Bill Fitzmaurice

[quote name='Ruds' timestamp='1415631525' post='2602139']. Maybe I'm just overthinking, and in practice this is not important, or I'm overlooking something. [/quote]It's not that xmax isn't important, it's that you don't have to consider it along with the thermal power rating, frequency response and sensitivity in a juggling four specs scenario when the maximum SPL chart wraps it all up in one neat package. It also helps to know that you don't need for a cab to have consistent maximum SPL down to the lowest fundamental. Where you run into a compromise situation with respect to a design that anyone can use is not knowing if the end user has a four string, five string or a drop tuned six string.

Any of my 2x12 designs would suffice. They're made from 12mm plywood, so they're light weight. They've also withstood falling off the back of a pickup truck at 60MPH with only scraped paint to show for it. I'd venture that barefaced are just as durable. What you make a cab out of is of far less importance than how you make it.

[quote name='owen' timestamp='1415563197' post='2601516'] One speaker firing out of the front and one out of the back (presuming out of phase with the front one)[/quote]That would result in their cancelling each other. They would have to be in phase/polarity. For best results the rear driver would have to be low-passed, probably around 250Hz, where the rear radiation pattern is omni-directional. Some will suggest that having the rear driver full range would give good dispersion, but the result would be severe comb-filtering, with the cab sounding different at every possible combination of both the cab placement and the listener position, as the front and the reflected rear waves meet at constantly shifting degrees of phase based on the wall distance and listening position.

[quote name='Ruds' timestamp='1415547203' post='2601329'] But, if I know the cab is going to be used mostly for electric bass, and I know something about this signal, wouldn't it be more precise to use this information to estimate the limits of the enclosure on a more practical situation? [/quote]I don't. I look at SPL, Maximum SPL and port velocity charts. I don't worry about excursion per se, as it's just a means to the end that's seen in the Maximum SPL chart. Looking at the excursion chart shows only one dimension of a three dimensional result. The main benefit to looking at the excursion chart is in learning how it fits into the overall result, including how tuning affects excursion, but after a few decades of designing speakers that's second nature.

It's the maximum SPL chart you should be looking at, not the excursion chart. Maximum SPL accounts for sensitivity, excursion and thermal power. With a 5 string tuned at B your maximum demands lie at the 2nd harmonic, 62Hz. However, obtaining maximum SPL at 62Hz will come at the cost of sensitivity, and therefor output, below that, so you must compromise to get the best overall result. In 56L 55Hz tuning gives maximum SPL of 121dB at 62Hz, but only 104dB at 40Hz. 48Hz tuning still gives 118dB at 62Hz but with a much more useful 110dB at 40Hz.

[quote name='yorks5stringer' timestamp='1415011014' post='2595501'] How do you get on with the right hand drive and UK registration plates in New Hampshire..... ? [/quote]That's my spare that I keep garaged in St.Andrews, for when I visit to play a few rounds.

[quote name='88reaper88' timestamp='1414358999' post='2588655'] I'd rather have the van [/quote]So would I, when I was 23 and on the road. But to paraphrase an old movie scene, "BMW. It's a little too small to get laid in. But you get laid the minute you get out". And we all know from sad experience it's not the bassplayers who get the women, it's the drummers.

[quote name='88reaper88' timestamp='1414348980' post='2588526'] ...not gain a masters degree in acoustics. [/quote]If you do you'll have something to fall back on when your playing days wind down. When I played bass five nights a week this is what I drove from gig to gig: I don't gig much anymore, but I play golf seven days a week, and this is what I drive to and from the course:

[quote name='Chienmortbb' timestamp='1414325852' post='2588211'] I was really excited when I first looked at the SM110. I have just done a quick winisd plot of the SM110. It has a great frequency response in a 40L box but xmax is exceeded in the at very low power (approx 75 watts) . This means that it is 3-6dB down at 70Hz. I will recheck later but at the moment the Fane 10-300 looks. a better bet [/quote]Good call. One cannot look at a sensitvity plot alone. Below are shown the Celestion (red) compared to the Eminence 3010LF (green), both in 45L. If all you look at is the top sensitivity trace then there would seem no real advantage to be had with the 3010LF. Looking at the middle maximum power and lower maximum SPL traces reveals a very different story: While you're at it model the Eminence BP102. [quote]If only I could make two cabs and test them out![/quote]Theile and Small rendered that necessity obsolete circa 1970.

They would not be my first choice. The 73Hz Fs is too high. Assuming that you don't know what that means, required reading: http://www.eminence.com/support/understanding-loudspeaker-data/

[quote name='Kevin Dean' timestamp='1413982999' post='2584377'] Everything was fine until the drummer who is also the singer decided he liked having the Sub behind him & I must admit the bass drum does sound good compared to what was coming through the monitors . [/quote]That's all well and good, but what does it sound like where it counts, in the audience? Having subs (and you need more than one unless the room is tiny) on stage is not the best placement where driving the room is concerned.

[quote name='lefrash' timestamp='1413967770' post='2584056'] Has this gaping hole totally knocked the balance off the sound of the cabinet? [/quote]It has. Cover it.

[quote name='xgsjx' timestamp='1413972882' post='2584156'] The difference between 4 ohm & 8 ohm cabs (if they're the same, such as 2 MarkBass 2x10s), is @ 3 decibels. [/quote]The difference is 3dB higher sensitivity for the 4 ohm cab with the same voltage input. The difference in maximum output is zero, because that's limited by the driver excursion, which is the same.

[quote name='Kevin Dean' timestamp='1413933262' post='2583909'] the only thing is I'm not getting all of that power out of my Abm 400RH [/quote]Going to a 4 ohm cab probably won't make any difference. Speaker output is limited by the driver excursion capacity, and that's not affected by impedance. Very few tens will take much more than 100w before they reach maximum excursion. The SICA drivers in your cab, for instance, max out in excursion at 100w each in the low end, so a larger amp won't make any difference either. Bottom line, you can only get so much out of a 2x10.

[quote name='chris_b' timestamp='1413801390' post='2581961'] The boom you hear might be localised to your corner of the stage and won't be heard out front. The problem with EQing out of it is that by the time you get a sound on stage you'll have changed the sound out front to the point that it might not be what you want. [/quote]True, but seldom if ever is the tone you hear on stage the same as what's heard out front. Ideally out front is covered by the PA, controlled by a competent sound guy who knows what you're supposed to sound like. If you're not in the PA then you adjust your EQ during soundcheck using wireless or a long cord to stand out front, and live with whatever it sounds like on stage. [quote]Ports are omni directional though & unless the ports on the cab is less than a few inches from the wall, I believe they have no affect on sound regardless of where they are on the cab.[/quote]Correct. [quote]My (inexpert) opinion would be that the problem is to do with reflections coming off both wall and floor as having speakers positioned in corners is known to cause problems with bass frequencies. Maybe raising the cab up some may help.[/quote]Also correct. Lifting the cab by a meter or so can reduce midbass boom, while making it easier to hear the mids and highs, which will mask a midbass boom.

[quote name='leroydiamond' timestamp='1413717615' post='2581090'][color=#141414][font=verdana, geneva, lucida,] Previous experience of doing this with a rear ported cab, resulted is excessive boom that could not be controlled with EQ.[/font][/color] [/quote]Boom is easily controlled with a parametric EQ. Set the Q to medium width, set the gain to -10dB, sweep the frequency until the boom disappears. Then tweak the Q and gain to taste.

[quote name='Kevin Dean' timestamp='1413452470' post='2578313'] Some time I just cant hear any note definition on a tight stage but it sounds great about 8 ft away [/quote]That's due to the small midrange dispersion angle. While it's not as much an issue with bass as with guitar, it's still necessary for your ears to be within the cone shaped midrange dispersion pattern of your speakers. If you're standing close to your rig that means tilting it back, unless it's an 8x10 or a stacked arrangement that stands at least four feet high. OTOH, unless your cab is aimed at the drummer, how does he hear your mids? He doesn't. Monitors aren't just for vocals, they're for whatever needs to be heard.

[quote name='itsmedunc' timestamp='1413365722' post='2577464'] I have to stand as far right as possible to him as he is far too loud for me. [/quote]He wouldn't be if the cab was aimed at his head. But a surprising percentage of guitar players have serious issues with basic anatomy, as they seem to think that their ears are mounted on their calves.

[quote name='itsmedunc' timestamp='1413323937' post='2577259'] I'm surprised your guitarist needs to go through the PA never mind the monitors as well! [/quote]Guitar more than any other electric instrument needs to be in both the PA and monitors, as its high frequency dispersion pattern is abysmal. The problem with most guitar players is that they play so loud that the small percentage of the audience that is within the dispersion pattern of their speakers end up with bleeding ears, while the rest, including a bass player standing only ten feet from the guitar amp but off to one side, can't hear them at all. The smart guitar player knows enough to use no more than a 1x12 speaker, so he can crank it for tone without excessive volume, letting the PA spread his sound across the room and the monitors across the stage.

[quote name='icastle' timestamp='1413324408' post='2577265'] Electronic theory says this is OK, but in practice you can't just wallop any old speaker into a wooden box and expect it to work to it's optimum. [/quote]+1. And while the Delta 12 has a 350w rating, that's thermal, which only says what it will take before the voice coil burns out. What matters in terms of output capability is xmax. At only 2.4mm it will only take 50 watts in the critical 60Hz-150Hz range before serious distortion occurs. Don't buy the cab.

[quote name='Tuono' timestamp='1413228780' post='2576176'] I know nowt much about PA. Our guitarist/singer does (?) [/quote]Not as much as he thinks he does. [quote] I got a bit in the monitors as well and that was when he threw a wobbler and said about ten times that you NEVER put bass through the monitors.....is he right?[/quote]No, and yes. You should be in the monitors so that everyone else can hear you. So should all the instruments, save the drums (who has trouble hearing them?). But what should be in the monitors is your mids and highs, which travel from your cab in a straight line. Your lows radiate in a circular pattern, so they don't need any assist from the monitors, and in fact running the lows though the monitors can cause their low frequency output and that from your cab to cancel each other. A good soundman knows this, and he'll high-pass the bass in the monitors to keep the lows out of them.

[quote name='police squad' timestamp='1413122700' post='2575067'] can't work out how to take them apart. genuine neutrik though [/quote]http://www.neutrik.com/en/instructions

Turning the volume control down loads the pickups, causing a loss of high frequencies, which to some might sound better.

[quote name='LukeFRC' timestamp='1412836740' post='2572453'] I was in America last month, was mental, the FM radio on the hire car needed retuning every 5 miles. At one point We were driving through Shenandoah on the skyline drive and on the Richmond Side we got some rock station and the moment the road turned to the Shenandoah Valley side of the hill it was some christian praise station.... mental [/quote]That's because FM is a line of sight transmission medium. So is satellite for that matter, but whereas with FM line of sight could be as little as ten miles to a two hundred foot tall tower, with satellite it's to a point some 42,000km high in the sky. [quote]They are supposed to be very efficient, very loud per watt. You get a few extra db [/quote] Feld coil drivers have no higher sensitivity than PM drivers. Sensitivity is determined by T/S specs, not the magnet composition.

[quote name='Dad3353' timestamp='1412798455' post='2572249'] One needs long-wave AM to pick up the BBC here in France. Old technologies have their 'niche' advantages (sometimes...). Just sayin'. [/quote]I can get anything anywhere in North America with satellite radio. Just sayin'.