Newb to diy needing a sanity check on subwoofer plans

[marticus]

Hi guys,

I'm considering attempting a subwoofer build to get me started into DIY speakers, I've done a little research and made an initial attempt at using winisd to model some results, but I would like to get some confirmation that I haven't missed something obvious before I start spending money.

So the driver I'm looking at is SB Acoustics SB34SWPL76-4

And the amplifier is monacor Sam 300d.

So I input the speaker parameters into winisd, and after some playing with the volume and tuning frequency it looks like I can get flat response down to 19hz..

So to the questions.. Aside from putting all the perameters into winisd, is there anything else I need to consider?

I read somewhere that the tuning frequency shouldn't be lower that the fs of the driver, is that also correct? Does there need to be some other allowance there?

regarding ports.. Can I just take the port recommendation out of winisd and use them as is? Or should I be considering something else there?

OK last one for now I promise! I know that the volume of the box has to account for all the bracing, driver, and amplifier. But I'm wondering if there's anything else to consider regarding the internal bracing. How close it is to the driver or ports for example, can it interfere with the response of the sub?

Sorry for all the noob questions, thanks in advance for any help!

 

[ryanosaur]

There is a lot to unpack here, and some of it I cannot help with.
SB Acoustics does make some good drivers. I am not certain about the Subwoofer, however.
It is not uncommon in DIY Subwoofers to get away from Plate Amps. I will be doing this with my designs currently in the works. Use something like an XLR or Speakon connector in the cabinet, then an external Amp like the Behringer NX3000 or Crown XLS1502 which contain DSP options to program controls for the Subwoofer. Amps like these can power multiple subs depending on how you wire them. Well worth looking into, IMO.

So to the questions.. Aside from putting all the perameters into winisd, is there anything else I need to consider?

Yes and no. There are always things to consider... but without knowing more about your design and goal, I can't predict what you may have missed, if anything at all.

I read somewhere that the tuning frequency shouldn't be lower that the fs of the driver, is that also correct? Does there need to be some other allowance there?

Some drivers can be pushed below their Fs. Much of that depends on their Power Handling, Motor Strength, and Suspension. For example, I've seen models of the Eminence NSW6021 pushed to the low teens... Not to say that is a practical option, but theoretically doable.
I am not familiar with WinISD, but BassBox Pro will show you predicted excursion and where the driver will tap out ant different power levels.
Using DSP to program a high pass filter is common to help protect the driver down low. (Likewise, you can also program a voltage limiter in DSP to help prevent exceeding safe power handling capabilities.)

regarding ports.. Can I just take the port recommendation out of winisd and use them as is? Or should I be considering something else there?

Without knowing what you are being told in the model, all I can suggest is to look at what the particle velocity may be and whether that is going to create audible noise at lower frequencies and high output. Again, my experience with BassBox is that the model will include that information and give you a warning about possible port issues.
Beyond that, make certain your ports have room to breathe... not too close to the cabinet wall where they open inside the cabinet, and not blocked by any packing material.

OK last one for now I promise! I know that the volume of the box has to account for all the bracing, driver, and amplifier. But I'm wondering if there's anything else to consider regarding the internal bracing. How close it is to the driver or ports for example, can it interfere with the response of the sub?

Bracing can be challenging... and I've looked at some intriguing ideas online. Worth researching more deeply. In short, it is recommended to brace every 10-12". While I wouldn't put a brace right up against the driver, they can definitely be near the driver. Look at flatpacks on GSG, PE, other sites and see how they look inside. Likewise checkout some build videos, especially ones using flatpacks that you can see designs of. I found this helpful to help me wrap my head around it.

Side notes:
Double up your front baffle to be 1.5" thick, with 3/4" sides.
Make certain the box itself is as airtight as possible.
Some people recommend tight bond wood glue, other like construction adhesive like Loctite PL3. (I will be using the latter.)
MDF or Baltic Birch for construction? Baltic Birch is lighter by ~1 pound per square foot, but is also more expensive. It can be easier to work with, and does not create the dust that MDF will.
Wear a respirator when cutting, routing, sanding, etc.
Dowels can be used well for bracing as opposed to window bracing and such... as I said above, you should research bracing options and plan your strategy.

Cheers!

 

[Verdinut]

I read somewhere that the tuning frequency shouldn't be lower that the fs of the driver, is that also correct? Does there need to be some other allowance there?

regarding ports.. Can I just take the port recommendation out of winisd and use them as is? Or should I be considering something else there?

The box tuning frequency of a ported box can be lower than the Fs of the driver. But a speaker should not be driven at frequencies below the box tuning frequency, as at such LF, there is no more loading by the box that prevents the driver from exceeding its Xmax.

As for the port recommendation by Winisd, it's possible that the suggested dimensions are not spot on the projected tuning frequency. That's why it is useful to have an equipment such as the Dayton DATS V3:

Home

Dayton Audio DATS V3 Computer Based Speaker & Audio Component Test SystemDayton Audio DATS V3 Computer Based Speaker & Audio Component Test SystemThe Perfect Companion for Audio ProfessionalsWhen designing the DATS V3 measurement device, Dayton Audio took everything customers love about the DATS...

www.parts-express.com

 

[marticus]

There is a lot to unpack here, and some of it I cannot help with.
SB Acoustics does make some good drivers. I am not certain about the Subwoofer, however.
It is not uncommon in DIY Subwoofers to get away from Plate Amps. I will be doing this with my designs currently in the works. Use something like an XLR or Speakon connector in the cabinet, then an external Amp like the Behringer NX3000 or Crown XLS1502 which contain DSP options to program controls for the Subwoofer. Amps like these can power multiple subs depending on how you wire them. Well worth looking into, IMO.


Yes and no. There are always things to consider... but without knowing more about your design and goal, I can't predict what you may have missed, if anything at all.

Some drivers can be pushed below their Fs. Much of that depends on their Power Handling, Motor Strength, and Suspension. For example, I've seen models of the Eminence NSW6021 pushed to the low teens... Not to say that is a practical option, but theoretically doable.
I am not familiar with WinISD, but BassBox Pro will show you predicted excursion and where the driver will tap out ant different power levels.
Using DSP to program a high pass filter is common to help protect the driver down low. (Likewise, you can also program a voltage limiter in DSP to help prevent exceeding safe power handling capabilities.)

Without knowing what you are being told in the model, all I can suggest is to look at what the particle velocity may be and whether that is going to create audible noise at lower frequencies and high output. Again, my experience with BassBox is that the model will include that information and give you a warning about possible port issues.
Beyond that, make certain your ports have room to breathe... not too close to the cabinet wall where they open inside the cabinet, and not blocked by any packing material.

Bracing can be challenging... and I've looked at some intriguing ideas online. Worth researching more deeply. In short, it is recommended to brace every 10-12". While I wouldn't put a brace right up against the driver, they can definitely be near the driver. Look at flatpacks on GSG, PE, other sites and see how they look inside. Likewise checkout some build videos, especially ones using flatpacks that you can see designs of. I found this helpful to help me wrap my head around it.

Side notes:
Double up your front baffle to be 1.5" thick, with 3/4" sides.
Make certain the box itself is as airtight as possible.
Some people recommend tight bond wood glue, other like construction adhesive like Loctite PL3. (I will be using the latter.)
MDF or Baltic Birch for construction? Baltic Birch is lighter by ~1 pound per square foot, but is also more expensive. It can be easier to work with, and does not create the dust that MDF will.
Wear a respirator when cutting, routing, sanding, etc.
Dowels can be used well for bracing as opposed to window bracing and such... as I said above, you should research bracing options and plan your strategy.

Cheers!

Thanks for taking the time to write such a comprehensive response I appreciate it.

I guess i should have started off with my goals here right. so my space is about 5-6000 cubic feet, and from my understanding I will need a lot of subwoofer to fill that, unfortunately i don't have the budget or space (WAF) for something huge or small/powerful.

i'm based in Poland so a lot of those decent budget options that are available in north America are overpriced here. My hope is that I can build something with a better performance/$ ratio than commercial offerings (i understand this is problematic at a budget pricepoint). The driver / Amplifier combination should work out about 300 euro.

I'm looking at 12" drivers as what i've seen leads me to suspect that is a good middle ground between size and performance, and i'm hoping to keep the box less than 80 liters 60 preferable, assuming i've done my math right.

In terms of performace i'm not expecting anything crazy but i'm hoping to hit 20hz or less with reasonable SPL. and if my first attempt goes OK I will build a second, i'm hoping two will do the trick.

Good tip about the Amplifier, assuming I'm planning on running two of these eventually anyway I will look into something that could drive them. are car amps of any use here? i see lots for sale on the second hand market and have often wondered if they would be useable for a home theater sub..

I think I will look into Bassbox Pro, and see if it gives me similar results to winISD, that should at least confirm that i'm on the right track. And maybe I will post up some more detailed results later.

Thanks again!

 

[marticus]

The box tuning frequency of a ported box can be lower than the Fs of the driver. But a speaker should not be driven at frequencies below the box tuning frequency, as at such LF, there is no more loading by the box that prevents the driver from exceeding its Xmax.

As for the port recommendation by Winisd, it's possible that the suggested dimensions are not spot on the projected tuning frequency. That's why it is useful to have an equipment such as the Dayton DATS V3:

Home

Dayton Audio DATS V3 Computer Based Speaker & Audio Component Test SystemDayton Audio DATS V3 Computer Based Speaker & Audio Component Test SystemThe Perfect Companion for Audio ProfessionalsWhen designing the DATS V3 measurement device, Dayton Audio took everything customers love about the DATS...

www.parts-express.com

Thanks for the reply!

So I should implement a high pass filter to ensure the sub isn't going below the tuning frequency i guess?

I will look into the Dayton Dats, that looks like a usefull bit of kit. i'm also going to check into bassbox pro as a comparison to winISD to see how they match.

thanks again.

 

[Verdinut]

Thanks for the reply!

So I should implement a high pass filter to ensure the sub isn't going below the tuning frequency i guess?

I will look into the Dayton Dats, that looks like a usefull bit of kit. i'm also going to check into bassbox pro as a comparison to winISD to see how they match.

thanks again.

With regard to the high pass filter, a need depends on what type of source program you intend to drive the sub with. I haven't checked with a speaker box software, but I guess that WinISD would suggest a box tuning frequency at about 25 Hz or slightly above. If you only listen to music, there isn't much signal below 30 Hz unless you like to listen to discs with massive bass, such as those Drum & Bass recordings, action movie soundtracks, electronic keyboard or pipe organ music that can dig down to 16 Hz.

 

[marticus]

With regard to the high pass filter, a need depends on what type of source program you intend to drive the sub with. I haven't checked with a speaker box software, but I guess that WinISD would suggest a box tuning frequency at about 25 Hz or slightly above. If you only listen to music, there isn't much signal below 30 Hz unless you like to listen to discs with massive bass, such as those Drum & Bass recordings, action movie soundtracks, electronic keyboard or pipe organ music that can dig down to 16 Hz.

Thanks for that, my primary concern is movies, I know I won't get to 16hz with my budget / size requirements, but im hoping to get below 20, my current sub is rolling of by 25hz from what I've seen.

I need to check some more into how best I can deal with the filter also I guess dsp in the amp or external unit.

Thanks again!

 

[Verdinut]

Thanks for that, my primary concern is movies, I know I won't get to 16hz with my budget / size requirements, but im hoping to get below 20, my current sub is rolling of by 25hz from what I've seen.

I need to check some more into how best I can deal with the filter also I guess dsp in the amp or external unit.

Thanks again!

If you use a high pass filter, you won't definitely get 20 Hz. Also, even with no HP filter, I strongly doubt that you would get a useful output below 25 Hz, because that SB Acoustics driver has a low Qts. You said that WinISD indicated indicated that you could get a flat response to 19 Hz. I am going to verify with BassBox6 Pro and come back on this.

 

[marticus]

If you use a high pass filter, you won't definitely get 20 Hz. Also, even with no HP filter, I strongly doubt that you would get a useful output below 25 Hz, because that SB Acoustics driver has a low Qts. You said that WinISD indicated indicated that you could get a flat response to 19 Hz. I am going to verify with BassBox6 Pro and come back on this.

That would be awesome thanks!

 

[Verdinut]

That would be awesome thanks!

I verified with the BassBox and also the recommendation of the Madisound Speaker Store.

The best alignment for an F3 of 21 Hz would be a box with a net volume of 2.5 cubic feet. BassBox confirms that suggestion.

SB Acoustics SB34SWPL-76-4 12" Subwoofer

SB Acoustics SB34SWPL-76-4 12" Subwoofer

www.madisoundspeakerstore.com

Go down the page and you will see full details with the duct pipe length. That design is tuned at 23 Hz for the smoothest LF performance.

 

[marticus]

I verified with the BassBox and also the recommendation of the Madisound Speaker Store.

The best alignment for an F3 of 21 Hz would be a box with a net 2.5 cubic feet. BassBox confirms that suggestion.

SB Acoustics SB34SWPL-76-4 12" Subwoofer

SB Acoustics SB34SWPL-76-4 12" Subwoofer

www.madisoundspeakerstore.com

Go down the page and you will see full details with the duct pipe length.

that's great to know thanks for taking the time to do that, so it looks like winISD is off, or more likely i messed something up when inputting the speaker parameters. you've saved me from unrealistic expectations!

with that being said i doubt i would be wholly dissatisfied with that kind of performance, though it's hard to quantify from a single f3 figure.

I'll have another look around and see what else is available here, i think the next step up in terms of cost are some of the dayton audio drivers, but i wanted to avoid relying on products imported from the US in case they become more expensive / difficault to source in the future.

Again, big thanks for that, i'm really impressed with this forum so far,you guys really go the extra mile for noobs like me

 

[Pogre]

I can't offer much, but I'm always up for a sub build thread!

I do agree with getting away from a plate amp for a couple of reasons. It simplifies the build a little bit, and if you get a big enough amp you can power multiple subs with it. That's where the diy savings really start kicking in.

 

[Pogre]

Again, big thanks for that, i'm really impressed with this forum so far,you guys really go the extra mile for noobs like me

You know, it really helps when you check your preconceptions at the door and are open to advice and suggestions. You're in the right place with the right attitude and asking good questions. Welcome to the funny farm!

 

[marticus]

I can't offer much, but I'm always up for a sub build thread!

I do agree with getting away from away plate amp for a couple of reasons. It simplifies the build a little bit, and if you get a big enough amp you can power multiple subs with it. That's where the diy savings really start kicking in.

Yeah that makes sense, I'm looking at a crown xls1002 someone is selling not far from me right now for about $200 lol

 

[marticus]

You know, it really helps when you check your preconceptions at the door and are open to advice and suggestions. You're in the right place with the right attitude and asking good questions. Welcome to the funny farm!

Feels like home already!

 

[TLS Guy]

I have done a number of models for you, I will attach the best one.

Unfortunately I do not recommend that driver for a domestic sub. It models as a classic car sub and not a domestic one. It has the classic response to work with the "cab gain" of cars. It is also designed to go in a small sealed enclosure.

It does model in a ported box. Unusually it models best as an extended bass alignment, which I do not as a rule favor. The reason I think this occurs is that it is a low Qt. driver.

So it models as a 2.29 cu.ft box with an F3 just below 27 Hz. The problem is that it requires a relatively long vent to get the vent air velocity down to acceptable levels.
Even then you may have trouble winding it inside the box. It would be more suitable to be tuned with an ABR. (Passive radiator).

My advice since you have not built the cabinet, is to select a driver more suitable for domestic AV duty.

Driver selection is one of the most difficult aspects for the DIY builder to get the hang of. However, as I have said here many times, all good designs start with appropriate driver selections.

 

[marticus]

I verified with the BassBox and also the recommendation of the Madisound Speaker Store.

The best alignment for an F3 of 21 Hz would be a box with a net volume of 2.5 cubic feet. BassBox confirms that suggestion.

SB Acoustics SB34SWPL-76-4 12" Subwoofer

SB Acoustics SB34SWPL-76-4 12" Subwoofer

www.madisoundspeakerstore.com

Go down the page and you will see full details with the duct pipe length. That design is tuned at 23 Hz for the smoothest LF performance.

Hi again, just out of interest i figured i would check my results in winisd, so this time i imported the driver from the driver database instead of trying to enter everything manually, and i generated an EBS model as suggested on madisound.

This is what it generated for me, i'm wondering how this fits into you findings, do you have any experience with EBS enclosures?

I suspect the biggest difficaulty here is the port length..

power looks ok as far as my understanding of such things goes..

if I bring the box size down to 80l and up the tuning frequency to 18hz i get:

What's difficault for me is knowing how far you can push these numbers, i can see with the last 80l config cone excursion is maxing about 15hz?

of course i'm not knowlegable enough to know what other hard limits i need to account for. i'm not even knowlegable enough to fully understand the difference between a 'standard' vented enclosure and an extended base shelf.

From my little research an EBS is when you target below the fs of the driver and increase the size to compensate? but then when does an EBS stop being an EBS? when the box is too small or when you cross the fs ..

its funny because when I started looking into this the implication was that you stick the drivers into winisd, and whatever box size pops out you build it and everythings golden. then of course in reality you start digging and before you know it you've dug all the way to Australia and you have a spider in your shoe.

 

[marticus]

I have done a number of models for you, I will attach the best one.

Unfortunately I do not recommend that driver for a domestic sub. It models as a classic car sub and not a domestic one. It has the classic response to work with the "cab gain" of cars. It is also designed to go in a small sealed enclosure.

It does model in a ported box. Unusually it models best as an extended bass alignment, which I do not as a rule favor. The reason I think this occurs is that it is a low Qt. driver.

So it models as a 2.29 cu.ft box with an F3 just below 27 Hz. The problem is that it requires a relatively long vent to get the vent air velocity down to acceptable levels.
Even then you may have trouble winding it inside the box. It would be more suitable to be tuned with an ABR. (Passive radiator).

My advice since you have not built the cabinet, is to select a driver more suitable for domestic AV duty.

Driver selection is one of the most difficult aspects for the DIY builder to get the hang of. However, as I have said here many times, all good designs start with appropriate driver selections.

WOW thanks! again you guys come through! I was playing more with winISD at the same time you have been doing these, and I posted my findings above.

I will follow your advise and keep looking, but at the very least this was a good excersise for me to get used to the software and better understand what it's limitations are, (ie just because it shows a reasonable response graph, it doesn't mean you will get a good sub out of it)

thank you so much for the effort, I will spend some time looking over your models to try and improve my understanding!

 

[lovinthehd]

One note as to dsp in a Crown XLS amp, it is very limited, while it's suited to just a crossover between sub/speaker, does not have the more extensive dsp of the Behringer NX3000 to place a high pass filter for protection under tuning point for example. Many of us using XLS amps (I have 5) use external dsp on diy subs such as from miniDSP.com (2x4 models particularly).

 

[marticus]

One note as to dsp in a Crown XLS amp, it is very limited, while it's suited to just a crossover between sub/speaker, does not have the more extensive dsp of the Behringer NX3000 to place a high pass filter for protection under tuning point for example. Many of us using XLS amps (I have 5) use external dsp on diy subs such as from miniDSP.com (2x4 models particularly).

Great info thanks, I was also looking at the Behringer NX1000 which seems to also have the same high/low pass filtering.

A minidsp 2x4 HD was on the list already for if i get a second sub, so I will plan to get that also when the time comes.
From my understanding the HD model is preferable for subs?