Yes, that's it
Outrageously heavy though. Hmm. Is that necessarily a design limit or just due to materials they chose to build prototypes.
Ge0
Ask an Acoustic Engineer (me)
- Thread starter Justin Zazzi
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Yes, that's it
Outrageously heavy though. Hmm. Is that necessarily a design limit or just due to materials they chose to build prototypes.
Ge0
Grinder
Active member
Justin,
I have a question (or two) about passive radiators.
From the mid 80s through the late 90s, I ran a pair of homemade (by a highly knowledgeable friend) passive radiator speakers in my home system - for the first year or two, as the sole speakers of a 2.0; and then for a year or two as satellites of a 2.1; and then thereafter as the center of a 3.1/5.1.
Back then, I simply assumed that as the active drivers (a pair of 4" midbass in the above case) moved in and out, the passive radiator (a simple 8" flat foam panel and surround, with construction adhesive applied to the cardboard backing for additional mass) moved accordingly, due to the positive and negative pressures created by the piston-like in/out movement of the active drivers.
Since then, I've heard it said that passive radiators are analogous to the column of air in the port of a bass reflex. And having built and played around with a few bass reflex subs, I've seen how the cone moves least while the port is most active.
So, what causes the movement of a passive radiator? <edit> How much of a factor is active driver excursion in moving the passive radiator, and does great active driver excursion potential matter (assuming there were no passive radiator excursion limitation)?
Also, having recently heard horizontally mounted passive radiator sag dismissed as "myth," I wonder if you might shed some light on the subject ...and perhaps on the subject of cone sag in active drivers as well.
I have a question (or two) about passive radiators.
From the mid 80s through the late 90s, I ran a pair of homemade (by a highly knowledgeable friend) passive radiator speakers in my home system - for the first year or two, as the sole speakers of a 2.0; and then for a year or two as satellites of a 2.1; and then thereafter as the center of a 3.1/5.1.
Back then, I simply assumed that as the active drivers (a pair of 4" midbass in the above case) moved in and out, the passive radiator (a simple 8" flat foam panel and surround, with construction adhesive applied to the cardboard backing for additional mass) moved accordingly, due to the positive and negative pressures created by the piston-like in/out movement of the active drivers.
Since then, I've heard it said that passive radiators are analogous to the column of air in the port of a bass reflex. And having built and played around with a few bass reflex subs, I've seen how the cone moves least while the port is most active.
So, what causes the movement of a passive radiator? <edit> How much of a factor is active driver excursion in moving the passive radiator, and does great active driver excursion potential matter (assuming there were no passive radiator excursion limitation)?
Also, having recently heard horizontally mounted passive radiator sag dismissed as "myth," I wonder if you might shed some light on the subject ...and perhaps on the subject of cone sag in active drivers as well.
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It's the same dynamic, really - I do want to add to this question if possible:
How does the efficiency of a PR vs port compare - meaning, a 'moving mass of air-with-friction' [I'm interested both in a) an "equivalent diaphragm", meaning 10" PR = 10" diameter port, and b) a "minimal port", or smallest diameter without port noise at full power] compare to the 'moving mass of diaphragm-with-suspension-compliance'?
I ask because Earthquake makes some pretty bold claims - 6dB gains. Obviously tuning factors in to gain as it does with traditional vents - but for equivalent tuning, noting that the inherently heavier-than-air mass makes PR's pretty exclusively low-tune beasts - I'd think an efficiency comparison could be made...
I actually have an experiment that I'm setting up for (though there's an installation in my way) - see this post for more detail.
Basically, using both high-output and standard 12's, I'm going to compare:
- output in a small sealed box
- output in an equivalent small box with two PRs
- output in a medium-size vented box with a medium-low tune (both specifics still TBD)
Guilty-
I may be the one you are referring to, who made that comment. Just wanted to add the same historical context that I did there...
Back in the day, PRs were just subs with the motors removed, and then mass added - so the suspension was often over-compliant, since it wasn't built for that mass. And I think also, intuitively - people thought a higher-compliance PR was a more efficient PR (and that's exactly my question to Justin above
), so that basic design didn't change much over time....and in fact back in the day - the same was true for speakers in general. Today, we have far heavier subs with lower compliance suspensions that support their mass without issue, even mounted horizontally.
So I was saying that today "PR sag" is no longer a given - that there's PR's (like my PRs shown in my link above) that are designed to be PRs, that have less suspension compliance, and can support their own mass.
Just raising my hand for the "guilty" charge as at least having said that somewhere, recently. :whistle:
Justin Zazzi
Wave Shepherd - aka Jazzi
This is exactly how it works at very low frequencies, below the tuning frequency of the box. This is what happens when a box "unloads" and the excursion of the woofer becomes uncontrolled so the woofer's excursion increases dramatically. This is why a subsonic or infrasonic filter is used on amplifiers so that any content below the tuning frequency of the box won't explode the woofer.
Yep, exactly right!
Short answer: angry air pixies. The woofer moves, compresses the air in the box which acts like a spring, and the compressed air in the box pushes on the passive radiator which acts like a moving mass. I get to share one of my absolute favorite animations! Behold, the paddleball!
View attachment 10819
The paddle in the kid's hand is like the woofer.
The rubber string acts like the air in the box, acting as a stretchy mechanical link between the paddle and the ball (or between the cone and the passive radiator).
The red ball acts like the passive radiator or the slug of air inside the port.
If you imagine hanging the ball from the paddle and moving the paddle up and down slowly then the ball will just follow the motion of the paddle inch for inch. This is equivalent to the air rushing into and out of the box when the cone moves slowly, like you first mention above, where the frequency is below the tuning frequency of the box.
If you move the paddle up and down at exactly the right frequency then you only have to move the paddle a tiny bit and you can send the ball flying with ease. This is the resonant frequency of the system where the frequency is a perfect match for the combination of the spring tension in the string and how heavy the ball is. This is also when the cone in the speaker moves the minimum amount but the passive radiator moves a tremendous amount (or the air in the port is moving a ton).
If you move the paddle up and down really fast then the ball tends to not move very much and remain mostly stationary. This is what happens in a box at well above the tuning frequency: the passive radiator essentially stops moving and the box starts behaving like a regular sealed box. The same thing happens with the slug of air in the port, it mostly stops moving.
A ported box can leverage the resonance to get similar output by using a woofer with less excursion, so high excursion is not required as much as it would be like in a sealed box.
However! The air pressure inside the box at resonance is really high and so the forces on the cone are really high. In theory you would want a speaker that can push really hard near the rest position. Some folks call "push" the ratio of BL^2/Re or sometimes Klippel calls it the "motor force factor". Others call it "shove" but I'm fond of skookum.
I cannot say for absolute certain, but I think this a product of materials from long ago that were more susceptible to things like sag. I want to say this is a myth for speakers made this century. If you're concerned, just flip your woofers every time you flip your mattress.
Justin Zazzi
Wave Shepherd - aka Jazzi
There's a neat twist on the question! The efficiency of a passive radiator or a port is proportional to the losses (friction) they have. In a passive radiator this can be somewhat quantified as the Qms value. A higher Qms value will be more efficient because there are less mechanical losses (less friction within the surround and spider materials).
The losses of a port are related to the surface area of the inside walls of the port. If you zoom in to the inside surface of the port then you would see the air touching the surface is going to be stationary and then as you zoom out further away from the surface of the port the air will begin to start moving. The air velocity will be maximum near the center of the port, away from the interior walls.
This effect is called a boundary layer. It can also be seen in a river where the water along the shore will be moving very slowly compared to the water moving in the middle of the channel which will be the fastest (because it is the furthest away from both the shore and the bottom of the river where the earth is). Sometimes the fluid nearest the boundary can turn into swirling patterns as seen in the image below. Notice the particles near the top of the image are moving fastest. In this case, the stationary surface or boundary (or wall) is along the bottom of the image.
View attachment 10821
Boundary layers also exist on your skin so if you sit still in a room you can feel warmer than if there is a breeze. This is how windchill works: you can exchange more cool air against your skin and it will wick away heat faster. The opposite is true in a convection oven, it cooks faster.
You can minimize the losses in the boundary layer by reducing the surface area of the port, and by ensuring the central area of the port is as far away from all surrounding surfaces as possible. If your port is a long narrow slit then you will have a ton of surface area and not much space in the "middle" for the air to move freely. A circular port is the most efficient for this. Did your math teacher in elementary school ever give you a puzzle like this:
"Karen has 100 feet of fence and she wants to make a cage for her animals. How long and how wide should the cage be to make the most room for her animals?"
And then you're like "I hate word problems Karen can figure it out herself".
Well that's the same problem here. You want maximum cross-sectional area for the air to flow through and you want the minimum wall surface area for it to rub against.
This would be a very interesting question. I think the efficiency can also be related to the surface area of the "radiator" whether is it a passive radiator or an air port. We know that if you double the number of subwoofers you have then you will get about +3dB of sound output, even if you use the same amplifier and don't add any extra watts. This is because doubling the surface area of the radiator will increase the radiation efficiency of the system.
I wonder if a similar claim could be made for passive radiators? If you take one 10" passive radiator that is tuned to 40hz, and you replace it with a pair of lighter 10" radiators that are combined tuned at the same frequency, would you get double the output from them? I would love to try that!
For your experiment, I'd love to see what results you come up with!
Justin Zazzi
Wave Shepherd - aka Jazzi
Im not sure if it's clear but did you know Jazzi is my old username?
@Justin Zazzi. First off man, major kudos on all that you've shared. I've been reading the thread and the troves of knowledge and excellent questions asked and answered has been truly remarkable. I know this post looks like an essay but my questions are very entry level and theres just a good bit of back drop...
Part 1:
As a total beginner to car audio I have a few basic questions.
I am installing a 2way active system in a 4door Nissan Altima. The sub will be a Sundown SA-12 powered abdundantly with an Orion HCCA 2400 amp that will provide 1200rms clean. I listen to bass heavy music and will be listening very loud at times. The front stage will be powered with a ppi phantom p900.4. The total system will be around 2500w rms.
I understand the basics of efficiency and how the system will not be using the entire 2500w playing music. I plan to just monitor voltages and current once the system is up and running and then plan out electrical upgrades. My stock alt is 110a. It is also time for a new battery and I'm considering a Napa Legend Premuim AGM with 55Ah and 750cca, it's just a mid level East Penn Mfg battery and of course ill be doing the big 3 upgrade.
I've heard so many conflicting tips. Some people say stock alt AND stock battery will be fine. Some people say get caps some say caps are trash. Some say get an XS power AGM and get HO alternator from the beginning; and every imaginable combination of those things.
So my question is just simply, if I have voltage drops, dimming lights etc. once the system is installed, should my next steps be a 2nd AGM in the trunk or a HO alternator?
Part 2:
I've also been having trouble finding a proper front stage that will keep up with the sub. I was considering Crescendo UN65 or PWX65 as the mids and pairing them with a proper tweeter.
I'm now considering the Steven's Audio MB8 to go in the front doors. I talked to Eric Steven's and he said his MB8s will do fine in a 2way active setup with the proper high sensitivity dome tweeter. My goals for this setup are high efficiency, decent sound quality, and good frequency coverage. Being a beginner, my goals and expectations arent pristine SQ just yet, but just loud, clear and acceptable performance. I will be getting a DSP, bomb proofing my doors, tuning, aiming, using a mic to calibrate things and setting gains properly with an o-scope or some other effective method. So I do plan on trying to make this 1st build as successful as possible.
Below is a link to the Steven's Audio MB8 and my question here is, do you have an opinion on these 8"s ? Or do you see any glaring issues with my plans that I need to address? Again I've heard so many conflicting tips on this 2way front stage to pair with the SA12 . I've heard 8s will be unruly in a car door, and how 6.5s wont be loud enough to keep up and how one or other speaker wont play high or low enough to blend, etc. I'm not looking for perfection just yet, and I have a good grasp on how to solve basic issues of door treatment and tuning. I just want to know that I'm on the right track with these MB8s and that they will at least sound pretty good with the right tweeter in the right location.
https://www.facebook.com/102258413519674/posts/495408394204672/
Part 1:
As a total beginner to car audio I have a few basic questions.
I am installing a 2way active system in a 4door Nissan Altima. The sub will be a Sundown SA-12 powered abdundantly with an Orion HCCA 2400 amp that will provide 1200rms clean. I listen to bass heavy music and will be listening very loud at times. The front stage will be powered with a ppi phantom p900.4. The total system will be around 2500w rms.
I understand the basics of efficiency and how the system will not be using the entire 2500w playing music. I plan to just monitor voltages and current once the system is up and running and then plan out electrical upgrades. My stock alt is 110a. It is also time for a new battery and I'm considering a Napa Legend Premuim AGM with 55Ah and 750cca, it's just a mid level East Penn Mfg battery and of course ill be doing the big 3 upgrade.
I've heard so many conflicting tips. Some people say stock alt AND stock battery will be fine. Some people say get caps some say caps are trash. Some say get an XS power AGM and get HO alternator from the beginning; and every imaginable combination of those things.
So my question is just simply, if I have voltage drops, dimming lights etc. once the system is installed, should my next steps be a 2nd AGM in the trunk or a HO alternator?
Part 2:
I've also been having trouble finding a proper front stage that will keep up with the sub. I was considering Crescendo UN65 or PWX65 as the mids and pairing them with a proper tweeter.
I'm now considering the Steven's Audio MB8 to go in the front doors. I talked to Eric Steven's and he said his MB8s will do fine in a 2way active setup with the proper high sensitivity dome tweeter. My goals for this setup are high efficiency, decent sound quality, and good frequency coverage. Being a beginner, my goals and expectations arent pristine SQ just yet, but just loud, clear and acceptable performance. I will be getting a DSP, bomb proofing my doors, tuning, aiming, using a mic to calibrate things and setting gains properly with an o-scope or some other effective method. So I do plan on trying to make this 1st build as successful as possible.
Below is a link to the Steven's Audio MB8 and my question here is, do you have an opinion on these 8"s ? Or do you see any glaring issues with my plans that I need to address? Again I've heard so many conflicting tips on this 2way front stage to pair with the SA12 . I've heard 8s will be unruly in a car door, and how 6.5s wont be loud enough to keep up and how one or other speaker wont play high or low enough to blend, etc. I'm not looking for perfection just yet, and I have a good grasp on how to solve basic issues of door treatment and tuning. I just want to know that I'm on the right track with these MB8s and that they will at least sound pretty good with the right tweeter in the right location.
https://www.facebook.com/102258413519674/posts/495408394204672/
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I thought this might be a great thread to ask this silly question. I am almost embarrassed to ask and have done a lot of googling but cant seem to find an answer that i understand.
Is there a rule of thumb when designing an enclosure in regards to a drivers Fs? How far below the Fs can you tune a ported enclosure? What about a sealed enclosure's F3 response, can it be below the Fs of a driver? And lastly... If designing any enclosure (not and IB) is there any weirdness that happens if the F3 is well below the Fs of the driver...
Thanks in advance
Is there a rule of thumb when designing an enclosure in regards to a drivers Fs? How far below the Fs can you tune a ported enclosure? What about a sealed enclosure's F3 response, can it be below the Fs of a driver? And lastly... If designing any enclosure (not and IB) is there any weirdness that happens if the F3 is well below the Fs of the driver...
Thanks in advance
The two amps you’ve selected are class D, which are very efficient compared to class A, A/B, etc. So I doubt you’ll have any issues with the stock alternator.
Sounds like you’re all set on how to identify the better batteries if you need to replace your current battery.
One thing you need to realize on the second battery and capacitors is that sometimes people try to fix something that may not be broken or go overkill just because. A second battery is primarily for listening to the system with the engine off (I’d use a battery isolator so the main battery doesn’t get too low a charge) but I guess those competing in SPL often use batteries to ensure they have a strong enough electrical system. Also realize that a second battery is a second load on the charging system so it is possible it could cause some system issues while the second battery is charging, which might take away from the stereo amplifiers.
Regarding a capacitor, realize that amplifiers have built-in capacitance and capacitor construction has (slightly) improved over time. A capacitor is just a really short term and very fast “battery” using the generic term of a battery being an electrical charge storage device. So I would recommend you look at adding that later IF you have a voltage issue with the amps or lights dimming. Otherwise you are just adding another device in your system that may or may not be needed and I’m all for following K.I.S.S. and keeping the system simple. I wouldn’t add another device in the signal chain if I didn’t have to and would follow that same logic to the electrical system.
Sounds like you’re all set on how to identify the better batteries if you need to replace your current battery.
One thing you need to realize on the second battery and capacitors is that sometimes people try to fix something that may not be broken or go overkill just because. A second battery is primarily for listening to the system with the engine off (I’d use a battery isolator so the main battery doesn’t get too low a charge) but I guess those competing in SPL often use batteries to ensure they have a strong enough electrical system. Also realize that a second battery is a second load on the charging system so it is possible it could cause some system issues while the second battery is charging, which might take away from the stereo amplifiers.
Regarding a capacitor, realize that amplifiers have built-in capacitance and capacitor construction has (slightly) improved over time. A capacitor is just a really short term and very fast “battery” using the generic term of a battery being an electrical charge storage device. So I would recommend you look at adding that later IF you have a voltage issue with the amps or lights dimming. Otherwise you are just adding another device in your system that may or may not be needed and I’m all for following K.I.S.S. and keeping the system simple. I wouldn’t add another device in the signal chain if I didn’t have to and would follow that same logic to the electrical system.
If Maxmil982, regarding the drivers, I’ll start with my home speakers and then use that to discuss the driver selection. My home theater speakers are JTR 212HTR (sealed version, should have gone with ported) and they have 2 12” MIDRANGE drivers to try to keep up with the sheer efficiency of the horn-loaded compression driver. The 12” midrange drivers only play down to about 80 Hz (70 if ported) so they are definitely not home midbass speakers. Now my speakers, since they are so efficient can play extremely loudly. I often tell people with most speakers if you turn them up too much, they’ll start to become unhappy (distortion), with my speakers you’ll become unhappy before they will.
So using that as the basis for the car audio discussion, you’ll want to focus on higher efficiency drivers and skew your crossover points to the upper end. So maybe the tweeter will be crossed at 4 or even 5,000 Hz. But if you’re looking at a 2-way, this isn’t going to work well for even the best 8-inch drivers so you’ll need to go with a larger format tweeter (1.5”-2” tweeter) so you can cross them closer to 2,500 or 3,000 Hz. You’ll want to choose a tweeter with an Fs closer to or even below 1,000 Hz.
For the midbass you’ll want to play it as high as you have to to integrate with the tweet but preferably bring the tweet down to 2,500Hz or so because the beaming (directionality) of an 8” starts at 2,000Hz. So you might say then maybe you should cross the tweeter at 2,000 Hz so you don’t get any beaming but then you’ll put more strain on the tweeter, which means more distortion. So with a high volume system, you want to stay away from the limits which means crossing the tweeter, crossing the 8” a little higher than maybe they’re capable of. So the midbass you might want to cross at 90 or 100 Hz instead of 80 because 80 will take more effort to play and interfere with getting loud. Then you’d just bring the subwoofer up to 90/100/110 to integrate smoothly with the midbass.
I think the biggest problem people have in car audio is they want to play super loud and make each driver play super low. You can usually have one or the other. A high efficiency driver won’t play as low as a normal efficiency driver. If you just figure out what your goals are, which it seems you have, just choose the drivers that will fit that design goal. I think the MB8 will probably work well for you but you’ll want to go with a larger, high-efficiency tweeter to ensure the 2-way will work well and play loud.
The only other comment I have is that a single 12” sub of moderate excursion may or may not handle the volume you’re trying to run. You may want to consider a higher-efficiency ported design (won’t play as deep as sealed but will be louder), adding a second sub, or going with a higher excursion design with closer to 30mm of excursion.
Sounds like the makings of a very good system. I think you’ll learn a lot.
So using that as the basis for the car audio discussion, you’ll want to focus on higher efficiency drivers and skew your crossover points to the upper end. So maybe the tweeter will be crossed at 4 or even 5,000 Hz. But if you’re looking at a 2-way, this isn’t going to work well for even the best 8-inch drivers so you’ll need to go with a larger format tweeter (1.5”-2” tweeter) so you can cross them closer to 2,500 or 3,000 Hz. You’ll want to choose a tweeter with an Fs closer to or even below 1,000 Hz.
For the midbass you’ll want to play it as high as you have to to integrate with the tweet but preferably bring the tweet down to 2,500Hz or so because the beaming (directionality) of an 8” starts at 2,000Hz. So you might say then maybe you should cross the tweeter at 2,000 Hz so you don’t get any beaming but then you’ll put more strain on the tweeter, which means more distortion. So with a high volume system, you want to stay away from the limits which means crossing the tweeter, crossing the 8” a little higher than maybe they’re capable of. So the midbass you might want to cross at 90 or 100 Hz instead of 80 because 80 will take more effort to play and interfere with getting loud. Then you’d just bring the subwoofer up to 90/100/110 to integrate smoothly with the midbass.
I think the biggest problem people have in car audio is they want to play super loud and make each driver play super low. You can usually have one or the other. A high efficiency driver won’t play as low as a normal efficiency driver. If you just figure out what your goals are, which it seems you have, just choose the drivers that will fit that design goal. I think the MB8 will probably work well for you but you’ll want to go with a larger, high-efficiency tweeter to ensure the 2-way will work well and play loud.
The only other comment I have is that a single 12” sub of moderate excursion may or may not handle the volume you’re trying to run. You may want to consider a higher-efficiency ported design (won’t play as deep as sealed but will be louder), adding a second sub, or going with a higher excursion design with closer to 30mm of excursion.
Sounds like the makings of a very good system. I think you’ll learn a lot.
Justin Zazzi
Wave Shepherd - aka Jazzi
You're welcome! Thank you for being a part of all this fun.
Looks like you've had some great feedback in your other thread about the MB8 drivers.
I admit large and powerful systems are not my specialty so listen to other folks here too. There are many talented people that can help you with this question too.
I'm not a fan of capacitors. Amplifiers have capacitors already.
I had dimming headlights on my 800w system for a while and I thought about upgrading my electrical system then my battery failed completely and I had to replace it. Turns out, my battery at end-of-life was the problem and when I replaced it I didn't have dimming lights anymore. I swear my bass output increased too but it's hard to compare since I don't have the old battery anymore. Take that anecdote for what you will, but I found it really interesting to experience a battery "upgrade" firsthand.
I'm a big fan of installing stuff and seeing if the electrical system is adequate, *then* finding what the weak link is. Could be the "big 3" power/ground cables, could be a battery, could be an alternator, could be none of those things. Can't tell until you get the gear and turn it on otherwise you might have a solution in search of a problem.
When you get the gear installed and if you notice unacceptable dimming (emphasis on unacceptable!), post a new thread and we can help you find the weak link by using a multimeter and stuff.
Justin Zazzi
Wave Shepherd - aka Jazzi
I love silly questions! We usually don't approach a problem from silly angles and so I find I learn more this way.
For a sealed system the F3 will only increase. The F3 of the woofer by itself will always be lower than the F3 of the woofer in a sealed box. This can also be seen because the Q of a woofer will always be lower than the Q in a sealed box. (Qts < Qtc)
For a ported system I don't think there is a hard rule against tuning below the woofer's resonant frequency. If you do, it looks like the tradeoffs are not very good. A lower tuning frequency can have some of these:
-group delay increases which is really objectionable to some people
-vent air velocity increases which can make noise
-output could decrease in the range just above tuning so you might get less output above Fb (see below)
Here is a simple simulation of a 6.5" subwoofer with an Fs of 35hz. The three curves are boxes of various sizes tuned to 25hz (green), 35hz (red), and 45hz (orange). Look at the dip in output in the 40-100hz region as the tuning frequency decreases.
View attachment 10978
I havent done it yet... I'm currently looking at shallow subs that i can run under the front seats. A lot of speakers i am coming across have higher Fs than what i am wanting the speaker to play down at. I have always been under the impression that if you want to play down low you need a driver with an Fs in that area or below. BUT i didnt know if this was a valid belief so i thought i would ask those with more knowledge...
Supper appreciate the feedback
Justin Zazzi
Wave Shepherd - aka Jazzi
Two major things in my favor: I absolutely love the science of sound, and I found a mentor while I was still in college.
I started in car audio because I always lived in someone else's house and couldn't put speakers and wires in the living room wherever I wanted. When I had my first car I quickly realized I could do anything I wanted with speakers so it became my laboratory. Car audio was how I experimented and learned and grew, and I soon found there was a whole community of people who loved car audio too. I joined a couple forums and started making friends.
A big breakthrough was taking the judge training for MECA sound quality competition and then becoming an active judge. This further trained my ears to listen for things, and trained my mind to communicate what I was hearing into a score rubric or into plain words that a non-competitor could easily understand. Becoming a judge is the second-most important thing I've done to further my career because it gave me a new network of people to interact with which is where the first-most important thing happened: I met my mentor.
My mentor has helped me find many ways to connect with the professional audio community, starting with the ALMA organization
https://almaint.org/
ALMA puts on an annual conference where all the engineers at all the serious audio companies come together to talk about all the cool stuff they're working on and the things they learned. This is a place to share knowledge and help eachother. There is some business that happens which is also a draw for professionals already in the field but the best part is the people staffing the company booths are literally the engineers who created the products. If you have a question about microphones, engineers from GRAS and PCB are there to help. If you want to learn about Beryllium as a tweeter dome material, Materion's engineers are there. Wolfgang Klippel is always there and usually brings a few of his employees and they always present something amazing.
Professional networking is something I always shrugged off as "yeah ok that's what old people do" but when I found the right group of people to talk to (the people at ALMA's events) then I realized it was actually amazing. This is where I met Seigfried Linkwitz (from the Linkwitz-Riley crossover) and he invited me to his home to audition his personal audio system where I immediately bought plans to build my own. This is where I met Wolfgang Klippel whom I later had a short internship with at his company in Germany. This is where I met Jerry McNutt who is the head engineer at Eminence Speaker Company where I had a summer internship and was later hired and I began my acoustics career. This is a magical place for someone like you and me.
The neat thing is ALMA's event is virtual this year and admission is free if you register here: https://almaint.org/elementor-6293/
I cannot recommend this highly enough. ALMA also has a student initiative which is getting stronger. Send me a private message here with your email address and I'll introduce you to Barry Vogel who runs ALMA.
As for starting work after college or going to grad school, I can only tell you what works well for me. I've had a lot of practical experience with audio and a lot of self-taught acoustic knowledge. When I graduated I was ready to never be in school ever again, I hated it with a burning rage I cannot put into words. I ran full speed to Kentucky to work at Eminence and never looked back.
Then I did something unfathomable that I still can't believe: I started grad school. I have been a terrible student on paper my whole life and I'm routinely in the 2.0 GPA range. I have a 3.7 in grad school right now and I'm on track to get another A with my current class. I'm enrolled in the "world campus" at Penn State and taking one class a semester with their distance education program (before distance education was cool like today haha). My company is reimbursing the tuition and I'm learning the most amazing stuff and my favorite part is I'm applying the knowledge in a very serious way before the final exam. Right now I'm taking the 2nd of the signal processing classes and I'm applying literally everything I know in that class to a project this week. It's incredible.
So for me, the combination of practical knowledge and experience with acoustics was powerful and let me start my career. If you don't have as much, you might benefit from grad school and if you go full time then you can get it done in a year or two instead of the 5-year pace that I'm at. Plus you don't have to worry about homework for the next five years while you're also working full time (that part sucks hard).
I guess my advice is do what you love and find two communities: a casual one to make friends and a professional one to start a career (and also make friends). ALMA is the best professional one I know of, so lets start there. Send me a message with your contact info.
Justin Zazzi
Wave Shepherd - aka Jazzi
I forgot something important.
A ported box can be manipulated with an equalizer to some degree, but only above the tuning frequency. If you want output below the Fs of the driver you could build a box that is tuned really low and then attempt to boost it with EQ. However if you built a box that is tuned higher then you should not try to boost frequencies below the tuning frequency otherwise the woofer will just run out of excursion without making any more noise and it'll fail.
@Justin Zazzi. Thanks for the reply and the tips about the electrical upgrades. I'd like to send you a PM, exchange emails and in the future ask your opinion on some home audio options... I just have to do a ton of research first lol. I'm also interested in the ALMA event, sounds like a great opportunity to learn.
And again, this thread has been great! Tons of cool people here and on the whole forum. You, and people like you who have a genuine passion for their craft and are willing to invest in themselves and others are our national treasures. It's a real inspiration and motivates a lot of people to pursue their own interests to the fullest.
And again, this thread has been great! Tons of cool people here and on the whole forum. You, and people like you who have a genuine passion for their craft and are willing to invest in themselves and others are our national treasures. It's a real inspiration and motivates a lot of people to pursue their own interests to the fullest.