Enclosure(s) upgrade for 2 x Midbass drivers

[suparub]

Hi folks ! I'm opening a new thread following this one Ported Sub to Tapped Horn. Few questions before starting as I don't want to mixup everything, I hope it's ok regarding forums guidelines.

So got myself a pair of 2 x RCF MB12N351 and have been building 2 vented box for them. But since I get rattling noise (goddamn PVC port) and limited SPL, I would now like to improve their efficiency and so on build something new. Their aimed frequency range use is from 40/50Hz to 1/1.5Khz. Some questions to direct me in the best path :

1 - What are the pros / cons having an enclosure with 2 midbass drivers together VS a dedicated one for each ? I believe there is a question of power and sound spatialization.

2a - Any idea of a dual midbass driver I could adapt ? I have seen designs like this one :


2b - Any more classic (wood based only) ported design I could adapt ? I was thinking of simple designs like this one :


3 - How can I adapt these drivers to plans/design I find online ? If not possible, too difficult, how can I be sure that the driviers will work with them ?

The drivers are neodymium based and are supposed to be ultra efficient in small enclosures. I have also a limitation of weight and size so the lighter + smaller, the better ^^
The drivers are 8ohms and I use them in parallel wiring in any cases.

- Here are the drivers specs : https://service.rcf.it/c/document_l...22-200b-48e3-8fde-ccba0805410f&groupId=216492

- Here are the vented enclosures (the two at the bottom) I have built already via BassBox + their specs:










Thanks !

 

[PeteMcK]

I think you're trying to get too much out of them... I'd say use them in sealed boxes for midrange only, say 150 - 1500 Hz. With such a low Qt (.2), in a vented box they're only going to be usable in a EBS alignment, so the low end will always be dropping off anyway.

 

[suparub]

Thanks for the input Pete, I haven't thought about that and it would clearly makes the enclosures lighter. I'm also not loosing too much DBs compared to the vented version ( 2.55DB of difference maximum at 150Hz)

Here are the sims ( I just read your signature so added the impedance ones too

RED = vented / YELLOW = closed

 

[suparub]

Hi Again everyone I'm trying to decide between a building a pair of sealed box or a pair of THAM12 for these drivers. Anyone know what DB / SPL difference I would get comparing the 2 types of enclosure with the RCF mb12n351 ?

 

[picowallspeaker]

Well, everybody knows that at each halving of solid angle radiation you get +6dB

 

[suparub]

Well, everybody knows that at each halving of solid angle radiation you get +6dB

I guess I'll understand this soon XD For now, a bit out of comprehension at my level

 

[GM]

A fundamental of acoustics, so assuming both are in 4pi space, the horn will in theory be up to +18 dB over some portion of its BW: http://image.slidesharecdn.com/pls2...ers-and-how-to-do-it-13-728.jpg?cb=1333091757

That said, there's losses, huge size difference, power handling, etc., so will need to sim them to compare.

GM

 

[suparub]

Alright thanks for that GM, any help how I could sim-compare ?
THAM12 vs Sealed BOX
Driver : RCF MB12N351 - 12" Mid Bass

Sealed enclosure :
Total volume 18 liters
VB : 16.73 liters
Dimensions : 376 x 376 x 197mm

 

[suparub]

Update : Got my answer from freddi on another thread

 

[suparub]

Alright, I am now debating on the choices of the mid-range drivers. Regarding the fact that I'm interested only in the frequency range from 150Hz to 1Khz, which driver will sound louder in this range ? I'm curious how to do the calculations in advance instead of going to a shop. I know also that the sensitivity is per Watt, but I also know that most of the Watts are needed for the low frequencies (which I will not use in this case). No problems about the amplifier, it has much enough juice to power them both (I'm applying a limiter on my dsp in order to not burn the drivers)

- RCF MB12N351 - 12" Mid Bass 99 dB sensibility / 650W RMS
- RCF MR10N301 - 10" Sealed Basket 102 dB sensibility / 300W RMS

As don't plan to use the MB12N351 for bass frequencies, I still wanna figure out if they will sound louder in the midranges than the MR10N301. Hope I'm not too much off topic from the original post ^^

 

[GM]

Flip a coin, only ~0.4 dB difference on paper.

Eff. conversion: Sensitivity in dB = 112 + 10 log [efficiency]

Power conversion: peak dB SPL = sensitivity + 10 log [power]

GM

 

[suparub]

thanks GM, learning everyday more

 

[David Morison]

On a wide baffle (ie in half space) the MR10 is already -10dB at 150Hz even before applying any crossover filters - which may not be as useable as you need. On a narrow baffle, you won't be fully in half space, so it'll be even further from flat at that low a frequency.
If solid output to 150 is important, the MR10 is not the right driver for you.

 

[suparub]

Thanks, the Idea is to start them at 200hz actually