Bill Fitzmaurice

If an engineer gives you a DI to be placed before the amp an alarm should go off. Either he doesn't care about duplicating your tone in the PA or he's technically ignorant. The guys who know what they're doing and care how you sound will DI post-preamp if they can, and will mic as well, the one for the lows, the other for the mids and highs. Imagine what would happen if they expected a guitar player to go to a DI in any way, shape or form.

[quote name='Jack' timestamp='1497284450' post='3317029'] Hit them with plenty of input volume. [/quote]+1, that's the only time a valve will act all that much differently. IMO valves in the pre are only effective as a sales tool. The real 'magic' of valves happens when they're in the output stage.

[quote name='Freddie75' timestamp='1497052015' post='3315632'] Looking to upgrade the driver to 300/400 watts (8ohms) so it handles the pairing better. . [/quote]Higher thermal power capacity doesn't necessarily translate into higher output capacity. In some cases it can be less. If you need more than what the one RS212 will do your best best is to add another RS212, not a 112.

[quote name='DIYjapan' timestamp='1497001664' post='3315182'] 12mm or 15mm? [/quote]Properly braced 12mm is all you need. [quote]bagends look rugged as heck and they are thicker 18mm not 15mm. [/quote]Commercial cabs tend to use 18mm, because lower labor costs make it less expensive to build barely braced or unbraced 18mm than well braced 12mm. Besides, they don't have to haul the cab but once to the loading dock for shipping. The sweat equity invested in building a lightweight cab is repaid every time you lift it.

Damping doesn't take up acoustical space.

If designing speaker cabinets was easy everyone would do it. Just to complicate matters further, it looks like you're using WinISD Beta, or perhaps an old version of Alpha. I can't tell which from the photos, as they're too small to make out details, and in any event I haven't had either of those for quite a few years, so I have nothing to compare to. You should be using WinISD 0.7.0.950. http://www.linearteam.org/

Of the three I greatly prefer the green. The white will be boomy in the midbass and weak in the lows. What they don't show is response above 200Hz. That you can only find by comparing the charts on the Eminence data sheets. The Delta 12LF will be weak in the mids. You also should be looking at the SPL chart, not the transfer magnitude chart, which doesn't take into account sensitivity. For comparison this is the measured response of the 2512 plus tweeter in my Simplexx 12: You can see the midbass hump is slight, so boom won't be an issue, and the low end is stronger as well. You're also missing two charts that are of equal importance to the SPL chart, the maximum SPL chart and the rear port velocity chart. The port velocity chart, which needs to be calculated at the maximum power of the driver, tells you how large the port area must be to keep port velocity below 20m/s to eliminate port noise. Too much area isn't good either, it makes the port longer and therefore the cab larger for no reason.

Panel to panel braces can be made from whatever is handy. There are no flexing forces exerted on them, only compression and extension, so stiffness isn't required. When I use spline braces, only if there's no place to put a panel to panel brace, they're plywood, at least and inch and a half wide, because they do require as much stiffness as possible.

[quote name='Marty Forrer' timestamp='1496374873' post='3310886'] With all due respect to Mr Bill Fitzmaurice, I have just built a Greenboy Fearful 12/6 from scratch, not a kit. I have pumped 500 watts RMS of double bass signal (huge transients and organ re-arranging bass) and have no problem with the spine bracing. I will be stone deaf before I hear any rattles or vibration. Each to his own. [/quote]With all due respect, I've done extensive testing of both, in the same cab configuration, side by side. Panel to panel bracing is at least four times as effective as spline bracing, with less weight. Modal analysis bears that out, but I prefer to rely not on analysis alone. Your results may be acceptable, but unless you have built both configurations you have no basis for comparison.

I don't know about Linden, but American Basswood is too lightweight for speaker cabinets. It's considered a junk wood, not suitable for construction or furniture. It doesn't even burn well.

[quote name='Chopthebass' timestamp='1496070973' post='3308520'] I remember having a better experience at this venue with my two Jack 12's[/quote]Probably because the Jacks are much more sensitive in the lower mids than commercial cabs, and those lower mid frequencies are above the band width where null zones occur.. [quote]My GK cabs are the wedge shaped ones, so if I angle them will the crowd still hear them ? [/quote]They'll hear the lows that you don't. The mids and highs, maybe not, especially as they have rather poor dispersion in the mids and highs to begin with.

[quote name='Jack' timestamp='1496059700' post='3308428'] It's electrically the same as having a thicker cable, so if anything your amp would have a minutely easier time of it. [/quote]If anything the lower resistance of dual cables would lower the overall impedance load, and that might make things harder on the amp. OTOH if the cables are undersized to begin with the lower resistance could lessen insertion loss, and that would ease the load on the amp, so it could work either way. Then there's the scenario if the amp has dual power amps, ala the Ashdown Superfly for instance. Plugging both into a single cab with parallel jacks could fry a 'Fly. I don't know what the LM III configuration is, but the possibility for damage does exist. [quote]after having some numpty at a gig borrow my gear [/quote][i]That's [/i]the source of the problem. If I do let someone sit in I have one rule: don't touch the amp. If they don't like the way it sounds that's their tough luck for not bringing their own gear.

You were standing in a null zone. http://billfitzmaurice.info/forum/viewtopic.php?f=10&t=999 Moving the cab and/or your position can help. Since you can't hear lows when you're in a null zone it's critical to have the cab either elevated or tilted back so you can hear your mids.

[quote name='DIYjapan' timestamp='1495931610' post='3307648'] most people on here are recommending tube ports. [/quote]I didn't. You may find these threads interesting, including the builder's choice of finish: http://billfitzmaurice.info/forum/viewtopic.php?f=30&t=24323 http://billfitzmaurice.info/forum/viewtopic.php?f=13&t=24354

[quote name='Jus Lukin' timestamp='1495819948' post='3306897'] Money- no longer worth it's weight in burgers! [/quote]I'm sure they're no longer like that. The reason: credit and debit cards. Before the barriers went up fast food joints were easy marks, and cash heavy, as that's what everyone paid with. Nowadays cash is a thing of the past. Banks were less likely to be robbed, having armed security guards. You never saw Ronald McDonald packing heat.

[quote name='Jus Lukin' timestamp='1495817800' post='3306874'] I seem to remember drinks and tickets​ were dispensed through a hatch- perhaps the missing part of the rectangle housed the office and storeroom! [/quote]Years ago in some of the seedier sections of New York City, and I'm sure other cities as well, there were bullet proof perspex dividers over the counters at McDonalds and other fast food shops, where the orders were passed through small revolving doors. Banks in the same neighborhoods had less security.

[quote name='Balcro' timestamp='1495818332' post='3306883'] Downloaded that latest version of winISD from the facebook link and the home-page, but Norton Anti-Virus took umbrage with it on both occasions. Something called Heur.AdvML.C was identified and it was removed to the vault. [/quote]It's a Norton issue. See: https://community.norton.com/en/forums/heuradvmlb-detected-false-positive-or-not I have Windows Defender, Super Anti Spyware and Malwarebytes, none have any issue with it.

I see you're using spline braces on the box sides. Spline braces are better than no braces, but barely. Panel to panel braces are far more effective, and allow you to build a cab from 1/2"/12mm plywood for a lightweight cab. I also don't care for slot ports. Corner ports in all four corners work better, and they have the advantage of bracing the top, bottom, sides and baffle. As to the math, no one does math anymore. Download WinISD 0.7: https://www.facebook.com/WinISD/posts/126113234166443

[quote name='Phil Starr' timestamp='1495646885' post='3305611'] It's a cultural thing Bill, a lot of our pubs are in very old buildings [/quote]I know that pubs tend not to be on the dimensions of the Royal Albert, but 10x15 feet? Meters yes, but feet? My car wouldn't fit in a garage of that size.

[quote name='cheddatom' timestamp='1495637460' post='3305511'] There's a pub I've done a few times, the room we play is probably 15ft long, 10 ft wide. [/quote]My living room is larger than that. Maybe I should start charging my guests for their drinks? I can't imagine a room that small being able to pay me enough to leave the house. As for subs, read what I actually posted. Low tend to make their way throughout the room no matter what its size. It's the directional mids and highs that need spreading about.

[quote name='cheddatom' timestamp='1495629316' post='3305411'] I'm talking about very small pubs. I have an extra heavy beater for the kick drum, and I actually have to take it easy on the snare to get the mix right [/quote]I run everything in the PA no matter the size of the room. The difference is akin to listening to a small table radio versus a decent stereo system. Management might not care about how it sounds, the audience might not care about how it sounds, but no matter. I care about how it sounds.

[quote name='cheddatom' timestamp='1495544467' post='3304606'] I play in an originals band that still manages to get the odd pub gig where we take our own PA. For these, the bass never goes in the PA, but neither do any drums [/quote]It's actually important to put drums in the PA, the snare in particular. Even a ham fisted troglodyte's snare doesn't carry all that well throughout most rooms. Having the bass in there as well doesn't hurt, but not for the lows that carry well, for the mids and highs that don't. Just be sure to high pass the channel at 100Hz and/or roll off the bass EQ so it doesn't stress the PA. The same applies to guitar, for the same reason. It's not about volume, it's about dispersion.

[quote name='citymariner' timestamp='1495484753' post='3304164'] [i][size=3][color=#333333][font=Oswald, sans-serif]"The [/font][/color][b]Standard 104HR[/b][color=#333333][font=Oswald, sans-serif].... puts out impressive power at 800 watts[/font][/color][/size][/i] Is MarkBass talking crap? [/quote]Big time crap. For starters, speakers don't put out power.

[quote name='grandad' timestamp='1495185446' post='3301907'] The conflict in my mind is between the larger speaker = narrower beam, smaller speaker = wider beam, which in my experience behave the opposite. Theory states that the larger the source compared to the wavelength the more narrow or directional the beam. What am I missing here? [/quote]It's not theory, it's law. Use this to illustrate: http://www.acoustics.salford.ac.uk/feschools/waves/flash/diffractionslider.swf Dispersion is why tweeters are smaller than midranges, midranges smaller than woofers. [quote]On reading over the above it sounds rather text-bookish[/quote]The behavior of sound waves isn't intuitive, because unlike light waves we can't see the result.

[quote name='CameronJ' timestamp='1495006825' post='3300295'] why is it that I've never seen a 4x10 cab which comes constructed this way? . [/quote]Because it wouldn't sell. People buy what they're used to seeing, and that's a standard 4x10. In any event, a pair of 210s is more practical, from the standpoint of cartage and the ability to leave one at home when you don't need it.