SB15NRXC30-8 or SB17NBAC35-4 in 10 liters?

[jimk04]

The 2 above drivers as modeled by winisd actually shows better LF extension from the smaller driver. The SB17 would go quite a but lower but needs 16 litres or so.
I have a WAF constraint and 10 litres is my maximum.

Would the SB17 subjectively give me more 'punch' , despite what the numbers say.

I remember a quote from Zaph or Troels maybe who said you cant substitute SD and would always go for a bigger driver where possible...(was referring to 5.25")

These drivers will be used as low as they can, although I can filter out the lower octaves when listening through the Denon AVR, critical listening is straight from dac into DCG3>power amp>passive speakers

 

[YSDR]

Depends on what you mean by "punch". The larger driver in the small box may give more "kick" in the upper bass and less "punch" down low. But even possible that the smaller driver would have too much bass if room-gain is considered and the larger driver (in smaller box) fits better for a balanced sound. Depends on your room acoustics, expectations and taste.
The larger driver have more Sd, more xmax, more sensitivity and have more electrical power handling, so the overall output likely would be higher.

 

[PeteMcK]

My latest build is a 3 way with a 5" Wavecor woofer, it's in 20L, but has plenty of punch, I think most modern recordings are mixed that way. Even when I switch in my 10" subs, I get a bit more solidity & realism, but no more punch.
You can tune the box for a bit more punch by tuning a couple of Hz above what would give max LF extension, you should get a small hump of up to a couple of dB, don't over-do it though, or the dreaded 'one-note-bass' will raise its head....
If you model your drivers in Unibox, it has a feature where you can save & compare graphs

 

[Lojzek]

SB15 is a better choice given circumstances and I would consider a 4 ohm version as well.

 

[rabbitz]

I'd use the SB15 and if you don't have the drivers, have a look at the SB15NBAC as it's a better performer even though the SPL may be lower.

I've played with under size 12 litre boxes with the SB17MFC and MW16P and not ideal. A SB15MFC in 8 litres gave better bottom end performance and a more balanced presentation. In other words you are better using a driver more suited to the volume you are after.

PeteMcK's comment on the port tuning is spot on for smaller drivers and the hump makes the speaker sound more balanced. Bagby made some comments on this and Troels has a good article on vent tuning and generally I use a port length around 0.7 x the calculated size which is similar to his thoughts.

 

[jimk04]

Thanks for all the insightful replies and I shall stick with the SB15NRXC30-8 that I have here. Makes sense. I went for thr 8ohm just to give me some lee way should I end up with too low an overall system impedance if starting with a 4ohm.

Playing with the tuning, 30Hz versus 50Hz, would you go for the 30Hz flatter curve or add the small rise at 100Hz or so from the 50 tune but loose some output from there down.? I guess this can be trialled with port lengths.

 

[fatmarley]

Jeff Bagby used it in roughly 8ltr in his Piccolo. The AVI DM10 was about 5.5ltr and Audio Excite Kensho 2 was about 10ltr.

I'd play with port lengths for final tuning (to suit your room / ears)

 

[celef]

i would go for the smallest driver possible that still give you the low end response you want

 

[PeteMcK]

go for the small hump, it's pointless to try to get 30Hz from a 5" driver

 

[jimk04]

Wise words.....thanks again

 

[celef]

30hz is easily done with a 5" driver, just choose a woofer with characteristics that suits the box and tuning to the room gain

if you want to play loud choose a bigger driver, and choose a woofer with characteristics that suits the box and tuning to the room gain

 

[markbakk]

30hz is easily done with a 5" driver, just choose a woofer with characteristics that suits the box and tuning to the room gain

if you want to play loud choose a bigger driver, and choose a woofer with characteristics that suits the box and tuning to the room gain

Virtually any driver will do 30Hz. Playing modestly loud on 30Hz however is too much to ask for with normal 5" drivers. Don't forget our ears do have reduced sensitivity on the lows and only playing relatively loud will reveal any sound at all. The concept of 'room gain' at such frequencies is nonsense, response to low frequencies is totally dependent on the room modal distribution (standing waves).
Secondly, drivers have serious distortion issues playing loud, with 5" one likely will hear 60Hz instead of the desired 30. So go for 50 to 60Hz, that alone is a challenge already.

 

[YSDR]

Secondly, drivers have serious distortion issues playing loud, with 5" one likely will hear 60Hz instead of the desired 30. So go for 50 to 60Hz, that alone is a challenge already.

I think this distortion effect is more common than some may think, especially with small drivers like 5".

 

[jimk04]

I am not going to strive for the 30hz tuning despite the flat curve. I shall tune higher....50 to 55. This also has the added benefits of slower vent air speed and faster group delay....whether the latter I will hear but it cant be a bad thing!

 

[celef]

Virtually any driver will do 30Hz. Playing modestly loud on 30Hz however is too much to ask for with normal 5" drivers. Don't forget our ears do have reduced sensitivity on the lows and only playing relatively loud will reveal any sound at all. The concept of 'room gain' at such frequencies is nonsense, response to low frequencies is totally dependent on the room modal distribution (standing waves).
Secondly, drivers have serious distortion issues playing loud, with 5" one likely will hear 60Hz instead of the desired 30. So go for 50 to 60Hz, that alone is a challenge already.

room gain, nonsense?

and a 5" driver can not play without dist i hope none ever will listen to your advice

 

[Bill poster]

5" BNAC and CAC - 4 ohm in 10 litres is not too bad
8 ohm can get close to 35hz f3 but better as a 2.5 way imo

 

[Bill poster]

Don't forget our ears do have reduced sensitivity on the lows and only playing relatively loud will reveal any sound at all. The concept of 'room gain' at such frequencies is nonsense.

Not sure about that. Imo room gain can work v well with sealed designs suited to compact to medium size rooms, gives a nice broad lift without a 'hump' in bass response

 

[hifijim]

In my room, a 12 inch driver at 30 Hz needs to be displacing about +/- 1 mm for me to detect the sound. I don't believe that a 5 inch driver can produce useable 30 Hz energy unless the room is very small (i.e, an automotive interior, or a bathroom).

 

[markbakk]

room gain, nonsense?

and a 5" driver can not play without dist i hope none ever will listen to your advice

Well, give me a physical description of sound propagation that leads to your claimed 'room gain' at low frequencies then. And don't bother trying to lecture me on 4π, 2π or π radiation fields. Those are all true, but in acoustics modal behavior of relative small listening rooms for home audio is dominant by far. That knowledge, in turn, leads (me at least) to other conclusions on the possibilities of 5" drivers than yours. I take into account one has to tame the modal response, e.g. by placement, EQ-ing or multisub-approach, maybe you do not.