DIY Audio Projects Forum

I am convener of the DIY section of the Melbourne Audio Club (MAC) Victoria Australia and decided to make the September meeting (Saturday the 6th) an OB speaker day. I had a massive sheet of 18mm particle board and with the help of a power saw, jigsaw and drill shaped the baffles as shown:

http://diyaudioprojects.com/Gallery/displayimage.php?pos=-250

Six members plus myself spent the day reviewing the speakers. I moved the boxes closer to the wall then away and closer together then apart to find the best sound from cheap drivers in an OB configuration. One of the best balances we got was with the two baffles side by side almost touching. This made the two large baffle appear like one massive baffle and increased the bass dramatically.

The mid range and tweeter appeared a little too bright so these were reduced in output. After a few hours of experimentation the final setup was (with the drivers and Xover on hand) -6db reduction on the mid range and -3db reduction on the tweeter and the baffles only 1 meter apart and toed in backing onto a 2m long glass table (same as in image). Bass was deep and weighty, mids and treble reasonably balanced. Jazz, Classical and some modern day rock sounded well. The system was powered by my valve monoblocs

http://diyaudioprojects.com/Gallery/displayimage.php?pos=-116

and Bumble Bee preamp.

http://diyaudioprojects.com/Gallery/displayimage.php?pos=-224

A mix of vinyl and CD was played.

In all, a very satisfying day if not exhaustive. Moving the baffles which were extremely heavy over a two hour period tired me out. One member liked the OBs so much he loaded them into the car to tryout with his system and a half promise to purchase if liked.

Has anyone else experimented or made some OBs? If so what do you think? At the close of the club meet I was very impressed at the slam and punch of the speakers. I made them from scratch in one afternoon for less than $200.

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Projects: "Sortilege" - 180W Tripath Class D Mundorf upgrade amp | “Mantra” - tube MM phono preamp | "Carbon” - MM phono preamp | 180W RAW Class D amp |

Hi Mark,

Sound like you guys had some fun. I'd like to try a pair of Open Baffle Speakers for myself, but right now I don't have the room. A few years back, I did get a chance to try a 20" OB subwoofer that blended in very well with my Fostex FE127E Sealed Tower Bipole Speakers. The combination worked very well and the open baffle subwoofer made some very natural and pleasant bass.

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]

I am looking forward to Nelson Pass' examination of OB. He is trying Fostex, Lowether, and Audio Nirvana speakers of all sizes in OB with his amps and will be publishing the paper this fall.
Ri

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DIY Lightspeed Passive Attenuator

An open baffle speaker system can sound very nice, open and natural. The problem with them as has been noted is the amount of space that one will require and hence they are often impractical. There are several wide (full) range drivers that can be effectively used to create a nice two way open baffle.

This I need to see!

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Projects: "Sortilege" - 180W Tripath Class D Mundorf upgrade amp | “Mantra” - tube MM phono preamp | "Carbon” - MM phono preamp | 180W RAW Class D amp |

I'm fortunate to have a 7 X 8 meter listening area. And yes the OBs could have stayed and I could have increased the WAF but I just wanted to get on with other projects. I don't think I'm finished with OBs. Maybe an 18" woofer next time!

The guy who took the OBs from the demo day sent me these comments.

"I got the OB's home and set them up straight away. My listening
room is about half the size of yours and so they were a bit awkward
and ugly:) and then they sounded at first quite "thin". They lacked bass a bit and thing is I don't have a subwoofer system. Plus I
don't seem to have the grunt of your tube monoblocks to drive them. So at first I wasn't too impressed so I went and made dinner and then
did some ironing!:))).

But after tea I sat down to listen properly. It was then that I played record after record and was liking them more and more.

Transparency, lack of box colourations and purity was very like able. They imaged very well I agree. Specifically the image is very stable.
An image does not dance around or move on it's own nearly as much as with my boxes. Piano and guitar sounded great. And a vocal record of
some female on 180gram audiophile vinyl that sounds V couloured on
my box speakers sounded brilliant.

So they were addictive. I ended up listening to them for hours last
night as well. Still sound a bit thin but otherwise seem so good.

At this stage I'd say I want to buy the bits off you as I would like to continue this experiment at the very least. But give it 2 or 3
weeks if you will as you suggest and I'll see what I think."

They are addictive. My chip amp monoblocks drove them hard and well and my ZCA also handled them well but the 6T9 amp didn't like them at all. Also placement is very critical as we found on the day.

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Projects: "Sortilege" - 180W Tripath Class D Mundorf upgrade amp | “Mantra” - tube MM phono preamp | "Carbon” - MM phono preamp | 180W RAW Class D amp |

Link to thread where Nelson will likely post info about the OBs
http://www.diyaudio.com/forums/showthre ... ost1605668

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DIY Lightspeed Passive Attenuator