Bill Fitzmaurice

[quote name='pby' timestamp='1383323290' post='2263222'] I think RandomBass was confused about specs from ampeg manual, the units used are confusing. "2 x 900 watts rms @ 2 ohms (600 watts continuous), 3% THD" I don't know how they got the 900 watts rms value but pretty sure it's electrically irrelevant as the real/apparent power of the amp is way less than that. I'm guessing the continuous power IS the average power. [/quote]Looks like specsmanship to me. Traditionally RMS was assumed to mean continous, anything other than continuous was called peak, or music power, or any of a half dozen other marketing euphemisms created for the sole purpose of inflating the actual power output.

[quote name='sebastian' timestamp='1383310250' post='2262948'] Does it mean that when we're talking about the cab of 600 Watts - the amp of 900 Watts is appropriate or the other way around - the amp of around 300 Watts? [/quote]Both of the above and anywhere in between. [quote]As a slight aside, I have never fully understood the term of RMS watts.[/quote]Measure the amp's maximum output RMS voltage swing into the rated load at the rated THD and that's 'RMS' watts. The watts aren't RMS, the voltage swing is.

[quote name='sebastian' timestamp='1383303923' post='2262811'] Taking the example of SVT 4 Pro, which has 350W rms @ 8 ohms on the power amp A and B. Does that mean that I will be able to use it with the Carvin cab and will I only get 350W of power or - is this going to be too much for the cab? [/quote]The cabs power rating is how much it can take before the voice coils melt. In most cases that's well above how much the cab can take before the drivers distort (displacement limited power). Cab companies should tell you what the displacement limited power is, but they won't, since the much lower figure would impact sales. In practice you'll never over-power a cab if you don't push it beyond the point where you hear distortion. That means an amp rated anywhere between one-half and twice the power rating of your cabs is usually appropriate. Less than half probably won't drive your cabs to their displacement limit, more than twice is power you can't make use of anyway.

[quote name='6v6' timestamp='1382629258' post='2254694'] - the component can be attached to the board with tie-wraps or silicone [/quote]As they can, and for that matter should be, with wood. OTOH I've seen many a phenolic board that cracked, and the traces along with it, but I've never seen a wood base crack. Much ado about nothing you are making.

[quote name='6v6' timestamp='1382528950' post='2253198'] Well I never, google says it's true! [/quote]Google is wrong. Bulbs aren't employed in crossovers as fuses, although they will in effect act as fuses if the cab is over powered or fed with very highly distorted signals, which can blow them out. Bulbs are used as simple compressors. As the filament heats with higher power input the resistance of the filament goes up, reducing the voltage delivered to the tweeter. [quote]Same goes for the crossover, which should be constructed on a bit of fiberglass or phenolic board with turrets/tags, not a bit of ply which can absorb moisture and become conductive.[/quote]There is no reason to use fiberglass or phenolic other than that they can be made with conductive traces, which speeds the construction process in high volume operations. Making a board with conductive traces slows the construction process in typical DIY production runs of one or two cabs, even assuming the DIYer has the capability to make traced boards at all. Wood as a material for crossover boards has been used since the first crossovers were constructed circa 1920, with no ill effect.

[quote name='Dev70' timestamp='1382099437' post='2247923'] bought 2 sovereign pro 500s 12" my plan is to run them in 2 separate old but solid H/H cabs [/quote]There are dozens of threads about the dangers of randomly tossing together drivers and enclosures.

[quote name='RPaul' timestamp='1381907708' post='2245120'] apart from taking it to the nearest specialist to take a look at and opening up the wallet, is there anything I could do? [/quote]Even a specialist won't be able to do anything, A poor signal to noise ratio is a common charateristic of an inexpensive design. The cure is a better/more expensive amp.

[quote name='Billy Apple' timestamp='1381150371' post='2234953'] My point is not whether it can or can't be done, my point is that there are differences in opinion. In this case, one from a very knowledgeable chap such as yourself, and another from the manufacturer. For my money, I think the OP should be speaking to Eminence. [/quote]That depends on who at Eminence. For the most part when you email Eminence for advice you deal with a customer service rep, who gives advice based on a drop-down menu that they have of stock answers to what amount to FAQs. These people aren't engineers. They will have a far higher degree of product expertise than a retailer, but they don't make their livings designing either transducers or enclosures. Not that there aren't engineers at Eminence, but said engineers work in the engineering department, not customer service. You will not be put in contact with them, or even know their names, unless you are an industry professional, like myself or Alex. That doesn't mean that one needs the advice of an industry professional. There are certainly many amateurs quite capable of using speaker modeling software able to give definitive advise on how a certain driver will function in a specific cabinet. That advise could include specific details of the need to high pass at a specific frequency and to limit amplifier output to a specific voltage swing to insure that the driver cannot be harmed. You won't get that from Eminence's customer service department. The closest you'll get to that is if you look at their published plans for their drivers, which do come from their engineering department. But even that information can be duplicated by anyone with modeling software, and the knowledge of how to use it.

[quote name='Billy Apple' timestamp='1380979328' post='2233053'] Fair enough Bill, but below is a copy of the email Eminence sent me, and after all, they manufacture them. Anyway, my point is, everyone has an opinion, but for my money I'd listen to the maker. Hi Sean, Yes, you can remove the front gasket pretty easily without harming the speaker. Take a utility knife and cut it off, being careful not to cut any portion of the cone’s surround. Once you get the gasket started, you may be able to pull it off. Best Regards, A****** L**** Technical Support Eminence Speaker, LLC [/quote]I'm well aware that it can be done. My point is that it shouldn't be, there's nothing to be gained, and potentially a driver to be lost.

[quote name='Billy Apple' timestamp='1380976176' post='2233015'] I think the OP should get in touch with Eminence themselves and see what they have to say. I had a question about removing the sealing gasket from the front of an Eminence Basslite driver. The supplier said it should not be done, could cause the cone to come unstuck and void the warranty. Eminence said it could be cut down, or indeed removed completely. They said the adhesive that sticks the gasket on is different to the one that glues the cone to the chassis, and the presence (or not) of the gasket does not interfere with this. [/quote]It should not be done, for two reasons. One is that there's nothing to be gained in so doing, so if it ain't broke don't fix it. Why one would decide to remove it is beyond me. The other is that in the process of removing it one might pull the suspension from the frame, and even the smallest air leak there could lead to driver failure. [quote]I'd seek the advise of the people who built it. BTW took Eminence less than a day to respond, the supplier took a week! [/quote]Suppliers/distibutors employ sales, advertising, customer service and shipping personnel, not transducer engineers.

[quote name='AndyKos' timestamp='1380853245' post='2231590'] recognising the name Bill Fitzmaurice,Im curious are you the same Bill Fitzmaurice thats linked to numerous speaker designs, [/quote]Guilty as charged.

[quote name='Mr. Foxen' timestamp='1380838496' post='2231478'] So that's two counts of Blue Aran staff not having the first clue about bass cabinets then. [/quote]I agree to some extent, though it falls upon the customer to do the proper research to be sure that they are purchasing the correct driver for a particular application, not the retailer. I don't expect a retailer to have a high degree of engineering expertise. Of course, if the retailer does assume the position of giving applications advice, other than merely reposting manufacturer specs and data, then they have the obligation to be sure that they get it right. In short, don't offer expert advise if you're not an expert. Still, I put the onus on the OP in this case. I'd be curious to see exactly what research he did. For instance, did he ask here before making his purchase?

[quote name='skidder652003' timestamp='1380655076' post='2228594'] There are numerous possibilities, including the fact that the speaker simply was not compatible with the cabinet you put it in.[/quote]That sums it up. How did you choose this driver? There's far more to be considered than just inches and watts.

[quote name='alexclaber' timestamp='1380620797' post='2227845'] The driver in question is excellent for bass guitar. The damage is a clear case of both excursion and thermal overpowering. . [/quote]+1. As is the case with any and all drivers it must be loaded into a cab that is compatible with its specs. If one is to push it to maximum output the amp must at the very least be appropriately high passed, if not limited to the driver's safe operating voltage swing. It must have sounded really bad for quite some time to have sustained the damage that it did. Distortion is the driver's way of telling you that you're pushing it too hard. In terms of performance the 3015 is on par with an Aston Martin. One would not expect Aston Martin to honor a warranty replacement claim should one drive it into a grove of trees.

[quote name='Roland Rock' timestamp='1380204281' post='2222279'] I've just discovered something very interesting, considering one of my amps is a Streamliner 900. I was researching Thumpinator on BC, and this came up on the subject of high pass filters: [/quote]Many amps incorporate HP filters, it greatly reduces warranty claims on blown drivers.

[quote name='Roland Rock' timestamp='1380186581' post='2221909'] I have ordered a low pass filter, as two of our songs are in a dub reggae style, and I'd like to get that pure deep deep tone. [/quote]Just turn down the high and mid EQ on your amp. [quote]So the question is, what happens if I boost a frequency below the "usable range"? Will I blow my speakers? [/quote]Quite likely. The 'usable range' takes into consideration not only frequency response but also the driver excursion limit. Boosting below that range may result in over-excursion, causing both thermal and mechanical driver damage.

[quote name='jdt' timestamp='1379880873' post='2217805'] just wanted a 2x10 to go with 2x10 markbass cab, was thinking of a 112 fender cab, [/quote]Whatever you're thinking about don't pull the trigger until you've actually tried the two together, as there's no way to predct the result. The only safe combination to go with without hearing it first is two identical cabs, which will sound the same as one, but louder. Beware the urge to add a different cab to make up for deficienies in your existing cab. If, volume aside, your current cab doesn't sound good, don't try mixed cab voodoo to fix it. Get rid of a cab that you don't fully like and replace it with one that you do.

[quote name='geoffbyrne' timestamp='1379420363' post='2212410'] I'm pretty much going to replace both of these little speakers (they're all fine, by the way) with a single 12", 8 Ohm rated somewhere near 150W-ish. [/quote]Bad idea. You need response to at least 10kHz. Useful response from a twelve is no higher than 2kHz before it beams so badly that you can't hear it more than a few inches off-axis at the range monitors are used at. Unless the drivers are damaged leave them alone. The above assumes you're using them for vocals. If you're intent is to use them for bass, along with a backline amp, that's a bad idea as well. You may be doing so with the intent of hearing yourself better, but if the backline amp and monitors create null zones in the space between them it will have the opposite result.

[quote name='Wolverinebass' timestamp='1379193037' post='2209771'] Surely GB would have been making money? [/quote]Obviously not enough not to accept the Fender offer. As for Fender retiring the GB brand, it wouldn't be the first time a large company has bought out a smaller company just to eliminate them as competitors, with no intention of preserving the brand.

[quote name='goblin' timestamp='1378650524' post='2202767']I know the 1000 watt ones have a fan in them, I'm wondering if there's anything else I can do to aid cooling, including potentially fitting a fan inside of one. I don't want to rack it and have a fan in a rack case, as that would then defeat the point as it'll be no more compact than the Hartke! [/quote]Racking it is the only practical method of fan cooling it. It does work, though.

[quote name='wateroftyne' timestamp='1378459557' post='2200513'] I'm quite happy to state that (so far) Neos don't seem to ring my bell, without being too bothered by the 'You don't understand the theory - they're no different other than the weight!; responses I invariably receive. :-) [/quote]They are different. Neo allows longer excursion, not because of higher flux, but because the motor structure is more compact. Longer excursion results in higher output with less distortion. Most of us prefer that to lower output with higher distortion, but I guess not all.

[quote name='Corvine' timestamp='1378157229' post='2196519'] Will I get more volume from one cab than another? Can this harm the amp/cabs, or just that it might not sound so good? [/quote]All of the above. The only totally safe and totally predictable combination is identical cabs.

[quote name='Corvine' timestamp='1378155219' post='2196477'] On an amp that goes to a minimum of 2 ohms, and has 2 speaker out-puts, it's ok to have a 4 ohm cab on one out-put and two 8 ohm cabs (in parallel) on the other out-put. [/quote]It's OK, but chances are slim to none that the cabs will have equal power distribution.

Impossible to say, but the small AlNico magnets reveal them as generic musical instrument drivers, so I would not consider them for bass.

[quote name='hamfist' timestamp='1377252793' post='2185276'] Maybe, for passive basses, the higher the impedance output of the pickup, the more they lose signal, and tone, with longer cables? It's a theory anyway . [/quote]It's a fact. When the impedance of any source is particularly high it makes the capacitance of the cable a major factor in high frequency losses and noise pickup. The higher the impedance the worse it is. The cures are lower source impedance and/or lower capacitance cables. Since capacitance is proportional to cable length that also enters the equation. Capacitance and cable length tend to be non-issues with line level/buffered sources, such as those in actives, where the source impedance tends to be less than 1kOhm, as opposed to 10kOhm and higher with passives. [quote]I chucked it away it was so bad. Is this an issue with curly leads [/quote]Coiled cords have the worst capacitance imaginable, and also high inductance, which makes them doubly bad.