Bill Fitzmaurice

[quote name='Ghost_Bass' post='1041262' date='Nov 29 2010, 10:21 AM'][u]With two identical cabs, stacked, with the same setting on the amp (this includes the volume knob being untouched) we have[/u]:

- Two cabs running at the same time will have more volume than each of them soloed;
- The bottom cab running solo will have more than half of the the volume of two cabs;
- The top cab running solo will have less than half of the the volume of two cabs;

My main variable is floor coupling.
If anybody with knowledge could do the math with a simple example to try and find if i'm very far from the truth i'll appreciate.

Cheers[/quote]The volume of a cab is not related to watts, it's related to voltage. At a given gain setting the amp output voltage is constant, irrespective of the load impedance. Two cabs parallel wired both receive the same voltage as one, so if identical they will each run at the same volume. Floor 'coupling' in terms of a mechanical connection does not exist. Boundary loading from the floor does exist, and will be the same with two cabs stacked as with one on the floor, as the two cabs are acoustically coupled in the low frequencies where boundary loading occurs, acting essentially as one.

[quote name='Wil' post='1040946' date='Nov 29 2010, 06:25 AM']Probably a case of the head not being powerful enough to give any real volume increase when its output was split between the two cabs.[/quote]
Adding the second cab halves the load impedance, doubling the current flow and therefore power. Another 3dB of sensitivity comes from the mutual coupling of the two cabs, so with the same amp the total volume increase is 6dB, which is the equivalent of four times the power. Then figuring in the greatly increased intelligibility of the mids and highs from the top cab versus the bottom and there would have been a huge difference between both cabs and the bottom cab alone if everything was working correctly. Conclusion: something was AFU, perhaps a blown driver or two in the upper cab.

[quote name='Lemming16' post='1040063' date='Nov 28 2010, 11:24 AM']Whoa, thanks for your answers, so, do you think i should get a speaker with 200 Watts? (8 ohms) or one with 300 watts? (8 ohms too).[/quote]Watts are the least significant factor. What matters is frequency response, sensitivity and driver displacement. Don't even think about trying to design your own speaker. Find an existing tested design that meets your needs, use the drivers recommended for use with it.

[quote name='Phil Starr' post='1035927' date='Nov 25 2010, 04:27 AM']For me the middle graph is significant. It shows extreme excursion below 50Hz at high power which I think may be part of the problem.[/quote]Loaded in 50L tuned to 50Hz excursion is at a minimum at 50Hz, and with 200w input only exceeds xmax below 43 Hz, so save for extreme drop tuning excursion is no concern. However, where excursion is at a minimum port output is at a maximum, seen in a port velocity chart, and that's what attention must be paid to where chuffing is concerned.
[quote]I also question the extent to which you will hear the differences at these frequencies. I've been experimenting with just this at the moment with a low Q driver in an optimum box a high Q driver in a smaller than optimum box and running A/B comparisons with and without ports. Playing recorded music through them you get to hear all the things you'd expect. Earlier roll off and slightly reduced but cleaner bass from the sealed cab and warm woolly bass from the undersized cab, but you have to choose the source carefully to hear this. With bass guitar I can hear a difference but my guitarist can't and with the full band playing I'd be dishonest to say it makes a whole lot of difference. We just aren't very good at hearing deep bass and if you can't hear it it doesn't matter.[/quote]All true from the standpoint of what you're hearing on stage, where more often than not boundary effects severely limit audibility below 60 Hz or so. Combined with the masking effects of the other instruments you can eliminate much, if not all, content below 60Hz and not notice the difference when the band's playing. But in the audience the situation can be very different. You can be totally unaware of high output in the lows where you're standing, whilst 40 feet away patrons are contending with drinks falling off their tables. It's the 40 to 60Hz bandwidth that large PAs pound out with authority that can define good concert sound, or for that matter ruin it when there's a ham-fisted idiot at the FOH console.

[quote name='jonthebass' post='1035087' date='Nov 24 2010, 09:02 AM']Blimey, my heads spinning from this thread![/quote]
Science does have a tendency to win out over dogma, though sometimes it takes a while. Ask Galileo.
[i]'In 1979 Pope John Paul II asked that the 1633 conviction be annulled. However, since teaching the Copernican theory had been banned in 1616, it was technically possible that a new trial could find Galileo guilty; thus it was suggested that the 1616 prohibition be reversed, and this happened in 1992. The pope concluded that while 17th-century theologians based their decision on the knowledge available to them at the time, they had wronged Galileo by [b]not recognizing the difference between a question relating to scientific investigation and one falling into the realm of doctrine of the faith[/b].'[/i]

[quote name='Phil Starr' post='1034915' date='Nov 24 2010, 06:40 AM']Sealed cabs have better power handling and much better transient response than reflex cabs. For a given speaker the cab will be smaller. The trade off is that the ported cab gives an extra 3dB of bass around the resonant frequency and the f3 roll off point will be raised in a sealed cab. Having said that there is often more deep bass from a sealed cab ie deeper but not so loud.[/quote]Those observations do apply in a few cases, depending on the driver specs, but only a few. For the vast majority of drivers, no. In this case, a very low Qts driver, a sealed cab is totally inappropriate. It models very well in 50 liters net vented.

[quote name='Moos3h' post='1034209' date='Nov 23 2010, 01:48 PM']I'm SURE there must be a reason why this can't be done?[/quote]
The same reason one doesn't fill the boot of their auto with concrete so that they might get all of the horsepower out of their engine. You'll use a lot more gas but you won't go any faster.
I believe the subject is addressed in the FAQ.

[quote name='LawrenceH' post='1034111' date='Nov 23 2010, 12:15 PM']I honestly can't see what's at all controversial about the idea that porting is used to boost low-end output of speakers but comes with its own set of compromises and complications, and if it wasn't necessary to boost LF volume output we wouldn't use it.[/quote]There's nothing controversial about it, it just isn't true. One doesn't properly use a sealed versus ported alignment for any reason other than the specs of the drivers employed and the results desired.
[quote]With sealed cabs you get a nice gentle drop in frequency response that is much more easily matched with a simple shelving filter than the more complex rapid drop (with small hump or shelf) associated with ported cabs[/quote]One can obtain the same results with either topology. And one can obtain totally different results with either topology. One just has to know what one's doing.

[quote name='4 Strings' post='1033517' date='Nov 23 2010, 03:48 AM']So, it seems I'm not going to improve things too much by changing the driver but might do so with adjustments to the port.

Bit difficult to tell if the port is 'chuffing' or the speaker complaining. Assuming we do have 'chuff', what to do?

There's not really space to make the port larger in diameter, what if I made the tube longer? How long would be best?

What if I made another 3" port (say, in the back). What length tubes would be best?[/quote]Catch-22. A 3" port is too small in diameter to not chuff. A 4" would probably relieve the chuffing, 5" is better, but both require far longer ducts. The larger duct volume subtracts from the net cabinet volume, which raises the cabinet tuning and leads to boomy response. IMO you have a nice driver deserving of a new home. I wouldn't invest any more in the old one.

[quote name='LawrenceH' post='1033133' date='Nov 22 2010, 03:06 PM']hence the 'loudness function'[/quote]
That is intended to address the issue of equal loudness. To do so it boosts both the lower and upper end of the spectrum when the volume pot is set at low levels, with the effect diminished as volume is increased.

[quote name='LawrenceH' post='1033098' date='Nov 22 2010, 02:35 PM']Bill has again decided to obscure my point entirely by saying that if 'sealed was superior then that's what would dominate the market'.[/quote]
By the market I meant speakers in general, not just electric bass. In home use output isn't the concern that it is with pro-sound, and yet ported still dominates every segment of the hi-fi market save one, HT subwoofers. There sealed is well represented for two reasons: cabin gain and high driver Qts.

[quote name='LawrenceH' post='1033024' date='Nov 22 2010, 01:32 PM']I do wonder though, how many people actually regularly listen to bass on decent sealed systems, monitors, hi-fis or cabs? We're probably more used to adapting to ported cabs. I can't use sealed cabs as an effective solution for compact bass cabs due to the loudness issue, but they are very revealing. Perhaps too much for some people.[/quote]
Is sealed was actually superior then that's what would dominate the market. I agree that poorly designed and built ported speakers sound like crap, but that's because they're poorly designed and built, not because they're ported.
As to the quoted article, not much there to impress. Especially this :[i]"The classic Yamaha NS10 is too, and while its overall frequency response isn't quite as refined as that of the LS3/5A, its time domain precision enables it to provide superb clarity and separation of the bass elements in a mix, which is partly why it has been such a popular studio reference for decades."[/i]

The real reason for the popularity of the NS-10 was its resemblance to the consumer speakers that average listeners would be using. It was always said that if you could get a mix to sound good through NS10s it would sound good through [i]anything[/i].

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 05:35 PM']I read somewhere about the K-200 having a low Qts reduces its bass response. I don't know what that is.[/quote]True, although that's offset somewhat by the low 35Hz Fs. You can get more low end out of a driver with higher Qts, but not in a 1 cu ft box.

[quote name='LawrenceH' post='1032100' date='Nov 21 2010, 06:53 PM']And regarding tone, if loudness weren't an issue most designers wouldn't even use porting.[/quote]Not any designers I know.
There's nothing the least bit magical about sealed cabs. Most cabs in the 60s were sealed not because they sounded better but because most of the drivers available didn't work any better in vented alignments. Designers/manufacturers who still create sealed cabs don't do so because they're better, they do so because they sell, mainly to customers who think there's something inherently better about the tone of a sealed cab. The fact of the matter is that a good designer can precisely duplicate the transfer function of a sealed cab with a vented alignment.

[quote name='ThomBassmonkey' post='1031923' date='Nov 21 2010, 04:24 PM']I've looked through this thread, but I can't see specifically what the problem caused by horizontally placed speakers is.[/quote]
Dispersion is inversely proportional to the dimension of the radiating plane. Horizontal dispersion of two drivers placed horizontally is half that of two drivers placed vertically. Explained in great detail here:
[url="http://www.gtaust.com/filter/06/08.shtml"]http://www.gtaust.com/filter/06/08.shtml[/url]

[quote name='4 Strings' post='1031039' date='Nov 20 2010, 07:11 PM']Turns out the current driver is a Beyma K-200, not familiar with it myself. Has a huge magnet but no impedance marked.[/quote]
The 12K200 is a premium driver. There's nothing wrong that putting it into a well designed and built cab wouldn't cure.

[quote name='TimR' post='1030968' date='Nov 20 2010, 05:57 PM']How loud does an 8x10 'sound' compared to a 4x10 vertical stack?[/quote]That depends on the 8x10 and vertical 4x10 in question. Some vertical 4x10s have higher sensitivity and displacement limited output than some 8x10s, especially sealed 8x10s.
This is a maximum SPL plot of an SVT (blue) and a pair of 3 cu ft ported 2x10s loaded with Deltalite II 2510s (red). Where power/output demands are highest, from 41 to 65 Hz, the pair of 2x10s are louder.

[quote name='4 Strings' post='1030142' date='Nov 20 2010, 03:53 AM']The cabinet is around 13cu in (ie about 14 x 14 x 12)[/quote]
That comes down to about 1 cu ft net, and no driver is going to give [i]"plenty of bass in it to get an deep tone, which can go nice and deep"[/i] from a box that small. IMO it's not worth replacing the driver, put the money in a better/larger cab, used if $ is an issue.

[quote name='TimR' post='1026762' date='Nov 17 2010, 06:54 AM']I wouldn't mod the amp. I would build a box to sit on the amp that provided the 9v and had two 1/4" sockets.[/quote]The entire point of phantom is simplicity, which a separate box isn't. Someone with the chops to rightfully consider doing this isn't the least bit daunted at the prospect. I've run phantom for 30 years and never had a problem. Or a dead battery.

[quote name='dincz' post='1026042' date='Nov 16 2010, 11:41 AM']That's what I have in mind, but my only concern is the use of a standard connector which would allow accidental connection of standard gear/instruments that might be damaged or that might damage the power supply.[/quote]That would happen if somebody plugged a mic into your amp. A four conductor XLR would remove that possibility, as they're hardly used for anything anymore. So much so that they might be hard to find.

[quote name='dincz' post='1024238' date='Nov 15 2010, 01:43 AM']I'm thinking of modding my amp and bass to provide 9V for the onboard preamp and so avoid the problems that go along with batteries. It should be simple enough to do, so I wonder why manufacturers of amps and basses don't already offer this feature. Or do they?[/quote]
It's simple, use an XLR at either end, tap into one of the pre-amp's positive rails. If the on-board will take more than 9v you can get additional headroom, but if not use a 9v voltage regulator. Be sure to filter the supply at the bass end. The advantage is never having a dead battery. Be sure to retain the 1/4" at both ends and back-up battery on board in case you ever need them.
Manufacturers don't offer this due to compatibility issues.

[quote name='Conan' post='1025729' date='Nov 16 2010, 07:19 AM']Do we hear what we want/expect to hear?[/quote][url="http://www.youtube.com/watch?v=BYTlN6wjcvQ"]http://www.youtube.com/watch?v=BYTlN6wjcvQ[/url]

[quote name='thisnameistaken' post='1025404' date='Nov 15 2010, 08:25 PM']If you say that two twelves stacked vertically would be better than what I've got now.[/quote]Not better, different. Whether that different is better or worse for you only you can judge. But to say that if one's using four tens that the only way it should be done is to put them into a typical 4x arrangement is to ignore an alternative that most players who have actually tried prefer.

[quote name='Stewart' post='1025306' date='Nov 15 2010, 06:00 PM']- why would you NOT want to do that?[/quote]
There are two primary reasons why things are done as they always have been: 'It's how we've always done it' and 'It's the only way we know how to do it'. Those who open their minds sufficiently to allow for alteration of the latter don't have to forever conform to the former.

[quote name='Mog' post='1025136' date='Nov 15 2010, 03:16 PM']Its just for monitoring for the guitarist as some of the stages can be very wide. Maybe 18-20 feet between stacks. I only run a 150 watt head so theres not much chance of bleed into the FOH feed. Loads of power IMO. Even in medium sized clubs the PA does all my grunt work. I'm not into the whole 1k bass head thing. Just dont get it?[/quote]
Put one cab on the floor aimed at the guitar player. What he can't hear are your directional mids, and with your extension placed below his it's not doing much good there anyway, most pass him by at the knees. Put the other cab atop the first, aimed at you.