using box size as a THE deciding factor...a dipole (OB or H frame or otherwsie) seems to the most inefficient method to produce bass. albeit without boom. isobariks are slightly more efficient.
sealed boxes (with Qts < 0.7 and aperiodic) are a bit more efficient than isobariks. horns while being efficient in absolute terms are not so when you factor in box size (db/w per cu. ft of box)
that leaves TL and bass reflex. My guess is that bass reflex produce the most quantity of bass out of a given box size.
now if you are factoring in bass quality just about all these systems if properly designed for their particular enviroments can produce good if not startling results. This I feel is the STRATEGIC advantage of being DIY. We as DIYers can choose what suits our listening tastes, home decor and other requirements.
for example.....
if you have a 12" woofer that can produce 100db in a 3 cu. ft. sealed box, youd need 4 similar woofers to produce the same SPL in dipole.
The same woofer could (given it's T/S parameters are suitable) also produce 100db in a horn with very little wattage but the horn box would be considerably larger than 3 cu. ft. or the F3 would be considerably higher if the horn were to fit in 3 cu.ft.
the same woofer in a well damped BR would produce about 6db more in a box that is maybe 10% larger (this depend a lot on T/S parameters).
horns tend to have "slam", dipoles tend to sound "smooth and natural", bass relfex boxes tend to sound boomy, sealed boxes are somewhere in between.
I think we are all searching for that holy grail. a speaker that has slam and depth, does not boom, sounds natural, fits in with WAF's demands, and to to it costs next to nothing. If we weren't we would not be here.
sealed boxes (with Qts < 0.7 and aperiodic) are a bit more efficient than isobariks. horns while being efficient in absolute terms are not so when you factor in box size (db/w per cu. ft of box)
that leaves TL and bass reflex. My guess is that bass reflex produce the most quantity of bass out of a given box size.
now if you are factoring in bass quality just about all these systems if properly designed for their particular enviroments can produce good if not startling results. This I feel is the STRATEGIC advantage of being DIY. We as DIYers can choose what suits our listening tastes, home decor and other requirements.
for example.....
if you have a 12" woofer that can produce 100db in a 3 cu. ft. sealed box, youd need 4 similar woofers to produce the same SPL in dipole.
The same woofer could (given it's T/S parameters are suitable) also produce 100db in a horn with very little wattage but the horn box would be considerably larger than 3 cu. ft. or the F3 would be considerably higher if the horn were to fit in 3 cu.ft.
the same woofer in a well damped BR would produce about 6db more in a box that is maybe 10% larger (this depend a lot on T/S parameters).
horns tend to have "slam", dipoles tend to sound "smooth and natural", bass relfex boxes tend to sound boomy, sealed boxes are somewhere in between.
I think we are all searching for that holy grail. a speaker that has slam and depth, does not boom, sounds natural, fits in with WAF's demands, and to to it costs next to nothing. If we weren't we would not be here.
paulspencer said:
This does not occur with modern well executed designs -
This is a fallacy that is a holdover from decades ago.
Horns have moved far beyond this.
Horn loading of the front and rear is something that has been talked about a good bit but is not something I remember anyone.
having done successfully
I am running Lowther DX4's open backed on Azurahorns. There is a small dipole effect from the rear - but since the rear is not horn loaded it is down in output - I have never attempted to measure how much or determine by serious listening the benefit derived from this - Sounds good though _grin_
Regards
Ken L
Konnichiwa,
Only in the region where the horn actually controls dispersion, which is directly determined by the size of the hornmouth. Below this most "domestic" horns operate as resonant systems (TL, Reflex) to produce extended bass, while incorporating room placement gain to boost the LF into place. The result is highly inaccurate LF rendition, with a lot of room mode excitation.
You are in big LF trouble unless you can make a Bass Horn with a mouth surface commesurate to the required wavelenth (eg like here
....
Horns are usually corner loaded. As they are not any longer strongly directional below the flare cutoff they will from their position maximally excite all room modes.
All the above holds true for an IDEAL horn with a sufficiently large mouth area. This automatically means architecturally, build in structures with several squaremeters mouth opening. Once you move towards shrunken and foreshortened horns only high output remains, the rest is traded off for (comparably) small size.
I would say that dipoles are drastically different from horns in that they operate as velocity transducers, as opposed to pressure transducers (Horns, Sealed Boxes, Reflex or Organpipe reflex [aka TL]). This has implications for room mode excitation that goes far beyond the normally discuused issues.
A dipole will excite room modes maximally in the absolute centre of the room and minimally in a corner. All other speakers maximally excite room modes in the corner and minmally in the room centre.
This of course depends upon your defintion of "better".
Dipole.
A Full Size Horn with a large rear chamber (eg architectural horn) is about level with a dipole, except on distortion for a given SPL with a given driver. Shrunken Horns are much worse than dipoles.
Sayonara
paulspencer said:
Only in the region where the horn actually controls dispersion, which is directly determined by the size of the hornmouth. Below this most "domestic" horns operate as resonant systems (TL, Reflex) to produce extended bass, while incorporating room placement gain to boost the LF into place. The result is highly inaccurate LF rendition, with a lot of room mode excitation.
You are in big LF trouble unless you can make a Bass Horn with a mouth surface commesurate to the required wavelenth (eg like here
....
paulspencer said:
Horns are usually corner loaded. As they are not any longer strongly directional below the flare cutoff they will from their position maximally excite all room modes.
paulspencer said:
All the above holds true for an IDEAL horn with a sufficiently large mouth area. This automatically means architecturally, build in structures with several squaremeters mouth opening. Once you move towards shrunken and foreshortened horns only high output remains, the rest is traded off for (comparably) small size.
paulspencer said:
I would say that dipoles are drastically different from horns in that they operate as velocity transducers, as opposed to pressure transducers (Horns, Sealed Boxes, Reflex or Organpipe reflex [aka TL]). This has implications for room mode excitation that goes far beyond the normally discuused issues.
A dipole will excite room modes maximally in the absolute centre of the room and minimally in a corner. All other speakers maximally excite room modes in the corner and minmally in the room centre.
paulspencer said:
This of course depends upon your defintion of "better".
paulspencer said:
Dipole.
paulspencer said:
A Full Size Horn with a large rear chamber (eg architectural horn) is about level with a dipole, except on distortion for a given SPL with a given driver. Shrunken Horns are much worse than dipoles.
Sayonara
Re: Re: Horn vs Open baffle bass
Is this why very cheap drivers can work to such good effect ?
I guess that once I build high output dipole subs and room treatment becomes more necessary, I will need panel absorbers or slot resonators, and tube traps in the corners would be ineffective.
By the way, thank you very much for stepping in and providing some very interesting information.
Kuei Yang Wang said:
Is this why very cheap drivers can work to such good effect ?
Kuei Yang Wang said:
I guess that once I build high output dipole subs and room treatment becomes more necessary, I will need panel absorbers or slot resonators, and tube traps in the corners would be ineffective.
By the way, thank you very much for stepping in and providing some very interesting information.
Re: Re: Re: Horn vs Open baffle bass
Konnichiwa,
I don't THINK so, BWTFDIK.
No, tubetraps in corners will be as effective with dipoles as they are with normal speakers (eg completely ineffective for standing waves). The point is that near a wall the pressure of the air for sound is high while the velocity of the air is low. In the middle of the room the air velocity is high while preassure is low. Hence the two different ways dipoles and other speakers couple to room modes.
Sayonara
Konnichiwa,
johninCR said:
I don't THINK so, BWTFDIK.
johninCR said:
No, tubetraps in corners will be as effective with dipoles as they are with normal speakers (eg completely ineffective for standing waves). The point is that near a wall the pressure of the air for sound is high while the velocity of the air is low. In the middle of the room the air velocity is high while preassure is low. Hence the two different ways dipoles and other speakers couple to room modes.
Sayonara
Just a short note - if you are concerned with remaining room effects of dipoles, one or 2 easy notch filters (active) will work wonders for the dominant room modes. It's not just that the drone goes away, it's thatthe midrange clears up significantly.
Build your speakers, place them where yu will play them, and then just do a simple FR test, even with continuous tones or 1/3 octave filtered pink noise (test CD). Then you see where your broad peaks are, and their magnitude. For me it was a broad (low q) peak around 90 hz), and one single -6 dB motch filter made a day and night difference.
I also remember KYW's glowing words about the Behringer room EQ (KYW - do you still use it?). That's more accurate of course. But more pricey.
Build your speakers, place them where yu will play them, and then just do a simple FR test, even with continuous tones or 1/3 octave filtered pink noise (test CD). Then you see where your broad peaks are, and their magnitude. For me it was a broad (low q) peak around 90 hz), and one single -6 dB motch filter made a day and night difference.
I also remember KYW's glowing words about the Behringer room EQ (KYW - do you still use it?). That's more accurate of course. But more pricey.
KYW,
I don't understand the velocity vs pressure thing.
Please correct me if I'm wrong, but this is my understanding of the difference between dipole and others when it come to room interaction. Dipoles radiate sound primarily in 2 directions front and rear because the sideways and vertical energies cancel each other out since they are out of phase. This results in reflections primarily on the front and back walls. Other speakers radiate sound in all directions and making the early reflections more complex and numerous so where reflecting surfaces meet (a corner) the pressure builds much more than with a dipole.
I don't understand the velocity vs pressure thing.
Please correct me if I'm wrong, but this is my understanding of the difference between dipole and others when it come to room interaction. Dipoles radiate sound primarily in 2 directions front and rear because the sideways and vertical energies cancel each other out since they are out of phase. This results in reflections primarily on the front and back walls. Other speakers radiate sound in all directions and making the early reflections more complex and numerous so where reflecting surfaces meet (a corner) the pressure builds much more than with a dipole.
Konnichiwa,
Think about a wave standing between two surfaces. It matters not if the wave is in liquid, gas or solid. The medium the wave is transmitted through reacts with compression and rarefaction. Now near a surface the rarefaction or compression cannot "move" the medium being compressed or rarified, so hence we experience pressure effects. Equally, to make the medium compress or rarify we need to excert pressure, as no amount of velocity change input will amount to much, as the velocity of movement is near zero.
Now velocity is the opposite. If we now go to the exact "middle" between the two surfaces we will always find a pressure of equilibrium, never a deviation from even pressure. Yet at any given instant we have a lot of displacement of the medium back and forth at this point. So the VELOCITY of the medium is at the maximum, yet the pressure is at a minimum. So no matter how much pressure you excert, you will have little output, but a little velocity will go a long way.
Does that make it at all clearer?
Room interactions in the DIFFUSE sound zone, yes. The radiation is still of course directional at low frequencies, but directionality alone doies not reduce standing waves (see LF Horns).
All of this is related to the "diffuse" mode, not to modal behaviour. The two are distinctly different.
Sayonara
johninCR said:
Think about a wave standing between two surfaces. It matters not if the wave is in liquid, gas or solid. The medium the wave is transmitted through reacts with compression and rarefaction. Now near a surface the rarefaction or compression cannot "move" the medium being compressed or rarified, so hence we experience pressure effects. Equally, to make the medium compress or rarify we need to excert pressure, as no amount of velocity change input will amount to much, as the velocity of movement is near zero.
Now velocity is the opposite. If we now go to the exact "middle" between the two surfaces we will always find a pressure of equilibrium, never a deviation from even pressure. Yet at any given instant we have a lot of displacement of the medium back and forth at this point. So the VELOCITY of the medium is at the maximum, yet the pressure is at a minimum. So no matter how much pressure you excert, you will have little output, but a little velocity will go a long way.
Does that make it at all clearer?
johninCR said:
Room interactions in the DIFFUSE sound zone, yes. The radiation is still of course directional at low frequencies, but directionality alone doies not reduce standing waves (see LF Horns).
johninCR said:
All of this is related to the "diffuse" mode, not to modal behaviour. The two are distinctly different.
Sayonara
paulspencer said:
Magnetar,
Could you elaborate a little more?
Dipoles aren't pressure loaded by a sealed box and this eliminates box coloration and I suspect that this makes them a little more "accurate."
I can't see how dipoles would actually be any better with room modes than horns. If I'm mistaken, then could someone expand on why?
What if an attempt was made to get the best of both. A dipole where both the front and rear wave was horn loaded. Or, perhaps more practical, an Infinite baffle where the front wave is horn loaded.
The dipole is just paddling the air and has a very poor interface with the room air. It relies on using drivers that are overly resonant to overcome this. In all cases these drivers have to have long excursions to pressurize the room (and your ears) to reproduce bass. Our ears are insensive in the lower range and it makes much more sense to use a horn that excels in pressurizing the air. The horn is an impedence transformer -- it will barely be working when the dipole is near it's limit. IOW it will move air with A LOT less work, hence it is a high efficiency device.
Anytime you you put a loudspeaker in a home listening room you will excite room modes -- A properly designed horn is designed from the start to interface with the room -- in fact, it needs the room reinforcement to really do it's job properly. If there is no room to place the horn in then the horn has to be the size of a room to reproduce the deep bass.
I have built dual driver dipole isobaric loaded horns that are front loaded and worked quite well in my room. The main advantage however was the distortion cancellation of the isobaric design not the figure 8 room interface.
IME either method (horn or dipole) can be quite satisfying but when you really get down to it the horn is king at realistic life like reproduction, power, speed and FUN.
Thought I’d post the to & fros from an off-line discussion on the same subject, to re-stir debate:
> horns ain't all about being loud. They sound fantastic at low volumes. When I talk about effortlessness you may equate that to loudness but what it means is a complete lack of strain - strain you wouldn't notice until you don't hear it.
I must hear this.
> The further a loudspeaker cone moves the more distortion it produces.
I've heard that postulated before, but if it has been measured, I haven’t seen it. Is there a link??
I can imagine it true nearer the extremes of excursion, but in a good driver find it difficult to accept at say up to 75% of Xmax.
Even if so, the horn will suffer more from room effects. Which is better in sum, lower excursion distortion or less room effects??
Yes the two drivers together must both work harder in a dipole, but unless the above (cone distortion proportional to excursion) is verifiable, is their a problem with higher excursions than other systems?
> Compare it to a properly done horn system (which will be ridiculously large) and there is no comparison.
Two things, most may accept large, eg the Labhorn, but not ridiculously large.
And compare on what criteria, excursion/ efficiency, or clean sound?
I actually seriously considered going horns, was deterred by size, but still think the dipole is a better all round approach for most normal domestic situations.
> horns ain't all about being loud. They sound fantastic at low volumes. When I talk about effortlessness you may equate that to loudness but what it means is a complete lack of strain - strain you wouldn't notice until you don't hear it.
I must hear this.
> The further a loudspeaker cone moves the more distortion it produces.
I've heard that postulated before, but if it has been measured, I haven’t seen it. Is there a link??
I can imagine it true nearer the extremes of excursion, but in a good driver find it difficult to accept at say up to 75% of Xmax.
Even if so, the horn will suffer more from room effects. Which is better in sum, lower excursion distortion or less room effects??
Yes the two drivers together must both work harder in a dipole, but unless the above (cone distortion proportional to excursion) is verifiable, is their a problem with higher excursions than other systems?
> Compare it to a properly done horn system (which will be ridiculously large) and there is no comparison.
Two things, most may accept large, eg the Labhorn, but not ridiculously large.
And compare on what criteria, excursion/ efficiency, or clean sound?
I actually seriously considered going horns, was deterred by size, but still think the dipole is a better all round approach for most normal domestic situations.
I've come to the conclusion that nothing beats dipole bass when it comes to fidelity at moderate to moderately loud SPL levels. Although it is the one way of making bass that gives up the most output and efficiency, it also deals with room modes the best, which is the most difficult problem to overcome. You can use eq but this will not work for all the positions you may be concerned with. Dipoles also totally eliminate the effect of the box, something which only infinite baffle is able to do. As I see it, dipoles make the least compromises in fidelity and the most in output. So if you can live with the size and cost involved in order to get the SPL that you want, dipoles are the way to go.
This is a very big IF however, and most will not accept this, don't have the space and/or can't afford to buy enough displacement to get the output they want.
Keep in mind I'm talking about bass here only ...
If you have space or the ability to build-in the speakers and you want very loud and clean, then I think horns are the way to go.
Infiniate baffle may be a contender as you can buy a number of high excursion 15" or 18" drivers, but you end up spending a lot of money on amplifiers and drivers and half the energy goes into the roof space - then you also need to consider noise reduction.
If you want 110 db at your seating position then it is hard to go past horns, but if we are just considering accuracy I think dipole bass is without equal.
Ultimately I would like to build a home theatre room with a large dipole array either side of a large screen crossing over at 100 Hz to a pair of very large built-in bass horns to produce 120 db at all seating positions. I also plan to build a music only system in a living room using full range dipoles similar to Linkwitz Phoenix or Orion.
This is a very big IF however, and most will not accept this, don't have the space and/or can't afford to buy enough displacement to get the output they want.
Keep in mind I'm talking about bass here only ...If you have space or the ability to build-in the speakers and you want very loud and clean, then I think horns are the way to go.
Infiniate baffle may be a contender as you can buy a number of high excursion 15" or 18" drivers, but you end up spending a lot of money on amplifiers and drivers and half the energy goes into the roof space - then you also need to consider noise reduction.
If you want 110 db at your seating position then it is hard to go past horns, but if we are just considering accuracy I think dipole bass is without equal.
Ultimately I would like to build a home theatre room with a large dipole array either side of a large screen crossing over at 100 Hz to a pair of very large built-in bass horns to produce 120 db at all seating positions. I also plan to build a music only system in a living room using full range dipoles similar to Linkwitz Phoenix or Orion.
Magnetar said:
I'm trying to get my head around this ... "dipole isobarik horns"Let me see if I understand ... as I am confused by the use of "isobarik" in this context. Essentially you have two front loaded horns back to back with the rear of the drivers in a small sealed enclosure. They are wired out of phase so that while one cone travels out of the magnet, the other moves in. Is this a bass horn? What size is it and what is the bandwidth?
I'm familiar with the idea of cancelling even order harmonic distortion in this way as Linkwitz does in his dipole woofers. However, I'm not convinced that this type of distortion is critical. There is research to show that distortion perception is related to to the nature of the distortion more than its level as measured by THD%.
Konnichiwa,
I have no links handy, however a simple indication are the often published SPL Curves for Pro-Speakers within which some manufacturers include 2nd & 3rd Harmonic plots. You can regulary see the 2nd harmonic rising up strongly with falling frequency, often also 3rd harmonic. And or course, falling frequency with a given input voltage means more excursion.
HOWEVER, in a low frequency system that is used LF ONLY (meaning a fairly low cutoff) distortion is fairly uncritical due to the insensitivity of the ear at low frequencies.
Depends. If you require very large SPL's in very large rooms (which means room effects are lessened) horns are the better solution.
If you require moderate realistic SPL's (eg 86db with 20db crest factor) in a comparably small room (which means room effects are pronounced) you are better off with dipoles.
So, for the palatial mansions of the elite in imperial america clearly horns, for the small rooms found in Europe and among the less privileged city dwellers in the empire dipoles.
Sayonara
rick57 said:
I have no links handy, however a simple indication are the often published SPL Curves for Pro-Speakers within which some manufacturers include 2nd & 3rd Harmonic plots. You can regulary see the 2nd harmonic rising up strongly with falling frequency, often also 3rd harmonic. And or course, falling frequency with a given input voltage means more excursion.
HOWEVER, in a low frequency system that is used LF ONLY (meaning a fairly low cutoff) distortion is fairly uncritical due to the insensitivity of the ear at low frequencies.
rick57 said:
Depends. If you require very large SPL's in very large rooms (which means room effects are lessened) horns are the better solution.
If you require moderate realistic SPL's (eg 86db with 20db crest factor) in a comparably small room (which means room effects are pronounced) you are better off with dipoles.
So, for the palatial mansions of the elite in imperial america clearly horns, for the small rooms found in Europe and among the less privileged city dwellers in the empire dipoles.
Sayonara
Konnichiwa,
In smallish rooms, anyway.
Actually, there is something that DOES beat dipole bass. Namely "unipole" bass.
The trick is to remember that room modes disappear once the room becomes smaller than 1/2 wavelength and become reduced in magnitude once the room dimensions are fractions of the wavelength. In my 4.5 X 5.5 X 2.4m room this is at 32Hz/64Hz.
If I now combine a Dipole upper bass with a sealed lower bass system crossed over at (say) 50hz (-6db) with 3rd order slopes each (the HP on the upper bass can be the natural driver and dipole rolloff if designed well) we will have a radiation pattern that will at the crossover frequency be cardiodic, ideally with no rear output. One octave below the crossover frequency (at 25Hz) our radiation will be omnidirectional, however we are now below the rooms modal range and actually require just pressure excitation to "drive" the room. One otave above the crossover frequency (at 100Hz) our radiation will be fully dipolar, exactly where we need it as room modes are at the maximum. And between 25Hz and 100Hz our radiation pattern will slowly transit from omni vai cardiod to dipolar.
Hence combining a small physical size "ELF Mode" active subwoofer with a suitable limited range Fullrange/Upper LF Dipole system yields the best oif all worlds, serious pressurisation of the room in the rooms pressure mode (and for home theather "Impact"), clean and tactile low notes from instruments that require good transient response but lack extremely low notes (Bass, Piano, Drums). It also makes for a compact system that is very "wife friendly" if doen right.
I am running something like that now, with a pair of 8" Fullranger on acrylic baffles and a pair of REL Q-Bass Subs together. The SPL's in my room suffice (just about, really big orchestral stuff could use a few more db of clean SPL - we all have to make sacrifices in a marriage) and the sound is the best I ever had in this room, not just to my own views....
Sayonara
paulspencer said:
In smallish rooms, anyway.
Actually, there is something that DOES beat dipole bass. Namely "unipole" bass.
The trick is to remember that room modes disappear once the room becomes smaller than 1/2 wavelength and become reduced in magnitude once the room dimensions are fractions of the wavelength. In my 4.5 X 5.5 X 2.4m room this is at 32Hz/64Hz.
If I now combine a Dipole upper bass with a sealed lower bass system crossed over at (say) 50hz (-6db) with 3rd order slopes each (the HP on the upper bass can be the natural driver and dipole rolloff if designed well) we will have a radiation pattern that will at the crossover frequency be cardiodic, ideally with no rear output. One octave below the crossover frequency (at 25Hz) our radiation will be omnidirectional, however we are now below the rooms modal range and actually require just pressure excitation to "drive" the room. One otave above the crossover frequency (at 100Hz) our radiation will be fully dipolar, exactly where we need it as room modes are at the maximum. And between 25Hz and 100Hz our radiation pattern will slowly transit from omni vai cardiod to dipolar.
Hence combining a small physical size "ELF Mode" active subwoofer with a suitable limited range Fullrange/Upper LF Dipole system yields the best oif all worlds, serious pressurisation of the room in the rooms pressure mode (and for home theather "Impact"), clean and tactile low notes from instruments that require good transient response but lack extremely low notes (Bass, Piano, Drums). It also makes for a compact system that is very "wife friendly" if doen right.
I am running something like that now, with a pair of 8" Fullranger on acrylic baffles and a pair of REL Q-Bass Subs together. The SPL's in my room suffice (just about, really big orchestral stuff could use a few more db of clean SPL - we all have to make sacrifices in a marriage) and the sound is the best I ever had in this room, not just to my own views....
Sayonara
paulspencer said:
88db/W/m + 1000W < 108db/W/m + 10W
The 88db is a guess - what is the efficiency of the dipole? (not in the middle of its passband - if you are EQing to flatten the response the true efficiency is the lowest level of efficiency in the passband.)
There are some differences impossible to compensate with a bigger amplifier. I suppose you can keep adding drivers, but then size starts to become a factor.
I wont accept that horns are automatically inferior to a dipole with regards to ultimate fidelity. Microscopically few people have heard anything but seriously compromised designs when it comes to horns and bass horns in particular. A full-size bass horn designed for half space radiation and a 50Hz cutoff should have a mouth size of roughly 4 square metres! If it sits on the floor (quarter space) you can get away with 1 square metre. Anything smaller is a significant compromise and this is just for 50Hz reproduction.
Sorry to beat the drum so loudly here, but most people associate poor fidelity with horns because of hearsay and bad PA.
Konnichiwa,
Hmm. I know of no horn that is of dimensions acceptable even in large rooms that provides 108db/W/m at 20Hz. Hence, rather than making unrealistic numbers up, let's get real.
If we take both horns and dipoles for a given size/cost we can discuss sensitivity.
Let's a take a folded (W) dipole 35" high and 20" wide and deep with 4pcs of moderatly inexpensive 15" LF drivers (say Eminence Beta 15) and a more or less equal driver investment in Horns, say the Labhorn (which is much larger BTW).
The labhorn was measured as 94db @ 30Hz and 97db @ 50Hz for one electrical watt input. The proposed dipole (which is more compact) will produce around 85db @ 30Hz and 96db @ 50Hz for one electrical watt input. Below 30Hz either system's output drops like a stone, the Labhorn is 76db/1W/1m @ 20Hz and the proposed dipole 72db/1W/1m @ 20Hz, so either would need ton's of EQ to get usefull output at 20Hz.
The disparity at 30Hz is 9db and at 50Hz it more or less disappears and going very low the horn again looses it's lead as it becomes too small. No doubt, the much larger labhorn will play much louder at 30Hz and probably also at 50Hz and 20Hz, but I suspect either system will give enough clean SPL in normal rooms for music, if combined with a powerfull enough Amp. The main difference will be the modal interactions with the room in my view.
If I take the original Labhorn Size and keep my original proposed dipoles but double them up the difference between Labhorn and 8pcs Beta 15 in dipoles drops to 6db at 30Hz and if drop another dipole on top to claim the same sort of volume I get the difference down to maybe 4db.
We did this "horn volume equvalent with conventional boxes" comparison during my Pro-Sound days. A massive Hornbased PA was compared to massive stacks of inexpensive 3-way systems (eg 15/3). On pure SPL the same Volume of 3-Way boxes with much more drivers and more power applied than the Horn system was well ahead, but it's cost was higher and intelligibility and "throw" was worse. Now in a Pro application this matters but at home?
A correctly implemented horn will show a fidelity similar to that of a dipole, however it will be a HUGE structure. Foreshortened Horns are demonstrably inferior in transient response and LF smoothness. At least in technical terms it makes them inferior, but admittedly, they are "poor horns".
Sayonara
jeff mai said:
Hmm. I know of no horn that is of dimensions acceptable even in large rooms that provides 108db/W/m at 20Hz. Hence, rather than making unrealistic numbers up, let's get real.
If we take both horns and dipoles for a given size/cost we can discuss sensitivity.
Let's a take a folded (W) dipole 35" high and 20" wide and deep with 4pcs of moderatly inexpensive 15" LF drivers (say Eminence Beta 15) and a more or less equal driver investment in Horns, say the Labhorn (which is much larger BTW).
The labhorn was measured as 94db @ 30Hz and 97db @ 50Hz for one electrical watt input. The proposed dipole (which is more compact) will produce around 85db @ 30Hz and 96db @ 50Hz for one electrical watt input. Below 30Hz either system's output drops like a stone, the Labhorn is 76db/1W/1m @ 20Hz and the proposed dipole 72db/1W/1m @ 20Hz, so either would need ton's of EQ to get usefull output at 20Hz.
The disparity at 30Hz is 9db and at 50Hz it more or less disappears and going very low the horn again looses it's lead as it becomes too small. No doubt, the much larger labhorn will play much louder at 30Hz and probably also at 50Hz and 20Hz, but I suspect either system will give enough clean SPL in normal rooms for music, if combined with a powerfull enough Amp. The main difference will be the modal interactions with the room in my view.
jeff mai said:
If I take the original Labhorn Size and keep my original proposed dipoles but double them up the difference between Labhorn and 8pcs Beta 15 in dipoles drops to 6db at 30Hz and if drop another dipole on top to claim the same sort of volume I get the difference down to maybe 4db.
We did this "horn volume equvalent with conventional boxes" comparison during my Pro-Sound days. A massive Hornbased PA was compared to massive stacks of inexpensive 3-way systems (eg 15/3). On pure SPL the same Volume of 3-Way boxes with much more drivers and more power applied than the Horn system was well ahead, but it's cost was higher and intelligibility and "throw" was worse. Now in a Pro application this matters but at home?
jeff mai said:
A correctly implemented horn will show a fidelity similar to that of a dipole, however it will be a HUGE structure. Foreshortened Horns are demonstrably inferior in transient response and LF smoothness. At least in technical terms it makes them inferior, but admittedly, they are "poor horns".
Sayonara
Kuei Yang Wang said:
These measurements show that the Labhorn is not a horn at these frequencies. The photo you posted earlier with the horn built into the wall would likely approach the 108db/w/m figure at 50Hz (but maybe not at 30Hz.)
Kuei Yang Wang said:
I'd argue that "similar" is being rather kind to the dipole, but other than that you are making the same point I made: there is nothing inherently wrong with horns until you begin compromising.
Re: isobaric
Here I used two JBL 2220b Alnico 15" bass drivers both mounted forward, front driver loaded into the horn and rear driver mounted in to the rear sealed compression driver (1/2 volume) but exposed to rear. The horn is a 60 Hz expo flare, sand filled. They were used 50 to 200 cycles but actually had usable bandwith to 800 Hz. 16 ohm drivers in push pull isobaric wired in parallel. Measured in-room sensitivity with 2.83 volts was 107 db at five feet. I have since replaced the dual drive with one Altec 921 8 ohm driver -- The dual drive was very good sounding BUT there was a problem in bass imaging due to the back drivers output. The new Altec driver also has less power compression and is just as detailed as the two isobaric drivers. So a single 15" Altec is what I prefer.
If both drivers were horn loaded the bass horn would be 2 meters deep. I really doubt it would sound as good as the way I have it now -- plus they already weigh around 350 lbs each - if the horn was double at 700 lbs a side it would be like my sub horns and require disassembly to move.
For subs I use three modified MGA (same as used in the Sensurround movies in real theaters) subhorns loaded with high efficiency 18" drivers mounted to concrete. It covers the whole front wall of the listening room and is a semi-permanent beast. One watt sensitivity here is a whopping 110 db at the listening position sixteen feet away from them at 20 Hz with usable response below 10 cycles.
In the picture below you can see the subhorns better. Here I used compression drivers from 120 cycles up and was using the two outside subhorns in stereo from 120 down and the center horn up to 35 cycles. The delay between the satellite and the subs was clearly audible and I do not like the sound of the digital delays I've tried- so I now cross over much lower to the above satellite/bass horn system and run the three subhorns in mono..
Coolin said:
Here I used two JBL 2220b Alnico 15" bass drivers both mounted forward, front driver loaded into the horn and rear driver mounted in to the rear sealed compression driver (1/2 volume) but exposed to rear. The horn is a 60 Hz expo flare, sand filled. They were used 50 to 200 cycles but actually had usable bandwith to 800 Hz. 16 ohm drivers in push pull isobaric wired in parallel. Measured in-room sensitivity with 2.83 volts was 107 db at five feet. I have since replaced the dual drive with one Altec 921 8 ohm driver -- The dual drive was very good sounding BUT there was a problem in bass imaging due to the back drivers output. The new Altec driver also has less power compression and is just as detailed as the two isobaric drivers. So a single 15" Altec is what I prefer.
If both drivers were horn loaded the bass horn would be 2 meters deep. I really doubt it would sound as good as the way I have it now -- plus they already weigh around 350 lbs each - if the horn was double at 700 lbs a side it would be like my sub horns and require disassembly to move.
An externally hosted image should be here but it was not working when we last tested it.
For subs I use three modified MGA (same as used in the Sensurround movies in real theaters) subhorns loaded with high efficiency 18" drivers mounted to concrete. It covers the whole front wall of the listening room and is a semi-permanent beast. One watt sensitivity here is a whopping 110 db at the listening position sixteen feet away from them at 20 Hz with usable response below 10 cycles.
In the picture below you can see the subhorns better. Here I used compression drivers from 120 cycles up and was using the two outside subhorns in stereo from 120 down and the center horn up to 35 cycles. The delay between the satellite and the subs was clearly audible and I do not like the sound of the digital delays I've tried- so I now cross over much lower to the above satellite/bass horn system and run the three subhorns in mono..
An externally hosted image should be here but it was not working when we last tested it.
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