Check out what I just won on ebay.. DIY Sub Here I come! (1 Viewer)

[Alexis]

Regarding the sunfire sub amps, we know that the sunfire subs have heavy eq circuits, is that built into the amp or an external box?

I am worried about these sunfire amps having a built in eq that is customized for the enclosures and their drivers.

 

[Brian Bunge]

Alexis,

Yes, they're normally built into the amp itself, and yes that is a valid concern. Using an amp without knowing if it has any boost or not is like flying blind.

 

[Geoff L]

Come on Brett, you wouldn't drive that pretty Vette blind now would you?

Or would ya...

 

[Dan Hine]

I think by now Brett understands what everyone is telling him. But understanding and accepting aren't necessarily the same thing. I guess just let him do it. He'll learn the hard way but at least he'll learn. Right Brett?
Dan

 

[Patrick Sun]

"You can lead a horse to water..."

 

[Will Orth]

I agree with (Dan Hine)

 

[Will Orth]

I agree with (Dan Hine) I use the Daytons and they rock and handle the power well.
Will

 

[Ryan Schnacke]

Well, he's already got the amp so he might as well try it out at least. We can theorize all day about what bass boost or filters it might have. But if Brett likes the way it sounds then I don't really see a problem. Staying within excursion limits is a matter of self-control. You're not destined to lose you driver's license just because you bought a Corvette.

Brett, your original plan was to use the MB Quart in 50+ Liters sealed, is that right? That's plenty of volume for a 12" DVC, Shiva, Titanic Mk2 or Stryke AV12. Any of these could move twice as much air as the 10 inch MB. The Titanic and Stryke would be more like 3X. I'd probably build the box with a cutout for the MB and try it. If I found that it didn't have enough displacement then I'd widen the cutout and drop in one of those 12 inch drivers. If I still found myself wanting more then I'd consider building a 2nd sub.

 

[Geoff L]

Very true, and he is trying to find out if there is a type of boosting and or filtering, so maybe that info will come forth at some point.
And have to admit he did steal the amp....
I agree on building something that would allow a drop in if things don't perform to his expectations.
He dose run againts the grain though, and I think he might really enjoy doing it even though I don't understand it...

 

[Brett DiMichele]

Well gang I am back and I am here to bow and say "Brian was Right"

I knew he would be because I ran the numbers and came to
the same conclusions myself. But I figured I would at least
try it anyway.

No I did not blow the woofer but the amp just puts out too
much smoke and the woofer doesn't have enough guts to work
with it. I tried it on Star Wars ATOTC last night and I had
the gain so turned down it wasn't even funny. I doubt anyone
runs thier subs at -18 LOL

But the great part is I stole the woofer too, and now it's
going on ebay and I guarentee I will turn a profit on it
I just watched a used one sell for $130.00 last week and
I only paid $100 so, I will atleast get out from under it
and recoup the money to put into another driver.

As far as the amp goes, this isn't the amp from a TrueSub
this amp powers a 15" woofer in a dual ported enclosure of
fairly substantial size. I honestly don't see why there
would be any attenuation of any frequencies because of the
size of the driver, cabinent and power why on earth would
you need to boost any frequency? Even so, the amp is still
going to be used. I am still waiting for them to get back
to me with some more specific information.

But now I am honestly going to heed advice and sit back and
carefully review my options for the real sub.

I built an 18" cubed enclosure and I won't go any bigger
than that. So what should I use with that given enclosure
and 500 watts RMS of power? (Sealed) I could always port
the enclosure if I found a driver that would work in that
given air space but I would rather stay sealed if at all
possible.

Through all of this (knowing Brian was right) it was still
fun! It's not like I threw away money, the enclosure can
still be used, I am selling the driver and recouping that
money so what am I really out? nothing.. I just wanted to
see if something could be done, and the math was right and
it couldn't.

I do sincerely thank everyone who has put in thier opinions
and thoughts and now I am ready to embark on building a
real sub..

But I won't buy any driver untill I have all the facts. And
that means waiting to hear specific details about the amp
just to make absolutely certain what I have and what I can
use.

Sound good?
Again many thanks!

 

[Dan Hine]

But I won't buy any driver until I have all the facts. And
that means waiting to hear specific details about the amp
just to make absolutely certain what I have and what I can
use.
Sound good?

Sounds great!

 

[Geoff L]

All right Brett!
Five, count'em:star::star::star::star::star:
Now your on the straight and narrow as they say.
1)- Would you consider PR'ed in your cube?
2)- And do you have a max dollar figure to work with?
All ahead of the game as you wait for info on your amp as this is absoulty nesessary before you begin to model.
Geoff

 

[Ryan Schnacke]

Do you have access to a multimeter? You could measure the frequency response yourself. It might take some time to make all the measurements but its not really very difficult. Plus you can even buy a multimeter pretty cheap - like $30. You don't need super high quality or accuracy.

Here's what you do:
Use a simple tone generator to create 30 second recordings of the sine waves you'll want to use. Something like 10Hz to 40Hz in 2Hz steps and then 40Hz to 150Hz in 5Hz steps. Save these as wav files. Burn them to a CD.

Connect the subwoofer amplifier to your receiver but don't connect it to the subwoofer driver. Instead, contact the speaker outputs to the multimeter probe wires. Black to black and red to red (this isn't really critical, just make sure the positive and negative are NOT shorted together). Set the multimeter to read AC voltage.

(EDIT: make sure pos and neg are NOT shorted)

The multimeter should identify the maximum input voltage it can withstand. Note this and keep the volume level at a point where you're well below the limit. This likely won't even be an issue so just pick some moderate volume where you get around 5V to 10V magnitude when playing 50Hz or so.

Now maintain that volume level as you play each of the frequency tracks and record the voltage output. Enter this data into a spreadsheet program in a table format listing the frequency and voltage for each measurement. Make an additional entry for each measurement. This entry will be some relative measure of volume and you'll calculate it using this formula:
rel_volume = 10*LOG10(voltage^2)

Plot these rel_volume numbers vs. frequency. This won't show you the absolute volume level, but if the plot humps up by 3 at some level then you've got 3dB of boost there. Likewise if it droops by 5 then you've got 5dB of cut there.

If the plot looks funny or you just want to be thorough then play those tracks again and this time measure the voltage of the line-level subwoofer signal going from the receiver to the amp. You'll get much lower number this time - maybe around 0.1V. Plot this the same way. If it doesn't look like a flat line then the signal is getting filtered or somehow modified before it gets to the sub amp. If that's the case I'd play the tracks again but this time measure the voltage of the line-level signal from the CD player to the receiver.

Even if you're getting a funny response to the amp you could account for that by calculating the voltage gain of the amp at each frequency. Then convert to dB gain. Then plot the dB gain and look for anomalies. This last bit is getting a little more complicated but if you understand it then give it a whirl.

I've basically done this before. I connected the amp directly to the computer and just played tones on the computer. But I found that the audio outputs from the computer were pretty poor - the low end dropped off rapidly - and I had to account for this as I described in the previous paragraph.

You could also run the test with the subwoofer driver connected to see how the amp responds under load. But remember to keep the volume VERY moderate (1V to 2V magnitude) since you'll be playing pure sines and very low frequencies.

 

[Ryan Schnacke]

BTW I used this tone generator
http://www.nch.com.au/tonegen/

 

[Brett DiMichele]

Dan,
I understand that if the box was "small" they may need
to attenuate certain frequencies to make up for the roloff
induced by the box it's self. But the box that the sub
came in (the whole factory assembled system) is in a rather
large box, far larger than most sub boxes out there. The
physical outside dimensions of said box are 18 1/4" x 17 1/4" x 24"
H x W x D that's not exactly a small sub enclosure for a
15" driver in a dual ported config. I am just saying that
I "feel" that they wouldn't need to Boost or Cut anything
in this setup but no I can't be sure of it and that is why
I have to get answers first. And I will do that!
Geoff,
Yes I most certainly would consider PR's in my setup and
even bass reflex isn't out of the question. And if I have
to make a new enclosure that's not an issue either, MDF is
cheap.. Heck I paid $17 dollars for a 3/4" x 4' x 8' that
is cheap in comparison to what can be saved in DIY.
My biggest issue is the fact that I don't have a table saw
and the enclosure I made did not turn out the way I wanted
it to anyway. I have friends with Table Saws, So the next
enclosure will be done the right way, no matter how long it
takes.
I need to find out what physical "size" I can live with in
my room.. 18" cubed is a little big for even my tastes. My
living room just isn't big enough for all these boxes sitting
around.
That is one reason why I would like to use a 10" rather
than a 12 or 15" because of the air space requirements.
Honestly I can't see why selecting a 10" that can handle
the power would be a problem. A properly built enclosure
and a properly choosen 10" should make tons of low end.granted it can't move the air that a 12 or 15" will that
is just plain physics.
I wish I had a bigger room!
I am open to any and all solutions at this point and I am
going to research everything.
Ryan,
Thank you SO much for that info. Yes I have a multimeter
sitting right here in front of me. I am copying your post
to a text file and I am going to try your method if I can
not get any specs from the manufacurer.
Again many thanks all.
This has been a fun thread and a fun experiance!
I look forward to the day I can crack the plaster!

 

[Dan Hine]

Hey Brett,

But the box that the sub
came in (the whole factory assembled system) is in a rather
large box, far larger than most sub boxes out there. The
physical outside dimensions of said box are 18 1/4" x 17 1/4" x 24"
H x W x D that's not exactly a small sub enclosure for a
15" driver in a dual ported config.

Well, it is very dependent on the driver, but if the box was made of 3/4" MDF with some internal bracing minus port volume and driver volume and you're looking at about 3.25-3.5cubic feet. That actually is quite small for a typical 15" driver in a vented enclosure. For instance, to get optimum results from a Tempest or AV15 in vented enclosures you'll be looking more toward 8-9 cubic feet. I'm just posting that so anyone else that isn't familiar with required size/driver may see it.

But you've stated what your design goals are so lets focus on them. It will, after all, be YOUR sub. You want to go small. No problem. I'm thinking maybe a Brahma 12" driver in a PR enclosure would work well. I'm still a newbie with regards to PR design so perhaps Kyle, Brian or Jack could give you a hand. The Brahma 12 does have a bit of a high Fs but it works well in small enclosures, has great excursion and using XBL technology the excursion is very linear (what an audiophile would call "clean bass"). The Tumult might work also. Though I think the Tumult will exceed your (box) size requirements. Unless you went with an LT circuit but you'd want more than 500watts for that.

This site is a great resource. I have no doubt that you'll end up with a killer sub!

 

[Michael R Price]

"...granted it can't move the air..."

Brett, there's your problem... Moving air is exactly what creates bass. Doubling displacement allows 6db more potential output.

Anyhoo, you should at least consider a 12" such as the Brahma. That might work in a ~16" cube with PRs.

 

[Patrick Sun]

Size, extension, power. Pick 2 out of 3, the other can't be changed easily.

 

[Brian Bunge]

Brett,

I'd say right now with quite a bit of certainty that unless you're considering a Brahma 10" driver, forget 10" drivers all together. The next best 10" driver that I'm aware of is the SV10 from ACI. While it's no longer available I believe that Meniscus is coming up with their own version. Anyway, the SV10 is about the best 10" driver I'm aware of (along with the Titanic MKII 10") for home audio use. With the 500W of power that you have you're going to easily exceed Xmax with either of those 2 drivers. The Brahma could handle it, but I'm not sure what sized PR cabinet you'd need. I'll run some sims to see what's what though.

Also, bass boost serves two purposes. It helps to flatten out the low end of a sub designed for a box that's really not large enough for it and it also acts as a subsonic filter. Below the Fc of the filter you'll have a 12dB/octave slope. I've been told by someone that's been designing speakers almost as long as I've been alive that many manufacturers will place the boost right at the tuning frequency of a ported enclosure. By doing so, they flatten out the low end and then sharply attenuate the output just below that to protect the driver from bottoming. This isn't really the type of compromise we want to go with as DIY'ers. If you want to use that amp and not spend $339 for the Brahma (who's Fs is 35Hz, and thus really too high to use anyway), then the AV12 or AV15 is the way to go.

 

[Brett DiMichele]

Brian,

Thanks for the info as always!

I was thinking that by limiting my cabinent size I am
putting a major damper on what I can do. So I started
thinking why can't I go bigger? Width and Depth wise I
would like to stay within a certain size constraint and
the smaller the better, but nothing is stopping me from
going up... It wouldn't matter if I made a monolithic
type enclose and I am just using these numbers as an
example not an actual enclosure volume.. I could go with
say 13"W x 13"D x 20" H or even taller if needed.


So with that being said.. How about an AV12 in a ported
enclosure? I would want a little more room around the driver
so say 14" x 14" by whatever the height needs to be. Sub on
the bottom facing the floor and the port at the top similar
to an SVS only in rectangular form rather than cylindrical.

I haven't looked at the specs on the AV12 yet to see how
that would work (I barely have enough time to type this)
I will check them out for sure.

And yes I really do want to use the amp unless it is absolutely
undoable.