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Dimensions for sealed 18" sub box - Page 14

post #391 of 679
Quote:
Originally Posted by Erich H View Post

If anyone happens to have one near Cincinnati, they could drop it off for me to double check the cut out diameters.
I picked up some Baltic birch subwoofer enclosures on Saturday. Double baffles with the outer baffle being mdf so that the roundovers are smoother and they could be painted easier if needed. The ones I got on Saturday were smaller boxes.

I should be making an IKEA run this weekend to West Chester if you want me to swing a 12 spoke basket by (Fi built). Shoot me a pm we can work out the details
post #392 of 679
Any info on whether or not there's going to be a box in the 2.5-2.75 ft^3 range?
post #393 of 679
at that point, you are going past the point of driver protection and just making the enclosure inefficient.

in cars where you get a whole boatload of pressure vessel gain, very small sealed subs can be okay.

in a home theater/home media room, you just end up needing twice the amp in the smaller enclosures which raises the price of the system quite a bit.

the 18-ho is 107db at 20hz in model in 4 cubic feet.

the 18-ho is 103db at 20hz in model in 2 cubic feet.

that is 3-4 times the power (figuring in a hair of compression) for the same output.

not recommended.
post #394 of 679
Hey LTD02.

The Dayton 18" HO in 4.5cuft is limited to about 300 watts if Dayton/Eminence's claims of 12.8mm xmax are to be followed. I would rather shrink that box since watts are cheap nowadays to allow for more power handling. You can go as low as a 2.5cuft box for a single driver and with advanced DSP nowadays like the MiniDSP or Audyssey you don't have to worry about the box Q before these awesome inventions.
post #395 of 679
Quote:
Originally Posted by LTD02 View Post

not recommended.

But not always avoidable I'm afraid. Aesthetics, placement considerations -- and various other factors -- often dictate enclosure size. That's the case here. FWIW... I was actually looking at the 15", not the 18". 2.5 ft^3 does seem a little constrained for an 18" driver, unless it's the Cap S1 of course...
post #396 of 679
"The Dayton 18" HO in 4.5cuft is limited to about 300 watts if Dayton/Eminence's claims of 12.8mm xmax are to be followed."

ricci just measured them to at least 20mm. 4 cubic feet at 1000 watts takes them to 20mm excursion at 10hz. i was edging on the conservative side and knocked it down 1/2 a cubic foot.
post #397 of 679
"Aesthetics, placement considerations -- and various other factors -- often dictate enclosure size."

agree. i was just saying that for the same performance in the tiny enclosure, you'd need twice the amp or more. if that is a good tradeoff in your system, cool.
post #398 of 679
Quote:
Originally Posted by LTD02 View Post

"The Dayton 18" HO in 4.5cuft is limited to about 300 watts if Dayton/Eminence's claims of 12.8mm xmax are to be followed."
ricci just measured them to at least 20mm. 4 cubic feet at 1000 watts takes them to 20mm excursion at 10hz. i was edging on the conservative side and knocked it down 1/2 a cubic foot.

With cheap watts and DSP nowadays I like a smaller box so you can turn up the volume down low with an LT/shelf filter for sealed boxes which is essential for good performance. The added travel is gravy but unless I am wrong isn't xmax were the driver begins to reach about 10% THD or the bl begins to fall off? Of course there can be added travel but you don't always want to model to that point as that is when distortion begins to rear it's ugly head.

From personal experience I have always had better performance from a smaller box than a larger trying to get to that magical .7 enclosure Q range which is just not needed in the age of cheap watts and DSP. Even Ricci's enclosure Q is going to be up there with his 9 cuft dual opposed XXX 18" which is normally the size for a single XXX 18" in sims.

Personally I think 3cuft would be a better all around size for the 18" HO and if you had enough power and DSP knowledge you can go a little smaller. You get more natural low end from a bigger box but you lose out on power handling which is needed for a boost down low for sealed designs.
post #399 of 679
"You get more natural low end from a bigger box but you lose out on power handling which is needed for a boost down low for sealed designs."

yeah that is kind of the myth that i was talking about. it isn't so much that tiny sealed subs have twice the power handling as they are half as efficient so they require twice the power for the same performance.
post #400 of 679
Quote:
Originally Posted by LTD02 View Post

"You get more natural low end from a bigger box but you lose out on power handling which is needed for a boost down low for sealed designs."
yeah that is kind of the myth that i was talking about. it isn't so much that tiny sealed subs have twice the power handling as they are half as efficient so they require twice the power for the same performance.

Myth, really? When you can get close to 2000 watts from the EP4000 bridged in the $300 range it's not like trying to catch a unicorn wink.gif
post #401 of 679
"Myth, really? When you can get close to 2000 watts from the EP4000 bridged in the $300 range it's not like trying to catch a unicorn"

not sure about the unicorn reference, but yeah, that is what i was talking about.

if it takes twice the power to reach the same spl, then the system can be said be 1/2 as efficient.

instead of being able to "take twice the power", a better statement might be that it "requires" twice the power for the same spl down low.
Edited by LTD02 - 11/6/12 at 12:05am
post #402 of 679
I have built multiple boxes for the same driver but feel that the advantages of a smaller box with the availability of cheap watts and DSP should be taken advantage of now, I guess you disagree. Your point is true but is not necessary as it was in the past when big amps were too expensive and DSP was not readily available to the DIY'er.

There really is no reason to argue the point with you anymore, I have read enough posts between you and Bosso to know this is going nowhere.
post #403 of 679
So would the Dayton 18" HO in a 4-4.5 cu ft box and a 500w bash amp be sufficient? Or would I need more than 500w (I already have a 500w bash amp sitting doing nothing).
post #404 of 679
Xmech on this driver is 32.25mm. Useful excursion is about 20mm. Geometric xmax is 12.75mm.

In a 4.2 cubic foot sealed enclosure this driver will take all of a 1400w amp channel without issue. Put it in 3 to 4.5 cubes sealed and give it 1000-1500w of amp. EQ to taste. Done.

One thing that is often missed with very small sealed boxes is that your excursion peak ends up being not at 5Hz or 10Hz or anywhere in the low bass and instead ends up being much higher in frequency depending on the particular sub. This despite what models might say about the excursion. They do not include the driver behavior and non linearity inherent at 2.5" peak to peak excursion. So while your driver may be safe in the deep bass it may not be at the excursion peak which could be at 20Hz or even 25Hz.
post #405 of 679
Thread Starter 
Quote:
Originally Posted by mastermaybe View Post

I've done quite a bit of woodworking and I'm pretty confident with what follows:
13ply 3/4" baltic birch is 2.5lbs per square foot.
3/4" MDF is ~3.125lbs per square foot.
Call it 20%.
Whether it's significant or not is of course subjective, but it surely makes a difference on large cabinets.
My current cabinet was 55 lbs in BB, it would have been about 66 in mdf.
and "B" should be perfectly fine for 95+% of the builds, here.
Again, I agree wholeheartedly with the move.
James


Believe it or not, there really is no weight difference between mdf and Baltic birch.

Today I picked up some Baltic 15.25" subwoofer flat packs and compared them with the mdf 15" flat packs I already have. The Baltic was .25" bigger, but the hole cutout was for a 12" and the mdf cutout was for a 10" woofer. So pretty close the same material. I was surprised to see that they were both exactly the same at 27.2 lbs. I weighed them both twice because the mdf box ticked up to 27.4lbs, then back to 27.2lbs. I think the scale goes to the nearest whole number, so the mdf box must be right around 27.3lbs.


I was actually hoping that it would be less for shipping and didn't expect them to be nearly identical in weight. I knew they were close, but not that close. There's a nice domestic birch plywood that is suppose to be lighter and very good quality. I'll try that stuff next.
post #406 of 679
Quote:
Originally Posted by Ricci View Post

Xmech on this driver is 32.25mm. Useful excursion is about 20mm. Geometric xmax is 12.75mm.
In a 4.2 cubic foot sealed enclosure this driver will take all of a 1400w amp channel without issue. Put it in 3 to 4.5 cubes sealed and give it 1000-1500w of amp. EQ to taste. Done.

X100000!

Erich - From the sounds of it, this is going to be a very popular combo! I'm going to order a handful of these soon and I'd be happy to be a test bunny,.
post #407 of 679
Quote:
Originally Posted by Ricci View Post

Xmech on this driver is 32.25mm. Useful excursion is about 20mm. Geometric xmax is 12.75mm.
In a 4.2 cubic foot sealed enclosure this driver will take all of a 1400w amp channel without issue. Put it in 3 to 4.5 cubes sealed and give it 1000-1500w of amp. EQ to taste. Done.
One thing that is often missed with very small sealed boxes is that your excursion peak ends up being not at 5Hz or 10Hz or anywhere in the low bass and instead ends up being much higher in frequency depending on the particular sub. This despite what models might say about the excursion. They do not include the driver behavior and non linearity inherent at 2.5" peak to peak excursion. So while your driver may be safe in the deep bass it may not be at the excursion peak which could be at 20Hz or even 25Hz.

Hey, Josh. When I use the T/S numbers you derived from the 18HO in Unibox and plot out for a 4.2cuft sealed box with 1,400w I get this:

DaytonHO18Ricci4cuft1400wXmax.gif

Seems like one would get pretty close to Xmech with that much power. Did I mess something up? Does this seem reasonable? To me it seems like it would be a good idea to skip out on 1dB ~10hz and use a 3.5cuft cab with that much power.
Edited by Scott Simonian - 11/6/12 at 3:00pm
post #408 of 679
I was seeing the same things Scott, this is why I was lobbying for a smaller flat pack. I also thought a smaller flat pack would allow for lower costs so 3 to 3.5cuft would make more sense.
post #409 of 679
The sweet spot seems to be between three and four cubic feet, imo. I wouldn't go any smaller for home use personally. 3cuft sounds good but it really depends on how one plans to power them. I've pondered a cheap multi-driver system for a rear subwoofer in my room with these drivers powered by a single ep4000 which gives roughly 400w per driver. In that case I could easily go with 4cuft or more with no worries. If someone wants to put +1,000w into each driver... no more than 4cuft, for sure.
post #410 of 679
"Xmech on this driver is 32.25mm. Useful excursion is about 20mm. Geometric xmax is 12.75mm."

holy crap. that is a nice fat margin of error for safety. great data josh.

scott, like ricci mentioned, once you start moving the driver in and out of the enclosure 30mm, it is going to start to run into things like significant air spring effects, significant bl rolloff, etc.

the thiele small numbers are for "small signals". all kinds of other schlock occurs when "large signal" are run through a driver. it is how a driver responds to large signals that is one of the principal reasons for klippel analysis.
post #411 of 679
That's true. I guess I model in the direction of some safety. Don't mean to come off like a know-it-all but I know better but not everyone will. Don't need people destroying their drivers ala recent LMS-U builds. wink.giftongue.gif
post #412 of 679
Quote:
Originally Posted by Gorilla83 View Post

Erich - From the sounds of it, this is going to be a very popular combo! I'm going to order a handful of these soon and I'd be happy to be a test bunny,.

'test bunny' or 'dead duck'? Your wife is gonna string you up someday! tongue.gif What on earth do you need more subwoofers for? Dual Caps not enough any more?
post #413 of 679
Quote:
Originally Posted by JimWilson View Post

'test bunny' or 'dead duck'? Your wife is gonna string you up someday! tongue.gif What on earth do you need more subwoofers for? Dual Caps not enough any more?

See my thread in this section. biggrin.gif
post #414 of 679
"Don't mean to come off like a know-it-all but I know better but not everyone will. Don't need people destroying their drivers ala recent LMS-U builds."

+1.
post #415 of 679
Quote:
Originally Posted by Gorilla83 View Post

See my thread in this section. biggrin.gif

Do my eyes deceive me? You're moving the Caps out of the basement HT??? You'll be labeled a heretic/turncoat/pagan/defector by Archaea! tongue.gif

Guess that means your wife hates every last one of us for planting this seed in your mind, eh? I suppose no more GTG's at your house now... wink.gif
post #416 of 679
Quote:
Originally Posted by LTD02 View Post

scott, like ricci mentioned, once you start moving the driver in and out of the enclosure 30mm, it is going to start to run into things like significant air spring effects, significant bl rolloff, etc.
the thiele small numbers are for "small signals". all kinds of other schlock occurs when "large signal" are run through a driver. it is how a driver responds to large signals that is one of the principal reasons for klippel analysis.

Winner winner chicken dinner.
post #417 of 679
Quote:
Originally Posted by JimWilson View Post

Do my eyes deceive me? You're moving the Caps out of the basement HT??? You'll be labeled a heretic/turncoat/pagan/defector by Archaea! tongue.gif
Guess that means your wife hates every last one of us for planting this seed in your mind, eh? I suppose no more GTG's at your house now... wink.gif

Let's just say I'm doing some experimenting. Archaea is aware I'm getting the urge to try some new things, although he might not be too pleased. tongue.gif

So far my wife hasn't really complained...might as well schedule the next event now before it's too late?
post #418 of 679
Quote:
Originally Posted by Gorilla83 View Post

So far my wife hasn't really complained...might as well schedule the next event now before it's too late?

Might not be a bad idea. At least this way we can all get a chance to see your 'experiments' before she changes her mind... smile.gif
post #419 of 679
Quote:
Originally Posted by Erich H View Post

Believe it or not, there really is no weight difference between mdf and Baltic birch.
Today I picked up some Baltic 15.25" subwoofer flat packs and compared them with the mdf 15" flat packs I already have. The Baltic was .25" bigger, but the hole cutout was for a 12" and the mdf cutout was for a 10" woofer. So pretty close the same material. I was surprised to see that they were both exactly the same at 27.2 lbs. I weighed them both twice because the mdf box ticked up to 27.4lbs, then back to 27.2lbs. I think the scale goes to the nearest whole number, so the mdf box must be right around 27.3lbs.
I was actually hoping that it would be less for shipping and didn't expect them to be nearly identical in weight. I knew they were close, but not that close. There's a nice domestic birch plywood that is suppose to be lighter and very good quality. I'll try that stuff next.

They are not the same (weight) but I'm not going to drag this out anymore...I cannot speak precisely for the plywood you're using though because I haven't seen it.

Every 4x8 3/4" sheet of TRUE BB I've ever handled/used hasn't weighed more than 85lbs (most are around 82)...it varies a bit on the type and amount of adhesive used, but certainly no more than a few pounds, tops. Yes I have a scale in my shop and can easily weigh them.

That said, virtually every sheet of 3/4" MDF on earth weighs at LEAST 94lbs with many nearing 100lbs depending upon species/adhesives utilized- with more and more poplar thrown into the mix, that has added a few more pounds per sheet.

Check here: http://www.wolstenholme.com/pdf/Baltic%20Birch%20Plywood%20Specifications.pdf

Check the MSDS' on either product.

Pick up a 4x8 sheet of either.

They do not possess the same mass.

But thanks again for all of the work you're doing.


James
post #420 of 679
Quote:
Originally Posted by Scott Simonian View Post

Hey, Josh. When I use the T/S numbers you derived from the 18HO in Unibox and plot out for a 4.2cuft sealed box with 1,400w I get this:
DaytonHO18Ricci4cuft1400wXmax.gif
Seems like one would get pretty close to Xmech with that much power. Did I mess something up? Does this seem reasonable? To me it seems like it would be a good idea to skip out on 1dB ~10hz and use a 3.5cuft cab with that much power.

Correct...If you are using more power move towards the smaller box, if using less power move towards the larger box.
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