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SVS SB-1000 - inside pics, personal thoughts

trl

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Just got few days ago my second SVS SB-1000 and I thought it would be nice to see what's inside the box and "how it works". This one is the black-ash (MDF with sort of melamine foil on the outside) and the "old one" is a black-gloss (MDF with veneer glossy on the outside).

IMG_20190619_190253.jpg


InkedIMG_20190619_195912_LI.jpg


IMG_20190619_194648.jpg

The MDF cabinet has a thickness of 1.5 cm and the four inner walls are covered on the inside with 5 cm thick acoustic absorbent pollyfill. Quite a generous amount of damping material I'd say, although I've added one more piece myself between the electronic parts and the driver, just to be sure the reflections will get lowered inside even further (not quite a recommended modding and probably not necessary, but usually the rear side of the sub might need some sort or damping).

IMG_20190619_195633.jpg


IMG_20190619_195709.jpg


IMG_20190619_184827.jpg


The SMPS power supply delivers 53.3 to the black-melamine subwoofer and 53.9V to the piano-black one, so the last one is more powerful. :) It doesn't seems to be a dual power supply as I can only see a red and black wire connected from PSU to the amp's PCB. There is also an additional dual +/-7V rail to power up the digital control parts (DSP).

IMG_20190619_194840.jpg


IMG_20190619_180736.jpg


IMG_20190619_195323.jpg


The amplifier itself is a SVS proprietary SLEDGE STA-300D able to deliver 300 W of RMS power, with peaks up to 720 W.

IMG_20190619_200025.jpg


The connection from the speaker to the amplifier seems to be bridged, so the two pairs of cables are paralleled on the driver side, then it's getting to separate PCB plugs. Cables are really thick, probably 1.5mm2 each one of them, so really good thing.

IMG_20190619_173928.jpg


Between the back plate, also used as heatsink, and the PCB there's a piece of rubber/foam used to electrically isolate the PCB from the back plate, but also to damp the internal sound-waves.

IMG_20190619_194909.jpg


On the amplifier's PCB I can identify:
- One TL064C quad operational amplifer made by ST that probably deals with the two stereo inputs from RCA and Speakers-Out.
- An AKM5358AET A/D converter, probably used to get the analogue inputs from the above opamp into the DSP.
- One STA309A multi-channel digital audio processor with DDX® (https://www.st.com/en/audio-ics/sta309a.html) that should take care of the Low-Pass Filter and all the necessary DSP corrections, based on the volume setting and frequency response. It should be programmed this way to correct imperfections of the subwoofer and provide a clean and proper bass response.

IMG_20190619_195459.jpg


IMG_20190619_195530.jpg


I can't see what type of Class-D power amplifiers are under the heatsink, but given the 36-pin I thought it might be TDA7498, but looking to https://www.st.com/en/audio-ics/class-d-audio-power-amplifiers.html#products I realized that there's no chip there able to be powered from 53V, so it should be some chip from https://www.st.com/en/audio-ics/digital-audio-power-amplifiers.html#2. Probably STA516BE seems to be able to deliver in mono-BTL configuration 400 W into a 3 Ω load with THD = 10% at VCC= 52 V, based on the datasheet.

IMG_20190619_195347.jpg


SB-1000 and PB-1000 share the same speaker driver and my DMM shows a DC-resistance of 3.5 Ohms, so based on the above I'd say that the 300 W RMS power provided by the manufacturer is a real number and that's probably achieved with a THD definitely lower than 10% (probably more close to 1% than to 10%).

On the SMPS power supply board can be seen:
- One TL494L made by UTC
- Couple of MOSFET transistors (can't see the model, probably hard to find ones).

IMG_20190619_195323.jpg


IMG_20190619_175357.jpg


I subjectively think that the SMPS inside is the weak link here, it just doesn't looks to be able to sustain the power that the bridged chips could deliver when used in mono-BTL. Of course, the heatsink is not the best one too for a closed-sub that lacks real ventilation inside, but in the end power supply & amplifier & speaker/driver seem to blend pretty nice to the final specs of the entire subwoofer.

I find the sound as being fast and accurate, maybe not the best punch ever, but given that I'm speaking about a closed-sub that can almost shake an apartment or even a small house down to 24 Hz, then it's good enough for my small home too, especially in a dual configuration like I'm using. In compare with my Mackie MR10Smk3 the output power is higher, the sub-bass is more present and the kick & slam is bigger as well.

In my living-room setup, with a stereo set made of Yamaha A-S701 and CANTON GLE 496 with two woofers per speaker, I'm pretty comfortable with the final kick and slam with the low-pass filter on SB-1000 set to around 75-80 Hz and the volume to about 12 o'clock. When getting over 100 dB of SPL the kicking is really good and the chest is getting the right amount of "vibrations", well...at least when listening to some hits like "Cardi B, Bad Bunny & J Balvin - I Like It" or "Minelli - Mariola" or any contemporary hit that has a huge amount of sub-bass. :)

As a low-light, worth mentioning that after 90 dB SPL these subs are vibrating on the floor, so either the SVS shock absorber feet needs to get purchased, either some carpet needs to be placed under the default original feet (that's what I did).

IMG_20190619_195840.jpg
 
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GrimSurfer

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Thanks for the write up.

I've often wondered if anybody with decent wood working tools could build better enclosures for entry level subs. After all, it is the enclosure that accounts for about half the price of a loudspeaker and "built like a brick shit house" isn't something that appears on spec sheets.

Based on your report, the cabinet for the SVS SB-1000 is 3/4" (nominal) MDF. Whether the front and back panels use material of the same thickness is anyone's guess, as this is sometimes where corners are cut. There doesn't appear to be any internal bracing which has some performance implications.

MDF can be a PITA to work with. It doesn't take glue or screws all that well. On the up side, it doesn't contain voids and is about as non resonant a material as one can commonly get...
 

Ron Texas

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Thanks for the write up.

I've often wondered if anybody with decent wood working tools could build better enclosures for entry level subs.

Based on your report, the cabinet for the SVS SB-1000 is 3/4" (nominal) MDF. Whether the front and back panelsuse material of the same thickness is anyone's guess, as this is sometimes where corners are cut. There doesn't appear to be any internal bracing, which has greater implications in a sealed design.

MDF can be a PITA to work with. It doesn't take glue or screws all that well. On the up side, it doesn't contain voids and is about as non resonant a material as one can commonly get...
There are plans somewhere for a DIY sub built out of a 5 gallon paint can with concrete added.
 

GrimSurfer

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I have a few bags of concrete in the shed... but that is for another project. (Need to move James R. Hoffa?)

I might try my hand at building a sub enclosure towards the end of the summer...
 
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trl

trl

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[...]
Based on your report, the cabinet for the SVS SB-1000 is 3/4" (nominal) MDF. Whether the front and back panels use material of the same thickness is anyone's guess, as this is sometimes where corners are cut. There doesn't appear to be any internal bracing which has some performance implications.[...]

Front and back panels thickness is the same, but the back panel has also attached the PCBs onto the metal sheet, probably 1 mm thickness of metal sheet or so, can't say exactly. This actually acts as a heatsink, transferring the heat from the two power chips.

Given the relatively small size and weight there's no need for internal brackets. The bigger subs have much more weight and, of course, some internal reinforcement bracketing:

92121f03_DSC_0387.jpeg

PB-2000

svs_pb16_ultra_gblk_5_.jpg

PB-3000

AVimg_21031.jpg

PB-4000

L.E.: SB-2000 has no brackets inside:
, while PB-1000 has: https://www.avsforum.com/photopost/data/2276845/2/21/21cca5bb_file_zps2b0fbb58.jpeg . Based on the above, it seems that internal brackets are a must for ported subs, but not required for compression subs.
 
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gino1961

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The woofers in the PB series look like complete different animals to me :oops::oops::oops: Much more robust drivers :rolleyes:
At higher price levels i am not convinced that a powered sub is better than a passive sub with an external power amp ...
 
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trl

trl

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Actually, I think that a passive sub might be better than an active sub, because if using the same box, the volume of air inside is higher on the passive sub (lacks the amplifier and PSU) and there're no wires and components inside to reverb and ding-ding and blink-blink. Also, speaker's coil will be cooler on a passive sub, due to the missing active components inside to generate heat.

Also, on an active sub most of subwoofer's vibrations are "hitting" the power amplifier inside and the metallic plate that has no much damping on top (it will overheat the amplifier). I'm pretty sure that the metallic plate is causing a small change in sound, perhaps even a tiny increase in the resonance frequency. Perhaps someone from this forum that actually builds subs might take over this and provide a better answer.

However, the difficult part is how to pair a passive sub with a powerful amp and a pre-amp with DSP and still have some money left to pay the rent or bank. :)
 

audimus

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MDF can be a PITA to work with. It doesn't take glue or screws all that well. On the up side, it doesn't contain voids and is about as non resonant a material as one can commonly get...

Glue plus screws will do the trick for panels that are not expected to be removed. Ikea seems to have mastered this although not consistently by using a bolt through the hole at the edge which is filler material and weak and the “nut” at right angle through the wall that pulls the bolt down to put most of the stress on the walls rather than the filler material. And this is for panels that need to be disassembled. If no disassembly needed than you can use any glue including common wood glue, titebond or if you are brave enough and tidy enough in your work Gorilla glue. You can use drywall screws even or liquid nails to hold it while it is curing.

The main problem is actually ensuring it is airtight as required in a speaker cabinet. Gorilla glue expands and fills voids but anything else will likely require “caulking” to make it airtight.

And for any removable panels like front and back, getting it right without air leaks and not getting loose over time and vibrating is not easy.

Can be done but can’t do Ikea like stuff and leave it at that.
 

headshake

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Actually, I think that a passive sub might be better than an active sub, because if using the same box, the volume of air inside is higher on the passive sub (lacks the amplifier and PSU) and there're no wires and components inside to reverb and ding-ding and blink-blink. Also, speaker's coil will be cooler on a passive sub, due to the missing active components inside to generate heat.

Also, on an active sub most of subwoofer's vibrations are "hitting" the power amplifier inside and the metallic plate that has no much damping on top (it will overheat the amplifier). I'm pretty sure that the metallic plate is causing a small change in sound, perhaps even a tiny increase in the resonance frequency. Perhaps someone from this forum that actually builds subs might take over this and provide a better answer.

However, the difficult part is how to pair a passive sub with a powerful amp and a pre-amp with DSP and still have some money left to pay the rent or bank. :)
Or an active sub with an external amp/dsp.

All of that stuff inside is making a case for keeping it separate. Look at all of the things they have to do to lessen vibrations!

This is my dream diy sub contender: https://www.css-audio.com/online-store/SDX12-and-Sealed-Flat-Pack-Kit-p112666933

It does not need stuffing. It is kinda the opposite of the svs.

The SVS is my off the shelf contender.

Thanks for sharing the pics. It is nice to see what is going on inside.
 

ferrellms

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Or an active sub with an external amp/dsp.

All of that stuff inside is making a case for keeping it separate. Look at all of the things they have to do to lessen vibrations!

This is my dream diy sub contender: https://www.css-audio.com/online-store/SDX12-and-Sealed-Flat-Pack-Kit-p112666933

It does not need stuffing. It is kinda the opposite of the svs.

The SVS is my off the shelf contender.

Thanks for sharing the pics. It is nice to see what is going on inside.
Using a passive sub misses all the benefits of the DSP and amp that are designed specifically to work well together. You would essentially be second-guessing professional experts in subwoofer design. Conceivably, but not likely to be better.
 

Kal Rubinson

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KaiserSoze

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Just got few days ago my second SVS SB-1000 and I thought it would be nice to see what's inside the box and "how it works". This one is the black-ash (MDF with sort of melamine foil on the outside) and the "old one" is a black-gloss (MDF with veneer glossy on the outside).

The MDF cabinet has a thickness of 1.5 cm and the four inner walls are covered on the inside with 5 cm thick acoustic absorbent pollyfill. Quite a generous amount of damping material I'd say, although I've added one more piece myself between the electronic parts and the driver, just to be sure the reflections will get lowered inside even further (not quite a recommended modding and probably not necessary, but usually the rear side of the sub might need some sort or damping).



The SMPS power supply delivers 53.3 to the black-melamine subwoofer and 53.9V to the piano-black one, so the last one is more powerful. :) It doesn't seems to be a dual power supply as I can only see a red and black wire connected from PSU to the amp's PCB. There is also an additional dual +/-7V rail to power up the digital control parts (DSP).



The amplifier itself is a SVS proprietary SLEDGE STA-300D able to deliver 300 W of RMS power, with peaks up to 720 W.



The connection from the speaker to the amplifier seems to be bridged, so the two pairs of cables are paralleled on the driver side, then it's getting to separate PCB plugs. Cables are really thick, probably 1.5mm2 each one of them, so really good thing.


Between the back plate, also used as heatsink, and the PCB there's a piece of rubber/foam used to electrically isolate the PCB from the back plate, but also to damp the internal sound-waves.



On the amplifier's PCB I can identify:
- One TL064C quad operational amplifer made by ST that probably deals with the two stereo inputs from RCA and Speakers-Out.
- An AKM5358AET A/D converter, probably used to get the analogue inputs from the above opamp into the DSP.
- One STA309A multi-channel digital audio processor with DDX® (https://www.st.com/en/audio-ics/sta309a.html) that should take care of the Low-Pass Filter and all the necessary DSP corrections, based on the volume setting and frequency response. It should be programmed this way to correct imperfections of the subwoofer and provide a clean and proper bass response.



I can't see what type of Class-D power amplifiers are under the heatsink, but given the 36-pin I thought it might be TDA7498, but looking to https://www.st.com/en/audio-ics/class-d-audio-power-amplifiers.html#products I realized that there's no chip there able to be powered from 53V, so it should be some chip from https://www.st.com/en/audio-ics/digital-audio-power-amplifiers.html#2. Probably STA516BE seems to be able to deliver in mono-BTL configuration 400 W into a 3 Ω load with THD = 10% at VCC= 52 V, based on the datasheet.



SB-1000 and PB-1000 share the same speaker driver and my DMM shows a DC-resistance of 3.5 Ohms, so based on the above I'd say that the 300 W RMS power provided by the manufacturer is a real number and that's probably achieved with a THD definitely lower than 10% (probably more close to 1% than to 10%).

On the SMPS power supply board can be seen:
- One TL494L made by UTC
- Couple of MOSFET transistors (can't see the model, probably hard to find ones).



I subjectively think that the SMPS inside is the weak link here, it just doesn't looks to be able to sustain the power that the bridged chips could deliver when used in mono-BTL. Of course, the heatsink is not the best one too for a closed-sub that lacks real ventilation inside, but in the end power supply & amplifier & speaker/driver seem to blend pretty nice to the final specs of the entire subwoofer.

I find the sound as being fast and accurate, maybe not the best punch ever, but given that I'm speaking about a closed-sub that can almost shake an apartment or even a small house down to 24 Hz, then it's good enough for my small home too, especially in a dual configuration like I'm using. In compare with my Mackie MR10Smk3 the output power is higher, the sub-bass is more present and the kick & slam is bigger as well.

In my living-room setup, with a stereo set made of Yamaha A-S701 and CANTON GLE 496 with two woofers per speaker, I'm pretty comfortable with the final kick and slam with the low-pass filter on SB-1000 set to around 75-80 Hz and the volume to about 12 o'clock. When getting over 100 dB of SPL the kicking is really good and the chest is getting the right amount of "vibrations", well...at least when listening to some hits like "Cardi B, Bad Bunny & J Balvin - I Like It" or "Minelli - Mariola" or any contemporary hit that has a huge amount of sub-bass. :)

As a low-light, worth mentioning that after 90 dB SPL these subs are vibrating on the floor, so either the SVS shock absorber feet needs to get purchased, either some carpet needs to be placed under the default original feet (that's what I did).


Thanks! I'm interested in this sub because I prefer the more gradual rolloff of a sealed enclosure. And because the price is good of course. But with respect to sealed vs. ported (or PR), it would be interesting to know the Fs and Qts of the driver, as these are the two parameters that determine the suitability of the driver for sealed enclosure use or ported enclosure use. It would be especially interesting to know these parameter values for this driver since the same driver is used for both the sealed and ported version.
 

KaiserSoze

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Thanks for the write up.

I've often wondered if anybody with decent wood working tools could build better enclosures for entry level subs. After all, it is the enclosure that accounts for about half the price of a loudspeaker and "built like a brick shit house" isn't something that appears on spec sheets.

Based on your report, the cabinet for the SVS SB-1000 is 3/4" (nominal) MDF. Whether the front and back panels use material of the same thickness is anyone's guess, as this is sometimes where corners are cut. There doesn't appear to be any internal bracing which has some performance implications.

MDF can be a PITA to work with. It doesn't take glue or screws all that well. On the up side, it doesn't contain voids and is about as non resonant a material as one can commonly get...

MDF is horrible for screws. If it is a screw that you think you might remove and reinsert more than just a few times, it is better to use threaded inserts. To do threaded inserts you need to use a jig of some sort both for drilling the hole and for screwing in the insert. A drill press can be useful in particular circumstances. With gluing the mating surface areas need to be bigger than with most any wood for two reasons. The glue doesn't soak in very far, and the MDF will too easily pull apart behind the glue. I've used it but my sense is that from the standpoint of intrinsic damping it is only slightly better than other common materials such as plywood. The knuckle test indicates that the difference is not strong, and you step over to where you find the composite material used for outdoor decking, the difference is dramatic. The material used for outdoor decking is much more pliable and at the same time seems to be be more dense. Very heavy but bends a lot, maybe too much to be useful for cabinet construction, but not a lot of reinforcement should be needed to stiffen up as needed.

There are a number of good subwoofer kits, some with knock-down cabinets and a lot more without. But I've explored this option repeatedly by doing a cost comparison, and the conclusion is that the rationale for building a subwoofer has to be something besides saving money. By the time you've bought the amp and all the other stuff you end up buying, glue, wood screws, maybe clamps if you don't already have them, you'll have spent considerably more than what the SB-1000 costs. For hobbyists the motivation is not cost savings. I'm somewhere in the middle, but ultimately I can't see doing all the work needed to end up with a nice subwoofer unless it is going to save me money compared to what I would spend on a subwoofer like this one.
 
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