The room I will be using the setup in is a living-cum-dining room. The HT will be set up in the living room area, which I would say is about 20x15 feet. There is no carpet.
I have a Denon HT receiver and Vifa MTM fronts. Centre and surrounds will be built later.
I am not expecting thunder but I just want to make the best possible use of the woofers. And I don't mind having a 120L box around.
Vivek
I have a Denon HT receiver and Vifa MTM fronts. Centre and surrounds will be built later.
I am not expecting thunder but I just want to make the best possible use of the woofers. And I don't mind having a 120L box around.
Vivek
Re: Re: Car subs for home theatre
GM, I am that "friend" I think Vivek refered to. I was travelling a bit and did not have too much time to reply earlier. I am a big TL fan, ever since the days of Bud (Irving) Fried. but the reason I suggested Aperiodic is that
a) Indian rooms are quite small compared to US homes.
b) Indian homes are made of brick and mortar and hence do offer some bass reinforcement so if the F3 was about 50Hz as long as the roll off is slow the room gain should provide enough "oopph" to about 30-35Hz. I will surprsied if Vivek would get any thing below that.
c) Vivek is recently married. Very soon WAF will kick in (I know - I had to "move down" from using 2 JBL 2245 based subs to 4 Audio Concpets based 12" subs) and even a 120 liter box might become too large.
LT would require huge power. I am not sure if this driver is designed to handle those ammounts of power. The alternate is to keep the driver within it's thermal and physical (Xmax) operating limits and just lower the expectation of the maximum SPL one can achieve.
Vivek,
Given the drivers you got I think you really have to choices.
a) Dont use any EQ (Linkwitz transform is a sort of an EQ) and live with the highish F3. Then use room placement to good effect.
b) Use LT which will drop the F3 but limit the power handling of the driver (and hecne the SPLs).
What say guys?
GM said:
GM, I am that "friend" I think Vivek refered to. I was travelling a bit and did not have too much time to reply earlier. I am a big TL fan, ever since the days of Bud (Irving) Fried. but the reason I suggested Aperiodic is that
a) Indian rooms are quite small compared to US homes.
b) Indian homes are made of brick and mortar and hence do offer some bass reinforcement so if the F3 was about 50Hz as long as the roll off is slow the room gain should provide enough "oopph" to about 30-35Hz. I will surprsied if Vivek would get any thing below that.
c) Vivek is recently married. Very soon WAF will kick in (I know - I had to "move down" from using 2 JBL 2245 based subs to 4 Audio Concpets based 12" subs) and even a 120 liter box might become too large.
richie00boy said:
LT would require huge power. I am not sure if this driver is designed to handle those ammounts of power. The alternate is to keep the driver within it's thermal and physical (Xmax) operating limits and just lower the expectation of the maximum SPL one can achieve.
Vivek,
Given the drivers you got I think you really have to choices.
a) Dont use any EQ (Linkwitz transform is a sort of an EQ) and live with the highish F3. Then use room placement to good effect.
b) Use LT which will drop the F3 but limit the power handling of the driver (and hecne the SPLs).
What say guys?
There will be no difference in your a) and b) regards max SPL achievable, for that is determined by excursion and radiating area, which do not change whatever the size of the sealed box. Provided of course that the box is not so small that the thermal limit is reached.
You are correct that a Linkwitz Transform could soon get messy with regards to power requirements and/or the driver thermal limit may be reached too quickly. But it is possible to do a 'mild' LT.
I would just think about what size is acceptable, see how that pans out response wise then go from there, adding an LT if you desire a little bit more.
You are correct that a Linkwitz Transform could soon get messy with regards to power requirements and/or the driver thermal limit may be reached too quickly. But it is possible to do a 'mild' LT.
I would just think about what size is acceptable, see how that pans out response wise then go from there, adding an LT if you desire a little bit more.
Like I said before, something like a 100 or 120 litre box is fine with me (taking into consideration WAF 
).
If using an LT requires a lot of power, then we have a bit of a problem because I am finding it difficult to get amps. In India, getting plate amps is could be a slight problem.
Richie, maybe I will try the 160W mosfet amp you have posted on your site.
). If using an LT requires a lot of power, then we have a bit of a problem because I am finding it difficult to get amps. In India, getting plate amps is could be a slight problem.
Richie, maybe I will try the 160W mosfet amp you have posted on your site.
The subs have good Xmax so I think there is potential for getting down quite low.
I'll try and do a quick simulation of power handling and SPL for one driver in a 50 litre box (or did you want both drivers in one box?) tonight for you and put the results up here (to supplement Bjorno's simulations).
I'll try and do a quick simulation of power handling and SPL for one driver in a 50 litre box (or did you want both drivers in one box?) tonight for you and put the results up here (to supplement Bjorno's simulations).
Vivek said:I live in an apartment and the place is crowded with too many speakers. And my wife is already complaining.
actually having 2 boxes might
a) offer better sound becuase you can place them with greater flexibility
b) be easier to build I find weilding larger sheets of wood more difficult
c) require less bracing
One way of improving WAF is getting the W involved.
If your woodworking skills are minimal, and you need to keep the W happy, you might take the W and a tape measure ang go shopping for a trunk or two that match the decor of your home and that the W approves of. Gut them, and fill them with a solid, doesn't have to be pretty, box for your drivers.
Viola, you have your subs with substantial WAF. In fact your W may brag to her friends about how clever you are, and how much she likes the new furniture.
See this thread.
Paul
If your woodworking skills are minimal, and you need to keep the W happy, you might take the W and a tape measure ang go shopping for a trunk or two that match the decor of your home and that the W approves of. Gut them, and fill them with a solid, doesn't have to be pretty, box for your drivers.
Viola, you have your subs with substantial WAF. In fact your W may brag to her friends about how clever you are, and how much she likes the new furniture.
See this thread.
Paul
Attachments
Vivek: Post#23:
A new joker:
Vivek: Post#26:
Vivek: Post#28:
Vivek: Post#35:
Vivek,
What LT parameters? What box size? Will two boxes imply 2 amplifiers?
Are you aware if using 20 Hz as a design goal and by using my simulations will restrict the available output pass-band power/driver to either 160/23 = 7W or 160/9.44=17 W?
This implies a maximum SPL/driver of either 92 + 10 log (7) = 100 W SPLmax or 92+10 log (17)= 104 W SPLmax and independent if you use one or two drivers with your suggested amplifier provided this amplifier is optimal for 4 Ohm load and doesn’t lower available output power for a 8 Ohm load?
Or is this 160W amplifier capable to drive a 2-Ohm load?
A driver advertised having a free air peak power handling of 1200 W and by use of the recommended amplifier = 300W RMS, using LT, would increase the maximum SPL with an additional 2.73 dB i.e. 102.7 and 106.7.
Check if those levels are within the driver maximum excursion capability (x-max), i.e.:
dB SPL= 20 x log(excursion in (mm)) + 40 x log(effective cone dia. in (mm)) +40 x log(lowest freq) – 86, this for 2*PI Steer radians;
Excursion = 10^(dB SPL/20- 2 x log (effective cone dia. in (mm)) -2 x log (lowest freq) + 4.3)
With 10 dB headroom margin lowers max SPL to 92.7 or 96.7.
Are these possible levels within your design goals?
In my design LT suggestions I didn’t waste unnecessary power/ excursion capability or the possible achievable SPL with a heavily applied LT, or did I?
A very common goal for HT use is a sub-woofer reaching f3=20 Hz and the consequences can be found in my simulations.
50 L is the box size for one driver when volume is optimised considering fc and f3.
Pick any other volume and LT use will be sub-optimised.
I think the optimum approach were taken for this case and was covered with my LT suggestions where the entering point was to put these woofers in a closed box but not exceeding a size about 2x 50L unstuffed (f3 to about 44 Hz, Qtc = 0.707) as this volume (100L) would optimise FR flatness, the possible acoustic output power at f3 without any FR compensation for HT use.
Of course it’s not necessary to reach 20 Hz for a speaker if the room gain/ corner placement is also brought into the equation, another joker?
More conservative LT parameter settings can relax the power requirement of the sub-amplifier.
Look at the submitted picture where the sub amplifier power requirement is traded with f3 for a Bessel system response or if a critical damped system is preferred (?), the parameters affecting the LT- components must be modified although the DC-gain (loss) will still be constant.
Before you chose (an) amplifier(s) (2x300W?), decide if the drivers are to be paralleled or in series or separate and maybe pick one of the new simulations and calculate with power headroom of at least 10 dB. If you don’t you’re HT subs will be sub optimized.
10 question marks… Decisions, decisions, decisions… decisions
b
1(1)
A new joker:
Vivek: Post#26:
Vivek: Post#28:
Vivek: Post#35:
Vivek,
What LT parameters? What box size? Will two boxes imply 2 amplifiers?
Are you aware if using 20 Hz as a design goal and by using my simulations will restrict the available output pass-band power/driver to either 160/23 = 7W or 160/9.44=17 W?
This implies a maximum SPL/driver of either 92 + 10 log (7) = 100 W SPLmax or 92+10 log (17)= 104 W SPLmax and independent if you use one or two drivers with your suggested amplifier provided this amplifier is optimal for 4 Ohm load and doesn’t lower available output power for a 8 Ohm load?
Or is this 160W amplifier capable to drive a 2-Ohm load?
A driver advertised having a free air peak power handling of 1200 W and by use of the recommended amplifier = 300W RMS, using LT, would increase the maximum SPL with an additional 2.73 dB i.e. 102.7 and 106.7.
Check if those levels are within the driver maximum excursion capability (x-max), i.e.:
dB SPL= 20 x log(excursion in (mm)) + 40 x log(effective cone dia. in (mm)) +40 x log(lowest freq) – 86, this for 2*PI Steer radians;
Excursion = 10^(dB SPL/20- 2 x log (effective cone dia. in (mm)) -2 x log (lowest freq) + 4.3)
With 10 dB headroom margin lowers max SPL to 92.7 or 96.7.
Are these possible levels within your design goals?
In my design LT suggestions I didn’t waste unnecessary power/ excursion capability or the possible achievable SPL with a heavily applied LT, or did I?
A very common goal for HT use is a sub-woofer reaching f3=20 Hz and the consequences can be found in my simulations.
50 L is the box size for one driver when volume is optimised considering fc and f3.
Pick any other volume and LT use will be sub-optimised.
I think the optimum approach were taken for this case and was covered with my LT suggestions where the entering point was to put these woofers in a closed box but not exceeding a size about 2x 50L unstuffed (f3 to about 44 Hz, Qtc = 0.707) as this volume (100L) would optimise FR flatness, the possible acoustic output power at f3 without any FR compensation for HT use.
Of course it’s not necessary to reach 20 Hz for a speaker if the room gain/ corner placement is also brought into the equation, another joker?
More conservative LT parameter settings can relax the power requirement of the sub-amplifier.
Look at the submitted picture where the sub amplifier power requirement is traded with f3 for a Bessel system response or if a critical damped system is preferred (?), the parameters affecting the LT- components must be modified although the DC-gain (loss) will still be constant.
Before you chose (an) amplifier(s) (2x300W?), decide if the drivers are to be paralleled or in series or separate and maybe pick one of the new simulations and calculate with power headroom of at least 10 dB. If you don’t you’re HT subs will be sub optimized.
10 question marks… Decisions, decisions, decisions… decisions
b
1(1)
Attachments
Bjorno, I really would not have used a 160W amp for a 300W sub.
Ok, more doubts:
1) Is it wiser to use the subs in parallel or in series? I really don't know how many subwoofer amps there are which can handle 2 ohms.
2) I think I will make two boxes, LT both of them with two separate amps. Then split the subwoofer output on the HT receiver into two and use two amps and two separate subs. How will that work out?
3) I don't mind using conservative LT settings if it is going to make a big difference in power requirement. This is because I am really not sure what kind of amp I will be able to build. In India, I don't know if I will be able to get parts (in small quantities) for amplifier designs which are published on the net.
Ok, more doubts:
1) Is it wiser to use the subs in parallel or in series? I really don't know how many subwoofer amps there are which can handle 2 ohms.
2) I think I will make two boxes, LT both of them with two separate amps. Then split the subwoofer output on the HT receiver into two and use two amps and two separate subs. How will that work out?
3) I don't mind using conservative LT settings if it is going to make a big difference in power requirement. This is because I am really not sure what kind of amp I will be able to build. In India, I don't know if I will be able to get parts (in small quantities) for amplifier designs which are published on the net.
Sorry for my false accusation, I had a small hunch I could be wrong…
Parallel is best and series can be a problem if the two subs are sensing different acoustic loads due to different placement of the speakers i.e. sensing different space angles.
I believe many Car amps do handle 2 Ohms or lower and there should be quite a few, typical class D type, but maybe by using a Bash amp concept type would save energy too.
This is the right decision and will work fine and even better if the subs separately are driven with L an R signals not summed. Arguments for can be found in these papers:
http://www.icad.org/websiteV2.0/Conferences/ICAD2002/proceedings/71_Martens.pdf
and
http://www.std.com/~griesngr/asa05.pdf
Ok, Why not build an amplifier and test the moderate P = 4 times power loss (f3= 31 Hz) as a good start.
b
I do not disagree with
but, it depends on the room. This room is all earth tones and wood of various types, sort of an African motif.
I am more interested in the sound, and if it makes my wife happy to the point that she brags about them, as opposed to just accepting them, they can be purple with yellow polka dots for all I care.
I am not suggesting those trunks are for anyone else, but, if you do not have great woodworking skills, and you want your wife on board with your obsession, there are lots of different style trunks, ottomons, and miscellaneous cabinets that are suitable for hiding a subwoofer in.
Paul
but, it depends on the room. This room is all earth tones and wood of various types, sort of an African motif.
I am more interested in the sound, and if it makes my wife happy to the point that she brags about them, as opposed to just accepting them, they can be purple with yellow polka dots for all I care.
I am not suggesting those trunks are for anyone else, but, if you do not have great woodworking skills, and you want your wife on board with your obsession, there are lots of different style trunks, ottomons, and miscellaneous cabinets that are suitable for hiding a subwoofer in.
Paul
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