Triple driver - sealed. Pros/cons, and is it too much for a newbie - Page 3 - diyAudio
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Old 11th November 2012, 09:13 PM   #21
tb46 is offline tb46  United States
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Hi MedPed,

I hoped you'd find the LTC references interesting, and yes to the "modern" approach using the miniDSP, or the iNUKE: Behringer iNUKE NU6000DSP | Musician's Friend

I'll attach what is basically a concept drawing for a dual 12" driver sealed box.

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File Type: pdf GTO1214_Dual_Sealed.pdf (12.7 KB, 34 views)
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Old 11th November 2012, 10:10 PM   #22
MedPed is offline MedPed  United States
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Looked up the inuke. Seems that they do not publish 2ohm numbers for bridged mode, only in stereo. Were you guys suggesting running it in stereo, or bridge it, and take my chances it can handle it? If there is data that the power output increased substantially down to 2 ohms (in bridged mode), then it seems that would be worth it. If the output remains the same - then would it be safer to simply run either in stereo, or with dual amps rather than bridged and run the drivers in parallel.
As another option, would it be pointless and needlessly wasteful to use 4 drivers, with a pair of two drivers in series parallel two another pair in series pair. Would that make the impedance safer to run.

Regarding the 15" dual opposed suggestion, the epics only come in 12. The LMS-R are $433 for the 15". If there is a consensus that there are well worth the money, then I'll dish out. If they are only marginally better than comparative 15" drivers which might be less damaging to the wallet, then I would of course love to consider it.

@tb46, how do you churn out drawings like that? That's awesome. Personally, I was thinking of two outward facing drivers - same concept as the Paradigm/Martin Logan subs. What are the pros/cons of doing it the way your drawing suggests vs horizontally opposed. Also, is there any value in mechanically coupling/bracing the rear of the magnets together for further stability (like the Hyperion Sound HPS-738 HPS-738).

Correct me if I am wrong, but intuitively, compared to the suggestion in the GTO1214 drawing, it seems that the horizontally opposed will get more output, (but harder to drive than single driver due to relative decrease compliance of the air in cabinet as the drivers work against each other within the cabinet space), whereas, the one in the GTO1214 drawing will likely be cleaner - the drivers helping each other but requiring dual amplification for almost negligible increase in output. Forgive my ignorance, but is the drawing what is referred to as a push pull design, or is that something else altogether?

I hope my curiosity is not misconstrued for criticism, I am new to this, and want to try and understand your suggestions. I have shadowed other threads, but have been apprehensive to hijack their threads with my stupid questions, and feeling bad about bombarding you guys with questions.

Thanks.
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Old 11th November 2012, 10:40 PM   #23
MedPed is offline MedPed  United States
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What is the optimal crossover point, where the sub cannot be localized. One of my monitors starts dwindling at 60Hz, and the other at 40Hz. I am assuming if I crossover higher, I can offload my L/R speakers/amps. Depending on what you read people suggest anywhere from 60-120 Hz. I don't have flood standers - only bookshelf monitors.
PSB B25s, and Emotiva Pro Airmotiv 6. My current sub is a PSB 5i. The Airmotivs are powered speakers - 200W/ch, the B25s are powered by a NAD receiver at 50W/ch - not too much power, but clean.
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Old 11th November 2012, 11:38 PM   #24
tb46 is offline tb46  United States
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Hi MedPed,

Let's call the drawing in Post #21 a conceptual sketch because, that's what it is. I'd call the arrangement Push_Pull, with the drivers wired out of phase (as they are mounted physically out of phase). There should be some distortion cancellation, and the vibration of the cabinet should be reduced. More bracing and maybe 1" dowels from driver baffle to driver baffle would be helpful. The output SPL should be the same as for two forward radiating drivers mounted normally. Instead of going to 15" subs I would tend to recommend multiple 12" subs (But I keep on changing my mind about this. For example did you see the thread on the new RSS460HO: New HT subwoofer. Dayton Ref 18" ).

You should not be able to localize a sub if it is crossed over below ~~120Hz. It's easy to localize wheezing boxes and magnet port noises though :-).

I don't have any practical experience with the iNUKE amplifiers, but would generally warn against running close to the minimum recommended load impedance, even in a closed box, with any amplifer.

Most importantly, define your requirements as to actually needed SPL and frequency range.

Regards,
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Last edited by tb46; 11th November 2012 at 11:41 PM.
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Old 11th November 2012, 11:39 PM   #25
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Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
60 Hz seems to be the point where the sub "gets started" rolling in as the mains start falling off.
This mechanical coupling smacks of snake oil to me.....I can see the reinforcement of large resonant panels to change the frequency. This being the case how much tension......or compression are you going to apply???
Perhaps it has been researched to death....but I would think not...Lots of variables here. The opposed drivers does seem to make sense & your not "hurting" by applying such an approach if your going with dual drivers...the only drawback being an increase in volume for the pair.
Just thinking out loud.


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Old 12th November 2012, 02:33 AM   #26
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Again, we have to return to what sort of performance specs are set as the goal, and also the size of the room. Otherwise all this is just speculation and generalization, imo.

The goal of "vibration" cancellation is all well and good, as long as all the other aspects of the design and system integration are pretty well optimized. So, I'd counsel to focus on this first before getting too fine an edge on the vibration cancellation issue.

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Old 12th November 2012, 02:34 AM   #27
MedPed is offline MedPed  United States
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Difficult to quantify SPLs in terms of decibels, as I don't have a reference point. But to draw parallels, I do like to listen to music loud, and would love to get solid oomph in the movies. The main room it will be heard in is approximately 16x20 with 9 foot ceilings. The more I read , the more it makes sense to crossover at 80 Hz unless using the smallest speakers. Unless you guys have other advice.

I would like to reach below 20 Hz, maybe upto 15. I can't say I have much experience with subs that go deeper, so I don't know if I am missing anything below 15. Hopefully not much. I am not worried about neighbors, as the room it will be heard in faces my yard, and the closest neighbor on that side is across the street.

The sub will be used in a room open to the living/kitchen about 2-3/year for parties etc. those few times, it will be for music only, so output will trump the need to go below 20Hz.

Does that help?

What SPLs should I be shooting for?
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Old 12th November 2012, 02:43 AM   #28
MedPed is offline MedPed  United States
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As far as taste in music, I listen to jazz, blues, classic rock, classical, and my kids listen to contemporary pop and dance. Essentially covering all genres. Doesn't help does it.
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Old 12th November 2012, 04:13 AM   #29
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Odd.........That Behringer amp consumes only 620 Watts off the wall outlet but outputs 3000 Watts into a 4 Ohm load per channel(2)..... Where did it find all that extra power?

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Last edited by Richard Ellis; 12th November 2012 at 04:13 AM. Reason: typo
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Old 12th November 2012, 06:08 AM   #30
tinitus is offline tinitus  Europe
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