sllt/IB project. Need help with port size 4xUL18" - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 04-20-2017, 12:36 AM - Thread Starter
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Cool sllt/IB project. Need help with port size 4xUL18"

Hi.

I had hoped I did not have to ask for help for this, but as I am using a mac I cannot make winisd work. Not even the online option. Could I ask one of you subwoofer gurus for help calculating size of bass port and length of the tube in my project?

I got a tip on another thread that I should port my IB build incase sllt would work better in my room. That way I could seal off the port if I liked the IB better. a two in one deal. I thought that made sense, so I hope I can get help figuring out the port/tube size for this while the wall is still being built.

My "box" volume is 154.5ft3 or 4374L I have 4 Dayton Ultimax 18" in that wall. Tuning around 14-15Hz seems good. I would like 2 ports if possible.

Data for ultimax:

Product Specifications
Nominal Diameter18"Power Handling (RMS)1,000 Watts
Power Handling (max)2,000 WattsImpedance4 ohms
Frequency Response19 to 500 HzSensitivity88.6 dB 2.83V/1m
Voice Coil Diameter3"
Thiele-Small Parameters
Resonant Frequency (Fs)19.50 HzDC Resistance (Re)4.4 ohms
Voice Coil Inductance (Le)2.22 mHMechanical Q (Qms)3.82
Electromagnetic Q (Qes)0.62Total Q (Qts)0.53
Compliance Equivalent Volume (Vas)7.49 ft.³Mechanical Compliance of Suspension (Cms)0.10 mm/N
BL Product (BL)23.8 TmDiaphragm Mass Inc. Airload (Mms)655g
Maximum Linear Excursion (Xmax)22 mmSurface Area of Cone (Sd)1,219 cm²

Hope someone can come to the rescue :-)

Alex
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post #2 of 5 Old 04-21-2017, 05:58 AM
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Here's a model of IB, 15Hz SLLT in heavier green, and 12 Hz SLLT in lighter green. 1000W per driver. Port size is 20" by 20". WinISD calculates 14.4" long for 15 Hz and 31.7" long for 12 Hz. Could be some variability in that depending on boundary surfaces, i.e. if the port mouths are near the floor or wall, the floor/wall can act like an extension to the port. Also note that 1000W pushes the IB a little past what I'd consider max excursion. SLLT could possibly handle a little more power. 28mm is based on Data-Bass's estimate of max usable xmax, where Dayton publishes a figure of 22mm geometric xmax.



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post #3 of 5 Old 04-21-2017, 09:24 AM
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Wall looks great articfly, I think you'll be impressed with the results. The plots are interesting...
Just looking at the FR and impedance plots, the 15Hz tuning would mean more energy and be harder-hitting, but still reap benefits of IB I would think.
Also given the vast majority of recording don't go that low anyway, I'd personally not eat away at efficiency chasing lower frequencies.
Just thinking out loud here...ymmv...carry on...

In any event, excited to hear your impressions.

Actually, I love tube amps..
I play guitars through them.
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post #4 of 5 Old 04-21-2017, 12:28 PM
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To be fair you have to run the IB below xmax as well. It shows past xmax at 18hz or so. Lower the power on the IB to keep it under xmax and then look at the graphs.
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post #5 of 5 Old 04-21-2017, 11:14 PM - Thread Starter
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Thank You rhodeshj!

I will get back to you with results when the cinema is ready. I think I might go for 15Hz so the neighbours across the yard keep the paintings on the wall.

That is one big port! Can i USE 10x30 or will the airflow behave differently?

Last edited by arcticfly; 04-21-2017 at 11:15 PM. Reason: Writing errors
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