First off I'd like to say that I'm a long time lurker and have been doing a lot of reading about audio projects from tube amps to speaker design. A project on parts express caught my interest and I'd like to use it as an opportunity to learn. They're a pair of Omnidirectional "Top Hats" that are a user submitted project. I'd like to try to replicate them (but slightly smaller if possible) and have one main question:
How does the top hat cone improve response (in theory and practice)? I have wood and metal lathe experience so I can fabricate whatever shape will work best.
My plan is to select a driver and build a ported enclosure out of PVC similar to the original project. Since I'd like to make it smaller I know I will need to change all dimensions around. Is there software I can use to help figure out volume and port size?
My next main concern is the filter. Again, I don't have any experience designing these and was wondering if there is software or any basic knowledge to get me started?
I'm very good with construction and soldering/electronic connections so I won't have any problem building the enclosures or electronics. I need help with the math side of the design though. I know this is a big project and perhaps impractical for such a small speaker that will not sound very good. However, I like how they look and want to use this as a learning experience.
Thanks so much for any help anyone can offer me!
How does the top hat cone improve response (in theory and practice)? I have wood and metal lathe experience so I can fabricate whatever shape will work best.
My plan is to select a driver and build a ported enclosure out of PVC similar to the original project. Since I'd like to make it smaller I know I will need to change all dimensions around. Is there software I can use to help figure out volume and port size?
My next main concern is the filter. Again, I don't have any experience designing these and was wondering if there is software or any basic knowledge to get me started?
I'm very good with construction and soldering/electronic connections so I won't have any problem building the enclosures or electronics. I need help with the math side of the design though. I know this is a big project and perhaps impractical for such a small speaker that will not sound very good. However, I like how they look and want to use this as a learning experience.
Thanks so much for any help anyone can offer me!
I second this question. I understand it's a waveguide, but I'm not familiar with the math behind it. How do you calculate which shape would work best? It seems the creator of the tophat design arbitrarily picked a shape. Does it not matter that much-- Or is there a general rule to follow?
Passive Crossover Designer 7 and other spreadsheet based tools:
Jeff Bagby's Software Page
WinISD is a powerful box calculation program:
LinearTeam
How much time (in years) do you have available?! 😀
(Software)
Are you going to measure drivers and working with filters with theirs FRD/ZMA's?
For the enclosures you can start with basic software like WinISD or Unibox.
If you are using the same driver, the volume of the speaker (and port in a reflex) is going to be identical.
Omnidirectional speakers
(below Philips vintage)
(Software)
Are you going to measure drivers and working with filters with theirs FRD/ZMA's?
For the enclosures you can start with basic software like WinISD or Unibox.
If you are using the same driver, the volume of the speaker (and port in a reflex) is going to be identical.
Omnidirectional speakers
(below Philips vintage)
Attachments
Unless you need to have 360 spread, a reflector that is more 180 degree oriented would be preferable.
The highs are really tough to get right in a design like this. They somehow seem to get partially absorbed by all the reflection. A simple 90 degree-ish folded plate of plastic or other non-resonant material, put at a 45 degree angle above the driver, could work very well.
Or you could make the sides of the folded plate concave towards the driver like a magazine that is held open by the edges.
The tophat diffuser cone is just as close an approximation to the ideal 360 waveguide/reflector as he could make with the materials he had at hand.
Not anything special about that.
I'd say, have it 3D printed or CMSed if you are serious about doing a proper 360 reflector.
Not cheap, but better looking and sounding.
The highs are really tough to get right in a design like this. They somehow seem to get partially absorbed by all the reflection. A simple 90 degree-ish folded plate of plastic or other non-resonant material, put at a 45 degree angle above the driver, could work very well.
Or you could make the sides of the folded plate concave towards the driver like a magazine that is held open by the edges.
The tophat diffuser cone is just as close an approximation to the ideal 360 waveguide/reflector as he could make with the materials he had at hand.
Not anything special about that.
I'd say, have it 3D printed or CMSed if you are serious about doing a proper 360 reflector.
Not cheap, but better looking and sounding.
The shapeof the deflector/reflector works with the dispersion and FR of the driver. Its shape can make a BIG difference in the units final output. I know of no (at least affordable) tools that would let you simulate this, in practise, experimentation is probably required.
Getting the actual box figured out (volume & vent) is relatively straightforward andnot the hard part.
In the 60s Electrohome made a zillion different speakers based on the same concept, today the Duvel Planets represent a current implementation.
dave
Getting the actual box figured out (volume & vent) is relatively straightforward andnot the hard part.
In the 60s Electrohome made a zillion different speakers based on the same concept, today the Duvel Planets represent a current implementation.
dave
What Dave said.
George Augspurger started out with teak tea-trays for the deflector on one of the JBL omnidirectional speakers, and modified from there. Much empirical testing required unless you've a lot of mathematics / physics / programming skills & detailed on / off axis performance data of the drive unit & know its resonant profile.
George Augspurger started out with teak tea-trays for the deflector on one of the JBL omnidirectional speakers, and modified from there. Much empirical testing required unless you've a lot of mathematics / physics / programming skills & detailed on / off axis performance data of the drive unit & know its resonant profile.
I think a package like the professional Comsol Multiphysics FEA can do this but it's prohibitively expensive for the DIYer.
If one had sufficient 'rising response' , and didn't compensate for it in the usual way ,
the reflector/defuser/whatever shouldn't be needed !
the reflector/defuser/whatever shouldn't be needed !
That doesn't take into account off-axis response, though. With the driver radiating upward the listening angle would be at 90 degrees. Just because a driver has a rising response doesn't mean it has adequate off-axis coverage. Directivity must be taken into account for higher frequencies.
Thanks for the great information so far guys! Any recomendations for 3-4" full range drivers? I'd like to spend no more than ~$30 on each driver. After I select that I can knock out box (well, tube...) size!
Thetwinmeister, thanks for the link to the software. That's exactly what I'm looking for and will have some fun figuring it out!
Inductor, I'm currently a college student and think I will spend the rest of my life dabbling in audio 🙂 maybe (hopefully) even make a career of it! I meant to mention that I have access to a measurement microphone (my dad purchased one for home theater setup). Thanks for the link to info on omnidirectional speakers--very interesting and helpful.
I have access to a full machine shop (metal lathe, 3D printer, etc.) through my university and wouldn't be opposed to creating a few waveguides/reflectors and experimentally measuring the response with the measurement microphone. I've never used the mic before but it can't be too hard, right? 😉
Thetwinmeister, thanks for the link to the software. That's exactly what I'm looking for and will have some fun figuring it out!
Inductor, I'm currently a college student and think I will spend the rest of my life dabbling in audio 🙂 maybe (hopefully) even make a career of it! I meant to mention that I have access to a measurement microphone (my dad purchased one for home theater setup). Thanks for the link to info on omnidirectional speakers--very interesting and helpful.
I have access to a full machine shop (metal lathe, 3D printer, etc.) through my university and wouldn't be opposed to creating a few waveguides/reflectors and experimentally measuring the response with the measurement microphone. I've never used the mic before but it can't be too hard, right? 😉
For that kind of price XRK's favorite Vifa? For a bit more, and with a response that would likely suit, the Mark Audio CHR70
dave
I don't have the experience Dave has, but I have been interested in upward radiating design and considered a project not unlike yours in recent past. Yet to pursue it due to personal time restrictions.
I've been eyeing the 3 and 1/2" BMR driver which just switched hands from HiWave to Tectonic Elements. Model TEBM65C20F-8. This one claims very good off-axis response: "Nearly all of the audio in the pass band of the driver is available up to 100° off-axis."
May be under your budget, but it's something to consider.
I've been eyeing the 3 and 1/2" BMR driver which just switched hands from HiWave to Tectonic Elements. Model TEBM65C20F-8. This one claims very good off-axis response: "Nearly all of the audio in the pass band of the driver is available up to 100° off-axis."
May be under your budget, but it's something to consider.
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I'll check out the Vifa's and the Mark Audio CHR70 (which looks beautiful by the way!). The Techtonic 3.5" looks interesting and would allow me to experiment without spending too much money. I'd really like to build an enclosure and experimentally try out a few different reflector designs.
This one claims 100
/agrzesik
The Techtonic 3.5"
Tectonic Elements TEBM65C20F-8 3-1/2" BMR Full-Range Speaker 8 Ohm
If you choose the Techtonic BMR, I would like to experiment alongside you. I planned to start that build soon anyway. Expediting it would be no problem, and it would be mutually beneficial.
They do say "great minds think alike" 🙂
May I ask why you have chosen the Techtonic BMR as the driver of your interest?
I think working together would be great. I don't know about your access to tools and materials but I have a great deal at my disposal through my University's machine shop. And it sounds like you have a lot of knowledge! It won't be too hard for me to play around with a few designs.
I would like to get started soon but with work and class it could be awhile (few weeks) before anything truly gets done. I generally like to have a plan before spending money (broke college student 😀 ). I'm new to this so I don't have a scrap bin of electronics and speaker components I can grab from; I have to order and wait for delivery of most things I need. I guess I need to download some stuff to get started with enclosure and filter design. Especially since I barely know anything about the different types of filters...not sure what a filter even does on a full-range driver.
> May I ask why you have chosen the Techtonic BMR
> as the driver of your interest?
Should not need a reflector if no more
than ~ 3 ' above the floor !
> as the driver of your interest?
Should not need a reflector if no more
than ~ 3 ' above the floor !
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