaller horn subs. I have studied a great many. Some are even reflex loaded below horn cutoff. They have definite peaks and dips in their output. The boxes are manageable in size.
I said what I did because from the direct radiator side of the argument they will come up with a 4 cubic foot over amped and Eq'd that has response to 14hz. They exist. And they have output down to the basement and volume to match. The kicker is the amount of power that they require. Kilowatts! Plus there is a difference in the distortion components the two different boxes produce. Short of using a servo.
But then again if you use a level playing field a servo could be incorporated in a horn to. The servo combined with John's idea would get the most bang for the buck. There is also Graham Maynard's phase coherent low end Eq circuit. The point to keep in mind is that the response below horn cutoff decline steeply at 24 db/octave. With an enlarged rear enclosure it should roll off at 12 db/octave. The active Eq will take a lot of power but work.
Mark
I don't understand the emphasis on EQ'g a horn below cutoff in the last few posts. Isn't that just begging for excursion problems? On the other hand enlarging the chamber on a rear horn moves the point where excursion increases rapidly to a lower frequency.
Is the Imperial a scoop? If take a scoop and make it's horn length 2m and make it's chamber size well over 100L, then yes. I think that changes the sonics quite a bit compared to typical scoops.
Is the Imperial a scoop? If take a scoop and make it's horn length 2m and make it's chamber size well over 100L, then yes. I think that changes the sonics quite a bit compared to typical scoops.
johninCR said:
I think its more that in a home environment the horn will never get near its x-max. This allows a fair bit of boost before problems arise.
I won't be boosting the labs I'm building - they'll be crossed right on the lower limit of the horn loading.
Re: the imperial. I haven't seen inside one - I think I'd have to pay for the plans. The 21" scoop I linked to has a 2.44 metre length, and a very quick rough calc gives approx 75L rear chamber. (If the rear chamber is what I think it is on the plan
)Whats the mouth size on the imperial ? - The scoop I linked to has a mouth of 3984 cm2, and it states in groups of 4 the loading is down to 28Hz. (35Hz for 1 unit)
Cheers,
Rob.
I use three sub horns loaded against the front wall and concrete slab floor. They get down into the teens at 125 db levels no problem. Mine are loaded with three eighteen inch JBL 2242H's.
Stargate Horn System (Obsolete)
Stargate Horn System (Obsolete)
An externally hosted image should be here but it was not working when we last tested it.
Here is one I built designed to go up against a wall. It has a 25 Hz flare and is loaded with a JBL 2241 18" woofer. It requires a 6 db boost at 20 cycles to get below 20 with authority.
An externally hosted image should be here but it was not working when we last tested it.
Rob,
I came up with about the same chamber size for that 21" super scooper, but that's for a 21" driver and the imperial was designed for a single 15". The scoops are designed for max efficiency, however, the Imperial was originally designed as a full range unit, so they sacrificed some efficiency for deeper extension which was a better match for the acoustic XO between the front radiation and horn output at about 90hz. BTW the imperial's mouth is 7600cm2 and it was designed for in wall installation and use as a single unit in mono.
The route I'd like to try eventually is an rear loaded horn array, at least to find out if what HornResp is telling me is real, and that is strong output more than an octave below Fs. If I can find someone to give me 24-32 of the CSS WR125ST's, I could make a sub unnecessary except for subsonic HT content.
I came up with about the same chamber size for that 21" super scooper, but that's for a 21" driver and the imperial was designed for a single 15". The scoops are designed for max efficiency, however, the Imperial was originally designed as a full range unit, so they sacrificed some efficiency for deeper extension which was a better match for the acoustic XO between the front radiation and horn output at about 90hz. BTW the imperial's mouth is 7600cm2 and it was designed for in wall installation and use as a single unit in mono.
The route I'd like to try eventually is an rear loaded horn array, at least to find out if what HornResp is telling me is real, and that is strong output more than an octave below Fs. If I can find someone to give me 24-32 of the CSS WR125ST's, I could make a sub unnecessary except for subsonic HT content.
RobWells said:
Greets!
Depends on the 'scoop's' design gain/BW. If a typical BLH designed for wide BW such as the Imperial's, then it's nothing more than a BR with a huge expanding vent, ergo has a relatively large filter chamber/throat and terminating at a shorter length/larger mouth. Limited BW 'scoops' are closer to being compression driven, with higher gain over a narrower BW via a smaller filter chamber/throat and longer pathlength to get to the minimum aceptable mouth area.
The former has greater acoustic (box) efficiency, while the latter has greater acoustic power, ergo lower distortion/higher SQ until the driver goes into thermal power or mechanical overload, which can be at quite low power if the CR is high, so only prosound drivers designed for the app/abuse should be used IMO, even in a HI-FI/HT app as half roll surround suspended drivers sound really obnoxious when they deform. Obviously, any driver suitable for a BR/TL app will work in a typical wide BW design BLH.
GM
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