Frequency response

[agedhorse]

Point taken, and it’s a nice speech for anyone who uses their gear in anechoic chambers. And yes, I understand boundary interference – measurements taken in different rooms, or even outdoors, will look different. In fact, I did take some outdoor measurements (although not in a hay field, as I don’t have one readily available), and while they did look much different, upper and lower extension were virtually the same.

Which was the point of my post.

However, the indoor measurements shown are a good representation of what I actually hear from these cabinets. In the real world. Where I use them. As well as the differences I hear between them.

Regards,
Wayne A. Pflughaupt

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Then assuming your graphs are “accurate”, how can you say that the response falls like a rock below 80Hz when your own graphs do not support that accusation.

I posted the frequency response specs based on how the industry reports them from your numbers and they do not support your accusation, not even close. This is what I object to, it’s an unrighteousness accusation.

 

[micguy]

If you want to know what a speaker is really doing, use a laser interferometer.

At port resonance, the majority of the sound from a bass cabinet comes from its port - the cone on the woofer is almost standing still. Where I worked, we had a couple different generations of laser vibrometers - yes, you can figure out the motion of a cone, but neither could tell me anything about the air motion in a port. A laser vibrometer, despite being a very cool tool, is blind to what's going on at one of the most important frequency ranges of a ported enclosure.

 

[Scarysharkface]

What is the practical application of a listed frequency response for a speaker or bass cab? I have seen listed response’s as high as 80 for a bass cab when the frequency of a E string is half of that and a B string is even lower, how is this number to be used? Thanks.

I built a big dual-18" isobaric cabinet some years back. It rolled-off around 26 Hz. The biggest difference between that cabinet and the 4-12 I sometimes used was that the isobaric cabinet made the pool table in a bar we played migrate across the room. Our sound guy had a very difficult time controlling the rumble, even at low volume. So, less fundamental is usually what's called for.

Here's a video clip where it shows up when the lights hit it:



Taurus pedals just filled the room through that monster.

John

 

[beans-on-toast]

Frequency response data is difficult to compare from one manufacture to another. There are standards but interpretations vary and everything os in the details. You should be able to compare one product to the next from a particular manufacturer but even that isn’t always true. Testing might have been done under different conditions depending on what their current procedures were. A older product might have been handled differently.

I’ve worked in an anechoic chamber. It’s eye opening how they change testing. Eminence has an interesting and simple approach for QC testing frequency response on the assembly line. They have a panel in the wall with a hole in it. The speaker is held in place, a quick test is performed, a computer determines if it meets specs or not. Depending on the results, they might take more samples to monitor production. Of course, a buyer can specify that 100% of their products be tested but this costs more.

When it comes to speaker cabinets, some companies test each unit in a chamber and provide a printout certifying the results. You can find this with some mics as well. I’d be surprised if many musical instrument manufacturers test cabs to this extent other than in quality control tests. Not everyone is set up to do these tests.

 

[Arjank]

I've developed a pretty good hunch that the theoretical small-signal low frequency model of a sealed or ported speaker, assuming good input data such as accurate specs, is likely to be more accurate and useful than a home measurement.

+1

For all my designs I use two different pieces of modeling software for the below 250hz region, above that I do measurements with MLS software. Measuring anything below 250hz will take a big anechoic chamber or (as an alternative) measure outside and do a half-space (2pi) measurement.

 

[Old Garage-Bander]

I completely agree, especially the part about an anechoic environment and the schooling to know what you are doing (and when the numbers you measure aren't right).

I made my living for over 4 decades in part designing and building acoustical stuff - mostly microphones, but also loudspeakers. If you think you can do accurate acoustical testing at home, you are mistaken. The kind of gear you need to do that includes a purpose built anechoic room, a whole lot of B&K equipment, and a LOT of schooling to understand what you are doing.

Anyone who wants others to take seriously any of these kinds of measurements should not just post the results.
They should also list what equipment was used, any applicable calibration references and the environment in which the test was conducted.

 

[mike buzzetti]

RTA doesn't provide anything about excursion, only energy/frequency. You can download software like Room EQ Wizard and see this as well as the time component in a 'waterfall' plot, though.

I ment add a spectrum analyzer to the interferometer output data !!

 

[dbsfgyd1]

In the absence of other qualifying information, frequency response numbers are pretty much meaningless. Some manufacturers might use the -3dB point; others might cite the -10dB point. Still others seem to just pull numbers out of their... uh ... out of thin air. And almost without exception, those frequency response numbers are at 1 watt, not at the rated power. Even with some qualifications given, I wouldn't assign much value to those numbers except to compare models within one manufacturer's product line. Otherwise, it's mostly all just "Fun With Numbers" and marketing puffery.

As far as NEEDING flat response down to 40 or even 30Hz -- that's a whole different can of worms. Whether or not that's critical to the sound of a bass amplification system has been the subject of quite some discussion in these parts. All I want to say about it is to go search out some of those threads on your own.

Great post. Me? I don’t really care about the numbers as much as can I get the right sound out of it. Nothing like the ear test.

Also, in my band, a larger ensemble with FOH support, lot’s of Uber low end is not needed, and if there were, would cause problems with the overall house mix. I’m not so sure why one would need that much low end either, but to each their own.

 

[micguy]

I built a big dual-18" isobaric cabinet some years back. It rolled-off around 26 Hz. The biggest difference between that cabinet and the 4-12 I sometimes used was that the isobaric cabinet made the pool table in a bar we played migrate across the room. Our sound guy had a very difficult time controlling the rumble, even at low volume. So, less fundamental is usually what's called for.

There are a lot of reasons a DIY Isobaric subwoofer might not sound good - I wouldn't take that one data point as convincing evidence that we should avoid extended low frequency bandwidth. Tons of tours and big venues seem to think that extended low frequencies are worthwhile. Are they all wrong?

 

[The Massive]

This thread is interesting. As an average "joe" I leave the math to the engineers. I just rely on my ears to select the cab I want that sounds and feels inspiring. Then just use sound reinforcement to reproduce super low frequencies.

Most of the time just gimme some EV's in a Diesel cab and I'm happy. I don't care if they don't handle the lows like modern stuff. The last modern 15 I had was the Ampeg Pro Neo 15 and I don't care how many low frequencies it produced...it had no character compared to the EV's.

I guess it's like Harley's, everyone is concerned about getting the 114 when an old Evo 80 does just fine and sometimes is more fun to ride!

 

[micguy]

I guess it's like Harley's,

Isn't EVERY Harley overkill, when looked at in any kind of logical manner? A drummer I used to play with described his Harley as "Yeah, it rides rough most of the time, but at 120 mph, it smooths out".

 

[agedhorse]

Isn't EVERY Harley overkill, when looked at in any kind of logical manner? A drummer I used to play with described his Harley as "Yeah, it rides rough most of the time, but at 120 mph, it smooths out".

As long as the oil remains inside the motor!

 

[The Massive]

Isn't EVERY Harley overkill, when looked at in any kind of logical manner? A drummer I used to play with described his Harley as "Yeah, it rides rough most of the time, but at 120 mph, it smooths out".

My old Fat Boy is great! It's got the counter balancers in it and doesn't shake like the old ones. 120 on an old Harley...that's pretty fast. The new one will do that...but them old ones with 4 and 5 speed transmissions start to scream past 95.

That said, it's nice having loud pipes and a heavy bike on the road. Like riding on glass! Can you tell I'm missing summer?

 

[micguy]

26945491[/URL], member: 68399"]As long as the oil remains inside the motor!

Well, yeah, if you wanna get picky… ;-)

 

[Scarysharkface]

There are a lot of reasons a DIY Isobaric subwoofer might not sound good - I wouldn't take that one data point as convincing evidence that we should avoid extended low frequency bandwidth. Tons of tours and big venues seem to think that extended low frequencies are worthwhile. Are they all wrong?

Oh, the cabinet sounded GREAT! It was just too much. Let the PA handle the extreme lows.

John

 

[Lostgallifreyan]

Good thread. I doubt it has run out of road yet, either. Let the burning of rubber re-commence...

One thing I am wondering about. Given just how clearly the harmonics are vital for carrying the character of the sound, it's odd that in another thread recently, so many bass players seemed entirely satisfied with the notion that a sound tech can ask for all the electronics after the bass to be shut off when the sound clipped without apparent reason, letting the sound tech solve the entire sound.

That thread pretty much resolved on a consensus that in an emergency, needs must...

What it did NOT resolve was the contradiction between obsessive pursuit of tone, combined with a great consensus that this overriding by whatever the sound tech has available is valid. Either their harmonics ARE important, or they are not. Can't really have that both ways. It implies an extraordinary lack of understanding of how tone is built, or is an extended part of the instrument, not just some abstraction to be thrown away and ignored by a sound tech if it becomes momentarily inconvenient.

To put it bluntly, it's as if there is a huge disconnect between threads like these, and threads that deal in matters of gear management. If more connection were made, gear management would improve. Sound techs wouldn't have to make desperate decisions like telling a bass player to 'kick off his amp and preamp'... Instead, they could adapt a great sound to a room and make everyone happy.

 

[Old Fart]

Many of us use High Pass Filters to eliminate those ultra low frequencies anyway. They rob power, endanger speakers and make for a too-boomy sound.

 

[byacey]

I sort of alluded to this in my previous post.
Just because you have an enclosure that will reproduce all that low frequency energy doesn't necessarily mean that you need all that low energy in the context of the music. If the low end is rumbling over everything else, it renders the efforts of the other musicians as a waste. This is what the art of a good mix is all about, putting the different instruments into their perspective sonic space in both frequency spectrum and amplitude. Maybe the bass does sound better with the fundamental naturally 10 db or so down from the lower harmonics.

Unfortunately this is lost on many of the newer generation of wannabe sound engineers, as they become easily addicted to pounding low frequencies, regardless if it makes musical sense, or not.

 

[The Massive]

I sort of alluded to this in my previous post.
Just because you have an enclosure that will reproduce all that low frequency energy doesn't necessarily mean that you need all that low energy in the context of the music. If the low end is rumbling over everything else, it renders the efforts of the other musicians as a waste. This is what the art of a good mix is all about, putting the different instruments into their perspective sonic space in both frequency spectrum and amplitude. Maybe the bass does sound better with the fundamental naturally 10 db or so down from the lower harmonics.

Unfortunately this is lost on many of the newer generation of wannabe sound engineers, as they become easily addicted to pounding low frequencies, regardless if it makes musical sense, or not.

Love this. It's all about the mix and if you're pushing crazy amounts of low end you're competing with the kick drum. IME, to not lose anything in the mix and not muddy stuff up, the bass should be sitting just above the kick drum in the mix. Push those punchy mids!

 

[mike buzzetti]

Love this. It's all about the mix and if you're pushing crazy amounts of low end you're competing with the kick drum. IME, to not lose anything in the mix and not muddy stuff up, the bass should be sitting just above the kick drum in the mix. Push those punchy mids!

In an actual recorded mix they kik and bass do NOT compete !! no mud bud