DIY Sub Possibility...

[Indyjeep]

So, I have been looking at going DIY vs another Sub-12........Im looking at using a Soundsplinter RLP-12 12" sub. With about 2-3 cu. ft. sealed enclosure. Now I want to hook this up to a Yamaha HTR-5750. But I am confused on how to use something like a Nady XA-900 or a Behringer EP-1500 with the receiver. Since these amps only hav XLR inputs 1/4" inputs. How would I do this? Would I have to have a seperate preamp or EQ for this to work? I basically am going to this peice by peice. So any help would be appreciated. Thanks a lot!! Also if you have any other ideas about what Im doing or help that would be awesome!!

[Jay481985]

you can used unbalanced 1/4 rca to 1/4 inch phono. Though in short lengths. www.DJMART.com has it

[formica]

Since these amps only hav XLR inputs 1/4"

inputs. How would I do this? Would I have to have a

seperate preamp or EQ for this to work?

Basically you will go from your Preamp (receiver)'s subwoofer out

directly to the amp's input... and you can convert the RCA to 1/4"

input using a simple adaptor like:

RCA JACK TO 1/4" MONO PLUG ADAPTOR

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=090-285

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=091-1010

Should work like a charm...

An EQ adds the flexability to tune your subwoofer to your room... but this is true for all subs, bought or DIY...

ROb

[DrWho]

Have you already purchased this sub? It doesn't model very well for an

HT sub because it was built to take advantage of the cabin gain in a

vehicle (which isn't present in a home setting). With an F3 of 44Hz, your mains probably will have better bass

response.

[Jay481985]

Soundsplinter subwoofers though impressive in xmax and such are not

quite the go getters for home theaters. The Qtc is way to high fo home

theaters without a redicoulous enclosure (Try 20 cubic feet, most

fridges start there) and don't even try porting or pr the sucker.

They will not hit low without massive enclosures.

[Indyjeep]

You think so?? Well what about the new Ascendant Audio subs? like the Arsenal line? With an Fs of 27hz and xmax of 20.5mm, would that do well in an 7 cu ft enclosure? This is kinda a tax gift for me plus something to keep my busy for a couple weeks. Only reason I thought of the RLP 15" is because Ive heard good things about it, but than I remembered that they were in huge enclosures and somebody even did a IB of one or two. Ok so I know the amp, but sub is another thing. Or what about two Assassin 12"? With an fs of 23.1 hz and an xmax of 15.5 mm, plus only $95 right now...any thoughts? This will happen soon in the next week or two.. Also my mains are JBL HLS820s, dual 8" with horn tweet. So I got the mains covered......

Thanks All

Adam

[DrWho]

You might try the Ascendant Audio Aresenal 12"

In a 5.5 cubic foot enclosure tuned to 22Hz it has an F3 of 19Hz and

can do about 115dB. It models better than the 15" and 12" Titanic - and

costs less too.

[Indyjeep]

Sounds like a plan....

DrWho,

what do you use to model the speakers in enclosures?

[DrWho]

http://www.linearteam.dk/default.aspx?pageid=winisdpro

[Indyjeep]

Thanks DrWho. Shall look into that. Now Im just curious, if I make the enclosure larger, will it produce a better low end? Or will it not do anything at all?

Arsenal 12" Dual 4 Ohm

Behringer EP1500

Behringer DSP1124P

Would the DSP1124P act as a good xover unit?
Ive heard a lot of people have extremely good luck with that unit.

[efzauner]

Indyjeep: DrWho sent the link for you to use! It is a very easy to use software to design speaker enclosures. It comes with a good data base of drivers and it is very easy to add new drivers to it. There are a lot of TS parameters, but the only ones that it really uses is Qts, wich is the combined Qms and Qes. Fr resonant frequency, and Vas, wich is is a measure of how springy the suspension is stated in terms of the compressability of an equivalent volume of air. The other one that is good to enter is SPL the efficiency in dbm/W. Be carefull as some woofers are spec as dbm/2.82 Volts, wich would be the same as 1 watt into 8 ohms. So if you are comparing a 4 ohm car subwoofer at 88dbm/2.82 volts, that would actually be 85dbm/watt.

Just do the math Watts=V^2 divided by ohms.

2.82^2 = 8 watts and 8 watts divided by 4 ohms = 2 watts. So it takes 2 watts to give you 88 db. With only 1 watt, that is half the power, it would output only 85dbm

You can quickly try out different woofers in different enclosures and see how they respond. You can build sealed and vented (stay away from bandpass for good quality sounding DIY subs). You also do not want a big hump in the low frequency response because that comes from a very high Q combination of driver and enclosure. A higher Qtc (shown in the sealed BOX tab) means that the woofer will keep on vibrating after the signal stops. For Vented enclosers, it is QL that is uses. WInISD will do the basic design automatically for you with optimal Qtc and QL. You can change them a bit but do not go overboard. Compare this to a car suspension: A speaker is like a car: The weight of the car is the mass of the speaker, the spring is the VAS, and the shocks are the damping. You do not have a direct spec for damping, but Mass, Vass, damping and QTS are related. Basically the Q (or Quality) is how much damping or shocks you have compared to the spring. So putting that all together, a heavy car with weak springs and bad shocks will keep on moving for a long time at a very low frequency. As you make the car lighter, or make the springs harder, the resonant frequency goes up. Bigger, heavier cars need stronger shocks that light cars etc. Woofers are design for different purposes and thus have different masses, Vas, and Q just like cars are designed for different performance. The speaker cabinet is the last part that you can actually design. A sealed cabinet just adds an extra spring, like making a car suspension stiffer. A vented cabined adds an extra spring and mass and you now have a second resonant frequency lower than the speaker itself that you can play around with. A bandpass designs add more combinations of mass and springs to add resonances above and below the resonant freqeuncy of the speaker.

By using the car suspension analogy you can understand why subwoofers that go lower in frequency have heavier mass, but also need more damping, or shock. The result also means that it takes more power to move, and thus less efficient. If you compare to Klipsch speakers like the Heresy, it uses a light cone for more efficiency, but sacrifices bass. Tweeters on the other hand are very light, but have stiff suspensions in order to resonate at very high freqeuncies.

Have fun. I gave you the basics.

[efzauner]

To answer your question about a bigger box directly, yes, a bigger sealed box will give you lower bass, but again, compare to the car. A bigger box is a weaker spring. Give a car a weaker spring, and it will wallow down the highway at a lower frequency. Make the spring too week and the suspension will bottom out. So you have to be carefull. WinISD also has the ability to calculate cone excusion if you add xmax and Qes and power handling. But stay at a Qts of betwee .7 and .9 for a sealed enclosure and you should be OK. Others may want to comment on that.

Oh, by the way, there is a certain car wallowing frequency that will make you sick. Car makers stay away from that!

[formica]

To answer your question about a bigger box

directly, yes, a bigger sealed box will give you lower bass, but again,

compare to the car. A bigger box is a weaker spring. Give a car a

weaker spring, and it will wallow down the highway at a lower

frequency. Make the spring too week and the suspension will bottom

out.

We usually agree, but in this case I'm not entirely sure on the car

analogy... as reducing the enclosure's "air spring" will actually

reduce the woofer's "ringing". That is why having a high Qts will

create a bump in the frequency response due to this effect.

If you reduce the air spring (large enclosure) you'll be left with just

the woofer's motor and suspension controlling it's cone's motion.

This is a desirable effect... as it'll allow it to accelerate and stop

much quicker, without external influences. It'll increase bass extension and increase efficiency,

but you also do increase chances of bottoming out your driver.

Although it may seem that a large enclosure reduces the woofer's total

output (SPL) it actually rearranges it on a frequency level: decreased

level at higher frequencies while increased levels at lower

frequencies. Total air volume displaced remains the same.

I don't like having my car wallow down the road, but I do not like having my woofer ring because it rides on a stiff spring.

ROb

[formica]

Would the DSP1124P act as a good xover unit? Ive

heard a lot of people have extremely good luck with that unit.

No it wouldn't... it has no x-over function, but it can be used

as a parametric EQ. BTW, it has just been discontinued by

Behringer... and will be replaced by FBQ2496. Similar EQ function

for a little more $.

ROb

[DrWho]

If we simplify matters we can call the driver a single mass on a spring.

In a sealed enclosure we have a single mass on a spring (the driver) coupled to another mass on a spring (the trapped air inside the enclosure).

In a vented enclosure we have a single mass on a spring (the driver) coupled to another mass on a spring (the trapped air inside the enclosure) coupled to a third mass on a spring (the port).

It is the overall net interaction between the "system of springs" that determines the overall behavior of the system...it is a rather complex interaction and that is why we have these wonderful programs to model it for us.

One thing lacking in the small signal T/S models is the time domain (not talking about group delay here)...No matter how you tune the system, the addition of more springs is going to introduce extra resonations at certain frequencies. In other words, a sealed system with the same frequency response and SPL capability as a ported system is going to behave better (each succession of springs has a delayed reaction to the driver which can result in delayed damping)....However, the driver for that sealed system would have to be insanely better (thus more expensive). AND it would be a complete waste not to port that better driver because you could increase low frequency extension without sacrificing anything of the extra qualities in the higher passband (provided you did it right of course). Anyways, the conclusion of all this over simplification is to try and keep the ported frequency out of the passband of your musical content....because for the explosions in movies a little extra resonation never hurts []

[Zealot125]

You might try the Ascendant Audio Aresenal 12"

In a 5.5 cubic foot enclosure tuned to 22Hz it has an F3 of 19Hz and

can do about 115dB. It models better than the 15" and 12" Titanic - and

costs less too.

You were letting me go on about the Titanic in my other thread without tellimg me that there is a better perfoming alternative that costs less money??? Shame on you! How could you, I am hurt! No, but really, should I consider switching to this different driver?

PS Sorry for partial thread hijack...

[Jay481985]

ascendant needs quite a big box compared to the dayton

[DrWho]

Well I just noticed the Arsenal 12" didn't have such insane box size

requirements...I'm also not convinced it's a better performer than the

Dayton 15". So it's a trade off of about 1.5 cubic feet (5.5 versus 7)

and 6dB of SPL and 2Hz of extension.

And to make matters even more complicated, there is always the AES AV12

which is going for $150. 1dB less output than the arsenal and same F3

as the Dayton, but a 2.5 cubic foot enclosure...a PR would be required

for a cabinet this small though.

And you might as well model the 12" titanic too...which will be a

cabinet half the size of the 15 with the same F3 and 6dB less output.

...

Now if money isn't as important as cabinet volume, then I would look at

something like the Adire Audio Tumult, or even the AuraSound NS15.

These designs would require a 1000 watt amplifier (into 8 ohms) and

dual 18" PR's. And that's hard to tuck into a 5 cubic foot cabinet, but

you're looking at 117dB with an F3 of 20Hz. (the tumult going slightly

louder and lower than the NS15).

There are a ton of compromises to consider and it's going to be up to

the person building it to figure out what is the best tradeoff. It all

comes back to Hoffman's Iron Law. (extension, efficiency, and cabinet

size).

[Jay481985]

the aes 12 inch is 199 they upped the price

the aurasound is $$$

[DrWho]

Ummm.....

http://yellow.mynethost.com/~bv126368/shop/catalog/product_info.php?products_id=52&osCsid=a6e535d868107606cd158871e0ab6e17

I see $150?

And the Aurasound drivers cost the same as the Tumults.