Hi all,
Always been passionate about audio and DIY, but living in London has limited my options.
I have a selection of tools for electronics work, but very little space or tools to do woodworking and am without a workshop.
I currently run a DIY dual mono DUG TPA3116 integrated amplifier (LM4562 preamp stage) with a pair of Royd Sintra II speakers.
As part of a wider project, I'm looking to build a few components to upgrade the system, including a new amplifier, preamplifier and subwoofer.
This thread is for cataloging the design and build process of the subwoofer. My aim is a pragmatic balance between high quality sound and cost. I expect this build will take some months as I don't have lots of time to commit to the project.
Here's the plan so far:
50L internal volume sealed MDF enclosure with a 12" driver and DSP-capable plate amplifier. WinISD says this results in a Qtc of 0.732. With the MiniDSP, there's also the potential to apply parametric EQ to obtain a flatter response lower.
Amplifier
MiniDSP PWR-ICE125 in bridge mode to deliver 450w peak into 4 ohms
DSP capability allows for parametric EQ and room equalisation
Plate Amplifiers : PWR-ICE125
Driver
Scan-Speak Discovery 30W/4558T00
12" with 17Hz fs and +/-12.5mm of linear excursion
http://www.scan-speak.dk/datasheet/pdf/30w-4558t00.pdf
The thin blue line is the modelled response of the driver, untouched. The thick blue line is with 3.2db of gain applied at a centre frequency of 35Hz and a Q of 2.
Without the space to build the enclosure, I'll need to have this made. I've made early contact with some furniture manufacturers to see if any will take on the work. If anyone knows someone who could help with this and a decent finish (veneer would be ideal, but otherwise spray paint).
Any feedback at this point would be appreciated. Does anyone think I should seriously consider another driver?
Best,
Chris
Always been passionate about audio and DIY, but living in London has limited my options.
I have a selection of tools for electronics work, but very little space or tools to do woodworking and am without a workshop.
I currently run a DIY dual mono DUG TPA3116 integrated amplifier (LM4562 preamp stage) with a pair of Royd Sintra II speakers.
As part of a wider project, I'm looking to build a few components to upgrade the system, including a new amplifier, preamplifier and subwoofer.
This thread is for cataloging the design and build process of the subwoofer. My aim is a pragmatic balance between high quality sound and cost. I expect this build will take some months as I don't have lots of time to commit to the project.
Here's the plan so far:
50L internal volume sealed MDF enclosure with a 12" driver and DSP-capable plate amplifier. WinISD says this results in a Qtc of 0.732. With the MiniDSP, there's also the potential to apply parametric EQ to obtain a flatter response lower.
Amplifier
MiniDSP PWR-ICE125 in bridge mode to deliver 450w peak into 4 ohms
DSP capability allows for parametric EQ and room equalisation
Plate Amplifiers : PWR-ICE125
Driver
Scan-Speak Discovery 30W/4558T00
12" with 17Hz fs and +/-12.5mm of linear excursion
http://www.scan-speak.dk/datasheet/pdf/30w-4558t00.pdf
The thin blue line is the modelled response of the driver, untouched. The thick blue line is with 3.2db of gain applied at a centre frequency of 35Hz and a Q of 2.
Without the space to build the enclosure, I'll need to have this made. I've made early contact with some furniture manufacturers to see if any will take on the work. If anyone knows someone who could help with this and a decent finish (veneer would be ideal, but otherwise spray paint).
Any feedback at this point would be appreciated. Does anyone think I should seriously consider another driver?
Best,
Chris
Hi Chris,
Might be worth talking to Colin (Toppsy) here - MY own OB speaker project - audio-talk
He does commision builds on occasion. Did a pair of speakers for me a little while ago, and they came out great. They won't be particularly cheap, but he uses good wood, gets it CNC cut to spec, and knows all the tricks for veneers.
Depending on how loud you want to go, you can probably push a lot lower than 35Hz. Remember this, though - the mechanical limits are always in place. That driver in a sealed box will do 96.3dB at 20Hz (groundplane, 1m), and that's that. You can either apply EQ so that the entire range will be flat down to 20Hz with the knowledge that if you're listening louder than 96dB, if the music has any 20Hz content the sub will make some bad noises. You could aim for 30Hz instead, in which case it'll do 103.3dB.
The maximum SPL of a sealed sub is a function of cone area, excursion, and frequency. If you use a really big box, the low-end efficiency improves (Qtc goes down), meaning it takes less power to move the cone. A tiny box might need 1000w to hit the excursion limits, while an infinite baffle arrangement might need 100w. They will both produce the same mechanically-limited SPL.
When it comes to choosing the cabinet size, don't worry too much about Qtc. Ensure that you can use all of the mechanical travel of the driver with the power you have. That way, you're getting everything you can from the driver while using the smallest box you can.
I expect a single sealed 12" to be plenty for a UK living room, unless you're a home-theatre nutter and want to feel your body move at 5Hz. Check out AVS for that sort of thing.
FWIW, I'd seriously consider investing in some kind of measurement setup, and learn how to use it. Best audio-related money I ever spent - rooms do some nasty things to carefully-tuned LF alignments. One I worked in for a while had a 10dB spike at 40Hz. Made small speakers sound big, and big speakers sound ugly.
Chris
Might be worth talking to Colin (Toppsy) here - MY own OB speaker project - audio-talk
He does commision builds on occasion. Did a pair of speakers for me a little while ago, and they came out great. They won't be particularly cheap, but he uses good wood, gets it CNC cut to spec, and knows all the tricks for veneers.
Depending on how loud you want to go, you can probably push a lot lower than 35Hz. Remember this, though - the mechanical limits are always in place. That driver in a sealed box will do 96.3dB at 20Hz (groundplane, 1m), and that's that. You can either apply EQ so that the entire range will be flat down to 20Hz with the knowledge that if you're listening louder than 96dB, if the music has any 20Hz content the sub will make some bad noises. You could aim for 30Hz instead, in which case it'll do 103.3dB.
The maximum SPL of a sealed sub is a function of cone area, excursion, and frequency. If you use a really big box, the low-end efficiency improves (Qtc goes down), meaning it takes less power to move the cone. A tiny box might need 1000w to hit the excursion limits, while an infinite baffle arrangement might need 100w. They will both produce the same mechanically-limited SPL.
When it comes to choosing the cabinet size, don't worry too much about Qtc. Ensure that you can use all of the mechanical travel of the driver with the power you have. That way, you're getting everything you can from the driver while using the smallest box you can.
I expect a single sealed 12" to be plenty for a UK living room, unless you're a home-theatre nutter and want to feel your body move at 5Hz. Check out AVS for that sort of thing.
FWIW, I'd seriously consider investing in some kind of measurement setup, and learn how to use it. Best audio-related money I ever spent - rooms do some nasty things to carefully-tuned LF alignments. One I worked in for a while had a 10dB spike at 40Hz. Made small speakers sound big, and big speakers sound ugly.
Chris
Hi undefinedza,
The Scan-Speak 30W/4558T00 is a very nice driver that also does a great job for music. I wouldn't worry too much about excursion, just keep an eye on the rms power. Like Klippel explained/showed in his paper: “Nonlinear Modeling of the Heat Transfer in Loudspeakers”
Regards,
Djim
The Scan-Speak 30W/4558T00 is a very nice driver that also does a great job for music. I wouldn't worry too much about excursion, just keep an eye on the rms power. Like Klippel explained/showed in his paper: “Nonlinear Modeling of the Heat Transfer in Loudspeakers”
Regards,
Djim
Thank you all for your feedback!
@DiscoJones
I don't intend to go extremely low or loud with this subwoofer build, and I'm looking for a musically capable subwoofer more than anything else.
Excursion graph attached (using the params in my original post, 50L sealed + EQ). The driver's Xlim is 28mm, so there's some room before damage.
This is at 100w input power. SPL is 106db at 40Hz and 103db at 30Hz.
@chris661
You're spot on, as you can see 30Hz (f3) at 103dB at max excursion. The amplifier is specified to do 450w mono BTL, but I'm sure this is rated with a music crest factor. I think the amp and woofer are probably well matched power wise, in terms of the excursion limits.
Thanks for the tip on the measurement setup. Do you have any opinion of the MiniDSP UMIK-1, and more generally, their DRC tech?
I'll reach out to Toppsy.
@Djim
Thanks for this graph. The driver has an RMS Pe of 150w, which is a bit higher than the 100w that brings it to max excursion in the WinISD model, so hopefully the reality is there's a bit of power and excursion headroom.
Keep it coming!
Best,
Chris
@DiscoJones
I don't intend to go extremely low or loud with this subwoofer build, and I'm looking for a musically capable subwoofer more than anything else.
Excursion graph attached (using the params in my original post, 50L sealed + EQ). The driver's Xlim is 28mm, so there's some room before damage.
This is at 100w input power. SPL is 106db at 40Hz and 103db at 30Hz.
@chris661
You're spot on, as you can see 30Hz (f3) at 103dB at max excursion. The amplifier is specified to do 450w mono BTL, but I'm sure this is rated with a music crest factor. I think the amp and woofer are probably well matched power wise, in terms of the excursion limits.
Thanks for the tip on the measurement setup. Do you have any opinion of the MiniDSP UMIK-1, and more generally, their DRC tech?
I'll reach out to Toppsy.
@Djim
Thanks for this graph. The driver has an RMS Pe of 150w, which is a bit higher than the 100w that brings it to max excursion in the WinISD model, so hopefully the reality is there's a bit of power and excursion headroom.
Keep it coming!
Best,
Chris
Hi undefinedza,
The Scan-Speak 30W/4558T00 is a very nice driver that also does a great job for music. I wouldn't worry too much about excursion, just keep an eye on the rms power. Like Klippel explained/showed in his paper: “Nonlinear Modeling of the Heat Transfer in Loudspeakers”
Regards,
Djim
Hi Djim,
I'm afraid this post completely confuses my poor old brain!
I was aware that small voltage modelling is not completely accurate, but is this graph and text suggesting that all modelling software is junk below, say, 50-60Hz?
Or that we will need to plan into our system the need to supply X times the modelled power/voltage to achieve anywhere near the modelled/desired response curve?
Or that we need to build a subwoofer system twice as large as the modelling would suggest for our desired output??
Was that graph derived from just one driver being tested?
Surely the graph would be markedly different for different drivers with different materials and/or construction?
Is it likely that the soft-suspension drivers with low Fs, designed specifically for home theatre use, will not suffer the issues illustrated in the graph?
Was the 12.5mm linear excursion derived from the manufacturer's stated T/S parameters (therefore potentially 'optimistic') or actual measured parameters (therefore realistic)? If the former, would using a graph of the latter result in a better match between the lines?
I just find it hard to believe that all drivers would (under-)perform the same!
Maybe see the measurements on the Data Bass website.
For example, this 12" system was measured as having about 7dB LF loss when comparing high and low power - but the output doesn't begin to collapse until <30Hz.
Data-Bass
This 12" system doesn't have any LF loss when comparing high and low power.
Data-Bass
I have one and it was easy to set up, works well. I've dropped it a couple of times without harming it.
Hi Undefinedza,
I'm similarly in London and looking to do a sealed sub design, though my design criteria are probably a bit more "getto" - I'm looking to do something cheaper, maybe hacking some car-audio sub and box (placing a single sub in a double sub box but sealing the other opening - so lowering the response Q).
I checked you box/speaker parameters in this online calculator, I'm not sure on accuracy but it suggests 0.711 system Q.
The only thing that jumped out at me from your proposal is that peaking filter with a Q of 2 - is that in the MiniDSP? Given the high Q and low frequency that's going to possibly "ring" on for some time. Does the software allow you to view the time / step response and phase response - possibly you could be undoing all the benefits of the sealed design.
If it gives you the option it might be better to use a low-shelf filter topology, with a 2-pole low-shelf, setting the gain to +6dB and cutoff to 40 Hz (your -3dB point, assuming the filter is specified at the mid-point of the shelf slope) then the amplitude response would effectively be like shifting the light blue line in your graph to the left, so you still extend the 'flat' range but the response at 10Hz would be -18 not -24dB, and the phase / step response should be smoother.
I'm similarly in London and looking to do a sealed sub design, though my design criteria are probably a bit more "getto" - I'm looking to do something cheaper, maybe hacking some car-audio sub and box (placing a single sub in a double sub box but sealing the other opening - so lowering the response Q).
I checked you box/speaker parameters in this online calculator, I'm not sure on accuracy but it suggests 0.711 system Q.
The only thing that jumped out at me from your proposal is that peaking filter with a Q of 2 - is that in the MiniDSP? Given the high Q and low frequency that's going to possibly "ring" on for some time. Does the software allow you to view the time / step response and phase response - possibly you could be undoing all the benefits of the sealed design.
If it gives you the option it might be better to use a low-shelf filter topology, with a 2-pole low-shelf, setting the gain to +6dB and cutoff to 40 Hz (your -3dB point, assuming the filter is specified at the mid-point of the shelf slope) then the amplitude response would effectively be like shifting the light blue line in your graph to the left, so you still extend the 'flat' range but the response at 10Hz would be -18 not -24dB, and the phase / step response should be smoother.
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Sad to take a driver with a wonderfully low resonance (ummm, somewhat different on the spec versus the impedance curve) and stick it in a box barely bigger than itself (1.77 cu feet)... with the result that it poops out below 35 Hz. Weird: where do these recommendations for tiny boxes come from? No room for bigger box?
With modern lumber yards cutting panels to your specification and with good glues that expand to fill your errors, not hard to make boxes. Or to buy something from Ikea roughly to your size. Even if you need to buy a saw or two (and sell on eBay later), you are still on budget.
BTW, for music to sound good, you want an upward trending boost to your bass, not a flat response. Ask anybody.
B.
With modern lumber yards cutting panels to your specification and with good glues that expand to fill your errors, not hard to make boxes. Or to buy something from Ikea roughly to your size. Even if you need to buy a saw or two (and sell on eBay later), you are still on budget.
BTW, for music to sound good, you want an upward trending boost to your bass, not a flat response. Ask anybody.
B.
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MDF is not the best material to use, particularily for a sub. Its only asset is that it is cheap.
You already have an (just barely) undersamped alignment. Have you considered room gain. If anything you will probably use EQ to reduce the Q. At least with the miniDSP you can adjust once in place.
You might contact Stefan @ KJF audio. He would probably be willing to build a proper plywood box.
dave
I'm with you fellas
I have a pair of those woofers and absolutely they are a great choice. I created a list of many woofers and sorted them according to the Xmax * Cone Area divided by required sealed box volume. I wanted the most air moved for the smallest box size. The woofer you chose was one of the winners. I built the vented box using the size recommended in the data sheet. It sounds great, but like all resonant vented designs the transient response is crap. Your approach using the smaller box and electronic compensation is better. The smaller box dimensions move the panel and internal box resonances higher, and of course it is just lighter and smaller. I recommend measuring the woofer in box resonance and Q using something like Limp or Woofer Tester and then enter the values into the Linkwitz spreadsheet provided by miniDsp to calculate the perfect compensation filter coefficients to extend the bass response. You then just type the five filter numbers into the filter window on the miniDsp. I used it with an 8" woofer in a sealed 11" cube and extended the response down to 35 Hz and it works like a champ.
Here is a link to the Linkwitz Transform page at miniDsp
Linkwitz Transform
I have a pair of those woofers and absolutely they are a great choice. I created a list of many woofers and sorted them according to the Xmax * Cone Area divided by required sealed box volume. I wanted the most air moved for the smallest box size. The woofer you chose was one of the winners. I built the vented box using the size recommended in the data sheet. It sounds great, but like all resonant vented designs the transient response is crap. Your approach using the smaller box and electronic compensation is better. The smaller box dimensions move the panel and internal box resonances higher, and of course it is just lighter and smaller. I recommend measuring the woofer in box resonance and Q using something like Limp or Woofer Tester and then enter the values into the Linkwitz spreadsheet provided by miniDsp to calculate the perfect compensation filter coefficients to extend the bass response. You then just type the five filter numbers into the filter window on the miniDsp. I used it with an 8" woofer in a sealed 11" cube and extended the response down to 35 Hz and it works like a champ.
Here is a link to the Linkwitz Transform page at miniDsp
Linkwitz Transform
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"...don't worry about Qtc." Since when? At a Qtc of 2.0 it most definitely is going to "ring", and if that ringing frequency isn't exactly perfect, it will invoke Fourier to do its thing. Your choice of driver is of the "noncommittal" type, useful in sealed OR ported, but not optimized one way or the other.
------------------------------------------------------------------------------Rick.....
------------------------------------------------------------------------------Rick.....
Since he has a miniDsp to implement any biquad filter you like, the Qtc of the woofer in the box can be compensated for using the Linkwitz Transform, and it will definitely not ring.
Hello
Thank you all for your feedback!
@Richard Ellis, @olsond3: As @DiscoJones pointed out, the Q I was referring to was the parameter of the parametric EQ boost (which is one of many options the MiniDSP provides).
The Qtc of the system is around 0.732.
Thanks @DiscoJones!
More generally, I expect to play around with the DSP functionality once the thing is built to find the right configuration.
@olsond3: Glad to heard that the driver performed well in your analysis!
@planet10: I'll be ordering a UMIK-1 to measure the room gain and other room errors (REW) to apply correction with the MiniDSP.
Could you elaborate on your MDF comments?
@bentoronto: Unfortunately I don't have room for anything larger in my flat.
Do you have any alternate driver recommendations, and if so, what are their relative strengths over the SS driver given the size constaints?
As much as I *could* build an enclosure, without a workshop and decent woodworking tools or skills, I'm not going to be able to build something that looks really great. I'd also doubt the suitability of anything from Ikea as a subwoofer enclosure.
@PJ303: I was planning on adding the parametric EQ with the MiniDSP, but it looks like it also supports low-shelf filters (and custom biquad filters). I'll get a room correction curve from REW too. Thanks for recommendation!
@chris661: Will pull the trigger on the UMIK-1. Thanks again.
------
Some more general questions:
Current model size is 436*436*436, with a sealed compartment for the plate amplifier. The woofer compartment, with a double baffle (36mm), measures about 50L in volume, but that's without accounting for bracing and driver volume displacement.
1. Is the double baffle worth the reduction in available enclosure volume? 400x400x18 is about a 2.8L reduction.
2. Stuffing recommendations? I can line the inside with blanket. Should I be adding lambs wool or similar too? How might I model the outcome in terms of volume and/or Qtc?
I'll post the model after doing a bit more work on it. I need to figure out the best strategy for air vents in the plate amp compartment.
Have a good Sunday afternoon!
Chris
Thank you all for your feedback!
@Richard Ellis, @olsond3: As @DiscoJones pointed out, the Q I was referring to was the parameter of the parametric EQ boost (which is one of many options the MiniDSP provides).
The Qtc of the system is around 0.732.
Thanks @DiscoJones!
More generally, I expect to play around with the DSP functionality once the thing is built to find the right configuration.
@olsond3: Glad to heard that the driver performed well in your analysis!
@planet10: I'll be ordering a UMIK-1 to measure the room gain and other room errors (REW) to apply correction with the MiniDSP.
Could you elaborate on your MDF comments?
@bentoronto: Unfortunately I don't have room for anything larger in my flat.
Do you have any alternate driver recommendations, and if so, what are their relative strengths over the SS driver given the size constaints?
As much as I *could* build an enclosure, without a workshop and decent woodworking tools or skills, I'm not going to be able to build something that looks really great. I'd also doubt the suitability of anything from Ikea as a subwoofer enclosure.
@PJ303: I was planning on adding the parametric EQ with the MiniDSP, but it looks like it also supports low-shelf filters (and custom biquad filters). I'll get a room correction curve from REW too. Thanks for recommendation!
@chris661: Will pull the trigger on the UMIK-1. Thanks again.
------
Some more general questions:
Current model size is 436*436*436, with a sealed compartment for the plate amplifier. The woofer compartment, with a double baffle (36mm), measures about 50L in volume, but that's without accounting for bracing and driver volume displacement.
1. Is the double baffle worth the reduction in available enclosure volume? 400x400x18 is about a 2.8L reduction.
2. Stuffing recommendations? I can line the inside with blanket. Should I be adding lambs wool or similar too? How might I model the outcome in terms of volume and/or Qtc?
I'll post the model after doing a bit more work on it. I need to figure out the best strategy for air vents in the plate amp compartment.
Have a good Sunday afternoon!
Chris
Sealed box 50 litre sub with 15 inch Pro driver.
Hiya Chris,
I have attached a very nice 50 litre sealed box solution.
I use a pair of these at home for both music and movies... They sound amazing and I am happy to let you hear them (45 mins from central London).
With 500 watts one sub will hit 106dB at 30Hz before any wall / corner gain.
A major factor in all my loudspeaker designs is the vital importance of accurate time domain performance.
IMO this is best achieved with the following:
(1) Sealed box loading with low Q. ie 0.5 up to 0.7.
(2) Low Mms / High Bl for a 15 inch driver around 4.5 to 5.5 is optimal.
(3) DSP to Eq in room response and match existing speakers.
(4) Heavy ply wood cabinets. Approx 500 times the Mms of driver ie the attached Beyma has a Mms of 121g so the cabinet plus driver weight should ideally be around 60Kg. (24mm ply box with driver weigh around 40Kg). Also serious spikes required to anchor the cabinets to the floor.
Hope this helps and all the best
Derek.
Hiya Chris,
I have attached a very nice 50 litre sealed box solution.
I use a pair of these at home for both music and movies... They sound amazing and I am happy to let you hear them (45 mins from central London).
With 500 watts one sub will hit 106dB at 30Hz before any wall / corner gain.
A major factor in all my loudspeaker designs is the vital importance of accurate time domain performance.
IMO this is best achieved with the following:
(1) Sealed box loading with low Q. ie 0.5 up to 0.7.
(2) Low Mms / High Bl for a 15 inch driver around 4.5 to 5.5 is optimal.
(3) DSP to Eq in room response and match existing speakers.
(4) Heavy ply wood cabinets. Approx 500 times the Mms of driver ie the attached Beyma has a Mms of 121g so the cabinet plus driver weight should ideally be around 60Kg. (24mm ply box with driver weigh around 40Kg). Also serious spikes required to anchor the cabinets to the floor.
Hope this helps and all the best
Derek.
In a subwoofer the box is all about stiffness… you want to push any potential resonances up above the passband of the woofer.
Quality plywood is considerably stiffer than MDF, ie 15mm ply > 19 mm MDF. Hence it is easier to build a suitable box with ply than MDF, even using thinner material. That the box weighs considerably less is a bonus for your back, not to mention reduced toxicity.
The last subwoofer i built was near the same volume you are targeting, 44 litre. We built it from 15mm BB plywood, you could easily pick up the box with no drivers with one hand. With drivers, to be safe, it was a 2-man lift.
The design had the distinct advantage, in terms of box load, of being a pair of push-push 10” with their active vibration cancelation, but to get any of the panels vibrating i turned it up as loud as was comfortable, turned off the mains, and then added another 10 dB to the drive. It was the top and the planned slab of loosely attached corian on the top should fix that.
For a single 12” i would use well braced 18mm ply, with subwoofers just doubling the baffle to create the rebate is a good bet.
dave
I have that SS driver in a 50l sealed box and it is great for music.
The amplifier I use is an hypex 400 watt model it has bass boost but I don't use it as I find with room gain it is not needed.
You could try SL Hardwoods in Croydon to build a box for you .
They supplied all the panels for mine cut to size and I assembled it and finished it myself but I think they would make it for you if you gave them details.
The amplifier I use is an hypex 400 watt model it has bass boost but I don't use it as I find with room gain it is not needed.
You could try SL Hardwoods in Croydon to build a box for you .
They supplied all the panels for mine cut to size and I assembled it and finished it myself but I think they would make it for you if you gave them details.
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