I've been trying to read more about Quasi Butterworth 5(QB5) ported boxes. I can't seem to find any answers to what a QB5 actually is. I've only read that they are a bit larger than your standard SBB4 type boxes, and tend to have a bit more output around the tuning frequency, causing a knee in the graphs. I understand that an EBS alignment is quite a bit larger than an SBB4 alignment.
What is the difference between an EBS and a QB5 types of ported boxes?
I've always tried to build vented boxes about 20-25% bigger than the manufacture's recommended size because I prefer an increased output at lower frequencies. I often sacrifice the 55-100hz region because I use multiple 8 or 6.5 inch drivers for this.
thanks Brad
What is the difference between an EBS and a QB5 types of ported boxes?
I've always tried to build vented boxes about 20-25% bigger than the manufacture's recommended size because I prefer an increased output at lower frequencies. I often sacrifice the 55-100hz region because I use multiple 8 or 6.5 inch drivers for this.
thanks Brad
Satellites and Subwoofers
i.e. puts a 'bump' in the response at tuning, which is what the pioneers did, though early on it was always tuned to Fs.
An EBS is about extending the bass low enough to create a 'shelf' in the response to flatten group delay to below our perception [< ~35 Hz IME] and actually is lower in this BW than a 0.707 Qtc sealed, hence my preferred alignment long time before T/S in that it was derived from just Fs, Vas and 'voiced' to the desired 'flatness' using a cheap 25 ohm adj. pot and knowing the driver was suitable for a BR alignment.
GM
i.e. puts a 'bump' in the response at tuning, which is what the pioneers did, though early on it was always tuned to Fs.
An EBS is about extending the bass low enough to create a 'shelf' in the response to flatten group delay to below our perception [< ~35 Hz IME] and actually is lower in this BW than a 0.707 Qtc sealed, hence my preferred alignment long time before T/S in that it was derived from just Fs, Vas and 'voiced' to the desired 'flatness' using a cheap 25 ohm adj. pot and knowing the driver was suitable for a BR alignment.
GM
You could read the very paper that introduced the QB5:
"Derivation of the quasi Butterworth 5 alignments" AES journal, Vol. 42, No 5 (May 1994)
The Rod Elliot article that GM linked to is a great how-to about how to achieve one.
An EBS is simply a system with a lowered tuning. It's no longer "flat" down to the low end of the passband, but instead has a kind of shelf in the response that is lower by a few dB at the bottom of the passband. This became popular at one time because, it turns out, when a driver cone is under high excursion its Q and Fs parameters change. This change tends to increase both, which at high cone excursion will cause the tuning frequency to increases a bit and a "hump" will develop in the response just above that. If the voice coil heats up this will also cause Q to increase a bit, and this also contributes to these same effects. The humped resonance peak can color the bass sound or make it sound like there is too much stored energy (a droning on of the bass). The EBS helps to offset these changes but it will typically require a larger box to do this, but you do not need any filter network like the QB5 alignment. Since there is little data on drivers at high excursion (e.g. Klippel data) it is a bit of a hit and miss proposition in terms of designing an EBS.
I found an old post by GM where he described how to design an EBS system:
"Derivation of the quasi Butterworth 5 alignments" AES journal, Vol. 42, No 5 (May 1994)
The Rod Elliot article that GM linked to is a great how-to about how to achieve one.
An EBS is simply a system with a lowered tuning. It's no longer "flat" down to the low end of the passband, but instead has a kind of shelf in the response that is lower by a few dB at the bottom of the passband. This became popular at one time because, it turns out, when a driver cone is under high excursion its Q and Fs parameters change. This change tends to increase both, which at high cone excursion will cause the tuning frequency to increases a bit and a "hump" will develop in the response just above that. If the voice coil heats up this will also cause Q to increase a bit, and this also contributes to these same effects. The humped resonance peak can color the bass sound or make it sound like there is too much stored energy (a droning on of the bass). The EBS helps to offset these changes but it will typically require a larger box to do this, but you do not need any filter network like the QB5 alignment. Since there is little data on drivers at high excursion (e.g. Klippel data) it is a bit of a hit and miss proposition in terms of designing an EBS.
I found an old post by GM where he described how to design an EBS system:
Thank you!
Excellent. I've always wondered how to exactly build EBS alignments, but never had a formula to do so. I always just increased the box size by 20-25% over the box size recommended by manufacturer. Sometimes, I also would lengthen the port by 1 inch increments, until I found the sound I liked. I always would choose woofers with QTS lower than .36 as well.
Thank you for the link to QB5 alignments.
Brad
Excellent. I've always wondered how to exactly build EBS alignments, but never had a formula to do so. I always just increased the box size by 20-25% over the box size recommended by manufacturer. Sometimes, I also would lengthen the port by 1 inch increments, until I found the sound I liked. I always would choose woofers with QTS lower than .36 as well.
Thank you for the link to QB5 alignments.
Brad
You're welcome!
Just remembered that apparently Altec's 'X' bass motivated EV's D.B. Keele to add another 4th order BR alignment with a near full octave below Fs EBS [pg 5]: http://www.xlrtechs.com/dbkeele.com...print) - Vented Loudspeaker A Restatement.pdf
GM
Just remembered that apparently Altec's 'X' bass motivated EV's D.B. Keele to add another 4th order BR alignment with a near full octave below Fs EBS [pg 5]: http://www.xlrtechs.com/dbkeele.com...print) - Vented Loudspeaker A Restatement.pdf
GM
Here's a rather extreme example of a highly efficient, low Xmax 15" woofer with Fs: 45 Hz, Qts: 0.24, tuning @ 28 Hz in a 6.78 ft³ cabinet:
4 advantages:
- Reduced risk of over excursion with >90% of all music
- GD is pushed outside the audible/disturbing range
- Due to the high efficiency of the driver, the sensitivity at 30 Hz is still 92 dB
- Low Xmax means low excursion, which is always desirable imo.
Last edited: