Bill Fitzmaurice

If they're identical sensitivity and maximum output go up by 6dB, the equivalent of quadrupling power. Intelligibility of the mids and highs for you increases by having the source closer to ear level.

7 hours ago, Steve Browning said:

For years I always removed anything between the cab and the floor. After getting a 2x18 that was immovable without I indeed found there was not the blindest bit of difference. Years of shifting utterly wasted.

 

Get some decent 10cm casters with brakes and don't look back.

By the same token isolation doesn't work either. Isolation can reduce the vibrating of a cab atop a soft floor, which is vibrating as the result of acoustic resonance excited by the speaker output. What it can't do is reduce the vibration of the floor, as that's acoustically sourced, not mechanically.

http://ethanwiner.com/speaker_isolation.htm

https://www.bassgearmag.com/submit-article-bass-amplifier-isolation/

29 minutes ago, DGBass said:

I just meant my particular MDF box cab🙂 And I guess you are saying the answer is Yes, it could make a difference to the sound although the yes word isn't specifically mentioned.

Yes, because what works in one speaker works in all speakers. The physics are the same, no matter what it's made of. MDF may not benefit from bracing as much as thinner, lighter materials, but it's not two inches of concrete either. OTOH bracing is what allows me to use cabs made of 3mm and 6mm plywood, with no ill effects either from a sonic standpoint or a physical standpoint, that being to my ancient arthritic spine. 😁

1 hour ago, Dan Dare said:

 

Bill, should you allow for the wadding when working out cab volume, or does it not affect it? Thanks.

it has no effect when used as lining, as it doesn't affect the low end where the cabinet defines response. When used as stuffing it does affect the low end, and should be taken into account during the design phase. If you want to make a sealed cab as small as possible stuffing is a must. However...

In 1995 a respected audio enthusiast named Ton Nousaine did some experiments with stuffing. Noting that it reduced a midbass response peak, similar in fashion that a larger box reduces a midbass response peak, he erroneously concluded that stuffing gave the same result as making the box larger. It does not. Stuffing and larger boxes both lower the speaker Qtc, which reduces a midbass peak. But a larger box also lowers the speaker frequency response and increases low frequency sensitivity. Stuffing does not. It actually reduces sensitivity. His error was due to not collecting adequate data to fully explain what he observed. Unfortunately he published his theory, which was widely accepted on the basis of his reputation, and the myth that stuffing a sealed cab gave the same result as making it larger was the result. That myth persists, to the extent that if you google 'stuffing loudspeaker' you'll find numerous references that continue to get it wrong, as they keep repeating the same flawed initial conclusion. The error would be obvious if they used loudspeaker modeling software to confirm what's going on, but they don't, because they don't know how.

1 hour ago, DGBass said:

The question about whether the inherent sound of such a cab will change by extensive bracing and wadding is still open.

That question was answered during the golden age of loudspeaker design, 1938-1973. The hi-fi guys knew it, the PA guys knew it. A few electric bass cab manufacturers knew it, those being manufacturers that also did hi-fi and PA, like JBL and EV. The mainstream musical instrument manufacturers didn't, operating in a vacuum as it were. JBL and EV never really cracked the musical instrument market, because they didn't make amps, and in those days amps and speakers were almost always sold as a set.

Where coloration is concerned Eminence intentionally imparts it, as it's been part and parcel of their tone going all the way back to the CTS days. One could even say it's part of the history of the sound of the electric bass, much as Celestion holds that position with electric guitar.

Only if it's 40cm or more closer, and that wouldn't affect it down low. You get full boundary reinforcement when within 1/4 wavelength of the boundary. 1/4 wavelength at 100Hz is 85cm, and the lower you go the longer a wavelength is. 

That's one way to look at it. The other is that they really didn't know what they were doing where cabinet design is concerned. Fender certainly didn't, not until the 1990s. Even today Fender isn't state of the art by any means. There are two reasons to brace. One is to silence panel vibrations that detract from the speaker sound. The other is to improve the efficiency of the speaker. Energy wasted causing panels to vibrate doesn't end up in the audience.

A good front to back method is to have a brace or two attached to the baffle at driver attachment screw locations. That way the driver is more securely connected to the box as well.

The Fs is a bit high, Vas a bit low for best results, though that's probably Greek to you. Nonetheless they'll work well enough in a number of my designs. For specific recommendations ask on my forum. They'll also work in other ported designs where the Eminence Beta 10 is recommended.

6 hours ago, Bunion said:

They’re in ampeg cabs too the stop the horn from blowing, my old 210 is a normal car tail light but I think they’ve updated them now to something more fancy 😄

They've been using 24v aircraft bulbs for quite some time.

4 hours ago, Phil Starr said:

These are really common, it's a really simple solution to protecting the speakers, mainly the tweeters. The bulb has a very low resistance when cold but as the current increases it heats up and the resistance rises reducing the current to the tweeter. In the quieter sections it cools down and full power is restored. 

Correct. In effect they work like a compressor, taming transient peaks that otherwise might cause the tweeter to fail. In extreme cases of overpowering they'll blow, turning them into fuses, although that's not their intended purpose. Those extreme cases are usually the result of using distortion effects, which increase the high frequency power content well beyond what most bulbs or tweeters can handle.

Wadding, more properly referred to as damping, serves two purposes. One is to reduce internal reflections in the cab, which cause peaks and valleys in response. How much will give the best result varies from cab to cab, with between one and two inches usually being good.

The other purpose is to lessen midbass boom, which takes more material. In sealed cabs with high Q drivers, which have a tendency for boomy response, the cab might be fully filled. In extreme cases it may be not only filled but also compressed. Well designed ported cabs don't use high Q drivers, so they usually don't boom and don't require filling the cab to tame it. Of course not all ported cabs are well designed, so more than an inch or two of damping could be beneficial. A ported cab would never be stuffed and compressed, as that would mess with the cab tuning and could kill the low frequency output. 

How damping affects response and impedance can be software modeled by changing the Qa value. 100 is a bare cab, 50 is lined, 10 is filled, 5 is filled and compressed. It's an approximate result, as different materials have different indexes of absorption. It also is only accurate to roughly 2 to 3 octaves above the box frequency, as are all the results with speaker modeling software.

The only reason to not use any damping is cost. 🙄

It makes no difference. The connection to the floor which gives boundary loading isn't mechanical, it's acoustical.

14 minutes ago, Marcus Cornall said:

 

Its just like the thing Bill said about 'the tube sound' coming from the power stage.- I have not seen that simple truth stated on any of the things I have read up on trying to understand it on my own.

 

 

Amp manufacturers, certainly those who don't sell all tube amps, won't tell you that. To some extent one can get some of that tube response by over-driving a tube in the pre-amp, but it won't come close to an over-driven tube output stage. It's not just the tone and response that's different, it's also the perceived volume created by compression. That perception is the reason for the never ending 'tube watts' debate.

Most recordings since the late 60s were direct to the board, because the speakers of the day were so poor. To the extent that amps were used in the studio it was as monitors. James Jamerson was known for using an Ampeg B15, but he almost always went direct, using the same Motown DI direct box now sold by Acme Audio. https://reverb.com/item/4394324-acme-audio-motown-d-i-wb-3-direct-input-box?bk=eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiJmZDdmYTI4OC1lODRkLTRkOTktYTI4NS1kZmU3ZmRkODA1ZjYiLCJpYXQiOjE2NzY4OTk1ODAsInVzZXJfaWQiOiIiLCJzZXNzaW9uX2lkIjoiOWYzOTNiMWMtOGM3ZS00NmI4LTg4ZjgtMjgyMjBkZDQ4MDJiIiwiY29va2llX2lkIjoiZDI5ZDI5N2QtYjIzNS00NWQ3LWE4NDAtMDA2NTFmYjdiMjc0IiwicHJvZHVjdF9pZCI6IjQzOTQzMjQiLCJzb3VyY2UiOiJOT05FIn0.7kZRDnlmhcQeqDRlfrndRM4mKyYWa2Gu9Wg-jhwje7A

1 hour ago, Marcus Cornall said:

1. I am considering an amp containing a tube.I have never had one before. Try not to laugh! 

I didn't have the income for a proper amp before either.

I am considering it because I would like a more 'vintage ' sound,which at the moment is what comes out of my Cort-essentially a rw P

Vintage sound doesn't come from a pre-amp tube. It comes from a power tube output section, which between the natural compression imparted by them and the output transformer imparts response that can only be more or less duplicated with amp emulation DSP.

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Question 2  is ...what size of wattage of amp would you use with a BB II in those circs?

Between 1/2 and 2x the speaker thermal rating. Knowing that low price amp specs can't be trusted I'd avoid those.

2 hours ago, Marcus Cornall said:

  But you can hear those freqs.i can anyway.

No, you can't. What you can hear when playing tones below roughly 30Hz is their harmonics. Even if the source is a tone generator that only produces sine wave fundamentals harmonics are still there, created by the speaker. If it's a square wave generator harmonics are there in spades, as what makes a square wave square is harmonics.

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my Reggae bass taste personally is to sound as purely 'fundamental only' as possible

You may think that's the case, but electric bass produces mainly harmonics, especially below 100Hz. Classic reggae tone is primarily 2nd and 3rd harmonics. This is an RTA of a PBass playing an open A string. Most of the energy is in the harmonics. With lower notes there's even less fundamental and more harmonic content, and this is with the pure signal from the bass. The coloration imparted by the speaker results in less fundamental content.

Figuring out what's going on with just ones ears is daunting, even if you know the physics. That's where measurements come in. That used to be an expensive proposition, but not today. Download this to your phone: https://play.google.com/store/apps/details?id=com.dom.audioanalyzer

Set it to Sound Analyzer, 1/3 octave bands, C weighting, Slow weighting. Ideally you want to input a pink noise source into your amp. You can download a pink noise loop to your PC. With that you can see in real time the effect of moving the cab. The phone needs to be placed where your ears would normally be with respect to the speaker, and not moved during the testing. That's critical, as even a slight change in the mic placement will alter the result. http://ethanwiner.com/believe.html

2 hours ago, jrixn1 said:

 

 

Hi @Bill Fitzmaurice

My understanding is that subs are omnidirectional.

All speakers are below the frequency where the baffle is one wavelength across. Above that they shift to directional. As you keep going higher the radiation angle keeps shrinking. Since a wavelength at 100Hz is 3.4 meters it takes a large cluster of subs to be directional.

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In that case, is there any point in any speaker on stage (backline or monitors) reproducing frequencies below 100Hz?

It depends on how far the backline is from the subs. But by and large if you're getting a lot of output from the subs on the stage it's mostly below the frequencies that your backline cab is producing, the fault of a sound man who doesn't know what he's doing. IME the #1 fault in concert sound today is sound men pushing the bass at lower frequencies and higher levels than they should. I had the pleasure of seeing 'Tower of Power' tonight and the sound man actually got it right. It's a good thing, if he'd turned fabulous funk bass into a boomy unintelligible mess I'd have had no choice but to hogtie him and hijack the board.

Looking at a picture the port is so close to the rear of the cab that if that's happening it's minimal. As for the Hybrid Resonator, I don't know what it is. Possibly a dual chamber reflex, which would explain the port placement, and the description of what it does. Nonetheless for the space between the cab bottom and floor to act as an effective extension of the port it would have to be placed in the middle of the bottom.

1 hour ago, Obrienp said:

Well, I’ve given the Markbass Tilt Stand a couple of tries and I have decided it’s not working for me and the BF One10. It put the cab in a great wedge monitor style position but all coupling between the cab and the floor was lost. This seemed to get rid of a large chunk of bass and make the mids very prominent.

In order to lose the coupling between the floor and cab the cab would have to be lifted at least 60cm off the floor. No bass was lost, it just seems that way because you're hearing mids and highs that you weren't before.

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I think this would be less of a problem with a front ported cab but the One10 has the port on the bottom in portrait mode, so it just vented into the air rather than deflecting off the floor.

That doesn't make any difference either. The port frequencies are lower than those from the cone, making the wavelengths longer, so the port would have to be even further from the floor to lose coupling, at least 150cm. If you're running with the same EQ on the stand as you did before that explains the mid content being more than what you want.

1 hour ago, Marcus Cornall said:

But it would also seem from what you say,that running ,say a 500w amp actually giving  say 350 into the single BB 12  wouldn't be enough to drive the driver properly then?

There's no such thing as enough power to drive it properly. There's only enough power to go as loud as you need to. That could be 100 watts, it could be one. How much is enough? The Ampeg B15 is 30 watts. Horses for courses.

The more watts the louder, yes, but running either an amp or speakers to their limit isn't a good idea, for their longevity or that of your ears.

Compare this to a car. Let's say the speedometer goes to 240 KPH and the tach goes to 7,000 RPM. That doesn't mean you should be driving 240 KPH at 7,000 RPM. You can, but probably not for long. The car has that capability so that it will run for ten years or more at 120 KPH at 2500 RPM. 

How many watts is enough? Between one half and twice the speaker thermal rating. One half is usually enough to drive a speaker to its mechanical limit. Twice gives you more amp headroom, which gives cleaner tone.

If your amp can only deliver half the speaker's mechanical limit that's at best -3dB from the speaker's maximum output. -3dB is audible, but just. As for linearity of power versus loudness, it isn't. It's a logarithmic relationship. That's why I said the first 100 watts are the most significant. That gets the average speaker output to the vicinity of 115dB at one meter. 115dB for extended periods will cause hearing loss. (Just ask Pete Townshend. You'll have to speak loudly.) Luckily we tend not to stand 1 meter from our cabs, but still, it's louder than we usually play at. A more reasonable 109dB takes only 25 watts. Where the next 75 watts come in is headroom, again so you're not running the amp at it's limit.

Going beyond 100 watts, if for some silly reason you want it twice as loud 200 watts won't do it. That only gets you to 118dB. Twice as loud as 115dB is 125dB. That requires 1,000 watts. Not that it matters, at that level you'll go deaf in short order. The only advantage to having 1,000 watts over 100 watts is that it gives you 10dB additional amp headroom, so that you won't clip it on hard transients. But with a realistic 25 watt average draw you only need 250 watts for 10dB of headroom. 

The last factor comes down to specsmanship, the fudging of data by marketing departments. The higher the stated power output the more likely the marketing department is writing cheques that the engineering department can't cover. Some companies are famed for doing this, TC and Bugera being two. Some have a well earned reputation for honesty, Ampeg being one. If only there was a comprehensive independent testing source to separate the wheat from the chaff, but there isn't. This is where cost versus claims comes in. If the price makes it seem to be too good to be true it probably isn't.

1 hour ago, Marcus Cornall said:

So you don't have to put the full 800 into the cab to get the best sound +/ loudest output from it then?

No, and for that matter chances are you may never put the full 800 watts into it. The first 100 watts are the most significant, and in most cases you won't put much more than that into it, other than as short transient peaks.