Cheap drivers in cheap O.B. system

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Hi everybody,

I have recently bought in the USA 4 cheap Aurasound NS6-255-8A semi-fullrange drivers (10 US dollars each !).

I choose them because I knew I could easily use them in O.B. (QTS = 0.55, Fs = 55 Hz, and a relatively good Xmax).
I also saw in the french website : petoindominique.fr, that this driver shall be used at its best in O.B.

In addition, I could presume that, with the Aurasound Neodymium radial magnet structure and its mechanical depth, it will help to have a tight membrane control; and I read that it reduces the distorsion in the midrange.

I did not want to take too much time nor money for building simple O.B. structures.

Eventually, I found cheap foldable thick cardboard / fabric drawers in my town.
I took 2 sizes (2 pces = 32 x 32 x 14 cm., & 2 pces = 32 x 32 x 32 cm.).
They were easy to cut, and in few hours, I was over with the assembly.

In the 2 big ones, I mount in each a NS6 filtered at 500 Hz. As from Fs to about 500 – 1000 Hz, its efficiency is lower of about 3 to 4 dB ; and as the basses are weaker in O.B., I like better to add them to the final system.
In the 2 little ones, I mount in each a NS6 filtered at 4'000 Hz. If not, too much distorsion arises in the upper range.
I have fixed old rubbish carpet on the sides (inside faces) in order to add density / weight and to avoid vibrations.

For the tweeters, I use 2 old Fostex textile domes FT25D, which efficiency matches perfectly the 4 Aurasound NS6 drivers.

The cost of filtering parts are higher than the 4 Aurasound total cost, but that cannot be avoided.
To reach a better QTS value of about 0.7 - 0.8 for the NS6, I have chosen two ways.
One, in adding a Resistor in serial with the driver.
The second, in adding in parallel with the driver, a serial Resistor – Capacitor – Inductance filter (that I have found in the above french website).

The listening / musical result is really amazing :

The midrange is present and clear but remains natural, and has very low distorsion (even at loud levels).
The basses are "huge"; and I could not believe this before listening to the achieved O.B. sytem. Thus for many reasons : little size of these drivers and use of O.B.
They keep a lot of power without annoying distorsions ; I can easily reach the sound pressure that I have with my semi-fullrange Phy-hp high efficiency drivers.

I will, as soon as I can, post some pictures of my O.B. drawers !!!

Musicalement vôtre …
 
Hi Zilla,

as I said before, I will send pics as soon as I can ...
Nevertheless, I like very much O.B. sound ... May be you will not like it, as it is anyway a "particular" sound.

If you want experiment other enclosures with the NS6, I do not know how they sound in various boxes ?
But, if it can helps you, in the french website petoindominique.fr, there are specials pages which indicate the + & - to use a specific driver in such enclosure or not (closed, BR, OB, and so on ...).

I am really happy with the sound of my cheap O.B., but my opinion is said knowing the little size and the low cost of my DIY system. This also for a domestic listening in a living-room of 22 square meters.

Audiophilement vôtre !
 
Hi again,

Some pics of these cheap O.B. drawers.
The second tweeter (under the Fostex) is not in use, because it has a little too much efficiency; but they are very good for the price (SB TWD25NH05 textile dome at 5-6 US dollars each).
I have ordered them together with the Aurasound NS6.
 

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Video avaible

I have posted a vid on Youtube.

The sources are :
Classic Denon cd player with an external NonOS DAC from Pacific Valve.
Full-DIY passive preamp with Elna stepped attenuator from Goldpoint, and with siver wires.
Half-DIY T-Amp done with audiophiles : T-Amp module, dedicated PSU module and R-Core voltage transformer.

Aurasound NS6 drivers in cheap Open Baffle - YouTube
 
Good question Zilla ...
If I compare only on cost rate, this little cheap OB sytem wins, as my main system costs about 10 times more !
And I cannot honestly declare that my O.B. with Phy-hp & free-air subwoofer is 10 times better !
See about the composition of my main system my website and my threads (with pics) in the Subwoofer section of this forum.
But in the end, it is normal that my big OB system wins in terms of musical listening pleasure !
I would say it gives 2 or 3 times more pleasure that the cheap OB system.
The contrary should be strange !
In addition, my big O.B. is driven by a good valve preamp. (M.A.D.) and a remarkable low cost SEOTL ClassA amp. kit (Transcendentsound) which gives more air and "3D" (than my T-Amp) in the incredible soundstage that open baffle basically offers.

But again, for the price and size, these Aurasound gives powerful basses and very musical midrange (when filtered int he highs).
And I am sure that the inventive Aurasound Neodymium radial magnet structure (see the PartsExpress vid inYouTube) is responsible for such good performance.
 
Founder of XSA-Labs
Joined 2012
Paid Member
Hi again,

Some pics of these cheap O.B. drawers.
The second tweeter (under the Fostex) is not in use, because it has a little too much efficiency; but they are very good for the price (SB TWD25NH05 textile dome at 5-6 US dollars each).
I have ordered them together with the Aurasound NS6.

This is awesome, hilarous use of those cloth covered cardboard folding totes we use to keep kids toys in. They fold up too and you have a portable OB system.;) I saw those drivers too and wondered how good they were- sounds like they ROCK! What about active EQ and biamping and skipping all those messy coil caps and resistors? Nicely done!:)
 
Hi Sagamotto,

I live in Geneva / Switzerland.
As I said before, the first thing to do before using the Aura NS6 in OB, is to set their QTS near to 0,7.
I made it 2 ways.
The cheapest one (in the deeper open box) with a serial R of about 2R2; which makes with the added value of R coming from the inductor of the lowpass filter, a total value of about 3R. The LP filter at 6dB/oct. has a value of 2,5 mH.

The second way (in the less deeper open box, with the tweeters) is much expensive. It is a serial R - uF - mH filter set in parallel with the driver. I have done it, because Mr. Petoin advices it in his famous french website : petoindominique.fr. This filter should linearize the impedance curve of the driver.
The values used are : 10,1 mH, 832,2 uF and 4R4; again, with the added R coming from the inductor , we reach a R of about 6R.
The Lowpass filter at 6dB/oct. has a value of 0,68 mH.

Hope it helps
 
Hi xrk971,

Thks for the smilies, ;-))

I agree with you, these little cardboard/cloth totes OB should work great with active EQ & normal or biamping.
As I explained before to Sagamotto, for the 0,7 - 0,8 QTS, if you use a single R value instead of the complex R-C-I filter, you should spare some place.
But anyway, the folding aera of the drawers I have bought, is the front face where the Aura NS6 (and tweeters) are mounted. So it should not be possible to fold them again.
We would have to create other folds and think about a new folding manner.
:hohoho:
 
Founder of XSA-Labs
Joined 2012
Paid Member
Yes, the cost of your caps and inductors is probably several times the cost of the aura drivers, and then some - so the term cheap OB may be pushing it. This is why I was wondering if going with an active x-over and bi-amping would be more economical. T-amps are cheaper than big inductors! Can you explain why you have what appears to be 2 tweeters and another driver on the top box? Can this be done with say the Aurasound in the lower box and maybe a full range like a vifa tc9fd on top? To really make system cheap, use only single low pass coil on bottom, and single high pass cap on top? That way, the costs of the cap and coils is at least less than cost of drivers.
 
Yes, I also agree, those are the biggest cap and coil I have ever seen. I have just received four t-amp the other day and was planing to use as bi amping as well. So how can t-amp be made to use for active drive? Btw, I got the lepai tda-2020+ amp from Solen, they cost less to buy then to built.
 
Founder of XSA-Labs
Joined 2012
Paid Member
Yes, I also agree, those are the biggest cap and coil I have ever seen. I have just received four t-amp the other day and was planing to use as bi amping as well. So how can t-amp be made to use for active drive? Btw, I got the lepai tda-2020+ amp from Solen, they cost less to buy then to built.

You are on the right path with all your t-amps. Maybe use car audio crossover like this one? Amazon.com: Power Acoustik C-3184 3-Way Electronic Crossover: Car Electronics The Lepai's should work well, great amps.
The bonus with the active cross over is that you can adjust cross over points and amplitude.
 
Hi Loud,

as I have already explained , I find that my OB system gives good basses in domestic use, for such "small" drivers.
There are 2 mains reasons for this (see my previous threads, or explanations in the Youtube vid) :
1) the Qts value has to be higher than the original one, try to reach between 0,7 - 1,0.
2) I have also boosted the bass register with the add of the biggest open box which is filtered at about 400-500 Hz.
Because if you look at the frequency curve of Aurasound, we can see that the bass output is lower about 2 or 3 dB. Inside a car, for example, its OK, as we know that the basses are boosted with 3 to 6 dB due to the narrow volume inside a car.

Hope it helps.
 
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