Need direction with DIY 15" subwoofer

[bjornb17]

I may build a subwoofer in the next couple months based ont he Adire Tempest 15." Should i use the 15D2 or 15D4?

The purpose of this subwoofer is to have the lowest frequency response i can get with respectable volume. I will most likely be using a 250 watt plate amp.

Are there instructions i need to follow? How large do i need to make this? Should i use a passive radiator or ports, and if so, what size?

This would be my first project, so please help me find a place to start.

Thanks :)

[kexodusc]

Well, what are your goals for perfromance in terms of frequency extension and output? Will this be for home theater exclusively or split with music?
Your choice of the 15d2 or 15d4 will be determined by how you wish to connect the voice coils...in series, or parallel...I'm guessing you'd want the 15d2 with coils in series so you get 4 ohms...maybe there's reasons to go another way though?
250 watt plate amp is fine. MCM electronics has them on fo $50 right now. Buy it. Now. Fast. Before it's gone.

How big a box are willing to have in your room? This sub seems to like big boxes. What frequency will your crossover to the subwoofer? 80Hz? 90Hz? 60 Hz?
If you can answer that you can really fine tune this sub to your needs, if you're not sure, you'll probably be a bit more flexible.

Personally, I'd go with a sealed cabinet, 3.5 cubic ft. 3/4" MDF with a double thick front baffle. Shelf bracing, with a 15" hole in it about1/2 depth. This tunes the box to about 32 Hz and gives an F3 (response -3dB) at 35Hz. That sounds high, but that's misleading. A sealed cabinet has a much slower roll-off on the response than say a ported design. In a room the response will be much lower.. If you used the DIN 45 500 measurement to determine "in-room response" (say F9) you're all the way down to 20Hz. You almost all the extension of a good ported sub with the improved sound quality and transient response a sealed can provide.

You'll have no problem pushing this sub to 100 dB with peaks as high as 110dB with that amp.

Any reason for chosing the Adire Tempest?

[bjornb17]

Well, what are your goals for perfromance in terms of frequency extension and output? Will this be for home theater exclusively or split with music?
Your choice of the 15d2 or 15d4 will be determined by how you wish to connect the voice coils...in series, or parallel...I'm guessing you'd want the 15d2 with coils in series so you get 4 ohms...maybe there's reasons to go another way though?
250 watt plate amp is fine. MCM electronics has them on fo $50 right now. Buy it. Now. Fast. Before it's gone.

How big a box are willing to have in your room? This sub seems to like big boxes. What frequency will your crossover to the subwoofer? 80Hz? 90Hz? 60 Hz?
If you can answer that you can really fine tune this sub to your needs, if you're not sure, you'll probably be a bit more flexible.

Personally, I'd go with a sealed cabinet, 3.5 cubic ft. 3/4" MDF with a double thick front baffle. Shelf bracing, with a 15" hole in it about1/2 depth. This tunes the box to about 32 Hz and gives an F3 (response -3dB) at 35Hz. That sounds high, but that's misleading. A sealed cabinet has a much slower roll-off on the response than say a ported design. In a room the response will be much lower.. If you used the DIN 45 500 measurement to determine "in-room response" (say F9) you're all the way down to 20Hz. You almost all the extension of a good ported sub with the improved sound quality and transient response a sealed can provide.

You'll have no problem pushing this sub to 100 dB with peaks as high as 110dB with that amp.

Any reason for chosing the Adire Tempest?

Hey, thanks for the incredibly helpful reply.

First of all, i went to mcm electronics but cant find the 250 watt amp.. can you give me a link please?

Secondly, already have a velodyne cht-12 connected, so i may lower the gain and set the crossover to it at 60 or 80 hz (it's currently at 40 hz), and then the new sub will probably handle 40 hz and below. the purpose of this sub is the have the maximum extension possible. My goal is to have the -3db at no higher than 20 hz.

I downloaded a box calculator, and it seems that porter boxses require a much larger enclosure though. i dont mind have a larger sub, but i dont want it to be outrageously huge. but 20 hz is pretty important. do you think i can get there at -3db with a sealed?

I chose the tempest because i heard good things about it, but I'm always open to new suggestions :) I think half of the fun of this project will be figuring everything out.

Thanks again

[kexodusc]

I wouldn't worry about the -3 dB down to 20Hz. Any sub that had that response in a real room would undoubtedly have a very noticeable deficiency in the higher bass region (which is more important musically). You will experience room gain below 60 Hz, real performance will extend the bass response.
My sub has an F3 at 32 Hz or so, but my in room response goes down to 19 Hz. I have some nasty peaks because of room gain in the high 20's. I'd accept a -9 dB at 20Hz for real usuage. What size is your room? You should consider parametric equalization.

Dayton, Atlas, and NHT drivers are very popular these days too...might consider those as alternatives to Adire. Depends on your budget and needs. Nothing wrong with adire.



This should be the MCM amplifier deal...good price.

http://mcm.newark.com/NewarkWebCommerce/mcm/en_US/endecaSearch/partDetail.jsp?SKU=50-6266&N=4

[bjornb17]

actually, the $50 amp is the 150 watt one. I don't mind using that, but will that be a little too weak for this type of application?

Also, as noted in my last post, im not too concerned about the upper bass region since i have another subwoofer to handle that, so deep bass is the primary concern here :)

Also, my room is quite small. 11'x14' This is just temporary though as i will be in a larger place before too long.

what type of boost should i expect from my room?

[kexodusc]

Boost is hard to predict, there are calculators and sources available...you should expect several dB's of boost, but also some dips from cancelations.
Sometimes too much emphasis is placed on the deep bass response. If you cross it over at 40 Hz, your response will be much lower, it depends what the reference SPL is.

[JeffKnob]

You should email Adire about some plans for the Tempest. Before they changed how they are doing business they had some plans up on their website and I used them to make my DIY subwoofer. My subwoofer consists of a Tempest and two PR15 passives in a 194L enclosure. It is bigger than I originally thought it would be but the sound is amazing especially after I connected a BFD inline with it. Adire did have plans for sealed, vented, and passive radiator enclosures.

When I made my subwoofer I already had a 2 channel amp that would do 150wpc so I just connected each channel of the amp to a separate voice coil as each voice coil was 8 ohms originally. If you are going to get a plate amp like the one at MCM you would need to get the D2 version to be able to get the 250W from it. You will then need to wire the two voice coils in series so the amp sees a 4 ohm load.