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Discussion Starter · #1 ·
Lets say you were building a theater but you didn't have a lot of construction skills or all the fancy modeling software and whatnot...


What could be achieved with a best guess approach with around 4-8 very high quality drivers positioned around the room (lets say 4 in the front of a room and 4 in the back).


for the sake of the discussion, lets do 22'x19'x13' dimensions (around 5400 cu ft).


What drivers would you guys use and would you go for an infinite baffle? We will assume that any peaks are tamed by EQ. Nulls can be tamed by sheer number of subs which allows adjustment of the main listening position. Lets presume good performance in the 10hz to 60hz range...


Is my discussion pure insanity or would arbitrarily just mounting drivers here and there (guessing) result in reasonable bass response? I would be willing to compensate for complex enclosures with simply using more drivers if this would help in some way...
 

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There would be no point in just adding random drivers at random areas around a 5400cu/ft room because of the fact that it is so cheap to do measurements! You can purchase a UMM-6 for around $75, and then download REW, and start measuring!
 

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Discussion Starter · #5 ·
Can you measure the sub response without actually fully mounting it in a box in the wall? There are finite places i can put these subs.


I could easily do 2-3 drivers per bay which is 72" high, 22" wide, and about 9"max depth. It's really my depth that is the constraint.


The 4 spaces I have are midway up a 12ft wall and in the 4 corners of the room.


I just dont know how to "measure" it without actually putting them in and checking the results.


I want to max out driver size and number so this is a one-time adventure. i will make custom boxes and build them into the space with 3/4" MDF or other hard wood.


I think sealed with 3 drivers each bay for a total of 12 drivers seems very doable. The drivers will almost form a mini-array in each corner, especially if I go to 16 drivers...


The boxes would each have about 5-6cuft of space and sealed. Not sure how that would turn out.


Unfortunately the only things I can "choose" are driver type/brand.


If all this goes well I want to sell my pair of JL AUDIO F212 subs. JL audio drivers looks really pricey and I'm thinking are overkill when I will have like 12-16 drivers in the room.
 

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The T/S parameters can be used to simulate a "theoretical" response.
 

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I see... I didn't realize in-wall was a restriction.


If you've got four locations for 6cuft enclosures, you're going to need sealed designs to keep volume down. (As well as for the deep extension.)


I'd say you want eight drivers that are good in 3cuft each, like the ultimax 15s. And plenty of power.


I'm building 4 3cuft boxes with UM-22 15s for use in four corners of my 3200cuft room, and it should be good for reference down to 20hz or below, depending on room gain. Eight should get you pretty close, and squeezing more drivers into the same enclosure volume won't help.
 

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Discussion Starter · #8 ·
Great thanks, i figured too many drivers may not add much since they will be fighting the same vacuum in the box...


Any role for a passive radiator?


What about sound qubed products?
 

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9" depth is going to be a problem...Are you going to build a enclosure in the bay? If so, that will decrease the depth too.

 

Dayton 18 HO = 9" depth

Dayton 15 Ultimax = 8" depth

Dayton 15 HF = 7" depth

 

Dayton 12 Ultimax = 6.22" depth, this can work well in a large ported enclosure.
 

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Discussion Starter · #10 ·
Yes i think i definitely need an enclosure in the bay. I may be able to build the enclosure into an odd shape to go deeper a few inches.


Are shallow drivers a really bad thing for performance?
 

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It's not that shallow drivers are bad performers, per se, it's just that most 15" and especially 18" drivers are not that shallow, and unfortunately, if you want shallow subs, you are stuck with 12" and 10" drivers.


Are you definitely opposed to having the enclosures out in the room? Are you stuck with having only in-wall enclosures?


You could do some nice looking end table subs, make them really pretty and I am sure no one would know that those end tables are actually subwoofers. For that matter, you can build all kinds of nice subwoofer enclosures disguised as furniture! I am sure some of us could help with the design ideas, and you could likely end up with a room full of nice 18" subs and no one would have a clue they are there! If you did eight of the Dayton HO18's or perhaps four of the UXL-18's then those would likely give quite the upgrade in performance compared to the JL-Audio F212!
 

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Discussion Starter · #12 ·
In wall is a major option because the wiring and other stuff is designed already in the room for it. Its not a regular wall, its actually a cavitity that is built up with woodwork and stuff already.


Theoretically i could also do a near field sub behind my couch as some kind of console table but it would only look good if it was narrow.


The more options and drivers, the better, so i can fine tune the response more evenly.


I dont need extreme volume, reference +5db is more than enough. Just need as perfect of a response as possible.
 

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You mentioned infinite baffle. What is behind these wall spaces and can the enclosure be open to the next room? If so, then definitely 18" drivers in an infinite baffle. Most bang for the buck are the FI IB318s.
 

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Discussion Starter · #14 ·
As a refresher, I have cavities in the wall for 4 subs (one in each corner of the room) for a 5500 cu ft room.


There is room in the wall for me to build a sealed enclosure with these INTERNAL dimensions:


7.5"x73.5"x20" = 6.38 cu ft.


About 3 Cu Ft is recommended for each Dayton Ultimax 15" subwoofer driver. My space is just right for 2 drivers in series (8 ohms) on one channel of a pro amplifier (like crown XLS).


Questions:

1. Is it best to wire two 2+2 subs in series to get 8ohms or is there a better way to do this?

2. Is there any difference between impedances in the final result assuming your amp can handle down to 2ohm loads?

3. How much space is usually needed behind the sub driver for ventilation of the driver with a Dayton Ultimax?

4. For my cubic footage, are 15" drivers even needed or will 2x12" drivers per enclosure already provide crazy bass for a 5500 cu ft room? (goal is multi-seat smooth response at reference volumes, not earth shattering competition bass)

5. Is MDF the best material, or is there other routine hardwood that would be even more rigid and vibrate less?


Soon as I get these questions answered, I can order my drivers with confidence! Any help is appreciated!
 

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Quote:
 1. Is it best to wire two 2+2 subs in series to get 8ohms or is there a better way to do this?
 

For a single sub, you can wire it as 4 ohms or 1 ohm.  If your amp can't do 2 ohms then you want to wire both drivers (4 ohm) in series for 8 ohms. 

 
Quote:
 3. How much space is usually needed behind the sub driver for ventilation of the driver with a Dayton Ultimax?
 

If the pole vent is 1" in diameter then 1" behind the driver should be alright.

 
Quote:
 4. For my cubic footage, are 15" drivers even needed or will 2x12" drivers per enclosure already provide crazy bass for a 5500 cu ft room? (goal is multi-seat smooth response at reference volumes, not earth shattering competition bass)
 

Go BIG, you'll regret it later 
 You are going to need a decent amount of subs to reach reference volume in a 5500 cu ft room. I don't know if I would go with 2x12" sealed subs, I would go ported and tuned to 20hz. Multiple ported subs tuned to 20hz will go loud.

 

Here is a comparison of two sealed ultimax 15 with 1500w and two ported infinity 1260w tuned to 20hz, 800w.



 

 
Quote:
 5. Is MDF the best material, or is there other routine hardwood that would be even more rigid and vibrate less?
 

MDF is cheap, straight, heavy and dusty when cut. Plywood like Arauco is also cheap, light in weight but can warp. Birch is nice to work with but expensive. If you don't mind the dust, I would go with MDF.

 

 

 

You can always go crazy and get 16 infinity 1260w at $55 each... 4 sealed in each corner.

http://www.sonicelectronix.com/item_18916_Infinity-Reference-1260W.html
 

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Discussion Starter · #16 ·
Damn those infinity reference speakers are cheap, are they as good as the daytons? I actually do have room for 4 of those if you think that would be a better option....


I realized I have enough room between studs to actually extend back of my box and make room for the speaker magnets and extra space for keeping the speaker cool.



using Crown XLS amps, does it really make a difference if the final speaker load is 2 ohm or 8 ohm in terms of sound quality maximum SPL? I am assuming it does not make a difference...?
 

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The crown xls can do stereo 2ohm so you can get more power if you wire the drivers as 2ohms. Eight Dayton 15" Ultimax is going to be amazing if you have the power to push them to their potential. If you want to save some cash and get almost the same spl then go with sixteen 1260w. 

 



 

 

Eight Dayton 15" ultimax with 4000w and Sixteen 1260w with 4000w. Both are pretty much the same BUT the infinity drivers are at its excursion limit. The Daytons could be pushed further with 8000w which will give you another 3db.
 

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Discussion Starter · #18 ·

Quote:
Originally Posted by Mrkazador  /t/1525098/structurally-simplest-diy-with-a-large-number-of-subwoofers#post_24577258


The crown xls can do stereo 2ohm so you can get more power if you wire the drivers as 2ohms. Eight Dayton 15" Ultimax is going to be amazing if you have the power to push them to their potential. If you want to save some cash and get almost the same spl then go with sixteen 1260w. 






Eight Dayton 15" ultimax with 4000w and Sixteen 1260w with 4000w. Both are pretty much the same BUT the infinity drivers are at its excursion limit. The Daytons could be pushed further with 8000w which will give you another 3db.

Awesome, thanks for the great info!


I ordered the dayton 15" and I'll wire them to have a 2 ohm impedance per box. That should give me very decent power per driver.


I won't be driving them anywhere near max power/excursion requirements so we should be all good I think.


I can always pick up a behringer to try if absolutely needed. Is fan noise and reliability of the Behringer Inuke series an issue?
 

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Quote:
Originally Posted by blazar  /t/1525098/structurally-simplest-diy-with-a-large-number-of-subwoofers#post_24577203


...using Crown XLS amps, does it really make a difference if the final speaker load is 2 ohm or 8 ohm in terms of sound quality maximum SPL? I am assuming it does not make a difference...?
Don't want to cloud the water here, but don't make that assumption.

To truly evaluate amplifier performance - all the criteria ( qualifiers ) have to be examined.

Crown has to compete in a market where large wattage numbers sell.

So it lists power under a variety of signal and load conditions.

IF you listen to 1khz signal @.5% distortion ( doubtful ) than that rating is meaningful

Otherwise expect less power with a larger bandwidth and for lower distortion
http://www.crownaudio.com/media/pdf/legacy/133465-6.pdf


Note on page 20: Power draw and Thermal Dissipation

It's easy to see that with an increase of duty cycle or a reduced impedance load - the current draw and amount of heat generated increase substantially.

Cooler amps last longer.
 

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Discussion Starter · #20 ·
Ok so here is the update:


I can actually build my boxes to about 7cu ft and can cut into some studs a bit and achieve the depth I need.


Ordered 8x15" dayton ultimax, waiting for next shipment.


Ordered a Lab Gruppen PLM 10000Q off of ebay and I will likely wire the speakers for 8ohms or put in a 30amp power line so i can wire them for 2ohm... The 10000Q can defintely do 2-4ohm (in fact that is the standard operating range).


I placed a my JL fathom f212 sub at my sitting position and did a "sub crawl" and discovered something useful. The subwoofer locations in my wall are in fact the "hottest" spots in the room. Higher up on the wall was even better... Since this will be a dual driver setup, one of my drivers will be near the hottest spot in each of the 4 corners of the room.


This should get me maximum "room gain" correct? Will this typically help all bass frequencies or just some of them?


The fathom 212 (dual 12") sealed with "sine wave" sweeps was straining pretty hard to reach high SPL and was making some driver "flapping" noise at the low end 20-25hz.


Hopefully 8x15" drivers will do a much more impressive job....
 
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