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Need help understanding power ratings...


bassickman
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[quote name='Lord Sausage' timestamp='1340732602' post='1708865']
....Can you clarify this? Does that mean of the 250w only 150w get efficiently used?....
[/quote]

They're not helping are they!

The output of your 500 watt amp will split evenly between two 8 ohm cabs, so each of the 300 watt cabs will get 250 watts. But as you probably won't be running flat out you'll be ok.

I run a 500 watt amp into 2 300watt 112 cabs and I can play very loud with no trouble.

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[quote name='Mr. Foxen' timestamp='1340741334' post='1709073']
Its the biggest number, so the most impressive. The fact you consider it when thinking of buying an amp is all of the reason.

The important information is a maximum SPL chart, and an SPL at a given input voltage chart, so you can see if it goes as high and low, and in the middle as you want with the amount of power you have. The generalised versions of these are the sensitivity rating, which tells you how loud, and the min/max frequency range, but both those are a bit fiddly and only useful for comparing cabs among one manufacturer, since they all fiddle them in different ways. The charts are harder to fiddle without it being obvious. Lots of manufacturers don't supply them, but plenty of people pay money without knowing what they are getting so it works fine for them.
[/quote]
So what region should you be looking for in SPL charts

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[quote name='Lord Sausage' timestamp='1340822579' post='1710188']
So what region should you be looking for in SPL charts
[/quote]First you have to find them; AFAIK no one reveals them. The official reasons why are 'we don't want to confuse players with information they might not understand (calling you stupid they are) and 'people buy our cabs based on how they sound, not how they chart'. But they don't explain how people are supposed to know how they sound before they buy them if they can't try them first. The real reason for there being no charts is either they don't want you to see them, or they don't have any. Or both.

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[quote name='Bill Fitzmaurice' timestamp='1340826600' post='1710256']
First you have to find them; AFAIK no one reveals them. The official reasons why are 'we don't want to confuse players with information they might not understand (calling you stupid they are) and 'people buy our cabs based on how they sound, not how they chart'. But they don't explain how people are supposed to know how they sound before they buy them if they can't try them first. The real reason for there being no charts is either they don't want you to see them, or they don't have any. Or both.
[/quote]
thanks

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[quote name='Bill Fitzmaurice' timestamp='1340826600' post='1710256']
First you have to find them; AFAIK no one reveals them. The official reasons why are 'we don't want to confuse players with information they might not understand (calling you stupid they are) and 'people buy our cabs based on how they sound, not how they chart'. But they don't explain how people are supposed to know how they sound before they buy them if they can't try them first. The real reason for there being no charts is either they don't want you to see them, or they don't have any. Or both.
[/quote]

Seems legit. If I was marketing a new cab, esp. a sealed cab... and wanted to show it could produce lots more lows at less watts than most sealed cabs... I'd give a chart because that'd be the hardest thing to argue against.
I think it's because they want to be able to call all of their products great, but not provide precise ways of comparing them to both other options within and without the company. Not dishonest but showing a weakness as far as disclosure. Assuming they have the data if they don't they must be copying someone who does, or going through a looot of trial and error!

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[quote name='PlungerModerno' timestamp='1340882658' post='1710938']
Seems legit. If I was marketing a new cab, esp. a sealed cab... and wanted to show it could produce lots more lows at less watts than most sealed cabs... I'd give a chart because that'd be the hardest thing to argue against.

[/quote]You'd think, but what would you compare it against? The major problem is that the response of most bass cabs drops off around 80Hz. That's normal. The expectation of users is that they should be flat to 40Hz or lower. No manufacturer wants their response charts to reveal that their cabs don't meet that expectation, so they don't make charts available. Most manufacturers also quote sensitivity measured in the vicinity of 1kHz, where it doesn't matter, instead of 100Hz, where it does. SPL charts would reveal the truth, a truth that they don't want revealed. What is the truth? Have a look:
http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2357
http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2362
http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2374

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[quote name='Bill Fitzmaurice' timestamp='1340885816' post='1710998']
You'd think, but what would you compare it against? The major problem is that the response of most bass cabs drops off around 80Hz. That's normal. The expectation of users is that they should be flat to 40Hz or lower. No manufacturer wants their response charts to reveal that their cabs don't meet that expectation, so they don't make charts available. Most manufacturers also quote sensitivity measured in the vicinity of 1kHz, where it doesn't matter, instead of 100Hz, where it does. SPL charts would reveal the truth, a truth that they don't want revealed. What is the truth? Have a look:
[url="http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2357"]http://billfitzmauri...php?f=12&t=2357[/url]
[url="http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2362"]http://billfitzmauri...php?f=12&t=2362[/url]
[url="http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2374"]http://billfitzmauri...php?f=12&t=2374[/url]
[/quote]

Too true. You'd need at least two manufacturers giving the info for a comparison.
Except for comparisons within a range... like two cabs from the same manufacturer....

For bass & guitar cabs the manufacturer 'tone not technical' approach might be right for some customers, however the fact that not all PA & monitor cab makers give crucial data for users to compare is shameful.
Any bass or guitar cab / amp manufacturer worth their salt knows many bands, and individuals use effects and mixes that rely on pretty much studio monitor flatness for best results. Much more commonly they will change needs over time.... and rather than 6 different rigs over time, 1 fully capable rig would be a better idea, especially because it can be used again and refurbished.... Something tells me the best cabs of today will be rocking for a long time!

I think it's complacency and marketing fallout that prevents a lot of manufacturers giving the true full capacities of their products.
They also reserve the right to 'uprgrade' and 'retrofit' their products... so if they were to give response curves they would likely quote a large inaccuracy and overstate the performance, stating this was representative of the whole, but as an average your cab mightn't quite reach that performance level. This is distinct from fEARful, and your(BFM) cab design inaccuracies in performance as DIY cabs have loads of variables that make most of them unique.

It's cool there are lots of choices today, but It's painful to see only a tiny fraction give decent info. As people who invest sometimes mountains in sound gear... we should choose based on the information we have, not what we assume due to lack of information. Reliability of information is another issue. It's painful to read the TB threads about a certain micro head that uses compression T'Cheat higher wattage... :o

P.S. good chart data.

I'm willing to bet the Barefaced compact I have on order has a curve along the lines of [b]the Eminence Omega Pro 15 w/tweeter, loaded in a 4 cu ft (net) cabinet, tuned to 40 Hz.[/b] @ [url="http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2374"]http://billfitzmauri...php?f=12&t=2374[/url]
minus the high end extension....
[url="http://barefacedbass.com/uploads/barefaced-cab-specs-jan2011.jpg"]http://barefacedbass.com/uploads/barefaced-cab-specs-jan2011.jpg[/url] kinda gives me near chart like info.
[url="http://barefacedbass.com/technical-information/interpreting-tech-specs.htm"]http://barefacedbass.com/technical-information/interpreting-tech-specs.htm[/url] seems fairly on the money.

I'm not trying to start a nit picking battle. Barefaced isn't perfect, but it does give the info needed to compare cabs... to a large extent. If I were an audio pro I might need more, but I know the emphasis on flat response and honest numbers that some manufacturers are making is a change for the better.

Edited by PlungerModerno
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[quote name='PlungerModerno' timestamp='1340890776' post='1711116']
.............Any bass or guitar cab / amp manufacturer worth their salt knows many bands, and individuals use effects and mixes that rely on pretty much studio monitor flatness for best results. Much more commonly they will change needs over time.... and rather than 6 different rigs over time, 1 fully capable rig would be a better idea, especially because it can be used again and refurbished.... Something tells me the best cabs of today will be rocking for a long time!..........
[/quote]

This is kinda obviously from the perspective of the user, not the seller. Most manufacturers want to sell their customers multiple units, over and over again!!!!!

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So something like this then,

[url="http://www.thomann.de/gb/harley_benton_bb410t.htm"]http://www.thomann.de/gb/harley_benton_bb410t.htm[/url],(I'm not thinking of buying it!)

even tho it seems quite impressive, decent frequency response, 500w,
does it mean it will be prob be hiding something? For instance it just saying 102db for Spl won't mean anything and it could perform badly at different points. I mean the price is obviously a giveaway, but that will be more than just build quality, right?

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[quote name='Lord Sausage' timestamp='1340896708' post='1711223']
So something like this then,

[url="http://www.thomann.de/gb/harley_benton_bb410t.htm"]http://www.thomann.d...nton_bb410t.htm[/url],(I'm not thinking of buying it!)

even tho it seems quite impressive, decent frequency response, 500w,
does it mean it will be prob be hiding something? For instance it just saying 102db for Spl won't mean anything and it could perform badly at different points. I mean the price is obviously a giveaway, but that will be more than just build quality, right?
[/quote]

Firstly I have a Harley Benton Combo, and It's OK, but definitely built with budget components.
102dB SPL might be an accurate value... but at what frequency? The 40 - 17k Hz Range too could be very useful info if they included the roll-off 'metric', in other words is it -10dB at 40Hz.... or -3dB. Big difference. without a curve or clearly defined data points you may as well give a verbal description with no actual values. IMO.
Also the 500W value must be taken with a pinch of salt. That's more than likely 2 - 4 times over the typical acceptable distortion power values... in practice. I'm kinda paraphrasing this: [url="http://barefacedbass.com/technical-information/interpreting-tech-specs.htm"]http://barefacedbass.com/technical-information/interpreting-tech-specs.htm[/url]

I'm not very experienced, but am a 'believer' in the knowledge of acoustic engineers. If you've heard a full scale, perfectly clear, wonderfully loud P.A. you'll know why these ladies & gents are far closer to understanding than a marketing person. No offence :gas:

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[quote name='xgsjx' timestamp='1340897467' post='1711248']
The good thing about Thomann is that you can send it back if you don't like it. But your analysis is probably correct.
[/quote]

Yup. I forgot to mention my combo is MDF, prone to weak lows at moderate volume*, and Has OK tone. Not awful, and I'd expect the 410 to be the same, awsome for the money, but there's a reason they're half the price of most entry level 410's!

*The lows have to be heavily cut to avoid farting out. A budget 112 110W combo will do that..... :rolleyes:

Edited by PlungerModerno
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[quote name='PlungerModerno' timestamp='1340890776' post='1711116']
Any bass or guitar cab / amp manufacturer worth their salt knows many bands, and individuals use effects and mixes that rely on pretty much studio monitor flatness for best results. Much more commonly they will change needs over time.... and rather than 6 different rigs over time, 1 fully capable rig would be a better idea, especially because it can be used again and refurbished.... Something tells me the best cabs of today will be rocking for a long time!
[/quote]

It could be argued that there's already a product market catering to their needs complete with far more comprehensive available specs, under the label 'sound reinforcement'.
Also bear in mind that getting a sufficient understanding of the specs that contribute to good subjective sound quality requires considerable effort on the part of the end user, which is partly why there are professional sound engineers/technicians to run rigs rather than musicians. Why bother going to the (considerable) expense involved in proper testing when a majority of bassists will probably misinterpret the specs anyway?
A worst case is that manufacturers start focusing on a particular, easy to interpret spec like frequency response combined with max SPL that actually tells you rather little about the subjective capabilities of the cabs. People start focusing on the spec, manufacturers focus on getting that spec to look good at the cost of another aspect of the cab and the products end up worse not better!

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[quote name='LawrenceH' timestamp='1340898648' post='1711269']
It could be argued that there's already a product market catering to their needs complete with far more comprehensive available specs, under the label 'sound reinforcement'.
Also bear in mind that getting a sufficient understanding of the specs that contribute to good subjective sound quality requires considerable effort on the part of the end user, which is partly why there are professional sound engineers/technicians to run rigs rather than musicians. Why bother going to the (considerable) expense involved in proper testing when a majority of bassists will probably misinterpret the specs anyway?
A worst case is that manufacturers start focusing on a particular, easy to interpret spec like frequency response combined with max SPL that actually tells you rather little about the subjective capabilities of the cabs. People start focusing on the spec, manufacturers focus on getting that spec to look good at the cost of another aspect of the cab and the products end up worse not better!
[/quote]

Valid, very valid. I'd say the manufacturers can't help but maintain certain 'tone' requirements in their designs.
It would seem unlikely that a cab maker would ever use numbers alone to sell. Heavy cabs still sell for as much as near equivalent lighter ones... not always but the weight info helps sell the product in some cases. Maybe better, more trustworthy info about performance would help sell the same cabs too...
I do agree the negatives of that approach currently out weigh the strengths for the maker, but we'll see how things change in time.
The 'sound reinforcement' you mentioned is no doubt the extension of traditional PA, Studio, and new technologies in processing live audio... cool stuff, but there is a need for, as you said, highly knowledgeable technical skills to use these tricks well.
I agree most bassists will have an incomplete understanding of the specs... like me they don't feel the need to go into it in a lot of detail. But a graph would give a lot of users the ability to judge a good, balanced cab from a very trebly one. If most manufacturers gave the full story, then people would suspect the ones that didn't of having something to hide... maybe. Ideally it wouldn't be the manufacturer, it'd be an independent tester.... but then where do they get their 'cut'?

I'm not convinced there is a win win solution.

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[quote name='Bill Fitzmaurice' timestamp='1338828840' post='1679761']
The watts just don't matter, you have to increase them by a factor of ten to sound twice as loud. Always buy 8 ohm cabs so that if you need to add a second you can. And the last thing you'd add to a 412 is a 115, a 115 can't even keep up with a 212.
[/quote]
[quote name='Lord Sausage' timestamp='1338829278' post='1679763']
So what do 1x15 give you then is it more low frequencies or is that bollocks! Just to be clear then, a 500w amp that only gives out 350 due to ohms would be plenty loud.
[/quote]
[quote name='Bill Fitzmaurice' timestamp='1338830436' post='1679776']
Bollocks. Cone size in and of itself only affects one function, the angle of dispersion, The larger the driver the narrower the angle. All other aspects are determined by the driver specs. Same specs, same results, no matter what the cone size.
[/quote]
This is similar to a post i've just done on another thread, I went into amusic shop with all the extra knowledge garnered off you fine people. I was talking to a saleman. I was looking at an Ashdown 4x10. He said if i buy it to then at a later date pair it with a 1x15 to get the low frequencies. i asked about what the frequency response of the cab was. He didn't know what it was, or meant i think, then went and looked it up on the internet.

Thanks basschat!! :D

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[quote name='Lord Sausage' timestamp='1341072360' post='1713535']
i asked about what the frequency response of the cab was. He didn't know what it was, or meant i think, then went and looked it up on the internet.[/quote]That's part of the problem. Then there's the manufacturers, who not only don't discourage the false notion that a 1x15 can go lower and/or as loud as a 4x10, they foster it. Why? Because that combination sells. Whether it works well or not doesn't concern them.

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[quote name='Lord Sausage' timestamp='1341072360' post='1713535']
This is similar to a post i've just done on another thread, I went into amusic shop with all the extra knowledge garnered off you fine people. I was talking to a saleman. I was looking at an Ashdown 4x10. He said if i buy it to then at a later date pair it with a 1x15 to get the low frequencies. i asked about what the frequency response of the cab was. He didn't know what it was, or meant i think, then went and looked it up on the internet.

Thanks basschat!! :D
[/quote]

That's what you get with marketing logic. "But.... the famous people do it so it must be right!"

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True. If it wasn't for the development of Very good PA systems and sound management... the old stacks weaknesses would be more obvious. a 215 or 412 stack can still be super legit, and indeed ideal.

Stacks not Stax. I cannot say a bad thing about the late Duck dunn or Jackson Jr. Also the others were great too: [media]http://www.youtube.com/watch?v=JjmeoSL3Y3E[/media] B)

OH and the rest of Sam and Dave: [media]http://www.youtube.com/watch?v=FG2vn7R6Mzs&feature=endscreen&NR=1[/media]

Now that's a show I'd give a lot to see!!!

Edited by Hamster
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