First time OB builder

[Kjeldsen]

I have heard 15" classic dipoles (Dali Skyline2000 with low Qt Cerwin Vega woofer, two scanspeak 4 inch and one meter ribbon ) in a room with around 40 sqm. They were around 2 meters from rear wall. I didn't miss any bass. It was not extremely loud or low, but still enough to satisfy most needs. I'm planning to do a fullrange OB with 4 pcs. of 10 inch peerless woofers per speaker (8 woofers all together).

In a normal room and no need for very low bass below 35-40 Hz, 18" should be fine.

[Silent Screamer]

Guess nothing stops me just adding more drivers until I feel I have enough...

[StigErik]

Good point... but some of us never stop....

Dual 15" or single 18" will be able to get good bass down into the 35 Hz territory, and that is fine for almost everything and everyone. But if you want to go an octave lower, remember that it takes 8 (eight) times as much cone displacement.

[Silent Screamer]

Thanks I'll keep that in mind.

Considering for the best part of a decade I have been listening to bass through 4 x 6.5" (18W Revelators, 2 in each Cremona) 4 x 18" is likely to be a big step up.

[ansepe74]

Have been looking at both your and Pass' "slot-bass" design.
And i'm considering i hard. But more that instead of making the baffle wide i'm making it deep.
Have already made a top baffle for my SEAS FA22's. Just about 40cm wide and from 5-20cm deep.
This made able to get a measurement of -/+3db from 250-17500hz.

Due to this i just got a simple 200uf cap + bypass. This blends very good with my sub, so the sub is supposed to be replaced by a slot-bass consisting of 2x15 angled towards eachother, like the "***-crack". Front baffle? 60cm with walls surrounding the bass 20-40cm. The thing here is that ive experienced that bass often need more power than refinement, so im thinking of using the same speaker-rca connection as i use to my sub too feed a PA-amp with active filter to use on these slot's...
What is your opinion?

Andreas

[studiotech]

Originally Posted by Silent Screamer

Thanks I'll keep that in mind.

Considering for the best part of a decade I have been listening to bass through 4 x 6.5" (18W Revelators, 2 in each Cremona) 4 x 18" is likely to be a big step up.

Stig is being a bad boy....

Just get the 2 you ordered and make a prototype first. Using sealed cabinet for the lowest octave or two does not really take away from the excellent nature of OB bass you can get down to 40-50hz. You want to maintain OB through the tonal region of the bass, but not necessary for the more visceral portion were you really need to move a lot of air. John K on that Music and Design site explains why it is so difficult to drive the room below a certain frequency with OB. Hence, the extreme build that Stig had to make to get there.

What concerns me now, is how high can you use the 5100. Will it be able to meet the mids? Maybe not, so you might want to think about something btw 100-400hz.

Did the dipole Raal arrive yet? We want pictures.

[siruis815]

StigErik's build is nuts - I thought that my 4 21s were enough and I'm just using a flat baffle!

[Silent Screamer]

Originally Posted by ansepe74

Have been looking at both your and Pass' "slot-bass" design.
And i'm considering i hard. But more that instead of making the baffle wide i'm making it deep.
Have already made a top baffle for my SEAS FA22's. Just about 40cm wide and from 5-20cm deep.
This made able to get a measurement of -/+3db from 250-17500hz.

Due to this i just got a simple 200uf cap + bypass. This blends very good with my sub, so the sub is supposed to be replaced by a slot-bass consisting of 2x15 angled towards eachother, like the "***-crack". Front baffle? 60cm with walls surrounding the bass 20-40cm. The thing here is that ive experienced that bass often need more power than refinement, so im thinking of using the same speaker-rca connection as i use to my sub too feed a PA-amp with active filter to use on these slot's...
What is your opinion?

Andreas

well its only wood... You don't have to do any fancy finishes to prototype the idea. Still considering it myself. Perhaps the butt-crack could be a half way compromise between a true OB and and sealed sub.

figuring I could make one speaker from the two drivers I have coming, and then compare it against a regular OB.

Edit:
Just thinking about what StigErik said about cone volume even though the slot is 1/3 the size of the driver volume the twin drivers will still be displacing the same amount of air, so perhaps it might be possible to still get low frequency with greater volume that way.

[Silent Screamer]

Originally Posted by studiotech

Stig is being a bad boy....

Just get the 2 you ordered and make a prototype first. Using sealed cabinet for the lowest octave or two does not really take away from the excellent nature of OB bass you can get down to 40-50hz. You want to maintain OB through the tonal region of the bass, but not necessary for the more visceral portion were you really need to move a lot of air. John K on that Music and Design site explains why it is so difficult to drive the room below a certain frequency with OB. Hence, the extreme build that Stig had to make to get there.

What concerns me now, is how high can you use the 5100. Will it be able to meet the mids? Maybe not, so you might want to think about something btw 100-400hz.

Did the dipole Raal arrive yet? We want pictures.

The great thing about having people like the stig in the world is how do you know where the boundaries are unless someone pushes them. I am really grateful for his efforts because even though I may not want to go that over the top it does tell you what results are possible if you do.

agree was never really comfortable going from the 12MUs to woofers. So what do you recommend for the gap between 100-1000?

RAALs will probably be a few weeks, the 5100 have already been dispatched, damn Parts Express are quick.

[ansepe74]

Originally Posted by Silent Screamer

well its only wood... You don't have to do any fancy finishes to prototype the idea. Still considering it myself. Perhaps the butt-crack could be a half way compromise between a true OB and and sealed sub.

I guess the word "surrounding" was kind of misplaced. I'm thinking about having it open in the back, just to keep the frontbaffle from being too wide.
I'm kind of novice in this trade, but my thought is that i've heard that if you want a speaker to play bass there must be a lot of "cabinet" between the on-phase (front) and off-phase (back).
The drivers would be angeled a little (30 degrees?) against each other while also playing out of the slot, while also creating a little more space to play on the back. This will also keep them from playing directly into the sidewalls, and maybe avoid "box-sound"?