convert 2-way bookshelf into 3-way tower?

[TLS Guy]

To clarify...the base, top and front baffle would be perpendicular. The sides would be wide at the base and slope up towards the top, like a triangle. The back would also be wide at the base and slope towards the top. So the base would be something like 14x12 and the top would be something like 6x6 (external dims)

When building such a box how in the world do you calculate volume on something like this...it's not a pyramid, front face is perpendicular to base. It's not a triangular prism because you have flat sections on top and an extra sloping side. When only two sides were slanted it was easy. Now with the addition of a third side sloping in I am lost on how to calculate volume. Any pointers? Do I need to find a friend that knows CAD to draw it up and have a program calculate volume?

I understood the first time from your description.

What you do is divide the structure into sections. On each side there will be a triangular shaped piece and another triangular piece on the back. In the middle will be a rectangular shaped piece, which you will calculate in the normal way.

To calculate the volume of the triangular pieces, you multiply half the height X the base X the depth. Then you add the volume of all four sections. It will be quite easy to do.

 

[Loren42]

To clarify...the base, top and front baffle would be perpendicular. The sides would be wide at the base and slope up towards the top, like a triangle. The back would also be wide at the base and slope towards the top. So the base would be something like 14x12 and the top would be something like 6x6 (external dims)

When building such a box how in the world do you calculate volume on something like this...it's not a pyramid, front face is perpendicular to base. It's not a triangular prism because you have flat sections on top and an extra sloping side. When only two sides were slanted it was easy. Now with the addition of a third side sloping in I am lost on how to calculate volume. Any pointers? Do I need to find a friend that knows CAD to draw it up and have a program calculate volume?

What you are building is a truncated pyramid. Be glad it doesn't look like this:

If you can give me the exact dimensions, wall thickness, and number and size of the braces I can build a 3-d model in CAD that can compute the internal volume.

Here is the internal model of my cabinet after all walls, woofer, braces, ports, etc. have been included in the model:

Otherwise, what TLS Guy described is the correct method for breaking the problem down into manageable chunks and computing the volume of each subsection.

If you like mental gymnastics it can be challenging and fun.

 

[Guiria]

...If you can give me the exact dimensions, wall thickness, and number and size of the braces I can build a 3-d model in CAD that can compute the internal volume.

Otherwise, what TLS Guy described is the correct method for breaking the problem down into manageable chunks and computing the volume of each subsection.

If you like mental gymnastics it can be challenging and fun.

Your cabinet looks nuts...hope you have some wood building skills

Thanks for the offer but after thinking about the build complexity of a truncated pyramid I am opting for a slightly simpler box so that I can get the job done in the time frame alloted...hopefully I can settle into a design I feel I can execute in the next couple of weeks. Building the boxes won't happen until after May 11th.

 

[Loren42]

Your cabinet looks nuts...hope you have some wood building skills

Already done. Just waiting to put veneer on them.

 

[TLS Guy]

Already done. Just waiting to put veneer on them.

Beautiful work! Is that the tube amp you built? If it is you are a real craftsman.

 

[Guiria]

That speaker with veneer will be something fierce. Nice work. I consider myself semi handicapped working with wood. I am getting better though...few more subwoofers and pairs of speakers and I will figure it out

I've thought about veneering my towers...are you planning on using a vacuum bag, PSA backed veneer, having them done somewhere? What are your thoughts? I will probably call around and see if I can get someone to finish the speakers once they are done...we'll see if funds permit for that.

There is nothing like custom built DIY.

 

[Loren42]

Beautiful work! Is that the tube amp you built? If it is you are a real craftsman.

Thank you very much.

Yes, that is the amp. It has been working flawless for me.

 

[Loren42]

That speaker with veneer will be something fierce. Nice work. I consider myself semi handicapped working with wood. I am getting better though...few more subwoofers and pairs of speakers and I will figure it out

I've thought about veneering my towers...are you planning on using a vacuum bag, PSA backed veneer, having them done somewhere? What are your thoughts? I will probably call around and see if I can get someone to finish the speakers once they are done...we'll see if funds permit for that.

There is nothing like custom built DIY.

I bought a book on veneering. The process I am considering is called "hammering".

Basically, you apply glue to both the veneer and the substrate, allow to dry most of the way, then use an iron and a blunt chisel like object to work the veneer on.

The veneer is koa, which has a very exotic, but warm grain.

 

[lsiberian]

Thank you very much.

Yes, that is the amp. It has been working flawless for me.

I envy that more than the speakers. I really want to get into DIY amps. I'd love to do a tube amp. I'm probably gonna start with a 41hz kit though.

 

[highfigh]

Your 2.77 cu. ft. sealed enclosure seems very reasonable for your needs.

I make Qtc around 0.5, which would give a clean tight bass I prefer.

That's great for classical but if someone listens to a wide variety of music, that will be too well-damped. Not that there's anything wrong with listening to only one style but .5 is pretty dry-sounding for a lot of music.

 

[highfigh]

I bought a book on veneering. The process I am considering is called "hammering".

Basically, you apply glue to both the veneer and the substrate, allow to dry most of the way, then use an iron and a blunt chisel like object to work the veneer on.

The veneer is koa, which has a very exotic, but warm grain.

Look around for info on gluing woods- IIRC, Koa is one of the species that has a lot of oils and wax in it, like teak. Often, these species need to be wiped down with solvent in order to make them gluable.

The glue you'll be using- is it wood glue? Look at WoodCraft and Rockler- they both have veneer "hammers". Also, Highland Woodworking and Lee Valley have a lot of supplies and tools, if you'll be in the market for more later.

 

[TLS Guy]

That's great for classical but if someone listens to a wide variety of music, that will be too well-damped. Not that there's anything wrong with listening to only one style but .5 is pretty dry-sounding for a lot of music.

You raise an interesting topic. First I should point out, that I did recommend Guiria to modify the enclosure to a Qt of 0.7.

However the question of highly damped speakers is an interesting, and I agree still a controversy in speaker design. So you have given me an introduction to giving my views.

I personally think the bass is not accurate in speakers that are not critically damped. That does not mean that all critically damped speakers sound right.

However the piano, bass strings, tymps and the bass pipes of the organ never sound quite right to me in speakers that are not critically damped.

What I will say is that a critically damped speaker leaves the rest of the speaker stark naked. In other words other faults will stick out like a sore thumb. So the spreading bass does provide a degree of cover for other ills. No where in the design is this more true than in the area of step/diffraction compensation. It has to be right on the money, and I believe requires an active approach. That is primarily why I developed such a unique approach to bass management and diffraction compensation.

The other issue, is that I have no doubt that highly damped speakers are much less likely to excite room modes as vigorously as resonant designs.

The more controversial issue is does the design matter. In other words is a critically damped sealed enclosure equivalent to a TL. My view is an unequivocal no. However I can't tell you with any certainty why.

Over the years I have rubbed shoulders a lot with pipe organ builders. They all firmly hold to a concept foreign to acoustic engineers. The concept is the encircling nature of the sound emitted by pipes. What they mean is that for a guitar, for instance, the sound drops quickly as you move away from it. However even the softest, quiet organ pipe is heard pretty much at the same level where ever you are in the church. An electric organ does not do this. I have confirmed this myself many times.

This holds true in this space here. The bass is highly uniform through out the room, even though there is no special acoustic treatment.

Now it is well known that I listen, apart from movies, to classical music almost exclusively.

However visitors have commented that the quality of the bass really sets this system apart from other systems they have heard, above all other parameters.

There is a retired mix engineer near here who has mixed for many of the famous. He brings all sorts of offerings here. One of his cuts have a couple of tuned guitars to produce a very low beat frequency, a la, the Tibetan monks. He just loves it. So this highly damped system seems to please across musical genres.

Anyhow you don't live that far away, once the summer lake season gets into high gear, you should treat yourself to a little R & R and bring any selections you wish. I think you would have an interesting time.

 

[highfigh]

You raise an interesting topic. First I should point out, that I did recommend Guiria to modify the enclosure to a Qt of 0.7.

However the question of highly damped speakers is an interesting, and I agree still a controversy in speaker design. So you have given me an introduction to giving my views.

I personally think the bass is not accurate in speakers that are not critically damped. That does not mean that all critically damped speakers sound right.

However the piano, bass strings, tymps and the bass pipes of the organ never sound quite right to me in speakers that are not critically damped.

What I will say is that a critically damped speaker leaves the rest of the speaker stark naked. In other words other faults will stick out like a sore thumb. So the spreading bass does provide a degree of cover for other ills. No where in the design is this more true than in the area of step/diffraction compensation. It has to be right on the money, and I believe requires an active approach. That is primarily why I developed such a unique approach to bass management and diffraction compensation.

The other issue, is that I have no doubt that highly damped speakers are much less likely to excite room modes as vigorously as resonant designs.

The more controversial issue is does the design matter. In other words is a critically damped sealed enclosure equivalent to a TL. My view is an unequivocal no. However I can't tell you with any certainty why.

Over the years I have rubbed shoulders a lot with pipe organ builders. They all firmly hold to a concept foreign to acoustic engineers. The concept is the encircling nature of the sound emitted by pipes. What they mean is that for a guitar, for instance, the sound drops quickly as you move away from it. However even the softest, quiet organ pipe is heard pretty much at the same level where ever you are in the church. An electric organ does not do this. I have confirmed this myself many times.

This holds true in this space here. The bass is highly uniform through out the room, even though there is no special acoustic treatment.

Now it is well known that I listen, apart from movies, to classical music almost exclusively.

However visitors have commented that the quality of the bass really sets this system apart from other systems they have heard, above all other parameters.

There is a retired mix engineer near here who has mixed for many of the famous. He brings all sorts of offerings here. One of his cuts have a couple of tuned guitars to produce a very low beat frequency, a la, the Tibetan monks. He just loves it. So this highly damped system seems to please across musical genres.

Anyhow you don't live that far away, once the summer lake season gets into high gear, you should treat yourself to a little R & R and bring any selections you wish. I think you would have an interesting time.

As I have often posted, attempts to create a system that reproduces the music "exactly as it was heard when it was created" are futile but we can create a system that sounds really, really good. The sound of bass, specifically, is almost impossible to reproduce because microphones aren't necessarily going to capture the energy as well as needed. They certainly won't capture the room's sound when they're directional. Pop music often uses electronic keyboards- not because they sound correct but because they're extremely consistent in the sound they produce and because they rarely need tuning. Bass guitar is almost always sent from the amplifier head and/or effects directly to the mixing desk, so the chance of that sounding "accurate" is zero. The kick drum usually has a small hole in the outer head with a mic stuck in it, which makes it very sensitive but not necessarily accurate, That pretty much takes care of the deepest bass and the ringing woofer/cabinet makes people think that more bass is better bass. I have been thinking of getting some kind of oscilloscope software and test lead kit for my computer so I can compare input signal with output and what comes from speakers and I know several drummers who would be able/willing to record some tracks that I can use for comparison. Since drums are one of the things I I use to form my opinions of speakers, it's kind of a no-brainer.

If it was possible to make speakers that reproduce only the input waveform and not add anything to it, I'm absolutely sure most people would hate the way they sound.

However, from what I have read/heard, pipes make the whole acoustic space resonate, not just the air inside and that's caused by the reeds (if used) or the cutup of the pipe, without using a diaphragm. They also produce their sound with a surprisingly low amount of air pressure, relative to their SPL. The harmonic content is another story. I have heard of people building pipe organs in their homes but they're really not able to reproduce the experience of a large acoustic space, like a church or cathedral. IMO, large spaces with the number of irregular boundaries, corners, dimensions and the amount of diffusion is the reason the decay rate is as consistent and favorable as it is and the room modes are as evenly distributed as they are. Remove the seating, any carpet, flatten/smooth the walls and ceilings and the acoustics will be much worse, although still not as bad as a typical listening room with speakers having high Qtc.

I like well-damped woofers, preferably sealed. However, in my house, the vented sub I use doesn't do anything objectionable, unlike many I have heard.

I don't listen to a lot of classical music but my brother used to sing locally, where an organist by the name of John Weissrock played, so I have heard pipe organ in a good environment.

 

[highfigh]

I find it interesting that you referenced guitar, which is a tuned box that uses bracing to remove as many resonant peaks as possible.

 

[yepimonfire]

That's great for classical but if someone listens to a wide variety of music, that will be too well-damped. Not that there's anything wrong with listening to only one style but .5 is pretty dry-sounding for a lot of music.

isn't better damping good for all kinds of music, shouldn't a speaker sound good on all types of music?

 

[TLS Guy]

I find it interesting that you referenced guitar, which is a tuned box that uses bracing to remove as many resonant peaks as possible.

I did that because in many churches these days there has been a marked deterioration in the music, and it has turned into music with guitars prominent. A guitar is totally unsuitable for performance in a large space, even amplified. I remember the organ builder John Norldie, drawing my attention to this. A group of folk/pop instruments was very loud up close but not down the church, with the guitars barely audible at a distant. However when one of his lovely instruments had its chance even the softest flute stops filled the space evenly.

Not only that the amplified instruments were boomy, but not the bass organ pipes in the same space.

So that was why I referenced the guitar.

 

[TLS Guy]

isn't better damping good for all kinds of music, shouldn't a speaker sound good on all types of music?

I'm not absolutely certain about that.

All I know is I can not use any source that contains electronic instruments, or instruments that only have a "voice" through loudspeakers to evaluate and develop speakers.

The problem is when you mix instruments that only have a voice into a mix panel, the speaker becomes part of the instrument.

I have noted that engineers that tend to mix pop music generally do it through speakers that have a lot of characteristics I abhor.

So I, like a lot of the fine British manufacturers give no heed to how there speakers sound on the music of the pop culture. I would say they and I don't know how the music is supposed to sound and we don't care.

Having said that I do note that in the movie experience there is a lot of music that is of the pop culture, and I've noted that people have no aversion to the sound and balance of these speakers in that setting, in fact quite the contrary.

So I suspect you premise is correct, that if it is a really good speaker for classical music all tastes in music will in fact be satisfied.

 

[Guiria]

I might end up building the bass chamber between1.5-2 cubic feet. If it sounds too dry I can add wood or something to the inside of the cabinet to take up more volume.

Music that I like but don't listen to tons would be

good acapella / jazz choir recordings...and in good I mean a good choir and a good recording
Well recorded live music...one of my favorite albums is Mana: Unplugged
String instruments with distinct solo's...I like to hear detailed instruments and when their is a whole orchestra, details of individual instruments tend to get lost in the production. Perhaps I haven't listened to the right recordings.

So not to get too far off the topic of this thread but I think this set of towers is going to put a big smile on my face when I get to sit back and enjoy them.

Enough is enough...off to study

 

[Loren42]

Look around for info on gluing woods- IIRC, Koa is one of the species that has a lot of oils and wax in it, like teak. Often, these species need to be wiped down with solvent in order to make them gluable.

The glue you'll be using- is it wood glue? Look at WoodCraft and Rockler- they both have veneer "hammers". Also, Highland Woodworking and Lee Valley have a lot of supplies and tools, if you'll be in the market for more later.

Thank you for the information! I was going to use a yellow wood glue coated to both surfaces. It is supposed to allow to dry to the point where it is barely sticky, then the two are placed together and heated with an iron until the glue melts and you can "hammer" it into place.

That's the theory, anyway.

 

[Guiria]

Found this article in the AV University here

http://www.audioholics.com/tweaks/do-it-yourself-diy-topics/building-do-it-yourself-loudspeakers/building-diy-loudspeakers-trapezoidal-design

I think my speakers will be very similar...probably a little smaller, and they will have separate enclosures for midrange and bass woofers.

So angling the front vs. the back would be the way to go to time align the drivers? How critical is that, I'm thinking not very since 95% of speakers are built on a vertical plane.

hmmm...