Question on big HT subs.

[manuelbauwens]

Hi all,


I'm planning on making two enclosures for my two 15" subwoofer I have laying around. I bought them a few years ago for a good price but they are actually more expensive Finish car subs. They are DVC drivers that can handle 700WRMS each and have a high excursion the brand is SPL Dynamics, here is a link to there specifications SPL Dynamics PRO Specs

My first thoughts are 2 BR enclosures of about 200l tuned to 15hz, I was playing around in WinISD and at full power they could each produce 109dB @ 15hz, if I increase the enclosure I eventually could get even a higher output...

I also could just tune it to 20hz it would give me an output of 114dB @ 20hz at full power as where it was only 109dB when it would have been tuned to 15hz.
15hz would be "produced" at only 105dB but probably "out of control" because below the tuning frequency...

What are your thoughts on this? I can't seem to decide what is most important, subsonic or just nice to 20... If I would go for the subsonic sub, I will use an other sub (the 12" version of the subs above) to cover the "higher" frequencies.

Thanks in advance!

[weltersys]

Originally Posted by manuelbauwens

My first thoughts are 2 BR enclosures of about 200l tuned to 15hz, I was playing around in WinISD and at full power they could each produce 109dB @ 15hz, if I increase the enclosure I eventually could get even a higher output...

I also could just tune it to 20hz it would give me an output of 114dB @ 20hz at full power as where it was only 109dB when it would have been tuned to 15hz.
15hz would be "produced" at only 105dB but probably "out of control" because below the tuning frequency...

What are your thoughts on this? I can't seem to decide what is most important, subsonic or just nice to 20...

Thanks in advance!

At 1000HZ, +10 dB sounds to your ear twice as loud, while at 20 HZ +5 dB sounds twice as loud.
I'd go for the 20 Hz tuning, giving away over half the volume level for some LF extension that will be used so little is a waste.

Art

[sreten]

Hi,

You seem to be chasing numbers rather than sensible sound quality.

200L cabinets for 80L Vas drivers is not really the way to do things.

Around 100L per driver tuned to 20Hz should work well with room gain,
it has a nice quasi first order rolloff shape over the low bass range.

Your twice as big cabinets will work, but not twice as well, or near that.

rgds, sreten.

[manuelbauwens]

Hi thanks for your replies!

weltersys, yes there is a big difference in output, maybe I should tune them both different, and have of each kind of cake a piece


sreten, are the "results" in WinISD not realistic? It shows me 5dB more output at 20hz with a 200l enclosure then with a 100l one...
The room where I will use it in is quite large about 120m3, I was guessing that I would not have to rely on a lot of room gain?
Is there a drawback on using big cabinets when the vas is quite low? Or will the practice be other then the theory?
I do not have much experience with the actual result of big enclosures for subs, except for one, 15 years ago I made a sealed 1000l enclosures for a 15" sub and it sounded like trash... lol

[revboden]

I'd put them in a 124l sealed box.

If you really want them in a vented box you'll have to tune high because the box volume won't be large enough to tune low and have a vent large enough to handle the air movement and fit in the box. For a vented box I also wouldn't go over 124L and tune to 25Hz but you'll need a High pass filter at 22Hz or excursion in movies will kill the driver.

edit: what do you want to use these for? movies, music, etc.

[sreten]

Hi,

The thing with subwoofers is output is only limited by cone area and excursion.

Your sim probably indicates 5dB more efficiency @ 20Hz requiring a lower power
amplifier, but i can assure you 100L tuned to 20Hz will go go just as loud with
more amplifier power, and its half the size.

Don't confuse max spl with frequency response, the former is fixed for a given
driver and correctly sized port, within those SPL limits you can EQ the driver
to any response you like, the box size determining the power needed.

Sealed for your driver is around 50L and vented should be ~ double.

Very big cabinets only increase efficiency, not maximum SPL, not usually
what you really want, which is the best compact performance of the driver.

[manuelbauwens]

Thanks, I would want them for movies.

How do you get to the value of 124l and not bigger? I really would like to go as low as possible and in WinISD it seemed possible with a larger enclosure?
Ofcourse I'm no expert so I just go by what the program displays me when I change different values...

[sreten]

Hi,

For movies I'd say 100L tuned to 20Hz and a sub amp with bass boost.
Bass boost of course changes how low it can go, but not max SPLs.
124L sealed is off any sensible alignment, max sealed volume would
be sensibly = to Vas = 80L, your chasing your tail going any higher.

But for HT sealed is not a good idea, vented goes a lot louder.

rgds, sreten.

[revboden]

I should explane the 124L limit, above that volume the Qtc drops below .5 which in my opinion sounds sloppy with non IB drivers (thats what they's designed for )

Even with ported boxes a too large enclosure will not give the driver the air spring it needs to keep things tight in the frequency range above the Helmholtz coupling.

[manuelbauwens]

Originally Posted by sreten

The thing with subwoofers is output is only limited by cone area and excursion.

Your sim probably indicates 5dB more efficiency @ 20Hz requiring a lower power
amplifier, but i can assure you 100L tuned to 20Hz will go go just as loud with
more amplifier power, and its half the size.

Don't confuse max spl with frequency response, the former is fixed for a given
driver and correctly sized port, within those SPL limits you can EQ the driver
to any response you like, the box size determining the power needed.

Sealed for your driver is around 50L and vented should be ~ double.

Very big cabinets only increase efficiency, not maximum SPL, not usually
what you really want, which is the best compact performance of the driver.

Thank you, I was looking to have a maximum SPL at a certain frequency and have a quite flat response in the area I wanted to use.

The max SPL I got by entering my amp power into the model, the frequency response by changing the tuning and size of the enclosure...

I added two screenshots of the SPL and frequency response at 700W.

If I understand it well I could get the same frequency response and SPL output in the 100l enclosure by simply equalizing?