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15-18" Powered Subwoofer Pair Build

gnarly

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Thank you. It’s a beast! It must be fun to wire it :)

For a 2-way active stereo crossover do you think it offers more filter flexibility than a miniDSP?
Yes, it's fun to draw up I/O and processing schematics given its open architecture design.

For a 2-way, and nothing more, no subs etc, I'm not sure it would make sense compared to say a minidsp 2x4HD.

That said however, I learn so much about processing ..xovers, EQs, etc...from just running electrical only transfer functions of simple designs that pop into mind.
Heck, it even has it's own dual channel FFT you can place anywhere in the schematic. I love the things!!
 

jhaider

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Well, here's the thing...."actually necessary to accomplish a goal" is "your goal", isn't it?

No. I don’t personally give a damn about “cinema reference levels.” But that’s generally the stated goal of AVS subwoofer excess. So it was worth exploring what that actually means by going to the source material (Atmos et al. specifications)

So I still see my sub amp, a PL380 with 2500W per ch @ 4ohm per channel clip at times, driving two of the BMS 18"s per channel.

I wonder what’s amiss. Maybe some cancellation in your setup? How did you set levels, delays, and EQ for each group of subs?

Running two subs on one processing channel kneecaps your optimization possibilities to some degree, so it’s possible you’d be able to get better results with less power, more channels, and improved optimization.

For reference, our main system sub controller-amp (Crown DCI4|1250n) has never reported a clipping event. Each sub is on a dedicated channel, and gains/delays/EQ are individually set by Dirac Live Bass Control aside from individual Linkwitz transforms. Subs are also wired as easy loads, nothing below 4 Ohms nominal, and most double that. That’s what should result from stupid cone area (here, an 18, 2 15s, and 2 12s, all in closed boxes) and stupid power. The 20A (120V circuit) breaker has never tripped either.

For the sake of fidelity, there's more to it than just how low in frequency a sub reaches. ime/imo. A benefit of a sub reaching lower than musical content is that it flattens phase to a lower frequency as well, which of course pushes group delay / phase rotation lower. 31.5Hz changes relative timing in a positive way, with a sub that reaches linearly below 31.5.

I’m not sure what any of that means, tbh. My read of Geddes and Toole is the steady state FR is what matters in the modal region and below. I’ve not heard anything in my listening to contradict that.

Here's mag and phase from my dual opposed 18" reflex build. Taken outdoors ground plane... What would you suggest I do to set them up better ???

I have no idea, beyond as mentioned above giving yourself an extra degree of freedom by individually processing and amplifying each sub.

Thing is, the data provided above is useless to answer the question posed at the end of it, because individual parts performance is completely out of the scope of system optimization. Tell us more about how you set the subs up in the room and maybe you can get useful diagnoses here.
 

gnarly

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I wonder what’s amiss. Maybe some cancellation in your setup? How did you set levels, delays, and EQ for each group of subs?

Nothing is amiss. I didn't describe the subs being powered by the PL380 well enough.
Two dual bms 18n862 ported subs, for stereo. One sub per channel on the amp. (I'm not into the multi-sub approach or home theater.)
Simple case of subs being able to take more power than amp can deliver, and being driven there.
Running two subs on one processing channel kneecaps your optimization possibilities to some degree, so it’s possible you’d be able to get better results with less power, more channels, and improved optimization.

Like said, not into multi-sub...which sounds muddy and rounded over to me compared to a simple stereo setup (actually, mono can often sound best of all i think)
So levels, delays and EQ for the sub are just a function of dialing in a full-range speaker. I do this as quasi-anechoically as possible, outdoors.
Processing is via Q-Sys, utilizing FIR for linear phase. Currently running 4-way synergies and a sub, per stereo side.
Flat frequency response, and flat phase are an easy given to achieve. Most tuning works comes from trying to optimize polars.
My most critical listening is done outdoors. I live with the results indoors without much further EQ/processing other than suppressing room modes.
I try too many proto-type experiments, build too many speakers, to get serious with trying to optimize any one of them to my main room.

I say all the above to impart my goal, which is the cleanest, highest linear (both mag and phase) SPL (both average and peak), with as low a bass extension as possible (with <3dB EQ boost).
It's my ticket to what i feel is the most life-like fidelity I've heard..
For reference, our main system sub controller-amp (Crown DCI4|1250n) has never reported a clipping event. Each sub is on a dedicated channel, and gains/delays/EQ are individually set by Dirac Live Bass Control aside from individual Linkwitz transforms. Subs are also wired as easy loads, nothing below 4 Ohms nominal, and most double that. That’s what should result from stupid cone area (here, an 18, 2 15s, and 2 12s, all in closed boxes) and stupid power. The 20A (120V circuit) breaker has never tripped either.
Nice amp. I'm such a fan of prosound install amps (other than their typically loud fans, dammit).
Do you use a BLU processor and send audio over ethernet? I'm guessing not, since you have Dirac in the loop.
Sounds like you're into the multi-sub approach big time. Cool.

I use QSC's CXD-Q's network amps, and various other QSC amps that take signal from ethernet I/O frames.
They all of course have amp monitoring similar to the Crown DCI's. I see Crown has released a Q-Sys plugin, to allow monitoring the DCI's over Q-Sys.
Gotta love amp monitoring for being able to really know how things works, huh?
I’m not sure what any of that means, tbh. My read of Geddes and Toole is the steady state FR is what matters in the modal region and below. I’ve not heard anything in my listening to contradict that.

What i meant to be imparting, is that having linear phase (shall we just say flat phase) extend as low in frequency as possible, holds timing advantages that can be heard on certain well recorded material. Bass notes and transients just seem to be more in time with the rest of the spectrum.

As we know, phase starts lagging where ever the low end rolls off. And the more the roll-off, the more phase lags, the more the group delay, yada.
I think the biggest reason folks often prefer sealed subs to ported, is sealed have a second order roll-off, vs ported having a steeper fourth order roll-off.
(I'm sure you know all that...wrote it for others following along...)

Anyway, even if there is no musical content below 30Hz, and the sub is fully capable of 30Hz, whatever phase lag/group delay there is at 30Hz will be reduced/flattened by a sub that maintains flat magnitude response below 30Hz.
All we really want for super bass is a sub flat to DC Lol.
Back to IPAL as closest alterative today I guess. Check out this Dave Rat vid...get's downright funny as he holds on to the cone past the 6:00 mark
 

gnarly

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Thing is, the data provided above is useless to answer the question posed at the end of it, because individual parts performance is completely out of the scope of system optimization. Tell us more about how you set the subs up in the room and maybe you can get useful diagnoses here.
Sorry for further post... I'll back off from long comments from here on..

As a DIY speaker builder striving for the best quasi-anechoic response, I've found the performance of individual parts, be they driver sections in a speaker or in separate boxes like subs and mains, is crucial.

I completely tune/process each driver section independently of the other sections for flat mag and phase (independent other than prechosen xover points).
And know for certain they will tie together with flat mag and phase, with no more effort than easily setting levels and delays.

Here's a example for of the 4-way synergy i mentioned.
Each sections' acoustic response is shown.
syn10 sections proc.JPG



Here's the summation. Sorry I don't have sub included, but it's easy to picture it ties in just like the syn sections..
syn10 sections summed proc.JPG
 

jhaider

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@gnarly thanks for your replies. At a high level I think most of our stated disagreements stem from different listening environments - outdoors vs. acoustically small room. That has massive implications as to headroom requirements in the bass, as well as optimization approaches.

Also, I was directionally correct but certainly too extreme in my assertions regarding parts quality above.

A few other brief comments:

Like said, not into multi-sub...which sounds muddy and rounded over to me compared to a simple stereo setup (actually, mono can often sound best of all i think)

To clarify, multi-sub per Geddes/Harman/DLBC is mono. It also only applies in acoustically small rooms, because the modal issues it works to address are small room issues.

Currently running 4-way synergies and a sub, per stereo side.

Cool! Do you have a thread on those?

Nice amp. I'm such a fan of prosound install amps (other than their typically loud fans, dammit).

Yep. They need to be remote from the room. But the features and power are excellent.

Do you use a BLU processor and send audio over ethernet? I'm guessing not, since you have Dirac in the loop.

No, analog in to the rack DCI-n amps. I do have a couple BSS processors on hand. When my mains amp was in the same room I used BSS to load the tuning for the front speakers. I only keep them because if my Monoprice HTP-1 dies I’d consider an AVP with Dante and a BLU-DA to convert to Blu-Link.

All of this is far afield of the OP. Apologies, but hope others nonetheless benefitted from the issues teased out.
 

gnarly

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@gnarly thanks for your replies. At a high level I think most of our stated disagreements stem from different listening environments - outdoors vs. acoustically small room. That has massive implications as to headroom requirements in the bass, as well as optimization approaches.
Glad we found common ground, thanks for your comments and staying with the discussion.
Totally agree about the different listening environments shaping our comments, and was why I wanted to present mine, to help reach where we are now at.
Cool! Do you have a thread on those?
Here's a thread from DIY https://www.diyaudio.com/community/threads/syn-10.383607/
It's a pretty short one...I've littered DIY with so many synergy versions, even they are probably tired of them Lol

Oh, i saw i forgot to provide the Dave Rat link i mentioned, about IPAL https://www.diyaudio.com/community/threads/syn-10.383607/
Get's pretty funny watching him hold onto the cone, as it marches down to 1Hz...
 

Ricku

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I would look for options available locally, and testes at data-bass.com:

- BMS18N862: https://data-bass.com/#/systems/5c48e01911126b0004ca12ec?_k=qcpf1c
- B&C 21SW152-4: https://data-bass.com/#/systems/5b11dab8a201f10004e39d72?_k=ewio3y
- B&C 21DS115-4: https://data-bass.com/#/systems/5d02b177d6b2560004ebe49e?_k=jdn66m
- Eminence NSW6021-6: https://data-bass.com/#/systems/5d0beab0b3ca0a0004fc82ae?_k=rbou86 (although excellent, this should be too pricier, around 11150$)
- Lavoce SAN214.50: https://data-bass.com/#/systems/5d03f339d349e90004d8fcd5?_k=9rfu7y

I would select based on availability and price, 2 of the above, even sealed, would run circles around any comercial alternative.
Moreover, no need to speculate, just look at data-bass.com analysis and compare.

As the OP is from NZ, it would probably be very expensive to ship large subwoofers (moreover with the added VAT).

By going DIY, you should be able to get one of the above drivers for a good price (500-800$, excluding the Eminence).
So 1600$ in drivers, 1400$ for plate amps (could be even cheaper if you select an external amp with DSP), and then the rest on woodworking, depending on how professional you would like them.

I found this thread amazing, you can check how professional a DIY subwoofer can be made:
Sorry... here I am doing research in to building my own subwoofers and I see someone linked through to the subwoofers I built for my Dad! Glad to see other people are appreciating them.
 

morpheusX

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Sorry... here I am doing research in to building my own subwoofers and I see someone linked through to the subwoofers I built for my Dad! Glad to see other people are appreciating them.
Congratulations, i really found your thread amazing, not only for the subwoofer work, but also for the care you seem to have for your dad !!!
 

Adi777

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Is it worth choosing 24 inches or 21 is enough?
Wooofer 24 inch will have any advantage over 21?
 

azzy_mazzy

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Is it worth choosing 24 inches or 21 is enough?
depends on what you are trying to achieve but for most normal people even few 12" is enough. personally i would get more subs instead of one giant one. a 24" requires a big box even when sealed and might not get you much over multiple smaller drivers, for example here is the SI HS-24 in 295 liters box (10.4 ft^3) vs 2 BMS 18N862 in 179 liters box (6.3ft^3) both getting full rated power and under XMAX above 12Hz
1656096983668.png

the SI loses badly above 30Hz (where most content will be) but "only" have 1.5dB advantage at 20Hz and 2dB at 10Hz (now of course the SI can take far more power than rated as seen on data bass).
now i doubt most people can throw around multiple 180 liters boxes around their room let alone 295 liters box which would hinder multi sub and getting actually good bass.

so my real advice is to get 2-4 12"-18" put them in a sealed boxes and with EQ and delay it will sound better than any one giant subwoofer.
you won't impress AVS forum as much though.


Edit: one thing i forgot to add is smaller drivers can be crossed over higher without as much issues, i even tried 120hz when i had subwoofers at my desktop setup and it was great.
 
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Ciobi69

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I would love to find a good project with the bms18n862 my friends that used it advised me that is a very good driver here available in Europe, my main need would be purely HT and secondary music , i think the tuning should be around 27 Hz if i am not wrong,i don't understand more than that,but its not easy to design a good ported box,or at least i don't have the experience, i would love to build a pair of those and be satisfied forever
 

Ra1zel

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but its not easy to design a good ported box,or at least i don't have the experience, i would love to build a pair of those and be satisfied forever
That's why you shouldn't and instead build sealed and use EQ, I've heard 4x 18n862 sealed subs in 42m² room and it can simulate an earthquake if you want to, and distortion is the lowest I have seen on low frequencies. 4x 18 inch woofers have area comparable to single 36 inch woofer...
 

Ciobi69

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That's why you shouldn't and instead build sealed and use EQ, I've heard 4x 18n862 sealed subs in 42m² room and it can simulate an earthquake if you want to, and distortion is the lowest I have seen on low frequencies. 4x 18 inch woofers have area comparable to single 36 inch woofer...
I am lucky to know a friend that is going do design a ported box for me , he is good at it, going to build two of them, plenty for me!
 

ROOSKIE

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I have March Sointuva speakers on the way.

I am considering building a couple of powered 15"-18" driver subwoofers to fill in the low frequencies and take the load off the Sointuva's.

• My room is about: 13 ft * 15 ft * 11 ft (l*w*h)
• For both music and movies.
• I don't mind waiting for stock, as it will be a while before I purchase parts anyway.
• The aim is to build something with excellent neutrality/linearity and very low THD.
• Thinking of building the boxes with HDF or baltic birch, with a nice veneer on the exterior.

I seek advice on:

• What drivers to use: I am happy to spend a lot on drivers.

• What corresponding plate amps to use: ditto.

• Ported or sealed? I understand ported provides higher SPL output but is more difficult to design?

• How to design the boxes. eg what thickness of HDF, how to brace boxes, how to integrate ports.

My rationale for DIY subs is: I think they are probably easier to design than any other audio component; I want to spend a bit less than a commercial sub; and I have some DIY experience in building my stereo amplifier.

If in the end I don't DIY I think I would instead invest in a couple of Genelec or Perlisten or Arendal.

Hi OP,
lots of great discussion due to your post.

Here is my take. Just my personal take, I am not a famous dude.

1. your room is actually small and that needs to be addressed here. One of my previous spaces was that size exactly and in that space I used used a pair of DIY 8" Ported box woofers and that was almost enough. Two 10's or 12's that dug a bit deeper would have been everything required. I would never ever have used (2) 15's or 18's in there

2. All other things being generally equal a ported design will have much lower distortion around the port tuning region due to the port providing as much 80+% of the output and the driver barely moving. That said if the port is not well designed the port can add distortion and noise and even change the box tuning if air can not move properly. *

*do not worry about pipe resonances. You have March Sointuva's. I feel this was lost somewhere. You will be crossing at 40-60hrz(80 max) especially since your room is smaller. If you pick 50hrz and use a typical 24db slope you are 24db down by around 100hrz and 48db by around 200hrz. If you get pipe resonances I will be shocked.

3. All things being equal a sealed box will require substantially more power for the same output, depending on the situation and the required boost it could 3-12db of boost which is a tremendous power differential. You will also be using much larger excursions with a sealed box. There is zero reason to anticipate a driver performing well at or near rated xmax. Find a test on the driver (try Audio Express / Voice Coil Mag). Another issue from high xmax is doppler distortion. Linkwitz did doppler testing on his woofers and found severe issues at 50% or so of xmax and beyond on excellent drivers. YMMV

4. The main benefit of sealed is box simplicity and size. Easier to build and physically less massive. I big ported 18 might be HUGE. That may be a factor visually. I actually want big beast boxes because that is how my living room is. Audio central. Some won't appreciate that.

5. If going ported and you have DSP use a HP below the port tuning. If you tuned to 22hrz, HP it somewhere around say 15-18hrz to ensure a random ultra low moment doesn't create an issue.

6. If you want to go and spend a little bigger. Passive radiators.
The best of both worlds IMHO, ported performance and lower power requirements with zero port noise and just like with the ported design due to low x-over you won't get radiator resonances. (like port pipe resonances)
You need twice+ the excursion(actually twice the air movement) in the radiators so keep that in mind.
That could look like any number of combinations, often two radiators of the same size and excursion with one active woofer. You will also commonly see something like a single 15" radiator with a 10 or 12" active woofer.

7. I was in the market for two more subs and all set to build two 15" like #6. I had many of the parts here already. I also have many other DIY projects in Audio and beyond so keep that in mind. I was not going to miss out on a DIY experience here. Then the Klipsch SPL150's when on sale for under $600 each which is less than the parts cost for my DIY builds.
$1150 for (2) & I went for them. Ugly though but I kind of like that. Online reports suggest clean high output and the boxes are only 65lbs so I can move them alone. They don't use radiators so hopefully the port doesn't chuff down low. I am setting them up this weekend. I can report back.

In any case something like the Monoprice Monolith M10 V2 for $649 each is something to consider. $1300 a pair, I am pretty sure that will do that room to the max.


It will be difficult to DIY something comparable for significantly less $$. With driver and amp you already spend close to half that.

Of course returnable (with considerable effort as they are 73lbs each just for the 10's)if you don't like them. Your DIY is not returnable and difficult to sell to others without taking a big loss.
Of course the DIY time is time well spent and worth it no matter what IMHO.

8. Finally if you are new to woodworking follow the others advice and start with a flat pack. A quality sub cab of size is an advanced build in some ways. Focus on the basic's this time via the flat pack and getting the veneer right.

9. MDF or PLY wear a mask. Do not breath this stuff in (even plain old wood is actually toxic to breath in in quantity). Especially if you enjoy it and plan to build more. Get used to taking that safety precaution. Every chemical known to man is in most of that manufactured wood stuff.

Sorry I did not help with exact DIY drivers but I really think you can and least think about rethinking the size you will need. Especially if going ported/passive radiators where a 10 or 12 can meet and even beat a 15 or 18 sealed. (Or screw my small thoughts & go big or go home with the 15/18 ported and end up using lower excursions for very low distortion.)


If you go sealed after all. PE has a bunch of decent starter kits.
 
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concorde1

concorde1

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Here is my take. Just my personal take, I am not a famous dude.
Thanks for the great reply. From the start I was actually thinking a couple of 12" subwoofers, maybe 15". I don't really want to do a flat pack as I'd prefer not to rely on glue for holding pieces together.

If I want to spend more than the Monolith 12 THX, what would be some options you would recommend for 12" or 15" subs on the market?

Obviously the Perlisten D12S, but that is crazily expensive here. 4100 USD for one.

The Paradigm Defiance X15 is about what I want to spend, despite being marked up heavily. 2450 USD (1500 USD in USA)

SVS is marked up heavily, for example, PB16 Ultra is 4600 USD (2900 USD in USA)
PB-3000 is 2600 USD (1600 USD in USA)

Don't want Rythmik and they're not available here anyway.

JL is marked up heavily.

JTR is probably a no as I'm in NZ.

However, it seems Perlisten is not marked up much here, so that does make them more attractive, if not my best option if I spend more.
 

Chrispy

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Thanks for the great reply. From the start I was actually thinking a couple of 12" subwoofers, maybe 15". I don't really want to do a flat pack as I'd prefer not to rely on glue for holding pieces together.

If I want to spend more than the Monolith 12 THX, what would be some options you would recommend for 12" or 15" subs on the market?

Obviously the Perlisten D12S, but that is crazily expensive here. 4100 USD for one.

The Paradigm Defiance X15 is about what I want to spend, despite being marked up heavily. 2450 USD (1500 USD in USA)

SVS is marked up heavily, for example, PB16 Ultra is 4600 USD (2900 USD in USA)
PB-3000 is 2600 USD (1600 USD in USA)

Don't want Rythmik and they're not available here anyway.

JL is marked up heavily.

JTR is probably a no as I'm in NZ.

However, it seems Perlisten is not marked up much here, so that does make them more attractive, if not my best option if I spend more.
The glue will hold a flat pack together just fine, particularly when cnc-cut with rabbets. Hold it so well you likely can't break it apart at the joints...probably snap a panel first. All my glued up subs work just fine...clamps are nicer than using something like tape while it dries, tho.
 

ROOSKIE

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Thanks for the great reply. From the start I was actually thinking a couple of 12" subwoofers, maybe 15". I don't really want to do a flat pack as I'd prefer not to rely on glue for holding pieces together.

If I want to spend more than the Monolith 12 THX, what would be some options you would recommend for 12" or 15" subs on the market?

Obviously the Perlisten D12S, but that is crazily expensive here. 4100 USD for one.

The Paradigm Defiance X15 is about what I want to spend, despite being marked up heavily. 2450 USD (1500 USD in USA)

SVS is marked up heavily, for example, PB16 Ultra is 4600 USD (2900 USD in USA)
PB-3000 is 2600 USD (1600 USD in USA)

Don't want Rythmik and they're not available here anyway.

JL is marked up heavily.

JTR is probably a no as I'm in NZ.

However, it seems Perlisten is not marked up much here, so that does make them more attractive, if not my best option if I spend more.
As @Chrispy said good wood glue is pretty strong.
In MDF or PLY where it soaks in nicely it should be stronger than the wood itself.

But you can add screws in to any flat pack build at will or any build for that matter.

As far as exact recommendation I will let others chime in as I haven't used a lot of those subs. Some are designed to fill very large spaces with high SPL. That doesn't mean you can't go with them. They just likely won't be used to their potential. Note that an overloaded room is not going to sound good so plan to use PEQ/DSP for moderating strong modes and maybe some fine tuning.
 

Holmz

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Digger,

I’ll insert some thoughts in-line.

I have March Sointuva speakers on the way.
I was really surprized at how much bass that these speaker had on their own.
The lowest string on a bass is ~41 Hz, so I guess how low do you want to go?
Music only, or also home theatre? (I see it below now)

I am considering building a couple of powered 15"-18" driver subwoofers to fill in the low frequencies and take the load off the Sointuva's.

• My room is about: 13 ft * 15 ft * 11 ft (l*w*h)
Our’s is 14x 17 x 11 so very similar.

• For both music and movies.
• I don't mind waiting for stock, as it will be a while before I purchase parts anyway.
• The aim is to build something with excellent neutrality/linearity and very low THD.
Why? THD is really only issue with subs in that out hearing is sensitive to the only at higher freqs so it is only the harmonics we can hear.
Neutrality/linearity might be better replaced with low group delay and transcient response?

• Thinking of building the boxes with HDF or baltic birch, with a nice veneer on the exterior.
What finish are the Sointuva speakers?

I seek advice on:

• What drivers to use: I am happy to spend a lot on drivers.

• What corresponding plate amps to use: ditto.
Something like Hypex FA502 would be an option, and they have bigger ones.
Plus they have a stack of bi-quads for IIR DSP built in.

• Ported or sealed? I understand ported provides higher SPL output but is more difficult to design?
  • Sealed has lower group delay, and best transcient response.
  • Ported has lower distortion
  • Passive Radiator has less port noise than ported.
  • Bandpass has the lowest distortion, and highest group delay, and most difficult to design and worst transcient response.
    • But really for “shaking out last night’s curry” in the scary movie scenes.
If you are not using a DSP, and not using a FIR DSP, then transcient response, group delay and port noise are most likely your main concerns.

• How to design the boxes. eg what thickness of HDF, how to brace boxes, how to integrate ports.
as mentioned already… WinSD.

My rationale for DIY subs is: I think they are probably easier to design than any other audio component; I want to spend a bit less than a commercial sub; and I have some DIY experience in building my stereo amplifier.

If in the end I don't DIY I think I would instead invest in a couple of Genelec or Perlisten or Arendal.

If I can get a set of the Sointuvas then maybe we should combine forces?
  • Then the design work pretty much gets halved.
  • If there was a finish to match the Sointuvas, then the routing cost also goes down.
    • I am thing to match the speakers
  • We also have the same phase issues at play to marry up to the Sointuvas.

Personally I would probably go with a passive radiator for home theatre… but I already have a couple of 12” ones, some Earthquake SLAPS M12s, and a pair of FA502s.
Maybe tuned down to 15… Hz if the group delay is not too dire.
And… crossed over at 80-120 Hz, and run a 80-120 Hz high pass to the Sointuvas.
Or just go sealed.
I was thinking about making one of each (sealed and PR) out of scraps to test.

For music only, then 20 Hz would be more than enough low end, and sealed has good transcient response.

Personally I would go with a pair of 12” before a single 15”, or a quad of 12” before a single 18”.
IMO - bass seems best when you cannot tell if it is on, but can easily tell when it is not on.

And one can always use a butt shaker on the chair for the movies, so that also might favour end it all at 20Hz.

Are you intending on using a DSP at all?
 

fluid

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I am considering building a couple of powered 15"-18" driver subwoofers to fill in the low frequencies and take the load off the Sointuva's.

• The aim is to build something with excellent neutrality/linearity and very low THD.

I seek advice on:

• What drivers to use: I am happy to spend a lot on drivers.

• What corresponding plate amps to use: ditto.

• Ported or sealed? I understand ported provides higher SPL output but is more difficult to design?

• How to design the boxes. eg what thickness of HDF, how to brace boxes, how to integrate ports.
Here is a visual of the 18" BMS drivers next to something similar in size to the Sointuva's.

16538367832496337335242007846915.jpg

I went through a similar process myself a few years ago. My conclusion was Dayton 15" RSS390HF drivers in a sealed box, ~500mm cube.
For any other size driver in the 10" up range, all the Dayton HF drivers are equally as good and are really low distortion linear drivers with flat extended frequency responses.

BMS drivers are really great but to get them in the Southern Hemisphere is not so easy and the value proposition drops significantly. Thomann have good shipping rates and will sell the 12 or 15" BMS drivers for air freight making the price less exorbitant. The Dayton drivers are really good value but their performance exceeds their cost so don't be put off because they are not the most expensive option.

For box and build inspiration here is a great site from member @Wesayso
https://www.rsr-concepts.com/vandermill/?page_id=295

One thing that is often overlooked in the ported sealed or alternative debate is that sealed box woofers have a 12dB/oct rolloff. This is really the only way of getting very extended low frequency response. This is a point made by Linkwitz with his Thor subwoofers and also by Floyd Toole who chose sealed subwoofers for his own system.
It adds something that is hard to be without once you have heard/felt it.

For plate amps the Hypex Fusion series are hard to beat for sub use
 
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