I am nearing completion of building a FHXL. I have no idea what the horn is, or why this has its particular design. It would appear that the driver is placed so that half of the sound "goes" over the top into a wedge shape that dead ends. What is the purpose of that wedge? What do the slopes sides do, and why are they critical? What dimensions are cricical? What is the purpose of the fill, and how does fill "work"? If anyone can provide me with a basic understanding I would appreciate understanding the "why" behind the design.
Thanks
Thanks
It's a folded Voigt type (aka 'tapped', aka 'pipe') horn. The drive unit is tapped into the horn expansion at a given distance from the throat (i.e. the sealed end) rather than end-loading to reduce harmonic modes when not optimally boundary loaded. Damping material also helps attenuate some unwanted midrange output -being a bass horn, it only operates in the lower frequencies. The curved sides form the horn terminus; the curves force the wavefront back toward a natural spherical shape, the dimensions being chosen as appropriate to the horn design, tuning etc. Being physically simple in layout, all the dimensions in effect are serving several acoustic purposes, from providing a desired tuning, driver height & axis, horn size / expansion, tap position etc.
Thanks Scott. I very much appreciate your reply, but to be honest, could not understand a lot of it.
If I understand this correctly i still have these questions if anyone can assist:
1. This cabinet is to get better bass from a smaller driver, and that is its primary purpose?
2. Would all frequencies above the bass frequencies be created directly from the driver, with the cabinet having little impact, and the cabinet is designed to try to ensure this?
3 What is the approximate frequency where the transition to cabinet enhanced bass occurs?
4. What is the approximate lower limit to bass frequency in ideal room conditions?
5. What frequency is the cabinet tuned to, or if this doesn't make sense, what does tuning a cabinet mean?
6. Would the cabinet perform roughly the same if it were a long wedge of the same dimensions, instead of being folded?
7. If you were explaining how this works to a twelve year old, what would you say?
I have looked into Voigt designs, based on your previous post, but I am still not getting it very well.
Thanks again. Any clarification is appreciated.
If I understand this correctly i still have these questions if anyone can assist:
1. This cabinet is to get better bass from a smaller driver, and that is its primary purpose?
2. Would all frequencies above the bass frequencies be created directly from the driver, with the cabinet having little impact, and the cabinet is designed to try to ensure this?
3 What is the approximate frequency where the transition to cabinet enhanced bass occurs?
4. What is the approximate lower limit to bass frequency in ideal room conditions?
5. What frequency is the cabinet tuned to, or if this doesn't make sense, what does tuning a cabinet mean?
6. Would the cabinet perform roughly the same if it were a long wedge of the same dimensions, instead of being folded?
7. If you were explaining how this works to a twelve year old, what would you say?
I have looked into Voigt designs, based on your previous post, but I am still not getting it very well.
Thanks again. Any clarification is appreciated.
Let me posit a response to #4 in the form of another question - based on nothing other than a few years of listening- what are “ideal room conditions”?
I asked many of these questions before as a n00b myself so here's some of the answers i recall.
the frugel horn design wasn't designed to be a tapered line voigt pipe, it was designed as a bass reflex cabinet. it looks like a voigt pipe to ease construction. the bass reflex design has advantages over the voigt pipe as it doesn't produce a frequency comb, or a bass notch.
voigt pipes require an internal baffle and to be mass loaded to rectify their issues. the frugel horn does not.
the frugel horn design wasn't designed to be a tapered line voigt pipe, it was designed as a bass reflex cabinet. it looks like a voigt pipe to ease construction. the bass reflex design has advantages over the voigt pipe as it doesn't produce a frequency comb, or a bass notch.
voigt pipes require an internal baffle and to be mass loaded to rectify their issues. the frugel horn does not.
1-3 ) T/S theory, ergo box design theory, ends at the driver's upper mass corner:
Fhm = 2*Fs/Qts'
Qts': 2*Fs/Fhm
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
TL theory governs a high enough box aspect ratio: Resonances of open air columns
4) Lowest signal frequency or just shy of DC = infinite bandwidth [BW].
5) The box resonant frequency [Fb], which has nothing to do with the driver per se, but is normally based on its [Fs], effective motor strength [Qts'].
6) Yes, if there's no appreciable bend losses in the box's passband, otherwise its response will be the sum of the two.
7) Depends, though pretty much the same as me beginning at age 10; doing lots of DIY designs/projects from magazines, beginner's speaker building books except nowadays all this and at least an order of magnitude more is available on-line.
Fhm = 2*Fs/Qts'
Qts': 2*Fs/Fhm
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
TL theory governs a high enough box aspect ratio: Resonances of open air columns
4) Lowest signal frequency or just shy of DC = infinite bandwidth [BW].
5) The box resonant frequency [Fb], which has nothing to do with the driver per se, but is normally based on its [Fs], effective motor strength [Qts'].
6) Yes, if there's no appreciable bend losses in the box's passband, otherwise its response will be the sum of the two.
7) Depends, though pretty much the same as me beginning at age 10; doing lots of DIY designs/projects from magazines, beginner's speaker building books except nowadays all this and at least an order of magnitude more is available on-line.
Eh? That's major news to me, but then, I only designed it, so I bow to the authority of whoever it was who said that. It's nonsense, but they clearly know more about my own design
I've zero idea where this came from, but as noted, I bow to the authority of whoever wrote it.
Untrue.
That bit is true. 😉
FrugalHorns are wonderful designs.
Yesterday my FH Lite (Vifa driver) were tested at a friends place. He has a very expensive stereo, with Air Tight amplifiers and big Kharma main speakers. Everyone was amazed when FH Lite sounded!. How this diminutive speaker can produce such big sound? 😱
Then I pushed the FH to the back wall and bass turned bigger, clean and deep. Sound was maybe 70% of Kharmas at 1% cost 😀
Thanks Scott
Yesterday my FH Lite (Vifa driver) were tested at a friends place. He has a very expensive stereo, with Air Tight amplifiers and big Kharma main speakers. Everyone was amazed when FH Lite sounded!. How this diminutive speaker can produce such big sound? 😱
Then I pushed the FH to the back wall and bass turned bigger, clean and deep. Sound was maybe 70% of Kharmas at 1% cost 😀
Thanks Scott
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Murrfk, search about Voigt Pipe and read some article about horns. Then, Scott's explanations are clear.
Hope to see some pictures of your FHXL.
Do tell........ seriously do tell; who said all this pure BS? Please post the links, or if on FB, YT or similar, best overall to ignore all as the level of misinformation both from ignorance and/or intentional misdirection has gotten as bad as it was during the early days of the WWW.
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I appreciate all the responses. Slowly I hope to understand this a wee bit better. I will continue to research Voigt horns.
If i remembered where i read it i would link it but i do not recall, i would have to search in all the threads i posted(my first thread has over 40 pages!) also i tend to doubt myself, as my memories change over time. everything i read was on this forum though.
Sometimes others like to hear my take on things as i tend to simplify down difficult subjects, but even if wrong, at least it becomes a framework to base corrections on.
I think using a woodwind musical instrument analogy is sometimes helpful. Imagine the FHXL is a folded woodwind instrument (folded to keep the physical size manageable). The length of the cavity is sort of like the length of a folded flute. The closed end at the bottom is the end cap of the flute. The mouthpiece where you blow across is the “driver” location. In a flute, air blowing past the sharp edge of the mouthpiece oscillates from wind shedding vortices and these serve to excite the pressure waves in the flute. The speaker and the flute are resonant acoustic cavities. Their resonance defined by their length and the speed of sound, and also their boundary conditions. Flutes and Clarinets are different in that the clarinet is a 1/4 wave instrument (had a closed end) whereas the flute is technically open on both ends so it is a 1/2 wave instrument. The speaker is in essence a giant woodwind instrument designed to amplify the bass sounds from the back side of the driver. In this way, we hope to create the lower registers of the driver to give it body and bass. That’s basically it - the speaker cabinet is a bass amplifying woodwind like instrument. Driven by a vibrating speaker driver membrane rather than the breath from our mouths. Like woodwind instruments, a small pinhole air leak will prevent the lowest fundamental bass note from properly forming. Anyone who has played a flute or recorder knows that the slightest leak in a finger pad prevents you from hitting the low C. That’s why when constructing a horn or transmission line type speaker it’s critical that there are no air leaks from gaps along the passage.
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I'm missing dead links in his post, but otherwise it does remind me of early WWW. 😀
Although there was a lot out there that was fun and accessible for teenagers starting out in our hobby, even if it a lot of it was wrong. Sometimes ductaping some cardboard together motivates more than reading long threads, buying books, doing math etc. We eventually go there if our hobby grows to that point, but it's not a great entry point.
It's great to have the BiB thread and Frugelhorns etc to give starters either a finalized plan or a simple design recipe, especially because there is real knowledge underneath them.
Yeah, made a lot of heavy duty cardboard, insulation board and packing tape [duct tape was way too expensive] including a 1/4 scale Jensen Imperial using an 8" 'FR' driver [near perfect 1/4 scale of a 15"] out of a ?? 'Curb Queen' mono console: March 1952.
Innocent times and for me way way more fun, entertaining than the high tech 'paint by numbers' of today.
Innocent times and for me way way more fun, entertaining than the high tech 'paint by numbers' of today.
it was designed as a bass reflex cabinet.
This is why I like the FH, a bass horn is a great idea for various music genres.
