I'm wanting to build some dual subs for my system before the end of the year on as low of budget as I can manage given my needs, namely that I'd like between 110 and 115b of output at 20hz-90hz if possible, and that the dimensions not exceed 20in wide * 20in deep * 78.7in height.
I'm fully on board with using DSP to get there and smooth any troublesome peaks.
The design most appealing to me currently is the VBSS given a low cost of ~100 for drivers + 100 in materials per sub, however the inuke amplification required could potentially bring the cost up to 600USD... farther than I'd like to go if I can help it.
I currently have about 16 channels of 220W @ 8ohm amplification thanks to two ATI built Crestron CNAMPX-16X60s. Very clean, low distortion power. Given that I won't be most of those channels any time soon, I'm wondering if I could use that power to drive subs instead, and save money on having to buy yet more amplifiers?
I know some designs like tapped horns can get you more output for your watt... would that be a possible option? I know there would be some crazy peaks in the xover region, but I imagine those could be deal with via DSP. Dual voice coil driver could also be a way of getting more of my amplifier's power to the driver?
The Eminence 20Hz Tapped Horn – Volvotreter Homepage <- This horn seems like it'd check most of my boxes, but at 240cm it's slightly too tall (200 is more my limit), and the drivers listed are pricier than I'd prefer (would like to try and keep it to 100 per driver).
Currently trying to educate myself on hornresp but I've a lot of learning to do. In the mean time, any advice y'all have would be greatly appreciated!
I'm fully on board with using DSP to get there and smooth any troublesome peaks.
The design most appealing to me currently is the VBSS given a low cost of ~100 for drivers + 100 in materials per sub, however the inuke amplification required could potentially bring the cost up to 600USD... farther than I'd like to go if I can help it.
I currently have about 16 channels of 220W @ 8ohm amplification thanks to two ATI built Crestron CNAMPX-16X60s. Very clean, low distortion power. Given that I won't be most of those channels any time soon, I'm wondering if I could use that power to drive subs instead, and save money on having to buy yet more amplifiers?
I know some designs like tapped horns can get you more output for your watt... would that be a possible option? I know there would be some crazy peaks in the xover region, but I imagine those could be deal with via DSP. Dual voice coil driver could also be a way of getting more of my amplifier's power to the driver?
The Eminence 20Hz Tapped Horn – Volvotreter Homepage <- This horn seems like it'd check most of my boxes, but at 240cm it's slightly too tall (200 is more my limit), and the drivers listed are pricier than I'd prefer (would like to try and keep it to 100 per driver).
Currently trying to educate myself on hornresp but I've a lot of learning to do. In the mean time, any advice y'all have would be greatly appreciated!
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Well sure. And offhand your numbers seem achievable. But it would help if you specified:
- How many of those channels won't you be using?
- 16x220=3,520 watts. That will pop a typical breaker. What is your electrical supply to this? Because at these extremes it is silly to consider just the amps and speakers without considering if your wall outlet can keep up.
- DSP is fine but as loudspeaker designer I've always felt it is far better to avoid problems in the first place. All those compensations are based on some kind of measurement which may not really be quite what is happening under dynamic conditions.
- Speaking of DSP, can you implement time-based room EQ in whatever you have? Calculating all this stuff without considering the room may be OK as a first step but certainly not a complete answer.
- Can your ATI channels bridge? If so what is the rating? I do not like loading amps down heavily, I feel on admittedly scanty evidence that you don't get much if any additional power at clipping under dynamic conditions, but you DO reduce efficiency and get more heat.
- But I'm not aware of DVD PA-type woofers either. If anyone knows some I'm very curious!
- In your case *maybe* two smaller subs would be better? You could use 2 amp channels, and the subs could load each otheer-and, depending on your space, position them in the room to counteract room modes. Tough to port 20 Hz in smaller cabinets though, especially with big enough ports to flow enough air.
But it's not 16 x 220! That Crestron, IIRC, is 16 x 45W @8Ω, or, 16 x 90W @4Ω. And, only some of the channels can be bridged and definitely not all of them, pretty sure only half the channels can be bridged.
@djeddie: each Crerstron unit is 16*60w @ 8ohm, with each stereo channel being powered by one modular amplification PCB. Bridging the stereo channels on one PCB results one 220w @ 8ohm channel with 0.03% THD at full power. I have two of these amplifiers, hence a potential total of sixteen 200-220w channels.
The modular amps in the Crestron are the same that ATI used when building monoprice's 7 channel monolith amp, but already internally bridged, so it's definitely possible to bridge almost all of the PCBs. Just have to make sure it can cool itself well enough.
I guess I was figuring tower subs (either a horn or a ported cabinet) would be preferable as I could potentially get more low end output with less power? I plan on starting with two and working out from there.
The modular amps in the Crestron are the same that ATI used when building monoprice's 7 channel monolith amp, but already internally bridged, so it's definitely possible to bridge almost all of the PCBs. Just have to make sure it can cool itself well enough.
At this point I only use LCR with no surrounds or overhead speakers, so one of the amplifiers is being used for those three channels. I'll likely use the remaining channels to power an Atmos setup or perhaps to power DIY active xover speakers, but that's years in the future and not of immediate concern.
The plan is to use a PC for all DSP processing of all channels, and for crossovers as well. As such, FIR and IIR based filtering are on the table.
The 220WPC is with the stereo PCB units bridged. Each amplifier has two MASSIVE toroidal transformers, so I'd use one sub per transformer to. The amplifier is rated at 0.003% THD with all channels driven at full power, so I don't have concerns about the load as long as I'm not drawing much more than 200 watts continuous @ 115db.
I guess I was figuring tower subs (either a horn or a ported cabinet) would be preferable as I could potentially get more low end output with less power? I plan on starting with two and working out from there.
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@Redskin: Channels 1 and 2 are on the same PCB, and bridging them results in a single channel rated at 220W @ 8ohms with 0.03% THD. That's what ATI specifies.
The Crestron user manual recommends that only channels 1-4 and 13-16 be bridged, but this is most likely to prevent any chance of over heating. Like I said in a previous post, ATI's monoprice 7 channel amp has 7 of the 200W stereo PCBs internally bridged without problems. Additionally I'm going to be installing these amps in a rack mount with active cooling, so they'll be fine.
In any case the original post still stands: I'd like to use two of the ~200W 8ohm channels to drive two subs capable of hitting 110-115 dB @ 20hz. Is there a design that can get me there?
The Crestron user manual recommends that only channels 1-4 and 13-16 be bridged, but this is most likely to prevent any chance of over heating. Like I said in a previous post, ATI's monoprice 7 channel amp has 7 of the 200W stereo PCBs internally bridged without problems. Additionally I'm going to be installing these amps in a rack mount with active cooling, so they'll be fine.
In any case the original post still stands: I'd like to use two of the ~200W 8ohm channels to drive two subs capable of hitting 110-115 dB @ 20hz. Is there a design that can get me there?
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OK all is clearer and now I understand I missed "dual subs." So you're dumping let's round to 400 watts = 26 dBW into two subs, which will load each other. Either I'm getting delirious in the sun-possible!-or that should gain another +6 dB at 20 Hz, for +32 dB gain over one watt. So to hit 100 dB, subtracting a wildly arbitrary 10 dB to the listening position, if one sub can do 88 dB/1W/1m in a half-space simulation it should work.
I can't comment about the VBSS or other designs-is that ported down to 20 Hz? Why do you want 20 Hz by the way? Specialized music? Movies? Because for movie FX 20 might not be low enough and for most music it's probably lower than you need (nothing wrong with that).
Instead of going with a singe driver you can go multiple smaller ones, while 4 may be overkill there are huge advantages to go in multiples of 2 as you can cancel pretty much all the mechanical forces in such a setup.
Inverting half of the drivers also reduces driver distortion since if you take 2 drivers that combined push-pull at the same time now the outwards stroke is the same as the inwards stroke -> less distortion.
You want to keep the drivers as close as possible though, in my example I have drawn selaed sub with a open slot at the front with 4 drivers in a push-pull configuration.
Inverting half of the drivers also reduces driver distortion since if you take 2 drivers that combined push-pull at the same time now the outwards stroke is the same as the inwards stroke -> less distortion.
You want to keep the drivers as close as possible though, in my example I have drawn selaed sub with a open slot at the front with 4 drivers in a push-pull configuration.
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