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Freq response charts vs real world experience
- Thread starter Alex Xander
- Start date
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
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- Owner, Bill Fitzmaurice Loudspeaker Design
Depending on the crossover frequency it can be quite critical. A very famous incident in the 1930s involved a movie of Jane Powell tap dancing. The speakers were reproducing the taps as quite audible double-hits, one from the woofer, one from the HF driver, until an engineer figured out and cured it via phase/time aligning the drivers. OTOH, at many frequencies phase and time alignment are irrelevent.
Exactly! It can be done because everyone has the great outdoors. Find a nice field somewhere with power of course.
We could produce a standard recording, to be played on a standard amp(backline 600) with some standard settings at standard conditions.
The recording could be four freqs 30hz, 600hz, 1200hz, and 7000hz. You measure the SPL with at those frequencies and post your results. Hopefully three or more people would eventually post their results for a cab and an average 4 point chart could be posted on the internet.
Just an idea.
MikeBass
Supporting Member
- Nov 4, 2003
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- Endorsing artist- Suhr basses, PedalTrain, GHS, Ultimate Ears
I glance at specs, but never live and die by them.
I've went into arguments with a few guys here in this thread over this in the past.
But the funny thing is, no matter what I play through, I usually end up sounding like me and sure, I can split hairs about what ever, but I still get "me".
I used a pair of Hartke 2.5XL cabs for a while, look up the specs on them. On paper they for the most part, look freakin' great- 35 Hz To 12 kHz.
I never even looked at the specs until after I opened this thread, because IMO they sounded stinkin' great- I didn't need to look at the specs. And didn't care.
But I would love to see aome "real world" testing of bass cabs done by someone.
Not that it would change much for me.
On paper it could suck, but plugged in and on the gig it could rock!
I've went into arguments with a few guys here in this thread over this in the past.
But the funny thing is, no matter what I play through, I usually end up sounding like me and sure, I can split hairs about what ever, but I still get "me".
I used a pair of Hartke 2.5XL cabs for a while, look up the specs on them. On paper they for the most part, look freakin' great- 35 Hz To 12 kHz.
I never even looked at the specs until after I opened this thread, because IMO they sounded stinkin' great- I didn't need to look at the specs. And didn't care.
But I would love to see aome "real world" testing of bass cabs done by someone.
Not that it would change much for me.
On paper it could suck, but plugged in and on the gig it could rock!
Why limit it to four freq's when a sweep can be done more easily and for zero extra expense and effort?
Any standard pro poweramp that's not clipping during the test would be fine as it would add/subtract nothing from the test.
Just a small warning - testing in the great outdoors can potentially get a very negative reaction from neighbours. Which is understandable given what sine waves, white noise, and sound sweeps sound like. If possible, test somewhere where neighbours aren't going to be inconvenienced.
And I agree that 4 frequencies won't tell you enough. Sweeps will give more information.
Aint that the truth. Should have seen the fun and calamity when I did the initial testing of my LABhorns.
I'm trying to get something sorted for a Sydney test. May know someone out the back of Blacktown with some acreage The automated test sweeps in lots of programs can be set to be short duration, and the IMP tests are basically a loud click.
I was curious how you are doing your impedance sweep. TrueRTA does not have this ability. I'm hunting around for an automated method of doing it, preferably with TrueRTA, rather than yet another piece of software/hardware to cart around.
Sweeps sound great, but you have to have a way to record the response in real time. That's why I suggested a discrete test method, so a hand held meter could be used.
We have an earthquake truck(the ultimate sub woofer!) that sends out little trembler's in sweeps, then we plot the generated signal verses the reflection in real time. We use a special USB interface and program to send and receive the signal, I guess it could be done with a standard sound card though.
As an alternative, if you can do an impedance sweep, then you can measure the Thiele-Small parameters of the driver. Then you plug the design into WinISD and extract the SPL curve. It's only good for low frequencies, but if you scale your measured curve to the theoretical curve, then you arrive at a decent sensitivity plot.
Been reading this thread off and on, there was another like it a while back but I'll say this:
1. It's a capital idea
2. It will never happen because these companies will pretty much be admitting that they've been filling you full of shiite for the last 20 plus years.
3. I'm not a computer geek nor am I familiar with all this software but I can be in short order if needed.
4. If anyone could organize a scientific test with a true baseline or something to eliminate the variables to compare commercially available cabs let me know what I can do to help out.
5. I don't know if I could be of much help because of the 4 cabs I currently own, all are DIY and all sound good for what they are to my ear.
6. If Bill F.'s offer of "bring me your cabs and I'll measure them" still stands, give me a minute to calculate shipping 4 cabs (varying from 2.5 - 5.2 cu.ft. and weighing from 45-80lbs.) from Texas to the east coast and back 1 at a time. If it means bring me them in person I'll need to schedule a week off and load up the truck.
As for the people who say, "the hell with specs, trust your ear" there is a valid point to that as music is a subjective and artistic thing but whatever "your sound" is, there most certainly is a response graph, SPL chart and off axis response graph that goes along with it. There is a whole lot of America that can't just go down to the bass emporium and plug into anything and everything that's available to the bass playing world. Learn a little bit about this stuff, find out what kind of response pattern sounds good to your ear, and if companies were to be forced to publish honest specs, you certainly could choose a cabinet based on specs and get something you like sight unseen but of course this will never happen, refer to item #2 above.
1. It's a capital idea
2. It will never happen because these companies will pretty much be admitting that they've been filling you full of shiite for the last 20 plus years.
3. I'm not a computer geek nor am I familiar with all this software but I can be in short order if needed.
4. If anyone could organize a scientific test with a true baseline or something to eliminate the variables to compare commercially available cabs let me know what I can do to help out.
5. I don't know if I could be of much help because of the 4 cabs I currently own, all are DIY and all sound good for what they are to my ear.
6. If Bill F.'s offer of "bring me your cabs and I'll measure them" still stands, give me a minute to calculate shipping 4 cabs (varying from 2.5 - 5.2 cu.ft. and weighing from 45-80lbs.) from Texas to the east coast and back 1 at a time. If it means bring me them in person I'll need to schedule a week off and load up the truck.
As for the people who say, "the hell with specs, trust your ear" there is a valid point to that as music is a subjective and artistic thing but whatever "your sound" is, there most certainly is a response graph, SPL chart and off axis response graph that goes along with it. There is a whole lot of America that can't just go down to the bass emporium and plug into anything and everything that's available to the bass playing world. Learn a little bit about this stuff, find out what kind of response pattern sounds good to your ear, and if companies were to be forced to publish honest specs, you certainly could choose a cabinet based on specs and get something you like sight unseen but of course this will never happen, refer to item #2 above.
1: Agreed.
2: I think the original idea was to bring your own, rather than have them supplied by the manufacturer/distributor. But who knows, some may be interested.
3: Bill is fine with software, as am I. There are others who could host too that could do it, esp for TrueRTA.
4: A calibrated mic and the same test conditions should me performance meausured here, in the US or anywhere very comparable. Certainly, it'll be MUCH more of a useful reference than a list of manufacturer generated specs.
5: I'd be happy to measure DIY gear too, if you were happy to divulge the specs and drivers used. It could encourage others to do the same, especially if they see the potential for great performance with reduced costs. This is probably even more relevant outside the US where gear is proportionately more expensive.
6: Can't speak for Bill, but I'd love to do a 6/12 monthly measure what you brung day. Still organising the deals at my end for Sydney, but maybe aften the Xmas school holidays.
2: I think the original idea was to bring your own, rather than have them supplied by the manufacturer/distributor. But who knows, some may be interested.
3: Bill is fine with software, as am I. There are others who could host too that could do it, esp for TrueRTA.
4: A calibrated mic and the same test conditions should me performance meausured here, in the US or anywhere very comparable. Certainly, it'll be MUCH more of a useful reference than a list of manufacturer generated specs.
5: I'd be happy to measure DIY gear too, if you were happy to divulge the specs and drivers used. It could encourage others to do the same, especially if they see the potential for great performance with reduced costs. This is probably even more relevant outside the US where gear is proportionately more expensive.
6: Can't speak for Bill, but I'd love to do a 6/12 monthly measure what you brung day. Still organising the deals at my end for Sydney, but maybe aften the Xmas school holidays.
Distortion. That's a huge factor that's usually overlooked in loudspeaker testing and measurement. Knowing the distortion characteristics of a particular speaker could tell you a lot about that speaker's sonic character, assuming you knew how to interpret the numbers, which is another issue. I'd venture that most musicians don't have enough of a technical background to interpret the numbers anyway. That's not a knock, it's just an observation, BTW..
We are going to do this for the horn guys in Novato, CA on November 4, weather permitting.
I'm trailering down from Sacramento with another horn builder, and we are meeting up with a guy down there. He is securing his company's parking lot for a Sunday speaker fest.
Details in the Everything Else section on Bill's board.
Great on the distortion measurements!
One question. Is 1M enough distance for multi driver cabinets? It seems that it should be farther to allow the drivers to integrate. How much farther I don't know. Standard audience spacing? 3m? Maybe 1m and 3m, for the bassist compared to the closest audience member or other group members.
Also I'm wondering about a half-power rating test. That is put 200w through a 400w cabinet and measure SPL and distortion? This seems like it could reveal quite a bit about bass compression.
