The Project
I’m looking at building a SUB (or maybe 2) for music listening to add to the 2 way mains I’m building which are Troels CNO mkII’s. I will however be bi-amping and actively crossing these.
The SUB’s are to be sealed and passively driven by external amp’s from the 3rd crossover channels. Depending on how you look at it, it’s a 2 way setup with Subs or a 3 way setup.
- I’m expecting to cross at around around 120Hz-100Hz and go down smoothly to 40Hz (or slightly lower). Measuring will tell me what’s best.
- I’m trying to keep it small as possible this is not a deal breaker.
- The room this will be in is not that large (say 5m by 3.8m) and I’m undecided what consideration will suit. I’m weighing up 2 x 10” sealed, 1 x12” sealed vs 2x12” sealed
WinISD simulations & Questions
1. Drivers
I’m keen of the Scan-Speak 30W/4558T00 or the 26W/4558T00
- WinISD suggests the 30W/4558T00 could achieve a QTC or 0.71 in a 51L box with -3db gain at 37Hz
- For the 26W/4558T00 is suggests a 23L box (for QTC 0.71) with -3.1db gain at 47Hz and -5bd at 40Hz . The box size is quite a difference. I double checked the parameters from the spec sheet and they seem to be entered correctly. A 10” SUB in a 23 litre box sounds quite small…Any thoughts on this?
- I’ve also looked at the Peerless 835017 and found it to require a slightly larger box that other option (60L). This is also more expensive so I’ve ruled this out
The trade-off I see will be low end response vs. box size ( but I need to verify the WinISD calcs are correct 26W/4558T00 before I can confirm by what extent.
2. Box Shape
- WinISD suggests a rectangular box shape as optimum which I understand gives a better response that a cube. Is this true for sealed boxes? I notice a lot of sub’s built tend to be cubes.
3. Power AMP’s
How much power do I need to drive these speakers? They Scan-Speaks are both rated at 150W RMS at 4Ohms and Peak of 350W. I have an option for a 180W or 400W RMS amp into 4 Ohms (i.e. Hypex UcD180HG or the UcD400HG). Am I correct in assuming the smaller will provide more than enough clean power?
4. Do sealed Sub’s need cabinet dampening?
I’m looking at building a SUB (or maybe 2) for music listening to add to the 2 way mains I’m building which are Troels CNO mkII’s. I will however be bi-amping and actively crossing these.
The SUB’s are to be sealed and passively driven by external amp’s from the 3rd crossover channels. Depending on how you look at it, it’s a 2 way setup with Subs or a 3 way setup.
- I’m expecting to cross at around around 120Hz-100Hz and go down smoothly to 40Hz (or slightly lower). Measuring will tell me what’s best.
- I’m trying to keep it small as possible this is not a deal breaker.
- The room this will be in is not that large (say 5m by 3.8m) and I’m undecided what consideration will suit. I’m weighing up 2 x 10” sealed, 1 x12” sealed vs 2x12” sealed
WinISD simulations & Questions
1. Drivers
I’m keen of the Scan-Speak 30W/4558T00 or the 26W/4558T00
- WinISD suggests the 30W/4558T00 could achieve a QTC or 0.71 in a 51L box with -3db gain at 37Hz
- For the 26W/4558T00 is suggests a 23L box (for QTC 0.71) with -3.1db gain at 47Hz and -5bd at 40Hz . The box size is quite a difference. I double checked the parameters from the spec sheet and they seem to be entered correctly. A 10” SUB in a 23 litre box sounds quite small…Any thoughts on this?
- I’ve also looked at the Peerless 835017 and found it to require a slightly larger box that other option (60L). This is also more expensive so I’ve ruled this out
The trade-off I see will be low end response vs. box size ( but I need to verify the WinISD calcs are correct 26W/4558T00 before I can confirm by what extent.
2. Box Shape
- WinISD suggests a rectangular box shape as optimum which I understand gives a better response that a cube. Is this true for sealed boxes? I notice a lot of sub’s built tend to be cubes.
3. Power AMP’s
How much power do I need to drive these speakers? They Scan-Speaks are both rated at 150W RMS at 4Ohms and Peak of 350W. I have an option for a 180W or 400W RMS amp into 4 Ohms (i.e. Hypex UcD180HG or the UcD400HG). Am I correct in assuming the smaller will provide more than enough clean power?
4. Do sealed Sub’s need cabinet dampening?
All else ~ =, then the larger the Vas, the larger the cab, so with one having a Vas > 2x the other..... sure, one should be ~2x larger.
Right, all else ~ =, bigger box, more bass.
Small bass cabs whether sealed or vented are acoustically small relative to its passband WLs, so doesn't matter what shape it is, it just needs to be rigid, massive well sealed against leaks.
Build small sealed right and no damping is required, though folks normally line or stuff them anyway, just make sure if stuffing is used to contain it in a cheesecloth or similar 'bag' or use it to cover the back of the driver to keep it out.
Depends on who you ask, though normally you want at least as much as the driver rating unless you know for sure you only need a fraction of it like for an apartment, etc., or will be in a corner where there's significant room, boundary gain. It's hard to have too much power, just a point of diminishing returns, but doesn't sound good if you're hard into its limiter and maybe damage the driver too.
This is for HT, PA, amp choices, how to select, etc., but lots of good info that applies to any quality system: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System - Home Theater Forum and Systems - HomeTheaterShack.com
GM
Right, all else ~ =, bigger box, more bass.
Small bass cabs whether sealed or vented are acoustically small relative to its passband WLs, so doesn't matter what shape it is, it just needs to be rigid, massive well sealed against leaks.
Build small sealed right and no damping is required, though folks normally line or stuff them anyway, just make sure if stuffing is used to contain it in a cheesecloth or similar 'bag' or use it to cover the back of the driver to keep it out.
Depends on who you ask, though normally you want at least as much as the driver rating unless you know for sure you only need a fraction of it like for an apartment, etc., or will be in a corner where there's significant room, boundary gain. It's hard to have too much power, just a point of diminishing returns, but doesn't sound good if you're hard into its limiter and maybe damage the driver too.
This is for HT, PA, amp choices, how to select, etc., but lots of good info that applies to any quality system: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System - Home Theater Forum and Systems - HomeTheaterShack.com
GM
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With regards to sealed boxes, EQ and all that jazz...
- A larger box makes it easier for the cone to move, so it's more efficient at low frequencies. As a result, you'll need less power to get to Xmax. This is a Good Thing, since putting lots of power through a driver will always increase distortion.
- Any given driver has the same mechanically limited maximum SPL no matter the size of the cabinet. Changing the box size changes how much power you need to get to those mechanical limits. See point 1.
- Aiming for a particular Q-factor in a cabinet isn't much use when the room comes into play and messes everything up. If you're listening on an open area like a car park or field, then I expect you'll hear differences. Room effects are often an order of magnitude larger than the differences between Q=0.5 and Q=0.7. One room I've come across had a 10dB spike at 40Hz. Made small speakers sound big, and big speakers sound ugly.
- EQing is just the act of changing how much power is going to the driver. See points 1 and 2.
- Infinite baffles are the natural extension of the sealed box. They're very efficient at low frequencies, meaning you need very little power to run the drivers up to the excursion limits. Minimal power, minimal air pressure on the cones, so distortion is very low.
From point #3, I'd suggest you get hold of a measurement setup. You're looking at some fairly nice drivers. Measurement gear is useful forever, and doesn't cost much. I'd take the next drivers down with some well-done processing over nicer drivers and blind/no EQ.
To pick an amplifier, find one that'll get the drivers to Xmax before it clips. That way, you're making the most of the drivers without spending huge money on big amps. Note that you can make the cabinets bigger and use less power, so that's something to play around with.
These are just guidelines, but I hope they're useful.
Chris
- A larger box makes it easier for the cone to move, so it's more efficient at low frequencies. As a result, you'll need less power to get to Xmax. This is a Good Thing, since putting lots of power through a driver will always increase distortion.
- Any given driver has the same mechanically limited maximum SPL no matter the size of the cabinet. Changing the box size changes how much power you need to get to those mechanical limits. See point 1.
- Aiming for a particular Q-factor in a cabinet isn't much use when the room comes into play and messes everything up. If you're listening on an open area like a car park or field, then I expect you'll hear differences. Room effects are often an order of magnitude larger than the differences between Q=0.5 and Q=0.7. One room I've come across had a 10dB spike at 40Hz. Made small speakers sound big, and big speakers sound ugly.
- EQing is just the act of changing how much power is going to the driver. See points 1 and 2.
- Infinite baffles are the natural extension of the sealed box. They're very efficient at low frequencies, meaning you need very little power to run the drivers up to the excursion limits. Minimal power, minimal air pressure on the cones, so distortion is very low.
From point #3, I'd suggest you get hold of a measurement setup. You're looking at some fairly nice drivers. Measurement gear is useful forever, and doesn't cost much. I'd take the next drivers down with some well-done processing over nicer drivers and blind/no EQ.
To pick an amplifier, find one that'll get the drivers to Xmax before it clips. That way, you're making the most of the drivers without spending huge money on big amps. Note that you can make the cabinets bigger and use less power, so that's something to play around with.
These are just guidelines, but I hope they're useful.
Chris
GM - excellent response very helpful to my plans. Still working through how much power i really need to drive these SUB's and agree opinions vary on this.
- I recall somewhere 2.5 times speaking rating is a good guide to having sufficient clean headroom for peak speaker performance on tap.
- In another read on 3 way PA systems it talked to ratios of power typically required between LOWS, MIDS and HIGHS. There were degrees of freedom around this but from memory looked something like 50/30/20.
This is why I've put a 400W amp up for consideration for each SUB.
My hesitation is (assuming I build 2 SUB's) that it feels somewhat ridiculous to need 800W of power on tap plus the 500W I will have going to the CNO's (biamped) given the size of the room I'm planning on this going in.
I could be assured however, it will be clean.
- I recall somewhere 2.5 times speaking rating is a good guide to having sufficient clean headroom for peak speaker performance on tap.
- In another read on 3 way PA systems it talked to ratios of power typically required between LOWS, MIDS and HIGHS. There were degrees of freedom around this but from memory looked something like 50/30/20.
This is why I've put a 400W amp up for consideration for each SUB.
My hesitation is (assuming I build 2 SUB's) that it feels somewhat ridiculous to need 800W of power on tap plus the 500W I will have going to the CNO's (biamped) given the size of the room I'm planning on this going in.
I could be assured however, it will be clean.
Chris - you've been very helpful. I know bits & pieces around sound technology but need a little stretching to get where I want to land. Thankyou.
Can confirm that my plan to measure and set my crossover is a given. I have preamps and calibrated measurement mics at hand.
Cheers
First, I assume you're using WinISD Pro, which will show you a half space Xmax [or whatever limit you choose] power curve, so right away you've got a 400 W [peak] baseline and ignoring any room, boundary gain, you can see how much excess power you probably have over its intended BW and in most HIFI/HT apps any loss over distance is offset [and often then some] by how much this is, though never hurts to factor it in.
Then there's system efficiency to factor in and the greater it is, the less power required, ergo the lower its distortion: Power Handling Vs. Efficiency
Me and some others aren't convinced this test is all that accurate, but will give some more info to factor in: http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
Box size per se has no bearing on power handling capability: Efficiency and sensitivity conversion - loudspeaker percent and dB per watt and meter loudspeaker efficiency versus sensitivity vs speaker sensitivity 1 watt = 2,83 volt box chart - sengpielaudio Sengpiel Berlin
GM
Then there's system efficiency to factor in and the greater it is, the less power required, ergo the lower its distortion: Power Handling Vs. Efficiency
Me and some others aren't convinced this test is all that accurate, but will give some more info to factor in: http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
Box size per se has no bearing on power handling capability: Efficiency and sensitivity conversion - loudspeaker percent and dB per watt and meter loudspeaker efficiency versus sensitivity vs speaker sensitivity 1 watt = 2,83 volt box chart - sengpielaudio Sengpiel Berlin
GM
Simulations!
WinISD is a good tool, nice and easy to get started with. Look at the excursion graph, and change the power input.
A large sealed box will have excursion that increases as frequency goes down, so don't worry if you're exceeding Xmax at 1Hz. Your signal chain will have rolled off before then. Look at 10Hz or above, depending on how low you'd like to go.
You'll find that more power is needed to get the driver to bottom out at higher frequencies, so you might need 1KW to get all of the driver's mechanical potential at, say, 100Hz. Putting 1KW in at 20Hz would almost certainly destroy the driver, though.
Regarding GM's last point, a larger cabinet makes a driver more efficient at LF, which means you use more excursion (and get more SPL) per watt. It does change how much power you can put in before bad noises happen, but the resultant SPL will be the same.
Chris
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