stevie

[quote name='JTUK' timestamp='1359669257' post='1958677'] A decent 410 shouldn't be boomy, IME... but an amp with a semi paramtric EQ stage is good for notching problematic rooms... [/quote] This is your answer. Without knowing where the boom is coming from and what frequency is causing it you are working in the dark. A separate parametric equalizer is your best bet. It will also enable you to sort your midrange problem out.

I'd just like to air my appreciation for one of Basschat's real gentlemen. Tom replied to my request on the forum for help to pick up an equalizer I'd bought from someone in east London. Despite the snow, Tom travelled from Essex to Leytonstone to pick the unit up for me. Not only that, but he paid him the cash on my behalf that I'd previously transferred to his bank. To top it all, Tom was brilliant and packed the unit up for me (the seller had promised to pack it up but failed to do so). What can I say? My faith in humanity is restored:-). Seriously, Tom is a very generous guy and, if you're reading this thread to see whether you can do business with him, then the answer is a definite 'absolutely'.

Good advice from Phil as usual. You could use a spacer ring to fit your new driver. Cut it out of 1/2" MDF to suit the new speaker. For a reversible job, put adhesive foam on the back, screw it to the front of the cab and then bolt your driver to it. Your new speaker will be 1/2" closer to the grille but there's usually enough space to allow it. This is a common problem when going from a pressed steel to a cast chassis. I did this with an Ashdown cab and it worked fine.

What about singers who think their only obligation is to bring a mic and are happy to let the others in the band buy the PA? How common is that or have we just been unlucky?

Richard, I certainly hope you can persuade your customers to post their build experiences here. There are probably quite a few prospective punters watching and waiting.

Has anyone on here bought one of these kits yet?

A bit late (sorreee!) but Mike bought an amp from me a few months ago. It was a perfect transaction and Mike is a great bloke to do business with. Do not hesitate!

I've bought an equalizer from a very nice bloke in Leytonstone E11 and I've no way of getting it over to Dorset. I thought I'd be able to send a carrier in to collect it but he says he can't promise to be in all day and is not interested in dealing with freight companies. Is there anyone in London E11 who would be able to collect (it's not heavy) and then hand it over to a UPS driver for me? There would be a bottle of Scotch or a nice bottle of wine in it for you.

[quote name='Bill Fitzmaurice' timestamp='1355924143' post='1904527'] Your own anecdotal can be just as vaild as some 'leading lights'. Take Vance, for example. For many years and editions of his book he espoused the notion that stuffing a sealed cabinet with damping duplicated the effect of a larger cabinet. He was wrong. He fell into the trap of accepting someone else's data and opinion at face value without confirmation, in this case that of Tom Nousaine, and Tom's conclusion was erroneous due to his having used incomplete data to arrive at it. I didn't accept Tom's conclusions without confirming them, and I found them incorrect. So have a number of other sources, and in his latest edition of his book Vance has revised his advise on the subject. The lesson that should be learned is that no source is infallable, and if you think something they say may not be spot on don't hesitate to confirm or disprove it for yourself. One's own anecdotal experience can be the first step in that process. [/quote] Scientists [i]will[/i] change their minds when presented with new and convincing evidence. Theories persist until a better one is proposed, reviewed and accepted. Given that the Loudspeaker Cookbook has been in print in its various editions for 25 years, it is hardly surprising to find that one piece of information has changed. The fact that this expert has revised his opinion in the light of new evidence makes him more credible, not less, but I don’t think he has ever claimed to be infallible.

[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.