Hi all,
I have a couple of Infinity Reference 1230W 12 inch car subs which I plan to use for home theatre. I was thinking of using both of them in a sealed box (placed magnet to magnet). My friend suggests there might be lumpiness in the bass since these are car drivers. He thinks an aperiodic box may be the solution.
Could anyone help me out here?
Thanks,
Vivek
I have a couple of Infinity Reference 1230W 12 inch car subs which I plan to use for home theatre. I was thinking of using both of them in a sealed box (placed magnet to magnet). My friend suggests there might be lumpiness in the bass since these are car drivers. He thinks an aperiodic box may be the solution.
Could anyone help me out here?
Thanks,
Vivek
Here are the TS parameters:
voice coil dc resistance: 3.40 ohm
voice coil inductance @ 1 khz: levc (mh) . . . . . . . 2.54
driver radiating area: sd (in2) . . . . . . . . 82.48
motor force factor: bl (tm) . . . . . . . . 14.63
compliance volume: vas (liters) . . . . . 78.50
suspension compliance: cms (µm/n) . . . . 195.40
moving mass, air load: mms (grams). . . . 174.21
moving mass, diaphragm: mmd (grams) . . . 167.15
free-air resonance: fs (hz) . . . . . . . . 27.27
mechanical q: qms . . . . . . . . . . . 6.14
electrical q: qes . . . . . . . . . . . . 0.47
total q: qts . . . . . . . . . . . . 0.44
magnetic-gap height: hag (mm) . . . . . . . . 8.00
voice-coil height: hvc (mm) . . . . . . . 32.50
maximum excursion: xmax (mm) . . . . . . 12.25
voice coil dc resistance: 3.40 ohm
voice coil inductance @ 1 khz: levc (mh) . . . . . . . 2.54
driver radiating area: sd (in2) . . . . . . . . 82.48
motor force factor: bl (tm) . . . . . . . . 14.63
compliance volume: vas (liters) . . . . . 78.50
suspension compliance: cms (µm/n) . . . . 195.40
moving mass, air load: mms (grams). . . . 174.21
moving mass, diaphragm: mmd (grams) . . . 167.15
free-air resonance: fs (hz) . . . . . . . . 27.27
mechanical q: qms . . . . . . . . . . . 6.14
electrical q: qes . . . . . . . . . . . . 0.47
total q: qts . . . . . . . . . . . . 0.44
magnetic-gap height: hag (mm) . . . . . . . . 8.00
voice-coil height: hvc (mm) . . . . . . . 32.50
maximum excursion: xmax (mm) . . . . . . 12.25
Greets!
Well, there will be a mid-bass rise due to the high Le if you don't parallel them, but for a critically damped alignment (Qtc = 0.5) there shouldn't be any 'lumpiness' in its response other than what the room does to it:
Vb = ~12.89 ft^3 (365 L), F3 = ~51 Hz, Fb = 33 Hz.
Not exactly HT LFE performance and while raising Qtc will reduce Vb, it will raise Fb, so you may want to re-think your choices unless your room is small and constructed well enough to get some additional acoustic gain BW down low.
For instance, a Fp = Fs end loaded Alpha TL will have a similar Qt and much better damped to below 10 Hz in a smaller, though still large cab:
L = ~122"
CSA = ~104.1"^2
If it must be any smaller, then your friend is correct that it will require a ~aperiodic alignment, which means a high F3, Fb.
GM
Well, there will be a mid-bass rise due to the high Le if you don't parallel them, but for a critically damped alignment (Qtc = 0.5) there shouldn't be any 'lumpiness' in its response other than what the room does to it:
Vb = ~12.89 ft^3 (365 L), F3 = ~51 Hz, Fb = 33 Hz.
Not exactly HT LFE performance and while raising Qtc will reduce Vb, it will raise Fb, so you may want to re-think your choices unless your room is small and constructed well enough to get some additional acoustic gain BW down low.
For instance, a Fp = Fs end loaded Alpha TL will have a similar Qt and much better damped to below 10 Hz in a smaller, though still large cab:
L = ~122"
CSA = ~104.1"^2
If it must be any smaller, then your friend is correct that it will require a ~aperiodic alignment, which means a high F3, Fb.
GM
Do you mean to say that I need to try a ported or some other type of box?
The room is not very big and there are a couple of corners which seem to provide some gain with the Vifa MTM speakers I am using now.
The portion below I just did not understand. sorry.
For instance, a Fp = Fs end loaded Alpha TL will have a similar Qt and much better damped to below 10 Hz in a smaller, though still large cab:
Vivek
The room is not very big and there are a couple of corners which seem to provide some gain with the Vifa MTM speakers I am using now.
The portion below I just did not understand. sorry.
For instance, a Fp = Fs end loaded Alpha TL will have a similar Qt and much better damped to below 10 Hz in a smaller, though still large cab:
Vivek
Greets!
Some movies have content to near Dc and significant output to ~10 Hz, so you want the sub's and room's combined response to be ~flat to as low a frequency as the available budget and space for the sub allows and I seriously doubt your room has enough gain for a ~33 Hz or higher Fb.
I don't recommend a vented alignment since the vent would be so large, long, but this means that a reverse tapered TL (TQWT) will work well and would be ~the same size as the Alpha TL, but with more gain down to ~15 Hz. Transient response would be slightly worse, but still far better than vented and why they are popular.
I'm referring to a simple straight pipe TL (which of course can be folded) tuned to at least Fs made popular by Rick Schultz (AKA 'Exolinear'), which will be smaller (~7.35 ft^3/208 L) with better overall performance than the sealed sub.
GM
Some movies have content to near Dc and significant output to ~10 Hz, so you want the sub's and room's combined response to be ~flat to as low a frequency as the available budget and space for the sub allows and I seriously doubt your room has enough gain for a ~33 Hz or higher Fb.
I don't recommend a vented alignment since the vent would be so large, long, but this means that a reverse tapered TL (TQWT) will work well and would be ~the same size as the Alpha TL, but with more gain down to ~15 Hz. Transient response would be slightly worse, but still far better than vented and why they are popular.
I'm referring to a simple straight pipe TL (which of course can be folded) tuned to at least Fs made popular by Rick Schultz (AKA 'Exolinear'), which will be smaller (~7.35 ft^3/208 L) with better overall performance than the sealed sub.
GM
richie00boy:
Yeah I agree. Check out the project for making one at ESP in the projects pages.
I'm currently building a sealed box with a 10" car sub which (with an LT and sufficient amplification) should be pretty flat with an F3 of around 27Hz, and a nice sealed box roll-off. Box only approx 36 litres (1.3 cubic feet).
Yeah I agree. Check out the project for making one at ESP in the projects pages.
I'm currently building a sealed box with a 10" car sub which (with an LT and sufficient amplification) should be pretty flat with an F3 of around 27Hz, and a nice sealed box roll-off. Box only approx 36 litres (1.3 cubic feet).
A good idea but…
Agree.
I prefer a low Q box for a sub, and would pick a frequency between 22 to 31Hz to make it easy for the amp and if using LT economize the extra use of excursion.
I would build a stuffed 85 L to 100 L un-stuffed, sectioned, heavily braced enclosure for 2 drivers and use LT Q = 0,5-0,577.
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Vivek said:
Greets!
Folded in half it's a simple box with an internal divider that also acts as a brace, so woodworking skills are pretty much limited to whether or not you should be allowed the use of sharp tools.
It's an option if you don't mind 'wasting' a driver and half the amp's power to make it smaller.
GM
richie00boy said:
OK, I'll 'bite', what do you know about TL response that decades of speaker designers and satisfied users don't?
How much more power?
Since I've known very few LT users that preferred little sealed boxes EQ'd to the max over more acoustically efficient lower power subs in a HT app, this seems rather presumptuous of you, especially considering how little we know of what sort of performance Vivek is expecting (hoping for?) or room, etc., it will be used in.
Now if it turns out to be a nearfield computer HT or similar, then the LT is fine (it's what I'm currently using), but for a typical HT, LT subs typically need a much lower Fs, etc. than the Infinity's for decent performance with action movies.
GM
richie00boy said:
FYI, while aperiodic is often used to damp a high Q driver it was originally used (and still is) to lower the Q of too small a box.
No, the real question IMO is what is his primary performance goal? Small size no matter what the cost in overall performance or maximizing performance at the expense of considerable bulk, or some compromise between the two.
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