Bill Fitzmaurice

[quote name='LawrenceH' timestamp='1341500534' post='1720115'] From a dispersion perspective I think it's better to cross as low as possible to avoid off-axis nulls due to destructive interference between drivers in the crossover region [/quote]That's much more of a concern with PA than electric bass. So long as you use at least 3rd order filtering on the midrange the response overlap zone is slight enough to minimize ill effects to the point of being virtually inaudibile, especially when compared to a typical commercial cab with woofers horizontally aligned and no midrange driver at all.

[quote name='dincz' timestamp='1341413832' post='1718602'] I suspect the answer will be no, but is there a standard for this e.g. +ve on the tip moves the cone out? [/quote]The standard is outward excursion with a positive voltage applied to the tip on a 1/4" plug or the + pole of a Speakon.

[quote name='4 Strings' timestamp='1341410777' post='1718545'] ...you mean like maple fingerboards sounding 'bright'. [/quote]Actually rosewood and ebony are brighter, being more dense than maple. More dense body woods are also brighter and sustain longer than less dense varieties. Here also there's nothing the least bit magical about it, it's simple physics. But as Clarke said any sufficiently advanced technology is indistinguisable from magic, even when that technology is as simple as a block of wood. If you're a luthier you understand the technology. If not you may not.

[quote name='dincz' timestamp='1341247347' post='1715719'] Just a thought. Correct me if I'm wrong but the potential problems with mixing cabs are to do with dispersion and comb filtering. [/quote]The main issue is the different phase responses of different cabs. When combined they may work OK, or they may not, and there's no way for the user to predict it. With identical cabs there are no issues. The theory behind mixed cabs, with tens and fifteens being by far the most popular configuration, is based on the notion that fifteens go lower, tens go higher, and that by combining them you get the 'best of both worlds'. The fly in that ointment is that fifteens don't necessarily go lower than tens, and tens don't necessarily go higher than fifteens. The only inherent difference is that tens do have wider dispersion in the mids and highs. But when tens are placed side by side their dispersion in the mids is halved, resulting in narrower dispersion than a fifteen, and the highs are combed. And where output capability is concerned one fifteen can't match four tens, so the ubiquitous 115/410 combination makes no sense from any perspective.

[quote name='Spoombung' timestamp='1341250160' post='1715783'] That sounds a bit high. I was thinking 400HZ - 1 KHZ: ie, midrange. I have a dull sounding speaker that could have more a clear midrange. It's a bit boomy. Just looking for a general pupose unit you can chain -up (link) with a bigger speaker really [/quote]There's no reason to cross lower than where the twelve starts to beam, around 1.2 to 1.6kHz. The reason for a mid driver is just as much dispersion as it is response. As for boom, that occurs down around 100 to 160Hz, so adding a mid driver wouldn't affect it. The causes of boom are a cab that's too small, is tuned too high, or is insufficiently damped, as well as a combination of any or all those factors.

[quote name='discreet' timestamp='1341243138' post='1715616'] Very good. I shall try to find out. It does mean buying another ABM and/or making another J12, though... [/quote]That's the issue, not knowing without the trying, and not having the means to do the trying.

[quote name='chris_b' timestamp='1341226173' post='1715288'] I spent the first 2 years on BC being told that mixing speakers sizes definitely never worked, when I was getting a great sound out of a mixed size rig![/quote]Show us the posts that said that. I know I never have, nor has Alex or any other qualified engineers. What we have said is that the results with mixed drivers/cabs are unpredictable, while with matched cabs you know what you'll get. [quote]How can any of us assume we know exactly how a manufacturer’s cabs were designed[/quote]Having designed many of them myself I don't have to assume anything. Designing cabs for a living I know that most manufacturers priorities are, in order of importance: 1. Profit margin 2. Graphics 3. Performance # 3 never takes precedence over #s 1 and 2. And I know that the only reason manufacturers push the concept of mixed drivers/cabs is because the average player thinks that there's some benefit to doing so. When faced with the options of saying "Don't do that" and potentially losing a sale to the next guy or giving the masses what they want, whether it's the best option or not, the almighty buck/pound is the ultimate arbitor. [quote name='discreet' timestamp='1341234575' post='1715456'] My 2p: I always believed mixed speaker sizes/ratings to be a no-no as well... seems quite logical to me, but through necessity I used an ABM 410 and a BFM J12 together at rehearsal recently and I have to say it sounded extremely immense - and that's the bottom line, isn't it? [/quote]Virtually any two cabs together will sound better than either alone. What you don't know is whether you'd have had a better result with two ABM410 or two J12.

[quote name='Lozz196' timestamp='1341097827' post='1713916'] Agreed. But a 212 mathematically is the same area as 310 (well about 98% if I remember correctly). [/quote]That depends on the displacement of the individual drivers, and by no means are all tens the same, nor twelves, or any other size.

[quote name='Lozz196' timestamp='1341078287' post='1713645'] Surface area wise, a 212 is virtually equal to a 310, in the amount of air being pushed - [/quote]Surface area doesn't matter. http://barefacedbass.com/technical-information/Volume-displacement.htm

[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.

[quote name='Fubar' timestamp='1340993260' post='1712661'] This has the effect of making the cab 'think' it's bigger than it really is. [/quote]Myth, though a very widespread one. Sufficient stuffing will lower the Q of a cab, which can tame boom, which is [i]similar [/i]to the effect of a larger cab. But it's not the same, as a larger cab also gives lower response with higher sensitivity. And you only stuff a sealed cab, never a vented cab. Stuffing a vented cab will upset the box tuning.

[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

[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.

Read this, and all the other bits on the site. It will answer not only most of the questions you already have but also quite a few that you haven't thought of yet. http://barefacedbass.com/technical-information.htm

[quote name='icastle' timestamp='1340729535' post='1708781'] Stop apologising The 500W will be split between the two cabs, so a pair of 300W cabs will get 250W each. [/quote]And since most 300w cabs can only make use of perhaps 150w each you'll still have plenty of amp headroom.

[quote name='Musicman20' timestamp='1340660211' post='1707846'] I think ALL engineers, no matter how difficult they find it, should find time to get the aesthetics right. Heck, they are probably missing a huge chunk of the market. [/quote]Gettting it right? Or getting it familiar? Just because bass cabs have looked pretty much the same since 1960 doesn't mean that's how they s[i]hould[/i] look, at least not if their main purpose is to be listened to. Not that they need be ugly, like these close relatives of Daleks: Those who can afford the hundred thousand quid a pair go for must not be bothered by their look any more than the likely Picasso on a nearby wall.

[quote name='Dave Tipping' timestamp='1340575348' post='1706584'] before if you knocked on the cab it sounded pretty hollow..Now it sounds solid with a high pitched knock. [/quote]The tecnical name for that is 'the knuckle test'. Using it on any cab you're considering is a good idea, as is using it on any you already own.

[quote name='Dave Tipping' timestamp='1340570369' post='1706461'] Cheers for the compliments lads, had a good play with it today and it's pretty incredible the improvement. [/quote]Good show, and it goes to this quote from your original thread: [quote]if your Laney hasn't got bracing then it probably doesn't need it and the same is probably true for the dampening material.[/quote] Ths fact of the matter is that speaker manufacturers are in the business of making profits, not making the best product possible and then selling it for peanuts. That often means cutting corners, and those corners most often cut are those that the buyer isn't aware of unless he opens the box up to see what he paid for, and in some cases didn't get. The good news is that putting in what the manufacturer left out isn't a bit difficult, and can as in this case have dramatic results for very little effort and cash.

[quote name='Mr. Foxen' timestamp='1339788888' post='1694523'] Get a bunch of distortion and compression if you put more in, so might be a win if you like that. Until they break. [/quote]True, and break they will. Guitar drivers are far more tolerant, as with their short xmax they distort around 10% of their power rating, leaving a lot more room between when they start to get nasty and give up the ghost.

[quote name='51m0n' timestamp='1339760667' post='1693844'] +1 excellent response Similar to the 500w of the TC Electronic amps is actually 300 (200??) and something watts with a load of DSP processing to make it seem louder. Tubes just do that processing for you in an analogue way. [/quote]+1, and by that same token you may use processing to get that same result with any SS amp. [quote] Bunch of that would be down to the 2x10 not actually being able to convert much more than 100w into spl. [/quote]+1. Few 210s can actually make use of even 150w, so anything more than that put in won't get any additional out.

The rear ported are that way because there's not enough room to fit them on the front. Larger box equals lower response with the same drivers used.

[quote name='Mr. Foxen' timestamp='1338897483' post='1680708'] That says a short causes no harm at all, which is as I said, low impedance is not an issue for damage concerns. [/quote]+1. Most tube amps use a closed circuit switching output jack that shorts the output if there's no speaker plugged in. That's to prevent damage from what really does bother tubes, which is no load. They're not happy with a load higher than the tap rating either, but a load lower than the tap rating is to a tube as water is to a duck.

[quote name='Lord Sausage' timestamp='1338829278' post='1679763'] So what do 1x15 give you then is it more low frequencies or is that bollocks! [/quote]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 name='Lord Sausage' timestamp='1338828441' post='1679756'] Also what about ohms? If you have say an amp that's 500w at 4ohms and 350w at 8 ohms and you run it thru a 4x12 that handles 500w at 8 ohms, i take it you'll get 350. If you add say a 1x15 cab that is 8 ohm would you still get 350 or do the ohms increase or decrease. Would i have to buy 4ohm cabs. [/quote]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 name='Lord Sausage' timestamp='1338802455' post='1679298'] Does it matter if the amp is more powerful than the speakers. [/quote]Only if it has no volume control.