Need Help with The Smallest 3 way Speaker Plan for LM3886 Triamping

[AndrewT]

Putting a Q=0.853 driver into a sealed box will give a big "hump" in the LF frequency response. The high Q figure of 1 confirms this.
In a small room, or by placing the box near a boundary, you will get a very unnatural sound to male voice. Known as Bass Boom or "one note bass".

A Linkwitz transform could be used to sort this by reducing the effective Q to somewhere in the range 0.5 to 0.7

This high Q driver could be used in an open baffle, or in an infinite baffle. This would save all the effort in trying to design and build a sealed box.

 

[csom]

Putting a Q=0.853 driver into a sealed box will give a big "hump" in the LF frequency response. The high Q figure of 1 confirms this.
In a small room, or by placing the box near a boundary, you will get a very unnatural sound to male voice. Known as Bass Boom or "one note bass".

A Linkwitz transform could be used to sort this by reducing the effective Q to somewhere in the range 0.5 to 0.7

This high Q driver could be used in an open baffle, or in an infinite baffle. This would save all the effort in trying to design and build a sealed box.

Oh thank you so much Sir for your prompt and very informative reply.
I've been longing for long to build one using an open-baffle design.

Here I have some questions.

1. Is the size of the driver Okay even for a mini-open Baffle design?

2. What will be approximate baffle size and thickness for this specific driver?

 

[Dissi]

Mms measurements between -68 g and +12 g and two impedance peaks in closed box, that reminds me very much of another thread:

http://www.diyaudio.com/forums/multi-way/238046-speaker-enclosers-s-2.html#post3543951

Maybe you find some useful information there.

 

[csom]

Mms measurements between -68 g and +12 g and two impedance peaks in closed box, that reminds me very much of another thread:

http://www.diyaudio.com/forums/multi-way/238046-speaker-enclosers-s-2.html#post3543951

Maybe you find some useful information there.

Thank you for posting the link. I've just given a quick look at that and my situation is identical to the OP of that thread. I will give a second look.

Kindly have a look at my earlier posted parameters and I would be grateful if you could kindly suggest a specific and optimized design for me.

I have no other software except LIMP.

 

[Dissi]

I assume the woofer to have a Sd of 110 cm^2 and a Qts around 0.9. Open baffle would work very well, but the maximum SPL of the speaker will be quite limited. Second option is a closed box of any convenient size and some equalization, exactly what AndrewT has been saying.

 

[csom]

I assume the woofer to have a Sd of 110 cm^2 and a Qts around 0.9. Open baffle would work very well, but the maximum SPL of the speaker will be quite limited. Second option is a closed box of any convenient size and some equalization, exactly what AndrewT has been saying.

Thank you for your quick response.

I've been testing various drivers ( what's available here in my area, mainly un-branded, local ones) with OB with blind guess since some days. I like the sound. But I am yet to learn the grammar of OB. 🙂
I use active amplifier and equalizer. So I guess equalizing those won't pose a problem.

Could you kindly post some links to diy friendly OB reading material that is easier to comprehend and any free software to design OB?

I was reading your very useful link that you posted earlier and found an easier way to calibrate limp.
So I'm re-doing/modding the limp-jig now and I will post the result of the new test if they differ from the earlier one.

Also I am awaiting the response from Sir Andrew.

Thank you.
...................................................................................
Update:
I also tried my best to measure effective cone size which is 12.2 cm.
With new procedure of calibration vas is reduced now!

Thiele-Small parameters:
Tested with pink noise:
Fs = 74.55 Hz
Re = 8.00 ohms[dc]
Le = 1238.74 uH
L2 = 2017.01 uH
R2 = 3.83 ohms
Qt = 0.83
Qes = 0.96
Qms = 6.04
Mms = 11.08 grams
Rms = 0.858869 kg/s
Cms = 0.000411 m/N
Vas = 7.89 liters
Sd= 116.90 cm^2
Bl = 6.579041 Tm
ETA = 0.33 %
Lp(2.83V/1m) = 87.26 dB
Added Mass Method:
Added mass = 10.00 grams
Diameter= 12.20 cm


******************************************
Thiele-Small parameters:
Tested with Stepped Sine wave:
Fs = 72.51 Hz
Re = 8.00 ohms[dc]
Le = 1272.69 uH
L2 = 2303.91 uH
R2 = 3.55 ohms
Qt = 0.90
Qes = 1.06
Qms = 6.01
Mms = 10.81 grams
Rms = 0.819442 kg/s
Cms = 0.000446 m/N
Vas = 8.56 liters
Sd= 116.90 cm^2
Bl = 6.101374 Tm
ETA = 0.30 %
Lp(2.83V/1m) = 86.82 dB
Added Mass Method:
Added mass = 10.00 grams
Diameter= 12.20 cm

 

[csom]

Thank you so much
Greebster,
kbzx35,
cT equals piD,
Absconditus,
gootee,
AndrewT and
Dissi
for the kind help of yours.

I am feeling confident now with the ABC of the speaker enclosure building.

I made a sealed enclosure two "specs-not-available drivers" for the centre channel after obtaining the parameters with LIMP and it's working nicely.

I checked with the old trusted method mentioned/taught by cT equals piD and then compared the result with what I got with the help of software and web based tools. And both were identical and so I went forward with confidence and the result is satisfactory, I can say.

I also tuned my sub enclosures and now they are going deeper. 🙂

Thanks a ton really, to all of you!

Here are some snaps. 🙂

 

[gootee]

Good work (again), Som!

You seem like an intelligent, fast learner, who is also well-mannered and hard-working. And it has always been a pleasure to work with you, and to watch (and smile) as your projects develop to successful completions.

Warm regards,

Tom

 

[csom]

Good work (again), Som!

You seem like an intelligent, fast learner, who is also well-mannered and hard-working. And it has always been a pleasure to work with you, and to watch (and smile) as your projects develop to successful completions.

Warm regards,

Tom

I thank you Tom for your kind words.

The awesome association and constant handholding of respected, kind and very knowledgeable people like you all are the real privilege for a half educated man with no formal technical background like myself.

So the real credit goes to you all for your patience, suggestion, teaching and guidance.

I am just following all of your footsteps and getting amazed as I am learning new things day by day.

🙂

 

[csom]

Just finished a ported box tuned at 70 Hz.
Polishing, retouching are yet to be done.
It sounds very good.
Tested with TrueRTA and other freebies.
With the help of PC, it's just a child's play now. 😀
I used Box tune calculator, an android applet, to build the enclosure.

Next plan is to build a T-line with cheap local full range speakers. 🙂

Thank you so much all again. 🙂