Need help understanding OB and Placement

[motrctyman]

I am very motivated to move towards the world of OB. Everything I have read tells me I will like them and the idea is very attractive.

My listening room is less than ideal in a normal setting as I am unable to move speakers very far away from the wall. However, with a simple switch of the couch, I could place them basically 15 feet from the nearest wall. My listening room is a game room on the second floor that is open to the family room downstairs which has a 22 foot high ceiling. If I were to place an OB speaker up against the cast iron railing, would it now be too far from a boundary to sound good? My seated position would be about 11-12 feet away with an open stairwell behind the seated position.

This would be for 100% music, lots of acoustic rock, Davis/Coltrane style Jazz, and female vocals like Eva Cassidy with occasional Pink Floyd/Peter Gabriel type stuff mixed in. I do not need huge bass, but know that I would probably have zero boundary gain with this setup....or am I missing the point?

I appreciate any guidance thrown my way...a neophyte that keeps his man-card in his wife's purse...

 

[Scott L]

In my humble opinion, an open baffle design does not fit in to your scheme of things,
ESPECIALLY for a novice. By their very nature, open baffles have front-to-back cancelation of bass and require massive equalization. Not a good mix for a "family" room, and certainly not a mix with Pink Floyd music.

 

[Pano]

For a satisfying OB experience, you do need some room. But you don't need huge amounts - tho your wife may argue that point. For decent bass you also need large baffle area, that usually has low WAF.

Here is a thread I started years ago with my buddy John. His OB designs (he has built dozens) are the best I've ever heard - by a long shot. Browse and search thru the thread for plenty of good info.

http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project.html

 

[motrctyman]

Pano, thank you for your response! Your threads are what inspired me to try something that I had initially thought unobtainable to me. My first one would indeed be a Manzita (or its dear cousin with the GRS 15" driver).

I have read through many threads and have seen many references regarding not enough space behind the drivers. What if there is too much space behind the drivers? Or is there such a thing?

 

[Pano]

There is, and you start to lose some mid-bass. Maybe we can get John to chime in here, he has more OB experience than I.

 

[John Busch]

OB rear wall distance thoghts

OK.... Often discussed question. Assuming a passive crossover, equal (roughly) front and rear radiation up to at least 2 KHZ, and also assuming dry wall or something with similar reflective - absorptive values, 24" is about as close to the rear wall as you can get with out significant problems. This will vary of course depending on the design. OTOH, As distance increases beyond 48" or so, the tonal balance of the speaker can be moderately effected. Like with typical speaker set up issues, a passive OB does have limitations. Several DIY builders of the Manzanita and lately the Ultra have actually put wheels under the support stand (Manzanita) and on the bottom plate of the Ultra. This allows them to store them against the wall or else where when needed and wheel them out at a distance that works for their musical tastes and domestic situation.

One thing is for sure, too far from the wall is MUCH more forgiving than too close. Too close and the bass extension disappears and mid range tonal balance is also effected. There are a combination of things that contribute, just don't have the time now to explain.

One advantage active crossovers with multiple amplifiers have is the ability to adjust the tonal balance for OB not set up at optimum distance. Active can only do so much though. Hope this helps.

 

[motrctyman]

Seems from what I have been learning today, I should become proficient with Mini-DSP (or similar) before I start this endeavor. I already have amplification, just never played with any active systems before. HHhhmmm....