Just a tale about work in progress, who's only moral is to consider your options and choices carefully. This is about making a "simple sub" from stuff on hand- for testing with the development version of my monolith line array, and to use in my bedroom system.
I'm getting ready to resume work soon on the RD50 based line array, and prior to building the final cabinets, especially the woofer boxes, I wanted something to work with them for the bottom end. Being my usual penurious self, I figrure I could toss something together with bits and pieces I have lying around... don't want to spend any moolah right now on this. Since I've got a few drivers on hand, seems like I have some choice to work with. Twelve inch drivers I have "in stock" include the Adire Shiva, the Blueprint 1203 (which I'm planning for the finished version of the monolith, using an LT equalizer), Titanic MkII's, and Adire DPL12's.
It's times like these that I'm really thankful to Christian Ouugard and his wonderful program, "Unibox". IMO, it's the easiest and most power ful LF analysis program you can get, and what's even better, is it's free, as long as you have Excel 2000 or later to run it on. I have a copy of Bass Box Pro which has languished in the dust bin now for some time, since I started using Unibox 2.33, now up to version 4.03. You can get it here:
Unibox
Using Unibox is a breeze, because though it can handle advanced LF simulation parameters if you have them for the driver, it doesn't need much to get a good driver model- Fs, VAS, Qes, Qms, Xmax, and Sd, and you're in the ballpark. It calculates all the others from these parameters, so you can do a sanity check on the model as well as the T/S parameters. It's pretty amazing to see it come up within a couple of percent on the estimated cone mass, suspension compliance, Qts, etc., that are on the manufacturer's spec sheets.
Anyway, for a simple sub, I don't need anything fancy- what I want is maximal LF extension in the NOS Woodstyle 62 liter sub cube I have in the original carton in my garage. And with Unibox you can readily calculate the response, including the limitation on acoustical output due to driver Xmax, Sd, etc.
So which do I use in my simple sub, and why?
Well, the choice is simple, really, after reviewing the data. I'm using the "dipole" driver, the Adire DPL12, in my sealed sub. Why? Well, though it's a couple of dB less efficient in midband sensitivity, for a sub, it's what you get down low that counts, and what the overall balance is. From the upper midbass, say 100 Hz, the -6 dB point is what's of interest to me, as well as the Q and roll off rate. With good room placement, and typical room gain, you can get the -6 dB point pretty much flat in room. The -6 dB point for the DPL12 in this box is 22 Hz!! For the other drivers, it's about 30 Hz. With a little more box volume, say, 75 liters, you can get the -6 dB point at 20 Hz, with a Bessel alignment on the roll off, which means the Q is pretty much minimum delay, and nearly critically damped.
Frankly, if you don't have the room or architectural support for a true IB sub, using arrays of the DPL12 in 75 liter boxes will give you essentially the same thing. The F10 is 15 Hz in the 75 liter configuration. Light shelving EQ, and I mean lite, say, 4 dB, could bring you to in room flat to 15 Hz. With multiple drivers, we could have some serious fun tonight. OTOH, it doesn't roll off the tongue the same way as "Twelve Shiva's Dancing".
Max anechoic output at 1 meter at 20 Hz is 98 dB. With room gain, about 104. Two would give you 110. Four would net in room about 116. You get my drift? No EQ required for that, either. Power required is about 150 watt per driver, allow 300 watts at four ohms for headroom on transients at higher frequencies- that would give you about 105 dB at 1 meter anechoic at 30 Hz. Call it 110 with room support.
Bottom line? For ported systems, with EQ and HP filters, go ahead with your Shiva or Titanic MkII. For simple, wideband, excellent time domain performance in a sealed box, make it a good dipole driver- the Adire DPL12.
I also evaluated Isobarik, and my conclusion was that the gain below 30 Hz in Fs wasn't worth the expense- the DPL12 has a curve a lot like Isobarik Shivas, but with 2 dB less sensitivity, and only a single driver.
What's not too like?
I'll be building this shortly, and document the process and the results. Let's see how Unibox predictions stack up against the real world on this one.
Regards,
Jon
Earth First!
_______________________________
We'll screw up the other planets later....
I'm getting ready to resume work soon on the RD50 based line array, and prior to building the final cabinets, especially the woofer boxes, I wanted something to work with them for the bottom end. Being my usual penurious self, I figrure I could toss something together with bits and pieces I have lying around... don't want to spend any moolah right now on this. Since I've got a few drivers on hand, seems like I have some choice to work with. Twelve inch drivers I have "in stock" include the Adire Shiva, the Blueprint 1203 (which I'm planning for the finished version of the monolith, using an LT equalizer), Titanic MkII's, and Adire DPL12's.
It's times like these that I'm really thankful to Christian Ouugard and his wonderful program, "Unibox". IMO, it's the easiest and most power ful LF analysis program you can get, and what's even better, is it's free, as long as you have Excel 2000 or later to run it on. I have a copy of Bass Box Pro which has languished in the dust bin now for some time, since I started using Unibox 2.33, now up to version 4.03. You can get it here:
Unibox
Using Unibox is a breeze, because though it can handle advanced LF simulation parameters if you have them for the driver, it doesn't need much to get a good driver model- Fs, VAS, Qes, Qms, Xmax, and Sd, and you're in the ballpark. It calculates all the others from these parameters, so you can do a sanity check on the model as well as the T/S parameters. It's pretty amazing to see it come up within a couple of percent on the estimated cone mass, suspension compliance, Qts, etc., that are on the manufacturer's spec sheets.
Anyway, for a simple sub, I don't need anything fancy- what I want is maximal LF extension in the NOS Woodstyle 62 liter sub cube I have in the original carton in my garage. And with Unibox you can readily calculate the response, including the limitation on acoustical output due to driver Xmax, Sd, etc.
So which do I use in my simple sub, and why?
Well, the choice is simple, really, after reviewing the data. I'm using the "dipole" driver, the Adire DPL12, in my sealed sub. Why? Well, though it's a couple of dB less efficient in midband sensitivity, for a sub, it's what you get down low that counts, and what the overall balance is. From the upper midbass, say 100 Hz, the -6 dB point is what's of interest to me, as well as the Q and roll off rate. With good room placement, and typical room gain, you can get the -6 dB point pretty much flat in room. The -6 dB point for the DPL12 in this box is 22 Hz!! For the other drivers, it's about 30 Hz. With a little more box volume, say, 75 liters, you can get the -6 dB point at 20 Hz, with a Bessel alignment on the roll off, which means the Q is pretty much minimum delay, and nearly critically damped.
Frankly, if you don't have the room or architectural support for a true IB sub, using arrays of the DPL12 in 75 liter boxes will give you essentially the same thing. The F10 is 15 Hz in the 75 liter configuration. Light shelving EQ, and I mean lite, say, 4 dB, could bring you to in room flat to 15 Hz. With multiple drivers, we could have some serious fun tonight. OTOH, it doesn't roll off the tongue the same way as "Twelve Shiva's Dancing".
Max anechoic output at 1 meter at 20 Hz is 98 dB. With room gain, about 104. Two would give you 110. Four would net in room about 116. You get my drift? No EQ required for that, either. Power required is about 150 watt per driver, allow 300 watts at four ohms for headroom on transients at higher frequencies- that would give you about 105 dB at 1 meter anechoic at 30 Hz. Call it 110 with room support.
Bottom line? For ported systems, with EQ and HP filters, go ahead with your Shiva or Titanic MkII. For simple, wideband, excellent time domain performance in a sealed box, make it a good dipole driver- the Adire DPL12.
I also evaluated Isobarik, and my conclusion was that the gain below 30 Hz in Fs wasn't worth the expense- the DPL12 has a curve a lot like Isobarik Shivas, but with 2 dB less sensitivity, and only a single driver.
What's not too like?
I'll be building this shortly, and document the process and the results. Let's see how Unibox predictions stack up against the real world on this one.
Regards,
Jon
Earth First!
_______________________________
We'll screw up the other planets later....
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