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E-Wave box type?

post #1 of 20
Thread Starter 
Got my drivers! BC250, QSC, 2512, and my miniDSP.
Box will be scratch built. Size is not a consideration as will be behind a screen.
In general, for an Ewave, what would lead one to choose, or reject:
1) Sealed
Smaller size? Any acoustic advantage?
2) Vented
Better efficiency? Bass extension?(less important as already have TubaHT)
3) Passive radiator
Would this have a detrimental effect on the constant directivity goal?

And finally, if I model the 2512 using TS parameters, etc, rec.box size is 2.37 cf. Manufac spec sheet says 0.8!! What do I believe? That's a huge difference!
post #2 of 20
Ill have to look at my 2512 models when it I get on a computer but I would suggest vented if you gave the space. The nice thing about vented is that you can always plug the port and it will work as sealed. By doing this you can try both alignments and choose which gives you the best room response after measuring.

I would suggest maintaining the same baffle width and horn to woofer spacing that Zilch designed them for. Also, I'd recommend rounding over the front corners of the box. It isn't vital and if you prefer the look of sharp corners that is fine. The roundovers will just give you a little smoother response.
post #3 of 20
In this document:

http://www.parts-express.com/pedocs/...-more-info.pdf

Eminence identifies several possible alignments. The first one they identify is vented with 2.75 cubic feet.

coctostan:

I've been reading the various Zilch threads and planning my own E-Wave build, I assume it is always beneficial to minimize the center to center spacing of the horn and tweeter to maximize the height of the vertical lobe at the crossover frequency. Is that not the case? Is their a reason not to have them as close as possible?
post #4 of 20
This is what I'm trying for the same setup. It is about 2.5 cu. ft. tuned to 45 hz. Sorry for the cell phone pic.


LL
post #5 of 20
Ohlwiler-

The box size and tuning you choose is dependent on how big of a box you are willing to have. IMO, the optimal size would be ~4cu ft tuned to ~40hz with a highpass between 30-50hz depending on what works best in your room and placement. You can also stuff the port and highpass around 50hz for a nice rolloff around 70hz. I would use a single 4" port or equivalent.

Smaller also works such as BigJim_inFLA's 2.5 cu ft @ 45hz. It peaks a little more than I'd like and the port resonance is going to be deeper in the passband. None of that is a big deal, just a little less than optimal.

Zilch was tuning around 30hz in 1.6cu ft which is even less optimal, but still doable.

Basically, you have to have an idea of how big your are willing to go.
post #6 of 20
As you have a MiniDSP, 6th order ported is the way to go.

82 litres net, 36Hz tune (with a Q=2 HPF @ 36Hz), 1 x 100mm port 15.3cm long. As the 2512 is very sensitive and doesn't have a lot of Xmax, 50W is about all before it hits Xmax near tune.






LL
LL
LL
post #7 of 20
Thread Starter 
Another rec was to consider a "tapered TL" if a larger size was OK. I am not sure exactly what this is and if it is a reasonable choice for an E-wave?
Thanks for all the ideas above! The one posted by A9X-308 is nicely detailed.
post #8 of 20
Thread Starter 
So is this what is meant by a tapered TL? In my case I envision a single driver in the box, the Deltalite 2512, with the waveguide mounted bare on top of the box at the proper CTC spacing, or the WG could be in the box. What advantages or disadvantages does this type of setup entail for an E-wave? (again, size is not a big consideration for this behind the screen speaker)
post #9 of 20
mini dsp will put out tons of noise with 108db
post #10 of 20
Quote:
Originally Posted by gmannel View Post

So is this what is meant by a tapered TL? In my case I envision a single driver in the box, the Deltalite 2512, with the waveguide mounted bare on top of the box at the proper CTC spacing, or the WG could be in the box. What advantages or disadvantages does this type of setup entail for an E-wave? (again, size is not a big consideration for this behind the screen speaker)

A TL will work, but the only software that designs them correctly is Hornresp of Martin King's. It is not the case where you can simply copy the dimensions of a TL designed for another driver and have it work, it will need to be designed for the one you intend to use. I only see it as of potential benefit for the EQ phobic. I can't help you with the design, but someone else might be able to.

6th order ported was liked by Zaph and I've used it a few times to great effect, and Zaph was a fan if it. It barely rates amongst conventional philes because it needs specific EQ. Thiele was the originator of the idea IIRC.

Quote:
Originally Posted by cookieattk View Post

mini dsp will put out tons of noise with 108db

Rubbish.

There have been plenty of builds here using compression drivers, and 108dB is about the average sensitivity of a CD. The MD has better SNR than RBCD standards and people have been using CDs for nearly 30 years without issue if set up correctly.
post #11 of 20
"mini dsp will put out tons of noise with 108db"

explain.

as for an enclosure, if you will be using subs, i suggest going sealed (2 cubic feet shaped as deep as possible and stuffed).

line the walls with a good absorber, such as: http://meniscusaudio.com/ecocore-p-931.html
post #12 of 20
Quote:
Originally Posted by LTD02 View Post

"mini dsp will put out tons of noise with 108db"

explain.


ok i use a 8x8 mini dsp that puts out noise kinda sounds like ground loop combined with a cell phone going off inside my beyma only fix was to turn down the output volume to -24 db more then that didnt help. then the noise was less but still there @ 7ft.

this is on a beyma tpl-150h the nose is also in the woofer and it from the mini dsp.
post #13 of 20
I suspect you have an actual ground loop. How are you powering the Mini-DSP? Does the supply have common ground with anything else? I use a ground-isolated (cheap) wall-wart supply and the result is very quiet. I can hear a faint hiss only when right near the horn mouth.
post #14 of 20
Thread Starter 
OK so if I go the 6th order ported route, is the info provided basically all I need?(82 litres net, 36Hz tune (with a Q=2 HPF @ 36Hz), 1 x 100mm port 15.3cm long)
As a beginner, a few questions:
What is meant here by 6th order? The rolloff slope as in crossovers?
Why does the use of the miniDSP suggest this plan?
Is the "Q=2hpf @ 36Hz" something built passive, done through the miniDSP, or set through the AVR?
Does the box shape matter? Thinking a trap shaped box like Zilch's original, but taller to account for the recommended 82 l, or 2.9 cf, net, narrow as the QSC will allow w/ rounded over edges and correct CTC driver spacing.
Any trick or guidelines to use to calculate net volume after bracing and driver mounting? (I think my QSC/CD will actually be top mounted outside the woofer box)
post #15 of 20
Thread Starter 
LTD02
Thanks - sealed would be easiest, and thanks for the damping material link!
I will have a sub, THT in progress. These other concepts are all fascinating, tapered TL, 6th order ported, etc - and I am trying to learn as much as possible about my "new" hobby!
post #16 of 20
Quote:
Originally Posted by bwaslo View Post

I suspect you have an actual ground loop. How are you powering the Mini-DSP? Does the supply have common ground with anything else? I use a ground-isolated (cheap) wall-wart supply and the result is very quiet. I can hear a faint hiss only when right near the horn mouth.

it doesn't have a ground loop problem it can be isolated from every thing including sitting on a cardboard box in the air with just the output connected to the amp and still makes the noise.
post #17 of 20
"...thanks for the damping material link!"

np. that material or a similar one was pointed out by member decadent_spectre, who was looking for a fiberglass alternative. the recycled material appears to have better absorption, which was kind of surprising to me. putting a bunch of cotton fibers next to electricity sounded like a recipe for fire, but apparently the fibers are treated, so that they will not burn. i don't have the link ready at hand, but the absorption was much better than fiberglass below about 250hz.
post #18 of 20
A TL for a driver of that size is likely going to be huge. I'm don't have a lot of experience with TLs though so maybe it could be done. IMO it is not worth the effort.

If you want a smaller box go with the 6th order vented like A9X described. If you don't mind a bigger box the 4cu ft tuned to about 30hz is ideal IMO. It will give you a little more headroom than the 6th order setup but you need a larger box.

Remember you can always plug a vented sub to make it sealed. This will allow you to tweak to see what measures best in your room.
post #19 of 20
Quote:
Originally Posted by cookieattk View Post

it doesn't have a ground loop problem it can be isolated from every thing including sitting on a cardboard box in the air with just the output connected to the amp and still makes the noise.

But how is its DC power coming in? The DC power negative terminal is also the audio ground. If that also somehow connects to the AC wall socket ground, or gets its DC power from your amplifier, that would be a ground loop.
post #20 of 20
Quote:
Originally Posted by bwaslo View Post

But how is its DC power coming in? The DC power negative terminal is also the audio ground. If that also somehow connects to the AC wall socket ground, or gets its DC power from your amplifier, that would be a ground loop.

there is no ground loop the dsp chip puts out noise.
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