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post #1 of 54 Old 06-12-2014, 04:57 PM - Thread Starter
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Aiming for 105-110dB @ 5Hz in room (not a field!)

I've recently completed a round of upgrades, one of the aims of which was to hit a clean 110dB@20Hz using a single sealed sub. I think this was successful yet I am now contemplating what it would take to get to the next level & whether that is feasible in my room. I blame reading this forum too much in recent weeks

Anyway it would be great to get some ideas/feedback as whether I'm on the right track and/or ideas on how to proceed.

To kickoff I thought I'd share some details of my room & what I'm aiming for.

Aims
My maximum normal listening levels for films are about -10, if I crank it up then it means -5, it never means reference. This means I have no intention of paying for true reference capability as I don't really have the space to spare for it. I would like to achieve a *clean* 110dB if I can, I'd settle for 105dB if I have to though.

This begs the question of what does "clean" mean? Based on various tests I've done here & based on the limited space I have, I think this means something like a 10% distortion limit. I would be *really* interested in personal experience in targeting/hearing systems with different distortion levels mind you.

My Room
My house is a typical Victorian (built in ~1880) house in London which means; wooden floors over a ventilated void, open chimney, solid brick walls, high ceilings.

The room is actually our lounge albeit it is largely dedicated to AV, some pics from my sketchup model;

Plan View
The room is ~13' 6' x 12' x 10'



From Listening Position
Distance to screen and sub is ~10'


From Entrance
The blue oval highlights the readily available space for subs


The footprint of highlighted alcove is about 40" x 22"

The next couple of posts will describe my signal chain & where I've got to so far with some initial modelling.
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post #2 of 54 Old 06-12-2014, 05:09 PM - Thread Starter
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My Signal Chain

I run everything from an HTPC running JRiver with all EQ provided by filters created by acourate. My signal chain goes

HTPC
-> firewire -> Focusrite Saffire Pro 24
-> line out -> Marantz AV7005
-> pre out -> amps

I have measured the rolloff at various points and came up with the following graph (which I posted here earlier, bit off topic there though)



red = soundcard cal for my onboard line in/line out
yellow = focusrite saffire pro 24 line out to onboard line in
blue = focusrite saffire pro 24 line out to marantz av7005 pre out
green = marantz av7005 response only (i.e. delta between blue and yellow)

The AV7005 is in pure direct mode

The sum total points to -3dB at 3Hz, -2dB at 4Hz, -1.3dB at 5Hz and -0.3dB at 10Hz

I use a Dayton EMM-6 mic calibrated down to 5Hz by CSL. I read all this as indicating my existing signal chain is good for 5-6Hz with appropriate correction when measuring.

Room Gain
Having verified my signal chain, I then took another measurement at the listening position down to 5Hz. I overlaid this on a nearfield measurement of my sub & then plotted that against a straight 12dB/octave rolloff. This gave me this view on room gain/transmission loss which suggests my <20Hz room gain pretty much counteracts the natural rolloff of a sealed sub. I'm not sure how much I trust the <10Hz numbers given they come from a 15" sealed sub but it's all I have to go on right now. The lack of gain in the 20s is absolutely unexpected in my room, I've fought this ever since moving to a sealed setup.

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post #3 of 54 Old 06-12-2014, 05:22 PM
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You will need deep pockets.

5 to 10hz requires a minimum investment of $5-7k

Four sealed LMS's powered by 2 FP14k clones and two 30amp breakers should get you close.

Since you live in London shipping will be hella expensive.

Unless you happen to have access to good drivers inside the EU.
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post #4 of 54 Old 06-12-2014, 05:39 PM - Thread Starter
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Setting Some Theoretical Targets

Based on the data in the previous posts, my initial take on the woofage that would deliver on paper (i.e. WinISD) is as follows.

The start point is needing 110dB at 5Hz
A sealed setup rolls off at 12dB/octave so I need 122dB at 10Hz
I get +12dB from room gain from 10 to 5Hz so I'm back to needing 110dB at 10Hz.

WinISD models at 1m but my listening position is 3m so worst case I need to add ~9dB to the model (probably less in reality? but lets be pessimistic)

Total room gain at 10Hz is ~12dB though which more than cancels out the listening distance.

Therefore I need to model for 107dB at 10Hz with 102dB as a fallback option.

Where can I put subs?
I have 2 near field locations available and 1 further away, these locations are marked in red on the pic.

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REW room sim says the near field positions will not play nicely with the existing sub location. This suggests that the only way forward is to occupy that alcove completely with subs.

The alcove is ~40"x22" so I think this means an enclosure in the region of 200L is feasible.

The only danger here is that an enclosure that fills the alcove will produce a stronger, early reflection off my R speaker (whether this will impact SQ in an untreated room is another Q, it will certainly be a stronger & earlier reflection than I have now though).

Some pics of common enclosure designs to illustrate

A tube stack
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A column stack
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sideboard style
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Modelling Near Field
The main doubt here is that the room sim is only accurate when I stay away from the alcoves however this is simulating a sub in an alcove so I don't know what will really happen. FWIW though
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The sim says that subs in the alcoves really screws with the consistency of the response across the sofa. In the corner alone, there is a variance but it is manageable.

What next?
The most interesting Q to me right now is whether my modelling (of my room) is correct. If this is off then any attempt to design for the room will fail.

The 2nd Q is what "clean" really means. I don't have the space to chase 1% distortion at ULF and high SPL, it's just not feasible so I have to compromise. 10% (-20dB) seems like a reasonable compromise based on it being more aggressive than CEA-2010 but not as aggressive as typical HF distortion figures.

Any and all comments much appreciated!
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post #5 of 54 Old 06-12-2014, 05:46 PM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
You will need deep pockets.

5 to 10hz requires a minimum investment of $5-7k

Four sealed LMS's powered by 2 FP14k clones and two 30amp breakers should get you close.

Since you live in London shipping will be hella expensive.

Unless you happen to have access to good drivers inside the EU.
I can get multiple 32A feeds straight from the consumer unit if required.

If it's worth it and doable then I can cope with spending that sort of money. However, in the first instance, I just want to see what it would take to deliver this. Once I can see this, if I need to scale back my goals then so be it (though my current thinking is bumping from a clean 20Hz to a clean 15Hz is probably not worth the effort/expense).

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post #6 of 54 Old 06-12-2014, 06:23 PM
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not the first time I or many others here, many of whom have much more creditable/proven experience, have seen a request trolling the 'cognoscenti" for answers for such extremes.
there was a similar OTT request not even that long ago


best answer, no contest or further discussion needed I ever saw was:


you're a candidate for that $25,000+ (Japanese?) rotary sub . get 2. you know at least 2 or more are needed to help with room modes . .


iirc you can ask "BigDaddy" over at HTS. maybe it was Audioholics. I dunno but it was a good read


OOMBP


you may also care to delve into the acoustic physics wrt human hearing sensitivity and while you're at it maybe even tissue damage, and the (annihilating) Db needed to actually have 5hz be heard, the power that is needed wrt to doubling of available power for every 3Db to push things to that level


If you can pull that off for "only" $5-7K, there must be alien technology involved. keep us posted about THAT!


there's something deep here alright


What's in YOUR wallet?

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post #7 of 54 Old 06-12-2014, 06:30 PM
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a modest proposal

there are charts available showing Db needed for all freq's.


the last one I saw was posted by Bill Fitzmaurice.
For that ULF, the Db was like insane, to say nothing of the power needed
He's one heck of a go-to source


back to the drawing board

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post #8 of 54 Old 06-12-2014, 06:56 PM
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Here is my results in the real-world (not box model):


One LMS runs out of excursion at around 105db @ 10hz @ 10.5ft in my 3000cuft room.
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post #9 of 54 Old 06-12-2014, 07:03 PM
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Bassthathz,
You do not need to spend that much.
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post #10 of 54 Old 06-12-2014, 07:09 PM
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a better option would be to run a 18 from 15hz up and use some bass shakers b/c u wont hear 5 hz anyways just feel it and u can feel it for a hell of a lot cheaper
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post #11 of 54 Old 06-12-2014, 07:10 PM
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Here is quad LMS's and with 4x the power as well.


8 UXL-18's and two FP10kQ's shipped to London would probably be about $7000 or euro's or whatnot.

You only need 16amp breakers because you use 220volts in London.
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post #12 of 54 Old 06-12-2014, 07:14 PM
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OP- you've got one SP4 already, right?

Here is my four SP4s on 15kw in ~2000 cubes. Yes.... I know the graph does not go below 10. You'll just have to take my word that I'm not down more than 3db @ 5hz.

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post #13 of 54 Old 06-12-2014, 11:13 PM
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I can do that for $3000. I use 8 18 inch IB drivers and lots of power. The key and more important is signal chain roll off. Make sure your equipment does not roll off before 5 hz or it will be impossible. I had a Meridan 861 that rolled of at 7 hz and no matter what I could not get that setup to 5 hz. Changed processors and all of a sudden I could.
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post #14 of 54 Old 06-13-2014, 05:09 AM - Thread Starter
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I'm not sure if my intent has come through or not, the title refers to *in room* not outside. I didn't think this was that controversial a topic tbh given some of the systems around here

Quote:
Originally Posted by pdxrealtor View Post
OP- you've got one SP4 already, right?

Here is my four SP4s on 15kw in ~2000 cubes. Yes.... I know the graph does not go below 10. You'll just have to take my word that I'm not down more than 3db @ 5hz.
yes I have 1 15" SP4 atm. Is that peak output in your room?

Quote:
Originally Posted by MKtheater View Post
I can do that for $3000. I use 8 18 inch IB drivers and lots of power. The key and more important is signal chain roll off. Make sure your equipment does not roll off before 5 hz or it will be impossible. I had a Meridan 861 that rolled of at 7 hz and no matter what I could not get that setup to 5 hz. Changed processors and all of a sudden I could.
From what I can see, leaving the question of sufficient power to one side, the whole exercise really seems predicated on room gain/transmission loss & signal chain roll off. I posted my measurements above. Does this look accurate?

In my room this gives enough boost to counteract the rolloff of a sealed sub so am I right in thinking that delivering 110dB at 5Hz equates to delivering 110dB at 20Hz assuming I have sufficient power on tap?

If so then that turns the actual requirement into 119dB at 20Hz (adding +9dB for converting 1m model to 3m listening position) doesn't it? or is this an overly optimistic use of a model?

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post #15 of 54 Old 06-13-2014, 06:13 AM
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Finally a thread that is down to earth!

My build thread

My 8 x RE XXX 18" Subwoofers, IB build
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In a room that size I think any four sealed 18's (or larger) with decent excursion would get you there. Two might even, but with the different roll-offs at 5-10 hz you will probably need 4. The room gain in your room should be pretty nice, starting at around 42 hz, you should have +12 dB at 20 hz, +24 dB at 10 hz, and +36 dB at 5 hz. I assume your room isn't perfectly sealed so you will lose some room gain as these numbers only hold true for a perfect sealed room.
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post #17 of 54 Old 06-13-2014, 01:21 PM
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Quote:
Originally Posted by 3ll3d00d View Post
I'm not sure if my intent has come through or not, the title refers to *in room* not outside. I didn't think this was that controversial a topic tbh given some of the systems around here


yes I have 1 15" SP4 atm. Is that peak output in your room?


From what I can see, leaving the question of sufficient power to one side, the whole exercise really seems predicated on room gain/transmission loss & signal chain roll off. I posted my measurements above. Does this look accurate?

In my room this gives enough boost to counteract the rolloff of a sealed sub so am I right in thinking that delivering 110dB at 5Hz equates to delivering 110dB at 20Hz assuming I have sufficient power on tap?

If so then that turns the actual requirement into 119dB at 20Hz (adding +9dB for converting 1m model to 3m listening position) doesn't it? or is this an overly optimistic use of a model?
That was a -20 dbfs sweep with REW. 75db cal at LP, boost noted in picture. Take away the boost, and up the REW output volume to -3 should put me at peak, just haven't had time to do it yet. Need to first dial in my amps. You know about that situation.......

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post #18 of 54 Old 06-14-2014, 01:09 AM
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If the room isn't sealed chances are you won't get anywhere close to that gain. I would be conservative and say expect 15-20 db of gain at most at 5hz. And as others have said make sure you are using equipment that won't roll off until 5hz or so to make sure that as much power as possible is being efficiently used.
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post #19 of 54 Old 06-14-2014, 02:41 PM - Thread Starter
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Quote:
Originally Posted by Petden View Post
If the room isn't sealed chances are you won't get anywhere close to that gain. I would be conservative and say expect 15-20 db of gain at most at 5hz. And as others have said make sure you are using equipment that won't roll off until 5hz or so to make sure that as much power as possible is being efficiently used.
My measurement of room gain is in an earlier post in the thread, it's not too far off what you've suggested as it indicates 20-25dB by 5Hz.

I realised I was underestimating the output required new calculation is

Target = 110dB at 5Hz
Room Gain = ~22dB
Room Gain adjusted target = 88dB at 5Hz = 100dB at 10Hz = 112dB at 20Hz
Distance adjustment ~= 6dB
New Target = 118dB at 20Hz

If this target is accurate then it seems to suggest that 2 Fi SP4 18 come close. I'm basing this on the power I currently have available; 2000W at 8ohm, 3200W at 4ohm, 6000W at 8ohm (speakerpower SP1-6000).

2 of those drivers (chosen as they are easily available in the UK) wired to present 4ohm (i.e. 2 dual 1 ohm), placed in a 220L enclosure (roughly a 40" x 22" tube) and given 3200W produces a system with Q=0.724 & excursion is capped at about 24mm. My current SP4 loses control at ~27mm (distortion passes 10% or -20dB here and escalates quickly) so if this holds true for the bigger driver, albeit in a completely different enclosure, then it seems to say I could get away with 2 18" if I relax my goal a little.

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On the other hand, this is a system that is *just* getting there. I suppose I could always start with a single dual opposed tube and then add another, if need be, later. 3 such drivers seems to be exactly on target, are there any good cabinet designs that accommodate 3 drivers though?

@pdxrealtor I used your measured winisd model for the above, I think you said you had some tweaks to that driver or am I misremembering?
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post #20 of 54 Old 06-15-2014, 12:15 PM
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Here's the T/S specs off one of my actual drivers. The driver was slightly broken in before the measure. The only change made to the driver was less spiders, and the spider spacer.

FI SP4 18” D1 HT – Two spiders, spaced.
DCR 1.41 Ohms (both coils wired in series)
FS 21.4 Hz
Qms 6.50
Qes .45
Qts .42
LE 1.310 mH
Vas 229.45 l
MMS 496.22
SD 1210cm^2
BL 14.47
CMS 1.119x10^-4 m/N
SPL 88.7 1W/1m

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post #21 of 54 Old 06-15-2014, 12:16 PM
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Quote:
Originally Posted by 3ll3d00d View Post
Quote:
Originally Posted by Petden View Post
If the room isn't sealed chances are you won't get anywhere close to that gain. I would be conservative and say expect 15-20 db of gain at most at 5hz. And as others have said make sure you are using equipment that won't roll off until 5hz or so to make sure that as much power as possible is being efficiently used.
My measurement of room gain is in an earlier post in the thread, it's not too far off what you've suggested as it indicates 20-25dB by 5Hz.

I realised I was underestimating the output required new calculation is

Target = 110dB at 5Hz
Room Gain = ~22dB
Room Gain adjusted target = 88dB at 5Hz = 100dB at 10Hz = 112dB at 20Hz
Distance adjustment ~= 6dB
New Target = 118dB at 20Hz

If this target is accurate then it seems to suggest that 2 Fi SP4 18 come close. I'm basing this on the power I currently have available; 2000W at 8ohm, 3200W at 4ohm, 6000W at 8ohm (speakerpower SP1-6000).

2 of those drivers (chosen as they are easily available in the UK) wired to present 4ohm (i.e. 2 dual 1 ohm), placed in a 220L enclosure (roughly a 40" x 22" tube) and given 3200W produces a system with Q=0.724 & excursion is capped at about 24mm. My current SP4 loses control at ~27mm (distortion passes 10% or -20dB here and escalates quickly) so if this holds true for the bigger driver, albeit in a completely different enclosure, then it seems to say I could get away with 2 18" if I relax my goal a little.

Attachment 116561

Attachment 116569

On the other hand, this is a system that is *just* getting there. I suppose I could always start with a single dual opposed tube and then add another, if need be, later. 3 such drivers seems to be exactly on target, are there any good cabinet designs that accommodate 3 drivers though?

@pdxrealtor I used your measured winisd model for the above, I think you said you had some tweaks to that driver or am I misremembering?
Apologies if I missed it earlier - what about 3 cabinets, one for each driver?

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post #22 of 54 Old 06-15-2014, 01:49 PM - Thread Starter
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Originally Posted by pdxrealtor View Post
Apologies if I missed it earlier - what about 3 cabinets, one for each driver?
I've been playing some more with WinISD after discovering what Ql and Qa are really for (as per this thread - Very low frequencies (WinISD vs. laser measurement)).

If I give each driver 100L (roughly 15" height of a 24" diameter tube) then 2x18 can deliver 118dB when fed with 6000W. Excursion is at 31-32mm though (xmax 33mm) under 20Hz.

If I add a 3rd driver and reduce power to 4000W then I get the same SPL but 20-21mm excursion.



This seems doable using D2 drivers & I could stick 2 in a dual opposed tube with an upgrade path of a 3rd driver in another, shorter, tube firing into the top plate of the dual. Does this seem sane/workable?

The main doubt I have here is the amp & power supply in general. I understand the speakerpower is good for 6kW for 4s into 2ohm down to at least 10Hz, I'm also told there is no need for more than a 13A feed in the UK (230V) though I can easily get a 32A line fitted if required. The numbers quoted by some earlier posters are rather larger though. What are the pitfalls here (that I am blissfully unaware of)?
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post #23 of 54 Old 06-15-2014, 02:54 PM
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I've yet to see what exactly is going on with my setup. IE are the speakers distorting due to past xmax, or because the amp is at its limits. Winisd tells me that 3750 watts / driver is too much and puts me past xmax @ ~ 21 hz. However it's anyone's guess what the IPR2 is actually putting out at 10-20 hz.

Are you going with SP amp(s)?

The biggest flaw I see in your design is two drivers in one cabinet. You can always build three cabs and stack them as dual opposed. If that works great, but if you need to separate them for FR smoothing you'll have that option.

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post #24 of 54 Old 06-15-2014, 03:36 PM - Thread Starter
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Originally Posted by pdxrealtor View Post
I've yet to see what exactly is going on with my setup. IE are the speakers distorting due to past xmax, or because the amp is at its limits. Winisd tells me that 3750 watts / driver is too much and puts me past xmax @ ~ 21 hz. However it's anyone's guess what the IPR2 is actually putting out at 10-20 hz.

Are you going with SP amp(s)?

The biggest flaw I see in your design is two drivers in one cabinet. You can always build three cabs and stack them as dual opposed. If that works great, but if you need to separate them for FR smoothing you'll have that option.
I don't really have the space to separate them, or at least the FR improvement from separating them into the available locations is not worth bothering about. Having said that, the extra flexibility is probably worth it anyway.

I am awaiting delivery of an SP amp (a single rack mount channel capable of 6kW into 2 ohm). It is overkill for what I have right now but quiet & efficient was paramount. Of course it was a small step from there to "what can I do to exploit that power?"

Have you changed that leakiness param in winisd? I see yours as just coming in under xmax with that set.



You clip with a +7dB shelf but don't without that shelf right? Since WOTW has serious signal strength all the way down then +7dB (~5x the power) seems quite a big ask so I suppose you just need to chill out a bit on the boost. Have you measured your actual room gain? if you do that & combine that with your near field measurements then you should be able to tailor your EQ to dovetail with the room gain perfectly rather than just adding a low shelf.
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post #25 of 54 Old 06-15-2014, 03:52 PM
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In a room that size I think any four sealed 18's (or larger) with decent excursion would get you there. Two might even, but with the different roll-offs at 5-10 hz you will probably need 4. The room gain in your room should be pretty nice, starting at around 42 hz, you should have +12 dB at 20 hz, +24 dB at 10 hz, and +36 dB at 5 hz. I assume your room isn't perfectly sealed so you will lose some room gain as these numbers only hold true for a perfect sealed room.

I agree with this post.

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I can't remember who asked about using more than 2 drivers in an enclosure, but, I have heard several different designs that used anywhere from 3 drivers up do 6 drivers in a single enclosure.

The enclosure with 6 drivers had two in the front, one above the other, and then some hexagonal, or octagonal (not sure of the proper term, it was shaped kind of like two Pentagons stack on top of each other, but, it was a single cabinet.) sides that were tall enough to use two drives in each side cavity on each side. The drivers were Dayton HO12's. That sub really put out an enormous amount of output and seemed to have excellent extension!

. He is actually building another one as we speak!
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post #27 of 54 Old 06-16-2014, 09:32 AM - Thread Starter
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I can't remember who asked about using more than 2 drivers in an enclosure, but, I have heard several different designs that used anywhere from 3 drivers up do 6 drivers in a single enclosure.

The enclosure with 6 drivers had two in the front, one above the other, and then some hexagonal, or octagonal (not sure of the proper term, it was shaped kind of like two Pentagons stack on top of each other, but, it was a single cabinet.) sides that were tall enough to use two drives in each side cavity on each side. The drivers were Dayton HO12's. That sub really put out an enormous amount of output and seemed to have excellent extension!

. He is actually building another one as we speak!
would be interested in a link if you can remember the build.

as far as I can see anything hexagonal is going to result in a footprint that is too big to fit in the space available unless I use more smaller drivers, i.e. pretty much build a sub2 clone, which I don't think will be cost effective.
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post #28 of 54 Old 06-16-2014, 09:59 AM
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I have seen sub towers built. There is a build that had 6 or 8 lms ultras in a tower that was quad oppose or triple opposed. Can't really remember what thread it was though.

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post #29 of 54 Old 06-16-2014, 12:12 PM
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Originally Posted by pdxrealtor View Post
I've yet to see what exactly is going on with my setup. IE are the speakers distorting due to past xmax, or because the amp is at its limits. Winisd tells me that 3750 watts / driver is too much and puts me past xmax @ ~ 21 hz. However it's anyone's guess what the IPR2 is actually putting out at 10-20 hz.

Are you going with SP amp(s)?

The biggest flaw I see in your design is two drivers in one cabinet. You can always build three cabs and stack them as dual opposed. If that works great, but if you need to separate them for FR smoothing you'll have that option.
I don't really have the space to separate them, or at least the FR improvement from separating them into the available locations is not worth bothering about. Having said that, the extra flexibility is probably worth it anyway.

I am awaiting delivery of an SP amp (a single rack mount channel capable of 6kW into 2 ohm). It is overkill for what I have right now but quiet & efficient was paramount. Of course it was a small step from there to "what can I do to exploit that power?"

Have you changed that leakiness param in winisd? I see yours as just coming in under xmax with that set.



You clip with a +7dB shelf but don't without that shelf right? Since WOTW has serious signal strength all the way down then +7dB (~5x the power) seems quite a big ask so I suppose you just need to chill out a bit on the boost. Have you measured your actual room gain? if you do that & combine that with your near field measurements then you should be able to tailor your EQ to dovetail with the room gain perfectly rather than just adding a low shelf.

Nice amp choice!

I recently read about changing the leakage parameters, but never could figure out how until you posted that screen shot. Thanks, I changed it. I'm still a bit above xmax with no boost using a 4^3 box and 3750 watts of power per driver.

I am just barely tickling the clip lights in only the hottest of scenes with my 5DB shelf frm 45 hz back, then I also have 7DB of boost @ 15 hz with a Q of 4. I'm flat with or with out the shelf filter.

On some material the low shelf sounds great, and on others it sounds to boomy/muddy. Then of course on a few it shuts the amp down. I don't know if the boomy and muddy sound I am hearing is the amp at it's limits or the speaker at its limits.

I don't know how to measure room gain. I know have a good amount. I will probably end up using a low shelf as is for normal listening (-5 on back) and either eliminating or toning it down for reference level listening - demos.

Lots to play with, lots of listening to do.

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post #30 of 54 Old 06-17-2014, 09:30 AM - Thread Starter
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I don't know how to measure room gain.
all I've done so far is noted that my in room response has a section that has a 12dB/octave rolloff in a frequency range where the close mic measurement is also rolling off at that rate (25-35Hz ish). This suggests there is no (or at least constant) room gain here so I can overlay the 2 measurements, level matching in that area, and then measure the diff between the 2 to get the room gain. Obviously this only works for my room and might be wrong in absolute terms. I don't know another way to do this without taking it outside first though.
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