My sand filled curved side walls project in progress!

[sqlkev]

Enclosure size is approximately 15.5 Liter
Sand will be filled at the bottom of the enclosure, sides, and back.
Here are some pics.

[sqlkev]

More

[sqlkev]

This is my first experiment in sand filling, so I don't expect much, just want to see how a dead solid enclosure would sound.

[sqlkev]

I'm having a hard time deciding which tweeter to use,
I have a pair of seas 27TFFC that I could use, or a pair of small heil ess tweeter.
I just took the heil tweeter out for a quick pink noise RTA to roughly see how it response, take a look at the blurry graph below

This is the tweeter just sitting by itself freeair, no baffle. Mic is 1/2 meter away held by my steady hand. It's unbelievably flat from 3khz all the way out to 20khz, much much better than most tweeters I've played with.

[sqlkev]

Lots of view, but no comment


Slow progress, but I wrapped the curved side panels with tempered hardboard. It was a bit of work until I remember that I have a few sets of tie down straps. Much much easier with them.

[sqlkev]

The drivers being used are the seas 27TFFC and the dayton rs150. Test crossover point is 2.21khz with 4th order. Ports are dual 2" x 8", it comes out to be around mid 50s.

I'll order some crossover components and start tweaking next week.

BTW, what do you suggest for the sand filling? Should I buy the sand bags from Home Depot or should I just go cheap and go to the beach?

[lufbramatt]

The bass enclosure of my last project used sand filled walls- 12mm plywood inner shell (C-shaped, laminated from 1.8mm thick aero ply) and a 5mm thick fiberglass outer shell with an approx 20-30mm gap between that was filled with sand. This way i could get some really nice compound curves on the outer shell.

The sand made quite a big difference listening to the speakers filled vs unfilled, with the bass becoming a lot tighter and punchier with the walls filled, worth trying but not sure if its a big improvement over a ridgidly built "solid" cabinet. The weight of the whole speaker is well over 40kg though

For sand I would use the bags in your local DIY/garden center meant for kids sand pits normally called "play sand" here in UK, then make sure its all dried out properly by either putting in metal trays and leaving int he oven on a low heat for a while, or just air drying it. You might get mould problems if its damp. Some sort of fungicide might be a good idea too.

In my speakers I glued in a short (15mm) length of 20mm inside diameter steel tube into the back of the external shell into which I can insert a bicycle handle-bar end plug, thsi lets me top up the sand as it compacts down over time and leaves an air space at the top of the speaker.

Good luck, matto

[lufbramatt]

Bar end plugs like these in case you wasnt sure: http://www.ukbikestore.co.uk/acatalog/info_SPT152.html

and another foto of one of the finished speakers:

[sqlkev]

Matto,
Thanks for the input of your experience, I don't really know what to expect from this experiment. The woofer is only 6", so I don't expect too much bass out from it. I'll try to break in the woofers for a few days and will fill the dry sand after to see if the bass improves.

I really like your project. Just curious, what drivers did you use? I'm spotting the seas TBFG? xls woofer and vifa mid?

[lufbramatt]

Originally posted by sqlkev
I really like your project. Just curious, what drivers did you use? I'm spotting the seas TBFG? xls woofer and vifa mid?

Thanks

spot on with the tweet, mid is a seas MCA15RCY and woofer is a Scanspeak 8555-01.

The woofers really shift some air for an 8", X-max is about 13mm as far as i recall, but even at pretty loud levels there is hardly any vibration present on the outer walls of the enclosure. I was amazed how loud it was when i pressed my ear up against a mission 782 3-way speaker with a much smaller 6.5" woofer how much of the sound is transmitted straight though the walls- in that case 30mm MDF- and its much less with the sand filled walls.

The mids were something of an unknown quantity when i got them as they were quite new, but some people like troels graveson have subsequently measured them and really rate them- which i would definitely agree with, they are very clean, natural mids.