Vd

[wotnwhy]

[quote name='EBS_freak' post='679129' date='Dec 9 2009, 02:57 PM']Don't be retarded. You can the thread is not talking about weight.[/quote]

ebs_freak, you crack me up sometimes!

i'm not gonna bother pointing out several contradictions you've already made in this thread. i'm just gonna enjoy waiting to see how many more you make

as for my 2c, i think having specs are important and usefull in shortlisting when shopping for new equipment. adding Vd to specsheets will only help in that respect. if people are idiotic enough to buy a cab based on writing not sound then let them revel in their madness, don't get a bug up your butt on their behalf (as funny as it is )

[Stylon Pilson]

[quote name='EBS_freak' post='679136' date='Dec 9 2009, 03:02 PM']And we all know that the published fuel consumption is a load of BS.[/quote]

Is it? I know that they tend to involve certain simplifications, but that's just to ensure that the test is repeatable and hence fair. If you take two cars which have had their fuel consumptions tested under identical circumstances, and one returns 40mpg and the other returns 30mpg, then it's safe to assume that under most conditions, the 40mpg car will produce better fuel consumption than the 30mpg car in a like-for-like test.

S.P.

[EBS_freak]

[quote name='wotnwhy' post='679137' date='Dec 9 2009, 03:04 PM']ebs_freak, you crack me up sometimes!

i'm not gonna bother pointing out several contradictions you've already made in this thread. i'm just gonna enjoy waiting to see how many more you make

as for my 2c, i think having specs are important and usefull in shortlisting when shopping for new equipment. adding Vd to specsheets will only help in that respect. if people are idiotic enough to buy a cab based on writing not sound then let them revel in their madness, don't get a bug up your butt on their behalf (as funny as it is )[/quote]

The weight is a given... as pointed out in my earlier post. (as is dimensions... as I thought it would be obvious a no-buy item if you can't lift it or get it in your car...)

The reason the bias of the thread is not on weight is because to the average person, you can't fob off the weight of an item... but with tech spec, they are all open to interpretation and the measurement of such specs is not done under controlled conditions across the board for every manufacturer. Adding Vd means nothing either... especially if we don't know if a manufacturer has calculated their porting correctly, let alone their cab size in relation to the drivers.

Edited December 9, 2009 by EBS_freak

[wotnwhy]

ok, i guess i can sympathise with that. however i think in general people know now that numbers given by companies (of any kind, for anything) are to be taken with a pinch of salt (some pinches bigger than others, of course).

but there's still no denying that Vd would be a handy number to show, and in a lot of cases, is more relevant than some of the numbers currently given.

the argument that your making is that all these numbers are useless, and while that has the potential to be a very interesting discussion, it's still above and beyond the topic of this thread.

[alexclaber]

[quote name='bigjohn' post='679069' date='Dec 9 2009, 01:59 PM']Is that good or bad? Would that change dramatically with the celestion loaded 1212L?[/quote]

It's good, especially for such a small cab, hence its popularity. With the Celestions it's 478cc.

[quote name='51m0n' post='679023' date='Dec 9 2009, 01:11 PM']Or am I very much mistaken Alex?[/quote]

No, you're absolutely spot on.

[quote name='razze06' post='679015' date='Dec 9 2009, 01:03 PM']Will the appearance of more specs on the datasheet alter the quality of the sound that comes out of the speaker?[/quote]

No, but if you're going to quote some specs, why not make them the useful ones? The main figure that everyone gets excited about (watts watts watts) is all but completely useless. And if you're going to quote specs, make them honest. Some manufacturers have even quoted weight specs which are more than 10% lower than reality and that's not exactly hard to check!

[quote name='EBS_freak' post='678919' date='Dec 9 2009, 11:32 AM']Specs on paper mean nothing. Performance in the real world means everything.[/quote]

Real specs do mean something. If they didn't everything would be 'designed' by trial and error. Performance in the real world can be more accurately predicted by accurate modelling than by trying a cab in a guitar shop. But the best thing to do is to use the cab with your bass, your amp, your playing and in your band at a typical venue.

Without sufficient Vd that perfect sound you get in the shop simply isn't going happen on your gig.

[quote name='EBS_freak' post='679126' date='Dec 9 2009, 02:55 PM']I'm with Bose on this one. Dont publish meaningless specs that can be interpretted in different ways. Let your ears do the deciding.[/quote]

If you think Bose gear sounds good for the money then that explains everything! Mr Bose is a marketing genius.

[quote name='EBS_freak' post='679150' date='Dec 9 2009, 03:17 PM']Adding Vd means nothing either... especially if we don't know if a manufacturer has calculated their porting correctly, let alone their cab size in relation to the drivers.[/quote]

No. As most cabs have plenty of thermal power handling and plenty of midrange sensitivity, then Vd is the limiting factor. If ports are undersized then that will cripple the Vd but it's easy to see if that's the case. If the cab is very small (like a Schroeder or to a lesser degree like the Midgets) then it will take more power to drive the cab to full Vd but the total Vd remains the same. If the cab is tuned too high then it'll give the feel of greater Vd but will unload prematurely, whilst if it's tuned too low then it'll feel like it has less Vd. However within the typical tuning range of a bass cab the porting related variance is small compared to the absolute result of how much Vd it has.

Alex

[MythSte]

[quote name='alexclaber' post='679204' date='Dec 9 2009, 04:00 PM']but will unload prematurely,[/quote]

Teehee

[51m0n]

[quote name='EBS_freak' post='679194' date='Dec 9 2009, 03:53 PM']I'm not making that argument at all... unless there is an seperate body measuring everybody's cabs, the true figures are lost... and again, manufacturing speakers is an imprecise science... one manufacturer's idea of a good speaker design may not be shared by another... Until there is come control, I'll rely on my own senses.[/quote]

Sorry, but you'll be saying we cant trust the number of cones reported in a cab next.

As I said, proper verified and verifiable specs are useful, anything else is not.

No spec can tell you quite whether or not you will like the sound, but it can inform you as to whether or not the cab is capable of achieving your volume and dispersion requirements.

Put it another way, simple yes no question for you, do you believe modeling can accurately predict frequency response, volume and dispersion from a cab?

If you dont, then no one should be using software to make cabs, they need to go back to trial and error completely. Which is preposterous.

If you do, then specs drive those programs, and so can inform our decisions. Assuming they are accurate. And that we understand the specs and what they actually mean.

[alexclaber]

[quote name='EBS_freak' post='679211' date='Dec 9 2009, 04:09 PM']"Ports - it's easy to see if that's the case". I'm sorry, but most of the people on here wouldn't know what size port they are looking out for.[/quote]

A good rule of thumb is that the port needs to be at least 1/9 the size of the speaker.

[quote name='EBS_freak' post='679211' date='Dec 9 2009, 04:09 PM']Porting variance is small. Undersized ports will cripple Vd. Make your mind up.[/quote]

Sorry I should have been more clear - I was talking about port tuning so the statement would have been more clear if I said port [b]tuning[/b] related variance is small. Fortunately most decent cabs have sufficiently large ports though a few cabs have quite ridiculously small ports for the speakers they use.

[quote name='EBS_freak' post='679211' date='Dec 9 2009, 04:09 PM']And if you think that 2x12 can match a 8x10... I would like to see exactly how you have got to that conclusion. Have you gigged an 8x10? Or is this all paper based too?[/quote]

I have never gigged an 8x10" because I've never needed or wanted to, they just don't sound how I want. But yes, I know that the right 2x12" can quite happily match an 8x10" and more. Despite what you may thing it isn't rocket science. And amazingly rocket science does a pretty good job of making things fly to the moon without having to just guess at what will work. Engineers have been using science and mathematics for hundreds of years to build the world you live in. It seems rather curious to deem their work irrelevant in this specific case.

Alex

[wateroftyne]

[quote name='alexclaber' post='679240' date='Dec 9 2009, 04:42 PM']amazingly rocket science does a pretty good job of making things fly to the moon without having to just guess at what will work.[/quote]

[51m0n]

[quote name='alexclaber' post='679240' date='Dec 9 2009, 04:42 PM']amazingly rocket science does a pretty good job of making things fly to the moon without having to just guess at what will work[/quote]

Except in the dubious NASA issue when someone tried to do it all in Imperial measurements and then missed....

LOL!

Edited December 9, 2009 by 51m0n

[51m0n]

[quote name='EBS_freak' post='679263' date='Dec 9 2009, 05:04 PM']But that doesn't actually stop people having their own ideas about specifications does it?![/quote]

I spend my working life writing, reading, coding, and measuring results by specs. You dont have to tell me that people can have different understanding of what a spec is or means or is intended to suggest.

I am all for independant verification and tolerances and meaningful specs. I agree currently the specs produced by manufactureers are completely nonsense, and in fact tantamount to a breach in certain standards. I'd love it if there was a law that if a manufactureers so called spec could not be demonstrated as accurate within published tolerances then that manufacturer was in breach of contract. Then we could all start to trust specs (believe me the specs would be brought into line in a second if this was taken to its obvious conclusion a couple of times). I hate marketing departments too!

But all your comments fail to take on board that Alex is not suggesting that a load of marketing people dress up another mystery spec, but that companies use the real spec. In fact he's all for pushing companies to use real specs across the board, and I 100% agree with him, you seem to be of the opinion that this could not be ever achieved however, and so no specs should ever be printed, and we should in fact go and try all cabs in situ until we find the one we like. But even that cant be done since I doubt you can try any cab in all situations without buying it first (its not practical to be lent one for months). So we need an understanding of how well the cab should perform beyond a few goes with a band, and that requires specs.

A badly designed cab WILL sound awful, and underperform, and further more, although this one spec alone wont show you that it is poorly designed, if all the specs are correctly listed between it and a well designed cab then anyone who understands the specs will be able at a glance to point out the better designed cab. There are no ifs and buts and maybes about that, a badly designed cab will not spec as well as a properly designed cab. The trick is in being educated enough to recognise good spec combinations.

A badly built cab will not meet the specs it has assigned to it, and so will fail any tests against those specs. It will quickly garner a reputation for failures too.

As for modelling algorithms, rest assured that they are now close enough to tell you more than doing it by any more rough and ready process. I agree that nothing is the same as building it, but you can't build it 500 times, whereas you can model it 500 times. That would be why Formula 1 spend so much money on modelling. And believe me a speaker cab is a far far simpler thing to model than a Formula 1 car.

As for trial and error with rocket design, yes in the 50's, 60's and 70's there was a lot of trial and error, and there is now too, but now its done in a virtual world, modelled on computers, same with aircraft design!

[alexclaber]

The thermal power handling spec quoted is actually accurate - not useful but accurate. And it's simply the sum of the voice coil power handling figures as supplied by the speaker manufacturer. Those same speaker manufacturers can likewise provide accurate Xmax figures, either by Klippel analysis or by doing the voice coil length and gap height sum. And cone area is pretty damned obvious (but it's always less than you think because of the diameter lost to the cone surround and frame).

We play bass, we care about bottom, about moving air. You want a big bass sound, you need to be able to move air. The Vd is simply the amount of air the cones can move on one stroke, in cubic centimetres. It's nice simple maximum output spec. Isn't that much more useful than knowing how much heat you can pump into a cab without it blowing?

Alex

[alexclaber]

[quote name='EBS_freak' post='679298' date='Dec 9 2009, 05:50 PM']But the real spec isn't measurable if the cab design is not right - and no manufacturer is going to own up to that. So naturally, they will publish a Vd that makes them look favourable against their competitors. It's not all down to the choice of the speaker... as mentioned earlier, speakers and cab both influence the tone and volume of a cab. What the point of publishing the Vd if the speakers are in an wrongly sized, wrongly ported box... what about phase cancellation due to poorly positioned drivers... they all effect volume and tone.[/quote]

This entirely proves that you don't understand what I'm talking about. And if you think WinISD is all I use to design my cabs then you are WAY off the mark.

Vd is a no bs figure. Xmax times Sd. That's it.

If the box is tiny or the box is huge, the Vd is still the same.

Alex

[EBS_freak]

[quote name='alexclaber' post='679312' date='Dec 9 2009, 06:01 PM']Vd is a no bs figure. Xmax times Sd. That's it.

If the box is tiny or the box is huge, the Vd is still the same.

Alex[/quote]

Not really. Vd for a 12 inch speaker in a box measuring 13x13x1. Vd performance... great. Now tell me about the rest of the design. If you put the speaker in a shoebox or a coffin... what's the difference? Extreme example I know but you get the idea.

Edited December 10, 2009 by alexclaber

[alexclaber]

[quote name='EBS_freak' post='679327' date='Dec 9 2009, 06:09 PM']Not really. Vd for a 12 inch speaker in a box measuring 13x13x1. Vd performance... great. Now tell me about the rest of the design. Extreme example I know but you get the idea.[/quote]

Your extreme example merely proves how ill informed you are and why it's futile to argue with you. Within the spectrum of bass cabs, from 'undersized' Schroeders to the 'oversized' Big One, Vd remains entirely relevant and applicable. Sorry but it really is useful and judging by all the other responses I'm not the only person to think so.

Alex

Edited December 10, 2009 by alexclaber

[Wil]

I have to say I wholeheartedly agree with his sentiments about testing the merit of a cab with your ears. I do see the place of the science behind cab building but I also know I love the sound of the apparently poorly designed Ampeg 8x10 at full volume, much as I also like old British motorcycles despite them having a tendancy to fall apart if looked at too hard.

Edited December 10, 2009 by alexclaber

[Sibob]

For what it's worth, I don't care for specs....mostly because I don't understand them. I'm an advocate of letting my ears decide, I would never buy an amp or a cab based on written speculation. I've gigged a Barefaced 'Big One' a few times and was very impressed with it as a 1x15.....did it live up to its specs? Who cares, it sounds good!.

I play an Ashdown 4x8 mostly, sometimes combined with a 1x15. Do these cabs live up to others on a spec sheet?, perhaps not, but then I've been happy with them for 5 years, so make of that what you will

Si

Edited December 10, 2009 by alexclaber

[51m0n]

EBS_Freak please explain to me what you would have in the place of specs then, to help people make an informed decision about what they should go and test for themselves?

Or do you really think people should test everything?

Right now forums like this exist largely because we do actually have to test everything, or ask people of their real world experiences, in order to help us make an opinion.

The trouble is that one man's "it totally slayed up against my two guitarists' half stacks and my rottweiler drummer" is another man's "it barely covered the room playing jazz at the local cafe" - well maybe not that bad, but you know what I'm saying.

I, again, say I agree that marketing driven unvalidated and unverifiable specs (as we have now) are useless, and there should be an industry standard set of tests done independanty for a piece of kit (amp, cab whatever) such that the manufacturer is then able to publish specs, if only to protect the customer.

But were such an enforcement body in place, and were they rigorous, would you have any argument against the particular spec that Alex is mentioning here?

And if so please justify why it, in your opinion, is so worthless, given that it would be alongside accurate frequency, dB, wattage, blah blah blah specs too.

I am honestly trying to understand your point of view, and am failing to miserably right now...

Edited December 10, 2009 by 51m0n

[Sibob]

I think you're always going to have to have a certain few staple specs:
Power Handling (I know this is a point of contention with some people)
Ohmage
Weight
Speaker Sizes
Front/Rear/No porting
etc etc

But everything else (apart from this VD thing perhaps) is open to so much subjectivity and other variables.
I'm obviously no audiologist, but I would have thought perceived frequency responses and things like that change from room to room, venue to venue???. Not to mention the inherent differences in how each pair of ears actually HEARS something. Obviously correct me if I'm wrong.
And so from that point of view, I'd rather gig something a few times to establish if a cab is right!

Si

[Rich]

Call me a bit of a luddite, but the only specs I tend to look at these days are power handling (just to make sure the amp doesn't woefully over- or under-power them), impedance (amp compatibility), sensitivity (for a rough guide to 'loudness', and yes I admit this is possibly a red herring) and weight. Especially weight. I made the decision to have a go with the Nemesis 1x15s based mainly on back-friendliness!
Obviously there will be many folks who will eagerly want to know every single spec, almost right down to the designer's preferred socks. For this reason alone, maybe it's worth researching. But there will also be many of us for whom 'Vd' will really only ever be something we sniggered about in the playground when we were 12.

[alexclaber]

To be frank I really can't be bothered with petty arguments on this forum so despite my dislike of moderation I've decided to tidy things up. For anyone that just wants to leap in and have a dig then I'll be doing this in future, so save yourself some typing.

Just to clarify things further, Vd is an equivalent spec to a true sensitivity spec added to a true power handling spec - it tells you how loud a bass cab can play. If you're in the pro audio (SR) world then you are provided with accurate sensitivity specs and accurate power handling specs which give you the same end result. No large PA subwoofer rig would be put together for a gig without using these specs to ensure the dB requirements can be met.

And as it's much more complex to get sensitivity and power handling plots from every manufacturer, Vd is a simple shortcut to essentially the same end result. More Vd equals more dB SPL where it counts.

Strange that this should create such an argument as it's a bit like suggesting that van manufacturers should start quoting loadspace volume rather than just 0-60 times and top speed - it's the most useful spec for BASS players.

Alex

[alexclaber]

[quote name='Rich' post='679876' date='Dec 10 2009, 07:55 AM']Call me a bit of a luddite, but the only specs I tend to look at these days are power handling (just to make sure the amp doesn't woefully over- or under-power them), impedance (amp compatibility), sensitivity (for a rough guide to 'loudness', and yes I admit this is possibly a red herring) and weight. Especially weight. I made the decision to have a go with the Nemesis 1x15s based mainly on back-friendliness!
Obviously there will be many folks who will eagerly want to know every single spec, almost right down to the designer's preferred socks. For this reason alone, maybe it's worth researching. But there will also be many of us for whom 'Vd' will really only ever be something we sniggered about in the playground when we were 12.[/quote]

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

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

Edited December 10, 2009 by alexclaber

[electriccheese]

I'm grateful this information, 'cause I don't find useful the information that cab builders give for know the real volume of a cab. A Schroeder 1212 it's rated a 800W RMS. If I play reggae, can I EQ my bass very low and push the cab with a 800W head at max volume without break nothing? I'm shure that it's impossible that the cab resist this.

I think it's a very good way to know how much loud could go a cab, especially in the lows, not for know how it sounds.

[BottomEndian]

[quote name='Rich' post='679876' date='Dec 10 2009, 07:55 AM']But there will also be many of us for whom 'Vd' will really only ever be something we sniggered about in the playground when we were 12.[/quote]
I don't know what you mean.

[alexclaber]

[quote name='Wil' post='679384' date='Dec 9 2009, 06:57 PM']I have to say I wholeheartedly agree with his sentiments about testing the merit of a cab with your ears. I do see the place of the science behind cab building but I also know I love the sound of the apparently poorly designed Ampeg 8x10 at full volume, much as I also like old British motorcycles despite them having a tendancy to fall apart if looked at too hard.[/quote]

You absolutely HAVE to test a cab with your ears AND it has to be at the required SPL. That's why I have a one month trial period. The Ampeg 8x10" was a great design for the era, that's why it was such a success. And one of the big reasons why it was such a success was that it had more Vd than any other bass cab up to that point. If you like its unique sound (which many many bassists do) and you're happy with the size, weight and cost, then there really is no reason to consider using anything else. For some of the stuff I play it would be spot on tonally - but then for other stuff it wouldn't, and I hate being boxed into a tonal corner with my own gear (though I love using other gear at jams which does make me focus on one particular facet of my bass personality).

But let's say you're looking to replace your current big cab which is loud enough for your band but you know it won't go much louder without sounding nasty. Let's say the manufacturer has kindly told you that the Vd is 600cc. You then know that you can ignore every cab on the market whose Vd is much below 600cc, and you also know that you don't need to go much higher than 600cc to get the required output. There are a LOT of bass cabs out there, so doesn't it help to be able to narrow the field like this before you go and try all of them at rehearsals/gigs?

Alternatively you could look at the other specs of your cab (lets assume it's a nice 6x10"). Power handling 750W. Sensitivity 102dB. Now if you used the power handling spec to eliminate cabs that weren't powerful enough you'd end up with a list that still included a fair few 3x10" and 2x12" cabs which on the whole are unlikely to cope. Or using the sensitivity spec (which is the most abused one) you'd end up still including even some 1x12" and 2x10" cabs which wouldn't have a hope. And if you're quite new to bass playing you might even believe the specs, try a small cab with insufficient Vd in a shop and conclude it sounds great and that the specs tell you it'll be loud enough, and then have an epic fail at your first rehearsal.

The other approach would be to try to get excursion limited power handling figures and low frequency sensitivity figures for everything. But once you have them you then need to use logarithms to work out the resulting max SPL, which really isn't rock and roll. But I think everyone understands cubic centimetres (ok, apart from the Americans... )

Alex