[a77cj7]

I've decided to build a MBM and split my sub stage into a two way config. However, I'm hoping to get some tuning advice as I'm completely new to this.

Current system:
Processor: Emotiva Fusion 8100
Mains: Goldenear Trition 5's
Center: Goldenear Supercenter XXL
Surrounds: Goldenear Invisa 7000 In-Ceiling
HF amp: Crown DCI 8/300 (300w rms x 8 at 4 and 8 ohm)
Subwoofers: 2x SI HT18D4 (v1) in 4cf flatpacks. (will be upgraded to HST's, black friday sale maybe?)
Sub amp: Crown DCI 4/1250 (1250w rms x 4 at 2, 4, 8ohm, 2500w rms x 2 at 4, 8, 16ohm bridged) (20a Dedicated circuit)
Additional Sub: Goldenear Supersub XXL, nearfield behind MLP (hopefully not permanent here, looks horrible and takes too much space)

Usage is 90% movie, 10% music

Due to my relatively small mains and VLF subs, I have a significant response gap from 50hz to 120hz, just from running sine sweeps.

I have a minidsp 2x4 bal and omnimic, just haven't had time to set it up yet. I'm pretty sure EQ can't fix this issue though, since the Crown amp will be more than capable of melting down HT18's at higher frequency.

I started playing with the idea of adding 1-4 PA460's as MBM's, either nearfield behind main seats, or on front wall under center. Most designs just take up too much space for my setup though. Then I started reading up on specs and box recommendations for higher end PA drivers. I discovered the B&C 18DS115, which wants a 3.5cf box at 40hz.

So I ordered a the B&C 18DS115 and a blank baffle 4cf flatpack from PE. I plan to mount the woofer off-center toward the top of the baffle, leaving space for a 2" slot port at the bottom.

My two HT18's are set up on the front wall under the screen, on either side of the center. One will be moved to the back of the room, with the MBM in its place to keep the symmetrical appearance.
The HT18's are currently bridged on the crown, avoiding input sensitivity mismatch mostly. With the addition of the miniDSP, I will set them up on 1250w channels, with a 2500w bridged channel left for the MBM.

When I upgrade to HST's, I will get an additional amp. Crown 2/1250 or 4/1250. 2500w rms available to all three subs. Hope the 20A breaker can take it.

My mains are currently running to 80hz, will change to 120 or 150 with the addition of the MBM.

Sorry about the book, but I believe too much information is better than too little.

TL/DR: I have 2 SI HT18's sealed in 4cf flatpacks. I'm adding a B&C 18DS115 in another 4cf flatpack, ported at 40hz. I have plenty of amp for all three.

Does anyone see any problems with this setup?
How about crossover recommendations for the two way sub setup?
Is the 40hz port tune optimal?

Thanks,
Chris

 

[jcr159]

good luck! hope you find the bass you are looking for!

only concern i'd have is that without measuring, how do you "know" for sure the hole you have in freq response... just saying that some tweaking of what you have might be enough... I'd do that before adding another build, and another pair of crossovers to integrate which for sure you'll need to measure to optimize...

super curious to hear how it works out!

 

[a77cj7]

I know its missing because I can hear it. Not the most scientific response I know. I have/have had many other subwoofer systems, and none has had the insane LFE of these 18's, but all had more punch in the higher bass region. Running just the 18's for music leaves me with very little punch, while the supersub is significantly better. Even the cheap ported 10" paradigm in my shop "hits" much harder at high bass.
I could throw some eq at the 18's, but I'm already powering them with 4x their rated power. I'm sure I'd melt em down trying to get the higher frequencies boosted. I love the 20-50hz range of these subs, but they just completely fall off over that. Switching to HST's as planned would take care of the power handling, but results in subs even more poorly suited for the higher frequencies.

With all the super positive reviews I see on here of MBM's, i decided to take the plunge without measurements. I know its premature, but I'm itching for another build. Its only been a few months since I built the HT18's (after they sat in my shop for 3 years plus, lol), and I want to do more. This game is super addicting.
I will get the MiniDSP setup and measurements taken, but just haven't had the time yet.

I just downloaded and started playing with WinISD over the last few hours. So far, its telling me I purchased the wrong sub i'm pretty sure. Also, its showing me that port velocities are a major issue with these ridiculous drivers.
I've been trying all sorts of different 18" subs in the 4cf box. Sadly, I'm pretty sure I found one that way outperforms the 18DS115 at the same cost.

Modeling the 18DS115 in 4cf tuned to 40hz. HPF 2nd order butterworth at 40hz, LPF 2nd order butterworth at 150hz gives me a damn near perfectly flat response from 40-120hz. Throwing the whole 2500w on it gives me 125db, but also 37m/s port velocities. Halving the power drops it to 122db, 26m/s. Changing the crossover to 50hz drops port velocity below 20m/s, with closer to 120db at 50hz.

Modeling the 18SW115 in same box, with same crossovers gives me -1db at 40hz, +2 at 50hz, +3 60-90hz, +2 at 100, and tapering down from there. Port velocities are lower, due to lower volume near tune. 32m/s at 2500w, 23 m/s at 1250w.

So for the range I'm looking at, I'm pretty sure I need to exchange the 18DS115 for a 18SW115. Modeling sure ends up differently than going by manufacturers specs. I wonder what that will cost me in shipping.

Is my interpretation correct, or is the flat response valued over the additional spl?
Do my filters and tunings make sense?

Modeling the HT18's sealed show a higher spl 50-100 hz than 20-50, so that also really confuses me. Is room gain effecting it that much?

I really hope some experienced people help me with this before I waste more time and money in wrong directions. I'm feeling really lost here.

Thanks,
Chris

 

[jcr159]

I think a lot, but obviously not all are chasing room/ placement issues with MBM’s to be honest....

That said, I’m crazy worried about things like in room response and positioning of the 2 MBM’s, 2 sub, and how the 4, their crossover behaviors, time alignments and group delays will ever integrate cleanly... since the room is such a huge part of the system in low frequencies, it’s tough to know until you start working pieces together. All this was what piqued my interest as it sounds crazy hard so I can’t wait to see how it all works out! And measurements are good to make sure that what you are hearing isn’t a room mode/null, etc. easy to see how even the response is as you move around the room.

Myself I’d probably just build 2 more 18’s(though they’d need to be um-18’s since the hot-18 isn’t around anymore), and just go the MSO route. But I don’t listen at reference (more like -15), where some eq can get the job done unless your space is a bajillion cuft

🤪

Again, can’t wait to follow your progress, sounds like you have a clear plan on mind!

 

[lemonslush]

I have the ht18s and you may need to adjust the DSP settings to get them playing to your room and ears. Just sticking a sub in a box and hoping for the best wont yield the best results.
Personally I would take the sub you just bought and build a larger ported box for it. The higher sensitivity compared to the h18s will make at least 8db louder on 1 watt and that's not accounting for room gain.
Additionally the tuning of lots of out of the box subs has a much higher mid range curve for many reasons. One being most people dont turn their subs up very loud so they have a elevated mid level vs a flat response. Its most of the time a simulated bass vs how the recording was actually intended to be. Just remember a movie you watched in a movie theater and then watched it later at home. The ht18s tuned correctly should mirror that response and not be blasting bass the whole time. If the ht18's are not loud enough you could try larger boxes. A bigger ported box will get you much more output than the sealed because those subs have a weak motor and really should be ported IMO. Also room positioning helps a ton. I had huge nulls in my old theater setup and I kept adding subs with zero increase in volume. I eventually smartened up and put my subs in optimal locations and got a much flatter even response with half the subs.

I know companies make flat packs for the diy ported subs builds now if your not into the cutting part.

 

[a77cj7]

Its not the cutting that i’m avoiding so much as keeping box size down. With the power i’m running to them, I can hit xmech from 40hz down according to winisd modeling. I can confirm this from the nasty thunks on the ridiculous bass scenes if i’m not careful with volume control. I’m sure I can increase LF output with a very large box ported low, but I don’t have the space.

I did realize I misunderstood winisd box modeling in that it doesn’t remove port and driver displacement from entered box volume. It also doesn’t account for additional friction encountered by slot ports.
Using dual 2.25x8.875x14.5 slot ports with 3.2cf net box volume gives me a very nice flat response with the 18ds115 driver. According to a slot port calc, that should be 38.5hz. Winisd comes up with 42-43hz. Doubling box size gives it a wicked peak near port tune, without increasing spl above 50-60hz.

Now the previously mentioned 18sw115 would love a 5.3cf net box at same tuning. It would give the same flat spl curve, but up 3db at given power.

Due to my space constraints and the fact I already bought the 4cf flatpack and ds woofer, I will be using that setup. Just the offset woofer and port is gonna mess with my ocd compared to the matching sealed box. I like symmetry, especially right under the screen.

I know my setup is loaded with compromises, since I have no sound treatment, trying to keep box volume minimal, and using a few high powered subs instead of ridiculous cone area. I’m sure 32 pa460’s would be far superior to 2 hst’s and a ds in small boxes, but not what i’m going for in my space.

What I was hoping for was some suggestions on crossovers and how to deal with phase issues. I know mixing sealed and ported is challenging to tune, but using a 2 way sub setup is supposed to make it easier.

Also would love feedback if anyone has tried an undersized and overpowered mbm.
Or just generally integrating a ported mbm with sealed subs.

I am very inexperienced at sub tuning for ht use, other than just crossover adjustments by ear. I should have the tools with the minidsp and omnimic, but I have a feeling it’s going to be one hell of a learning curve.
I’m also crippling tuning by the fact the front sub and mbm have to stay at fixed locations. I can move the rear around some.

Thanks,
Chris

 

[Will P]

I would allocate no more than 2 octaves for the sub-woofer and 2.5 octaves for the bass.
12in woofer drivers for the bass.
That is 60Hz sub-woofer upper x-over and 240Hz bass upper x-over.

 

[a77cj7]

Got the parts, i’ll try to get the build knocked out this weekend along with some automotive projects.

I’ve never built a ported enclosure before. How do you paint the inside of the port? Should I try to duratex it like the rest of the box, or just black spraybomb? Ports will be pointing at MLP, at floor level.

Also, I’m seeing lots of conflicting info on whether the box should be lined. Should I use denim insulation or just leave it out?

Chris

 

[a77cj7]

I'm not getting much for responses, but I guess I'll ask anyway.

I've got a dilemma on roundovers. With the ports, I'll have multiple edges that are 3/4in thick. The flatpack already has 1/2in roundovers on the front panel.

Has anyone tried 1/2 roundovers on both sides of a 3/4 panel? My other boxes have a 1/2 roundover on all edges, so consistancy would be nice if possible.

Option one: Use 1/2 roundover on all edges, and inside the ports.

Option two: Use 1/2 roundover on all edges, and 3/8 inside the ports.

Option three: Cut a new front baffle. Use 3/8 roundover on all edges and inside the ports.

I'm going to try a 1/2 roundover on a piece of scrap first and see what it looks like, but I assume someone has run into this issue before and would have some insight.

Thanks,
Chris

 

[a77cj7]

I’ve been running this sub for three weeks now. It accomplished what I was going for, filled in the 50-100hz section. I’m loving the TR it adds.
I’m currently running it 40-120hz, and the sealed HT18’s 0-80hz. Need to take the time to learn REW and my minidsp mic and see what its actually doing, but sounds good to me so far.
Of course, I’ve been reading this site too much, and have fallen down the rabbit hole badly. I’ve since added built in mini boss platforms, and ordered a pair of HST 18’s during the sale for some LLT Sonosubs.
If its still not enough, a pair of GSG devastators sounds interesting.
Chris

 

[Augerhandle]

Just for perspective, I'm running my HT-18s in 10.5 cubic ft. enclosures.

 

[a77cj7]

Just for perspective, I'm running my HT-18s in 10.5 cubic ft. enclosures.

Sealed or ported? I can already bottom them in the 4cf boxes, so no gain for me by going larger sealed.

 

[Augerhandle]

Sealed or ported? I can already bottom them in the 4cf boxes, so no gain for me by going larger sealed.

Ported, tuned to 16.5 Hz, flat to 12 Hz in room.

 

[a77cj7]

Ported, tuned to 16.5 Hz, flat to 12 Hz in room.

Sounds like a nice setup.

My plan was to transfer my ht18’s into some LLT sonosubs.
Then Nick put the HST-18’s significantly on sale and I couldn’t resist. So my HT-18’s are staying in the sealed boxes. Used for room smoothing, and because I don't know what else to do with them. Plus they look good under my screen till I build something stupider.

Chris

 

[Augerhandle]

Where are you located? I'm sure there's plenty of people willing to take those HT-18 drivers off your hands.

 

[a77cj7]

Where are you located? I'm sure there's plenty of people willing to take those HT-18 drivers off your hands./forum/images/smilies/wink.gif

Sturgis, South Dakota. Not much of a local market around here.
Doesn’t help that the nicely finished boxes are worth as much as the drivers, lol.

What I really need to sell is my Goldenear Supersub XXL. Its a very impressive sub for the form factor, but the 18’s made it seem a bit weak. 😉
I’ve been using it as an inconveniently shaped nearfield, but the BOSS made that unnecessary.

Chris