Hi Chainenoble
Louis D. Fielder & Eric M. Benjamin, in their JAES article "Subwoofer performance for accurate reproduction of music", suggest there is a room gain of +12 dB/o starting (towards down) at 25 Hz in typical listening locations. So a closed box with a resonance around 25 Hz should suffice to get 12 Hz at 0 dB.
I have written a spreadsheet which calculates the rendition of a closed box in a typical location having a first room gain starting at 140 Hz (+1 dB) at a rate of +2 or +3 dB/o in the down direction and a second room gain starting at 25 Hz with +12 dB/o in the down direction. The resonance frequency and the Qtb of the enclosure are the input data, and the ouput is the THEORICAL response : it shows that with resonance frequencies less than 40 Hz, you can go with less than +/- 3 dB variations down to 12 Hz. Drop an email if you would like to receive this spredsheet I made using OpenOffice.
The problem is how to get a very low resonance frequency between 25 and 40 Hz. Many people on this forum suggest the most simple would be to use a Linkwitz transform. More elaborate solutions are either using Stahl's techniques or a servo-sub which lowers the resonant frequency by increasing the apparent moving mass (a fact almost unknown).
~~~~~ Forr
§§§
Louis D. Fielder & Eric M. Benjamin, in their JAES article "Subwoofer performance for accurate reproduction of music", suggest there is a room gain of +12 dB/o starting (towards down) at 25 Hz in typical listening locations. So a closed box with a resonance around 25 Hz should suffice to get 12 Hz at 0 dB.
I have written a spreadsheet which calculates the rendition of a closed box in a typical location having a first room gain starting at 140 Hz (+1 dB) at a rate of +2 or +3 dB/o in the down direction and a second room gain starting at 25 Hz with +12 dB/o in the down direction. The resonance frequency and the Qtb of the enclosure are the input data, and the ouput is the THEORICAL response : it shows that with resonance frequencies less than 40 Hz, you can go with less than +/- 3 dB variations down to 12 Hz. Drop an email if you would like to receive this spredsheet I made using OpenOffice.
The problem is how to get a very low resonance frequency between 25 and 40 Hz. Many people on this forum suggest the most simple would be to use a Linkwitz transform. More elaborate solutions are either using Stahl's techniques or a servo-sub which lowers the resonant frequency by increasing the apparent moving mass (a fact almost unknown).
~~~~~ Forr
§§§
chainenoble said:
forr said:
In a sealed box getting 20Hz at decent volumes is very difficult, the displacement needs increase a lot, a sealed box with the trapped air reduces the cone x max as air pressure increases inside the box.
I know about the servo subwoofers but there powerhandling is lower right? you need some kind of electronic circuit to compensate for the roll off and a very powerful amplifier.
Re: Re: sealed sub 15" 20hz or lower
Not true.
A linkwitz transform alignment in a sealed enclosure can get down to as low as the sub and amp will handle, so providing you've got a robust driver with a good strong motor, plenty of displacement and around 500-1000w your laughing. These things aren't particularly expensive nowadays either and you could build yourself some thing for around £600 quite easily.
I had a XXX 15" with 72mm of xmax peak to peak going flat to 15hz and with an SPL of ~105dB at 20hz, both in-room. That's both deep and loud, infact it was quite easy to scare yourself with it.
Iron-Wizard said:
Not true.
A linkwitz transform alignment in a sealed enclosure can get down to as low as the sub and amp will handle, so providing you've got a robust driver with a good strong motor, plenty of displacement and around 500-1000w your laughing. These things aren't particularly expensive nowadays either and you could build yourself some thing for around £600 quite easily.
I had a XXX 15" with 72mm of xmax peak to peak going flat to 15hz and with an SPL of ~105dB at 20hz, both in-room. That's both deep and loud, infact it was quite easy to scare yourself with it.
Re: Re: Re: Re: sealed sub 15" 20hz or lower
Its a circuit that changes the Q and Fs of the driver/box with the use of inverse equalisation to offset the rolloff to a point determined by the builder of the circuit.
Do a google on linkwitz transform and you'll get a load of hits. The best site to checkout is the Linkwitz lab.
Iron-Wizard said:
Its a circuit that changes the Q and Fs of the driver/box with the use of inverse equalisation to offset the rolloff to a point determined by the builder of the circuit.
Do a google on linkwitz transform and you'll get a load of hits. The best site to checkout is the Linkwitz lab.
My Lambda (2x15" ISO) was designed (using UNIBOX) at 110dB @50Hz, 104dB @20Hz & 93dB @10Hz in a 120litre box (4.25 cu. feet). All this using 18mm (one-way) xmax as my limiter. I've never measured it in-room, but it sounded fine - and a lot louder than I expected.
I'm just updating it now to fit in the box originally intended (1" MDF, bracing, good glue, damping, blah, blah, blah - and veneer). Then it'll be allowed in the house by my new partner (I hope).
I'm just updating it now to fit in the box originally intended (1" MDF, bracing, good glue, damping, blah, blah, blah - and veneer). Then it'll be allowed in the house by my new partner (I hope).
chainenoble said:
You probably already know that the adire Tumult 15d2 driver is a match made in heaven with the ada1200. The amp was designed with that specific driver in mind. I've just completed a DIY sub based on this driver. If you are looking for serious 20 Hz bass, this is an excellent way to go.
The 68 lb. beast comes in at $600 but is worth the price. If you are handy with wood and a decent painter, a serious sub could be put together for about $1100 (with an ep1500 amp). Add to this a Marchand Bassis, and for $1500 i'd match it against anything in the $2k class.
I ran a preliminary sweep in my 1,800 cu. ft. room and recorded 90 dB @ 20 Hz (6.5 meters) and 104 dB @ 28 Hz (2 meters) with less than 100 watts!(uncorrected). I should realize a 12-15 dB boost with the 1400 watt ep1500 and the Bassis on tap.
IMO, DIY is the most bang for the buck.
Attachments
You measured 105 dB in room at 20 Hz ShinOBIWAN ? With a XXX ?
That's nothing impressive if you ask me. My basic Shiva with 16 mm Xmax was doing around >115 dB at 20 Hz in room with a basic 250W amplifier.
I don't like Linkwitz Transform circuits, an awesome loss of efficiency and power. Not saying they are not useful, but I don't like them.
For chainenoble, you don't need a Tumult to use your amplifier. I would use something else because the price is too high IMHO. For the price of a single Tumult, you could buy 3 Acoustic Elegance AV12 and build 3 Thunder 12.3 enclosures with passive radiators. Performance to obliterate the Tumult if you ask me. Again that's a bit overkill, but you said the space was flexible!
That's nothing impressive if you ask me. My basic Shiva with 16 mm Xmax was doing around >115 dB at 20 Hz in room with a basic 250W amplifier.
I don't like Linkwitz Transform circuits, an awesome loss of efficiency and power. Not saying they are not useful, but I don't like them.
For chainenoble, you don't need a Tumult to use your amplifier. I would use something else because the price is too high IMHO. For the price of a single Tumult, you could buy 3 Acoustic Elegance AV12 and build 3 Thunder 12.3 enclosures with passive radiators. Performance to obliterate the Tumult if you ask me. Again that's a bit overkill, but you said the space was flexible!
simon5 said:
Notice how I didn't say how far the mic was from the sub when measuring or how large the room was. All very important.
If I put it under the stairs with the mic a couple of inchs from the cone I'm sure I could hit 120dB very easily.
You need the right sort of drivers to use them with. I wouldn't recommend trying it out with a couple of 'hifi' 8" drivers - which I have tried BTW.
It'll definitely take three my friend. But there is more than just spl to consider. I'm sure that adire's xbl^2 is a better motor topology. The distortion/BL characteristics of this driver has been expounded upon in many HT forums.
I prefer the Tumult over a pair of av-12's. I modeled these drivers for a few weeks before i decided to go the 15" route. It'll take more than two to equal the Vd and efficiency of a single Tumult. The SPLmaxLF (20 Hz -1/2 space @ 1m) is only 101 dB vs. 108 dB for the 15d2.
Again, it'll take more than two.
The cost factor, i think, is a rub, with 6-15" pr's and 3 separate enclosures. At $400 for the radiators, you could simply add two more av-12's...probably three, with the extra enclosure expenses. You would definitely have to build the boxes yourself to save "any" money. You could probably do two Tumults in a single vented enclosure for slightly more.
I prefer the Tumult over a pair of av-12's. I modeled these drivers for a few weeks before i decided to go the 15" route. It'll take more than two to equal the Vd and efficiency of a single Tumult. The SPLmaxLF (20 Hz -1/2 space @ 1m) is only 101 dB vs. 108 dB for the 15d2.
Again, it'll take more than two.
The cost factor, i think, is a rub, with 6-15" pr's and 3 separate enclosures. At $400 for the radiators, you could simply add two more av-12's...probably three, with the extra enclosure expenses. You would definitely have to build the boxes yourself to save "any" money. You could probably do two Tumults in a single vented enclosure for slightly more.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.