Force f3 lower in sealed box

BradH

Member
2019-07-13 10:35 pm
I'm sure this has been discussed numerous times, but I did a search and only have so much time to sift through threads. Sorry about that.

What happens when you use digital EQ to push f3 lower in a sealed box? I have 4 of these in a ~1.83 ft.³ or 52 liter enclosure. PE site says one in 1.53 ft.³ / 43L has f3 49hz. I would like to get close to 40hz. If not practical it's fine, I can use subs. I'm in a concrete apartment and listen quietly without much bass anyway. But it would be nice to get these down near 40hz.

Also fs is 52hz, but I think I remember reading that going below fs in low freq. isn't a big issue.

Also if you wonder about the arrangement of 4 drivers in a smallish enclosure, I'm making sure some things are feasible and then will make a build thread. It will make sense...maybe
 

ernperkins

Member
2009-11-24 8:39 pm
Putting 4 of those in 1.83 ft3 will change the response: you'll have a 3.5 dB peak (Qtc = 1.4) at about 95 Hz and a f3 of about 59 Hz. I modeled three configurations using WinISD: a single driver (blue trace), 4 drivers (red trace) and 4 drivers using a Linkwitz Transform to achieve a 40 Hz F3 (green trace). All configurations used a box size of 1.83 ft3 and were fed 8 watts. I chose 8 watts since it drives the 4 driver boxes to 100 dB. I included graphs for the transfer function, SPL, cone excursion and required amplifier power from WinISD.
 

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BradH

Member
2019-07-13 10:35 pm
Oh wow, thank you both! Especially for those graphs. Looks like the Linkwitz transform is exactly what I want. I'll read the paper on it and also re-familiarize myself with winISD. It's been about 10 years. I'm embarrassingly rusty.
 
Last edited:

charlie2

Member
2012-10-27 8:45 am
Uk
Hey Charlie,

I have attached a sim of your driver, I am guessing that the H and J versions have different impedance?
Hope this helps?
Cheers
A.

I have looked at your pdf response thank you very much for taking the time to look at it and model it

Does it mean that I have to pump 600 watts to get a decent f3 /30hz @ 100db

Power is not a problem several qsc audio 1450 amps at disposal with bridging

Thing is I was wanting to go a lot lot lower amplification power wise and space maybe move onto 1st watt nelson pass or valve amplification

Very small room neighbours either side

If u fart they tell you
 
Hiya Charlie,

Happy to help.
The simulated 105 dB at 35Hz continuous (with 111dB peaks assuming 6dB of headroom and the 2,400 watts required power!) is before room gain ie in a corner you will gain real world 6dB to 8dB over and above the sim SPL's... Thats loud!
You will find that in the real world your amps will be running at low to medium power most of the time ie 5 to 10 watts with around 50 to 100-watt peaks and that will be loud music.

You will reduce the SPL's by 3 dB with each halving of input power so:
600 watts = 105dB
300 watts = 102dB
150 watts = 99dB
75 watts = 96dB
37.5 watts = 93dB.
I think you will enjoy this article which details the theory and practical results from the extented low frequency "ELF" subwoofer principal of small sealed box with DSP / Eq and high power amps.
Sub-Woofer Controller
by Rod Elliot... He is an internationally respected audio engineer with over 40 years successful trading in the industry.
 

charlie2

Member
2012-10-27 8:45 am
Uk
Hiya Charlie,

Happy to help.
The simulated 105 dB at 35Hz continuous (with 111dB peaks assuming 6dB of headroom and the 2,400 watts required power!) is before room gain ie in a corner you will gain real world 6dB to 8dB over and above the sim SPL's... Thats loud!
You will find that in the real world your amps will be running at low to medium power most of the time ie 5 to 10 watts with around 50 to 100-watt peaks and that will be loud music.

You will reduce the SPL's by 3 dB with each halving of input power so:
600 watts = 105dB
300 watts = 102dB
150 watts = 99dB
75 watts = 96dB
37.5 watts = 93dB.
I think you will enjoy this article which details the theory and practical results from the extented low frequency "ELF" subwoofer principal of small sealed box with DSP / Eq and high power amps.
Sub-Woofer Controller
by Rod Elliot... He is an internationally respected audio engineer with over 40 years successful trading in the industry.

Thanks so far

I am well versed in the inverse square law

But if I use this driver it is in a multi entry horn meh

I have to many compression drivers
Mid drivers
And mid bass drivers

Need to make a short list of what is practice for my new small room....




Bear in mind at present I have twin jbl 4638 bass cabs with loads of horns /waveguides altec 511b jbl2380 jbl 2440

2445/2426/celestion 10f1020 celestion 1735

Pair of spendor s9 with center
Monitor audio full rs kit
Arcam alpha Fmj am
5 pa amps
Pair of eminence alpha 15a

Can not possibly use it again