Aura 1808 sub build

[milesmilesmiles]

Hi there

I recently was given (!) some aura 1808's and of course now i want to put them in sealed boxes


First time speaker DIY - please forgive any novice errors


I initially did a plan on Speakerbox Lite which brought up some head scratchers...


see images, but the general gist
The calculator determined what seemed to me quite a small box (79.35 litres for a Qtc of 0.5, f3 97.2Hz)
When increase the volume of the cab the f3 increases and the Qtc decreases... how small a cab can an 18" have?
(images are for a slightly bigger box - needed to fit the driver!)

Then i found this calculator Speakerbuilder Pro 2.0

Vb 150l, Qtc 0.7, Fb 52.12

The results seemed to "feel" more correct... also as i made the Vb greater, the Qtc and Fb lowered... this is correct right?

Are these both viable options, or is one of these not functioning correctly?

 

[milesmilesmiles]

i also found this link
Aura 1808 Qtc=0.707

for a Qtc of 0.707, a Vb of 1.54 cu ft (43 litres!)

 

[GM]

Hmm, Hornresp

---

'says' 50 L, 43 L =0.75 Qtc.

To answer your Q though, drivers can in theory be squeezed up till there's nearly zero rear chamber for compression horn loading [2.0 Qtc], which is one of the cab alignments this driver is designed for.

GM

 

[Brian Steele]

That driver has a VERY low Qts. You'll need to use one of the higher-order alignments to get the best from it. Like an extended bass shelf or 6th order bandpass system.

 

[GM]

Yeah, the pair I did for a long gone now neighborhood cinema was EBS.

GM

 

[snax]

Hi Milesmilesmiles,

Not sure of the purpose of your sub (home, car, pro).

I also have a pair of Aura’s and I have been digging around as to what the best enclosure for them is for home use. I am looking a perhaps a di-pole or horn enclosure but will add the information I have just to help you along.

For all the hype and rave reviews there seem to be little in the way of definitive enclosure design to make the most of its Xmax and Qts. I have a quote from Tom Danley as to the potential, “this would be scary powerful in a home” which gives me confidence that I’m on the right track.

I know GM has also been instrumental in all the Aura discussion so would be someone to listen to for experience. I think he supplied the attached 1808.aks.txt which is the output from Hornresp.


Forgive the subjective nature of this next bit as this is just a dump of information.

Found this on Youtube - YouTube

As you documented above an image taken from the same website Aura 1808 Qtc=0.707


The Aura 1808 was used in the Aura RS-8.1 subwoofer but I am unsure as to its design as they mention port but it looks more like a horn to me. Brochure and images, I have found attached.

Enclosure designs:

"You have mentioned a sealed box which should be fairly self-evident for construction however a horn should give you 10-15DdB more than using the direct radiator by itself".

Angeloitacare from this forum was looking at making a tapped horn enclosure but I can not find any designs that he completed and the thread ‘tappers’ off. Sorry for the pun....

ROAR 18 as a design although it has a vocal critic as to the quality of sound. Martinsson’s website has measurements but I do not have the experience of determining good from bad. It is also getting a bit big but not MASSIVE at 600mmx960mmx960mm (WxHxD) - 553dm3 external volume. Site is here Martinsson's Blog

 

[weltersys]

The Aura 1808 was used in the Aura RS-8.1 subwoofer but I am unsure as to its design as they mention port but it looks more like a horn to me.

Snax,

I recognize my almost 3 decade old "calculations" on the side of the spec sheet you posted :^).
The RS-8.1 subwoofer is simply a bass reflex box with a very large port flared at both ends to reduce port turbulence, good idea with 18mm Xmax potential.
The Fb of 25 Hz with such a large port exit (around 13 x 20 inch) requires the port to use a substantial portion of the 915 x 572 x 762 mm (36 x 22 1/2 x 30 inch) cabinet volume.

The Roar 18 is quite a bit larger than the RS-8.1, and has around a 10 Hz higher Fb, with response dropping at around 24dB per octave below 40 Hz. For home use I'd be inclined to use the smaller, deeper RS-8.1 bass reflex approach, loose a little sensitivity for extended low frequency.

Art

 

[milesmilesmiles]

Hi Milesmilesmiles,

Not sure of the purpose of your sub (home, car, pro).

thanks for the info Snax

It will be for a medium sized control room for monitoring, and if that fails to integrate, then will be at home in the lounge room


I am a beginner speaker DIYer, but happy to put the work in to get something useful for me.

The goal is articulate bottom end and relatively small cab size - i don't need high (or even medium) SPL

My thinking now is that i go for 2 small sealed boxes (110 litre-ish), and tweak with some EQ to get it happening (20-80Hz)

A concern is exceeding the maximum excursion... any thoughts here?

thanks for the help!

 

[GM]

HR 'says' net Vb Vs 800 W Xmax power is ~86.4 L with minimal damping, i.e. just enough to remove any 'hollow' sound.

GM

 

[milesmilesmiles]

HR 'says' net Vb Vs 800 W Xmax power is ~86.4 L with minimal damping, i.e. just enough to remove any 'hollow' sound.

GM

OK great - thanks GM!

i'm putting a windows emulator on my mac this weekend so i'll be able to run my own sims shortly!

Miles

 

[GM]

You're welcome!

Cool! Use file/import to open/view/save/copy/whatever the file.

GM

 

[snax]

Hi Art,
It is confirmed, I am a collector of rare antiquities.
And to think my wife called them trash… how disappointing.

 

[weltersys]

The goal is articulate bottom end and relatively small cab size - i don't need high (or even medium) SPL

My thinking now is that i go for 2 small sealed boxes (110 litre-ish), and tweak with some EQ to get it happening (20-80Hz)

A concern is exceeding the maximum excursion... any thoughts here?

Milesmilesmiles,

The Aura 1808 is unusual in many respects for a very high excursion subwoofer, one being the "maximum excursion" of 50mm peak to peak is only 12mm more than the linear excursion. It would be a good idea to push the cone by hand (use two..) to it's maximum excursion and determine whether the voice coil or former bottoms out with a click, or the cone suspension, (the surround or spider) reaches maximum excursion first.

If the voice coil bottoms out before the suspension reaches maximum excursion, it can be damaged easily,and almost instantly.
If the suspension reaches the end of it's "stretch" before the coil bottoms, it should take a fair amount of abuse before tearing or deformation.

Placing a fabric grill at about 20mm in front of the surround would give you a visual indication of when Xmax has been exceeded.
At "medium" SPL the grill won't ever be touched .

Art

 

[milesmilesmiles]

Milesmilesmiles,

The Aura 1808 is unusual in many respects for a very high excursion subwoofer, one being the "maximum excursion" of 50mm peak to peak is only 12mm more than the linear excursion. It would be a good idea to push the cone by hand (use two..) to it's maximum excursion and determine whether the voice coil or former bottoms out with a click, or the cone suspension, (the surround or spider) reaches maximum excursion first.

If the voice coil bottoms out before the suspension reaches maximum excursion, it can be damaged easily,and almost instantly.
If the suspension reaches the end of it's "stretch" before the coil bottoms, it should take a fair amount of abuse before tearing or deformation.

Placing a fabric grill at about 20mm in front of the surround would give you a visual indication of when Xmax has been exceeded.
At "medium" SPL the grill won't ever be touched .

Art

Thanks Art

Good to know - will try

I have to say that as a first time poster on DIYaudio, this has been an amazing and very helpful resource for me - thanks to you and all the other people in this thread!

I will post some pics when it is nearing completion

Miles

 

[Jack Hidley]

With the 1808, the lower spider will hit the top of the motor first. It is impossible for the end of the coil the hit the bottom of the gap.

If you want a small box, make it sealed, apply a lot of eq and use a 1.5kW amplifier. You'll need the voltage swing.

 

[milesmilesmiles]

With the 1808, the lower spider will hit the top of the motor first. It is impossible for the end of the coil the hit the bottom of the gap.

If you want a small box, make it sealed, apply a lot of eq and use a 1.5kW amplifier. You'll need the voltage swing.

ok great - thanks Jack!