Wiggybass

[quote name='alexclaber' timestamp='1349437460' post='1826267'] This doesn't matter when cabs are connected in parallel. Cone area alone doesn't tell you how much air a rig can move - you need to also consider cone excursion (and port area if that's a potential limitation). [/quote] That's an interesting thought. Is there a linear correlation between increased excursion and equivalent increase in effective radiating area? My first thought would be that greater excursion would just push the same amount of air harder, not that it would move [i]more[/i] air, but I'm willing to learn!

[quote name='Mr. Foxen' timestamp='1349436871' post='1826257'] Also missed that impedance varies with frequency as well as phase, and fairly sure that can make fun with mismatched cabs too, picturing a ported cab with the big impedance peak at a frequency where the paired cab is not sensitive, resulting in more power going to the less sensitive cab at that frequency. [/quote] Critical and excellent observation. Impedance varies [i]wildly[/i] with frequency, the main reason why impedances for both individual drivers and complete speaker cabs are usually stated as 'nominal'.

[quote name='stevie' timestamp='1349427084' post='1826085'] I'm afraid not. The only reason to change your 18 would have been to increase power handling (although even this is a bit moot). Otherwise, a 1 x 18 will work with a 4 x10 as well as another 4 x 10 – in many cases better, in fact, because 18s don't normally have an extended HF response and are thus less likely to cancel the mids/highs coming from your 4 x 10. [/quote] Replacing a single 18 with a 4 x10 should make quite a bit more racket because it will shift a lot more air. If we assume that the whole surface of a cone driver is active in terms of direct air displacement (it isn't quite but let's keep this simple), then one 18" driver has a surface area of roughly 176.71". A single 10" has a radiating area of about 78.54" so four of them working together will have 4 x 78.54" = 316.16" bashing the air out.

[quote name='alexclaber' timestamp='1349357409' post='1825226'] More later but there's more to out of phase than being 180 degrees out of phase (equivalent to reverse polarity). Any amount of phase difference will affect summing! [/quote] Of course! Here's a good explanation which goes beyond sinusoidal phase comparisions: http://www.sengpielaudio.com/calculator-timedelayphase.htm

[quote name='alexclaber' timestamp='1349357800' post='1825239'] Yes, re-reading your post Wiggy, you seem to have polarity and phase confused! Phase is continuously variable and all loudspeakers have varying phase response across their bandwidth because they are reactive electrical components (i.e. volts and amps do not move in simple synchrony). [/quote] Polarity describes an exclusively electrical relationship. Phase offset (expressed in degrees) is usually used in audio to describe whether two signals are phase-synchronous ('in phase') or whether and by how much they are asynchronous ('out of phase'). Any device that produces more than one frequency will exhibit varying phase response because phase measurements are frequency-specific.

[quote name='Conan' timestamp='1349354810' post='1825176'] For most people, this is enough. However, some of us like the science stuff. A few of us actually understand it (or some of it at least!). Some of us have even made our gear choices on the back of this science stuff. It works for us. It gets very wearing to be told, in every thread about cabs, that "I used this for years and it sounded good to me". Good for you, but don't question the ears of those of us who have noticed a difference after listening to the advice of the experts. Thank you all. [/quote] Well said sir!

[quote name='alexclaber' timestamp='1349337903' post='1824773'] The point I'm always trying to get across when discussing pairing mismatched cabs is related to their differing phase response. The best way to understand of this is to think about the pickups on a Jazz bass. Think of the neck pickup as being a cab with a more bassy sound and the bridge pickup as being another cab with a more trebly sound. The common assumption is that if you pair a bassy cab with a trebly cab you'll end up with a stack that does bass and treble well, whilst getting the mids from both - "best of both worlds". But what actually happens when you both pickups on full on a Jazz bass (or any other bass with two pickups in parallel)? You don't get the bottom of the neck pickup plus the top of the bridge pickup and the mids being a mix of both. You get the bottom of the neck pickup, the top of the bridge pickup but much less midrange than from either pickup! Why is that happening? It's happening because there are phase differences between the two pickup's output and so instead of all the output summing fully, some of the output sums partially, some of the output cancels partially and some of the output cancels fully. This is a good thing with bass pickups because it gives us a very different third tonal option on a two pickup passive bass. The same thing happens when stacking dissimilar cabs. Now on the one hand this isn't a problem if the end result is loud enough and sounds right. But on the other hand, the reason someone tends to buy a second cab is because they want to add something in terms of both tone and output to the tone of their existing cab and as the pickup situation illustrates, you won't get that tidy summing - you'll get partial cancellation so the resulting tone will be unpredictable and equally importantly the rig will be less efficient. There's also the matter of mismatched power handling and the cabs' response diverging further at high SPL when things become less linear, so the rig may perform worse and worse as you turn up - exactly when you don't want it to become less efficient! We designed the Compact and Midget to work together - the two drivers have identical motors and the cab alignments are such that the phase response is very close through the lower frequencies (where it matters - at higher frequencies the path length messes with the phase response whether you have identical cabs or not). [/quote] I wondered if you'd be brave enough to start exploring phase response on here ;<)! It's the most misunderstood and opaque area of sound to most people...good luck! In fairness that's an excellent explanation of what actually happens. Being the pedant I am, I'll add the following additional data: It's certainly true that the pickups on a twin-pickup instrument cannot be in-phase with each other at all frequencies (because they 'hear' the same string at different points along its length), and the classic sound of a Jazz bass relies on certain frequencies being partially cancelled, but technically they are not 'out of phase' either, because the description of any phase relationship can only describe one frequency at a time. For them to be 'out of phase', with each other i.e. separated by 180deg of phase, we'd have to identify the specific frequency which is affected by the physical distance between them. The half-wavelength of the frequency that corresponds to that distance will suffer the greatest cancellation (though it won't be total silence because of the harmonics and sympathetic resonances created by the structure of the bass. It would work if the bass produced a pure sine wave). [i]So, on a J-Bass we have two independent 'ears', 'hearing' a common source but from different locations.[/i] This is different to two drivers being driven by the same channel of amplifer. Assuming they are electrically in-phase (i.e. with matching hot / cold wiring), then both drivers will move simultaneously forwards on receipt of positive voltage from the amp. [i]So, in this case, we have two acoustic sources being driven by one signal.[/i] To the listener, standing in front of said cabs, any phase cancellation could be caused only by a difference in physical alignment in the vertical plane of the two drivers' acoustic centres, as you mention in your description of the Compact and Midget. Using a pair of identical cabs stacked straight would eliminate any phase cancellation because the drivers would be aligned in the vertical plane (which, of course, creates new issues for the same reasons - the frequency whose half-wavelength corresponds to the physical distance between the driver centres will now 'couple', providing in theory up to +6db extra output at that frequency, as happens with my Bergantinos). Consequently, it's entirely possible that a 1 x 15 beneath a 4 x 10 (even if the front baffles are in vertical alignment) would suffer varying amounts of phase cancellation at specific frequencies, simply because 15" drivers are deeper front-to-back than 10s, thus creating a discrepancy between the acoustic sources of each cab. This might sound good btw. And it might not. However, just to bring this back to earth a bit, we should also remember that: 1. Most backline amps are frequency-limited, i.e. they are fitted with high and low-pass filters to enhance their efficiency 2. Basses (in fact most instruments) produce a relatively limited range of frequencies, which makes life a lot easier for designers of backline 3. If you follow the rules of minimum impedance then you almost certainly won't damage your amp 4. If it sounds good to you, and nothing's blown up, then it IS good! Anyway, back to dispersion - I'll understand if it's still a trade secret but I'd love to know more about your thoughts on this because, as I said, it's a new one to me in backline terms.

[quote name='xgsjx' timestamp='1349291046' post='1824413'] Working with PA, you'll probably have the luxury of having amps & EQs for each type of speaker (having different ones for subs, mids & so on). The majority of the bassists on here use one amp to run either one or 2 cabs. Taking away anything else, if you're using 2 different cabs, then you're compromising either one or both as you try to EQ the best sound you can. If both cabs are the same, then they're both going to act fairly similar to any EQing that you need to do. Sorry I didn't respond earlier, too busy at work after lunch today to post. I think Alex is better at explaining things than me anyway (well, I should hope he is ). [/quote] That's a perfectly valid point, however, if you have two different configurations of cab from the same maker then one would [i]hope[/i] (note emphasis!) that said manufacturer has tested all possible combinations...!

[quote name='XPAULUSX' timestamp='1263904352' post='717724'] Hey, as you may have read from a previous thread i own a Trace Elliot AH300SMX. i managed to aqcuire this amp off a friend as it was broken and he had already replaced his entire rig with GK stuff. only paid 80 quid to get it fixed, good deal or what?! i'm cosidering upgrading my head at some stage with something else but was just wanting to know what kind of reputation my Trace has, is it worth keeping? Thanks Paul [/quote] I bought mine in about 1995-ish, gigged it hard, still use it from time to time and wouldn't part with it. Lovely kit.

Very sensible. I use a pair of Bergantino 1 x 12s which are rear-ported and they're fab but always need an EQ tweak depending on what's behind them. I can't see any numbers for dispersion in the specs - I'm looking for horizontal x vertical in degrees, did I miss it? I'm intrigued to know how you control this, sad geek that I am!!

(@ Alex) Yup, for sure, but I can't remember the last time I had the opportunity to put my bass backline in 'free space' at a gig - I wish I could! In practice it's always up against a wall, or a curtain, or whatever, but there's always something behind it whereas there is always plenty of free space in front, which is why I think that rear-ported cabs, in practice, are more reactive to their environment. I take all your well-made points about speaker parameters. I think the missing link here (and the fundamental difference between PA and backline) is that an instrument amp becomes part of the playing experience, is part of the 'feel' of it, plus the instrument and the amp contribute to the overall noise. In PA-world it's just not like that, for many reasons. Just out of interest, what is the difference in low-end frequency response between your most and least 'bassy' cabs, regardless of driver diameter? Also, I'm very interested in your comments about dispersion here... http://barefacedbass.com/technical-information/speaker-size-frequency-response.htm ...as it's not a concept that I've ever encountered in backline before. In PA-world (especially since the widespread adoption of line-source systems) it's still the major buzzword. Are you possibly referring to the frequency-specific acoustic coupling of adjacent drivers, [i]a-la[/i] line-source? Cheers!

[quote name='alexclaber' timestamp='1349278169' post='1824185'] That's as may be but Wiggy wouldn't be the first sound engineer who misunderstand some aspects of loudspeakers! This statement suggests a knowledge gap: "[color=#282828][font=helvetica, arial, sans-serif]As for variances between venues, again it depends. Reflex cabs are much more reactive to their surroundings than close or front-ported cabs, that alone would make a lot more difference than the size of drivers they contain. But surely that's what the EQ is for?[/font][/color] [font=helvetica, arial, sans-serif][color=#282828]Is 'reflex' cabs referring to rear-ported cabs then?[/color][/font] [/quote] Yes, sorry - to me reflex cabs are rear-ported, so what they're placed in front of makes a big difference. Serves me right for using slang - that's not the true meaning of 'reflex' in this context.

[quote name='xgsjx' timestamp='1349273161' post='1824084'] Have a wee read at these & things might make a little more sense to you. [url="http://barefacedbass.com/technical-information/speaker-size-frequency-response.htm"]http://barefacedbass...cy-response.htm[/url] [url="http://billfitzmaurice.info/forum/viewforum.php?f=10&sid=239e993b6a548da81514b45176b314cb"]http://billfitzmauri...514b45176b314cb[/url] Smaller drivers give a better dispersion than larger ones. 2 10" drivers vertically arranged in a cab the same size as a single 15" will give out a better dispersion. It's nothing to do with driver diameter on how low it can go, but how much it can move. The reason behind 15's & 18s is that cabs are cheaper to produce with a single driver. [/quote] Er...when did dispersion enter the conversation? Below 160Hz it's a completely random concept anyway because frequencies below around that are omnidirectional. Dispersion of LF can only be controlled by what's known as 'beam steering' and has nothing whatsoever to do with backline! I'm really sorry, but whoever told you that diameter has nothing to do with the respective driver's frequency response is talking right out of their rear hole. Also, and again I'm sorry, but the reasoning behind 15s and 18s being cheaper to produce is simply ridiculous. Perhaps using concert sound equipment was a bit esoteric (but that's my background) - let's look at hi-fi, the principles are exactly the same - here's a really simple hi-fi speaker: [url="http://www.richersounds.com/product/bookshelf-speakers/q-acoustics/2020i/qaco-2020i-gra"]http://www.richersou.../qaco-2020i-gra[/url] Now, why do you think that it has one driver larger than the other? And, what exactly is 'better' dispersion anyway? Wider? Narrower? Varies with frequency (which it does btw)?

[quote name='PaulWarning' timestamp='1349268111' post='1823997'] bloody hell, don't really understand that, but I do know when I connect my 15" speaker to my 2 x 10" combo it's got more grunt [/quote] LOL!!! It surely will, a/ because the amp is now delivering about 25% more power (assuming you're connecting an 8 ohm extension cab to a combo that's fitted with drivers providing an 'internal' load of 8 ohms, thus showing it 4 ohms overall) and b/ because it's moving more cardboard. And that's a good thing!

[quote name='xgsjx' timestamp='1349210433' post='1823454'] Sorry, but quite a bit of that sounds like you've been filled with marketing codswallop. The main reason you shouldn't mix driver sizes is that you'll get unpredictable results from venue to venue. As for 15s producing lower frequencies, it's just not true. Marketing gobcrappers would have you believe that, but if you go for decent drivers from the same manufacturer, the specs on how low a frequency it can produce have no baring on driver diameter & more so on how the cab has been designed. keeping to the same size drivers means you'll get a consistent sound from venue to venue. I'm not saying don't go for a 4x10 & a 1x15, but you won't really be hearing fully what the 15 is doing as the 4x10 would probably be drowning most of it out. [/quote] Hmmm...sorry, simply not true. This is physics and its principles govern all things regardless of marketing. Let's look beyond crappy, frequency-limited backline and into proper audio systems, like a big modern PA designed to deliver full-range audio to large crowds. In all modern systems the full frequency range is divided electronically into bands, usually four - HF, high-mid, low-mid and LF. HF is always produced by 1" or 2" compression drivers, the mids are usually tens or twelves and the LF is almost always some arrangement of EIGHTEEN inch drivers in ENORMOUS cabinets. Now, if all speakers could reproduce low frequencies with the same enthusiasm, why go to all this trouble? The answer, of course, is that they don't - they physically can't. The longer the wavelength you're looking to reproduce, the larger the device has to be. At 100Hz (the open G on a concert-tuned bass is 98Hz), the physical wavelength at sea level and 20 degC is 3.4 [i]metres[/i]. Yes, tens will do that but not with the same efficiency of a fifteen of equivalent performance and sensitivity. This of course all based on a one-speaker to one-speaker comparison. The practical issue comes down to how much cardboard moves in and out when you play, and thus how much air is physically displaced and then picked up by our lugholes. A 4x10 against a single 15 with the same amp power will be louder because it's moving more air but in frequency response terms it will not reproduce low frequencies as efficiently. Which incidentally explains why you're quite right about a 4x10 drowning out a single 15 - for those to balance in terms of physical loudness the 4x10 would have to be turned down a bit. As for variances between venues, again it depends. Reflex cabs are much more reactive to their surroundings than close or front-ported cabs, that alone would make a lot more difference than the size of drivers they contain. But surely that's what the EQ is for?

They do!!! http://www.markbass.it/product_detail.php?id=228

No reason why you can't carry the head around in a bag or something like that - Mark Bass make natty little carry bags for their smaller heads, don't know if they do for this one too. However - the advantage of a rack is that it will protect your gear in transit, and the rack is always cheaper than the kit it carries!

If you're serious about spending £500 on a DI box, try the Avalon U5 first. Absolute industry standard (and not just for bass either), built like a tank and sounds incredible.

No reason whatsoever why you shouldn't mix any speaker sizes you want so long as you don't go below the minimum impedance (stated in ohms) that your amp will safely drive. Going below that point will make your amp work very hard and likely shorten its life. Most bass amps I've used seem to be happiest working at 4 ohms, and will typically deliver about 25% more power than when working at 8 ohms. What size you prefer depends a lot on how you use them and what music you play. Fifteens react slower (marginally) but will reproduce lower frequencies (typically regarded as those below about 160 Hz) more readily, so can be good for the deep bass required in dub, reggae, house etc. Tens react faster (marginally) and will not 'go as low' as larger speakers, simply because there is less cardboard moving in and out, but personally I prefer them for reasons of both sound quality and portability. I used an Eden 2 x 10 plus 1 x 15 setup for a while and it was OK, but since I bought my first 4 x 10 I've not really used anything else. By far the loudest rig I've owned was an original Trace Elliot 300w head with two T-E 4 x 10s, which, despite the modest power of the amp, set off car alarms 50 yards away at half volume outdoors...

Possibly a bit late but I have to say that a Sansamp RBI would be the perfect solution if you can handle having an extra box. Advantages (not in any order): * Two electronically balanced outputs, wet and dry, so you can feed [i]exactly[/i] the sound you want (post-gain / blend / EQ) to the house PA as well as also giving them a dry feed if you want. * Duplicated wet / dry unbalanced outputs for connection to your own backline * Quality FX loop with choice of fully wet or 50/50 blend with original signal so you can run non-preamp based FX properly, or (as I do) connect a tuner for silent tuning * Instrument inputs front and rear, and it's footswitchable in / out * Really musical EQ with well-chosen frequencies for bass, a useful presence control and a sensible gain range able to produce fully clean to comprehensively nasty preamp overdrive from pretty much any input level * Very solidly built! I've used my RBI for years (in fact I have two) and can't imagine gigging without it. Couple of weeks ago I gigged at a local music venue and DI'd into their system as normal - at soundcheck the engineer asked me to play a bit, I did and he started smiling. I stopped and he said 'Is that a Sansamp?' I nodded and he said, 'Fantastic - they always sound great. Can we do the drums...?'