OK, over here (http://www.diyaudio.com/forums/showthread.php?s=&threadid=76982) I had a thread started on the buyout plate amp I'm using with this project. I'm very pleased with the sealed box I'm using right now; it added a lot of extension to my main speakers, but I'd like to try a ported design more suited toward movie viewing. However, at the same time I want to keep the low group delay of a sealed enclosure since I listen to a lot of music during the day.
I know that a lot of people have suggested a 3.5 cu ft box tuned to 20 Hz as a very good design for the Assassin driver. However, I have a small room and I know that room gain will make a big difference on what the subwoofer will sound like. If I build the above design, will the room gain add a peaking bottom end? I've seen figures such as boost being up to 9 dB at 16 Hz, and when I used the room gain feature in BassBox, the equates out to a boost around 40 Hz at 6 dB per octave; is this reasonable?
I know that a large effect on room gain will be placement and materials in the room, but from what I've been able to tell so far, I have mainly one null in the very center of the room and basically everywhere else the response is fairly smooth from what I've been able to discern (except for the VERY corners of the room where the bass is boosted significantly).
At the moment, however, the sealed box I'm using is place about 1 foot from the front wall of my room and 2 feet from the sidewall, however if I build a larger box, it'll probably be pushed right back into the corner of the room, so can I expect the 6 dB per octave of boost beginning at 40 Hz? Do you expect it to be more than this? Less?
If need be, I can take a couple of pictures of my room to give everybody an idea of what the room is setup like and how things are arranged to give you an idea of what I'm working with. A short description would be:
It's a typical highschooler room. Carpeted floor, pine carsiding on all walls, a closet and a bed in the room, a computer desk and my audio system. When I do the famous hand clap test to test for a ringing of the room, the room actually responds very well. There aren't really any unfavorable frequencies which ring. The only real differences in sound throughout the room occur in the bass region becuase of the small size of the room.
Dimensions of the room (if I remember correctly, I haven't measured the room in a while) are around... 7 ft cieling, 12-13 ft wide, by 10 ft deep.
I'm pretty capable at playing around with BassBox and hammering out a good alignment for specs I'm looking for, but I'm looking to keep the response fairly flat and smaller is always better if the output doesn't suffer, so I'm looking for help at guestimating a room gain effect to plug in when designing the system.
Thanks for the help.
PS: if I had a mic, I'd measure the response of the subwoofer outside and compare it with the inroom response, but unfortunatly I don't have the hardware to do so, so getting actual measurements isn't a possiblity.
I know that a lot of people have suggested a 3.5 cu ft box tuned to 20 Hz as a very good design for the Assassin driver. However, I have a small room and I know that room gain will make a big difference on what the subwoofer will sound like. If I build the above design, will the room gain add a peaking bottom end? I've seen figures such as boost being up to 9 dB at 16 Hz, and when I used the room gain feature in BassBox, the equates out to a boost around 40 Hz at 6 dB per octave; is this reasonable?
I know that a large effect on room gain will be placement and materials in the room, but from what I've been able to tell so far, I have mainly one null in the very center of the room and basically everywhere else the response is fairly smooth from what I've been able to discern (except for the VERY corners of the room where the bass is boosted significantly).
At the moment, however, the sealed box I'm using is place about 1 foot from the front wall of my room and 2 feet from the sidewall, however if I build a larger box, it'll probably be pushed right back into the corner of the room, so can I expect the 6 dB per octave of boost beginning at 40 Hz? Do you expect it to be more than this? Less?
If need be, I can take a couple of pictures of my room to give everybody an idea of what the room is setup like and how things are arranged to give you an idea of what I'm working with. A short description would be:
It's a typical highschooler room. Carpeted floor, pine carsiding on all walls, a closet and a bed in the room, a computer desk and my audio system. When I do the famous hand clap test to test for a ringing of the room, the room actually responds very well. There aren't really any unfavorable frequencies which ring. The only real differences in sound throughout the room occur in the bass region becuase of the small size of the room.
Dimensions of the room (if I remember correctly, I haven't measured the room in a while) are around... 7 ft cieling, 12-13 ft wide, by 10 ft deep.
I'm pretty capable at playing around with BassBox and hammering out a good alignment for specs I'm looking for, but I'm looking to keep the response fairly flat and smaller is always better if the output doesn't suffer, so I'm looking for help at guestimating a room gain effect to plug in when designing the system.
Thanks for the help.
PS: if I had a mic, I'd measure the response of the subwoofer outside and compare it with the inroom response, but unfortunatly I don't have the hardware to do so, so getting actual measurements isn't a possiblity.
Hi, everyone have his idea on room gain, but Acoustic Elegance, Adire Audio, alot of people and myself agree on around 3 dB per octave in a "standard" room.
160 Hz = 0
80 Hz = +3
40 Hz = +6
20 Hz = +9
10 Hz = +12
To have less group delay problems, you can tune even lower than 20 Hz (like between 16 and 18 Hz), but that will require a larger box to accomodate the port.
160 Hz = 0
80 Hz = +3
40 Hz = +6
20 Hz = +9
10 Hz = +12
To have less group delay problems, you can tune even lower than 20 Hz (like between 16 and 18 Hz), but that will require a larger box to accomodate the port.
Thank you, simon5.
What do they consider the "typical" room? Does everybody think my room is large enough to be a typical room?
I also plan to tune no higher than 20 Hz because 1) I want to have the low extension 2) I want to keep the group delay low from 40 Hz upward.
If everybody thinks that the 3 dB per octave at 80 Hz is suitable, I'll start playing around with figures from there.
Thanks.
What do they consider the "typical" room? Does everybody think my room is large enough to be a typical room?
I also plan to tune no higher than 20 Hz because 1) I want to have the low extension 2) I want to keep the group delay low from 40 Hz upward.
If everybody thinks that the 3 dB per octave at 80 Hz is suitable, I'll start playing around with figures from there.
Thanks.
Typical room is a room without concrete walls I guess hehe!
Adire Audio talks about a 1750 cu.ft room.
Also, if your room is smaller than this, room gain just start higher, let say 160 Hz instead of 80 Hz.
Adire Audio talks about a 1750 cu.ft room.
Also, if your room is smaller than this, room gain just start higher, let say 160 Hz instead of 80 Hz.
Well, my room is a little more than half that size. Rough estimates give me a room of 980 cu ft. I've been playing with BassBox room gain starting at 80 Hz at 3 dB per octave like Simon5 had suggested. Is this going to need to be revised since my room is smaller than the "typical" room?
measurements?
I'm wondering if measurements can be done without a measurement microphone. I have a friend who has a couple of mics for speech and so forth, but can they be used for measurement purposes?
I don't mean that I'll be using them to EQ the system flat. I know that's not possible since that's not what they were built for, but if I did a half space test outside with my subwoofer and then brought it into my room to measure, would the mic be of high enough quality to just find the difference between the two measurements?
I don't know what any of the hardware he has is though. No clue on what brand of mics or preamps he has, but would it matter that much if it was all a comparison test, and not an absolute measurement, let's EQ it flat kind of test?
Then I could maybe even determine placement options due to room modes and such also.
I'm wondering if measurements can be done without a measurement microphone. I have a friend who has a couple of mics for speech and so forth, but can they be used for measurement purposes?
I don't mean that I'll be using them to EQ the system flat. I know that's not possible since that's not what they were built for, but if I did a half space test outside with my subwoofer and then brought it into my room to measure, would the mic be of high enough quality to just find the difference between the two measurements?
I don't know what any of the hardware he has is though. No clue on what brand of mics or preamps he has, but would it matter that much if it was all a comparison test, and not an absolute measurement, let's EQ it flat kind of test?
Then I could maybe even determine placement options due to room modes and such also.
The mic would find the difference between the two measurements for sure. Some mics are better to measure bass on the other hand.
Your room is half the size, I'd start the gain at 160 Hz then.
Your room is half the size, I'd start the gain at 160 Hz then.
Well, I've played around with BassBox some more, and it looks like anything above about 60-80 Hz as a corner point for room gain won't make much difference in output. The only thing moving the f3 point upto 160 Hz did was add about 3 dB of max output across the entire operating band, so as long as everybody suggests 3 dB per octave above about 60 Hz for my room, I won't bother too much with the actual f3 point.
So if it's agreed that 3 dB per octave is appropriate... I'll work with that.
So if it's agreed that 3 dB per octave is appropriate... I'll work with that.
Well, now that summer is here and I'm out of school, and now that I've saved up some money from working, I have the time and money to start building my enclosure (once I convince my parents to run me up to the city to buy some MDF) right now I'm looking at building a 3.8 cu. ft. box tuned to around 17.5 Hz. This will give me an approximate in room response down to 17 Hz. I'm thinking the box will be around 36" x 14" x 18" Does this seem reasonable to you guys? Or, since I have a small room, should I bring the box size down a little bit and push the tuning up to 20 Hz like most people do? 90% of the time, I use my subwoofer for music so I want to keep the tuning low to keep group delay down near the kickdrum frequencies, but the 10% of the time when I watch movies, I really miss the deep response. I can see my sub trying to get output and things start to vibrate a little, but I'm looking for help from a ported sub.
So is the extra size worth the little bit of extended frequency response or should I try to maximize my space and tune just a little higher?
So is the extra size worth the little bit of extended frequency response or should I try to maximize my space and tune just a little higher?
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