FR sealed or OB for FAST?

[KaffiMann]

Hello.

Have some different drivers available for a leftover build for a living room. The speakers will be about 2.5m away from back wall if left standing, or they could be placed up in the ceiling aiming down.

I've simulated some TQWT for bass solutions, and the seemingly optimal construction for phase and freq response would make a small sealed volume between the woofer driver and the "port". Perfect for a small FR. Looking at some Tang Band 1139SI, which is damn near spot on the same sensitivity of Seas FU10RB H1600-04, would leave a sealed volume of 2,128L between the woofer and port! The phase is even and predictable to over 1khz, so would be relatively easy to xo. Very tempted to put the Seas driver into those ~2L volume and xo at around 400hz, or is it better to mount it on top of the enclosure a la LX mini and xo around 7-800hz?

Aaaaahhhh Decisions decisions......

Or should I go for a different more sensitivity oriented FR driver and use the Beyma 8BR40 in a similar solution? The boxes would be bigger and ruin a potential aesthetic look to some extent. Would gain about 5db/2,83V and with 8 ohm as opposed to 4 ohm. Different roll off but little difference other than lower acoustic impedance peak on the beyma, so potentially better roll off.

Also very tempted to make boxes out of pine/oak combination or maybe just "safe it" with ply.

So:
1. Make 1 box with both drivers inside, FR tightly between woofer and "port".
2. 1 box with woofer inside and FR on top.
3. two subs and two mini tops angled from the ceiling.
X. Ignore possible objections from the mrs and "go large". *again* Almost more tempting to do a mini build for the fun of it.

 

[jimbro]

I'm a little confused by your post. Do you already have some drivers?

 

[sreten]

Hi,

As a starting point The FR should be less sensitive than the
bassmid by the amount of BSC used. Then x/o 1st order series
at the baffle step frequency. L-pad on the FR is an option.

f3 = 115 / WB (where WB is the baffle width in meters)
f3 = 380 / WB (where WB is the baffle width in feet)

rgds, sreten.

 

[KaffiMann]

I'm a little confused by your post. Do you already have some drivers?

Yes.

This would mainly be about utilizing "leftovers"

Sreten:
Not sure why, but on some projects I do not like bsc, on others it's a necessity. So that is a decision I will evaluate on a later stage. Thank you. Either way, part of my leftovers are 1 extra 2*4 minidsp, not the ultimate solution, but it will suffice.

So no votes for ob FR and no votes for sealed FR?

 

[Godzilla]

I vote for both!

 

[planet10]

Each kind of FR "enclosure" has its own benefits & drawbacks. Personally i like aperiodically damped midTLs in an attempt to absorb the entire back wave.

Godzilla has a number of sets of midTweeter OBs which he likes. A sealed enclosure probably allows the midTweeter to be extended the furthest on the low end, and the 2nd degree rolloff used as 2 poles in your XO.

dave

 

[jamesecox]

Hello.

Have some different drivers available for a leftover build for a living room. The speakers will be about 2.5m away from back wall if left standing, or they could be placed up in the ceiling aiming down.

I've simulated some TQWT for bass solutions, and the seemingly optimal construction for phase and freq response would make a small sealed volume between the woofer driver and the "port". Perfect for a small FR. Looking at some Tang Band 1139SI, which is damn near spot on the same sensitivity of Seas FU10RB H1600-04, would leave a sealed volume of 2,128L between the woofer and port! The phase is even and predictable to over 1khz, so would be relatively easy to xo. Very tempted to put the Seas driver into those ~2L volume and xo at around 400hz, or is it better to mount it on top of the enclosure a la LX mini and xo around 7-800hz?

Aaaaahhhh Decisions decisions......

Or should I go for a different more sensitivity oriented FR driver and use the Beyma 8BR40 in a similar solution? The boxes would be bigger and ruin a potential aesthetic look to some extent. Would gain about 5db/2,83V and with 8 ohm as opposed to 4 ohm. Different roll off but little difference other than lower acoustic impedance peak on the beyma, so potentially better roll off.

Also very tempted to make boxes out of pine/oak combination or maybe just "safe it" with ply.

So:
1. Make 1 box with both drivers inside, FR tightly between woofer and "port".
2. 1 box with woofer inside and FR on top.
3. two subs and two mini tops angled from the ceiling.
X. Ignore possible objections from the mrs and "go large". *again* Almost more tempting to do a mini build for the fun of it.

Here is my vote.....

 

[KaffiMann]

Godzilla: And even more! But this is for the living room, want to surprise the mrs. for once and building something compact. She will be caught very much off guard at that.

Dave: Mmmmm... Seeing as there will be very few parallell sides in the sealed volume I take it that's your vote? Have some good (3cm) loose wool felt, and I can mix in a bit of polyfill and glue 3mm felt padding on different spots.

James: Yes, I have some Beta 15A, but not the Betsy. The Beta 15A is currently mounted to a 3cm thick oak baffle with Hawthorne Audio 10" Sterling Iris. In a format much like what you proposed. Would like something slimmer for the living room.