Bill Fitzmaurice

[quote name='Phil Starr' post='1303710' date='Jul 14 2011, 11:29 AM']There are loads of signal generators online and if you are deeply boring (like me)it is quite interesting to listen to a 40Hz (roughly bottom E) pure tone and realise just how low that is. If your speakers can go that low of course.[/quote]You may still be hearing a lot of harmonics, as your speakers create them. If you play a pristine 40 Hz or lower sine wave through a capable speaker with very low THD you can't even discern pitch.

[quote name='tim126' post='1303547' date='Jul 14 2011, 09:12 AM']Now I have heard about harmonic frequencies and stuff (not sure I understood it, mind you!)... but, putting it in really dumb terms, if the bottom B is producing a frequency below the rated/stated capabilities of the amp and the cab, how come I can still hear it when I play it?... .[/quote]Because you're mainly hearing said harmonics. They dominate the output below roughly 80Hz. You perceive the fundamental being louder than it is as the second harmonic is the same note an octave up. And what you perceive as 'deep bass' is typically an octave higher than you think it is.

[quote name='Balcro' post='1295388' date='Jul 6 2011, 06:13 PM']Further to your post No. #14 above:- Wooks79 has a SS power amp section to his SVT3 Pro and its operated into a vented cabinet, which displays that typical double peak impedance (red-line) plot. Therefore from your explanation, can it be assumed that amp will be reasonably comfortable under such conditions? Balcro.[/quote]SS is generally fine with all vented cabs, not so much with sealed cabs when run at the amp minimum load rating. The opposite is true of tubes. They'll run into a dead short without complaint, but aren't happy with some vented cabs, especially those with very low Q drivers, which have very high peak impedance values. Now defunct Basson is an example, well known for bragging on their very low Q drivers with 20 pound magnets, almost as well known for their cabs toasting output transformers as a result of same.

[quote name='Balcro' post='1294629' date='Jul 6 2011, 07:29 AM']Reading between the lines, I think Bill is cautiously referring to the potential for damage that may occur to the amplifier if your amp is not capable of operating into a 4 Ohm load.[/quote]Not quite. Load figures are only vast generalizations, based on the DCR of the drivers used. Even with the same nominal load rating different cabs have very different loads, even when using the same drivers, as shown here: This shows the same driver in a sealed and vented cab. A tube amp will be much happier with the lower average impedance load of the sealed cab, SS will be happier with the higher average impedance load of the vented cab. The inverse is also the case, and is likely the source of Ampeg's problem with its Micro VR SS head and sealed 2x10 cabs.

With low power you want a hgher Q driver that delivers a humped midbass response, for adequate output. With high power you want adequate xmax to handle it, whereas with low power high xmax is unwarranted. And then there's the matter of impedance, being sure that it's appropriate for the amp. That's far more complicated than it seems on the surface; Ampeg is having some major problems with their mini-stack, as the load offered by a pair of the 2x10s is fundamentally at odds with the needs of the amp.

Still need your amp specifics, as which you'll use makes a big difference.

[quote name='Blademan_98' post='1291260' date='Jul 3 2011, 01:16 PM']He must be a drummer though as he wore no gloves or mask [/quote] More likely a bass player, we're used to being ignored. Not a guitar'd player, though, or he'd have smiled for the camera.

[quote name='jonno1981' post='1291004' date='Jul 3 2011, 09:10 AM']This is a re-post from a friend of mine who had a break in at his rehearsal studios last night. Watch out for any secondhand Mag300 heads going cheap around berkshire......If anyone recognises the guy please send Jay a message.[/quote] He'd get a better result posting the actual video feed, rather than a video of a video. I assume the police have used the video to get a still photo of the w***er for a 'Wanted, Dead or Alive' poster. And the way these things work chances are better than even he's a client of your friend, not a very bright one judging by the apparent lack of gloves.

Technically any Gamma 12s are NOS, new old stock. Production of them ceased a number of years ago.

[quote name='muttley' post='1286649' date='Jun 29 2011, 11:57 AM']Yes, I knew about the dominance of neo in PA. It's not [i]that[/i] long that I've been out of the industry . But for MI, do you mean non-guitar applications?[/quote]Guitar is the one area where neo has not yet made major inroads, because most guitar drivers don't use very large magnets nor have high xmax values.

The Ampeg driver has 4.7mm xmax, the 2510 4.2mm. That gives them virtually identical output capability.

[quote name='muttley' post='1286462' date='Jun 29 2011, 09:26 AM']I've been out of the game for a few years now so don't know what the latest thought is on neo[/quote] More than a few I'd say. Neo has owned the high end PA genre ($5k and up per cab) for a decade, musical instruments for the last five years. But as of recently the price has skyrocketed due to predatory trade practices by the Chinese. And Eminence didn't get to be the #1 driver manufacturer in the world by producing crap.

[quote name='Neuroscar' post='1286020' date='Jun 29 2011, 02:25 AM']Im thinking about making my own 15" cab[/quote]Only do so if all of this makes perfect sense and you know how to make use of it: [url="http://www.eminence.com/support/understanding-loudspeaker-data/"]http://www.eminence.com/support/understand...udspeaker-data/[/url] [url="http://www.linearteam.dk/default.aspx?pageid=winisd"]http://www.linearteam.dk/default.aspx?pageid=winisd[/url]

[quote name='Lozz196' post='1285850' date='Jun 28 2011, 05:51 PM']Ok, been doing a bit of reading over on T*lkb*ss, and there seems to be a fair appreciation for Eminence Basslite S2010s. I`ve also found out from Eden that the speakers in my cab are their Chinese made cones. So, would the Basslites be an improvement, and offer me a tone nearer to that of an Ampeg than what I have now?[/quote] Impossible to say without either seeing response charts for both (Eden does not publish any, as it would reveal their SPL claims to be rubbish) or having cabs with both drivers side by side.

[quote name='Merton' post='1284755' date='Jun 27 2011, 05:49 PM']Sorry for going OT here but when did Eden stop making their own drivers? Was it around the time of the US Music takover or when David left?[/quote]Eden's a bit cryptic, so I can't say for sure if they're still making any ceramic drivers or have gone completely to Eminence, but their staple driver was the 1060, and they now use the 1040 in Nemesis, probably Eminence. Their Neo is Eminence. The Ampeg drivers aren't all that heavy, 6.7 pounds, so four of them are only eight pounds heavier than four neo tens. Any other weight difference would be in the cab.

[quote name='Lozz196' post='1284593' date='Jun 27 2011, 03:44 PM']I`m thinking of changing the speaker cones in my Eden Nemesis 410, to either Eminence BP102 or B102 cones, to try and get a more Ampeggy sound, figuring that as Ampeg use Eminence speakers, that is logical[/quote] The cab and driver must be matched to work well. With older Edens when they made their own drivers you really needed to use Eden replacements. They now use Eminence, so there's probably nothing to be gained by swapping them. As far as what Ampeg uses, they bear no resemblance to either the BP102 or B102. The B810 is a direct replacement, but if you don't have a sealed cab you won't get Ampeg tone. And the cab is only half the equation. It takes an Ampeg head as well.

[quote name='Al Heeley' post='1281084' date='Jun 24 2011, 09:58 AM']I'm not sure I fully understand this, Bill. Are you saying that a 1 x 15 in series with a 2 x 10 (proposed setup) is different to having a 4 x 10 in parallel to a 1 x 15 (current setup)?[/quote] I'm saying forget about the 210, use the 115/410 as you have been, aiming the 115 at the drummer, and never split bass cabs.

[quote name='chris_b' post='1280435' date='Jun 23 2011, 08:57 PM']When I played a 210 and 115 Basschat told me that using different speaker sizes gave me problems, but it didn't! Now I'm being told I have a problem because I stack my cabs the wrong way. I don't![/quote] What you've actually been told is that there are logical alternatives to the willy-nilly tossing together of different speaker/driver combinations and equally willy-nilly tossing of cabs onto the stage with no regard to how soundwaves actually function. It's your option to ignore those alternatives, just as it's the option of others to investigate them and employ them should they find it appropriate for them.

[quote name='Mr. Foxen' post='1280965' date='Jun 24 2011, 08:35 AM']That is much less expensive than I was anticipating.[/quote] Very reasonable, and invaluable as you can use it to measure not only the raw driver but also the finished cab. It will do an impedance sweep in two seconds.

[quote name='Mikefwlr' post='1280931' date='Jun 24 2011, 08:13 AM']EA seem quite secretive about the specs for their cusdtom drivers. Guess i could measure the impedance with a multimeter (but i don't have one), anyone know the specs of these woofers?[/quote] This is what you need to measure specs: [url="http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-804"]http://www.parts-express.com/pe/showdetl.c...tnumber=390-804[/url] I seriously doubt that the EA driver is at all dissimilar to an off the shelf Eminence, but they won't say, and until someone goes to the trouble of measuring the drivers themselves it will remain a mystery.

[quote name='Al Heeley' post='1280547' date='Jun 24 2011, 04:24 AM']Just bought a 250W Hartke VX 2x10... to position just behind the head of our drummer to help him keep time.[/quote]Bad idea. Splitting low frequency cabs will result in all sorts of phase sourced cancellations. What you should do is simply turn the 1x15 (which I assume is below the 4x10) to face the drummer. That will provide him with the mids he needs to hear, while keeping all the lows sourced from the same point. By the same token should you ever run the bass into the monitors it should be high-passed on the board at 100 Hz, providing the mids to the band to hear you while not causing phase cancellations in the lows. If you must have the 210 near the drummer it should be driven by a separate amp with the lows rolled off for the same reason.

[quote name='Monckyman' post='1279540' date='Jun 23 2011, 07:27 AM'] That`s me told! I might remind you though, that this is supposed to be fun, otherwise we`d all be accountants.[/quote] Knowing what you're doing doesn't make designing and building speakers any less fun. It does save more than a fair share of time and trees.

[quote name='Grand Wazoo' post='1278990' date='Jun 22 2011, 03:18 PM']a rear ported cab behaves differently if placed on the floor that it would if stacked high.[/quote]The direction the port faces makes no difference. Any perceived tonal difference is purely the result of hearing your mids and highs better. [quote]Spacing the speakers further apart lowers the maximum frequency at which they will couple coherently[/quote]Only on the vertical plane, which doesn't affect what the audience hears, and only affects what you hear if you're very close to the cab, as in less than six feet or so.

[quote name='Monckyman' post='1277822' date='Jun 21 2011, 05:11 PM']Martin, I`m with you. You learn about this stuff by sawing wood, not entering numbers into software.[/quote][i]Any sufficiently advanced technology is indistinguishable from magic.[/i] There's nothing the least bit magical about loudspeaker design, and all you need to learn how to design them is the ability to read and desire to advance your knowledge. Learning how to do this 'stuff' by sawing wood is how it was done when better means did not exist; that era ended with Thiele and Small circa 1965. The only thing that software has done is to remove the need to wade through mountains of equations. If your personal preference is to remain technologically in the dark that's your prerogative. Advising others that they should do so as well, not so much.

[quote name='Phil Starr' post='1275551' date='Jun 20 2011, 03:52 AM']All this meant that most speakers were in boxes that were often too small and that the designs were often under damped meaning that you got a nice warm bass frequency hump at the expense of deep bass.[/quote]True for the most part, because most drivers of that period out of the Jensen/Celestion mold had high Q values. That made them best suited to large sealed cabs. However, JBLs were at the opposite end of the scale, with very low Q values. That made them best when used in small vented cabs. Yet you would find both JBLs and Jensens/Celestions used[i] in the same cabs[/i]. Fender used the D130F and D140F in a large volume per driver vented Showman cab and a small volume per driver sealed Dual Showman cab. Why? Because they didn't know any better. What science that did exist in the field of loudspeaker cabinet design in that era was very much restricted to the theatrical and hi-fidelity genres, being totally unknown in the musical instrument industry. That's why searching out a cab of that period, or a design for same, is of highly dubious value.