my 1st diy sub

[johnkane]

Well, after having read all these posts, i have decided to build my own subwoofer. 1st problem where do i begin. I have a lot of questions, and many confusing answers. Here are is what i am working with.

hk dpr 2005 reciever, room size is 15x15, have older atlantic tech sats.(to be replaced with my next diy) Unit used 80% ht, 20% music.

now the questions:

budget $300 plus wood(have 5/8 mdf available). Mach5 pricing is pretty good. (i live in canada)

1. Ported or sealed
2. plate amp or pro amp
3. Mach 5 or Dayton, or other
4. 10" or 12"

Ported is better for Ht, i think i read that somewhere in this forum.

Have seen many projects but i am not sure which would apply to me. Found a complete diy for mach5 10", but not sure if it can apply to me http://diyaudioprojects.com/Speakers/MAW-10/MAW-10.htm

Need some direction, thanks

john

[ThomasW]

Hi,

The Mach 5 drivers are the best deal ever for those living in Canada.

I really suggest going with a larger driver. The only downside to the Mach 5 drivers is their relatively short Xmax. So think about either the 15" or 18" even in a fairly small room.

IMO it's much better to have more output potential and not use it, that need more output and not have it....

[johnkane]

my 1st sub

That's great, 15" it is.

Ported or sealed; Subwoofer facing down or straight; Plate amp or pro amp;
Box size?

I am really looking forward to starting this asap.

I appreciate all the help.

john

[johnkane]

here are my parameter with winisd. Dont know what
Le, Z and Bl are. I think i have the rest correct. See pic. Problem is Mach5 says 85L box and Winisd says 60L.

What am i doing wrong?

[ThomasW]

I don't use WinISD so I can't comment about it.

Le, Z, and Bl aren't needed to model a box

30Hz is too high a tuning for home use, it's prefect for a car.

I'd go with the sealed box or lower the tuning of a ported box to 20Hz.

[PMazz]

Unless you can/want to build a larger enclosure (~120 liters) big enough to hold a decent sized port (4" min) tuned ~20Hz, then go sealed. 56 liters will give you a nice lowish Q (~.57) and won't be too large. Looks like you'll need a fair amount of power as well (750W @ 8ohm). With the dual 4ohm VCs you could use a pro amp and feed a VC from each output.

Pete

[johnkane]

15" ported would be too big. Is ported really better for ht? If so i can go down to a 12". What software should i use to calculate my box dimensions? This is my first venture in box building so i need some help.

thanks,

john

[JasonB]

15" ported would be too big. Is ported really better for ht? If so i can go down to a 12". What software should i use to calculate my box dimensions? This is my first venture in box building so i need some help.

thanks,

john

I like ported subs for HT use, if you can live with the size they require less power at low frequencies for the same output. If I were using the 12" I would put it in a 50 liter box tuned to 20hz. That gives you a response that rolls off slowly in the low end. Room gain will help correct this and give strong response to 20hz or below. This driver/enclosure combination will handle 300 watts. The port will be an issue again in a box tuned that size tuned so low. You might have to go with a slot port that wraps partway around the inside of the enclosure.

I use Unibox to do all my modeling, I believe it's the favorite around here. It's a free download here:

http://home20.inet.tele.dk/kou/ubdwnld.html

One important note about the Mach 5 woofers.....

Mach 5's site shows the Re of their 10", 12", and 15" drivers to be 8 ohms with the coils in series. My MAW-10 measures about 4.2 ohms with the coils in series.

Jason

[ThomasW]

Ported are more efficient, they require a bigger box due to the port, they give more output at Fb (tuning frequency). Due to the port they have a faster roll-off rate below Fb.

One must be careful playing CDs or DVD containing content lower than the Fb of a ported design. Below Fb, the driver and the port start operating out of phase. If the content is low enough, or loud enough, the driver can do what's called "unload". Unloading usually kills the driver. This is one reason for the trend toward lower tunings 15Hz-18Hz, and the larger boxes needed to accommodate the ports for those tunings.

With a sealed box the enclosure itself acts as an acoustic filter. This rolls-off the bottom end of the passband protecting the driver. Sealed requires more power and additional EQ if you want to match the frequency response of a ported box.

None of subwoofer designs programs create the shape/size of the box, the programs simply tell you how big it needs to be. You decide the shape of the box based on the size of the driver, length of the port (if ported) and how you want the box to look.

[johnkane]

im not crazy about the slotted port. The look does not appeal to me or my wife. She is in on the design phase. WAF is active on this project.

What is the determing factor on the port width and length? After playing around with UniBox i noticed that the lower the frequency goes the longer the port length. I think? Couldn't i just use some ABS with some elbows and get the port length that i need?

I also read up on a thread in the mission accomplished section. Maybe a sealed box could be an option. http://www.htguide.com/forum/showthread.php4?t=14644

Would changing the driver make a difference on the port size and length? I am not completely sold on the Mach 5. Although the price is great, if it will work i wouldnt mind using it. Should Jasonbs' comments worry me. I dont really understand the problem.

"Mach 5's site shows the Re of their 10", 12", and 15" drivers to be 8 ohms with the coils in series. My MAW-10 measures about 4.2 ohms with the coils in series."

john

[PMazz]

Port area is determined by the size and excursion (swept volume or displacement) of the driver. Too small and you'll have port noise from too much air whistling thru the port. Port length is based on enclosure volume (Vb), tuning freq and port area. A larger port area increases port length for a given tuning. A lower tuning increases port length as well. To achieve a low tune in a small enclosure for a sub requires a large long port. To do this in a small enclosure you can research passive radiators. They accomplish basically the same thing as a port but are expensive. You'd probably be better off with a sealed enclosure and good power with EQ if you want to keep it small, or build a larger sub and go ported. If you decide on a sealed sub and want higher output, you may want to get a larger driver or one with higher excursion.

Pete

[ThomasW]

A straight port is an 'air-spring' operating with a known resistance. If you put bends in the port that changes the resistance. None of the modeling progams take port bends into account.

Since you need a smallish box I'm in agreement with PeteM's suggestion, go with a sealed box. They're easy to build and almost impossible to mess up.

I don't know about the Re, perhaps you should email Mark at Mach5 with that question. Having 2-8ohm VC's isn't a big deal.

[johnkane]

have an almost finished box

Just realized that sitting in my garage is an old wall unit that i had put together out of mdf. I can cut it up and the end result would be a rectangular box that would measure 16"x16"x40". The whole thing is made out of 5/8" mdf. This comes out to about 5.9 cuft or 167 liters. Is this enough for the mach5 ported? I can mod the height.

Also just found some refurbished elemental design woofers, 12".

600Wrms
12" model 130v.2D4: Qts .28 Qms 3.3 Qes .3 Re 8.3 Vas (Liter) 176 Sd (cm^2) 545
Fs (Hz) 21.0 Bl 21.7 MMd 127.00 MMs 134.00 Xmax 18.3mm
Unibox gives me a port of 9.2cm and 54.82 cm long, is an 80l enclosure at 20 hz.

400Wrms
12" model 13KV.2d4: Qts: .31,Qes: .35,Qms: 3.33,Fs: 21.5 Hz,Re: 3.7,Vas:162 L, Mms: 142 g, Bl: 15 T*m, SPL: 88.47 dB,Sd: 545 cm^2,Xmax:15.1 mm ,Voice Coil: 50 mm
Unibox gives me a port of 7.62(3") and 36.65cm(14.5") long, is an 80l enclosure at 20 hz.

This is beginning to look more reasonable. Suggestions, input and comments are all welcome.

[PMazz]

I come up with a net internal volume of ~4.3 ft^3. Tune it to 18Hz with a 21.5" x 4" flared port using either of the drivers and it looks pretty good. The 15" will have more output.

Pete

[johnkane]

Pete, you think the Mach 5 is a better choice than the ED 12's. The ed 13OV.2 has a much better xmax and same rms as the 15" mach 5.

john

[ThomasW]

For comparisons purposes you might want to calculate the Vd. Vd = Sd multiplied by the Xmax doubled. That tells you how much air a given driver will move.

[johnkane]

I get 19663.8 for the Mach 5 and 19947 for the ED 13OV2.

dont know what these numbers really mean. What units of measure are we talking here.

Thomas if i use the 5/8" mdf and double up on it, do you think it will be a problem?

I also was thinking about using carpenters glue and using my brad nailer to lock everything together, is this ok? I noticed everyone only used glue. Is there a reason for this?

john

[Bent]

routers don't like brads for doing roundovers.

[johnkane]

ok, understand about the nails. How would i mount the port? since my box will be 16wx16dx29h (121L), is it ok if i mount the port from the top down? If not i may need to put a bend in it.

Of course if all else fails, i'll just go for a sealed enclosure and save myself the touble.

Still debating the mach5 maw15 or the ed 130v.2D4, 12" 600 wrms.

john

[ThomasW]

It tells you that one driver will more 1.97L of air, the other will move 2.0L at full excursion. So not much difference

Doubled 5/8" will be fine.

[JasonB]

Should Jasonbs' comments worry me. I dont really understand the problem.

"Mach 5's site shows the Re of their 10", 12", and 15" drivers to be 8 ohms with the coils in series. My MAW-10 measures about 4.2 ohms with the coils in series."

john

John,

The only reason for bringing up the Re issue was that it could be a factor when choosing an amplifier. Mach 5 sells these woofers as dual 4 ohm, the measured Re of mine is 4.2 ohms with the coils in series, this means 2.1 ohms each. Thats very very low for a "4 ohm" voice coil. There is nothing wrong with having low impedance you just have to make sure the amp you choose will be happy with it.

[PMazz]

since my box will be 16wx16dx29h (121L)

That's too small for your port. What happened to 16x16x40? Don't forget the sims are based on internal volume. That 121l is actually ~92l internally figuring port size, bracing and driver. For that same 18Hz tune in that sized box you'd need a port 29" long.

Pete

[---k---]

How would i mount the port? since my box will be 16wx16dx29h (121L), is it ok if i mount the port from the top down? If not i may need to put a bend in it.

john

What are you using for port material? I think there are probably a dozen ways to mount the port. I used 9 1/2" sonotube for my port. What I did, I took one of my spare driver cut outs, then routed a circle in the middle of it with the same diameter as the port OD. It looked like a doughnut. I then fitted it around the port, and glued it so that the top of the pipe was flush with my doughnut. I then cut a hole in my box with a diameter just a hair smaller than the my port ID. I then glued the port up into place, using the doughnut as the major glueing surface. Then I did a quick flush trim and round over.

Not saying that is the best way to do it, but it worked for me.

[johnkane]

just picked up the elemental design sub model 13Ov.2, specs. are below. I also picked up the dsp1124p bfd. Should get them both next week. I'll play around with the box numbers and post soon.

Now is the behringer EP1500 enough power for the above? If i wanted to someday add a second sub will the EP1500 still be enough. What does the "bridged mono: 900 watts RMS @ 8 ohms, 1,400 watts RMS @ 4 ohms" mean.

Power: 600 Wrms
Qts: .28
Qes: .30
Qms: 3.3
Fs: 21 Hz
Re: 8.3
Vas: 176 L
Mms: 195 g
Bl: 21.7 T*m
SPL: 89.1 dB
Sd: 545 cm^2
Xmax: 18.3 mm
Voice Coil: 62.5 mm

[johnkane]

ok, after a whole lot of reading i now know what bridged mono means.

So, if read the specs. of the ep1500 right, i can hook up my 13Ov.2 in series to give 8 ohms and then plug the ep1500 in bridged mono and feed 800 watts into the sub. Or, maybe use both channels and feed 450 watts per vc.

What would the benefit be of getting the bigger ep2500?

john

[ThomasW]

"Power: 600 Wrms"

This means driver is designed to handle 600 watts max. So hook one VC to each channel of a EP1500 and don't over complicate things..