I would like to use some 8" Peerless drivers as subwoofers for music/tv/home theater duty in an 18 ft by 12 ft by 8 ft room. I've got 4 of these drivers so there are a number of ways they could be configured. One driver as a sub for each front L/R channel was the initial idea.
Specs for the drivers:
Re 5.35
Fs 31.9
Qms 2.041
Qes 0.311
Qts 0.270
Vas 74.58L
Cms 0.000918
Mms 27.1g
Diameter 175mm
BL 9.66
SPL 90.75dB 2.83V
Sd 0.02405sq.m
Xmax 6.0mm
It is recommended that these drivers be used in vented enclosures. Anyone have any suggestions as to what enclosure volume and port size would be good for my application?
Specs for the drivers:
Re 5.35
Fs 31.9
Qms 2.041
Qes 0.311
Qts 0.270
Vas 74.58L
Cms 0.000918
Mms 27.1g
Diameter 175mm
BL 9.66
SPL 90.75dB 2.83V
Sd 0.02405sq.m
Xmax 6.0mm
It is recommended that these drivers be used in vented enclosures. Anyone have any suggestions as to what enclosure volume and port size would be good for my application?
For for music/tv yes, but skip the HT duty with these. 1.5 cu.ft tuned to 33hz with a 3 inch diameter port 9.5 inches long. It will handle 50 watts input power with a subsonic filter at 26hz. SPL would be around 104db at 40 hz, dropping to 98 db at 30hz, and falls off the face of the earth after that. A high Fs, 6mm xmax, and small Sd does not make for a lot of low end output.
Since the room is more or less rectangular do you think using a vented enclosure per channel and placing the boxes in the corners of the room would raise the low frequency gain enough for home theater use? If not, how about using the extra 2 woofers together in a separate enclosure just for HT use?
Well, four of these won't belt out DD/DTS/THX reference LFE down real low, but assuming the room is enclosed, then the room's first axial mode should be around 31 Hz, so all things considered, the drivers can be tuned to ~22 Hz in an EBS alignment where Vb = Vas, which in theory will couple well enough in the four corners to keep them from bottoming out at the limited power required to stay linear in the octave above Fb. Still, according to HR sims they should hit reference down to 20 Hz with only 20 W each, so if any hi-pass is required it should be minimal and below 20 Hz.
Like other Peerless sub drivers, this one requires a large/long vent, though a MLTL will shorten it a bit, but I recommend a TQWT for such alignments which tend to have the same or slightly less net Vb and better damping, but are long, so typically require some folding. This one only needs to be ~80.4" i.d. long though, so standing it up in the corner with the driver at the floor and vent up near the ceiling should make for a nice room filling bass with minimal room intrusion. Never tried putting a sub driver this high up, but flopping one or more to put the driver up high might help a bit with floor/ceiling modes as it does at ~2/3 room height.
FYI, the LFE is mono below 120 Hz and typically below 150 Hz for music if they still haven't adopted the DD/DTS/THX reference, so all can be driven off a common amp. White paper on multiple sub layout: http://www.harman.com/wp/pdf/multsubs.pdf
Anyway, let me know if either of these is what you want to build.
BTW, for my records, which model driver is this?
GM
Like other Peerless sub drivers, this one requires a large/long vent, though a MLTL will shorten it a bit, but I recommend a TQWT for such alignments which tend to have the same or slightly less net Vb and better damping, but are long, so typically require some folding. This one only needs to be ~80.4" i.d. long though, so standing it up in the corner with the driver at the floor and vent up near the ceiling should make for a nice room filling bass with minimal room intrusion. Never tried putting a sub driver this high up, but flopping one or more to put the driver up high might help a bit with floor/ceiling modes as it does at ~2/3 room height.
FYI, the LFE is mono below 120 Hz and typically below 150 Hz for music if they still haven't adopted the DD/DTS/THX reference, so all can be driven off a common amp. White paper on multiple sub layout: http://www.harman.com/wp/pdf/multsubs.pdf
Anyway, let me know if either of these is what you want to build.
BTW, for my records, which model driver is this?
GM
Hi GM.
The room is an 18'x12' living room with a 10'x11' dining area adjacent to it (think of an L shape), so it is not an enclosed room. There is also a small closet on the wall adjacent to where the tv and front speakers would go that could potentially house a subwoofer. Who needs closet space anyway
The 8" Peerless driver is model NPT-11-047-1. It was the subwoofer driver in the NHT M2.5i speakers. I picked them up cheap earlier this year from the NHT surplus sale (and there are still drivers available I believe): http://home.comcast.net/~jhidley/index.html
So the EBS alignment would be a ~75L box tuned to 22Hz (the spreadsheet from diysubwoofers.org calculates that a 3" diameter vent should be about 16.5" long) and you think 4 of those in the corners of the room should get down to 20Hz at reasonable levels with around 20W each? That sounds very doable!
It's probably worth mentioning that this will be in an apartment, so I can't really listen to music or watch tv/movies at insanely loud levels anyway... I have an inkling that 2 of these boxes in the corners of the room behind the front L/R speakers will be enough, but the TQWT standing up in the corner of the room sounds really interesting. Do you think the drivers would work better in a TQWT?
The room is an 18'x12' living room with a 10'x11' dining area adjacent to it (think of an L shape), so it is not an enclosed room. There is also a small closet on the wall adjacent to where the tv and front speakers would go that could potentially house a subwoofer. Who needs closet space anyway
The 8" Peerless driver is model NPT-11-047-1. It was the subwoofer driver in the NHT M2.5i speakers. I picked them up cheap earlier this year from the NHT surplus sale (and there are still drivers available I believe): http://home.comcast.net/~jhidley/index.html
So the EBS alignment would be a ~75L box tuned to 22Hz (the spreadsheet from diysubwoofers.org calculates that a 3" diameter vent should be about 16.5" long) and you think 4 of those in the corners of the room should get down to 20Hz at reasonable levels with around 20W each? That sounds very doable!
It's probably worth mentioning that this will be in an apartment, so I can't really listen to music or watch tv/movies at insanely loud levels anyway... I have an inkling that 2 of these boxes in the corners of the room behind the front L/R speakers will be enough, but the TQWT standing up in the corner of the room sounds really interesting. Do you think the drivers would work better in a TQWT?
Greets!
OK, the room modes are more complex and the room gain curve will shift to a lower frequency that may allow the drivers to unload below tuning and short of making them tapped horns they can't be reliably tuned below ~0.707*Fs. Also, you only have three potentially high gain corners, further reducing summed output down low, ergo probably still fine above tuning for most music, movies, but some pipe organ symphonies and action movies (particularly animated ones) will probably require some form of sharp cut below tuning if played at reference for those times when the neighbors are either away or enjoying it with you.
Power requirements go up too, theoretically pushing the drivers beyond Xmax, but considering Peerless driver's typically high Xmech, doubling power to 40 W/driver.
My experience with apt. living is that normally a small single sealed sub or mains that are tonally balanced down to even ~40 Hz is too much, but multiple subs to average out room modes is still worth the cost/effort IMO even if all they do is idle along as it will make the mains sound more 'full'/tonally balanced.
Yes, it's been my experience that anytime the driver's specs dictates a large/long vent for a given alignment it will perform better overall in a TQWT.
GM
OK, the room modes are more complex and the room gain curve will shift to a lower frequency that may allow the drivers to unload below tuning and short of making them tapped horns they can't be reliably tuned below ~0.707*Fs. Also, you only have three potentially high gain corners, further reducing summed output down low, ergo probably still fine above tuning for most music, movies, but some pipe organ symphonies and action movies (particularly animated ones) will probably require some form of sharp cut below tuning if played at reference for those times when the neighbors are either away or enjoying it with you.
Power requirements go up too, theoretically pushing the drivers beyond Xmax, but considering Peerless driver's typically high Xmech, doubling power to 40 W/driver.
My experience with apt. living is that normally a small single sealed sub or mains that are tonally balanced down to even ~40 Hz is too much, but multiple subs to average out room modes is still worth the cost/effort IMO even if all they do is idle along as it will make the mains sound more 'full'/tonally balanced.
Yes, it's been my experience that anytime the driver's specs dictates a large/long vent for a given alignment it will perform better overall in a TQWT.
GM
BWRX said:
As with the MLTL sim, don't forget to do a 'combine response' in SPL Tools. Note that in both sims the harmonic resonances aren't nearly as bad as predicted, so typical internal damping quells them enough that combined with the XO they're not a problem.
GM
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Looking at the data you posted is still a little foreign but after downloading Hornresp and reading through the help files I gained at least some understanding of what everything means.
Follow along with me to make sure I'm understanding this correctly. For the MLTL the cross-sectional area is constant for S1-S2 and S2-S3 with a total length of 102.16 cm. But S3-S4 necks down from 730.02 sq.cm to 62.06 sq.cm over 0.01 cm and maintains 62.06 sq.cm for 35 cm. In essence, a straight tube/pipe/rectangle for 102.16 cm with a 35 cm long port at one end.
For the TQWT the cross-sectional area starts at 770 sq.cm and goes down to 718.51 sq.cm over 10.16 cm, then down to 77 sq.cm over 194.10 cm.
In either case, where is the driver supposed to be located along the length of the enclosure? Just on the end? I've seen many MLTL enclosures where the line is folded and the driver is located in the middle of the line. How would one do that for either of these designs?
Follow along with me to make sure I'm understanding this correctly. For the MLTL the cross-sectional area is constant for S1-S2 and S2-S3 with a total length of 102.16 cm. But S3-S4 necks down from 730.02 sq.cm to 62.06 sq.cm over 0.01 cm and maintains 62.06 sq.cm for 35 cm. In essence, a straight tube/pipe/rectangle for 102.16 cm with a 35 cm long port at one end.
For the TQWT the cross-sectional area starts at 770 sq.cm and goes down to 718.51 sq.cm over 10.16 cm, then down to 77 sq.cm over 194.10 cm.
In either case, where is the driver supposed to be located along the length of the enclosure? Just on the end? I've seen many MLTL enclosures where the line is folded and the driver is located in the middle of the line. How would one do that for either of these designs?
Yeah, I much prefer MJK's software for these types of cabs, but now that he no longer offers them I can't recommend them, so HR it is.
Right, TLs are technically constant (zero) taper, ergo MLTL defines a high aspect ratio rectangular or round cab with the driver and vent located somewhere along the line.
Right, (S1-S2) defines the closed end to the center-line of the driver and (S2-S3) the center-line to the 'open' end (i.e. vent tube).
The way HR is programmed, an acoustically insignificant length transition section is required to define a sharp step in the pipe's total length (TL + vent tube).
Right, same scenario as the MLTL except the rectangular cab + vent has been morphed into a single reverse tapered pipe at a 10:1 ratio, though different ratios could be used, but I've had what I consider good success with it, so I don't bother to fix what isn't broke.
WRT driver location, you ideally use what works best for the app. For sub duty, we normally want the max loading (acoustic gain, damping) the alignment has to offer, so this means the driver at the extreme closed end and the vent at the other. This also causes the greatest amplitude harmonic structure, but we can trade some of it for a wider usable BW by 'sliding' the driver down the pipe to find the smoothest, most extended HF response if it's a MLTL or ML-horn, but the TQWT requires its taper ratio be reduced (increase pipe length).
GM
Right, TLs are technically constant (zero) taper, ergo MLTL defines a high aspect ratio rectangular or round cab with the driver and vent located somewhere along the line.
Right, (S1-S2) defines the closed end to the center-line of the driver and (S2-S3) the center-line to the 'open' end (i.e. vent tube).
The way HR is programmed, an acoustically insignificant length transition section is required to define a sharp step in the pipe's total length (TL + vent tube).
Right, same scenario as the MLTL except the rectangular cab + vent has been morphed into a single reverse tapered pipe at a 10:1 ratio, though different ratios could be used, but I've had what I consider good success with it, so I don't bother to fix what isn't broke.
WRT driver location, you ideally use what works best for the app. For sub duty, we normally want the max loading (acoustic gain, damping) the alignment has to offer, so this means the driver at the extreme closed end and the vent at the other. This also causes the greatest amplitude harmonic structure, but we can trade some of it for a wider usable BW by 'sliding' the driver down the pipe to find the smoothest, most extended HF response if it's a MLTL or ML-horn, but the TQWT requires its taper ratio be reduced (increase pipe length).
GM
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