Is Zd value given for a metronome design measured from the top or bottom of the inside of the enclosure? I know it doesn't matter for this particular design as the driver is centered, but for other drivers that is not always the case.
In a staight Metronome, the Zd is measured at the center point of the driver. For an Omni-met would Zd be measured at the midpoint of the depth of the drivers cone?
I know these are probably very basic questions, but I this is my first project with speakers.
Thanks, Jim
In a staight Metronome, the Zd is measured at the center point of the driver. For an Omni-met would Zd be measured at the midpoint of the depth of the drivers cone?
I know these are probably very basic questions, but I this is my first project with speakers.
Thanks, Jim
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It took a few iterations to get everything figured out (minimum volume folded Betsy-K Met):
https://frugal-horn.com/downloads/Folded-Betsy-K-Metronome-110519.pdf
dave
https://frugal-horn.com/downloads/Folded-Betsy-K-Metronome-110519.pdf
dave
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Nice. 
I bet figuring that one out caused a few more grey hairs Dave...
To be honest, when we're dealing with folded ML-horns, were I designing from scratch (I appreciate the caveat) I'd just do a box with a single-direction taper; I don't think there's much of an acoustic advantage in the quadratic expansion of the Metronome relative to single direction; it's mostly about the aesthetics. Since those cease to be significant when it's folded up, I'd go with whatever makes life easy.
I bet figuring that one out caused a few more grey hairs Dave...To be honest, when we're dealing with folded ML-horns, were I designing from scratch (I appreciate the caveat) I'd just do a box with a single-direction taper; I don't think there's much of an acoustic advantage in the quadratic expansion of the Metronome relative to single direction; it's mostly about the aesthetics. Since those cease to be significant when it's folded up, I'd go with whatever makes life easy.
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World’s largest gnome needs a new home – Parksville Qualicum Beach News
Now on its way to Victoria.
dave
The Galey family is needing to look for a variance with Saanich municipality over Howard’s height - apparently .5 metre too tall for bylaws? Give me a freaking break.
As kitschy as the whole Blenkinsop Valley attraction is, it does draw huge crowds for their seasonal events, and their in season strawberries make the California/Mexico imports taste like poorly flavoured styrofoam.
Galey Farms Corn Maze, Market & Railway
As kitschy as the whole Blenkinsop Valley attraction is, it does draw huge crowds for their seasonal events, and their in season strawberries make the California/Mexico imports taste like poorly flavoured styrofoam.
Galey Farms Corn Maze, Market & Railway
Now on its way to Victoria.
dave
Park it beside John A Macdonalds' statue?
Wow, what a clever design!. It looks like it might actually be easier to build than what Steve Cresswell came up with, Each half has no woodworking challenge more difficult than a standard Met. . I'd guess this type of design would need some holey braces on all sides.
I need to understand better how these work. Can anyone recommend any resources that start with the basics?
What, the metronome? It's an ML-horn with a quadratic taper. Functionally speaking the expansion rate for the lengths involved is insufficient for the quadratic to make much practical difference in loading terms to a conical horn i.e. single expansion direction. The main difference is the aesthetics -if you like the twin-direction expansion of the met., then that's the choice. If that doesn't bother you so much, or you want a folded version, then a single-expansion direction will work more or less the same and is easier to build. An expanding pipe (conical, quadratic or whatever) operates over a wider BW than a straight pipe so if a driver requires slightly broader band support than a straight MLTL they can be useful for that.
Thanks for the explanation. I would like to understand the relationship of the length, volume etc for variants of the MLTL . My understanding is very rudimentary, the cabinet serves to reinforce a certain bandwith, attempting to even out the weaker frequencies of a given driver. Longer length, bigger volume lower bandwith.
On another note, I am seeing that no matter what you do in terms of layout: straight, various folded layouts, the Betsy K driver results in a rather large enclosure if you use a quadratic taper. The WIBAQ is much more compact. I really like the idea of the omni met, but that's really better suited for a driver that does not require such a large volume.
I am probably going to build a WIBAQ variant but may look at placing the mass loaded port on the bottom as is done with the Metronome. A omni directional variant might be possible, too. I guess I better get more familiar with speaker design.
Thanks all for the assistance, I should probably take discussion of WIBAQ to the WIBAQ thread. A metronome variant of some kind will need to be a future project.
On another note, I am seeing that no matter what you do in terms of layout: straight, various folded layouts, the Betsy K driver results in a rather large enclosure if you use a quadratic taper. The WIBAQ is much more compact. I really like the idea of the omni met, but that's really better suited for a driver that does not require such a large volume.
I am probably going to build a WIBAQ variant but may look at placing the mass loaded port on the bottom as is done with the Metronome. A omni directional variant might be possible, too. I guess I better get more familiar with speaker design.
Thanks all for the assistance, I should probably take discussion of WIBAQ to the WIBAQ thread. A metronome variant of some kind will need to be a future project.
That gets really involved to the point where working it out using the wave equation blended in with T/S theory is the only way AFAIK, which MJK among others did, so recommend studying his docs. A few of us use rules-of-thumb, but most either rely on MJK's design routine or fiddle with Hornresp or similar TL/horn programs till they get an acceptable frequency response/tuning.
In the same vein: Hornresp
GM
In the same vein: Hornresp
GM
'Compact' is relative since until Vas is quite large the dominant spec WRT net cab volume is Qts': Vb = 20*Vas*Qts'^3.3
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
[ML]TLs are 1/4 WL resonators whereas the tapered [ML] horn, TQWT alignments are 1/2 WL resonators, so axial length must be twice as long to load to a given pipe/horn tuning [Fb/Fp].
That said, whether straight or tapered, for a given net volume the tapered yields a lower tuning, so if by 'compact' you mean amount of floor space required, then obviously true, otherwise the WIBAQ MLTL can be converted to tapered with the caveat that the driver needs to 'slide' down the pipe a bit for smoothest response and the vent lengthened to flatten the low end response to match except for being tuned a bit lower.
GM
GM,
I just found MJK's work and started skimming the various sections. I'm hoping I can understand enough of it to be able to put it to use, but I can tell the math will be challenging for me at best. I do have in mind to dig into the theory and see if I can understand it well enough to put it to use in speaker design.For now I'm going to use a stock WIBAQ design as it works well. For now no changes from a well conceived design as I dont know enough to make improvements except by accident. Thanks for all the advice it's helpful.
I just found MJK's work and started skimming the various sections. I'm hoping I can understand enough of it to be able to put it to use, but I can tell the math will be challenging for me at best. I do have in mind to dig into the theory and see if I can understand it well enough to put it to use in speaker design.For now I'm going to use a stock WIBAQ design as it works well. For now no changes from a well conceived design as I dont know enough to make improvements except by accident. Thanks for all the advice it's helpful.