Sorting my completed DIY $179 Accusound Sub Kit

[TIGERLEE]

I've just completed my first sub build after joining this forum 6 months ago, and chose to build a low cost unit at first. I wanted to get my workshop equipment and woodworking skills reasonably set with a sub build and then progess on to a serious pair of floorstanders later this year. This is just my second post, I visit the Audioholics forum almost daily and enjoy the forums diverse talk.

My first build, taking an Accusound kit purchased off EBay $179 AUD, amp plate and driver. Accusounds basic enclosure specs supplied are as a front firing build. Well I built my sub as down firing unit, an adventure in the great sub neewbie learning curve. I already have a Warfedale downfiring sub that I'm really happy with. Naturally I contacted Accusound to obtain the detailed driver specs to refine my build, amazingly they replied that they do not provide this information for their sub kits. Here is the EBAY page

You can view my build process here: DIY Subwoofer Build - a set on Flickr

INFO: On/Off switch moved from amp plate to front of unit for ease of access and LED indicator light too. Costs, Driver & Amp $179, $40 MDF, $12 Feet, $12 vents, $38 paint, 25mm thick MDF. I'm pretty happy with the result, considering the minimal money involved.



The only specs provided by Accusound that I had to work with were "Recommended Enclosure : (Internal dimensions) 415H x 330W x 380D (mm) 2 x 120mm x 58mm Ports"

Not having the driver specs that I could have tweaked the box and ports using a stock online calculation spreadsheet I'm looking for some advice as to whether changing the following (with no specs) would help improve the sound quality.

I'm getting satisfactory volume, but I'm not hearing clean punchy base, it's somewhat "boomy" and varying the amp plate frequency control gives only a small change in the base tone range. Would changing the following tune this sub for the better?

• Damping standing waves more effectivly by loading up the box with much more fibre insulation, currently walls lined with 15mm flat fibre. Should I wrap the ports with fibre?
• Reducing the leg height, currently elevated 100mm from the floor. Closer to the floor, does the driver feel the "floor load" and react?
• The two ports seem to perform their function, lots of free airflow and no choofing. Would changing the length help?
• There are no internal braces, the box is made from 25mm thick MDF, glued, screwed and sealed, seems to me there is no panel resonance at all. How do you measure resonance, is there a simple test?
• Does the driver need a run in period "to be trained" to work or find efficency in the new enclosure?

Or does a $179 sub kit have its limits and it won't get better with some changes?

Cheers

Tigerlee

 

[manwithnocape]

congrats on trying your hand! and you did a nice job. it looks really good.
yes, a 180 buck kit is very limited, do not expect mind blowing sound from it. the reason why is because the driver is most likely quite low efficiency, and in order to get any sound out of it from a small amp, the enclosure has to be designed to accent, or emphasize, a specific frequency. also, the port design is most likely not as "dialed in" as it needs to be to achieve tight and punchy bass. what you are hearing is a combination of a few problems.

lack of bracing.
high Q design enclosure
low efficiency driver
poor port design (designed for more volume and not clarity, it may not choof but it may not be optimal)
mdf material. lacks in stiffness, and a non-stiff box will do what? ____________ (answer here)

because of the design limitations for a 180 buck unit, i wouldn't throw a whole lot of time into it. maybe throw some acoustic seal in all the corners, some more dampening, and thats about it. there are diy forums dedicated to sub building that you can learn a ton from.
tight and punchy will always come from a sealed box and a well designed ported box, but if the port design is bad things go wrong in a hurry.

best of luck in your future sub building!

 

[TIGERLEE]

[/COLOR]ThanksManwithnocape, a super reply.............

I really appreciate you taking the time to reply with some ideas in tweaking mynew sub build.

I have taken a first step by loading up the enclosure walls with very thick anddense fiberglass insulation material. The change has improved the tightness ofthe sound and reduced the boomy elements. In fact varying the frequency controlnow shows some adjustment effect and I can now position the sub frequency tocompliment my Wafedale floorstanders. The driver's movement seems morecontrolled when the volume is increased and it doesn't break up and distort asit did. So far it's much better. I'm going to experiment by adjusting the legheights and port lengths. I'll keep searching to find some driver specs, if Ido, I will change the enclosure dimensions to meet the specs.

Thanks & Cheers

Leethal

Marantz NR1602 AV Receiver
Warfedale VR300 Floor
Warfedale VR10 Sub
Warfedale VR-S1 Surounds
Warfedale VR-C1 Centre
Accusound 200w 12" Kit Sub work in progress
Marantz TT-221 Turntable DD
Sansui C-77 pre amp
Restoring - Sharp VZ-3000 boom box

 

[manwithnocape]

nothing wrong with that approach at all.

if you take the points of learning and apply them, you will always be better off.... and sometimes the best learning is done through experimentation. try to apply this point: a speaker will only sound as good as the rooms' acoustics. if you feel inclined, try treating your room with some wall and ceiling treatments. there are plenty of ideas on line, and the overall experience of listening can be enhanced greatly.