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cabinet frequency response
- Thread starter bearjew
- Start date
A 15" driver in a approximate 2 cf box and 98 db/w/m sensitivity is highly unlikely to have usable response at 32Hz. The 32Hz is at best a -10db number. It may still be a nice cab for some needs, but it will not have much deep bass (unless the cone is mass loaded, the driver has a large Xmax and the sensitivity is far below the stated 98db - the latter could be based on the peak at the high end if the drivers range...).
OP,
I bought this powered sub at gc and gigged with it for year playing Reggae. It will likely do a good job of making that low A sound good. It's damn expensive but anyway here it is:
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I sold it to fund another cabinet that does bass better - at least for me. But this particular powered sub will no doubt make lots of bass for you. I used it along with my regular stage rig just piled on top of it. I came full circle - sort of - and now use an external HPF set at 35hz. My lowest notes are just "B" but it would probably work just as well at "A."
- Nov 24, 2008
- 4,343
- 7,163
- Disclosures
- Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
Wow. Excellent explanation. Thanks man, I had the pieces of the puzzle but hadn't put them together like you just did. Thanks for teaching me. I bookmarked your post.
acmebass
Commercial User
So, it would seem, we again have a choice.
Do we design a loudspeaker to have predictable and circumscribed characteristics within its performance limits, or do we select driver parameters based on an assumption that the unit will be overdriven, and "come into its own" under these extreme circumstances?
I suggest that this is a matter of personal preference from player to player, and people who really love to pound their equipment, the otherwise over-damped woofer might be the correct choice.
I hadn't put it together either, Duke. But I never thought of it before.
Who's this AstroSonic guy? He seems to be able to say some stuff.
In being a professional player for almost 40 years and tinkerer I knew very well what was happening but didn't know how to describe the physics of what was occurring.Thanks much, Astrosonics. Makes perfect sense. Well duh!
To me the best solution (which has become easier) is the use of adjustable HPF's. If they can be made relatively sonically transparent---done deal. If you start with a low QTS driver---in my experience it's in it's non--optimal range until its cranked. I guess if you know that your going to be living in the cranked range then it would be a good choice. But if--like me---there is a wide dynamic range in the gigs you play then it wouldn't sound its best most of the time.
To me the best solution (which has become easier) is the use of adjustable HPF's. If they can be made relatively sonically transparent---done deal. If you start with a low QTS driver---in my experience it's in it's non--optimal range until its cranked. I guess if you know that your going to be living in the cranked range then it would be a good choice. But if--like me---there is a wide dynamic range in the gigs you play then it wouldn't sound its best most of the time.
- Nov 24, 2008
- 4,343
- 7,163
- Disclosures
- Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
I think we have here a very solid argument for using woofers with sufficiently long x-max (along with appropriate tuning) for the system to behave as intended even at high SPL.
Bruce Wayne?
alexclaber
Commercial User
If a manufacturer sells their cabs through GC, then designing for abuse conditions would seem appropriate, eh? Otherwise, many of the cabs would never survive GC's showroom floor. (I don't know, I've never been in GC... 
)
)
Great information, and I like to see designers considering xmax, max SPL and all the driver parameters. I know it was a well discussed issue in the Greenboy threads
But in practicality, no bass cabinet manufacturer is going to test this or measure it. Nor max power. It really doesn't work just to add up all the watts the common drivers are spec'd for and say that's max power. Same for other limits, Xmax, and max SPL is going to be left as a surprise to the end user to discover at the gig. At least I think no one will bother to measure it, maybe just calculate it.
But in practicality, no bass cabinet manufacturer is going to test this or measure it. Nor max power. It really doesn't work just to add up all the watts the common drivers are spec'd for and say that's max power. Same for other limits, Xmax, and max SPL is going to be left as a surprise to the end user to discover at the gig. At least I think no one will bother to measure it, maybe just calculate it.
acmebass
Commercial User
Certainly an academic argument in my case, but interesting nonetheless. Everybody knows my cabs are dreadfully inefficient for just that reason.
Clark Kent?
Thanks,
Andy
acmebass
Commercial User
5", 8"?
Depends on the application. Application is something not often thouroughly discussed. Nor psychoacoustic effects. Nor off axis power response. Or size of its footprint. Nor room gains and losses. (loading of low frequencies being very relevant to this discussion).
The amount of acceptable non-linearities -- I can go on....
Personal taste (as mentioned).
The room and its properties (including audience) often having as much importance to the design goals as many other considerations. There is no "one size fits all".
Frequency response (at what amplitude?) and "maximum" output are often over emphasized.
Best thing for me? A different cab for every instrument and room. But its easier when you build your own of course.
And there is as mentioned, the extra expense required to maximize ones design goals. I have never found in a commercial product everything I need (Especially in one package!). Even in an instrument.
About the bag end mentioned. Closed box. Using the predictable rolloff below resonance to achieve very low frequencies with low frequency processing. I believe it was called the ELF (Extra Low Frequency) system. Application was for studio or small room.
acmebass
Commercial User
I think all of those things are being discussed, ad infinitum, many of them over and over again, except "off-axis power response," which doesn't exist. Power knows no axis, it's just power.
Yeah, that's the Bag End system I was referring to. I hope that helps the OP.
Thanks,
Andy
um--I'm using 5's, 6.5's and 8's to good ends. Low f3's and pretty good efficiency---the 5's are stock but the 6.5's and 8's are also by Eminence's wizard designer.
Ok---I assume that all of us guys making speakers check out each other's stuff. I gotta tell you---I was looking at Andy's and Roger's sites---man---they are really good values.
Ok---I assume that all of us guys making speakers check out each other's stuff. I gotta tell you---I was looking at Andy's and Roger's sites---man---they are really good values.
Bruce Kent here. (LOL)
I have been mainly visiting TB to learn and occasionally help out when I can. Considering how much I have learned here it feels good to have actually contributed something useful.
By way of background, I have been designing and building speakers since the late 60's. Built my first head and cab (for somebody else) in 1969. Manually measured my first TS parameters in 1975. I love playing bass although I've never played for thousands or had a top 40 hit. Recently moved to New Mexico. I have a shop currently under construction. I am not really a businessman. It takes lot more than technical expertise and woodworking skills to run a successful bass cab company. I prefer designing and building for the occasional soul who wonders in, and has a tone preference and general idea of how much spl is needed. Playing and cab building are a passion and an avocation, not a livelihood. Hats off to you guys who are doing it for a living.
BTW, I wish that I had thought of this overdrive/BL thing on my own, but I didn't. It was figured out years ago. I came across this in different articles/papers over the years. It is briefly discussed in JBL Technical Note Volume 1, Number 9, Distortion and Power Compression in Low Frequency Transducers". They actually state that this (loss of BL during overdrive) was intentionally "designed into the transducer (E140-8) to add warmth and 'punch' to bass guitar sound reproduction". Without knowing this, a person would have to be highly skeptical of the claims often made about great bass from these drivers because they are way over damped (Qts ~0.17). Most folks just assume that this is the result of designing for maximum efficiency.
With respect to choosing between a normally damped/large Xmax design or an over damped/overdrive design, I think that both approaches are legitimate. I suspect that most designers inherently prefer a more linear design (normally damped, large Xmax).
My more recent designs have used an EBS alignment: departure from 0db starts around 150Hz-200Hz, gently slopping to a knee in response (top of the knee around -5db), then the usual drop-off. The tuning frequency is chosen so that the trough of minimum cone motion (loading) extends downward to include the lowest frequency of interest. Fb is above this, but not far. I think this is similar to the alignment Mike talked about (looks sealed).
+1 for the HPF. IMO, an HPF should be included in any professional grade bass amplifier. It should be adjustable, with at least 4 and 5 string settings (fully adjustable preferred). This conserves both power and excursion (even on sealed systems). If an HPF is 'baked in' it should be disclosed in the specs.
Bob Pody
I have been mainly visiting TB to learn and occasionally help out when I can. Considering how much I have learned here it feels good to have actually contributed something useful.
By way of background, I have been designing and building speakers since the late 60's. Built my first head and cab (for somebody else) in 1969. Manually measured my first TS parameters in 1975. I love playing bass although I've never played for thousands or had a top 40 hit. Recently moved to New Mexico. I have a shop currently under construction. I am not really a businessman. It takes lot more than technical expertise and woodworking skills to run a successful bass cab company. I prefer designing and building for the occasional soul who wonders in, and has a tone preference and general idea of how much spl is needed. Playing and cab building are a passion and an avocation, not a livelihood. Hats off to you guys who are doing it for a living.
BTW, I wish that I had thought of this overdrive/BL thing on my own, but I didn't. It was figured out years ago. I came across this in different articles/papers over the years. It is briefly discussed in JBL Technical Note Volume 1, Number 9, Distortion and Power Compression in Low Frequency Transducers". They actually state that this (loss of BL during overdrive) was intentionally "designed into the transducer (E140-8) to add warmth and 'punch' to bass guitar sound reproduction". Without knowing this, a person would have to be highly skeptical of the claims often made about great bass from these drivers because they are way over damped (Qts ~0.17). Most folks just assume that this is the result of designing for maximum efficiency.
With respect to choosing between a normally damped/large Xmax design or an over damped/overdrive design, I think that both approaches are legitimate. I suspect that most designers inherently prefer a more linear design (normally damped, large Xmax).
My more recent designs have used an EBS alignment: departure from 0db starts around 150Hz-200Hz, gently slopping to a knee in response (top of the knee around -5db), then the usual drop-off. The tuning frequency is chosen so that the trough of minimum cone motion (loading) extends downward to include the lowest frequency of interest. Fb is above this, but not far. I think this is similar to the alignment Mike talked about (looks sealed).
+1 for the HPF. IMO, an HPF should be included in any professional grade bass amplifier. It should be adjustable, with at least 4 and 5 string settings (fully adjustable preferred). This conserves both power and excursion (even on sealed systems). If an HPF is 'baked in' it should be disclosed in the specs.
Bob Pody
Hey Bob
Well--welcome!
It's so interesting. I may be of little brains but I know I've got a good ear. Now I know why I hated the E140's when they came out! I assume that the K's were a higher QTS--they were my favorite. Without knowing anything---when I was young and throwing together cabs I found that .30 to .35 were the magic spots for what I liked.
Man--you want to hear a funny story? I was involved in the design of a little digital amp for a known amp manufacturer that was geared for guys that double. Now with upright--an HPF is really a necessity. Piezos put out an insane amount of subsonic information. So I said they needed to put in an adjustable HPF. They did. Let's just say that I didn't imagine that they needed to be told that 6db/octave was just this side of useless.They wouldn't change it to 24. Oh well.
Well--welcome!
It's so interesting. I may be of little brains but I know I've got a good ear. Now I know why I hated the E140's when they came out! I assume that the K's were a higher QTS--they were my favorite. Without knowing anything---when I was young and throwing together cabs I found that .30 to .35 were the magic spots for what I liked.
Man--you want to hear a funny story? I was involved in the design of a little digital amp for a known amp manufacturer that was geared for guys that double. Now with upright--an HPF is really a necessity. Piezos put out an insane amount of subsonic information. So I said they needed to put in an adjustable HPF. They did. Let's just say that I didn't imagine that they needed to be told that 6db/octave was just this side of useless.They wouldn't change it to 24. Oh well.
