Vd

[alexclaber]

[quote name='bigfatbass' post='679724' date='Dec 9 2009, 11:24 PM']When I was young(er) all the the hifi and music equipment mags (International Musician) used to conduct lab tests. They used to publish test results and measured cab performance in an Anechonic Chamber (basically a padded cell) and produce frequency response and max SPL charts etc. The reason this kind of reviewing fell from favour was because I often read in these magazines that stuff measured great but sounded bad. So reviewers started trusting their ears rather than their oscilloscopes.[/quote]

If something measures great but sounds bad then whoever is testing it is testing it wrong or misinterpreting the data. An easy mistake is to believe a simple SPL plot because these are often taken with a pink noise burst and so a seemingly perfect flat plot might only be flat because distorted overtones are filling gaps. Like a cab might have a dip at 250Hz but the woofer generates particularly high 2nd order harmonic distortion at 125Hz which thus synthesizes a load of extra 250Hz energy and fills in the gap. But it won't sound anything like a cab which has low distortion at 125Hz and even response at 250Hz, even though the SPL plots will be identical.

[quote name='bigfatbass' post='679724' date='Dec 9 2009, 11:24 PM']Alex is right and specs are important, but they are only part of the story... ...The same is true of cab design. Computer models should be checked with testing in an Anechonic Chamber.[/quote]

Absolutely. Design, model, build, measure (I do this outdoors in half-space as anechoic chambers big enough for bass are rare and expensive), re-design and model, re-measure, etc etc. It's a pain in the neck but the sad fact is that unless you have the budget of a Formula 1 team you are never going to come up with sufficiently accurate models to get the finest details right. Fortunately you can model and measure and compare, and then you can mentally figure in the inaccuracies of your modelling which gets you closer to the desired result with each iteration.

[quote name='bigfatbass' post='679724' date='Dec 9 2009, 11:24 PM']Basschat is providing the beta testers for Barefaced, but I am not entirely convinced the testers have the expertise and experience of using lots of different gear necessary to perform the role.[/quote]

I've certainly had useful feedback from other basschatters but I also have myself and plenty of other customers who were not on basschat when they went Barefaced (though many are now). But the design decisions all come down to me and I may not be the greatest bass player in the world (though I'm better at playing my way than anyone else ) but I do have an almost autistic ability to dissect and analyse sound and then apply those learnings to loudspeaker design.

Alex

[BigRedX]

I think the problem that some people were having with publishing spec sheets was that if some manufacturers are going massage the figures to make their cabs look better on paper then it makes the whole process a mockery. How do you know which figures are relatively unbiased and which are pure fantasy?

I mean if. as you said, there are manufacturers adjusting something easily verified like the weight of a cab (and who here other than Alex has actually weighed their cabs to see how close they are to the published figures) what hope is there for anything that requires some actual knowledge of acoustics and specialised equipment to verify?

I'm not against the publication of specs, but unless all cabs are tested and measured in the same way, comparison of one cab to another on paper is not particularly meaningful.

[wateroftyne]

[quote name='bigfatbass' post='679724' date='Dec 9 2009, 11:24 PM']Basschat is providing the beta testers for Barefaced, but I am not entirely convinced the testers have the expertise and experience of using lots of different gear necessary to perform the role.[/quote]
Some do...

[bigjohn]

[quote name='BigRedX' post='680070' date='Dec 10 2009, 11:39 AM']I think the problem that some people were having with publishing spec sheets was that if some manufacturers are going massage the figures to make their cabs look better on paper then it makes the whole process a mockery. How do you know which figures are relatively unbiased and which are pure fantasy?

I mean if. as you said, there are manufacturers adjusting something easily verified like the weight of a cab (and who here other than Alex has actually weighed their cabs to see how close they are to the published figures) what hope is there for anything that requires some actual knowledge of acoustics and specialised equipment to verify?

I'm not against the publication of specs, but unless all cabs are tested and measured in the same way, comparison of one cab to another on paper is not particularly meaningful.[/quote]


Absolutely - it would be good if this was done independently. Some kind of kitemark type system.

[alexclaber]

[quote name='bigjohn' post='680153' date='Dec 10 2009, 12:42 PM']Absolutely - it would be good if this was done independently. Some kind of kitemark type system.[/quote]

Never going to happen sadly, it's too small a market sector.

But as I've said over and over again thermal power handling specs are supplied by the manufacturers and 99% of them are honest and accurate. Not terribly useful but they are truthful. And Vd specs are just as straightforward and can be supplied to the cab manufacturers by Eminence, Celestion, B&C, etc, unlike sensitivity and frequency response claims which are open to interpretation. It is just a single number which is derived from cone area multiplied by cone excursion - there's very little wiggle room to bs or 'massage'.

Alex

[Rich]

[quote name='alexclaber' post='679923' date='Dec 10 2009, 09:21 AM']Hi Rich,

I'm going to turn this into a useful example. Let's say that when you were looking at your Nemesis you were also looking at another cab. Here's the specs for the Nemesis (assuming this is the right model 15, they've been through a few different models):

Power Handling 250 Watts RMS
Freq. Response 38hz - 18khz
Impedance 8Ω
Sensitivity 100dB SPL@1W1M
Weight 42lbs[/quote]Mine's the older one with a slightly different spec, but that's not really relevant
[quote]And lets say you were looking at another cab with the following specs:

Power Handling 350 Watts RMS
Freq. Response 35hz - 18khz
Impedance 8Ω
Sensitivity 101dB SPL@1W1M
Weights 48lbs

So you might think so yourself, well the latter cab is a bit more powerful, a bit more sensitive and goes a bit lower, so it's worth the extra weight. But let's assume that Vd was also quoted.

For the Nemesis = 350cc
For the Brand X cab = 250cc

This means that despite the Nemesis looking like it'll be less loud and fat according to the original (and very open to marketing abuse) specs, it will actually produce greater low frequency SPL.

Alternatively you could have an excursion limited power handling figure added to the specs (which would be likely to show the Nemesis as having more) or a true low frequency sensitivity figure (ditto). The product of these two figures would show the Nemesis as having better performance.

Alex[/quote]
Aha.
So to use a motoring metaphor, judging a cab purely on things like sensitivity and frequency is a bit like judging a car purely on horsepower and 0-60 time... the first car has more horse and a quicker 0-60, but when you look closely at the second car it has more torque and a better 30-70 time, which in reality is far more useful. Have I got that right?

[alexclaber]

[quote name='Rich' post='680210' date='Dec 10 2009, 01:20 PM']So to use a motoring metaphor, judging a cab purely on things like sensitivity and frequency is a bit like judging a car purely on horsepower and 0-60 time... the first car has more horse and a quicker 0-60, but when you look closely at the second car it has more torque and a better 30-70 time, which in reality is far more useful. Have I got that right?[/quote]

Yes, that kind of thing!

Midrange sensitivity and thermal power handling are critical to get the mids loud enough, so very important with PA tops, but with bass guitar we tend to run into problems when it comes to producing lows, and because our cabs generally have to produce the mids from the same speakers as the lows, when the speaker starts struggling with the lows it also screws up the midrange. Yes, most of the tone is in the mids but if you can't produce enough lows to support those mids then it won't sound like a bass.

You know how everyone goes on about how you can't get good bass out of a guitar speaker? Well actually you can at low levels from a closed back cab like a Marshall. But as you turn up the lack of Vd does you in and it all gets grindy and distorted and eventually speaker death happens.

Alex

[Wil]

Really Alex, you're taking the piss now. You've lost my custom, I'll tell you that much - how can I give you any credibility when you're happy to modify and delete people's posts on a whim when they dont follow the track you want the thread to take?

I'm sure you'll delete this also, so pointless ranting on.

Disgusted of Bristol.

[alexclaber]

Hi Wil/Disgusted Of Bristol,

I've left in everything that's relevant and removed that which wasn't. If you want to start a thread on those subjects elsewhere then feel free. I simply don't want a potentially useful and educational thread to be filled up with off-topic arguments which distract from the matter in hand. If you look back you'll see that I've left in plenty of useful points from those same people whose other posts have been edited/deleted.

Alex

[sk8]

[quote name='Wil' post='680266' date='Dec 10 2009, 02:13 PM']Really Alex, you're taking the piss now. You've lost my custom, I'll tell you that much - how can I give you any credibility when you're happy to modify and delete people's posts on a whim when they dont follow the track you want the thread to take?

I'm sure you'll delete this also, so pointless ranting on.

Disgusted of Bristol.[/quote]
i was wondering why i could only see EBS_freaks posts as quotes in other messages and not in the thread

[alexclaber]

[quote name='sk8' post='680415' date='Dec 10 2009, 05:01 PM']i was wondering why i could only see EBS_freaks posts as quotes in other messages and not in the thread[/quote]

I just wanted to make him feel welcome, he loves a bit of moderation (which of course should only be in moderation).

Alex

[Musicman20]

Bloomin heck.

I think im more confused than before....purely because half the information is gone.

[alexclaber]

Should we just delete the whole thing and start again then? Or should I just write this on my website, you can all read it, and then you can agree or disagree without having an online argument about it?

I mean honestly, I am just trying to help simplify the process of choosing a suitable cab. If it doesn't have enough Vd then you can cross it off your shortlist. Then go and try the ones that do. And I guarantee that the ones without enough Vd might have impressed you in the shop but would have turned out to be a horrible disappointment on the gig.

Yes, you have to try a cab to find out if you like the sound, but are there really enough hours in the day to try every cab on the market before making a decision? Vd is a good spec to narrow the field. In fact it's rather like doing the "I want a 4x10" thing except it removes the risk of getting a sub-par 4x10" with insufficient Xmax (and thus Vd) and also broadens the field to other cabs with similar output whose tone you may or may not prefer.

Alex

[electriccheese]

For me this information it's very useful. If I try a Markbass CL104 (4x10 sealed cab) in a shop, I can't really know how much loud can be in a gig. With this information, it's posible compare with another that you knows well. For exemple, if tried in a gig a Markbass 104HF, and I know how much air can move, I can compare it with the CL104 for know how loud can be in a gig.

This thoughts are real, I wanted a CL104 but I'm afraid that isn't capable of go enough loud fo me. The tone I like very much, but I doubt it will take 600W of reggae bass sound...

Edited December 10, 2009 by electriccheese

[Stylon Pilson]

[quote name='alexclaber' post='680452' date='Dec 10 2009, 05:48 PM']Or should I just write this on my website, you can all read it, and then you can agree or disagree without having an online argument about it?[/quote]

Therein lies the rub. If you publish it as a thread on a discussion forum, then that suggests that you're inviting debate. If you didn't want to hear dissenting opinions then yes, you should publish it somewhere that doesn't allow people to post comments without vetting.

S.P.

[Wil]

Pretty much sums it up. I'd like to make it clear myself and Alex have conversed via pm so we know where we both stand - I myself find threads like this very interesting, but generally they get to be most interesting when the debate starts.

Edited December 11, 2009 by Wil

[JTUK]

Where has my post gone..??

I can find NO record of it anywhere...what the f*** has happened...?

If a mod has deleted it, I would expect a note and an explaination and a VERY good reason
And how come someone can delete MY posts...unless a MOD..??

NOT IMPRESSED AT ALL

[Protium]

[quote name='JTUK' post='681214' date='Dec 11 2009, 12:23 PM']Where has my post gone..??

I can find NO record of it anywhere...what the f*** has happened...?

If a mod has deleted it, I would expect a note and an explaination and a VERY good reason
And how come someone can delete MY posts...unless a MOD..??

NOT IMPRESSED AT ALL [/quote]

One of mine got deleted too. I think I'll live though.

[Machines]

alexclaber has the ability of a moderator in this subforum only.

[Protium]

[quote name='electriccheese' post='680604' date='Dec 10 2009, 08:04 PM']This thoughts are real, I wanted a CL104 but I'm afraid that isn't capable of go enough loud fo me. The tone I like very much, but I doubt it will take 600W of reggae bass sound...[/quote]

Leaves me wondering just how much bass you need in reggae, I very much doubt you will be pushing anywhere near 600W of "bass" Also wondering how many people bullshit how much volume they "need"? My old band played painfully loud using just my homebuilt 2x10 rig (eminence beta), bits and pieces connected together for the singers PA and a H&K Warp7 with 4x12 cab...

[wateroftyne]

[quote name='JTUK' post='681214' date='Dec 11 2009, 12:23 PM']Where has my post gone..??

I can find NO record of it anywhere...what the f*** has happened...?

If a mod has deleted it, I would expect a note and an explaination and a VERY good reason
And how come someone can delete MY posts...unless a MOD..??

NOT IMPRESSED AT ALL [/quote]
Wow... A+ for overraction. Nice one.

[electriccheese]

[quote name='Protium' post='681624' date='Dec 11 2009, 08:22 PM']Leaves me wondering just how much bass you need in reggae, I very much doubt you will be pushing anywhere near 600W of "bass" Also wondering how many people bullshit how much volume they "need"? My old band played painfully loud using just my homebuilt 2x10 rig (eminence beta), bits and pieces connected together for the singers PA and a H&K Warp7 with 4x12 cab...[/quote]

It's a little difficult to me to express what I want to say, I'm spanish... Maybe I said "bass" instead of lows.

What I'm trying to say is that a cab like a Schroeder 1212 (I have one) claims that can take 800W RMS, and with a flat EQ and a passive bass maybe can take 500W without fart. I have a Barefaced Compact, wich says that can take 450W, and I push it with 450W and EQ with some lows without any farting.

I don't know if now it's more clear...


And about loudness, I play a lot of reggae outdoor gigs with PA only for vocals. For a low bass sound is necessary a lot more power than for a midrangey sound without real lows (and maybe this is better for cut in a dense mix).

I really don't understand "bullshit" but it seems that is not a good thing...

Edited December 11, 2009 by electriccheese

[Protium]

[quote name='electriccheese' post='681694' date='Dec 11 2009, 08:46 PM']It's a little difficult to me to express what I want to say, I'm spanish... Maybe I said "bass" instead of lows.

What I'm trying to say is that a cab like a Schroeder 1212 (I have one) claims that can take 800W RMS, and with a flat EQ and a passive bass maybe can take 500W without fart. I have a Barefaced Compact, wich says that can take 450W, and I push it with 450W and EQ with some lows without any farting.

I don't know if now it's more clear...


And about loudness, I play a lot of reggae outdoor gigs with PA only for vocals. For a low bass sound is necessary a lot more power than for a midrangey sound without real lows (and maybe this is better for cut in a dense mix).

I really don't understand "bullshit" but it seems that is not a good thing...[/quote]

I mean that very few cabs are going to take 800W of bass/lows. Plus you need a pretty beefy amp to push that kind of power.

Sorry mate, the "bullshit" part wasn't aimed at you or anyone in particular

[electriccheese]

[quote name='Protium' post='681734' date='Dec 11 2009, 10:25 PM']I mean that very few cabs are going to take 800W of bass/lows. Plus you need a pretty beefy amp to push that kind of power.

Sorry mate, the "bullshit" part wasn't aimed at you or anyone in particular [/quote]

Don't worry, I don't understand english perfect, so...

I think the Barefaced Vintage will take this power, or nearly.

[alexclaber]

[quote name='bigfatbass' post='681527' date='Dec 11 2009, 05:24 PM']But to get back on topic, in the very first post of this thread Alex said that the figure Celestion quote for Xmax is wrong. So if there is not a consistant measure for Xmax it reduces Vd to a meaningless number. Doesn't it?[/quote]

Fortunately not! Every speaker manufacturer knows the gap height (Hg) and the voice coil length (Hc) of their drivers. With those two pieces of data you can recalculate Xmax in the modern mathematical way, which simply involves adding Hg/4 to the old Xmax number (Hc-Hg)/2. THe resulting mathematical Xmax works out sufficiently close to the Klippel analysis (Xmax where THD=10%) method.

[quote name='bigfatbass' post='681527' date='Dec 11 2009, 05:24 PM']Given that most cabs use the same drivers, they may be custom OEM versions but my bet is that in most cases the customisation involves sticking the cab makers label on the drivers, then any cab with Eminence, or made to our own specification by Eminance, will have the same Vd? Am I missing something?[/quote]

Nope, you're absolutely right. Same for Celestion, B&C etc. If a manufacturer has asked for a longer voice coil (as with the Avatar DeltaLite 10s) then they can tell you that number and you can recalculate Xmax (a different Hg would involve a whole new motor).

I'm sorry some people have been offended by the moderation, I'll be sure to make any further potentially contentious statements (I'm still astounded that such an argument ensued) on my website in future.

Alex