A bunch o' random observations:
- "Audible" is a key and big word here. From the equal loudness contours in @weltersys post #74, it seems 40 Hz would be audible at 60some dB. But if you are playing at I think you said 70 dB, for the bass to sound correctly loud you'd follow the 70 Hz contour up from the midrange and find you'd need ≈ 106 dB. How far away are you listening? If 2 m that means like 112 dB from the driver, if 3m then like 116 dB if I'm doing the math right in my head. (That's ignoring some amount of room gain).
- More information is in this paywalled thing https://www.aes.org/e-lib/online/browse.cfm?elib=5147
- From a driver small enough to work in a 4L box, or a port of small enough area to tune that box down to 40 Hz, I cannot imagine it is possible to move/flow enough air. I gotta do some stuff for work so sorry I cop out no time to do the calculations right now. Well OK from an online calculator it says a 6" driver would have a 76mm Xmax
oops: one direction I presume). http://www.baudline.com/erik/bass/xmaxer.html
- A port functions as a kind of "plug" mass of air on the "spring" that the air in the box forms. Just like a suspension on a car, or jumping on a trampoline, this resonates at a certain frequency. A passive radiator substitutes cone mass for air mass, with the advantage of maybe not taking up so much room inside the enclosure. In tiny boxes sometimes you can realize a lower tuning than is physically possible with a port of sufficient cross section to not compress/choke and distort. A disadvantage can be less linearity depending on the PR construction.
- As I note in the previous post "boominess" is hard to relate to simulations. Nevertheless I dislike ported setups where the response begins to roll off but then bumps back up or even just shelves. I feel that is an indication that the related time domain response will have some degree of flaw.
- From work I did with automotive enclosures, I do not like your post #40. Instinct says that has a likelihood of acting like a number of tuned resonant tubes more than a simple air cavity. What was the reason for all those kind of tunnels? It can't be made with just like almost dowels sticking up from the surface to open up the inside volume more?
I like the "40 Hz Challenge!" idea. Maybe you'd have an easier time to start with the driver-find small drivers that can generate the necessary minimum SPL and then see what the boxes look like. The Purifi woofer goes low in a relative small box with a lot of SPL, more than 4L though I think. Hey is 4L too big to build into a top hat? A wearable backpack? Maybe you should just use a bass shaker?
Mr. head Unit, thank you man for going through the thread and try help understand things
Listening distance will be from 30 - 60cm. Unit will be near the ears. I do not enjoy using headphones, and especially if my partner is sharing the experience. We would be listening to a dub late night and I would get the urge to pick up the bass and try something
It feels like unless I am driving the cab hard, the sound doesn't take on the tuba like flavour which is the tone that I am after. An uneducated guess is that just like a drum that needs to be struck hard to set off the resonances. This makes my regular bass speaker unusable, as those effects just do not happen with the speaker idling. This is my interest in building a tiny 43hz tuned box that I can place close by the ear and drive it hard without exceeding polite listening levels at 2am surrounded by sleeping retirees. I would like to make this battery powered so that I may do the same on the steps at our Torquay sailing club nights as I sit and meditate with riddim with "planky" (bit of plank with pickups and 4-strings, headless) and watch the sail boats bobbing on the mooring
I did this for the electronics as well. Over the past two years I have acquired all the parts and materials to make a tiny tube pre and power amp that I would like to really push and pick up the sound for real amplification with Class D for the 40hz box
This is a very personal project that I would like to take my time with and execute with the finest detail. The blue cab in post #40 was a home theatre soundbar distraction using the same ZR6 as well an OEM and a CT Sounds Troppo to target 20hz and that didn't go too well. The cab itself was trying to understand segmenting and tapering with Hornesp as a TL. I have continued this work in another thread called BR or TL. This has also been resolved with an upgrade to the ZXI10.4D driver in a PR system in that thread. I have continued developing a basic 6 segment TL cab that can be adjusted for tunnel length and SD after build too and will present this once I have finalised a driver for the 40hz challenge, I would really love to compare the reflex system and this TL to see how I feel about the sounds of both. The TL cab can accommodate even my current 7" bass speaker driver, so I can have a control in the experiment with the current ported cab, that driver in a TL, the tiny40s speaker and that driver in a TL
I like the "40 Hz Challenge!" idea. Maybe you'd have an easier time to start with the driver-find small drivers that can generate the necessary minimum SPL and then see what the boxes look like. The Purifi woofer goes low in a relative small box with a lot of SPL, more than 4L though I think. Hey is 4L too big to build into a top hat? A wearable backpack? Maybe you should just use a bass shaker?
In high school year 10, I removed the electronics from a National ghetto blaster and fitted it to the front pouch of my school bag. The speakers, I fitted to a plastic container and fitted inside the side pouches. Stealth reggae inna bag
The 4L has a story behind it too. I am working on another system, mainly for personal use, partially described so far. This is a 2.1 all-in-one with a 10" and two 3.5" FR drivers. This is a twin cab system with the FR drivers and the 40hz box in one unit and the 10" in another with its own power amp. The 10 is there for letting loose and the tiny for intimate. Each bass cab unit capable of driving hard on its own for differing situations. I have never encountered such a setup and would like to take credit as inventor if this is true
The space limitation comes from what I can make on my CNC and printer as I chose the largest that I can afford to work in only section if possible. The smaller unit will dock on top of the larger one and contain all the electronics. The lower unit is basically a musical sub also tuned to 43hz
This will be an instrument amp second and music playback first as this will live next to my smoking and pondering chair with the 10" working hard at daytime and the tiny40s taking over at quiet times. I hope the project makes sense now
Electronics
The only thing left to sort is picking up a line level signal from the headphone amp and converting it to balanced after filtering it for 2.1 for the tiny stage and a balanced pass through for the larger stage. I have started a thread about this in analog line level
You know, saying things like that makes my resolve even stronger! Let a man have his white whale and assist, if you can, will be much appreciated. I bet you will find that a minute spent coming up 1 reason for "can" will be more fulfilling than a 100 "cants". Are we in this for tinkering or not?
I am going to explore this one for a bit, the spl on the graph looks interesting enough, and I think there is a matching PR kit aimed for low tunings in volumes less than 4L
https://www.tb-speaker.com/products/w5-2053
https://www.tb-speaker.com/products/w5-2053
That's cool.
Hexi will show you what and how to design. He and his wife are the sweatest on top of that.
Cheers!
A smaller system will be less efficient- a +3 dB difference means your batteries last twice as long.
That said, speakers with less Xmax and lighter cones are more efficient for a given Sd.
You wrote "It feels like unless I am driving the cab hard, the sound doesn't take on the tuba like flavour which is the tone that I am after."
A bass guitar rig produces sound, rather than reproduces it.
Most bass or tuba's harmonics are 6dB (or more) louder than the low note fundamentals.
When a loudspeaker is driven past Xmax, harmonics are produced, over 100% distortion (second harmonic louder than fundamental) is common in bass guitar rigs, a flat, clean response may not be what you want.
I completely understand about higher efficiency drivers and lowered power requirements for increased battery life. My obstacle has been that such drivers also need much larger cabs, like 35L plus to get down to 40s
My current 7" in 15L with 150wrms does an amazing job as a music sub. It also creates the perfect tones with the bass guitar. And it can play with the soft night touch while retaining very sold bass presence. It's fairly large to make another as a portable
Maybe a different tack
Have a look at this pic. I have dropped the ZR6 signal to 1w. 66db @ 40hz result. Still finding it hard to work out if that would audible on this system less than 1m from the ears. If this is a good result for what I am after, very near field output wise
New recipe - let's start looking at this intimate cab as an alternative to headphones
Tiny tube pre and tiny tube headphone poweramp
Efficient FR speakers running directly from the headphone amp,
Sum and pick up a mono signal
Filter for the sub
Small Class D mono board that can work with 18vdc
ZR6 ina 4L PR system
18v tool battery, multiple sockets
Voltage up converters for the tubes
Balanced 2.1 channel line outs for the aux cab
To fairly uneducated eyes, this is looking like a very viable solution
This system doesn't need to play loud, and I am assuming that the very inefficient driver will actually help keep things quiet while allowing to drive the tube hard with the bass guitar. And that lil amp would again be sufficient for very quiet and close music listening
With the ZR6 in shipping, I have all the parts to pull off something like this, except for the balanced outs and high efficiency FR drivers to connect directly into the headphone out. I can give them max 2L but would prefer to give them a lot less. Maybe JBL boombox type drivers would be worth looking at here. This will be some trail and error
For a small sub, you can figure the inverse distance law of +6dB for each halving of distance to hold up to a very near distance, so at 50cm you could expect ~72dB, at 25cm 78dB, etc.
Most of the LF output around Fb comes from the port or passive radiator, so at very near distances the location of the port and speaker relative to your ears will affect the level distribution.
If the port is rear mounted the distance around the cabinet to your ears is longer compared the driver output, so the LF would have relatively less increase as your ears get closer to the front of the cabinet.
Noted, I was going to place one PR on the front next to the driver and one on the back, with both PR in the same plane, possibly help decouple some of "that" mayhem as they move apart from each other levered by the active driver
https://www.aliexpress.com/item/1005005657595293.html?spm=a2g0o.detail.1000023.9.a7caRMkaRMkaGJ
https://www.aliexpress.com/item/100...KHyQ7liz&utparam-url=scene:search|query_from:
https://www.aliexpress.com/item/100...oLvM5FEG&utparam-url=scene:search|query_from:
They look like they belong on this project
https://www.aliexpress.com/item/100...KHyQ7liz&utparam-url=scene:search|query_from:
https://www.aliexpress.com/item/100...oLvM5FEG&utparam-url=scene:search|query_from:
They look like they belong on this project
Not sure what you mean by "that mayhem as they move apart from each other levered by the active driver", the PR will move the same regardless of the cabinet location.
Placing the driver front center and the pair of PR on the left and right side would also give force cancellation and a built in "loudness contour" as your ears get closer to the cabinet.
Ahem...
I have one of these myself. 67mm mounting depth, to this date it is the lowest mounting depth of any 12" that I have seen:
https://www.blam-audio.com/en/produit/subwoofer-rs12-4/
Edit:
Attached the spec sheet.
I don't know if you can visualise or model this to see what I see
With what I propose, the PR pair will be back to back and close enough to interact with each other, I am banking on this interaction to help the driver out further
KaffiMann, I can quite see you running this driver in a tiny BR. The Vas is huge, and weirdly this is the case for all of these pancake type drivers except for the DS18 SRW. They model very well in tiny ported cabs. With the huge Vas, most of these drivers don't make sense to me as a space saver. I have tried simming all the way up to the $1000+ drivers. Give the SRW10 a go in place of your blam, see what you think
Now to model and make some 40hz test boxes. My table saw and CNC are both ready to be setup
1 - Original 40hz test box that looks like a TL, the long skinny ported one - MDF - model ready
2 - Regular shape ported test box - MDF (could do with further proofing)
3 - 6 segment tapered TL - model ready - foam composite (could do with further proofing)
4 - PR based sub - foam composite (could do with further proofing)
5 - The PR cab for the portable - foam composite (could do with further proofing)
6 - Test box for the FR drivers - foam composite - model ready (could do with further proofing)
Anyone interested in jumping onboard to help really sort and tune one of the foam composite boxes and make it part of a tutorial on foam composite construction? I can do with some collab on the acoustic simming side
1 - Original 40hz test box that looks like a TL, the long skinny ported one - MDF - model ready
2 - Regular shape ported test box - MDF (could do with further proofing)
3 - 6 segment tapered TL - model ready - foam composite (could do with further proofing)
4 - PR based sub - foam composite (could do with further proofing)
5 - The PR cab for the portable - foam composite (could do with further proofing)
6 - Test box for the FR drivers - foam composite - model ready (could do with further proofing)
Anyone interested in jumping onboard to help really sort and tune one of the foam composite boxes and make it part of a tutorial on foam composite construction? I can do with some collab on the acoustic simming side
This is test box 2
4L net internal, 330x252.3x110mm external, 43hz tune. Ready to be made. Plans via PM
Box 5, I have settled on a DSP 2.1 processor and a small 2.1 amp board. 30w +30w + 60w max ratings, so prolly half that clean. That should be ample for the portable, and the DSP will help with quiet night listening
For the stereo full range speakers, first I'll try these purely on how well they visually complement the design
https://www.aliexpress.com/item/328...DFiT1eLO&utparam-url=scene:search|query_from:
Ram Ram Anand. For bass, I am using a DS18 ZR6.4D, a very similar OEM, a DS18 SRW 8, and maybe a CT Sounds Troppo 6.5. I'll pick the better performer for each test box
Full range stereo side drivers depend on project box but mostly DS18 ZXI-4354 for satellite type drivers or Pioneer TS-D65F for desktop larger speakers
Amps on hand to try are most of the models from this link
https://www.diyaudio.com/community/threads/2x150w-amp-module-for-sale.388868/
DSP will be one of the Aliexpress items, I haven't decided on the exact one