Cheap drivers in cheap O.B. system
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 …
I just bought these drivers. Do you have any pics of what you did? I'd love to put them onto open baffles but they don't sim as well as i would have hoped. They look like well made drivers tho and i'd like to try them out. I am not limited to open baffle and wondering what to do with them.
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 !
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.
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
Neat, how do they compare to the bigger speakers you have?
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.
Hi, this project seem like fun. I have never build OB design before and would like to try your design. Can you post detail of your ns6 crossover design? And by any chance you are from Montreal?
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
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