first DIY, subwoofer. need advise with components.

[doors666]

Honestly, nor do I, but most people listen at an average of 85-90dB at listening position, 85 dB being loud and 90dB being very loud. 96dB is deafening, and after adding 12dB to it you get 108dB, pretty much standard fare for most subs in this category.

2x2x2 is a pretty big box. Not sure you want a lump of lard in your living room, but go for it if you must.

Polyfill is not mandatory, and it does not take volume out of a box when used, it adds volume. Your calculations seem fine, but I'm not convinced the sub driver and amp together will be .75 cuft, and neither will the bracing. With a 1" box minimal bracing may be used. Panel resonances aren't critical when you're cutting the sub out below 100Hz. Some corner reinforcement should be fine for strength.

Wow.. most of the sub drivers I am considering have efficiency of 86-90 db/w/m. So assuming 87 db, I will achieve 96 db of deafening sound at about 8w. 3db for each doubling of power.

those were very rough calculations, will compute it properly when I am going to actually build it.

george has a small sub as he's using a PR. I dont wanna go for a PR, one more things for the kids to poke at.

Here's my design philosophy:

1. at full wattage of the amp, make sure that the air speed and cone velocity are within limits. I wont be using it at this wattage, but there will be times where due to peaks etc, it will hit close to that temporarily and the driver should not blow cause its hitting xmax.

2. for spl purposes, use 50% power. tinker with the options to get the max size so that I get the largest acceptable port size, this will also give me the least possible tuning frequency. make sure speed and cone excursion are still within limits at max power.

I want to have as less a -3db point as possible. If that gives me a big sub size, so be it. The 2x2x2 box is probably the max I can go, doesnt mean I will go for that much. I might make it like 21x21x24 also, depends upon the final choices I make.

 

[suri]

i guess then it will be a bash amp. difficult to get 1000w class d plate amp though, havent seen any so far on the web.

Hi doors666,

here is a 1000 watt class d subwoofer amplifier

Keiga KGND52100 (1000 Watt) Digital Plate Amplifier from Madisound

 

[doors666]

Well, I've seen peaks of about 30 watts on my mains, but rarely do we listen that loud. 10 watts average is par for the course, unless you have very insensitive speakers. Ironic as it may seem, smaller speakers are less efficient.

Large subs work well in large rooms, how big is yours?

And remember the SPL decreases with distance too, so it's not as open-and-shut as you think. A reach of 110dB is sufficient for most users in most rooms, unless you have no neighbors and everything is glued to the wall.

listening distance is about 12 ft. the room including the open kitchen and dining is about 6200 cuft.

the keiga is 550$, out of my budget.

It also doesnt have a subsonic filtter, would cost another 100$.

 

[GeorgeO]

Read Tom Nousaine's article about stuffing here:

http://www.nousaine.com/pdfs/Box Stuffing.pdf

Do a search on Tom Nousaine and you will find that he is a Guru's Guru.More info about him here:

Nousaine.com - The Archived Works of Tom Nousaine

There's a lot of interesting info on his site that can shed light on subs in general. Like this one( I liked his punchline in the last sentence):

http://www.nousaine.com/pdfs/Subwoofers How Big is Big Enough.pdf

 

[doors666]

I was just checking out the oaudio bash 500w amp. it has a boost (approx 3db) at the subsonic filter frequency. Is that a good thing? Is there a way to disable this.

 

[doors666]

I just asked my friend to pick up a css sdx-15 for me:yahoo:

Now I need to decide the amp. The oaudio has a 3 db boost at the hpf frequency which is variable (12, 16, 20, 25) as you can see in the figure posted in the previous post. This can be changed to any from 1 db to 5 db by changing a couple of resistors. Is this a risky 'operation'. Will the electronics shops guys (normal tv, radio etc fixers with small shops) be able to change the resistors easily, I am no good with soldering and havent seen a soldering iron after college and dont want to muck up the amp. Please advise.

The issue with amps is that most of the Parts express ones are 110 volts, including the bash amps. eD ones dont have subsonic filter but I have asked them about that. Keiga is too expensive (450$ for a 500w amp, ridiculous!!).

I need the following options in the amp:

1. plate amp, with 220volt support.
2. 500w (below 300, preferrably below 250), or 1000w (below 450$).
3. subsonic filter, preferrably 18hz. do the avrs have this inbuilt. does yamaha rx-v663 has one, couldnt find it in the manual.
4. low pass filter with 24 db/octave, not necessary though as i will be using my avr mostly.
5. Parametric equalizer will be good.
6. lfe and/or rca inputs. dont care about the speaker lvl inputs/outputs.

 

[GeorgeO]

Read this:

newbie wanting maelstrom, help and advice needed.

 

[psychotropic]

does this polyfill stuffing work only for subs, or does it do anything for other speakers? say bookshelves? (becuase the theory in tom nousaine's article seems like it should apply to any speakers) has anyone tried anything like that?

Read Tom Nousaine's article about stuffing here:

http://www.nousaine.com/pdfs/Box Stuffing.pdf

Do a search on Tom Nousaine and you will find that he is a Guru's Guru.More info about him here:

Nousaine.com - The Archived Works of Tom Nousaine

There's a lot of interesting info on his site that can shed light on subs in general. Like this one( I liked his punchline in the last sentence):

http://www.nousaine.com/pdfs/Subwoofers How Big is Big Enough.pdf

 

[GeorgeO]

Depends on the design. I have a couple of two ways, one of them has fibreglass stuffing, combined with felt lining, whereas the other one uses Black Hole 5 which is a expensive damping material.

George

 

[doors666]

my friend has ordered a dayton hpsa500 amp from PE for me.. finally all components are decided and ordered.

I would probably also need an SPL meter. any idea which are the good ones. I have a yamaha microphone that came with the 663, can I plug it in to the laptop's line in and record the spl levels? Will that give me accurate (or close enough) results.

 

[doors666]

Hi,

So the polyfill will help increase the effective volume of the box. The article does not talk about large ported designs and how much you will gain by polyfill. Does anyone have personal experience of using polyfill to gain volume.

Right now, I am getting smoothest frequency response by using a 7 cuft box tuned to about 20-21 hz with a 6" port, about 20" long. If I do decide to use polyfill, what sized box will give me an effective 7cuft volume, and by using how much polyfill. If it does not work and I do make a smaller box, my design will go for a toss and I will end up having everything wrong, and will result in a lot of work.

I can get polyfill from the mattress makers right? Any idea how much it will cost?

Regarding the port, I can use the plumbing pvc pipes available at the hardware store right? What diameters are these available at. I know I can get 2", 4", 6" etc. What about 3" and 5" etc. Are these available easily. What about cardboard pipes, the ones to keep drawing sheets etc or other posters etc. Can these also be used for the port? Any other options?

What about sonotubes, are there options available for these? Sorry, my discussions with my wife regarding the size are not getting anywhere and I need to check out all the possible options.

While designing the 7cuft one, my goal was to get a flat response and get teh -3db point as close to 20hz as possible. Some of the sites on the web recommend to get a lower tuning frequency, with a higher -3db point and let the room gain work as the room gain it seems is higher at lower frequencies.

If I drop the size to about 5 cuft, I loose a good 2-2.5 db in the 18-40hz range. rest of the range remains the same.

I have used the filters and power as per the docs of dayton amp. there is a 18hz hpf, which seems to be limiting quite a lot and according to simulations, I can go down to about 14-15hz for hpf without exceeding xmax of the driver. the documentation states I need to change three capacitors to lower the frequency. Is it a good idea? I do get a lot in terms of lower end response by lowering it to 14hz. Worth it? Can I get good capacitors here in india. Are these usually soldered to the PCBs.

 

[cmsajith]

Polyfill comes in 2 forms, Loose (what you see in a typical pillow) and as sheet (will be available with upholstery guys), sheet is preferred than the loose type since it is easy to glue.

5" pipes are available in KR Market, even i have plotted using 5" with 7cuft tuned to 20Hz. Probably I will be receiving the items within 2 days, reached bangalore.

Shifting the Hipass filter is possible. You can get the parts from PartsExpress itself (ask their technical dept., they are very quick in responding).

Edit: I just compared your plot @ 21Hz and Dayton @18Hz. It seems you could have used the 1000w amp, the cone excursion is well within the limits, till i gave 1400w. Also group delay seems to be lesser with RSS, almost same at 18Hz for CSS. Then why cant you tune it to 18Hz, any issues (comments welcome). What is exactly the meaning of -3db point? Also I could see the SPL is more with RSS less than 15Hz, why is it so?

 

[doors666]

Polyfill comes in 2 forms, Loose (what you see in a typical pillow) and as sheet (will be available with upholstery guys), sheet is preferred than the loose type since it is easy to glue.

5" pipes are available in KR Market, even i have plotted using 5" with 7cuft tuned to 20Hz. Probably I will be receiving the items within 2 days, reached bangalore.

Shifting the Hipass filter is possible. You can get the parts from PartsExpress itself (ask their technical dept., they are very quick in responding).

Edit: I just compared your plot @ 21Hz and Dayton @18Hz. It seems you could have used the 1000w amp, the cone excursion is well within the limits, till i gave 1400w. Also group delay seems to be lesser with RSS, almost same at 18Hz for CSS. Then why cant you tune it to 18Hz, any issues (comments welcome). What is exactly the meaning of -3db point? Also I could see the SPL is more with RSS less than 15Hz, why is it so?

1000w amp costed about 200$ more. I am getting 105db upto 25hz with just 50w. couldnt justify 200$ for 3 more db. anyway, if I feel the need, I can always upgrade to 1000w amp, probably ep2500 some day with equalizer and hpf.

tuning and size is what I am deliberating right now. the flattest response I get is at 7cuft/21hz. should that be the goal. I can lower the tuning frequency, that raises the spl at less than 20hz, but 20-30hz spl drops a lot if I do that. Also, no point in tuning it lower if I dont change the caps on the amp to change the hpf. I can tune it even lower then, upto 14-15hz looked good in winisd.
-3db point is frequency point where the output drops by 3db (half power). In winiSD, in the transfer function magnitude graph, its the yellow line.
Edit: I guess you meant what's the -3db point for this design, its 21hz. Sorry man!
to compare to the output of RSS below 15hz, remove the hpf from my design of css, then you'll see the actual output (its set to 18hz in the file I sent to u.

 

[cmsajith]

to compare to the output of RSS below 15hz, remove the hpf from my design of css, then you'll see the actual output (its set to 18hz in the file I sent to u.

I tried removing the hipass filter for both the subs, still it shows higher (till i changed the tuning to 23HZ) donno why..
Also i tried to change the tuning around 21 - 22. Now the Transfer Function Magnitude graph shows a bump in the 25 to 40Hz range. So i think for me its better i stick to 20Hz, or a 21\22 is better?

Also one more thing i noticed is that the max power requirement seems to be less than 3/4 of the amp power. So i just tried changing the power input to 300w (in my graph), even then the max power requirement is 200w. So i am confused about the extra headroom for the high power requirement. Whether this difference is enough before the amp starts clipping (almost all plate amps will have soft clipping also)? Please somebody clarify.. may be i am wrong

Sorry for hijacking your thread.

 

[doors666]

I tried removing the hipass filter for both the subs, still it shows higher (till i changed the tuning to 23HZ) donno why..
Also i tried to change the tuning around 21 - 22. Now the Transfer Function Magnitude graph shows a bump in the 25 to 40Hz range. So i think for me its better i stick to 20Hz, or a 21\22 is better?

Also one more thing i noticed is that the max power requirement seems to be less than 3/4 of the amp power. So i just tried changing the power input to 300w (in my graph), even then the max power requirement is 200w. So i am confused about the extra headroom for the high power requirement. Whether this difference is enough before the amp starts clipping (almost all plate amps will have soft clipping also)? Please somebody clarify.. may be i am wrong

Sorry for hijacking your thread.

yeah the curves are crossing at around 15 hz.

the bump is becuase for that size, the frequency is too high, so it gives more power in the lowest range its able to do. you can increase it further, the bump size will increase further. if you want to tune to 23hz, you'll have to reduce the size to get rid of the bump. for 7ft box, you need to tune lower or the bump will be there.

the max power varies inversely of the impedence. the amount of power withdrawn will depend upon the impedence the driver presents to the amp at a given frequency.

 

[cmsajith]

yeah the curves are crossing at around 15 hz.

the bump is becuase for that size, the frequency is too high, so it gives more power in the lowest range its able to do. you can increase it further, the bump size will increase further. if you want to tune to 23hz, you'll have to reduce the size to get rid of the bump. for 7ft box, you need to tune lower or the bump will be there.

the max power varies inversely of the impedence. the amount of power withdrawn will depend upon the impedence the driver presents to the amp at a given frequency.

I think it not a good thing hijacking your thread. I am continuing this in my sub build thread : http://www.hifivision.com/diy/5345-hi-all-diy-gurus-6.html#post74337

 

[doors666]

Yippeee. My driver is here. opened it and took a peek, havent removed it from the box yet, as the amp is not yet here, will come next week.
This thing is a monster.

 

[cmsajith]

Yippeee. My driver is here. opened it and took a peek, havent removed it from the box yet, as the amp is not yet here, will come next week.
This thing is a monster.

Great!!
Yes, its really a monster. What is that ring kinda stuff, rubber gasket?

Mine is still with the customs, arrived bangalore last week itself, but the shipper had put the From and To as my name!!, will be released this week.

 

[GeorgeO]

Good to know that you guys are on well your way to becomining committed bassaholics.So instead of wishing you gus Happy Diwali, I'll say "May the bass be with you!"

George

 

[sachi]

Looks like foam gasket for baffle sealing and damping.