Questions like this are usually best asked at DIYaudio, but I think this refers to the Qtc. Q is unfortunately an overloaded term in speaker and filter design.
The charts here will probably help.
What does Q mean in speaker specifications?
I have never seen that listed before on any speaker. Can you explain what the Q means on these Falcon speakers? THX
Falcon Acoustics is pleased to announce the re-introduction of the Falcon Acoustics Q7 “Complete@Home” Loudspeaker system. Designed by Malcolm Jones and sold by Falcon for many years, the updated Q7 features the same Falcon B110 and T27 drive units as used in the Falcon LS3/5a in a specially extended LS3/5a-type cabinet to produce an optimum Q=0.7 system with extra bass compared to the LSA3/5a (+2dB @ 50 Hz). Factory built options supplied built by Falcon, fully checked and tested are available.
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Sorry about bringin this up after a year or more. Question regarding Q and the mass of a passive radiator. I have two sets of very large floorstanding full-range speakers, VMPS Super Tower and Super Tower III, designed by the late Brian Cheney. Each speaker uses a 15" downward-firing passive radiator. Morite putty is attached to the PR, and the end user is supposed to add or remove it to achieve the desired bass response. I desire a low Q, tighter, flatter response. Generally speaking, would this mean more putty to increase mass or less putty to reduce mass? The instructions discuss what to listen for, but I'm interested in the more theoretical explanation. |
@yogiboy meaning of Q is Quality Factor (ref: Q Meaning in Speaker). For this reason, it also means quality factor for the speaker. I’m adding a few more references to this.
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QMS, QES, QTS, QTC QMS tells us how well a speaker is damped in the mechanical realm or suspension QES tells us how well a speaker is controlled through its electro-mechanical side, magnet & voice coil QTS is a summary of the 2 combined.... QTS helps us easily judge if a driver belongs in a sealed or vented/ported box. QTC is the final system Q after it is in the box. .707 is considered a perfect rolloff. .8 to .9 will give you a warmth or small rise in the lower region, Over 1.0 can get to be sizeable rise, but not necessarily, some drivers sound reasonably good with the rise in bass. Below the .707, its just the opposite of being above, the lower below it is, the leaner low frequency is. I hope this helps in some way. Tim |
They do that in electronics. There is a filter before the subwoofer amplifier that adjusts the bass behavior in a very similar fashion to how a woofer behaves with different sized cabinets. It’s just some basic equalizer circuitry. Great flexibility but requires your amplifier and driver to have plenty of headroom so you don't over drive it. They also make some speakers you can convert from sealed to ported AND have a Q control. In all cases the idea is to give you more flexibility and help the subs adapt to different rooms and placements. |
To the point on sealed subs, I noticed one HSU model allows one to adjust the Q. Not sure how it all works but seems interesting. Still digesting this concept, thanks to all for your explanations here in this thread:). @yogiboy, that was fast! Congratulations, can’t wait to hear your impressions on this speaker. |
It's been a long time since I read the original papers, and it's possible the nomenclature has changed or I misremember. What I recall is that the total (electrical & mechanical) Q of the speaker was called Qts and the final damping factor when mounted in a cabinet was Qtc. I do prefer simply Q for everything. I never liked c representing both driver and box and would even less for just the driver. |
@petaluman 1++. This is very important for the design of sealed enclosure subwoofers. For the reasons petalumen explains, ported subs are inherently very poor performers. As was also mentioned the Qtc of a sub can be easily adjusted by changing the volume of the enclosure. With the advent of digital speaker control and the availability of high powered amps, I want the best transient response I can get given the available power so I shoot for a Qtc of .6. With speaker control and power you can easily force a good large driver down to 15 Hz in room. Speaker control (room control) can also take the "hump" out of small loudspeakers and provide crossovers so you can integrate them nicely with subwoofers. Frankly, the only way to mate subwoofers with any loudspeaker at the state of the art is with digital signal processing. |
I like the answers here. Very good. I'd like to add that in my DIY towers people are often amazed that I get so much bass from what appears to be 10-inch drivers, then I pull the grills off exposing only 8-inch drivers. This effect that everyone is talking about is simply utilizing the resonate freq of the enclosure to lift to the bottom end. If done well, you will not notice the rise but just experience a steady bass volume as the Frequency gets lower. And as one person mentioned what he called 'Stored' energy in the cabinet. Though this is a component it is ONLY a component. |
I am on the fence on buying them. I would love to give them a try. I’ve owned many LS3/5A type speakers including the Harbeth P3ESR that I prefer over the other ones that I have owned! BTW, those Falcons ( kit ) look like a real bargain. I have also owned the Falcon IMF-100 transmission line and they was real nice! I sold them to my nephew and he loves them! |
This is all great information. You learn something new everyday. @yogiboy are you planning to order the Q7s? |
The system Q of driver & cabinet has been used as an essential guide to a speaker's bass quality since the seminal work in modeling bass alignments using filter theory was done in the late 50s-early 70s by several people. The parameters identified are typically called the Thiele/Small parameters, Q itself is unitless and represents the damping factor (tendency to return to rest). There are several Q values (speaker electrical, speaker mechanical, box) in modeling a driver & enclosure, but speaker makers (as opposed to driver makers) will typically only use the Qtc of the bottom end, which includes the speaker and enclosure. In general, a Q of .5 is critically damped, with no resonance & ideal transient response. A Q of .707 is considered maximally flat, with a 3 db rise at the system resonance. Higher Q values result in progressively more boost & poorer transient response. Note that I'm only talking about closed boxes here. All I can tell you about bass reflex is that transient response is always worse and the roll-off below resonance is 24 db/octave vs 12 for closed boxes. And don't get me started on those port plugs! This is the measured response of the LS3/5A, according to Hi-Fi World. As speakers go, it doesn't look bad at all. The bass alignment can be seen in the steady climb to the left below 300 hz & peaking around 100.
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Dyna: Do you have documentation for the 1.2 "Q" measurement? Having owned Rogers Ls3/5a's for 1979-1986 I find that spec hard to comprehend (considering the cabinet size). Yes, they did had a mid-bass hump - making them difficult to properly mate with subs (including their non-sub AB1's which I also used). DeKay
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erik_squires is correct. The original LS3/5a had a Q of 1.2 which produced a bump in the mid bass. This was done to balance the bass to the rest of the sound spectrum since a flat speaker sounds lean if it's bass resonance is high like the LS3/5a. But the price of a high Q to balance the sound is increased overhang in the bass roll off and thus decreased definition in the bass. |
Here is simple/nutshell info on such from a speaker manufacturer. Having used various vintage single driver speakers, mated with various tube/SS amps, for the past 20 years (as well as different enclosures - including open baffle) I do pay attention to the combined QTS measurements (and/or guessed values based upon listening/experimentation) of the drivers I've owned/used/consider'd. Damping factor (low values) of the amps I've used/use is also a consideration.
DeKay |
@czarivey Fret a pun too. This type of Q is no quixotic quagmire cued(pun) up. |
@erik_squires Yes Thanks. Your quintessential knowledge appreciated. On less thing to fret over. |
PS - There are other Q’s in speaker design and measurements so don't get them confused but I'm pretty sure this is what is meant here. In designing the alignment of the lowest frequency driver a great deal of artistic license must be allowed given the tradeoffs of speaker size, maximum bass output and expected placement. A speaker designed for near-wall or desktop placement in general wants a lower Q. |
I wouldn’t worry too much about it. In general in this case, Q refers to the "bass alignment" and how the bass rolls off. A high q ( > 0.7) causes a bump at the bottom followed by a faster drop. A low Q ( < 0.7) causes the bass to roll off more slowly but without the hump. A lot of smaller speakers use bump at the bottom to make them sound better. A Q of 0.7 is often referred to as optimally flat. The bass alignment of a driver in a sealed enclosure is related to the size of the cabinet. Smaller cabinet = higher Q. Larger cabinet = lower Q. In a speaker like this though an optimally flat speaker may make it more easily to integrate with a sub at the -3 dB since it wont’ have a bump to minimize. Truthfully, these are pretty technical terms which are great for designing a speaker but won’t matter much in room as the proximity to walls and floors will change the bass behavior a great deal. In particular, don't try to get a perfect measuring speaker. You want one that sounds great in the location you are planning for it. While a Q of 0.7 may be maximally flat in an anechoic chamber it may also sound like it lacks bass in your room. |
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