Enclosure help for Epic 12 - Page 2 - AVS Forum
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post #31 of 51 Old 04-25-2012, 10:29 PM
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But the sub you spec'd is at 13.8 m/s (20hz HPF 500W) with no round over, and "rectangular/slot ports will be worse" lol
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post #32 of 51 Old 04-25-2012, 10:30 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"Now everyones making me scared, lol."

go back up to post #6. ignore the rest. :-)

"Ive emailed thilo at tc sounds, Ill let you know what I find out."

no need to waste his time with something as simple as a ported cabinet for your driver. this really isn't a complicated project.

Just appears that everyone wants to make it as complicated as possible though. Im a newbie, and getting told this then that.

I really appreciate all the help, but the contradicting posts arnt really being that helpful.

If one could explain exactly the differences, Id be less confused.
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post #33 of 51 Old 04-25-2012, 10:43 PM
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Yes someone does keep trying to over complicate things, almost like they have an issue with someone else

Anyway, this note with those test results shows why the general rule of thumb has always been to shoot for about 17 m/s

Quote:


The main area of subjectivity is in deciding how to translate results based on barely audible chuffing, into recommendations for typical music and home theater applications.
A test was done to see how much the port velocity could be increased before the "chuffing" became audible at the seating position.
For a seat 2.5 metres from the sub in a room 5m * 4m, the velocity could be increased by 25%.

An allowance for the masking effect of content can also be used.
The actual amount is based on the performance of sub's I've built, and on existing industry recommendations.
I estimate that reasonable values for masking allowance are an additional 15% for music and 30% for Home Theatre usage.
The equations developed below are based on designing for music, so a total allowance of 25+15 = 40% is used

That's a 55% increase allowed in velocity for HT
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post #34 of 51 Old 04-25-2012, 11:01 PM
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"If one could explain exactly the differences, Id be less confused."

:-)

you asked for a front firing, front ported enclosure and set some dimensions and indicated a driver.

a design was presented in post 6 based on software that most anybody can take a look at and most folks would agree that it is a decent design. there are other possibilities, but what was presented fits your criteria. jay and i were on the same page with respect to the basic design.

jay and i got into a pissing contest about the diameter of the slot port and that is where the thread went off the tracks. i said 2.0". he said 1.5". the bottom line is if you choose 1.5", it will work. it just won't be quite as good as the 2.0" version because port chuffing will come on at a lower spl. if you don't make a roundover on the port, it will work. if you can make a roundover, it will work a little better.

no biggy.

Listen. It's All Good.
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post #35 of 51 Old 04-25-2012, 11:13 PM - Thread Starter
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Well thanks LT, so the larger port will induce less noise, but Ill have to factor in the bracing to have a slightly higher tune??

Am I getting that right?
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post #36 of 51 Old 04-25-2012, 11:27 PM
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the larger port will have to be longer in order to tune the cabinet to your target frequency.

once you choose what you want to do, lots of folks can calculate the length that your port must be in order to tune your cab as you wish.

Listen. It's All Good.
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post #37 of 51 Old 04-26-2012, 04:33 PM - Thread Starter
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Well I just found a thread in a search, but the op didnt state his outcome or any pics. But it involved the same driver Im getting, in a sealed enclosure with the o audio 500 watt plate amp.

I have the winisd beta, but it dosnt seem to graph out the same types of graphs you guys are posting. How is this combination, with say a 1.6 cubic foot enclosure with the high pass on the amp set to 25hz?
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post #38 of 51 Old 04-26-2012, 06:17 PM
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Hi Jim!

I couldn't resist joining up and throwing in my 2 cents.

Sounds like you've found another approach to the design here with some input from this fine forum

The approach being discussed here, is traditional vented but with ultra low tuning, which moves the peak air velocity of the system down below your intended passband. There is nothing wrong with that, though doing so is a sacrifice to maximum SPL and distortion levels for a given drive level. Originally we discussed 25hz extension, putting the priority on music over movies.

[for others here, I'm the goofball that came up with the transmission line idea that Jim posted in post #21 here]

The TL is a more complicated build, but has a few benefits over the "under-tuned" vented design being considered [compared to suggestion in post #6].
  • ~3dB better efficiency through the desired passband. (previously discussed as ~25-80hz)
  • 100% linearity at over 500W, The vented system looses linearity above ~350W.
  • 70% BL Xmax occurs at ~600W in the vented, over 1000W in the TL.
  • Peak air velocity at 500W is only ~6m/s.

The result of all that, is about an average 5-6dB better dynamic reach on paper, and reduced distortion for equal listening levels within the desired passband.

Whether or not that is worth the added build complication and the sacrifice of <25hz loading is up to you...


If you do want to go with a simpler ultra-low-tuned vented design, I would consider around 70 liters of chamber space (after losses to bracing and driver displacement) and a slot vent of 2"x15.5" x ~70" long (folded to fit). [see attachments for simulation @500W]... taking some time to simply sand or grind some smooth transitions around the bends and at the port opening would kill some of that peak in air velocity and more or less kill most if not all port noise...

Regards,
Eric
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post #39 of 51 Old 04-26-2012, 07:08 PM - Thread Starter
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Cheers Eric, and by no means are you a goofball. I really respect all the work you have done to get the best from driver choice. Its just a rather complicated design for a first timer.

The way I see it, I can build it, if I dont like it I can build it again. So starting with the easier design, would net me experience, to further go along if I finally go with your desigm.

By the simulation you posted, that is what I would like, but Im endeavouring simple designs to get me started.
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post #40 of 51 Old 04-26-2012, 07:23 PM
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Quote:
Originally Posted by vwgti View Post

Well I just found a thread in a search, but the op didnt state his outcome or any pics. But it involved the same driver Im getting, in a sealed enclosure with the o audio 500 watt plate amp.

I have the winisd beta, but it dosnt seem to graph out the same types of graphs you guys are posting. How is this combination, with say a 1.6 cubic foot enclosure with the high pass on the amp set to 25hz?

This is what you would get from that sub. There's 3.5db boost with the 25hz filter, shown with 225 watts.
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post #41 of 51 Old 04-26-2012, 07:44 PM - Thread Starter
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Thanks Jay, why does ur graph show a q of 1.42, but my winisd beta shows a q of .63??

As far as I know the lower q the better musicality, down to about .5.
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post #42 of 51 Old 04-26-2012, 07:57 PM
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Quote:
Originally Posted by vwgti View Post

Thanks Jay, why does ur graph show a q of 1.42, but my winisd beta shows a q of .63??

As far as I know the lower q the better musicality, down to about .5.

That shows the 25hz filter frequency and Q. One of the posts in my sub build thread has a link to another thread with all the O Audio amp info. I cant understand why O Audio doesnt include this info with the sub manual...
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post #43 of 51 Old 04-26-2012, 08:05 PM - Thread Starter
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Huh, haha, thought sealed might of been easier. But since you have the awesome software I dont, what size sealed enclosure should I go with for that 25hz filter?? Or would a lower filter be preferred?
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post #44 of 51 Old 04-26-2012, 08:23 PM
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Hi Jim,

If you go sealed, you don't really need to worry about a high pass filter. At 500W in a 2ft^3 box, simulation predicts peak displacement around 25mm well down in the subsonic (~10hz and below), which is fine, the real world displacement would be less because beyond ~18mm the driver is no longer linear, and the suspension, as I recall, is rated for 2" P-P excursion (25.4mm one-way)). I think a sealed box anywhere from 1.5 - 3.0 ft^3 is going to be just fine. Personally, I would not use one of those "plate" amps for the sealed box build unless you build the box with a separate cavity for the amp. I'd just stick to the original plan to use the Crown XLS as the sub amp. Having 1000W when you really only "need" 500W is actually a blessing.. it's called clean headroom and is worth having IMO... Especially considering the price is about the same either way.

Regards,
Eric
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post #45 of 51 Old 04-26-2012, 08:26 PM
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Quote:
Originally Posted by vwgti View Post

Huh, haha, thought sealed might of been easier. But since you have the awesome software I dont, what size sealed enclosure should I go with for that 25hz filter?? Or would a lower filter be preferred?

All you have to do is add a highpass filter, and change the subtype to "SOS user specified Fc and Q", then change the cutoff and Q to what the filter shows

Quote:


Switch Setting - 12Hz; C1, C2 = 1.00uF
R8 = 1.96 kOhms
R12 = 154.00 kOhms
Filter Fc = 9.16Hz
Filter Q = 4.43
Fc dB = 12.93dB
dB Boost = ~14dB

Switch Setting - 16Hz; C1, C2 = 1.00uF
R7 = 2.55 kOhms
R11 = 59.00 kOhms
Filter Fc = 12.98Hz
Filter Q = 2.41
Fc dB = 7.62dB
dB Boost = ~10dB

Switch Setting - 20Hz; C1, C2 = 1.00uF
R6 = 2.67 kOhms
R10 = 31.60 kOhms
Filter Fc = 17.33Hz
Filter Q = 1.72
Fc dB = 4.71dB
dB Boost = ~6dB

Switch Setting - 25Hz; C1, C2 = 1.00uF
R5 = 2.43 kOhms
R9 = 19.60 kOhms
Filter Fc = 23.06Hz
Filter Q = 1.42
Fc dB = 3.05dB
dB Boost = ~4dB

Plug in the filter Fc and Filter Q numbers into that highpass filter and it will show you the response (the boost numbers shown arent 100% accurate).
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post #46 of 51 Old 04-26-2012, 08:36 PM - Thread Starter
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Pics attached, Im confused where to put it.
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post #47 of 51 Old 04-26-2012, 09:01 PM
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those pics are to small to see
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post #48 of 51 Old 04-26-2012, 09:05 PM - Thread Starter
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Well I have a choice of active or passive, passive gives me high pass 1st or 2nd order, active gives me 2 way 1st 2nd and lpad.
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post #49 of 51 Old 04-26-2012, 09:16 PM
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what version of win isd are you running? get the new one

https://www.facebook.com/WinISD
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post #50 of 51 Old 04-26-2012, 09:39 PM
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hi mdo,

could you post the hornresp model that you are talking about? the one posted earlier was too small to see.

Listen. It's All Good.
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post #51 of 51 Old 04-26-2012, 10:16 PM
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Hi LTD02

Lets see if this works....

These are simulated at 500W:

Regards,
Eric
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