The loudest noise from a cabinet generally comes from resonances within the passband of the drivers (cabinets without resonances in the driver passband are an exception). Bracing changes the stiffness and mass of the cabinet leading to different resonant frequencies and resonant shapes. However, it doesn't change the magnitude of the resonance because at a resonance the forces due to stiffness and inertia/mass are 180 degrees out-of-phase and cancel. That's what resonance means. The size doesn't matter because they cancel. What reduces the magnitude of resonances is damping. The damping from wood and the various joints and fixings in a cabinet is small leading to high Q resonances typically of tens of dB in magnitude. A modest amount of effective damping can reduce those high Q resonant peaks by ten and sometimes tens of dB. Since these are generally the loudest sounds radiated by the cabinet the cabinet becomes ten and sometimes tens of dB quieter.
If I recall correctly the KEF paper shows bracing raising the frequency of the main problematic resonance but leaving the magnitude unchanged whereas damping reduced it by 30 dB or so. The unchanged magnitude of the resonance due to bracing speaker walls is shown by pretty much all measurements or simulations since it is simply reflecting the physics of what increasing wall stiffness does. The amount of reduction shown by KEF due to damping is larger than typical but they had only one troublesome resonance the shape of which they understood and targeted effectively with a larger than typical amount of damping.
Note that increasing stiffness can make a speaker cabinet quieter if the physics is understood and you know where and why increased stiffness will help. Engineers at the larger established speaker companies like KEF possess this knowledge whereas most DIYers don't because they haven't studied engineering. They look to what has been done in the past, what other DIYers say and do particularly those with websites, hand waving arguments based on a range of dubious premises, what feels right, etc... and come to a general view that bracing the hell out of everything will make a cabinet quieter. It doesn't but the difficulty of measuring the sound radiated by the cabinet, the difficulty of simulating it, the difficulty of understanding the physics (and often a lack of interest in doing so), plus the fact that the sound radiated by a reasonable cabinet is small anyway has lead to this view persisting. I do see the odd post from those with understanding but they tend to be swamped by the larger numbers with enthusiasm. Given it is a hobby one can probably make a pretty good case that enthusiasm should trump knowledge.
About 25 yrs ago I converted a pair of Mission 754F's (large floorstanders)into TL's which included opening up the rear upper half of the cabinets and fitting internal panels to form the line which exited below the bass/mid driver (Seas 18w 8542) and Morel Mid. A tweeter (Monacor DT25N was mounted at the centre of the mid/bass on metal suspension frame(!) I appreciate that many sins were committed in doing this - but it
s still in daily use nearly a quarter century later!
And still sounds great!
For anyone to add bracing to a ready built ProAc speaker would have to cut off the front baffle remove the bitumen add the bracing then replace everything back ,
Then have to reveneer it .
It would sound tighter but not as musical as it was before because the cabinet would be stiffer
Have you got a pic to share ?
18w/8542 is a Scanspeak paper coned woofer as in the Proac studio 100
and is similar to the bottom woofer in my Proac DT8
the below is a pic of the bottom woofer in my Proac. Although I can’t find any data on it.
Seas CA18RCY-C is a custom chassis made for ProAc with a bigger lip to accommodate the Proac logo
You can buy the standard CA18RCY with the standard lip for around £70 Proacs would be £300 ish
They both sound the same just made to look different
CA18RCY - C is also in the studio 140
Add another layer of bitumen and line it with baf wadding and you’ll have a ProAc Response series speaker
The DT8 is a response series.
im confused.
can you explain?
and wouldn’t the extra layer of bitumen alter the volume of the cabinet and change the sound?
much appreciated !
Which of these woofers is it the same as from SEAS?
https://www.madisoundspeakerstore.com/approx-6-7-woofers-seas/
https://www.madisoundspeakerstore.com/approx-6-7-woofers-seas/
i don’t think they need additional bracing.
as with many other here I just thought I can make them perform even better.
if that makes sense
Planet10
would changing out some of the lining which now is some sort of poly foam , with wool felt make for cleaner mids and highs?
something from here?
https://www.mcmaster.com/wool-felt/...alPath=wool-felt/firm-felt-sheets-and-strips/
here are a couple pics with the poly foam lining in the speaker currently.
would changing out some of the lining which now is some sort of poly foam , with wool felt make for cleaner mids and highs?
something from here?
https://www.mcmaster.com/wool-felt/...alPath=wool-felt/firm-felt-sheets-and-strips/
here are a couple pics with the poly foam lining in the speaker currently.
Depends. Foam is usually used because it is consistent and low kabour to install.
Some ML-TLs are just lined, some with volue fill. All those i have done have been volume fill with either teased UltrTouch Insulation or well teased Acoustastuff.
You can tune the response to suit the room, placement and your taste. They should both also be considerably better at killing mid/top frequencies.
dave
Some ML-TLs are just lined, some with volue fill. All those i have done have been volume fill with either teased UltrTouch Insulation or well teased Acoustastuff.
You can tune the response to suit the room, placement and your taste. They should both also be considerably better at killing mid/top frequencies.
dave