Suggestions for a single DIY hifi sub?

[motosapien]

I've got a sub out on my NAD pre and I'd like to build a single active sub to handle and reinforce the lower registers. My speakers reach into the 40Hz range and my set up is solely for music, not home theatre. The unit will sit between my main speakers.

[m R g S r]

do your current speakers play to 40hz with some authority, or they are just capable of playing down to 40? 40hz is pretty much dedicated subwoofer range...

[motosapien]

They are supposed to reach into the high forties and if they do, it is subtly.
I guess I'm looking for subtle, tunable and detailed supplemental bass to augment these. Perhaps it's a fools errand?
Maybe a smaller vertically oriented H frame. The ability to adjust it's freq. range and output would be important so the plate amp would need to be up to the task.

[bentoronto]

Ordinarily, adding woofer power without tweeter power (or the reverse) does not sound good.

Not a lot of music below 50 Hz. Big organ sound is often 80 Hz pipes. Only side drum plays down there much.

Big benefit is from removing bass from mid-range speakers when you add a mixed sub. But that requires cross-overs and amps. You might be pleased at how that wakes-up and clarifies your mid-range.

All things considered, just pasting on lower half-octave is of some benefit but not great benefit... unless you introduce sharp cross-overs and multi-amps. Not hard to do but a lot more fuss than what you had in mind. Of course, you may end up with something truly grand for music.

[djn]

I have the Emenence Alpha 15a in "H" frames with a little (inexpensive) 120watt plate amp. All in, one sub will cost about 2 bills. The kicker is that they sound much more natural than any other box sub I've had. And, the "H" frame is a very simple build that really only requiers of circular saw. If you have a table saw, then that is better.

Here is a good paper about them

http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

.
EDIT, I just looked at PE and found a plate amp for 60$ and the 15A for 60$. So for less than 150$, you can have a great sounding sub. The 15A is 97db eff. so the 70 watt plate amp is more than enough.

http://www.parts-express.com/pe/show...number=300-784

http://www.parts-express.com/pe/show...&vReviewShow=1


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[bentoronto]

Another reason not to do it: pasting on some bass often leads to big bad sounding bass emphasis with atrocious male radio announcers. With simple paste-on without cross-overs, no way to avoid having a big lumpy upper bass.

You might start by finding out what is coming out of the sub jack - you might find it is crossed-over at 12 dB/8ave from 180 Hz. Easy enough to get free frequency tones to use as input and possibly put them on a CD. Various ways to measure what is coming out. That should be Step One. No way to work by ear.

[Moondog55]

Which NAD pre-amp is it?/
Just asking out of curiosity

[motosapien]

Originally Posted by Moondog55

Which NAD pre-amp is it?/
Just asking out of curiosity

It's a C165 BEE

The speakers are full range coniston^2. They give good base, the drivers FS is 65Hz but the vented cabinets help them go lower of course. This has been an education. I can see why MJK's open baffle set up must work so well with a sub then. In reality I would probably gain little for the effort ( been there before! ).

[bjorno]

Originally Posted by motosapien

..In reality I would probably gain little for the effort...

Hi,
Not if you add an high performance OD-TL or a superior T-TQWT(an performance evolved TL-sub).
You would(IMO,IME) be surprised of the SQ enhancement, i.e. as your coniston^2 full-range drivers would apparently be unloaded from the need to produce large cone excursions at lower frequencies.

b

[bentoronto]

Whazzqt mean "apparently"?

Don't you need a 24 Db/8ave electronic crossover to "unload" the full-range speakers?