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Powered sub for ufonken plus?

Two years ago, my son -in-law built a bottlehead sex amp (2 watts) and was looking to build speakers for it.. Dave from planet hi fi, sold me the necessities to build a ufonken plus speaker, which I gave to him last xmas. He had fun building them.

The speakers worked out great and are plenty loud for near field listening (computer speakers). But, as expected, the base is a bit thin. So, I'd like to gather up plans and materials for my son in law to build a powered subwoofer. He has now acquired wood working skills and equipment, so a flat pack is not necessary.

In one of the paid plan sets that came with the ufonken plus, there were drawings for a small cube shaped sub utilizing two silver flute w14 drivers in a push/push configuration. If I remember correctly, Dave thought this might be a good match, utilizing a sub amp, either plate or stand alone. I would like to use a plate amp.

I am thinking of going ahead with this design, but I have questions;

1. Since the plans were not drawn to include space for a plate amp, I am not sure how to best modify the design. I am concerned that if I arbitrarily increase the volume of "the box" to accommodate the plate amp, it might alter the sound. And, If I change the interior volume, would the port need to be resized?

I had thought about compartmentalizing the part holding the plate amp, thereby not altering the original interior dimensions/Sonics of the "box".

2. The drivers come in 4, 8 and 16 ohm configurations. I figured I’d buy two of the 8 ohm variety, wired in parallel for a load of 4 ohms on the amp. Does that sound right?

3. Would a 100 watt plate amp be sufficient?

4. I have seen kits for diy powered subs from places like parts express, which I could consider, I guess.

I would appreciate any feedback or suggestions.

Thanks
 
frugal-phile™
Joined 2001
Paid Member
Sorry, i have a reply to your email partly done, but let’s just do it here.

1/ yes, the box volume needs to be increased to accomodate the volume (and maybe changed if the plate amp is large in any dimension). 1st is to know the volume of the plate amp. If the plate amp does not come in its own enclosure, it should be. An extention on the back of the box can be added so that the amp electronics are isolated.

I have some nice Foster plate amps (120w into 4Ω) that i can provide an example for. I have spares, they are cheap, but i am not sure if it is worthwhile shipping back across the border.

Once i know your choosen plate amp volume i can suggest (even draw) some modified plans.

2/ in this application 2 x 8Ω wired in parallel to get the most out of most plate amps.

3/ more than sufficient.

4/ if they are made of MDF (ie most), i would pass them by. I don’t like MDF for any speaker, but there is no excuse for using it in a subwoofer.

dave
 
Dave,

Thanks so much for responding. The plate amp I had in mind was this 100 watt from parts express. I would be happy to purchase one from you, but I need it for my son in laws birthday in a few weeks. Shipping across the border may take too long.

Dayton Audio SA100 100W Subwoofer Plate Amplifier

The manual on that page lists the following specs/dimensions for the amp;

Overall dimensions: 7 1/2 W x 8 11/16 H x 4 3/4 D

Enclosure cutout 6 1/2 W x 7 1/2 H

I don’t know if this gives you enough information.

I really appreciate your help, and hope you are doing well.

John
 
frugal-phile™
Joined 2001
Paid Member
Not if i get it out fast enuff, but the PE looks competitive, just a tiny bit kess power and no LF boost (best for sealed woofers thou). All down to the execution, and Dayton products (PE’s house brand)often push the cheap over quality. The only downside i see is the auto on. If you can bypass that and leave it on all the tie it would be better — manaula says you can).

But it is a cheap woofer. Does Madisound have any suitable, then you’d only have to pay 1 shipping.

dave
 
Dave,

I was thinking about the larger 28 L box, figuring it would sound better. But, the smaller 20 L box would save some space. We plan to put it on the floor, so the size is not all that critical. Your thoughts on one vs the other?

I didn’t see anything in the way of affordable plate amps on Madisound.

If you think the Fostex plate amps that you have are better quality, I’d be willing to buy them from you. I can get the two woofers in time for his birthday, so he has something to open. He won’t start the build for awhile, so if the amp from you arrives late, no biggy.

Plus, if you have the amp and know the dimensions, it would be easier for you to direct me on the mods needed.

Btw, I had envisioned construction with Baltic birch plywood.

John
 
frugal-phile™
Joined 2001
Paid Member
I was thinking about the larger 28 L box, figuring it would sound better. But, the smaller 20 L box would save some space. We plan to put it on the floor, so the size is not all that critical. Your thoughts on one vs the other?

The larger box goes lower. And once the volume of th eplate amp is added the extra size becomes relatively less large, than the comparison without. There are a number of variations on the 28 litre box, which do you prefer?

I will did one out, i will email you a price. If i get on it, i should be able to get one out Wed.

BB is good. Just watch the quality, some of the Chinese & Russian sorced are somewhat variable in quality.

dave