deep output from very small drivers and enclosure?

[botnet]

Hello,

I came across a small driver (Tang Band W3-2108) and wanted to try producing a very compact enclosure capable of deep (20-120hz) flat bass. My plan was to 3d print the enclosure so construction complexity is a non-issue.

Is such a thing possible?

 

[WaVeInFoRm]

with that driver you can get flat to 20 at about 4 db

 

[botnet]

with that driver you can get flat to 20 at about 4 db

what about something like a tapped horn? seems like I could get good, low output in a modest enclosure.

If flat isn’t possible i can’t EQ

 

[botnet]

If flat isn’t possible i can’t EQ

I mean to say I can* EQ 🙂

 

[wonderfulaudio]

At first glance the driver is too small for bass and sensitivity is too low at 77dB. Whats the target application?

Tapped horn and small enclosure don't go well together.

 

[chris661]

A 3" driver moving 10mm p/p will produce 65dB at 20Hz in a sealed box.
Piston Excursion calculator

I don't even think that would even be audible, unless you had several in very close proximity.

A clever box may help a little, but it would be far more impressive to most people to have 60Hz and upwards at high volumes, than to have a little driver trying to produce 20Hz and not being able to get close to satisfying levels.

Chris

 

[wolf_teeth]

TB RBM drivers are absolutely amazing, especially the 8". And no- you'd likely want to PR load the smaller ones. IIRC, the sensitivity is not 77, but 80 at 2.83V/1m. They are 4 ohm drivers, so the 77 at 1w/1m is not such a reliable rating.

I've heard a couple of the smaller units in both PR and vented enclosures, and they really do surprise the uninitiated.

Later,
Wolf

 

[botnet]

which is why tapped horn is attractive, 65db sealed means half the output is lost right?
i’m not fixated on 20hz as the low end but I am curious to learn what is possible.

 

[botnet]

TB RBM drivers are absolutely amazing, especially the 8". And no- you'd likely want to PR load the smaller ones. IIRC, the sensitivity is not 77, but 80 at 2.83V/1m. They are 4 ohm drivers, so the 77 at 1w/1m is not such a reliable rating.

I've heard a couple of the smaller units in both PR and vented enclosures, and they really do surprise the uninitiated.

Later,
Wolf

what is PR load?

 

[Windforce85]

This is academic problem or real world issue? If the latter, 20 Hz is totally unnecessary, why you want to reproduce infrasounds using 3" driver? 50 Hz corner for sealed cabined is already very deep for such a small driver. What sound level is needed? Is it PC speaker for work in the office? Don't count for more with it.

 

[botnet]

winforce, I was thinking home theatre; was looking to get something great out of this little driver and was hoping that the 3d-printer would give me some construction advantage by unlocking any complex shape.

 

[scottjoplin]

If you are after portrayal of LF sound effects, have you thought of a seat shaker?

 

[Windforce85]

botnet, loudspeaker driver needs to linearly displace fairy large amount of air physically in order to reproduce lowest bass loudly and with authority. This is what you need for home theater - driver with big membrane and big stroke for sheer, forceful displacement. Volume of displaced air is equal to membrane area times its excursion. It is simply not possible to do for small driver. Of course it can try but sound level will be very low and hearing level nonlinearity (follow Fletcher Munson curve explanation) causes 'no bass at all' effect. Magical boxes (high order acoustical alignments) like horns, band-pass, TL-s etc. can raise bass SPL considerably but they will work efficiently on much higher frequencies than on 20Hz becouse box size required will be larger than a wardrobe.. It is a lot harder to reproduce bass in HT than bass in music tracks becouse most music does not go lower than 40 Hz so proportionally smaller boxes and displacements are needed. For starter you can experiment with 8-inch drivers and try to limit low corner requirements (-6 dB) to 30 Hz. In small room it is more than sufficient becouse listening rooms will usually add sound pressure for lowest bass thanks to room gain effect.

 

[scottjoplin]

If space is the main issue, but you can put a hole in a wall, IB will get you the lowest.

 

[chris661]

If space is the main issue, but you can put a hole in a wall, IB will get you the lowest.

IB will gain efficiency down low, but you don't get any more output than a sealed box.
They both have the same mechanically-limited output, it's just the IB gets there with less power.

Chris

 

[botnet]

would someone be able to help me plug the right values into hornresp so I can see what might happen with a tapped horn configuration?

 

[chris661]

Double click on the "Sd" field, and you'll be able to enter the more commonly-found parameters for a driver.

Chris

 

[botnet]

On a tapped horn, my understanding is that one side of the speaker radiates into the horn, while the other side radiates at the mouth. The combined radiation leads to added output, because the wavefronts meet at the mouth at the same time due to a precisely calculated horn length.

Why not have both sides of the driver radiate into separate horns with a shared mouth? Would that give me the added output needed from this small woofer?

 

[chris661]

The problem isn't that of horn-loading, but that of physics. Hoffman's Iron Law states:

- Small size, high efficiency, low frequency extension - pick any two.

For my PA system, I chose 40Hz extension and then played around with efficiency vs size to get something I was happy with.
For a small portable speaker, I'd set an external size and then balance efficiency vs low-frequency extension.


My recommendation is to set off with your design goals, and then find the optimum way of achieving those goals.
If your goal is 20Hz at 100dB, the 3" driver only needs 35dB of help from the cabinet...

Chris

 

[TBTL]

If you want maximum output for a given enclosure volume, go for a small sealed box and use a woofer with a strong motor and a large air displacement capability. If enclosure size is not an object, other box types can be more efficient, though they will be larger.