Powered PA Speaker As Bass Amp

[Steve Browning]

I think that the longer the thread, the less likely it is to be read (or searched). Any speaker related thread is going full of 'my set up is best' 'buy Barefaced' and the like.

I wonder if there's any worth in identifying our experts (Phil Starr and Bill Fitzmaurice come to mind) who have the qualification to answer such questions from a technical standpoint. Everything else is the opinion of people with different ears/experiences. No idea how that would work but you could build up a compendium of useful 'articles' with the opinions of those who have a more objective standpoint.

Everyone wants to help. I get that but some can help more!

[stewblack]

3 hours ago, Happy Jack said:

We are, aren't we? We're actually going to re-do the entire FRFR topic less than a year after it ran to 97 pages (or whatever).

That certainly was not my intention. In fact I opened by saying I understand why and how they're used I just wanted to know how to choose one if you wanted to buy one. 

Might start one about whether compressors actually do anything next. 

[stewblack]

3 hours ago, Steve Browning said:

I think that the longer the thread, the less likely it is to be read (or searched). Any speaker related thread is going full of 'my set up is best' 'buy Barefaced' and the like.

I wonder if there's any worth in identifying our experts (Phil Starr and Bill Fitzmaurice come to mind) who have the qualification to answer such questions from a technical standpoint. Everything else is the opinion of people with different ears/experiences. No idea how that would work but you could build up a compendium of useful 'articles' with the opinions of those who have a more objective standpoint.

Everyone wants to help. I get that but some can help more!

But we all have our favourite experts though. 

🤦🏼‍♂️ 

[Steve Browning]

3 minutes ago, stewblack said:

But we all have our favourite experts though. 

🤦🏼‍♂️

True. I wondered the value of the post after making iit.That said, a 97 page thread is not going to have a high percentage of useful content. 

[stewblack]

2 minutes ago, Steve Browning said:

True. I wondered the value of the post after making iit.That said, a 97 page thread is not going to have a high percentage of useful content. 

What you said made perfect sense. I was kinda joking.

If this thread now shuffles off quietly having served its purpose then fine. If it runs to 97 pages and goes over stuff already covered elsewhere - so what? That's how the Internet works. 

[Jack]

22 hours ago, Nobatron said:

A QSC K12.2 is currently £795 from Thomann.

FWIW I just bought a paor on Sunday from Turnpike. £670 each and they come with the free tote bag.

 

I agree that specs don't tell the whole story. Some speakers are just better than others at handling bass, something that the vast majority of them aren't designed to do. Some of the bigger speakers (RCF 745 springs to mind) are designed to actually handle low bass, most aren't. I think if you're the kind of person who uses loads of stage volume or who often has to carry the room from stage gear then you either need to specd big bucks on the FRFR or just cart a mini pa everywhere just for you.

 

That's not really their use case though, most people using FRFR for bass (including me) have decent pa support and we're just using the FRFR for stage sound. And in that case you don't want a lot of lows.

[stewblack]

6 minutes ago, Jack said:

FWIW I just bought a paor on Sunday from Turnpike. £670 each and they come with the free tote bag.

 

I agree that specs don't tell the whole story. Some speakers are just better than others at handling bass, something that the vast majority of them aren't designed to do. Some of the bigger speakers (RCF 745 springs to mind) are designed to actually handle low bass, most aren't. I think if you're the kind of person who uses loads of stage volume or who often has to carry the room from stage gear then you either need to specd big bucks on the FRFR or just cart a mini pa everywhere just for you.

 

That's not really their use case though, most people using FRFR for bass (including me) have decent pa support and we're just using the FRFR for stage sound. And in that case you don't want a lot of lows.

Thank you. That explains it perfectly. 

[4000]

I think the conclusion I came to, for the time being at least, was that using a pa speaker was probably going to be more problematic than using my rig. I use 2 x BF One10s, max; in fact I usually use one. It weighs about 15lb. Plus micro head, what, 8lbs? Can tweak easily on the fly and sounds right pretty much from the off. A pa speaker would generally weigh more and I’d spend a lot more time tweaking to get my (admittedly very coloured) sound, especially given I hate what tweeters bring to the table. I can set up my rig in probably a minute and it weighs nothing. So unless I have some sort of epiphany then for me, it just isn’t really worth it. On bigger stages, it may be a different kettle of fish, but we seldom play them. Heck, many of the gigs we play I can backline with a single One10!

[Bill Fitzmaurice]

Or not. FRFR can apply to a small 1x10 PA main. It can also apply to a 2x15/2x6/tweeter monster. Most PA mains are FRFR, but by no means are most FRFR speakers PA mains. The confusion over this explains why this long dead horse continues to be beaten to excess.

[stewblack]

21 minutes ago, Bill Fitzmaurice said:

Or not. FRFR can apply to a small 1x10 PA main. It can also apply to a 2x15/2x6/tweeter monster. Most PA mains are FRFR, but by no means are most FRFR speakers PA mains. The confusion over this explains why this long dead horse continues to be beaten to excess.

It may frustrate you Bill, and be a 'dead horse' to you but to those of us who are interested in the subject it is a fascinating topic. The two above yours were illuminating, useful and interesting. 

If it annoys you so much and no one seems to respond to your input it is a little odd you keep returning to the thread. 

Edited August 7, 2020 by stewblack

[Jack]

Just as with everything from craft beer to god, some people are happy to let you be and some people want to convert you. As much I usually dislike people making their posts too personal and therefore not applicable to others, I think in this particular thread it's important. If you don't want to see me blather on about myself for two paragraphs then feel free to move on.

 

Personally, I'm on my third modelling solution and second set of FRFR cabs. Just like with proper amps it takes a while to see what works. For me, my bands have good pa support so I don't need much stage volume. Secondly I sing backing vocals so I'd ideally have a monitor anyway. Then, I own a decent mixer rack so having a nice set of pa cabs allows me to have my own pa system. Lastly (that I can think of for the moment anyway) having pa cabs allows me to use my skinny guitar, electric drums and girlfriend's keys/synth collection equally well on stage if I ever needed to. Ok, I'm NEVER playing drums on a gig but I have played a few on guitar.

 

The guy who occasionally deps for me in one of my bands (the previous bass player, he lasted one gig) plays bass and that's it. He shows up with a Sire Jazz, a clip on tuner and a sweet 1x12" Markbass combo. For him, having a bass rig is certainly a smaller and easier solution than using an FRFR type solution. On the other hand I'm a full time member and so I'm supposed to be making some kind of effort to get the sounds/effects right for the covers, hump my part of the PA (mixer rack), sing backing vocals and run sound during a show. I could bring a bass, effects board, amp and vocal monitor. And then all the cables! Oh the cables! But for me, in my particular band, helix>wedge is smaller and neater. That one wedge does bass and vocals for the stage, and seeing as I'm bringing a mixer and being the soundguy anyway I can make sure I sound good out front.

[Baloney Balderdash]

On 06/08/2020 at 16:01, Happy Jack said:

We are, aren't we? We're actually going to re-do the entire FRFR topic less than a year after it ran to 97 pages (or whatever).

As someone who weren't on this forum a year ago and who have no intention of looking through the entire archive of threads on here, I for one personally really appreciate this re-run of the topic, as I actually am pondering going this way myself, also new people might have some new input to the topic, as well as new solutions might have hit the market since then.

I honestly don't see the problem, lots of topics on this, as well as just about every other forum on the internet, are taken up frequently and rarely anyone complains, unless it happens to be one of almost identical noob topics that recurrently keeps being posted with what seems to be a weekly basis, then you'll usually see a couple of complains, as well as some people getting a laugh at the expense and much to the confusion of the genuinely ignorant and unaware OP.

This topic however doesn't seem to be one of those, on the contrary, to me it seems to be a very useful topic of the times we are in, perfectly in line with the turn the evolution of bass rigs have taken in recent years, with a wide variety of preamp pedals hitting the market, a fair deal of those with build in cabinet simulation, and high quality digital multi effect units with quite realistic amp modeling and IR cab simulation capabilities, and generally more and more bass players moving away from the classic bass amp + bass cab setup to something more practical and mobile.

@stewblack  Know that you started a, not only very useful for me personal in the kind of situation I am facing at the moment, but in my opinion very useful topic for a lot of the bass players of today, my appreciations for that, thank you. 

Edited August 7, 2020 by Baloney Balderdash

[Rollin Thunder]

Best of both worlds Tech 21 deuce delux, FRFR but looks and feels like a traditional cab got a 3 band eq HPF & LPF, really brought out all the subtleties on my Helix Stomp, loud 200w if required for stage volume Di in and out. 

Had mine a couple of weeks really impressed. 

Edited August 7, 2020 by Rollin Thunder

[4000]

I think the point about also doing backing vocals is important, as I also do bv and the occasional lead. Our current vocal monitors just aren’t great for bass, or certainly the sort of bass sound I like, so although I do go monitors only quite often I’m not happy with the bass sound when I do. We used to have another monitor that we used on my side, which was better - although not great - for bass, but not really that great for vocals, so we ended up getting rid. I guess at some point it may be worth biting the bullet, spending the money and replacing one of our current monitors with something that works better all round, at which point it may make sense to also eliminate the bass rig, for some gigs at least. The thing is, it would still have to be small and not too heavy. 

Given I’ve already stated we’re an acoustic band with cajon, and my backline is normally pretty small, if anyone can suggest a good quality small monitor that will work well for (slightly driven) bass as well as vocals I’d certainly be interested to hear about it. 

[Baloney Balderdash]

On 04/08/2020 at 20:52, Baloney Balderdash said:

I am about to make my bass rig mobile, and I have pondered on at some point buying an active PA speaker, just to have something in place of an amp.

The one I have in sight is the ralatively cheap The Box PA 502 A.

Judging from the specs at least it ought to be be able to handle bass fairly well.

15" 300W woofer and 100W tweeter, with a frequency response that claims to be 35Hz to 20kHz (-10dB)/40Hz to 18kHz (-3dB), which should mean that as long as you will not need to go lower than the low E of a standard tuned 4 string bass, it should reproduce it quite well.

That's in theory though.

But if these numbers are legit some dedicated bass cabs in existence got worse low end response.

 

Here's a link to it from Thomann:

https://www.thomann.de/gb/the_box_pa502a_aktives_fullrangesystem.htm?ref=intl&shp=eyJjb3VudHJ5IjoiZ2IiLCJjdXJyZW5jeSI6IjQiLCJsYW5ndWFnZSI6ImVuIn0%3D 

 

And here's a link to the manual:

https://images.static-thomann.de/pics/atg/atgdata/document/manual/160815_c_160815_r2_en_online.pdf

 

 

 

@Bill Fitzmaurice @stewblack

 

Assuming they are not just making up these numbers, even if some might claim that it is impossible with the size and shape of this PA speaker's (The Box PA 502 A) cabinet, as I wrote the stated frequency response number in the low frequency range for the active PA speaker I suggested in the above quoted post is -3dB at 40Hz (I got those numbers from the manual I linked to), whereas, just as an example, the corresponding stated numbers for the Ampeg PF-115LF and PF-115 HE Portaflex real bass cabinets, each equipped with a 15" speaker unit, like the PA speaker in question, are -3dB at respectively 57Hz and 50Hz.

Make of it what you want, but it personally makes me doubt weather the claims about this particular PA speaker in question not being able to reproduce the low end of a bass properly are in fact really also the actual truth. 

Not saying that the people stating it as a true fact doesn't know what they are talking about or that they are not right, just saying that from me looking and comparing, and judging exclusively by the stated numbers of this PA speaker and various real bass cabs, some by big acclaimed bass gear brands, and me knowing relatively little about the science of acoustics, it personally very much confuses me and makes me in serious doubt who to trust and who would be right here,.

Though for sure looking at the most common stated numbers for most other full range PA speakers using a 15" woofer unit it does indeed seem, again only judging by the stated numbers, that most of them would in fact struggle with reproducing the lowest bass notes properly, however, assuming the stated numbers can in fact be trusted, that doesn't seem to be the case for this particular one.

Now I do understand the incitament of the manufacture to paint up improved erroneous facts about their products capabilities, on the other hand as far as I know for one that would be illegal (since this would not just be vague and inconcrete exaggerated promises, but directly misleading very specific information that can be measured and verified), and secondly also put both said manufacture and the people distributing and selling their units, and repeating these stated numbers, in a bad light, if they in fact are just made up.

Edited August 8, 2020 by Baloney Balderdash

[Bill Fitzmaurice]

-3dB at 40Hz or any other frequency is meaningless in and of itself. I can show you 6 inch loaded speakers that are legitimately -3dB at 40Hz. The problem is that they only have 85dB/w sensitivity. Search: 'Hoffman's Iron Law'.

[Baloney Balderdash]

41 minutes ago, Bill Fitzmaurice said:

-3dB at 40Hz or any other frequency is meaningless in and of itself. I can show you 6 inch loaded speakers that are legitimately -3dB at 40Hz. The problem is that they only have 85dB/w sensitivity. Search: 'Hoffman's Iron Law'.

Yes, but I assume the stated numbers is the measurements for the entire unit, and not just specifically for the 15" woofer, to me anything else wouldn't make much sense, as that indeed would say very little about the actual capabilities of the unit as a whole, and practically make the stated specs completely meaningless and useless.

It would be like selling a car stating the top speed of it by how fast it is theoretically possible to roll the wheels when detached from the car.

That can't possibly be how it is actually done, can it really?

And in case they did in fact chose to state numbers that would actual make sense, be useful, and actually really inform about the actual capabilities of the unit as a whole, then I would think, even if it's sensitivity was really only being 85dB/w, that it would just be a matter of turning up the volume higher, as that would just mean it would be quieter at a certain amount of watt than a unit with higher sensitivity, right?

Edited August 8, 2020 by Baloney Balderdash

[TwoTimesBass]

To drag us away from physics for a moment and give my 2 cents to @stewblack 's OP; no, I'd ignore the spec's. As we've seen here there's a lot of interpretation involved and no real ISO or BS standard test that manufacturers subscribe to for the published info. In the day job I've spec'd a lot of PA for hire and capital purchase clients, and it always comes down to three things. Can they afford it, can they lift it, do they like the way it sounds? Price, practicality and performance... And if you're not sure beg, borrow and steal to get all the contenders the same room, with you plugged in playing your bass, and then decide. And once you've purchased neither evangelize for, nor take any criticism against your choice 😁

[Bill Fitzmaurice]

1 hour ago, Baloney Balderdash said:

 if it's sensitivity was really only being 85dB/w, that it would just be a matter of turning up the volume higher, as that would just mean it would be quieter at a certain amount of watt than a unit with higher sensitivity, right?

You can only turn the volume up so much before you either toast the voice coil or slam it into the back plate. Every 3dB reduction in sensitivity equals a doubling of power for the same output, assuming the amp has the required power to give. Your questions reflect the primary problem with specs. When they're incomplete what they don't reveal is usually more significant than what they do.

[nobodysprefect]

10 hours ago, Bill Fitzmaurice said:

-3dB at 40Hz or any other frequency is meaningless in and of itself. I can show you 6 inch loaded speakers that are legitimately -3dB at 40Hz. The problem is that they only have 85dB/w sensitivity. Search: 'Hoffman's Iron Law'.

And I bought ACME bass cabs because this was being explicitly said when almost no-one else making high-end bass cabs in 2004 did. It made sense to me, and the cabs behave as advertised. I may have quit physics, but I can still appreciate being told what tradeoffs are made in the design of a product.

What's the tradeoff in making high-excursion vs low-excursion cones? Accuracy of reproduction? The durability of the suspension? Weight? Difficulty of manufacturing? IIRC Acme said it's difficult to find a manufacturer that's willing to produce low-sensitivity, high-excursion drivers that have accurace low-end reproduction in the small-ish enclosure, but that may have been mostly about his buying relatively small amounts of drivers.

[Bill Fitzmaurice]

In general the higher the excursion the lower the sensitivity, although it's not a hard and fast rule, as excursion alone doesn't determine sensitivity. It's not easy to compare apples to apples here, but two drivers that use the same motor with different excursions are the Eminence 3012HO and 3012LF, at 6.2mm 100dB/w and 9.1 mm 95dB/w respectively. They also have different response, which is  related to their different excursion, but only in part, as other parameters affect the result. This goes back to the fact that be it a raw driver or a finished speaker you can't consider just one or two specs, you must consider them all. With raw drivers that's usually not a problem, as most driver manufacturers publish all the driver specs. With finished speakers it's usually not possible, as very few publish all the specs, if any.

[stewblack]

15 hours ago, TwoTimesBass said:

Price, practicality and performance...

Word 

[nobodysprefect]

3 hours ago, Bill Fitzmaurice said:

In general the higher the excursion the lower the sensitivity, although it's not a hard and fast rule, as excursion alone doesn't determine sensitivity. It's not easy to compare apples to apples here, but two drivers that use the same motor with different excursions are the Eminence 3012HO and 3012LF, at 6.2mm 100dB/w and 9.1 mm 95dB/w respectively. They also have different response, which is  related to their different excursion, but only in part, as other parameters affect the result. This goes back to the fact that be it a raw driver or a finished speaker you can't consider just one or two specs, you must consider them all. With raw drivers that's usually not a problem, as most driver manufacturers publish all the driver specs. With finished speakers it's usually not possible, as very few publish all the specs, if any.

Doesn't the math get ... 'non-trivial' also? Thanks for the informative reply

[Bill Fitzmaurice]

The math is quite daunting, if you do it yourself. Thanks to Bill Gates and other software developers you don't have to. Loudspeaker modeling software does all the heavy lifting.

[Phil Starr]

On 04/08/2020 at 19:52, Baloney Balderdash said:

I am about to make my bass rig mobile, and I have pondered on at some point buying an active PA speaker, just to have something in place of an amp.

The one I have in sight is the ralatively cheap The Box PA 502 A.

Judging from the specs at least it ought to be be able to handle bass fairly well.

15" 300W woofer and 100W tweeter, with a frequency response that claims to be 35Hz to 20kHz (-10dB)/40Hz to 18kHz (-3dB), which should mean that as long as you will not need to go lower than the low E of a standard tuned 4 string bass, it should reproduce it quite well.

That's in theory though.

But if these numbers are legit some dedicated bass cabs in existence got worse low end response.

 

Here's a link to it from Thomann:

https://www.thomann.de/gb/the_box_pa502a_aktives_fullrangesystem.htm?ref=intl&shp=eyJjb3VudHJ5IjoiZ2IiLCJjdXJyZW5jeSI6IjQiLCJsYW5ndWFnZSI6ImVuIn0%3D 

 

And here's a link to the manual:

https://images.static-thomann.de/pics/atg/atgdata/document/manual/160815_c_160815_r2_en_online.pdf

 

 

I don't know if you are still following this but I'll have a go at some of the things you might want to think about before going ahead with this as a purchase. First of all this is one heavy speaker/amp at 30+kg

The frequency response looks great but without a response curve it is hard to be certain. The -10dB/-3dB depends upon where in the frequency response you measure the 0dB point from but more importantly it is almost certainly measured at 1W not at 300W. As the power goes up the demands on the speaker get greater and few speakers can handle the excursion demands of full power at low frequencies. Excursion is the place where compromises are usually made in cheap PA speakers and that could be something that would show up if you use this one as a bass only cab.

The second thing to look at is the peak SPL (sound pressure level) of 120dB. That's going to be loud enough if it is a true measured value but it almost certainly isn't. The hint is the word 'peak' often the value is based not upon measurement but upon calculating the figure from the speaker's efficiency and the 'peak' power. This is often calculated to be four times the amp's actual power so the figure is 6dB down on the quoted figure 114dB. Sometimes it is only 3dB down so 117dB. 114 wouldn't be usable with a drummer and 117 would probably be struggling. Compare this with The RCF Art 312 from Thomann https://www.thomann.de/gb/rcf_art_312_a_mk_iv.htm which quotes 128dBpeak which should comfortably produce sound at 122dB. Even top brands like RCF use misleading 'peak' figures

A third issue is the amp, It's quite possible the amp driving the horn is a 100W amp but it almost certainly won't be a 100W driver. The amps are usually mass produced to go into a whole variety of cabs and then throttled back so that they don't blow a typically 30W horn driver. It's a perfectly sensible bit of design but the advertising people get hold of that figure once the engineers are finished and the ads are misleading.

 

All this is speculation of course. Without the speaker on a test bench I can't be certain and they aren't exactly lying, just misleading you. The Box are Thomann's own brand and have a decent reputation for value for money.  I've pulled apart a couple of these sorts of speakers and they are amazing value for what you pay. In this case it looks like they have traded the efficiency/loudness of the speaker for an extended frequency response and as cheap and cheerful PA speakers they are probably quite nice sounding. Used as a home disco for parties I'd guess they'd be great or even as a first PA for a band with not a lot of money. A couple of these might do you for bass but you are then up to the £500mark where you'd have better options. The RCF I linked will be lighter, louder and better sounding at only £40 more and I've used a pair of the 10" versions and they sound good. At £315 the 15" version, the ART315 might be a single speaker solution and the advantage of the RCF's are that they have DSP which won't let you overdrive the speakers.