Bill Fitzmaurice

[quote name='ray_6ao7' post='546626' date='Jul 21 2009, 10:54 AM']Hey Alex one speaker's blown recently so i need to replace that anyway and i've been toying around with the idea of trying to get something that has a really nice clear,punchy but deep tone aswell...just thinking it'll probably be cheaper than buying a new cab [/quote] Changing drivers might be of benefit if the new ones are better than the originals, but that requires knowing what the specs on the originals are. FWIW IMO the BL10-200x is poorly suited for electric bass, the BN10-300S totally unsuitable. Neither is capable of delivering deep tone.

[quote name='Protium' post='540590' date='Jul 14 2009, 01:47 PM']Bit harsh. I suppose all your cabs were perfect first time?[/quote] Of course not. But before building my first cab I spent a month in my college library researching how speakers work, and the first few cabs I built were pre-existing designs from acknowledged experts in the field. So, while not perfect by any means, they still worked better than off the shelf. The questions being posed by the OP may seem innocuous enough to the average reader, but they're akin to going to a DIY aircraft forum and asking 'why do I need a wing?'.

[quote name='Boneless' post='540513' date='Jul 14 2009, 12:28 PM']I actually don't know WHY vertical alignment is better[/quote]Which goes to why everyone who does know how speakers work in this and other forums have told you that you should not be trying to design your own cab.

The simple physics of bass reproduction demand that if you're going to keep up with guitars driven to full volume you need four times the speaker complement that they have. So the options are they turn down or you get a bigger rig.

[quote name='Boneless' post='540430' date='Jul 14 2009, 11:12 AM']Many boxes have a similar alignment, so I guess it can't be too bad[/quote] Yes, it can be too bad. The basic design parameters of most commercial cabs are set forth by marketing departments, based upon what they think will sell, and that's almost always a matter of looking 'right'. But what's most pleasing to the eye is not what's most pleasing to the ear. The number one reason for building one's own cab is the ability to not have to settle for what some marketing department head who probably doesn't even play bass thinks will sell based on looks. Your reasoning for not doing vertical drivers is the same as theirs, and is intrinsically flawed. [quote]I'd actually rely on the woofers for true midrange (and, according to the charts, I should have plenty of it)[/quote]The charts aren't worth squat, because they show axial response. whereas 30 degree and 45 degree off-axis is what counts.

[quote]what does this mean?[/quote]That you haven't read the manual?

[quote name='Musky' post='532898' date='Jul 5 2009, 07:24 AM']Unless you're playing dub you don't want the LF version of the 3015 as it doesn't provide any decent output in the upper mids.[/quote] The 3015 and 3015LF have the same useful off-axis high frequency limit, so the axial midrange response isn't why you'd choose the one over the other. The 3015 is the better choice with a small amp, less than 250 watts, for its higher sensitivity. The 3015LF will put out more low end, but only if you have a large enough amp driving it. As is the case with all fifteens you can only get a good off-axis midrange response by crossing to a midrange driver at 1kHz or less.

[quote name='Merton' post='532753' date='Jul 5 2009, 03:32 AM']Good work Stevie! Like the investigative journalism Very interesting reading, makes me glad I didn't get the Mini15s I was looking at earlier this year [/quote] Don't be hard on Ashdown, most lower priced, and more than a few higher priced, combos and separates employ drivers with similar specs. As for a midbass bump, and corresponding lack of low end, that same response characteristic can be found in more than a few high end cabs, Schroeder and Eden among them. Not because they use cheap drivers, but because it makes the cab seem louder. Look at an Equal Loudness Curve to see why.

[quote name='Pookus' post='532674' date='Jul 4 2009, 05:29 PM']I am about to sell my Ashdown ABM900 head and 810 cab as I have left the band and want to do other things musically and don't need such a massive rig.[/quote] Dump the speaker, keep the head. Get a 2x10 for now, if you ever get back into it, and you will, add more speakerage.

[quote name='bumnote' post='532651' date='Jul 4 2009, 04:40 PM']I understand that a company might fit the cheapest speaker it can get away with, but why not port it properly, surely that costs nothing[/quote]Heard the one about a silk purse and a sow's ear? You can't use a sub-standard driver with a good result no matter what the box tuning. For that matter a driver with a Qts of .62 has no business being in a small ported enclosure in the fist place. It would work reasonably well in a sealed cab of some 15 cubic feet.

[quote name='Bassman Rich' post='532426' date='Jul 4 2009, 08:38 AM']Or is the cab too small to handle that type of speaker.[/quote] It's not too small to handle any fifteen. However, the smaller the cab the less low end it's capable of producing. [quote]at 8 ohms that should cut down the power from the amp (500 watt at 4 ohms) to under what the speaker can handle.[/quote] That's immaterial. Bottom line, if you want high output at low frequencies you won't get it from too small a cab. Before making an investment in a driver that probably won't cure your problems consider buying a well engineered cab that will.

[quote name='Bero' post='528955' date='Jun 30 2009, 01:38 PM']Whats the difference between a cabinet giving output power as ??? watts rms then ??? watts program. The RMS is always lower than the program, which should i take as the output power so that i dont get the wrong cab for my amp[/quote] RMS is what engineering departments use, for the purpose of technical accuracy. Peak, program, peak program, music power, peak music power and all that rot is what marketing departments use, for the purpose of generating sales.

Everything about that cabs says that whoever built it knows next to nothing about how to design a speaker. Pass.

[quote name='fatgoogle' post='526610' date='Jun 28 2009, 06:52 AM']Bill were should i cross if i want to add a tweeter to a 15" cab. I believe the speaker says it can go to 4khz. Sorry for the hijack.[/quote] No higher than 1.5kHz. The axial response of the 15 may well go to 4kHz, though if it does go that high I'd be concerned about its low end, that's very much in the realm of a guitar driver. But irrespective of how high the axial response is any fifteen's response drops like a stone off-axis above 1.5kHz at best.

[quote name='Protium' post='526297' date='Jun 27 2009, 04:39 PM']How do If I want to wire up an 8ohm tweeter with an 8ohm woofer do I need a full crossover or can I get away with just using a high pass filter @ 4kHz on the tweeter? Cheers[/quote] You can get away with it, but you shouldn't. High frequency output from the woofer will have a different phase response than the tweeter, causing destructive interference, and the impedance of the cab above the HF corner frequency will be 4 ohms, not 8. Many cab manufacturers do use a high-pass only, not because it's the right way, but because it's the cheaper way. BTW, if you're adding a tweeter it should cross no higher than 2kHz with 12s, 2.5 Khz with 10s. Manufacturers usually go much higher, it's true, but as for why they do, see above.

[quote name='small_lump_of_green_putty' post='524346' date='Jun 25 2009, 07:09 PM']I still don't understand why a seal is important around the edges. As for the lubrication, there's something called teflon these days, isn't there? [/quote][url="http://electronics.howstuffworks.com/speaker5.htm"]http://electronics.howstuffworks.com/speaker5.htm[/url]

[quote name='BarnacleBob' post='523413' date='Jun 25 2009, 05:58 AM']So 450-500 is an ok price but possibly swap the spkrs (if still origina)l out of the cab? BB[/quote] -1. The cab isn't worth putting new drivers into. Basically it's landfill.

[quote name='BarnacleBob' post='522758' date='Jun 24 2009, 12:32 PM']should i be looking for to make sure I'm not buying a dog/paying over the odds for it Would i be better going for the reissue tweed cover 4x10 Bassman combo. or an original if affordable and available? Only ever bought new amps up til now. BB[/quote] Not a bad amp, if you've got efficient enough speakers to work with only 100w. The Fender speaker, however,is absolute trash. The pictured model looks to be early 1970s. I don't know if they did a reissue, or if they did, why. It was a 2nd tier rig 35 years ago compared to an Ampeg V4, let alone an SVT. The Bassman 4x10 is a great guitar amp, useless for bass outside the studio. A pristine '59 is probably worth more than what you're driving, but only to a guitar player/collector.

[quote name='alexclaber' post='521743' date='Jun 23 2009, 09:38 AM']I'd like to get some hard data on driver failures. I know the vast majority of Acme failures are not voice coil related despite the huge power often being used to drive them and I've heard from other talkbassers in the pro-sound world that >90% of failures are mechanical failure, not voice coil overheating. Alex[/quote]My sources include Eminence and trade-only publications. A high reported incidence of creased cones usually indicates an insufficient xlim to xmax ratio.

[quote name='alexclaber' post='516909' date='Jun 17 2009, 04:14 PM']The more common failure method for bass guitar drivers and direct radiating subwoofers is mechanical failure.[/quote] Most driver failures are electrical, ie., voice coil burn out. The primary reason is thermal power compression. Driver voice coils driven with more than 100 watts or so get very hot. When the wire of the voice coil gets hotter its resistance increases, reducing driver sensitivity, which reduces output, which the player more often than not will compensate for by turning up the amp. This further heats the voice coil, further reducing output, and this cycle continues until the voice coil heats enough to either burn out or for the adhesives holding it together to fail. Prevention of this syndrome is why it's a good idea to run twice the speaker power rating than amp power rating. This practice also better matches the amp output to the amount of power than the average speaker's excursion limits allow it to actually make use of. It's also one more nail in the coffin of the Myth of Underpowering.

[quote name='riff raff' post='518965' date='Jun 19 2009, 06:22 PM']that article explains it very simply. is there something similair to explain the effect of having them side by side?[/quote] The exact same result will come from having them side by side, but in the lower midrange frequencies rather than the bass. The exact same result also comes from having drivers side by side in a single cab, but in the upper midrange frequencies.

[quote name='riff raff' post='518772' date='Jun 19 2009, 02:20 PM']what about if they were positioned either side of the drummer.he loves it.plus would give my rhythm guitarist a great monitor.he loves it too.in rehearsal he's always hanging around my cab.[/quote]Even worse. Read this: [url="http://www.prosoundweb.com/article/in_search_of_the_power_alley/"]http://www.prosoundweb.com/article/in_sear...he_power_alley/[/url] [quote]whats the relevance of the old ampeg cabs?? pretty sure mine is a very old one.i'll have to check.[/quote]The original CTS were 30 watt guitar drivers, as were the first generation (early 70s) Eminence that were copies of them. The result was great highs, but limited low end capability, so a pair of cabs were necessary to handle the SVT head. Later drivers have better low end, and don't require two cabs, but they also don't have the highs of the earlier cabs.

[quote name='riff raff' post='518675' date='Jun 19 2009, 12:38 PM']i,ve already got one ampeg 8x10.just want another to run them both together.[/quote]That opens a can of worms, for if you place them side by side you'll halve the lower midrange dispersion and exacerbate the upper midrange comb-filtering that already exists with one. Stacking them vertically gets around those problems, but isn't practical. Frankly I can't imagine the need for two, one is plenty to handle any stage size, and if it's not enough for the room, well, that's what PA is for.

[quote name='KASH' post='518419' date='Jun 19 2009, 09:31 AM']...and now in English? [/quote] If you don't understand what I said you wouldn't be able to build it anyway and will have to settle for that factory built stuff.

[quote name='Mr. Foxen' post='518260' date='Jun 19 2009, 07:00 AM']Doom. Always wondered what Ampegs have over all the other 8x10s. Is it just the name?[/quote] It's the drivers, which are particularly well suited to the sealed cab. The original CTS and first generation Eminence are preferred tone-wise, as they were guitar drivers with a much better high end. A modern alternative would be a 3015LF bottom cab to provide the low end, crossed over to a vertical 3x10 cab loaded with guitar tens at 200-300 Hz to give the high end of the original.