Man finds Naim electronics and Naim speakers give great sounds!! Shocker!! (SBL question)

Don't know about SBL's but Ovators with my Naim also work 'quite OK' 

Perhaps something to do with a fact that those speakers were tuned using specific boxes?

I believe the PAR is designed to control the frequencies that escape into the lower box, which reinforces the bass. The idea is that the midrange 'sees' the small box whereas the bass 'sees' the big box. 

Thanks both. Ok, so the drain grid is the PAR it seems. And it only allows the lower notes into the bottom box. I see.

C.

Well, as far as my limited knowledges of acoustics reach, I know that what differentiates frequencies, from a physical point of view, is the different wave length. Then, of course, there is amplitude, which is a variable while wavelength is direct function of the frequency. So, if I understand what you're referring to (the 'filter' on the bottom of the mid box), what I don't understand is how it 'works' with relation to frequency: can it be a sort of mechanical low-pass filter? We must also consider that the air volume inside the lower box has a relation with frequency, so the lower box's ability to reinforce lower bass instead of mids has to do with its dimensions. The 'drain cover' could also work as a sort of inner reflex port, designed to do exactly what it does, permit bass enhancement.

So much for my technicality...

M

(Corrections with manners please)

Christopher_M posted:

So how do SBLs work? Why are they so good?

I know there's what looks like a small drain cover in the bottom of the mid box. I suppose I'm asking what is a precision acoustic resistance? This is the phrase I've read here. Please assume no more than O-Level physics (1977) grade C in any replies.

Thanks and Best, Chris

I have never seen or heard SBLs, but I can explain the "drain cover."  

The separated box concept is a very clever design compromise, whose practical and successful implementation is made possible by that drain cover.  The concept is to load the mid-woofer driver with a small box at mid range frequencies and with a large box at bass frequencies.  The woofer is mounted in the small box, which minimizes internal acoustic resonances (which are at higher frequencies due to the small internal dimensions).  This avoids the "boxy sound" that  often plague large box two way systems. The large box is coupled to the small box by an port, which is necessary to allow a low resonant frequency for the woofer, enabling its adequate bass response.   The diameter and depth of the port is tuned to the box volume, analogous to a bass reflex port.  It acts as a low pass filter, so that the woofer "sees" only the small box at higher frequencies, but becomes loaded by the combined box volume at low frequencies.  (This is a simplified description).

The aperture, or port, between the two boxes forms a resonant coupling between the two boxes, and would result in an irregular response with excessive ringing unless adequate damping is provided for the coupling port.  An acoustic resistance is necessary.  Casual attempts at creating acoustic resistance usually result in PRaT-destroying nonlinear behavior.  The "precision" acoustic resistance is made to avoid these defects and provide a tight, clean bass response.  So, the "drain cover" is a carefully and cleverly crafted solution to implement the dual-coupled-box design.

Charlie

Thanks Max and Charlie. Charlie, how you managed all that without having seen a pair is beyond me!

Cheers, Chris

I have seen photos, heard descriptions... and I am a loudspeaker designer (of sorts).

PS: sorry so late - my internet has been down all day.  :0(

Must say that when I unpacked mine from the boxes I could only admire the engineering behind them, as I wrote to may friend Max at the time. When I saw the drain cover, I knew I was looking at something different and special but I didn't know what it was all about. So thanks all.

Chris

How would you rate your SBLs compared to your old IBLs Chris. I think I'm heading towards Isobariks when our building work is finished but it's years since I've heard a pair of SBLs. I know they're all different beasts but I'd be interested in your reflections as a previous IBL user.

Regards

Mark

Hi Mark,

IBLs were the lover I couldn't live with. But also the lover whom I'll never forget.

SBLs have most of their speed, plus enough weight in the bass so that digital sources can sound good too. A compromise I'm willing to accept.

I've heard Isobariks so few times and so long ago, I can't make all that meaningful a comment. Except that if they had really turned my head, I'd have remembered. The fella who does the IBL and SBL foams also does foams for 'bariks btw.

Best, Chris

I went from Active Linn Saras (using 32.5/HiCap x 2/NAXO 2.4/4 x 135s) to Mk II SBLs.  The Saras were very good indeed, but the SBLs were even better, and the bass was/is much better balanced.  I listened to a pair of SL2s when they came out, but stayed with my SBLs - I still own them (in the living room system), but now they have a 52/53PS driving them.

Interesting Dungassin, high praise. I've sometimes wondered what a NAC52 and SC could do here with my NAP200 in my small room.

C.