Hello everyone,
I've been thinking about building an Onken enclosure for some time now. Recently I came across two vintage 15 inch czechoslovakian Tesla ARO 942 cinema woofers, which I just could not resist. The problem is i'm not sure if they'll work well in this type of cabinet. Originally they were mounted in a big bass reflex box (as the one shown here).
It's really hard to find a comprehensive set of parameters. All I've found is:
Diameter [mm]: 390
Depth [mm]: 231
Impedance [ohm]: 30
Power [W]: 15
Peak power [W]: 30
Fs [Hz]: 24
Frequency range [Hz]: 24- 4000
Efficiency [dB]: 100
Weighy[kg]: 10.50
[Qts]: 0.4
[Vas]: 226
[Xmax +/-]: 4.50 mm
Maybe someone measured the speakers and could share the results (as the ones shown above are not 100% certain). Or someone actually put them in an Onken box.
Any help appreciated
I've been thinking about building an Onken enclosure for some time now. Recently I came across two vintage 15 inch czechoslovakian Tesla ARO 942 cinema woofers, which I just could not resist. The problem is i'm not sure if they'll work well in this type of cabinet. Originally they were mounted in a big bass reflex box (as the one shown here).
It's really hard to find a comprehensive set of parameters. All I've found is:
Diameter [mm]: 390
Depth [mm]: 231
Impedance [ohm]: 30
Power [W]: 15
Peak power [W]: 30
Fs [Hz]: 24
Frequency range [Hz]: 24- 4000
Efficiency [dB]: 100
Weighy[kg]: 10.50
[Qts]: 0.4
[Vas]: 226
[Xmax +/-]: 4.50 mm
Maybe someone measured the speakers and could share the results (as the ones shown above are not 100% certain). Or someone actually put them in an Onken box.
Any help appreciated
Greets!
FYI, Google Chrome says the reflex cab page is unavailable.
You could/should measure your driver’s specs.
Otherwise, using what’s available and guessing/extrapolating to get the rest for simming purposes based on other brands of similar spec vintage 15” cinema drivers:
Sd = 860 cm^2
Qes = 0.416
Qms = 10.274
Le = 1.3 mH
Regardless, no, the vents will be too long unless the specs are radically different.
What you can do though is build a high aspect ratio reflex [aka MLTL] that is as easy to build, yet will work acoustically more like the Onken was believed to than actually does, it just won’t be as cool looking, so some folks have been know to add fake vents……..
Using the Onken calculator’s ~241.57 L [8.531 ft^3] net/24 Hz Fb alignment + 0.5 ohms added series resistance for wiring, etc. to get a baseline ‘default’ alignment for discussion purposes:
L = 152.4 cm [60”]
CSA = 2397.21 cm^2 [371.57”^2] = recommend ~ 62.28 cm [24.5”] W x 38.49 cm [15.2”] D
zdriver = 63.5 cm [25”]
zport = 121.92 cm [48”]
dport = 12.7 cm [5”]
Lport = 5.08 cm [2”]
All dimensions inside [i.d.] and approximate. Sim includes minimal damping of the top, one side and back of the cab. Of course this is just one of many possible solutions, it
The minor ‘ringing’ [‘bump’] at Fb is typical for the Onken and many vented alignments to this day, but tuning lower [longer vent] and/or a little more damping and/or slightly reducing the cab’s CSA will flatten it if desired.
All that said, with a 30 ohm driver, what amp/specs are you planning to use? If it’s a high output impedance, then the cab may ideally need to be even bigger.
GM
FYI, Google Chrome says the reflex cab page is unavailable.
You could/should measure your driver’s specs.
Otherwise, using what’s available and guessing/extrapolating to get the rest for simming purposes based on other brands of similar spec vintage 15” cinema drivers:
Sd = 860 cm^2
Qes = 0.416
Qms = 10.274
Le = 1.3 mH
Regardless, no, the vents will be too long unless the specs are radically different.
What you can do though is build a high aspect ratio reflex [aka MLTL] that is as easy to build, yet will work acoustically more like the Onken was believed to than actually does, it just won’t be as cool looking, so some folks have been know to add fake vents……..
Using the Onken calculator’s ~241.57 L [8.531 ft^3] net/24 Hz Fb alignment + 0.5 ohms added series resistance for wiring, etc. to get a baseline ‘default’ alignment for discussion purposes:
L = 152.4 cm [60”]
CSA = 2397.21 cm^2 [371.57”^2] = recommend ~ 62.28 cm [24.5”] W x 38.49 cm [15.2”] D
zdriver = 63.5 cm [25”]
zport = 121.92 cm [48”]
dport = 12.7 cm [5”]
Lport = 5.08 cm [2”]
All dimensions inside [i.d.] and approximate. Sim includes minimal damping of the top, one side and back of the cab. Of course this is just one of many possible solutions, it
The minor ‘ringing’ [‘bump’] at Fb is typical for the Onken and many vented alignments to this day, but tuning lower [longer vent] and/or a little more damping and/or slightly reducing the cab’s CSA will flatten it if desired.
All that said, with a 30 ohm driver, what amp/specs are you planning to use? If it’s a high output impedance, then the cab may ideally need to be even bigger.
GM
Attachments
Thanks for the reply.
The link to the original cabinet photo is:
ReproMania.NET | Tesla | Reprosoustavy | AKR 303
Being a single driver guy i wanted to try something new. Now i'm beginning to see how convenient the full range solution is
I'll have a closer look at the MLTL, but first will have to measure the driver (as soon as i'll get the necessary equipment). Also maybe I should consider the original enclosure.
As for the amplification i'm going to biamp -- SS for the bass and a SET amp for the rest. Was thinking about using a transformer to lower the speakers impedance, but don't know how is it going to affect the sound (if at all).
Is there any type of amplifier particularly good for the low frequency drivers (i'm familiar with soldering iron so DIY is definately an option)?
The link to the original cabinet photo is:
ReproMania.NET | Tesla | Reprosoustavy | AKR 303
Being a single driver guy i wanted to try something new. Now i'm beginning to see how convenient the full range solution is
I'll have a closer look at the MLTL, but first will have to measure the driver (as soon as i'll get the necessary equipment). Also maybe I should consider the original enclosure.
As for the amplification i'm going to biamp -- SS for the bass and a SET amp for the rest. Was thinking about using a transformer to lower the speakers impedance, but don't know how is it going to affect the sound (if at all).
Is there any type of amplifier particularly good for the low frequency drivers (i'm familiar with soldering iron so DIY is definately an option)?
You’re welcome!
Thanks!
Yeah, but the trade-offs can be a bit much for other than a ‘girl and a guitar’ music.
‘Sounds’ like a plan. Don’t recall ever trying to ‘convert’ a high ohm driver, just coupled them to a ~matching impedance one.
Well, with around a 0.4 Qts motor, it’s ~ ideal for SS or PP tubes that have a ~1/8 – ¼ ohms max of output impedance, so lots to choose from, though WRT SS, DF > ~80-100 should normally be avoided since it implies too much –fb and of course needs to be Class A-B to at least 10 amps and preferably 100% Class A unless the XO point is fairly low.
Anyway, when it comes to amp, wire, selection there’s about as many opinions as there are available products, so in the end you’re really on your own.
GM
Thanks!
Yeah, but the trade-offs can be a bit much for other than a ‘girl and a guitar’ music.
‘Sounds’ like a plan. Don’t recall ever trying to ‘convert’ a high ohm driver, just coupled them to a ~matching impedance one.
Well, with around a 0.4 Qts motor, it’s ~ ideal for SS or PP tubes that have a ~1/8 – ¼ ohms max of output impedance, so lots to choose from, though WRT SS, DF > ~80-100 should normally be avoided since it implies too much –fb and of course needs to be Class A-B to at least 10 amps and preferably 100% Class A unless the XO point is fairly low.
Anyway, when it comes to amp, wire, selection there’s about as many opinions as there are available products, so in the end you’re really on your own.
GM
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