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Noob needing verification

2K views 55 replies 9 participants last post by  michael hurd 
#1 ·
I'm in a rabbit hole right now chasing single digit frequencies without any prior experience. Hence the noob term is very fitting. I have planned out most of my components and want to make sure that I'm not overlooking anything and that I'm not going to blow anything up. I'm planning an infinite baffle setup with dual IB3v2 18" drivers and have tried to setup WinISD to test before I purchase my amp. I'm planning to take the RCA outputs of my Marantz 6011 and connect to a miniDSP with filters to prevent over excursion of the drivers. Then I'll connect RCA outs from miniDSP to speakerpower sp2-4800 amp. I have attached images from WinISD. I just want to make sure I set WinISD up right.

Is 2 drivers correct for a dual driver manifold?
Using the sp2-4800 would 2400 be correct for the system input power using 1 channel per manifold? Seems like my max power in winISD is going to be considerably less than the 2400 provided by the single channel of the sp2-4800. Should I consider a different amp?
The IB3v2 drivers have an xmax of 34mm so if all is correct seems I should be okay, or should I target a different xmax with my filters?

Any and all pointers/corrections are appreciated, total noob here.
 

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#2 ·
(2) 18" drivers total?!?
 
#3 ·
Will be four 18’s total, but this is for 1 manifold that will have two 18” drivers in it. Am thinking to split the 4800 to two channels one for each manifold. Not sure if you are puzzled that two drivers is inadequate or over the top. Like I said noob here looking for constructive responses
 
#4 ·
I had considered the sp4-2800 and running one 700w channel to each manifold, but 350w per driver seemed like I was leaving some output on the table. I could combine two channels on the sp4-2800 and send 1400w to each manifold, but the price difference between the sp2-4800 and the sp4-2800 is minimal so I figured I would just go with the sp2-4800 and extra headroom for nearly the same price.
 
#5 ·
According to (I can't post links) the driver can handle 600 W RMS.

I haven't used the multiple driver feature in WIN ISD but your maximum power graph doesn't look like it refers to 4 drivers. So if it refers to one or two drivers the maximum excursion might not be reached but the power would definetly be too much.
 
#8 ·
Hmm, I put in filters to limit the excursion. Is there a way to limit the power with DSP to protect it or is it simply a matter of not turning up the knob?
I was testing 2 drivers because I was planning to wire two 2ohm drivers in series to get a 4 ohm load to the amp. I’ll see what a single driver looks like, but I wouldn’t consider running that real world because the amp isn’t rated to run a 2ohm load. I guess it gives me an idea of how much power it can handle though. Wonder if the filters will screw up my excursion response too. I’ll give it a whirl
 
#10 ·
Yes it is an IB design. So when I drop to a single driver and half the signal system input power in winISD to 1200w I get the same excursions, which are limited by the filters I implemented. However the maximum power that I see is flat lined at 800W down to about 20Hz so I'm guessing this would be too much power if at max volume for the driver. Can I limit this power output with the miniDSP to protect the drivers from me cranking the gain up?
 
#11 ·
Just a side note: Xmax is not a standardized term. Technically speaking there is Xlin and Xmech. Xmech is always greater than Xlin and tells you the maximum excursion before the driver gets damaged. Xmax can refer to either, but it is more common that it refers to Xlin.

Once the excursion is greater than Xlin the disortion will increase rapidly but your speaker won't be damaged.
 
#16 ·
I'm not intimate with the minidsp, but most limiters are similar.
Very few, if any, are a brickwall, but it becomes exceedingly difficult to exceed their clamped output voltage.

When it comes to driver safety and single digit SPL, more cones and less power is better than more power and less cones.

I've never heard an IB in-person but I've heard that they sound very sterile, as the FR is very flat and free from box coloration.

I love single digits, I find myself dissatisfied with any system that doesn't have any (i.e. most systems having ONLY ported and horned subs etc).
I wouldn't be happy with a ported-only system unless it was ported to no-higher than 10hz, otherwise the rolloff will set in too early.
Gotta have me my
 
#17 ·
I'm not intimate with the minidsp, but most limiters are similar.
Very few, if any, are a brickwall, but it becomes exceedingly difficult to exceed their clamped output voltage.

When it comes to driver safety and single digit SPL, more cones and less power is better than more power and less cones.

I've never heard an IB in-person but I've heard that they sound very sterile, as the FR is very flat and free from box coloration.

I love single digits, I find myself dissatisfied with any system that doesn't have any (i.e. most systems having ONLY ported and horned subs etc).
I wouldn't be happy with a ported-only system unless it was ported to no-higher than 10hz, otherwise the rolloff will set in too early.
Gotta have me my
 
#26 ·
For optimum integration you will also need delay for your nearfield subwoofer manifold.
 
#28 ·
What box size did you set in winisd? It should be set to 100cuft or so to simulate no spring. Should not take much wattage at all to get to Xmax. That's what IB is all about. Low wattage = low heat on the coils = Less distortion. If you look at your spl curve. Wherever it is at 5hz is going to be where you'll be without room gain. You'll have to decide if that DB level is enough. Chasing single digits is about high spl at those digits or it won't be audible or felt very much. To get there you'll need a gaggle of drivers to move enough air. I think the ported IB like @MKtheater has would be a cool comprise to get more output down low.
 
#29 ·
At first I set the box size to 99999 but that killed my SPL estimate so I just kept taking off 9s until I got to 99 and that seemed to represent it well. Both winISD and that piston calculator @michael hurd posted show 99dB at 5Hz. If I add 2 more drivers to the ceiling manifold making 4 total in the ceiling it would make it 103dB. It really drops off a cliff after that and I would have to get up to 24 drivers to hit 115dB. That is ignoring room gain though right? I would assume that with room gain it will make a huge difference. I will have to search for this ported IB and read up.
 
#30 ·
@MKtheater has an amazing setup, but I would have to skip the IB, from what I read he has a massive multidriver ported box rather than true IB. I like the idea of using the Fi speakers made here in town too. I also don't think I have the real estate in my room to go that route which is why I am focusing on the IB setup. I bet the tactile sensation in that room is unreal though...
 
#37 ·
@MKtheater has an amazing setup, but I would have to skip the IB, from what I read he has a massive multidriver ported box rather than true IB. I like the idea of using the Fi speakers made here in town too. I also don't think I have the real estate in my room to go that route which is why I am focusing on the IB setup. I bet the tactile sensation in that room is unreal though...

Thanks, but I bet my system has changed a few times from what you looked at. The Fi drivers are great and work really well. I got rid of them because I wanted to try a very low tuned ported. Here is the reason. I really like single digit pressure adding to the experience. Since my room is small I get easy pressure from them. I was running 8 Fi IB3V2 in a sealed baffle wall, about 200 cubes, maybe more depending on bracing. They were awesome. Then I decided to try a LT boost on them and the tactile response went up significantly! It was so crazy I could no longer run my subs 12 dB hot. I ran a few scenes I like to demo, Lone Survivor being one of them, and my 20 amp breaker would trip. Running the LT with subs hot was too much for my breaker, so, I decided to port them down low rather than the LT. My enclosure was too small for the Fi drivers with ports. So I switched out to SI ht 18s and they could be ported with my enclosure. The Fi drivers are more powerful than the SI 18HT for sure, but require bigger boxes as they are IB drivers. The port uses much less power and gives you the tactile response of the LT, the down size is it drops off at 5hz in my room where the sealed went to whatever the amp could provide, at that time it was a clone at 3hz.
 
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#35 ·
My suggestion is to use both manifold locations, but to limit the bandwidth of one location. I would tend to limit the bandwidth of the nearfield 2x18" to 50 hz and down, leaving the other location to reproduce the full bandwidth of the LFE channel.
 
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#41 ·
Been real busy with work lately, but I guess gotta work to pay for the toys :D

I would have to buy a small sub to measure for the ceiling manifold...just not sure if I want to do that. The ceiling is a tray ceiling and will require significant modifications to place the manifold at the edge of the room. I'm still in debate about whether I will acquire a cheap small sub to measure for the ceiling manifold or just use the REW room sim.

I had not considered limiting the bandwidth at the nearfield. What would the benefit be in using a low pass filter on the nearfield manifold? I was thinking that the chest slam type of tactile response would be best produced by the nearfield drivers and would be best at frequencies above 50Hz. Curious to hear about limiting the nearfield bandwidth though if you could expound more. I guess its something I could play with down the road once setup to experience the differences.
 
#36 ·
It is funny, I am planning on basically this same build using the FI IB drivers. Thinking about two manifolds with 2 drivers each but I will have to wait until my cross spectrum umik1 gets here (also was waiting on the new batch of mics). Also planning in ceiling and eq through minidsp hd :) Curious to see how this works out.
 
#42 ·
I guess they just shipped the UMIK-1s looking forward to playing around with it, but still have a lot of work before I can build anything in my planned room to measure. Will be curious to see how you get along. I ordered 2 ohm IB318 drivers thinking I would use the speakerpower sp4-2800 or get two sp1-1400 plate amps from speakerpower to power the 4 drivers. I was going to wire the two 2 ohm drivers in series to present a 4 ohm load to the amp, but after talking to speakerpower the sp4-2800 and sp1-1400(more accurately saw it listed as sp2-1400 in one spot) uses individual 700w ICE amp modules that aren't stable below 4 ohms. This meant with 2 ohm drivers I would only be able to hook up 2 drivers in series to a single 700w channel and only get 350w per driver. I stopped by Fi after work and the guys were great and switched my order to 4ohm coils. After talking to speakerpower I also decided to go with the sp2-4800 and will wire two 4 ohm drivers in series to give me 8 ohms and 1300w per channel, 650w per drivers. Much closer to the 600w@20Hz that Fi specifies for the drivers. Keep me posted how your build goes.
 
#38 ·
Room gain is maximum 12 dB per octave which depends on your room. You mentioned your gain will start at 23hz so the max you can get is 24 dB at 5hz if you don't have any bass leaking out. I have all concrete behind my walls except the ceiling and I get 10 dBs per octave of gain.
 
#43 ·
I'm all wood walls at ground level so I'm sure I'll get some leakage especially through the double doors that enter the room. They are solid core doors that weigh a ton, but don't seal. If I could get 8 dB per octave that would theoretically get me to reference 115Hz. I'm sure I would be happy with that...at least for a few days before I started wondering what if:D

How do you like that sp1-4000? got an sp2-4800 on order now. I sure hope all this equipment rocks my world once I get a chance to put it all together
 
#39 ·
I'm in a rabbit hole right now chasing single digit frequencies without any prior experience.

Welcome to the club.
Just to forewarn you the rabbit hole is bottomless. As Jerry Garcia said too much of everything is just enough.
 
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#44 ·
The low end gain from rooms add the weight and pressure from deep bass. I have tried so many systems with varying low end frequencies and I always preferred the deepest extending systems. My room is very good for them. I have tried to go with subs that don't dig as low but if your room allows for it get it! The IB subs from Fi will give you as low as your room and amps will allow. Deep bass and room gain requires your subs to be located further away because as you get closer the subs response will take on a near field response or an outdoor response.
 
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#49 ·
Put the sub in your seat at ear height if possible and then use your mic with the rta and pink noise full band. You can then hold the mic where you plan to put your manifold and get an approximation. Move it around the ceiling to find the best spot.
 
#50 ·
I like this idea of reversing the sub and mic, but as I think it through I wonder how this works when running dual subs. Won't there be interactions when the two subs are present that won't be when just measuring with one sub and mic? I like the idea, but when I saw how much changing 1 of 2 subs affects the overall curve in REW simulator I got a little discouraged that it will be hard to predict without actually having the two subs in the room.
 
#53 ·
My cross spectrum looks like it will arrive tomorrow. Then I will have to spend some quality time with REW and I do plan on doing two manifolds and the sub mic crawl at different locations around the ceiling for the best spots. I will have to assemble the box in the attic though since the opening isn't large enough for a finished box. I am pretty excited to eventually hear some effortless clean bass. Right now my garage theater way out performs my house set up in terms of bass due to two VBSS's vs 1 Dayton Sub-1500 in the house.
 
#55 · (Edited)
To hear 20hz requires 70db.
To hear 10hz requires 100db.
To hear 5hz requires 130db.

and all of this must be below 10% THD or it will sound like the 2nd and 3rd harmonics of these tones.

and that is the minimum requirement, at X distance.

Ear damage below 20hz is at around like 160db (or even higher...)

To hear 1-2hz basically requires ear-damage spl. ;) (Which you'll never reach if you have ducts, doors or windows because of the leaks, it only works in a welded-metal coffin...)

It is possible to hear 0Hz, just ride a SpaceX rocket and tell Scotty to open the hatch. The air pressure will go from 1 ATM to 0, or 191db... You'll be blown out the hole in a million pieces, i.e. it is possible you'll hear it (but only ONCE. hehe! :D) Alternatively, just sit below the rocket when it ignites. The results will be similar...
 
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