stevie

[quote name='alexclaber' timestamp='1355317189' post='1896794'] The attached plots are the same driver, the first measured in the summer, the second measured in the winter - ignore the LF stuff because it wasn't set up for that, it's a midrange/treble response measurement. The lower temperature changes the cone and the suspension stiffness - and look what that does to the frequency response curve! [/quote] Alex, thanks first of all for staying with this and for the measurements. I know we have diametrically opposed views on this issue (at the moment) but that doesn’t mean we cannot discuss the facts. When you’re trying to figure out a puzzle like this one, it helps if you keep the variables to a minimum. Unfortunately, these curves add another variable – temperature. I appreciate you’re trying to show that stiffening the surround effects the frequency response of the speaker. But dropping the temperature by 10 degrees (was the ambient temperature 8 degrees?) not only affects the suspension, it affects everything. The voice coil resistance and inductance will drop as the temperature drops, the VC gap will change, the stiffness of the cone will change. Driver fs can rise by as much as 75 - 80 percent - compared with the 10 to 20 percent difference we see after break-in. So, in some ways this is a bit of a strawman, in that you are proving something that nobody is contesting: everybody knows that varying the temperature of a loudspeaker changes its performance. Then there is the matter of whether the differences shown are actually audible. It would be more useful to concentrate on the LF end because the data is easier to obtain and because this is where people are claiming to hear noticeable differences. Also, anyone on this forum with a copy of winSD who wishes to do so can plug the figures in and verify them, as I see Phil and Lawrence have already done.

I've heard some negatives about the Samson but the other amps listed are well respected - even the Behringer. You might keep a look out for a used QSC USA 850 or 900, which are 425 watts per channel and are the amps that built QSC's reputation. They sound good, have quiet fans, and just keep on going. They are 3U but fit in a shallow rackmount case. eBay prices are generally under £100.

I have a problem with the bass. The notes appear uneven to me, with lower ones being quite loud and higher ones sometimes nearly disappearing. For example, the first two notes at the very beginning are loud but the third one is very quiet.

Here you go, Phil. This is the relevant section from Vance Dickason's Loudspeaker Design Cookbook. "8.20 Break-in Prior to testing, all cone speakers should be broken in. However, the reason for doing this is not as obvious as you might imagine. While the majority of woofers will undergo a "loosening" of the suspension system after five to ten hours of play, this has very little effect on the Thiele/Small parameters used for developing box volumes. Fig. 8 shows a free-air impedance measurement comparison of a 6.5” Peerless woofer right out of the box to the same woofer after 12 hours of break-in using a sine wave generator (at 25 Hz) and amplifier. Importing this data (along with the delta compliance curves also made before and after break-in) into the LinearX Leap Software yielded the parameter summary given in Table 8.1. TABLE 8.1 BEFORE AFTER F0 49.9Hz 44.5Hz Qms 2.11 1.97 Qes 0.44 0.39 Qts 0.37 0.33 VAS 16.8 l 21.6 l At first glance it appears that there has been a substantial shift in parameters with at least an 11% decrease in the driver’s resonance frequency. However, when these parameters are used to create box simulations the answer is obvious. Figure 8.2 shows the comparison of the before and after parameter sets used to create both a sealed and a vented box computer simulation. Differences in those box simulations are shown in Table 8.2. As can be seen, the changes in box performance are trivial. The reason this occurs is that the FS/Qts ratios remain constant before and after break-in. In the case of this woofer, FS/Qts before break-in was 136.79 and after break-in 136.72, nearly the same. This is true for all woofers. Many times different samples of the same model will “appear” to have entirely different T/S parameter sets, when in reality they will provide identical box performance. If you suspect that two samples are very different because the parameter set is not identical or close in the various parameter values, check the FS/Qts ratios or perform a computer box simulation in the same box volume with the different data sets. This will immediately tell you if the woofers really are the same or if something important has changed. So why bother to break in drivers prior to testing? To assure that a valid test sample is being used. If a bad voice coil rub or poorly glued surround or spider are going to be a problem, banging the driver around with a reasonable amount of voltage at 25Hz for 12 hours should reveal the flaw. There is no sense in proceeding to design a project if the woofer is not a representative sample."

[quote name='Phil Starr' timestamp='1355273444' post='1896364'] Hi Stevie thanks for the data. you can see compliance and hence Vas and fs changing as you'd expect but there is also a difference between mms and Qes between the two drivers. Were these measurements of two speakers one 'broken in' and one not? I've got an unused and a used deltalite here which I ordered at the same time and I thought out of curiosity that if I had time I would compare the two when I get round to building their ultimate cabs. If the variation (in mms for example) is down to manufacturing spread then I might need a bigger sample. How did you measure the parameters in your sample? [/quote] You’re welcome. I took the measurements with Liberty Audiosuite using the same driver (brand new in a sealed box), running it in for 4 hours in free air to get the second set of data. It would probably have been more accurate if I'd measured several times. I take your point about the change in mms, although it's clearly not affected the result. Another independent set of measurements would be very useful. Even if there are variations between your drivers, I’d be very surprised if you didn’t get the same results as I did. [quote name='Phil Starr' timestamp='1355273444' post='1896364'] I share your frustration when anyone says 'believe me because I'm an expert', there's either evidence or there isn't. [/quote] Indeed. [quote name='Phil Starr' timestamp='1355273444' post='1896364'] I still disagree with you, I think speakers do change over time (bit surprising if they didn't) and that I have heard those changes with at least some speakers, your data isn't incompatible with that interpretation but it certainly doesn't confirm my belief either. [/quote] I don’t disagree that speakers change over time. I was just commenting that the changes are slow because of the stability of the materials available nowadays. There was quite an interesting interview in Soundstage Magazine with Paul Barton the designer and owner of PSB in which he talks about break-in and aging (amongst many other things). Interestingly, when he re-measured one of his speakers ten-years after it was built, the deviation from the original measurements was no more than 1/4dB. This is what he says: “Finally, and perhaps most controversially, Barton talks about the supposed break-in effect of components that has become so popular in audio today. Break-in refers to running components for a long time (sometimes hundreds of hours) to the point where their components "settle" into their proper operating mode. Barton doesn’t doubt that some components do change subtly, but he thinks that the major improvements people think they’re hearing aren’t in the components at all. Barton doesn’t doubt that people are hearing these changes, but thinks that what they’re hearing is actually brain break-in. Barton has examined his own speakers to test this. He has taken a Stratus Gold loudspeaker, built and measured some ten years ago, and re-measured it today. The deviation is slight, perhaps 1/4dB at most. Although that deviation can possibly be heard, it is certainly not a huge difference that one may attest to hearing. Instead, Barton surmises that the difference in sound that people are hearing over time is conditioning of the brain. He cites experiments done with sight that indicate the brain can accommodate for enormous changes fairly quickly and certainly within the hundreds of hours that audiophiles claim changes occur in. Could this apply to hearing, too? Barton thinks that more often than not, what happens is that the changes in perceived sound that are attributed to component break-in are simply the brain becoming accustomed to the sound. He warns listeners not to fool themselves.” [quote name='Phil Starr' timestamp='1355273444' post='1896364'] I look forward to seeing the stuff you have from Dickason and when I get time I'll have a play around with your figures. Looks like Santa needs to bring me a new Cookbook. [/quote] Nearly done it. It’s not as easy as cut n' paste.

It's only 7 pages, gjones - we've only just started. There's a thread on Peavey T-40 basses that's up to 14 pages already. Bass players don't do things by halves, you know. Edit: Oops, I just got bumped up to page 8.....

[quote name='Happy Jack' timestamp='1355320694' post='1896881'] This is an alarmingly sensible post, which completely fails to achieve arrogance or confrontation, and utterly misses the opportunity to score cheap points. I must ask my namesake to modify his post to better fit in with the overall 'tone' of this topic. [/quote] It's an honest post. Jack hasn't achieved the level of cynicism and distrust of authority and 'experts' that some of us have.

Me too. We know how delicate and sensitive they all are really.

[quote name='R Baer' timestamp='1355252509' post='1896007'] This seems to go against the information put out there by one of the largest speaker manufacturers in the world, most cabinet manufacturers and my own personal experience, but I guess everyone is entitled to their opinions. [url="http://www.eminence.com/2011/06/speaker-break-in/"]http://www.eminence....eaker-break-in/[/url] [/quote] That's the second time you've posted that link from the Eminence customer services tech. On this particular matter he says, "Subtle changes will continue throughout the life cycle of the speaker". Which is fair enough and doesn't contradict what I said. There are plenty of speakers from the 1970s still working fine today. There have been some unstable materials like undoped paper, foam and PVC surrounds, but by and large, I think you can expect a modern speaker to perform to specification for several decades. I'm sure that's the case with Baer speakers, isn't it? Interesting that he strongly recommends [i]against [/i]using a test tone to break your speakers in. So who is one to believe if the so-called experts disagree?

What you seemed to be saying was that being a mere bassist makes your opinion less valid than those working in the "industry". That's what Bill Fitzmaurice seemed to be saying.

[quote name='Bill Fitzmaurice' timestamp='1355240743' post='1895819'] If you ignore the replies from all those not actually in the loudspeaker business it's a lot shorter. [/quote] Yes, it's nice to see you guys with your big logos promoting your businesses on here.

[quote name='Jack' timestamp='1355250158' post='1895968'] What do bassists necessarily know about speaker mechanics? [/quote] You'd be surprised how many speaker designers play bass. Have you heard of Laurie Fincham?

I agree with iiipopes on this one. The bass driver in a 4-ohm cabinet has to be 4 ohms unless there are more than one. Your mid and HF drivers could easily be 8 or even 16 ohms but it's the woofer that counts.

[quote name='Phil Starr' timestamp='1355184012' post='1895267'] I don't think there can be any doubt that the compliance of the spider and the surround will change over the life of a loudspeaker and that this will change the Thiele/Small parameters. Without any data (sorry) to back this up I would guess that this would follow a decay curve with rapid changes at first slowing down as the speaker ages but never reaching a point of no further change. I've seen the fs/Qts/Vas argument though the only reference to this in my 4th edition of Dickason this is about manufacturing spread, not breaking in. [/quote] Hi Phil, Modern drivers are designed with materials that tend to be fairly stable. I don't think the parameters change very much over time, at least not on a good quality driver. I checked out a 25-year old JBL 12" not so long ago and it met the manufacturer's T.S. specs. The Dickason I was referring to was the 7th edition. I'll post the whole section when I get time to type it out. [quote name='Phil Starr' timestamp='1355184012' post='1895267'] I'd love to see any data anyone has though. [/quote] I'll post Dickason's before/after break-in measurements later because they're in the relevant section in his book. Here are the measurements I took of an Eminence Kappalite 3012LF (fresh from its sealed box) last year. You can put them in your own modelling software if you wish or refer to the curve on the right. As you can see, the curves are indistinguishable.

[quote name='Bill Fitzmaurice' timestamp='1354628075' post='1888317'] Loudspeaker designers don't debate break-in amongst themselves, for the same reason. But pundits will jabber on forever. [/quote] Actually, they do. You’ll find qualified designers all over the internet trying to explain that speaker break-in is a myth perpetuated by sales and marketing departments. The science involved is so basic that it's in the Loudspeaker Cookbook, written incidentally by a qualified and respected designer, Vance Dickensen, also editor of the industry’s trade journal Voice Coil. Vance Dickensen writes that [i]after break-in “enclosure requirements and performance are nearly identical[/i] since the Fs/Qts ratio stays virtually the same” and that, although there are measurable changes in driver parameters after break-in, [i]any changes in response will be inaudible[/i]. He backs this up with data, of course. He also says, [i]“Do you need to ascribe a particular time period for "break-in"? No.[/i] Just plug it in and play it like you normally would.” Very sensible advice and a direct answer to this thread’s original question. Floyd Toole thinks that speaker break-in is a myth too. Described by the Audio Critic as “arguably the world's leading authority on loudspeakers”, he was Head of Acoustical Engineering at Harman International Industries (JBL, Studer/Soundcraft, Crown, dbx, BSS, Lexicon, AKG, Revel) for 15 years and set up the Harman speaker testing labs, which are world renowned. He is an acknowledge expert on loudspeaker testing and psychoacoustics. I copied this short passage on the subject from his book: Sound Reproduction - Loudspeakers and Rooms. “In parts of the audio industry, there is a belief that all components from wires to electronics to loudspeakers need to “break in.” Out of the box, it is assumed that they will not be performing at their best. Proponents vehemently deny that this process has anything to do with adaptation, writing extensively about changes in performance that they claim are easily audible in several aspects of device performance. Yet, [i]the author is not aware of any controlled test in which any consequential audible differences were found, even in loudspeakers, where there would seem to be some opportunities for material changes[/i]. A few years ago, to satisfy a determined marketing person, the research group performed a test using samples of a loudspeaker that was claimed to benefit from “breaking in.” [i]Measurements before and after the recommended break-in showed no differences in frequency response[/i], except a very tiny change around 30–40 Hz in the one area where break-in effects could be expected: woofer compliance. [i]Careful listening tests revealed no audible differences. [/i]None of this was surprising to the engineering staff. It is not clear whether the marketing person was satisfied by the finding.” By the way, this book gets a glowing recommendation from Siegfrid Linkwitz on his site, where he says, "It debunks much of the BS that seems to have permeated the audio industry and many of its customers.” Now, guys, if we are going to contradict some of the most respected and erudite experts in the business, I suggest you respond to my previous requests for some [i]evidence [/i]to support the non-scientific, anecdotal assertions we have heard so far. Would that be too much too ask?

Assuming the measurement you took was correct, those drivers are not 8 ohms. I've never seen an 8-ohm driver with a DCR that low. Let me tell you about a trick some speaker companies have been known to pull. They fit 6-ohm drivers to their cabinets and label them 8-ohms. Why? Because it makes the speaker louder than the competition in the showroom. It only becomes problematical when you connect two speakers to one amplifier channel. However, at loud volumes where you would expect the amp to complain, the speaker impedance rises, neatly solving the problem. The worst example I've seen of this was the Zeck 15/3 PA speaker, unknown over here but a best-seller on the continent a couple of decades ago. They had the nerve to fit a 4-ohm EV driver to their 8-ohm box. The magazines raved about how much louder it was than anything else but none of them ever bothered to measure it.

[quote name='alexclaber' timestamp='1354269305' post='1884213'] In a typical bass cab this will result in an increase in output between 50Hz and 100Hz - you can measure this and you can model this. And you can hear it! <snip>.... you'll hear a fresh woofer as having noticeably less bottom than a loosened up one. [/quote] This is impressively specific. If there's "noticeably less bottom" I'd expect at least a 3dB rise between 50 and 100Hz, wouldn't you agree? I'd be very interested in seeing the data you've used to arrive at this.

It sounds like people are finally realizing the benefits of fitting high quality drivers. It's about time.

[quote name='andyjingram' timestamp='1354361613' post='1885154'] Stevie, I listened to the youtube clip, and as poor as the sound quality is, are you saying that you genuinely hear no difference whatsoever between the two speakers? Yes, the playing is inconsistent, and the changes are extremely subtle, but they are there in the way I have experienced with many guitar speakers in the past. I just want to emphasise the word [i]subtle[/i] here. We are talking about fractional, but audible differences. You make a good point about people believing that they hear (or saying that they hear) what they are told to expect by advertising or snake-oil hearsay. That is true, and part of human nature to a degree- how many non-musos have asked you why you don't play a Fender through a Marshall, because they 'know' they are 'the best'? There are no doubt people who agree on speaker break-in without ever having heard the difference or without the ability to hear it, but that doesn't make it untrue. [/quote] Good post. I didn’t think the sound quality was that poor actually and yes, I thought I might have heard a difference, although not consistently from one sample to the next. But I’ve learned to be very sceptical about what I think I hear because I know how easily it is to be fooled, especially when differences are minor. I would say straight away that I haven’t carried out any testing on guitar loudspeakers and wouldn’t argue against any claims that they “break in” or change over time. I simply don’t know. I can think of a couple of reasons why they might: 1) they are often used in open-back cabinets where a change of driver resonant frequency will impact differently on system response than in an enclosed cabinet, and 2) they are based on "old” materials (such as paper surrounds, non-impregnated cones, etc.) that are more liable to change – and keep changing - than modern materials. Although that video is interesting, there are a couple of reasons why the comparison is flawed and why anyone should be cautious about drawing any firm conclusions from it. Firstly, the level and quality of the test signal is inconsistent. As the guitarist is using a particularly horrible distortion sound, my personal preferences were directly related to the amount of distortion I heard. That is, I preferred the (quieter) clips when there was less distortion. Or to put it another way, I probably equated differences in the original signal to differences in the speakers. Secondly, there were no real controls. In particular, there were no measurements to determine whether, for example, the first speaker was identical to the second. If they were different to start with (quite possible), all bets would be off. Thirdly, we know in advance which speakers are being played in each clip. This invalidates the comparison because of expectation bias, the process where you listen out for cues that confirm what you expect to hear and ignore cues that don’t. In controlled listening tests, even the most skilled and practiced listeners will hear things that are not there if they expect to do so. For any opinion on this comparison to be valid, a listener would have to identify each speaker correctly in 10 out of 12 of clips without knowing which was which. Do you think you could do that? The reason I posted the YouTube clip initially was because of the comments: all of the people who left comments thought the broken-in speaker was better, mainly because they thought it was “smoother”. This should ring warning bells immediately because, as we know, one man’s “smooth" is another man’s “lack of high-end sparkle”. I suspect that if this video had been posted with the captions reversed, the response would still have been 100% in favour of whatever speaker people thought was broken-in. You never hear of a run-in speaker sounding worse, do you? That soft bass never becomes softer; it always becomes tighter. And that lean bass never becomes thinner; it always becomes fuller. Interestingly, I didn’t hear any difference in the bass response between these clips. To demonstrate why what you expect to hear can override what you actually hear, check out this YouTube clip on the McGurk Effect. [media]http://www.youtube.com/watch?v=G-lN8vWm3m0[/media]. Definitely worth a minute of your time. So, although none of this proves that speaker break-in does not exist, it does provide an explanation of why people might believe they’ve heard a change in their speaker when it hasn't changed at all. Especially if they’ve been told categorically by an expert that the sound will change and they then become a stakeholder in the whole process by downloading a burn-in file or CD and/or spending weeks playing pink noise through their system. And of course, they want to believe: they don’t want to admit they have made a mistake and they certainly don’t want the hassle of taking their speakers back to their dealer. (This is a bit Derren Brown, but I’m sure you get the picture). It's very easy to measure whether there’s a difference in the frequency response of a speaker in a cabinet before and after running in. I’ve done it. These measurements are reproducible and repeatable. I also posted a link earlier to someone who did the same thing in a more thorough manner than my efforts. Why do people believe in burn-in when there's no evidence for it? Well, it's a long story but it boils down to the fact that the longer you break your hi-fi components in, the less likely you are to return them. It’s a sales technique. And a very effective one too. Ask the people who sell two thousand dollar cables.

[quote name='Mr. Foxen' timestamp='1354311065' post='1884817'] So by saying 'not audible', you are meaning not audible to you personally because you can't hear the system, rather than actually being audible to people hearing them? Or the rule only applies to stuff you've heard? Or "not audible in the context of a speaker system" only applies to speakers where it doesn't, and systems where it does they are 'a different animal'? [/quote]

I don't know what's audible and what's not audible in your speakers, Mr. Foxen. I've never heard them.

Guitar loudspeakers are a different animal. And just to clarify, I'm not saying that drivers don't 'break in'; I'm suggesting that break-in is not audible in the context of a speaker system.