Bill Fitzmaurice

[quote name='TomRichards' timestamp='1443962606' post='2878978'] My local shop made me two cables about a year ago, and one of them was "bad". We tested them on the bench, and they both had the correct outputs. However, when we plugged them into the amp, one lacked all the higher frequency and top end. [/quote]That's an indication of high capacitance. It's very odd that you got different results with two cables cut from the same spool. The good news is that you need not spend more than a pound per foot for cable with the lowest capacitance and highest degree of shielding possible. Don't believe claims made for better performance from cables costing more than that, not even a hundred times more. If anything high priced exotic cables tend to have poor capacitance. Monster Bass cable is one example. It's capacitance is so bad that any reputable company would consider it defective and not sell it at all. Monster, however, is not reputable. [quote]But do cables have a major influence on tone? In my opinion, no[/quote]A good cable will have no effect, but a bad one will, and not in a positive way.

[quote name='lowhand_mike' timestamp='1443621142' post='2876325'] nothing like a bit of light reading for a wednesday afternoon, and thats nothing like a bit of light reading can you give us the concise version please bill? [/quote]http://barefacedbass.com/technical-information/speaker-size-frequency-response.htm

[quote name='JTUK' timestamp='1443608928' post='2876117'] My take...and it may not be the kiondest... is that players and bass players in particular, are stuck in the 80's... [/quote]More like the 30's. The answer to the basic question posed can be found here, published in 1940. http://www.introni.it/pdf/Olson%20-%20Elements%20of%20Acoustical%20Engineering%201940.pdf

[quote name='tauzero' timestamp='1443445768' post='2874712'] Does a rear port make any difference to that?[/quote]You shouldn't place a rear port tight to the wall, but three inches or so of air space is sufficient. [quote] A little thinking (which is possibly less than the minimum required) suggests that it would actually exacerbate the problem as the out-of-phase sound from the rear port would be additive with the sound from the front. [/quote]The sound from a port is not out of phase, at least not within the cabs intended pass band.

[quote name='discreet' timestamp='1443395071' post='2874406'] So it could be the case that I actually like the sound of a sealed cab, albeit one that just happens to have 10" drivers in it... [/quote]+1. For the most part sealed cabs do sound different than ported. It would be interesting if Ampeg had gone with twelves or fifteens instead of tens with the SVT. AFAIK the only reason they did go with tens instead of twelves was that they wanted to use 32 ohm drivers so that they could be parallel wired for a 4 ohm load, and there weren't any 32 ohm twelves available.

[quote name='geoham' timestamp='1443388155' post='2874367'] Presumably the 2.8 feet is measured from the back of the cab? [/quote]From the front.

[quote name='discreet' timestamp='1443354523' post='2874030'] I really don't understand why Alex comes in for so much flak on here and elsewhere. [/quote]It's because Alex tells it like it is, and people don't like having their pre-conceived subjective notions countered with factual objectivity. If the big manufacturers were concerned with anything but sales numbers they'd all have something similar to this on their websites: http://barefacedbass.com/technical-information.htm The fact that none do is telling. Where driver size is concerned this is pretty much definitive: http://barefacedbass.com/technical-information/speaker-size-frequency-response.htm But the ranks of those who'd rather cling to unfounded myth is legion, in any field.

[quote name='Musashimonkey' timestamp='1443295666' post='2873708'] My understanding is the wavelength will vary depending on notes played etc, but what's a good rule of thumb for how close to be to a wall for boundary reinforcement? [/quote]The general rule is to keep the cab as tight to the wall as possible. When the distance from the wall to the front of the cab is 1/4 wavelength you get a cancellation dip at that frequency, as the original and reflected waves meet 180 degrees out of phase. If the cab is, for instance, 16 inches deep that puts the 1/4 wavelength frequency at about 210Hz. Pulling it out further lowers the 1/4 wavelength frequency. There is a circumstance where you might want to pull it further out, that being a boomy stage. If you match the 1/4 wavelength frequency with the resonant frequency that causes the boom you can use the one to cancel the other. Boom generally takes place around 100Hz, where 1/4 wavelength is 2.8 feet, so that's a good distance to try.

[quote name='Chienmortbb' timestamp='1443034535' post='2871740'] Yes if you put it on a chair you will ruin the mutual coupling effect that the floor gives and loose a lot of the bottom end. [/quote]Only if raised by at least 2.8 feet. Still, I prefer a combination of tilting and lifting to aim the cab at your head. Tilting alone with a small cab can aim the mids above the audience. BTW, 'mutual coupling' is the technical term for when two cabs are placed together. Boundary reinforcement and space loading refer to when the cab is placed less than 1/4 wavelength from the floor and/or walls.

As the manual says keep it fully tumed up if you don't hear distortion, turn it down if you do. Don't expect to hear a massive difference in volume. There's surprisingly not that much difference between 20w and 150w; subjectively 150w isn't even twice as loud as 20w, let alone 7.5 times as loud.

[quote name='Merton' timestamp='1440755624' post='2853501'] More importantly interested to hear BFM's views on the Bass Array cab - it reminds me a bit of some of his designs [/quote]More than just a bit. All that differs is that they use cone midranges, by necessity, as horn loaded drivers would not fit in front of the woofer with that cab configuration. [quote]Doesn't sticking an array of open-back cone tweeters like that in front of another driver mean that you'll get colossal intermodulation distortion through the tweeters and on the reflected sound from the main driver? [/quote]The mids would have to be sealed back or contained within their own sub-enclosure to function well.

[quote name='kedo' timestamp='1440523054' post='2851571'] Should I consider a third party speaker (power handling should be 400w) and fit it myself [/quote]You should, but to do so you'd need the complete set of T/S specs and SPL chart on the original driver to be sure of a match, and that information is rarely divulged, mainly so that those in your position have no choice on where to get a new driver.

The 5kHz crossover to the tweeter is a bad idea. Twelve inch drivers start beaming around 1.6kHz, so the highest you want to cross over is 2kHz. At the othe end of the spectrum, 50kHz response is useless. Not only can you not hear above 18khz or so, there's nothing to be gained from an electric bass cab that goes above 8kHz except hiss. The vertical alignment of the woofers is the right way to do it, but otherwise I don't see anything to recommend these.

Impedance is not a constant figure, it changes with frequency, ranging on average (with an 8 ohm cab) from 5 to 50 ohms. A sealed cab has a single impedance peak, a ported cab two impedance peaks. By and large tubes prefer lower average impedance loads, which is what sealed generally provides.

[quote name='Chienmortbb' timestamp='1439196444' post='2840613'] Is this the marketing dept. using what they copnsiser a musical adjective? [/quote]Could be. A marketeer with no engineering expertise might think that a resonant cabinet was a good thing. As to whether the cab is resonant or actually inert, as it should be, one can only speculate. The reference to a resonant cabinet isn't the only market speak faux pas.[i] 'Orange signature skid runners to acoustically bond the cabinet to the stage and improve bass response' [/i]describes a phenomena which does not exist.

[quote name='Greg.Bassman' timestamp='1439143518' post='2840376'] Hi Bill. Forgive my ignorance, LPad? [/quote]http://www.bcae1.com/lpad.htm

[quote name='Greg.Bassman' timestamp='1439134047' post='2840278'] Even without a bass plugged in and the tweeter level set to zero, it can be heard. Rolling of the tweeter control off has no effect; [/quote]Assuming it uses a standard LPad that probably indicates that the LPad is bad or that the ground lead that should be connected to the LPad isn't.

[quote name='Thunderpaws' timestamp='1438984528' post='2839285'] Orange say they have a pleasingly reverberating enclosure. Does this make it an inherently poor cab design? [/quote]Any energy expended causing cabinet panels to vibrate is energy that doesn't exit the speaker as useful sound output. Where electronics are concerned Orange seems to have things well sussed, but where speakers are concerned, not so much.

[quote name='LukeFRC' timestamp='1438288920' post='2833371'] Would you class your simplexx range as a "commercial cab" option? [/quote]No. While they don't have a midrange they do specify the Eminence BGH tweeter, the only bass specific tweeter that I'm aware of. Used with a 4th order high pass it runs to 2kHz, nearly an octave lower than most commercial cab tweeters, eliminating the off-axis response dip which commercial cabs suffer from. It also rolls off lower, at 8kHz, reducing hiss. Crossing at 2kHz also eliminates the typical electric bass woofer break-up mode in the 2.5kHz-3.5kHz region, so overall response is flatter as well.

The only commercial cabs that I'm aware of that have reasonably flat response are Baer and Barefaced. If you want to be able to tell if a cab may have something close to flat response see if it has a midrange driver. If it doesn't, it doesn't. Even if it has a tweeter it won't be flat, there will be a response hole between the woofer and tweeter, if not on axis definitely off-axis. OTOH a tweeter isn't necessary, a good midrange driver goes as high as at least 90% of bass players really need.

[quote name='yorks5stringer' timestamp='1438152174' post='2832015']thought maybe with the Tweeter Box connected I'd get the full 60 watts [/quote]Adding a tweeter will give more output, but only in the highs, where the tweeter operates. As for the effect of going from 45 to 60 watts, it would be inaudible anyway.

[quote name='Dan Dare' timestamp='1437667212' post='2828060'] Good point, Bill. Despite the established consensus that one should drive preamps as hard as possible for best signal to noise, I find I get a cleaner sound out of my bass head (EBS 350) by running the output gain high and keeping the preamp gain well down so that the clip light never illuminates. I run my mixing desk channels well below the red, too. I think the advice originates from the time when circuitry was far noisier than it is today - you had to keep the hottest possible signal to mask that noise. As you say, passing an already clipped signal to a hefty power amp is asking to destroy your drive units. [/quote]Actually the advice dates to the early days of pro-sound when 100 watts was a huge amp, and instead of using enough of them to do the job sound providers did clip the power amps, resulting in this from JBL: http://www.jblpro.com/pub/technote/lowpower.pdf

[quote name='tauzero' timestamp='1437589404' post='2827389'] [url="http://sound.westhost.com/tweeters.htm"]http://sound.westhost.com/tweeters.htm[/url] - why tweeters blow, plus interesting bits on the trend to heavy compression in the recording industry and why using a bigger amp isn't the answer. [/quote]Most of that is correct, but it doesn't really apply to bass amps, and only partly with respect to PA. That's because bass amps and PA systems routinely pass clipped signals, some created in the power amps, but most created much earlier in the signal chain. Those clipped signals result in abnormally high THD, and that does kill tweeters. It's true that a larger power amp usually won't make any difference, because more often than not the clipping takes place in the pre-amp or in the mixing console.

I went from a digital board and separate amps to a powered mixer, this one (RX 1200L), as it does everything I need it to when mixing on stage: http://carvinaudio.com/collections/rx-series-mixers A separate board does offer more utility, but if you don't have a soundman running it you probably won't be able to make full use of it.

[quote name='MoJo' timestamp='1437245646' post='2824674'] Volts are volts, right? [/quote]Right. That doesn't mean that some Class D amps might not be anemic, but don't blame it on being Class D, blame it on poor design by the manufacturer. Powersoft wouldn't be where it is if there was something inherently deficient about Class D.