DIY SUB. I got the amp, I got wood(you can laugh), opinions on whats next?

polkanddie

Yea, Im hoping for the same results with mine. Ive built boxes before, but nothing too complicated.

ben62670

Going completely flat on paper doesn't tell the whole story. Don't worry about a nice sooth roll off. Environmental gain helps in most situations. The WINisd pic posted before has a bad hump. The design needed to be tuned lower.
Ben

billbillw

ben62670 wrote: »

Going completely flat on paper doesn't tell the whole story. Don't worry about a nice sooth roll off. Environmental gain helps in most situations. The WINisd pic posted before has a bad hump. The design needed to be tuned lower.
Ben

Ben,
Tuning lower still leaves that hump, but makes everything down low drop down significantly. That plot was the ideal quasi-Butterworth alignment for that driver given the published specs. Its an inexpensive car sub, so it doesn't go perfectly flat no matter what.

Polkanddie,
I really think you should reconsider going with a ported enclosure. Its much easier to turn things down (to avoid apartment eviction) than it is to crank things up to compensate for a negative ~10dB in the 25-30Hz range. There is a lot of material down there in movies. Remember that 3dB is perceived to be twice as loud. So 10dB is more than 3 times louder! I really think you will be disappointed in the response with a sealed box and that 10" sub. In a sealed box, you probably won't see much more low bass than what you already have with your tower speakers.


If it were a 12" or 15" sub, maybe you could do sealed, but with only a 10", you need to get every advantage you can with respect to frequency response. Building a ported sub is not really that much harder than a sealed, especially when you have modern software to do the calculations for you. Just cut an extra hole for the port, and buy a flared port kit, cut the port a little longer than specified, try it out, if the response is soft, cut a little off the port and try again.

If the box size is an issue, you can use ~1lb of polyfill per cubic foot of box to get a perceived increase of about .3-.4cf ft/lb. So, if the software says 2.7 cu ft, you could probably build it around 2 cu ft and stuff it with 2lbs of polyfill. Keep the port length the same as with the 2.7cu ft box. Also, remember to subtract the port volume out of the box size since it doesn't get counted towards the net box size.

sophie

bill,
i don't think a 3db difference is perceived as twice the volume, but it does require twice the power. I have read somewhere that a 10db difference is perceived as approximately twice the volume.....not sure about the 10db thing but i know that 3db does dot sound twice as loud.

Payton

billbillw

sophie wrote: »

bill,
i don't think a 3db difference is perceived as twice the volume, but it does require twice the power. I have read somewhere that a 10db difference is perceived as approximately twice the volume.....not sure about the 10db thing but i know that 3db does dot sound twice as loud.

Payton

OK, your right. 3dB is doubling of the acoustical energy, but we don't perceive it like that. My bad. Years of misinformation are hard to overcome...

Either way, the sub that is being built here will sound at least at 2 times as loud in the lower frequencies if he builds a ported version.

kawizx9r

billbillw wrote: »

OK, your right. 3dB is doubling of the acoustical energy, but we don't perceive it like that. My bad. Years of misinformation are hard to overcome...

Either way, the sub that is being built here will sound at least at 2 times as loud in the lower frequencies if he builds a ported version.

+1

Heck, I even did that with my 12"

polkanddie

Ok, the sub didnt arrive today, but the tracker says its in NC... So I saw a design for an infinity kappa vq sub with a slot port at the bottom that I liked. Im pretty sure I can work that into my enclosure.

kawizx9r

polkanddie wrote: »

Ok, the sub didnt arrive today, but the tracker says its in NC... So I saw a design for an infinity kappa vq sub with a slot port at the bottom that I liked. Im pretty sure I can work that into my enclosure.

(Flared) Port > Slot loaded enclosure imo.

Like I mentioned before, don't change up the subwoofer simply to make it "look" more appealing.

polkanddie

Ive heard that if you flare slotted ports it works just as well with less "chuffing"

kawizx9r

polkanddie wrote: »

Ive heard that if you flare slotted ports it works just as well with less "chuffing"

I still say flared port tubes....using WinISD you can determine how long of a port you'll need as well as diameters (to reach available frequencies/spl levels that the sub can produce), something I think you'd have a little more trouble finding out when using a slot-loaded enclosure. Up to you though really, I just think you should take into consideration some of the advice given on here so you can build yourself a better capable sub

polkanddie

Ups sucks.... its not going to be here until monday. I guess ill just have to start without it... I downloaded winISD pro so Ill start there. Flared ports are in the mix for sure.

polkanddie

This WINisd pro is awesome!!!!!!!!!!!!!!!!!!!!!!!! And Ive finally found the dimensions that I want for the box. I still have to draw it out, but I am making it 4.5 cubic feet. 18"x 1" slot port. The curve was good, and I will have room for it without making it a coffee table. Plus it should be easy to make. I am extending the box and having the amp mounted in a separate chamber. I am starting tommorrow, so expect some pics soon!! woofer is "scheduled" to come monday. Hopefully I can finish most of the box tommorrow. Wish me luck!

billbillw

polkanddie wrote: »

This WINisd pro is awesome!!!!!!!!!!!!!!!!!!!!!!!! And Ive finally found the dimensions that I want for the box. I still have to draw it out, but I am making it 4.5 cubic feet. 18"x 1" slot port. The curve was good, and I will have room for it without making it a coffee table. Plus it should be easy to make. I am extending the box and having the amp mounted in a separate chamber. I am starting tommorrow, so expect some pics soon!! woofer is "scheduled" to come monday. Hopefully I can finish most of the box tommorrow. Wish me luck!

4.5 cubic foot seems awfully large for a 10" sub.

Check your calcs (and input parameters) because I had it at 2.7 cubic foot. Use the parameters directly from Polk. Just download the manual for the db104. Make sure you keep the units correct.

polkanddie

Ill recheck and see what it gives me.

polkanddie

I did input all the parameters that i got from the manual. ill try and post the curve I got from all that.

kawizx9r

billbillw wrote: »

4.5 cubic foot seems awfully large for a 10" sub.

Check your calcs (and input parameters) because I had it at 2.7 cubic foot. Use the parameters directly from Polk. Just download the manual for the db104. Make sure you keep the units correct.

+1

My 12" requires a large box and I get frequencies down to 18hz, and it's 4.1cu ft. For your 10" that's only capable of free air response@25hz I doubt you need anything that large. By the way, did you really mean 1" x 18" port? I can see port noise coming from that small thing but I could be wrong.

billbillw

kawizx9r wrote: »

+1

My 12" requires a large box and I get frequencies down to 18hz, and it's 4.1cu ft. For your 10" that's only capable of free air response@25hz I doubt you need anything that large. By the way, did you really mean 1" x 18" port? I can see port noise coming from that small thing but I could be wrong.

Yes, I meant to say something about that. With a slotted port, you should not have the dimension ration of 1:6 or wider. 1:18 is too narrow and won't sound right.

There is some good reading here:
http://mobile.jlaudio.com/support_pages.php?page_id=141

Also, there is an easy Slot ported box calculator at the RE website:
http://reaudio.com/speaker_box/LPort_Box_Calc.html

Try different combinations until you get the desired box size and port tuning frequency. The calculator will then give you the cut sizes for each panel.

polkanddie

So what is the ratio for this sub? it looks to be no more than and inch and a half. Velodyne makes good gear too...

polkanddie

How about this, 2 cubic foot box, port 1.5"x12"x(14"long) tuned to 37 hz

Face

Round, flared ports are quieter and more efficient.

kawizx9r

polkanddie wrote: »

So what is the ratio for this sub? it looks to be no more than and inch and a half. Velodyne makes good gear too...

That's a completely different sub, and that company (like any other) builds enclosures specifically for their drivers.

polkanddie wrote: »

How about this, 2 cubic foot box, port 1.5"x12"x(14"long) tuned to 37 hz

37hz is a bit high imo, are you still using WinISD? Don't just throw numbers out there because it'll work, you're trying to get the most out of your sub now.

kawizx9r

You need to build something already, 3 pages and no pics! :mad: lol

Did you find out the dimensions you'll be using for your sub? Friend and I did mine keeping the outside measurements in mind, no need to over complicate things for a simple enclosure.

polkanddie

kawizx9r wrote: »

That's a completely different sub, and that company (like any other) builds enclosures specifically for their drivers.

And that is exactly what I have been trying to do, but if I tune it to 20 hz the curve it gives me a very steep drop around 50hz which is not good imo. Well 28 is about as low as I can go with this driver. I wasnt just "throwing" numbers in there. I was on a budget building this subwoofer. I bought this sub only matching up power handling. And it was cheap, as you can see it is a car sub. Not an HT driver. So. I am building the enclosure specifically for my driver just as you said.

kawizx9r

polkanddie wrote: »

And that is exactly what I have been trying to do, but if I tune it to 20 hz the curve it gives me a very steep drop around 50hz which is not good imo. Well 28 is about as low as I can go with this driver. I wasnt just "throwing" numbers in there. I was on a budget building this subwoofer. I bought this sub only matching up power handling. And it was cheap, as you can see it is a car sub. Not an HT driver. So. I am building the enclosure specifically for my driver just as you said.

There's another thread on here that specifically uses a car sub. Of course, different enclosure size/etc. than what you will be using (and different from what I used) but it'll give you another project to take a look at to give you some ideas.

http://www.polkaudio.com/forums/showthread.php?t=71073&highlight=MID+BASS+MODULE

Both his and mine have the same type center brace going, with the cutout being the diameter of the driver but his is completely finished and came out real nice looking.

polkanddie

The next day I have off work is Wed. But I took everyones advice and I am building the box to the tune of 28 hz, 2 cubic feet, 1.5"x12" port. And WILL be posting pics, I owe you guys that much!! lol.

polkanddie

That does look good, I will put similar bracing in mine. Thanks to everyone (kawizx9r, bill, and FACE especially) for all the great advice, I think its time to put this plan into action, Driver arrives tommorrow, Building will commence Wednesday. I bid you good day. The next time I post will hopefully have some good pictures for you.

billbillw

polkanddie wrote: »

The next day I have off work is Wed. But I took everyones advice and I am building the box to the tune of 28 hz, 2 cubic feet, 1.5"x12" port. And WILL be posting pics, I owe you guys that much!! lol.

slot port or round? If you are using a round, don't go smaller than 4" ID.

I still think you are doing something wrong. When I model that sub, its closer to 2.9 cubic feet and 25-26Hz tune. Are you are using the data for the db104? That is the sub you are getting from Newegg. There is major differences between the current db1040, the db104, and the earliest db10.

Use the data in this download:
http://www.polkaudio.com/downloads/manuals/car/DBSubwoofer_Manual.pdf

Enter in the parameters in the order that they are listed in WinISD (right to left, top to bottom). Use the tab function between each parameter and that will calculate certain feilds. If the program calculates a field, do not change it.

After that, do a new project, select vented, and choose C4 or QB3 alignment (really not much difference), and that should be your ideal size and tuning frequency.

Like I said before, you can shrink the box some (about .3 cubic foot per pound of polyfill/per cubic foot). 1lb/cubic foot is about the max you will get benefit.

If you are going with a slotted port, You really should keep the ratio 1:6 or wider. That means if 2" x 12", no narrower. That will give you a really long port (>30"). That's about double the length of a 4" port.

If you decide to use flanged (flared) ports, make sure you do the 'end correction' adjustment for either one or two flanged ends. It changes the length of the port. Read the directions that come with the port carefully with respect to how you measure the port length. I'm pretty sure you only measure the non-flared portion of the port when cutting it. Also double check the actual inside diameter of the port when you receive it. The 4" port might not actually be 4" ID.

polkanddie

so, with the overwhelming opposition to my slot port, I will take your advice. I worked it with what you gave me and it looked really good. thanks again. 3.0 cubic feet. 4"tube x14.2" long. tuned to 26hz.

polkanddie

You wanted pics, Here is one just to show you that they are coming. Sub arrived today...3days late. But thats ups for you, at least the sub works.... Drawing up the plans as we speak. I take it everyone thinks this is the best for my sub? I am really excited to be working on this, this is gonna be an awesome sub thanks to you guys.

polkanddie

Ok, here is a wild card, I got my hands on some 1.25" thick bulletproof plexiglass, I dont think I have enough to do the whole enclosure but I do have enough to at least the top and one or 2 sides... any thoughts? I think it would be awesome to be able to see inside the enclosure, the even if I just do the front I dont know what kind of bit to use with the router....any thoughts on that either??