Full Range IB System

[bobdehunt]

I have an idea for a wonderful sounding speaker project. This idea is purely hypothetical, because I do not have at the current time the money or space for this project, therefore we will imagine that I have infinite money and space (within reason). I want to build a line array infinite baffle speaker system. I am semi-new to audio (I've been doing research out of interest for about 3-4 years now), so please correct me if anything I say is wrong, and don't be afraid to tell me that my idea is horrible if it is. I think that in order for anyone to help answer my questions, I will have to fully explain my design. Below is an explanation of what I want to build.

The dimensions of the room are going to be 24'x16' with 9' ceilings. I believe that this is the ideal room size? The speakers will be built directly into the wall with the rear of the speakers in another room, or possibly even outside if I can think of a way to keep it out of the reach of weather and pests. I am planning on building two line array systems directly into the wall in front of the listening position. One to the left, and one to the right. There will be no curve to the line array systems (unless it significantly impacts the audio quality). I think a curve would defeat the purpose of a line array, causing the sound to bounce off the ceiling much more. Instead, I will be using a line of planar tweeters (which have good horizontal, but not vertical coverage). and two lines of mids. I know that planar tweeters have good sound and I want it to sound open despite fact that it's in a wall, so I believe that the planar tweeters will be the best option. I also am wondering how far up and down the line of speakers should reach? I'm thinking maybe a 1.5-3' off the floor and ceiling in order to limit the sound from bouncing off of those surfaces? I will be making IB subs as well, but I honestly don't even know where to start on the placement and number of those. I know the general rules of thumb, like don't add any an equal distance from two walls and to not add multiple subs in a symmetrical design, but the ideal placement alludes me. I would do the subwoofer crawl, but I am not sure how helpful that would be considering that the subwoofer I would be using would be placed into the wall. Below I have inserted a crude drawing of my design.

*note: This drawing in not drawn to scale. I also did not figure the angle at which the two front walls will meet. I will do that once I have a more concrete idea of where the seating position needs to be.

Thank you for taking the time to read this and hopefully answer some of these questions.


*As requested by Everett I have linked some possible drivers and crossovers

The possible tweeter: https://www.madisoundspeakerstore.com/ribbon-tweeters/raal-original-140-15d-ribbon-tweeter-with-amorphous-core/
I think by removing the deflector pads, it would eliminate the vertical spread, making this tweeter ideal.

The possible mid-range: http://www.audiotechnology.dk/iz.asp?id=4|a|935|||
This one isn't very concrete. I can't seem to find any super high end mid drivers. It seems that the companies that produce them like to keep it for themselves. I looked to see if I could get any ribbon mid-ranges and although they are sold, I think I will stick to the traditional mid-range speakers so I don't have to deal with a three-way system.

The possible, but unlikely crossover: https://www.parts-express.com/eminence-pxb2-1k6-2-way-speaker-crossover-board-1600-hz--290-634
I believe that the recommended crossover for the tweeters will be compatible with the mid drivers. I was unable to find any high quality crossovers though, so the one linked above will work, but I think I will eventually either make one or get one custom made if I am unable to make one. The tweeters recommended crossover is a 4th order L-R @ 1600 Hz.

 

[everettT]

What does your crossover look like? As for the planar mids you can still find a couple but BG is not in business any more and they were the go to. The system your talking about is an interesting project but if you don't link the drivers and proposed crossover I'm not sure many can comment

 

[bobdehunt]

What does your crossover look like? As for the planar mids you can still find a couple but BG is not in business any more and they were the go to. The system your talking about an interesting project but if you don't link the drivers and proposed crossover I'm not sure many can comment

I mostly just want to know if the concept itself is a good idea. Eventually I'd do research on the specific drivers and crossovers I'd use. I do suppose that linking those items would certainly help though, so I'll go ahead and do that.

 

[TheWarrior]

I mostly just want to know if the concept itself is a good idea. Eventually I'd do research on the specific drivers and crossovers I'd use.

Do you understand what a line array is?
Do you understand that the number of drivers needed to make a line turn your proposed idea into a $10k+ single speaker?
Do you know what 2nd order Butterworth means to a 4th order Linkwitz Riley topology?
Do you know what a series-parallel wiring scheme does to the overall impedance of loudspeaker?

You've got passion, great! But you might not realize how far you need to go to be capable of designing AND building such a loudspeaker. We can recommend great resources for you, but many will involve purchasing textbook sized literature like Vance Dickason's 'Loudspeaker Design Cookbook' and Floyd Toole's 'Sound Reproduction' both of which periodically receive updates in new edition's as technology changes.

It's kind of a red pill/blue pill situation, especially considering your proposed idea!

 

[Swerd]

As TheWarrior already said, you've got passion. But it takes more than that to actually build a good sounding speaker. A few comments:

• An infinite baffle (IB) speaker is said to work well for low frequency bass, although it isn't the only way to accomplish that. I've never heard one. The principles of making an IB sub woofer are probably not shared for, or needed by the higher frequencies. I don't believe an IB design does anything for all the other frequencies. As a result, a full-range IB system presents all the difficulties and disadvantages of an IB system without adding any benefit over a speaker in a more standard cabinet. Build an IB sub woofer or two, but keep the mid range and tweeter in moveable cabinets.
  
  
• The main disadvantage is you cannot move the speakers to different positions. You mentioned a 24'×16'×9' room, describing it as ideal. You haven't considered listening positions within the room – they also have a considerable effect. There is no one single ideal room. Ideal for one frequency range may not be ideal for others. I always expect to adjust speaker positions within a room to find a position that sounds good and is practical in a room that also contains other furniture.
  
  
• You can never easily move an IB system to a different room or another house.
  
  
• Any IB system that penetrates outer walls is likely to interfere with most efforts at home thermal insulation. Keep loudspeakers separate from heating and air conditioning efficiency. Frankly, I think that also applies to IB sub woofers. Any advantages of an IB sub woofer can't compete with the advantages of good insulation and moisture barrier on an outer wall.
  
  
• Your examples of a tweeter and mid range driver show that you are willing to throw money at a project to guarantee good results. This is common with eager beginners. I'm not sure what the price is for the mid range, but the tweeter is extremely expensive. I wouldn't know whether or not they would work well together without some testing. Also, if I understand correctly, a main feature of array designs is that multiple inexpensive drivers can sound as good as one expensive driver, if they are properly linked by a carefully designed crossover network. Using multiple expensive drivers is going to cost plenty, but may achieve little extra.
  
  
• Finally, it would be a shame to use any expensive drivers without a custom made crossover. Any off-the-shelf crossover cannot work well, unless you are extremely lucky. Why go to all the effort at designing and building an expensive speaker system while ignoring the major effect a good crossover will have?

 

[bobdehunt]

Do you understand what a line array is?
Do you understand that the number of drivers needed to make a line turn your proposed idea into a $10k+ single speaker?
Do you know what 2nd order Butterworth means to a 4th order Linkwitz Riley topology?
Do you know what a series-parallel wiring scheme does to the overall impedance of loudspeaker?

You've got passion, great! But you might not realize how far you need to go to be capable of designing AND building such a loudspeaker. We can recommend great resources for you, but many will involve purchasing textbook sized literature like Vance Dickason's 'Loudspeaker Design Cookbook' and Floyd Toole's 'Sound Reproduction' both of which periodically receive updates in new edition's as technology changes.

It's kind of a red pill/blue pill situation, especially considering your proposed idea!

I realize that the speaker system would be very pricey and complicated to build. This is just my dream idea. I am not very likely to ever build this, but I may build something similar one day with much cheaper materials and therefore a much cheaper cost. As for wiring the speakers, I think I have knowledge of series/parallel wiring. If I wanted to make a four Ohm system, with eight eight Ohm speakers, I'd wire four pairs of the speakers in parallel and then wire the pairs of speakers together in series? As for the crossovers, this is the first time I've honestly ever done any research about them, so I have no idea what a 2nd order Butterworth is to a fourth order Linkwits Riley, but I'm sure I'll do research in the future and find out what those are. As for the knowledge I need to build and design these speakers, I would gladly read a book or two. I enjoy learning about speakers and speaker technology. I've never really been interested in electrical components, but I know I will have to do research on those as well. Considering the very high price if I were to buy a speaker system similar in quality to the one that I proposed, all of this research would eventually be worth it in the end. Especially considering I have years to do so.

 

[bobdehunt]

As TheWarrior already said, you've got passion. But it takes more than that to actually build a good sounding speaker. A few comments:

• An infinite baffle (IB) speaker is said to work well for low frequency bass, although it isn't the only way to accomplish that. I've never heard one. The principles of making an IB sub woofer are probably not shared for, or needed by the higher frequencies. I don't believe an IB design does anything for all the other frequencies. As a result, a full-range IB system presents all the difficulties and disadvantages of an IB system without adding any benefit over a speaker in a more standard cabinet. Build an IB sub woofer or two, but keep the mid range and tweeter in moveable cabinets.
  
  
• The main disadvantage is you cannot move the speakers to different positions. You mentioned a 24'×16'×9' room, describing it as ideal. You haven't considered listening positions within the room – they also have a considerable effect. There is no one single ideal room. Ideal for one frequency range may not be ideal for others. I always expect to adjust speaker positions within a room to find a position that sounds good and is practical in a room that also contains other furniture.
  
  
• You can never easily move an IB system to a different room or another house.
  
  
• Any IB system that penetrates outer walls is likely to interfere with most efforts at home thermal insulation. Keep loudspeakers separate from heating and air conditioning efficiency. Frankly, I think that also applies to IB sub woofers. Any advantages of an IB sub woofer can't compete with the advantages of good insulation and moisture barrier on an outer wall.
  
  
• Your examples of a tweeter and mid range driver show that you are willing to throw money at a project to guarantee good results. This is common with eager beginners. I'm not sure what the price is for the mid range, but the tweeter is extremely expensive. I wouldn't know whether or not they would work well together without some testing. Also, if I understand correctly, a main feature of array designs is that multiple inexpensive drivers can sound as good as one expensive driver, if they are properly linked by a carefully designed crossover network. Using multiple expensive drivers is going to cost plenty, but may achieve little extra.
  
  
• Finally, it would be a shame to use any expensive drivers without a custom made crossover. Any off-the-shelf crossover cannot work well, unless you are extremely lucky. Why go to all the effort at designing and building an expensive speaker system while ignoring the major effect a good crossover will have?

I see what you're saying. If I ever did implement this type of project, which is pretty unlikely, I'm sure that I would experiment with different speaker types and systems first before ever putting all this effort into making this one. I think that an IB system would still benefit the mid-ranges at least a little because the waves coming off the back of the speaker wouldn't interfere with the waves in front. Or would the difference be so minimal that it wouldn't be worth it at all?

 

[TheWarrior]

Especially considering I have years to do so.

That is a fair guess as to how long you'll need! The books I mentioned are definitely worth a look, and I'm sure others can be named. The two I stated will teach you about the construction and design of passive loudspeakers, and how to objectively measure them and what roles the room plays in what you hear, and how to deal with it. Everything you need to get started!

It's an extraordinary amount of information to absorb, but it can lead to great things! Good luck!

 

[bobdehunt]

That is a fair guess as to how long you'll need! The books I mentioned are definitely worth a look, and I'm sure others can be named. The two I stated will teach you about the construction and design of passive loudspeakers, and how to objectively measure them and what roles the room plays in what you hear, and how to deal with it. Everything you need to get started!

It's an extraordinary amount of information to absorb, but it can lead to great things! Good luck!

-
Okay. Thank you. I will definitely give those books a look.

 

[Swerd]

… As for the crossovers, this is the first time I've honestly ever done any research about them, so I have no idea what a 2nd order Butterworth is to a fourth order Linkwits Riley, but I'm sure I'll do research in the future and find out what those are.

You absolutely must learn about crossovers to have a successful DIY speaker design. It is as important, if not more important, than the sound quality of the drivers you choose. You can make a good sounding speaker with an inexpensive woofer and tweeter if you build the proper sized cabinet and use a crossover that keeps the drivers operating within their pass bands where they perform well. Such a speaker will sound better than one with very expensive drivers and a poorly designed crossover. Don't even mention off-the-shelf crossovers.

Another book I would read is Speaker Building 201 by Ray Alden. In fact, I would read that first.

I think that an IB system would still benefit the mid-ranges at least a little because the waves coming off the back of the speaker wouldn't interfere with the waves in front. Or would the difference be so minimal that it wouldn't be worth it at all?

I wish I understood more about IB speakers to answer that question. I don't even know where you can read the basics about designing them. I suspect the business about back waves not interfering with the front waves may occur, but not to the extent that its noticeable.

The main reason why IB designs are used for bass frequencies is to gain the maximum loudness that comes when woofer cones are mounted congruent to a reflecting surface, like a wall. The sound from a wall mounted woofer propagates in a hemisphere, where the sound from a woofer mounted away from a wall propagates spherically – in all directions. The wall mounted woofer is about twice as loud.

This is most noticeable with bass frequencies whose wavelength is much larger than the woofer diameter or speaker cabinet diameter. Google search 'baffle step loss', 'baffle step diffraction', or 'baffle step compensation' to read better explanations of this.

There are other successful ways to build efficient woofers. Best understood are sealed and ported cabinets. There are math formulas that allow you to determine what cabinet dimensions and what port sizes will work, and predict how well or poorly a driver performs. These are discussed both in Ray Alden's and Vance Dickason's books. Beyond seal and ported cabinets, are transmission lines and folded horn cabinets. Those also now have math methods that predict performance, but they are more complex to use.

 

[bobdehunt]

You absolutely must learn about crossovers to have a successful DIY speaker design. It is as important, if not more important, than the sound quality of the drivers you choose. You can make a good sounding speaker with an inexpensive woofer and tweeter if you build the proper sized cabinet and use a crossover that keeps the drivers operating within their pass bands where they perform well. Such a speaker will sound better than one with very expensive drivers and a poorly designed crossover. Don't even mention off-the-shelf crossovers.

Another book I would read is Speaker Building 201 by Ray Alden. In fact, I would read that first.
I wish I understood more about IB speakers to answer that question. I don't even know where you can read the basics about designing them. I suspect the business about back waves not interfering with the front waves may occur, but not to the extent that its noticeable.

The main reason why IB designs are used for bass frequencies is to gain the maximum loudness that comes when woofer cones are mounted congruent to a reflecting surface, like a wall. The sound from a wall mounted woofer propagates in a hemisphere, where the sound from a woofer mounted away from a wall propagates spherically – in all directions. The wall mounted woofer is about twice as loud.

This is most noticeable with bass frequencies whose wavelength is much larger than the woofer diameter or speaker cabinet diameter. Google search 'baffle step loss', 'baffle step diffraction', or 'baffle step compensation' to read better explanations of this.

There are other successful ways to build efficient woofers. Best understood are sealed and ported cabinets. There are math formulas that allow you to determine what cabinet dimensions and what port sizes will work, and predict how well or poorly a driver performs. These are discussed both in Ray Alden's and Vance Dickason's books. Beyond seal and ported cabinets, are transmission lines and folded horn cabinets. Those also now have math methods that predict performance, but they are more complex to use.

Okay. I'll definitely look into that. Thank you. I guess I'll start looking how crossovers work now.