Bill Fitzmaurice

[quote name='alexclaber' post='1345333' date='Aug 19 2011, 07:22 AM']And there's inductance to think about too![/quote]There are some who believe that inductance is the primary concern. [url="http://www.stereointegrity.com/docs/WooferSpeed.pdf"]http://www.stereointegrity.com/docs/WooferSpeed.pdf[/url] And since the ten, twelve and fifteen inch versions of the same driver have similar inductance, no surprise as they usually share the same voice coil, it renders the varying Mms figures rather moot.

[quote name='ironderby' post='1344860' date='Aug 18 2011, 03:59 PM']I heard from someone that you can't mix a 2x10 and 1x15 cab because its dangerous or could ruin your amp. Is this true? because i want to add a 1x15 for a little punch, thanks.[/quote] So long as there are no impedance issues there's no reason you can't, but the results are completely unpredictable. With matched cabs the results are totally predictable, it's what you have but more of it. OTOH if you don't like what you have the best route is to find a cab you do like for tone, and use as many as required for adequate output. BTW, fifteens don't inherently have any more punch than tens or twelves, so adding a fifteen to get more punch is operating under a mistaken assumption.

[quote name='Marvin' post='1343962' date='Aug 18 2011, 02:59 AM']I was just wondering what potential benefits and disadvantages there were to using a 4ohm cab.[/quote] To using it? Only a very modest increase in output, if any, while making it impossible to run a second cab if your amp doesn't have 2 ohm capability. The exception is a valve amp that has no 8 ohm tap. To offering it? So you won't lose a sale to someone who 'needs to get all the watts out of my amp', even though doing so is of little to no value.

[quote name='gafbass02' post='1343561' date='Aug 17 2011, 02:20 PM']I'm thinking of at backline only gigs having a bass cab and a guitar on either side of the stage for maximum and even spread, silly idea?[/quote] With guitar it would be OK, with bass you end up with cancellation effects that can result in less output and dispersion, not more. This explains why. What applies to PA subs also applies to bass cabs. [url="http://www.prosoundweb.com/article/in_search_of_the_power_alley/"]http://www.prosoundweb.com/article/in_sear...he_power_alley/[/url]

[quote name='Mr. Foxen' post='1343791' date='Aug 17 2011, 05:45 PM']Speaker efficiency and voicing.[/quote]Mainly the voicing, I'd suspect. Most combos have high Q drivers in cabs that are technically too small, which results in no true deep lows but an exaggerated humped midbass response. That makes them sound louder than cabs with lower/flatter response. The difference in what a 300w amp and 150w amp can produce is at best only 3dB, the midbass hump of a combo can be 6dB, easily making up for the power difference and more.

[quote name='flyfisher' post='1343497' date='Aug 17 2011, 01:40 PM']Because the bass and guitar frequencies are well separated in the mix[/quote]The problem is that they aren't. And if you're getting all the mids from a guitar cab at ear level you can't hear any of the mids from your cab down below waist level. The technical explanation is called Precedence Effect. It's tough enough to hear your mids with the cab down low and not tilted back, it's impossible with the mids from the guitar masking them.

[quote name='ben604' post='1343092' date='Aug 17 2011, 08:43 AM']Is this a silly idea?[/quote]Not if he's sitting atop your shoulders. Otherwise, no, because with his cab in your ears you won't be able to hear yourself. The ears his cab should be aimed at are his.

[quote name='icastle' post='1341010' date='Aug 15 2011, 02:08 PM']Either will do the job with no difference. I tend not to daisy chain because if the first lead should fail you won't get a signal to either cab.[/quote] Another advantage is that you don't send all the amp current through only one cord. If your cords aren't under-gauge it's no matter, but if you don't know then using both amp outputs is prudent.

Chris Squire does, has since 1968.

[quote name='ficelles' post='1329480' date='Aug 5 2011, 08:27 PM']Makes me wonder why neos have become popular for bass but notably less so for guitar?[/quote]Because bass players tend to be more learned about how their gear works and are less mired in antique technology. If guitar'd players used the same standards for buying cars as they do their kit most would be driving Morris Minors.

[quote name='Grant' post='1329357' date='Aug 5 2011, 05:51 PM']2 x 10 vs 4 x 10 is a big difference[/quote]The equivalent of reducing your power by 75%, to be exact. Going from a 4x10 to a 2x10 reduces both sensitivity and displacement, the two factors that you can't sacrifice if you need high output.

[quote name='Grant' post='1329099' date='Aug 5 2011, 01:58 PM']I have to wind the volume knob round to 3 o'clock to get it to "gigging" level, with the gain at 12 o'clock. I am confused.... [/quote]Google [i]gain structure[/i]. As for how loud it's capable of going, that's determined by the displacement limit, frequency response and sensitivity of the drivers, not the amp power rating.

[quote name='AsterL' post='1324593' date='Aug 2 2011, 12:46 PM']Any suggestions?[/quote]Don't bother. That 300w/4 ohm amp will actually deliver about 200w into 8 ohms, and it's highly doubtful your 2x10 can make use of even 150w before the drivers reach their excursion limits. Not loud enough? Add another identical cab.

[quote name='LawrenceH' post='1324723' date='Aug 2 2011, 02:27 PM']historically it is a subject that has been dominated by engineers and physical scientists.[/quote] True, but when those engineers and scientists were those employed at Bell Labs they knew far more about how human hearing functioned than the medical community, who were late comers to the party. The history of Bell Labs, and what they accomplished from 1876 to roughly 1950, is a fascinating topic in and of itself.

[quote name='LawrenceH' post='1323765' date='Aug 1 2011, 08:19 PM']It does take a bit of time for that type of biological research to filter out and cross specialisms to the engineering/physics arena, and much longer before it becomes 'common' knowledge.[/quote]Indeed. If you want to see some screwy ideas check out the home theater sites, where some truly believe that there's benefit to speakers that run to 5Hz. That's where biology comes in. Below roughly 12Hz human beings lack the ability to hear anything, because 75 foot long wavelengths pass through muscle and bone with impunity. That fact, combined with the period of the wave, means that both sides of the tympanic membrane are exposed to the same pressure and phase. It does not vibrate, so no sound is heard, and as those wavelengths pass though the body they aren't felt either. What is heard and felt from systems capable of high output below 12Hz is harmonic content and air pressure fluctuation. But it would be incorrect to assume that this is knowledge restricted to the medical community. Acoustical engineering isn't limited to loudspeakers and acoustics. One of the major sub-fields is the hearing aid industry, where knowledge of how hearing works is paramount.

[quote name='LawrenceH' post='1323079' date='Aug 1 2011, 08:52 AM']But apparently a so-called acoustic engineer knows better than my scientific colleagues at the cutting edge of hearing research, how the ears and brain work.[/quote] An acoustical engineer must know how the ears and brain work. If he does not he isn't an acoustical engineer, he's a mechanic. If you've got nothing better to do than argue about the audibility of group delay got to DIYaudio and waste a few dozen pages in debate with Earl Geddes.

[quote name='alexclaber' post='1322743' date='Aug 1 2011, 03:13 AM']And why would you want that to happen? Just curious about the thinking - I think I might write an article about ports soon...[/quote] He's not really off track. When I opened up my first bass cab in '66 the thought occurred that there was compression inside that was restricting the movement of the cones and that they might move more freely if I cut a hole in the cab. What I knew about how speakers worked at that point was precisely nothing, but as it turned out my hypothesis was correct, all that I lacked was the knowledge of how to properly carry it out. I did cut a hole in the baffle, and it seemed to work a bit better. I know it didn't work any worse.

[quote name='LawrenceH' post='1322704' date='Jul 31 2011, 08:41 PM']Bill, you seem a bit fond of putting words into other people's mouths and then gleefully contradicting them as a self-appointed "engineers' representative". I said absolutely nothing about 10ms. To take an extreme case, clearly a group delay of, say, half a second, is extremely audible well below 100Hz. But the exact cut-off is reported differently in different studies - that is the area of controversy. From a neuroscientific perspective it would be very surprising if there wasn't a degree of individual variation in the threshold.[/quote] If you somehow managed to obtain an electric bass cab with 50ms of group delay, let alone 500ms, the speaker would have to be so completely AFU that the group delay would be the least of its problems. As to being an 'engineers representative', it's what I do for a living. Deal with it.

[quote name='LawrenceH' post='1322000' date='Jul 31 2011, 05:51 AM']The threshold of audibility of group delay (frequency-dependent delay) is a bit of a controversial topic.[/quote]Not within the community of acoustical engineers, who are well aware that group delay below 100 Hz is moot. It does bother the heck out of those who see a group delay of, say, 10ms at 50 Hz on a chart, but it doesn't bother those who know that you can't hear 10ms at 50 Hz.

[quote name='DirkThrust' post='1321296' date='Jul 30 2011, 08:45 AM']Ashdown quote an extra 23Hz of lowend for the MAG115 below the 4x10[/quote]Quoting it is one thing, backing the quote up with objective data is something else entirely. They don't. Not that Ashdown is alone on that point, as no manufacturers do so. In any event 'there's no such thing as a free lunch' remains the operative caveat. If the 115 does go 23Hz lower than the 410 that extension is obtained at the cost of sensitivity, so it would take two to four of those 115s to match the output of one 410. One of the laws of acoustical engineering is that power demand doubles for each octave of lower frequency extension. That being the case the notion that a single fifteen driven with the same power as four tens can significantly add to the low end just doesn't add up.

[quote name='sorrow' post='1321027' date='Jul 29 2011, 09:33 PM']has anyone tried tecnical pro power amps or seismic audio bass cabs?[/quote] Both brands should be avoided.

[quote name='DirkThrust' post='1320906' date='Jul 29 2011, 05:27 PM']I've found that a 4x10 produces more thump, thud, thunk, whump or whatever other unscientific name you call the sound bass players like than a 1x15.[/quote]It's only logical, as the average 410 has more total driver displacement, higher sensitivity and for that matter very often the same tuning frequency as the average 115. [quote]that extra 10 or so Hz of bass extension manufacturers quote[/quote]More often than not it's a rubbish figure anyway.

[quote name='fatback' post='1320641' date='Jul 29 2011, 11:53 AM']there should be a competition for the greatest number of acronyms (or whatever they are) in a BC thread. Vd, Vb, Fb, EBP, QTC ????[/quote] [url="http://www.eminence.com/support/understanding-loudspeaker-data/"]http://www.eminence.com/support/understand...udspeaker-data/[/url] [quote]For front porting don't you get that to some degree anyway? The backwave is inverted but one wave out at the resonant frequency...[/quote]The port radiation is only out of phase below the tuning frequency, and in a properly designed cab it's moot as that lies primarily below the speaker operating bandwidth.

[quote name='ficelles' post='1320497' date='Jul 29 2011, 09:46 AM']Untuned ports i.e. just a hole... anyone in favour / not in favour? Any rule of thumb for size? ficelles[/quote] All ports result in a tuning frequency (Fb), which can be determined with any speaker modeling software. The duct length is the thickness of the panel.

[quote name='xgsjx' post='1320350' date='Jul 29 2011, 07:42 AM']Ahh, but what if you set the EQ to a sad face? Would you get the mids back or would you just have a sad face???[/quote]You'd get some of the mids back, yes.