Need suggestions for Open baffle Design

[Sumanta]

Wow! Some more OB users!
Great going!
Kannan, you can read post of Dr. Jaudere and and mine for our designs which were tried, used and have satisfied listeners.
Mine is definitely not, and so probably is of Dr. Jaudere on the point of use of simulation.
Doctor had used single driver Ahuja 12 FRX with a clever cabinet design. I liked his logical approach and that is well recorded in his posts here.

I did my designed two ways,
1) One as 1 baffle with 2 drivers (active and/or passive)
2) Two baffles two drivers (active and/or passive).
I have never used any simulations, but only mine and my listener's impressions to measure the success of the design. All designs are a compromise by the way.

I suggest listen to your ears/mind once you are done and happy with your simulations.
Music, from its production to listening has so many variables and are subjective in their nature. Plus their attributes that we correlate as sound and its reproduction quality, I have come to believe everyone is right in their path. I try to listen music in my way for myself and hence try to be ready to tackle innumerable variables to sound music in my way (which like everybody else I believe is quite a transparent one).

In this journey I found Active OB with SET amp for mid/high and SS for low end gave me a versatile music player. And this system is very good to play in apartments without any room treatment.

 

[Ravindra Desai]

Welcome back @Sumanta !
You will be an asset in this thread.

Regards,

Ravindra.

 

[Hari Iyer]

I did a quick simulation of the Ahuja-12FR driver and even after trying very hard could not take the response roll-off below 100Hz. This is with the published parameters of this driver from their website. IMO, you will for sure require a sub-woofer when using the Ahuja with OB. One good feature of this driver is the roll-off begins at around 1KHz and even with the baffle step support the response is just -10dB down at 20KHz which will be very pleasing to listen with gradual roll-off for 10 octaves.

-6dB is 53Hz and -10dB is 40Hz.

One major point to be noted with this driver is its a low compliance driver and the cone motion would be quite stiff. So this could work as an advantage for OB as there is no back pressure to damp the motion of the cone and hence the box compliance (so to speak) will be very high (low stiffness). The placement of this speaker away from the front wall will dictate the overall tonality of the speaker. One should try and make one from my simulated values.

The baffle was with golden ration of 1:2 which is 49cm (19.29")wide and 160 (63")cm high which should be okay with largish room size.

 

[Hari Iyer]

Very nice Hari. With a bass assisted Driver there is no need to cross below 120 Hz. I think a 2 way OB with Ahuja drivers will rock !

I will rather go only single driver and check if 2-way is required after listening. There is always a possibility of adding a active TL-sub later one each per channel (if space permits). The idea is to avoid passive crossover which can cause phase mismatch errors.

 

[Hari Iyer]

The idea is to run FR unfiltered and biamp the bass driver through active XO. Both OB

I will rather prefer a TL sub rather than a OB sub to get response below 30Hz, deep and undistorted. Will require less real estate too.

 

[Ravindra Desai]

I did a quick simulation of the Ahuja-12FR driver and even after trying very hard could not take the response roll-off below 100Hz. This is with the published parameters of this driver from their website. IMO, you will for sure require a sub-woofer when using the Ahuja with OB. One good feature of this driver is the roll-off begins at around 1KHz and even with the baffle step support the response is just -10dB down at 20KHz which will be very pleasing to listen with gradual roll-off for 10 octaves.

-6dB is 53Hz and -10dB is 40Hz.

One major point to be noted with this driver is its a low compliance driver and the cone motion would be quite stiff. So this could work as an advantage for OB as there is no back pressure to damp the motion of the cone and hence the box compliance (so to speak) will be very high (low stiffness). The placement of this speaker away from the front wall will dictate the overall tonality of the speaker. One should try and make one from my simulated values.

The baffle was with golden ration of 1:2 which is 49cm (19.29")wide and 160 (63")cm high which should be okay with largish room size.

Thanks Hari for your time and efforts!

I cannot but wonder how an OB project with Ahuja 12FRX makes sense.
It needs 3feet space from the back and side wall, needs a helper woofer and so another amplifier, and not to mention a crossover.

Compare that against a ported enclosure that occupies much less floor space, does not need helper woofer and it gets as close to a purist system as possible.

But if one is stuck with a non- box approach, then it can't be helped.

Regards,

Ravindra.

 

[Ravindra Desai]

I think you should try one. OB experiments are pretty light on pocket, effort and time. Hari himself was a disbeliever and I almost coaxed him with his wonderful Ruski driver and he started with cardboard !

But simulation shows -3db around 80Hz. This confirms need for a helper woofer and complicates things.
The purpose for which I picked Ahuja 12-FRX gets defeated.

Regards,

Ravindra.

 

[Ravindra Desai]

I re-checked on the -3db cut-off and its close to 100Hz!

Do you know what the best part of this all is?
Even the driver manufacturer is un-aware of its driver capability in ported enclosure!

Regards,

Ravindra.

 

[Hari Iyer]

I re-checked on the -3db cut-off and its close to 100Hz!

Do you know what the best part of this all is?
Even the driver manufacturer is un-aware of its driver capability in ported enclosure!

Regards,

Ravindra.

I shall do a ported simulation after calculating box dimensions from winisd and post for a comparison.

 

[Ravindra Desai]

I shall do a ported simulation after calculating box dimensions from winisd and post for a comparison.

Thanks Hari!

I am not promising, but I will post the measurements here, soon.

Regards,

Ravindra.

 

[Sumanta]

And I know my friend who put off a world famous Indian brand's speaker active bass system and use his earlier OB bass. that made him happy after all trials.
Ravindra and Hari, simulation is good, but we all ultimately listen with our ears. It is only a request, listen to OB bass before you decide. Do not go by mere values of 20/30/35 Hz that a speaker system can go down to or by their depth (as the paper says). Listen them in real in your room. Decide for your environment by your own ears. I realized, the more critical I become of sound reproduction attributes and hence on the end sound product, the more variables I bring on the table to make it more individualistic. Hence you all might have noticed I hardly talk technical now as the routes are individual as well.

One more point for the baffle width consideration, I did use 1/4 wavelength to consider the half baffle width for OB (including side wall), it worked. Simulation, as usual I didn't. For 12FRX, 400mm width with 150mm side wall on both side should be very good. I think I used the same with tapered up side walls on the first design.

Note - Ahuja passives are not that bad and cost around 1800 (if I remember correctly) each. Use AS15 and 12FRX with this Ahuja crossover, collaboratively they can work quite well. Until you listen to well made actively crossed over system with the same drivers.

 

[Kannan_madhu]

Thank you friends , thats a great help i will be going forward with this project next week
Hari Could you please do a simulation of AS15-x200 on the baffle you suggested
http://www.ahujaradios.co.in/speakers/professional-pa-speakers/as15-x200.html

 

[Hari Iyer]

Thank you friends , thats a great help i will be going forward with this project next week
Hari Could you please do a simulation of AS15-x200 on the baffle you suggested
http://www.ahujaradios.co.in/speakers/professional-pa-speakers/as15-x200.html

Are you looking for two drivers in one baffle?

 

[Hari Iyer]

Yes, he is. FR at ear height and bass near the floor, both centered to baffle.

Ok, don't know why, centring of drivers on the baffle gives deep notches in mid range response due to baffle step in the Basta simulator. I shall prefer the FR to be off centered and only the 15" woofer to be centered for a balanced smooth response.

 

[Kannan_madhu]

Are you looking for two drivers in one baffle?

Yes , two of them in the same baffle , if we use a filter and cut the mid to 15 will it create the notch ?

 

[Hari Iyer]

Yes , two of them in the same baffle , if we use a filter and cut the mid to 15 will it create the notch ?

The notch is a acoustic phenomenon due to position of driver on the baffle and cannot be corrected passively.

 

[Lionx]

I will rather go only single driver and check if 2-way is required after listening. There is always a possibility of adding a active TL-sub later one each per channel (if space permits). The idea is to avoid passive crossover which can cause phase mismatch errors.

I am currently running this way, FRX as crossoverless OB (JE labs design) and a TL sub for bass assistance. But I do get a feeling that sub is not needed for fatigue free listening and keep on experimenting with switching on/off the sub. I am planning for a diy class A for this now.

 

[Hari Iyer]

Yes , two of them in the same baffle , if we use a filter and cut the mid to 15 will it create the notch ?

Here you go. These are quick simulation to give you an idea of what to expect at a high level. Efforts will be required to get a smooth overall response without cancellation when both drivers are combined. I have shown the individual driver response and also the resultant.
Cheers,

 

[Lionx]

Share a picture here. You made beautiful OBs. Everyone should see them.

Just a try to imitate the famous design from this,
http://jelabsarch.blogspot.com/2012/06/open-baffle.html?m=1

 

[Hari Iyer]

But simulation shows -3db around 80Hz. This confirms need for a helper woofer and complicates things.
The purpose for which I picked Ahuja 12-FRX gets defeated.

Regards,

Ravindra.

Here you go with the vented box. I had to modify the box tuning to avoid a deep notch created by the vent velocity at 1645Hz. I will not be surprised if you hear this peak with the recommended winisd values. I had to modify the vent dia and length to get rid of this nasty notch.