Hello all, I have had this recurring thought or question when trying to determine how to model a speaker in a traditional open-back guitar cabinet. While not acting as a vented or sealed enclosure, I feel it is easiest to think of in terms of baffle step for a tweeter, with the baffle supporting frequencies that are small enough to reflect off the baffle. An open back cabinet would do the same, yet maybe extend the frequency response even lower due to the front and rear waves being unable to interact with each other until much lower.
Has anyone else had any thoughts on this or know of any literature on this topic? I seem to be stuck between two hobbies here( diy audio and a gear hoarder who masquerades as a musician)
Thanks
Has anyone else had any thoughts on this or know of any literature on this topic? I seem to be stuck between two hobbies here( diy audio and a gear hoarder who masquerades as a musician)
Thanks
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Acoustical Engineering by Harry Olson
https://www.amazon.com/Acoustical-engineering-Harry-Ferdinand-Olson/dp/B0007E672Y
Acoustical Engineering by Harry Olson
https://www.amazon.com/Acoustical-engineering-Harry-Ferdinand-Olson/dp/B0007E672Y
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Why not think of it like woofer in an H frame and then just design it for double the rolloff frequency?
I wonder how much of a guitar amp's design is to resemble a suitcase for easy handling? Then the rest of the dimensions fell into place regarding wrapping a speaker & electronics in wood. Two 12s and a 100W tube amp? A suitcase that looks like a Fender Twin.
I wonder how much of a guitar amp's design is to resemble a suitcase for easy handling? Then the rest of the dimensions fell into place regarding wrapping a speaker & electronics in wood. Two 12s and a 100W tube amp? A suitcase that looks like a Fender Twin.
Yes.
To boot, MANY cabinets used way back then, from table radios to living room "combinations" or "radio - grammophone" used open back cabinets.
Speaker resonance, high Q and power amp poor to non-existing damping somewhat masked that, so a cabinet with response falling below , say, 200Hz was "helped", sort of, by a boomy peak between 90 and 150 Hz.
Most people (Hi FI was always a tiny crowd) was pleased with that and "thought" they had "bass".
To boot, MANY cabinets used way back then, from table radios to living room "combinations" or "radio - grammophone" used open back cabinets.
Speaker resonance, high Q and power amp poor to non-existing damping somewhat masked that, so a cabinet with response falling below , say, 200Hz was "helped", sort of, by a boomy peak between 90 and 150 Hz.
Most people (Hi FI was always a tiny crowd) was pleased with that and "thought" they had "bass".
As JM says, ALL domestic speakers 1928-1963 were open-back baffles. This is an effective speaker (if you don't need deep bass), and potentially more sound power in the room since both sides of the cone contribute over most of the audio band; the dipole/cardioid pattern gives more "throw".
So Olson's writings are relevant, if maybe too dense and insightless for most readers.
There was another great paper in the 1970s. Cats at EV derived the flat/bent baffle in terms of the new T/S thinking. They found a niche using large numbers of large very cheap drivers. My memory says D.B.Keele was an author but it is not cited on his website. You could contact him and see if he remembers the paper.
The Official website of D.B.(Don) Keele, Jr.
AES Papers -- Official website of D.B.Keele
So Olson's writings are relevant, if maybe too dense and insightless for most readers.
There was another great paper in the 1970s. Cats at EV derived the flat/bent baffle in terms of the new T/S thinking. They found a niche using large numbers of large very cheap drivers. My memory says D.B.Keele was an author but it is not cited on his website. You could contact him and see if he remembers the paper.
The Official website of D.B.(Don) Keele, Jr.
AES Papers -- Official website of D.B.Keele
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me> My memory says.......
Newman.
Dipole Radiator Systems
Author: Newman, Raymond J.
Journal of the Audio Engineering Society
RA. J.. Newman, "Dipole Radiator Systems," J. Audio Eng. Soc., vol. 28, no. 1/2, pp. 35-39, (1980 January/February.).
AES E-Library >> Dipole Radiator Systems
Highly recommended; however costs $33 if you do not have AES access. (You can avoid >$30 of mistakes by reading this before building.)
Newman.
Dipole Radiator Systems
Author: Newman, Raymond J.
Journal of the Audio Engineering Society
RA. J.. Newman, "Dipole Radiator Systems," J. Audio Eng. Soc., vol. 28, no. 1/2, pp. 35-39, (1980 January/February.).
AES E-Library >> Dipole Radiator Systems
Highly recommended; however costs $33 if you do not have AES access. (You can avoid >$30 of mistakes by reading this before building.)
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Thanks for the reply's you all. Readings like this are right up my alley, I hardly ever got to do anything with acoustic when I was in undergrad EE. Makes it a bit more digestible when its a subject you actually care about. Ive delved into Martin King's work on transmission lines this past year and never looked back - I am well accustomed with TS parameters and the (most) physics of wave theory.
On the topic of older open back radio cabinets and such - I had the opportunity to restore an old RCA stereo cabinet dating to about 1962 - a little TLC was all it needed to get playing again and I was quite surprised by the low end response. I assumed the base principle Im inquiring about in the guitar cabinet aspect is much the same as the older style cabinets - acting as a large baffle instead of an enclosure to add gain to the response at a given frequency / frequencies.
It seems curious, coming from a psuedo-Hi-Fi aspect, how the enclosure for most instrument cabinets are solely based on physical limitations such as dimensions/ weight. While there is absolutely a time and place for this, the apparent lack of " acoustical engineering" that goes into the design of these cabinets is interesting. Granted - guitar/bass/keyboard amps allow quite a bit of eq and tone shaping ability, but I do not see why cabinets designed for more specific roles/situation are not more popular.
On the topic of older open back radio cabinets and such - I had the opportunity to restore an old RCA stereo cabinet dating to about 1962 - a little TLC was all it needed to get playing again and I was quite surprised by the low end response. I assumed the base principle Im inquiring about in the guitar cabinet aspect is much the same as the older style cabinets - acting as a large baffle instead of an enclosure to add gain to the response at a given frequency / frequencies.
It seems curious, coming from a psuedo-Hi-Fi aspect, how the enclosure for most instrument cabinets are solely based on physical limitations such as dimensions/ weight. While there is absolutely a time and place for this, the apparent lack of " acoustical engineering" that goes into the design of these cabinets is interesting. Granted - guitar/bass/keyboard amps allow quite a bit of eq and tone shaping ability, but I do not see why cabinets designed for more specific roles/situation are not more popular.