Yep, confused thinking of sensitivity vs. SPL(max). I always mix that up. Note to self: 3dB increase, 3dB increase, 3dB inc...
Another way of explaining it: the radiator surface doubles. And as acoustical power is directly proportionate to volume displacement, acoustical power doubles. Hence SPL increases another 3dB, totaling 6dB gain for a 3dB increase in electrical power.
Another way of explaining it: the radiator surface doubles. And as acoustical power is directly proportionate to volume displacement, acoustical power doubles. Hence SPL increases another 3dB, totaling 6dB gain for a 3dB increase in electrical power.
Let me get this straight: presumably this is the same principle whereby larger diameter drivers generally have higher sensitivities than their smaller cousins in the same product line? And this has to do with efficiency of coupling to the air, correct? So for horn loading presumably you would not get that extra 3 dB from doubling the number of drivers, since a properly designed horn optimizes the driver coupling to the air.
Another question: A horn can have lower distortion (for the same driver, SPL and Hz) solely because driver excursion is greatly reduced, or are there other reasons as well?
Another question: A horn can have lower distortion (for the same driver, SPL and Hz) solely because driver excursion is greatly reduced, or are there other reasons as well?
myyykmeister said:Let me get this straight: presumably this is the same principle whereby larger diameter drivers generally have higher sensitivities than their smaller cousins in the same product line? And this has to do with efficiency of coupling to the air, correct? So for horn loading presumably you would not get that extra 3 dB from doubling the number of drivers, since a properly designed horn optimizes the driver coupling to the air.
Another question: A horn can have lower distortion (for the same driver, SPL and Hz) solely because driver excursion is greatly reduced, or are there other reasons as well?
The increased efficiency is due to higher radiation resistance, in other words better matching between the heavy diaphragm and light air. Horn loading increase efficiency by improving this matching.
A properly designed full-size horn can have efficiency in the 30-60% range (in the bass and midrange region below the mass rolloff frequency), in this case doubling the number of cabinets doesn't increase efficiency any further.
Most bass horns are considerably smaller than the size for optimum efficiency, so stacking cabinets does increase efficiency though not necessarily by 3dB per doubling.
Horn distortion is lower because driver excursion is greatly reduced; for a given SPL the higher efficiency also means much lower power dissipation which also reduces thermal compression.
Ian
don't know if it'll bring anything ..
but i have already made 16 15" wood bucks
to install in the front wall of my new house home theater ...
will probably be using 16 servo controlled 15" woofers from our friend at Rythmik audio ... i want to test 1-2 with their amp before i invest ..but from what i've read
this is a somewhat expensive setup ..but i am sure that it will get to the quality/spl i desire with this!
there is no second chances in my case
so while you could decrease the number of drivers,
to use a few of them as was mentionned earlier,
sounds like a better way to achieve all of your goals
( mine will be all IB with a rear chamber ported to the garage room ... you mentionned IB also i believe! )
my 2 cents
but i have already made 16 15" wood bucks
to install in the front wall of my new house home theater ...
will probably be using 16 servo controlled 15" woofers from our friend at Rythmik audio ... i want to test 1-2 with their amp before i invest ..but from what i've read
this is a somewhat expensive setup ..but i am sure that it will get to the quality/spl i desire with this!
there is no second chances in my case
so while you could decrease the number of drivers,
to use a few of them as was mentionned earlier,
sounds like a better way to achieve all of your goals
( mine will be all IB with a rear chamber ported to the garage room ... you mentionned IB also i believe! )
my 2 cents
Thanks, Ian,
That makes sense. Also I hadn't thought about the power compression angle.
So with the 3 dB extra increase by doubling of direct radiators, is there an optimum spacing between drivers that allows them to maximally involve as much air as possible, without being so far apart that they don't work together? And of course there would be narrowing of the radiation into a beam due to wider source, dropping in frequency as the baffle is widened...
Thanks!
That makes sense. Also I hadn't thought about the power compression angle.
So with the 3 dB extra increase by doubling of direct radiators, is there an optimum spacing between drivers that allows them to maximally involve as much air as possible, without being so far apart that they don't work together? And of course there would be narrowing of the radiation into a beam due to wider source, dropping in frequency as the baffle is widened...
Thanks!
One problem with horn subwoofers is that the long path means that you either delay the main speakers, or live with the out-of-phase response difference between the subwoofer and main speakers. Either way, horns are NOT a low distortion option.
Also horn subwoofers still do have compression issues and reflected sound from the box reradiated back through the cone because the compression chambers. Thus, infinate baffle arrangements are lower distortion systems, provided that you have a sufficient number of drivers to keep excursion down.
Finally, if you value deep response (after all, you asked about subwoofers), horn subwoofers cannot hold a candle compared to infinite baffle systems.
Retsel
Also horn subwoofers still do have compression issues and reflected sound from the box reradiated back through the cone because the compression chambers. Thus, infinate baffle arrangements are lower distortion systems, provided that you have a sufficient number of drivers to keep excursion down.
Finally, if you value deep response (after all, you asked about subwoofers), horn subwoofers cannot hold a candle compared to infinite baffle systems.
Retsel
Hi Retsel,
The phenomenon you are describing is called group delay, which is not inherently a form of signal distortion in itself. It's a bad crossover (one that doesn't account for the delay) that distorts the resulting amplitude and phase response of the system. I agree that long path lengths call for a dedicated delay, so what?
What's the deal with delaying the main speakers? We're talking about the low milliseconds range here. Even a DJ or musician performing live wouldn't get harmed by this common practice applied to their monitoring speakers.
This is an unfortunate generalization, I'm afraid.
Of course horns have compression, that's a regular design element: the compression chamber. Please note that the term compression doesn't relate to distorted sound, but a transformation process between air velocity and air pressure. This design element, depending on design compromises, can introduce distortion. But a good design (or one entirely without compression, a wave guide) doesn't.
Of course horns experience reflected sound from the box reradiated back through the cone, every speaker enclosure has this phenomenon. It's not a matter of horns in general, but a question of what you do with the back of the driver.
I agree that not-so-well thought out horn constructions can distort severely. But that's not implying the inverse argument.
While this sounds like a conclusion (due to the use of 'thus'), it actually is a claim on it's own that doesn't relate to the points above... 
But now that we're at it: we've had closed, vented, horn and tapped horn simulations in this thread, why don't you come up with an infinite baffle design for an 18" pro woofer that delivers very low distortion at competing output SPL?
Uuuh! You've obviously had contact with too many bad horns (or bad horn applications). Many others have listening experience with good bass horns (preferrably in stacks).
BTW, that's another claim being made! Are 'infinite baffles' really infinite? Are real world horns of infinite mouth size? Well, you get my point... It's all about the application. A good sub-bass horn (arrangement) cannot be small, neither can a good infinite baffle for sub-bass use.
Cheers,
Sebastian.
Retsel said:
The phenomenon you are describing is called group delay, which is not inherently a form of signal distortion in itself. It's a bad crossover (one that doesn't account for the delay) that distorts the resulting amplitude and phase response of the system. I agree that long path lengths call for a dedicated delay, so what?
What's the deal with delaying the main speakers? We're talking about the low milliseconds range here. Even a DJ or musician performing live wouldn't get harmed by this common practice applied to their monitoring speakers.
This is an unfortunate generalization, I'm afraid.
Of course horns have compression, that's a regular design element: the compression chamber. Please note that the term compression doesn't relate to distorted sound, but a transformation process between air velocity and air pressure. This design element, depending on design compromises, can introduce distortion. But a good design (or one entirely without compression, a wave guide) doesn't.
Of course horns experience reflected sound from the box reradiated back through the cone, every speaker enclosure has this phenomenon. It's not a matter of horns in general, but a question of what you do with the back of the driver.
I agree that not-so-well thought out horn constructions can distort severely. But that's not implying the inverse argument.
While this sounds like a conclusion (due to the use of 'thus'
), it actually is a claim on it's own that doesn't relate to the points above... But now that we're at it: we've had closed, vented, horn and tapped horn simulations in this thread, why don't you come up with an infinite baffle design for an 18" pro woofer that delivers very low distortion at competing output SPL?
Uuuh! You've obviously had contact with too many bad horns (or bad horn applications). Many others have listening experience with good bass horns (preferrably in stacks).
BTW, that's another claim being made!
Are 'infinite baffles' really infinite? Are real world horns of infinite mouth size? Well, you get my point... It's all about the application. A good sub-bass horn (arrangement) cannot be small, neither can a good infinite baffle for sub-bass use.Cheers,
Sebastian.
sek said:Uuuh! You've obviously had contact with too many bad horns (or bad horn applications). Many others have listening experience with good bass horns (preferrably in stacks).
BTW, that's another claim being made!
Cheers,
Sebastian. [/B]
One thing for sure is that it's far easier to use an IB for other purposes. It seem much more difficult to setup shop, closet, garage or storage space inside a sub-bass horn. I'm sure it can be done though!
'Sorry Honey, we'll have to move the cars if you want to watch that movie tonight. They're choking the horn!'
Hehe,
honestly, I'm just defending the concept of horns/waveguides against false generalization. Nobody said they are the optimal choice for HT. I myself wouldn't want a stack of, say, 40 sq ft (times two) in my living room or home theater.
But I wouldn't want to have to cut a hole into every concert hall or club I'm partying in, too.
To rephrase it: "Yes honey, the kids have to wear that hearing protection while playing in their room. I told you we can't use the attic for the IB."
honestly, I'm just defending the concept of horns/waveguides against false generalization. Nobody said they are the optimal choice for HT. I myself wouldn't want a stack of, say, 40 sq ft (times two) in my living room or home theater.
But I wouldn't want to have to cut a hole into every concert hall or club I'm partying in, too.
To rephrase it: "Yes honey, the kids have to wear that hearing protection while playing in their room. I told you we can't use the attic for the IB."
Every enclosure type can be made to play in the bass area. Its just a matter of how you design it. No type is inherently flawed, they are just different approaches to the same goal, which may have different optimums concerning the criteria price, volume, maximum output etc. or combinations of those like max.spl vs price. All can be low or high in distortion, it just depends on the designers choice how to do things.
sek said:
Hi there sek,
Just wondering, how did you get those numbers, even via simulation? I have plugged quite a number of prosound woofers into WinISD, and I nearly ended with the BMS 18N850v2 or B&C 18TBX100 as they could be gotten cheap locally for a pair. Only reasonably high level distortion levels can be obtained from specsheet for BMS/JBL, low level from Beyma.....
Eg, 18W1300 is a very sensitive driver (low MMs, not sure how it behaves at high SPLs), force tune it to 20Hz port and 200L enclosure and I get 115dB for 30-40Hz. Its not an optimum design for SPLs but you do dig low (114dB for 20Hz).
You do get 119-123dB for a 200L and 34Hz high tune for 30-40Hz.
This is without power compression.
In the end I ended with the TH-112 tapped horn. For DSL this is good revenue, average 12" driver, technically easy box design (at least for them), and good performance/fidelity even for audiophile use.
I don't have the skills to DIY my boxes so its prob ard usd500 for a big vented box properly braced and veneered. So if i DIY 2x18" good pro drivers for direct radiating apps it won't be so cost effective.
The TH-112 is about 300L and 30" depth (!), but I guess its easier to place 2 x 180L cabs. At about 1.8k usd and shipping is crazy low even to my place halfway round the world, as DSL probably has corporate account (I used Bax Global/Schekner).
Here's some measurement data for pro cabs (they have TH-115 in there).
http://srforums.prosoundweb.com/index.php/mv/msg/28422/0/16/0/
Seriously if the tuning is so high, its imperative to have a HP filter to cut below tuning, else you will get 20Hz or infrasonics but also lots of distortion at high SPLs.
For those aiming to dig low be it for music or HT, can try
www.acoupower.com
Literally no power compression unless its continuous drone at high levels (eg electronica).
Maybe there's a misunderstanding about my numbers. Maybe I just didn't express it clear enough.
You confirmed that your WinISD sims showed above 125dB below 40Hz. You mentioned 123dB at 34Hz for a single driver, my simulations took two drivers into account.
But by 'accepting an LT down to 20Hz' I didn't mean a 20Hz -3dB alignment, but a pole in the Linkwitz transform at that frequency. That's not the same thing.
Take a look at and around Post #70 for the numbers and the simulations. The closed box gets an LT and an additional high pass filter applied.
In this configuration - while not arriving at the same SPL(max) like in a vented configuration - the box can still take an all day beating at full power without failing due to overexcursion.
2100 said:
Exactly. All the simulations I posted contain a 24dB/Oct. HP filter in the response. I think I mentioned this before.
Hope this helps,
Sebastian.
sek said:You confirmed that your WinISD sims showed above 125dB below 40Hz. You mentioned 123dB at 34Hz for a single driver, my simulations took two drivers into account.
But by 'accepting an LT down to 20Hz' I didn't mean a 20Hz -3dB alignment, but a pole in the Linkwitz transform at that frequency. That's not the same thing.
[/B]
1. Oh I see. If we add say 6dB that would be pretty close. I'm not really concerned with super exact figures, but at least they must not be too far off.
And anyway, you did say peak figures and assuming no power compression, so I guess we are there around there.
2. Yes, I assumed LT down to 20Hz, or more generally any EQ (PEQ or GEQ or whatever). But that I think that's not really the territory of such drivers as the eff will be pretty low, even with the help of the box/tune.
That said, the 18N860 looks great. But sensitivity is only approx 92-93dB simulated (check out 1W SPL). I could get the Acoupower 18" and not loose a lot of sensitivity, but problem is that the port is too big too long to avoid chuffing, thus needing the use of PRs or a super big box. But if one does have a super amp like some of the powersoft or 3U monsters (but in 110Vac service it is usually electrically limited), and the room can take a big box, do check out the Acoupower 18, now that the LMS-5400 is not so easily available.
2100 said:
Power compression sets in with rising voice coil temperature. This usually starts to matter after something between a couple of hundred milliseconds to a couple of seconds, depending on coil temperature prior to the power peak. So for a 'true' (thermal) peak, (thermal) power compression doesn't play a major role unless the speaker was at it's thermal RMS limit anyway.
2100 said:
Yep, but a lot of money.
Cheers,
Sebastian.
sek said:
Power compression sets in with rising voice coil temperature. This usually starts to matter after something between a couple of hundred milliseconds to a couple of seconds, depending on coil temperature prior to the power peak. So for a 'true' (thermal) peak, (thermal) power compression doesn't play a major role unless the speaker was at it's thermal RMS limit anyway.
Yep, but a lot of money.
Cheers,
Sebastian.
Well, yeah, one tends to loose anything from 0.x dB to as much as a couple of dBs. 18sound actually lists -10db, -3 and 0dB specs, cool!
The Acoupowers with the fan-like airflow from the pole piece vent 6" VC and crazy heatsinking, can probably reasily take a couple seconds worth of explosion @ a couple of kW in HT program with negligible power compression.
I was quoted usd450 for 18N850v2 from usspeaker, you lucky soul in Germany can get it much cheaper and easier yeah!
What I said:
"Also horn subwoofers still do have compression issues and reflected sound from the box reradiated back through the cone because the compression chambers."
What you said
"This is an unfortunate generalization, I'm afraid.
Of course horns have compression, that's a regular design element: the compression chamber. Please note that the term compression doesn't relate to distorted sound, but a transformation process between air velocity and air pressure. This design element, depending on design compromises, can introduce distortion. But a good design (or one entirely without compression, a wave guide) doesn't.
Of course horns experience reflected sound from the box reradiated back through the cone, every speaker enclosure has this phenomenon. It's not a matter of horns in general, but a question of what you do with the back of the driver.
I agree that not-so-well thought out horn constructions can distort severely. But that's not implying the inverse argument."
My response:
I find it amazing that you can say something that counteracts your statement and then try to turn it around and use it to support your point of view. One important limitation to the quality of the sound from any subwoofer is compression. Compression is when the peaks of the sound is truncated, and it can mean that the driver is not tracking the sound, in that the driver is trailing the signal trying to be played. Thus the signal would dictate that a subwoofer driver respond to the signal being provided to it, but if there is a physical contraint, the driver will not respond correctly, hence distortion. That is what the compression chamber does to the sound of a horn subwoofer. This should be obvious just in theory. As the driver moves in response to a signal, it creates a backpressure that serves to limit its travel.
However, I will provide you with some practical experience that I have had. I had my Lowther DX4s in backhorns (Hedlund Horns) for many years. I was amazed at the improvement in sound (lower distortion) caused by mounting the Lowthers in open baffle. The two most important differences in the design was that I got rid of the back chamber, which caused reflections back through the cone, and it reduced the "compression" caused by the compression chamber. Thus, while you have succumbed to the dogma about horns, they have their inherent limits.
Infinfite baffle systems vent their backwave into such large spaces, that compression is avoided and much of the backwave energy is dissipated. Hence infinite baffle systems are potentially inherently better. Plus IB systems are very efficient down low, which is desirable in subwoofers. provided that your room can handle it...
I am not saying that horn systems don't sound good. They can, particularly if you need to provide sound to an auditorium. But for lowest distortion sound, IB systems, if designed adequately, are inherently better, if you have a room or space that you can vent the backwave into.
If you don't believe me, go to the IB webpage and people repeatiely call the IB systems the best bass that they have ever heard. Don't you think that those people have heard horn subwoofers?
Also, I have heard Bruce Edgar's Seismic subs, a couple of times, but I was not impressed. However, many have said that it was the best bass that they have heard. I think that people have a very low bar when it comes to deep bass, and small box sealed subwoofers that they have heard sound really, really bad, which is why horn bass sounds good to them.
Retsel
"Also horn subwoofers still do have compression issues and reflected sound from the box reradiated back through the cone because the compression chambers."
What you said
"This is an unfortunate generalization, I'm afraid.
Of course horns have compression, that's a regular design element: the compression chamber. Please note that the term compression doesn't relate to distorted sound, but a transformation process between air velocity and air pressure. This design element, depending on design compromises, can introduce distortion. But a good design (or one entirely without compression, a wave guide) doesn't.
Of course horns experience reflected sound from the box reradiated back through the cone, every speaker enclosure has this phenomenon. It's not a matter of horns in general, but a question of what you do with the back of the driver.
I agree that not-so-well thought out horn constructions can distort severely. But that's not implying the inverse argument."
My response:
I find it amazing that you can say something that counteracts your statement and then try to turn it around and use it to support your point of view. One important limitation to the quality of the sound from any subwoofer is compression. Compression is when the peaks of the sound is truncated, and it can mean that the driver is not tracking the sound, in that the driver is trailing the signal trying to be played. Thus the signal would dictate that a subwoofer driver respond to the signal being provided to it, but if there is a physical contraint, the driver will not respond correctly, hence distortion. That is what the compression chamber does to the sound of a horn subwoofer. This should be obvious just in theory. As the driver moves in response to a signal, it creates a backpressure that serves to limit its travel.
However, I will provide you with some practical experience that I have had. I had my Lowther DX4s in backhorns (Hedlund Horns) for many years. I was amazed at the improvement in sound (lower distortion) caused by mounting the Lowthers in open baffle. The two most important differences in the design was that I got rid of the back chamber, which caused reflections back through the cone, and it reduced the "compression" caused by the compression chamber. Thus, while you have succumbed to the dogma about horns, they have their inherent limits.
Infinfite baffle systems vent their backwave into such large spaces, that compression is avoided and much of the backwave energy is dissipated. Hence infinite baffle systems are potentially inherently better. Plus IB systems are very efficient down low, which is desirable in subwoofers. provided that your room can handle it...
I am not saying that horn systems don't sound good. They can, particularly if you need to provide sound to an auditorium. But for lowest distortion sound, IB systems, if designed adequately, are inherently better, if you have a room or space that you can vent the backwave into.
If you don't believe me, go to the IB webpage and people repeatiely call the IB systems the best bass that they have ever heard. Don't you think that those people have heard horn subwoofers?
Also, I have heard Bruce Edgar's Seismic subs, a couple of times, but I was not impressed. However, many have said that it was the best bass that they have heard. I think that people have a very low bar when it comes to deep bass, and small box sealed subwoofers that they have heard sound really, really bad, which is why horn bass sounds good to them.
Retsel
Retsel said:
Please read and understand how a moving coil speaker (in any kind of enclosure) works before posting "facts" like this, your "logic" bears no resemblance to how a driver operates.
At bass frequencies the restoring force (due to "compression") from any air behind the cone has exactly the same effect as reduced suspension compliance (higher Fs), except that the force is more linear. There's no such thing as "truncating" the peaks of the sound, no extra "delay" due to the driver "failing to follow the signal", and no resulting distortion.
This applies in exactly the same way to horn and closed box speakers, the effect is just the same as a stiffer suspension -- the driver has a mass, a spring, damping, and a driving force, and behaves in a way described by standard equations of mechanics.
Ian
Hi Retsel,
you are suffering from a small misunderstanding there, concerning the term compression. Depending on the context it can have different usage. In music mastering, it is indeed a mechanism which raises the lower signals in comparison to the ones with higher volume and is a subtle kind of distortion. But in the context of horns, the term compression means something completely different. It indicates that the horn throat is smaller in area than the driver membrane - it has nothing to do with compression in a music mastering sense. Your error is to assume that the meaning of the word compression is allways the same. If you research more about horns, you will come to know these terms and such misunderstandings wont happen
you are suffering from a small misunderstanding there, concerning the term compression. Depending on the context it can have different usage. In music mastering, it is indeed a mechanism which raises the lower signals in comparison to the ones with higher volume and is a subtle kind of distortion. But in the context of horns, the term compression means something completely different. It indicates that the horn throat is smaller in area than the driver membrane - it has nothing to do with compression in a music mastering sense. Your error is to assume that the meaning of the word compression is allways the same. If you research more about horns, you will come to know these terms and such misunderstandings wont happen
Hi,
You can quote by checking the 'Quote' box just right of the bottom area of any post, or by using the 'Quote' button functionality in the 'Post Reply' form while editing.
I'll spare you with a comment on what I consider a slip - and attribute it to your misunderstanding of my explanation on compression.
What you describe is called limiting. Sound Compression is an influence gradually reducing the output of the transducer depending on the input signal exceeding a threshold. The concepts of compression and limitation are quite similar, but the difference is in the numbers: a compression is 'softer' and slower, a limiting action is 'harder' and faster.
Please note that the term is ambiguous and the meaning you referred to is not what I used to talk about. MaVo already pointed this out.
An example for sound compression is the thermally induced rise in voice coil temperature due to excess power consumption. The coil impedance rises and the current through the coil is reduced, resulting in less cone motion rise than expected. This process takes several signal periods to set in, gradually depends on actual temperature (change) and slowly resumes.
An example for limiting is the cone hitting the suspension after exceeding it's linear travel. The motion is truncated, stopping the cone in the middle of the signal period, but allowing the cone to travel back immediately after the signal allows re-entering the linear travel range. This process sets in instantaneously, does not depend on actual power or temperature and thus immediately stops after the suspension force manages to damp the cone back in place.
To respond to your statement above: No, a back chamber inherently forces neither on a cone. The back chamber increases the suspension stiffness (and coil impedance), but does not inherently prevent the cone from following the current through the voice coil. Ian already pointed this out. BTW, the canonical term for the chamber interacting with the cone in a physical way is loading.
Perhaps you imagine the backchamber as a source of sound waves retaliating back onto the cone, behaving all the more evil the smaller the chamber is? Well, let's just say that the size of the chamber would have no influence on this concept, only on the relevant frequencies. And what else than a large back chamber is the room on the other side of the baffle.
To make a long story short, the type of compression I (and others) talk about regarding horn construction is not the one similar to limiting, but the physical concept of trading pressure for velocity. The same thing that happens in your engine or your refridgerator.
The moving cone creates a pressure increase in the back chamber with backward-motion, and a pressure drop with forward-motion. This indeed serves to limit the travel, but that's not a bad thing. The chamber does not force the cone to inherently do bad things. An added volume is nothing that violates regular signal theory.
First off, when comparing IBs and horns, we cannot talk about backloaded horns (ever wondered what the term stands for?). Your example enclosure has no back chamber.
The chamber behind the Lowther driver is called the compression chamber. But for the reason given above: in order to increase pressure by reducing velocity.
Additionally, most designs for Lowther drivers intentionally factor distorion into the desired sound. I've read reports about the Lowther Acousta many years ago and learned how not to do it.
On top of that, an open baffle has no back chamber too - unlike the type of IB you're referring to.
And on another note, you deliver anecdotal proof to a claim. While I understand your point regarding your experience, I consider a backloaded Lowther horn the worst starting point for talking about quality bass horn applications.
No. The backwave energy is not neccessarily dissipated, just entering a larger chamber. This lowers the frequency of standing waves and modes remodulating the cone motion. As these modes now get into the range of bass frequencies, I can see no advantage to a small chamber with regard to 'tracking the sound'.
And we've already sorted that 'compression' doesn't occur. It's loading, which is not bad.
What are you trying to say here? To whom do you deliver sound with an IB?
Are you referring to 'auditorium' like in venue? If so, why that? I have never stated that I limit my view (or the explanations I tried to give) to a certain size (of auditorium) or amount (of listeners). The principles of sound radiation don't depend on room size or the number of ears in it.
That's a self fulfilling prophecy.
If you - for whatever architectural or accidental reason - have a complete room to spare in your house, an IB is your best option to make efficient use of it in terms of an acoustic chamber.
But why is that to say that planning a horn in the same volume to begin with couldn't have yielded similar response? I'm not arguing the beauty and simplicity of the concept of cutting a hole in the wall. But what about other approaches like, say, a perfect architectural prerequisite for fitting a huge horn? Wouldn't it then be the most efficient approach to ... well ... just fit a huge horn?
Just to give some food for thought: If an IB in the sense of a large chamber behind some transducers is your best option, what would happen with a huge horn connected between auditorium and chamber? Same idea goes for the reverse experiment of removing the back chamber of an infinitely sized front loaded horn (i.e. one making up a huge wall) ...
On a side note, I am not trying to be overly scientific here. But I have to question your almost inflational use of words like 'thus', 'this should be obvious', 'inherently' or alike. They don't prove a point. There's no use in calling a statement obvious while it is part of your argument...
Cheers,
Sebastian.
Retsel said:
You can quote by checking the 'Quote' box just right of the bottom area of any post, or by using the 'Quote' button functionality in the 'Post Reply' form while editing.
I'll spare you with a comment on what I consider a slip - and attribute it to your misunderstanding of my explanation on compression.
What you describe is called limiting. Sound Compression is an influence gradually reducing the output of the transducer depending on the input signal exceeding a threshold. The concepts of compression and limitation are quite similar, but the difference is in the numbers: a compression is 'softer' and slower, a limiting action is 'harder' and faster.
Please note that the term is ambiguous and the meaning you referred to is not what I used to talk about. MaVo already pointed this out.
An example for sound compression is the thermally induced rise in voice coil temperature due to excess power consumption. The coil impedance rises and the current through the coil is reduced, resulting in less cone motion rise than expected. This process takes several signal periods to set in, gradually depends on actual temperature (change) and slowly resumes.
An example for limiting is the cone hitting the suspension after exceeding it's linear travel. The motion is truncated, stopping the cone in the middle of the signal period, but allowing the cone to travel back immediately after the signal allows re-entering the linear travel range. This process sets in instantaneously, does not depend on actual power or temperature and thus immediately stops after the suspension force manages to damp the cone back in place.
To respond to your statement above: No, a back chamber inherently forces neither on a cone. The back chamber increases the suspension stiffness (and coil impedance), but does not inherently prevent the cone from following the current through the voice coil. Ian already pointed this out. BTW, the canonical term for the chamber interacting with the cone in a physical way is loading.
Perhaps you imagine the backchamber as a source of sound waves retaliating back onto the cone, behaving all the more evil the smaller the chamber is? Well, let's just say that the size of the chamber would have no influence on this concept, only on the relevant frequencies. And what else than a large back chamber is the room on the other side of the baffle.
To make a long story short, the type of compression I (and others) talk about regarding horn construction is not the one similar to limiting, but the physical concept of trading pressure for velocity. The same thing that happens in your engine or your refridgerator.
The moving cone creates a pressure increase in the back chamber with backward-motion, and a pressure drop with forward-motion. This indeed serves to limit the travel, but that's not a bad thing. The chamber does not force the cone to inherently do bad things. An added volume is nothing that violates regular signal theory.
First off, when comparing IBs and horns, we cannot talk about backloaded horns (ever wondered what the term stands for?). Your example enclosure has no back chamber.
The chamber behind the Lowther driver is called the compression chamber. But for the reason given above: in order to increase pressure by reducing velocity.
Additionally, most designs for Lowther drivers intentionally factor distorion into the desired sound. I've read reports about the Lowther Acousta many years ago and learned how not to do it.
On top of that, an open baffle has no back chamber too - unlike the type of IB you're referring to.
And on another note, you deliver anecdotal proof to a claim. While I understand your point regarding your experience, I consider a backloaded Lowther horn the worst starting point for talking about quality bass horn applications.
No. The backwave energy is not neccessarily dissipated, just entering a larger chamber. This lowers the frequency of standing waves and modes remodulating the cone motion. As these modes now get into the range of bass frequencies, I can see no advantage to a small chamber with regard to 'tracking the sound'.
And we've already sorted that 'compression' doesn't occur. It's loading, which is not bad.
What are you trying to say here? To whom do you deliver sound with an IB?
Are you referring to 'auditorium' like in venue? If so, why that? I have never stated that I limit my view (or the explanations I tried to give) to a certain size (of auditorium) or amount (of listeners). The principles of sound radiation don't depend on room size or the number of ears in it.
That's a self fulfilling prophecy.
If you - for whatever architectural or accidental reason - have a complete room to spare in your house, an IB is your best option to make efficient use of it in terms of an acoustic chamber.
But why is that to say that planning a horn in the same volume to begin with couldn't have yielded similar response? I'm not arguing the beauty and simplicity of the concept of cutting a hole in the wall. But what about other approaches like, say, a perfect architectural prerequisite for fitting a huge horn? Wouldn't it then be the most efficient approach to ... well ... just fit a huge horn?
Just to give some food for thought: If an IB in the sense of a large chamber behind some transducers is your best option, what would happen with a huge horn connected between auditorium and chamber? Same idea goes for the reverse experiment of removing the back chamber of an infinitely sized front loaded horn (i.e. one making up a huge wall) ...
On a side note, I am not trying to be overly scientific here. But I have to question your almost inflational use of words like 'thus', 'this should be obvious', 'inherently' or alike. They don't prove a point. There's no use in calling a statement obvious while it is part of your argument...
Cheers,
Sebastian.
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