Bill Fitzmaurice

Tweeters don't hiss, amps do. That said, the response of the BGH25-8 rolls off above 8kHz, where there's no useful electric bass content, but plenty of hiss.

4 hours ago, Chrisan2 said:

 i smelt a electrical burning smell for a couple of seconds before it stoped , sent it to the fender repair agent. He said there was a blown power tube , and a blown fuse. Maybe there was more to it than that, and i just didn't get all the details .

A blown tube can take out other components and cause a blown fuse. If you were to just remove a tube it wouldn't stop the amp from working, although if one does that because they notice a tube is ready to go they should remove two, from opposite ends of the amp, to maintain balance.

It should have. There are two banks of three tubes, those three tubes being parallel wired. The amp should still work even with only two tubes, on from each bank, in place. Four tube models, like the Twin and Showman, had two banks of two tubes. With one or two tubes removed the difference in how they sounded was imperceptible.

2 hours ago, Owen said:

My hearing is too compromised to get excited about loud any more. But deep is The Bomb. I had an ACME 12" which was appreciably bigger than the "standard" 12" cabs. It went beatifully deep.

The reason I said deep and loud is that one can make a small cab that goes deep without boom. But doing so one sacrifices sensitivity, so while it's an option for home hi-fi and auto sound it's not for electric bass. The sensitivity issue can be offset by having a lot of power, and a driver that has both the electrical and mechanical ability to use it, but that sacrifices midrange response.

2 hours ago, GlamBass74 said:

 I'd expect an enclosure of this size to be quite boomy if driven hard, but it isn't. 

Boom isn't caused by cabs that are big, it's caused by cabs that are too small for the drivers within. One common shortcoming of commercial cabs is that they are too small, a marketplace concession to the desire of players to have a smaller rig to haul. But just as our instrument necks are long and our strings are fat our cabs need to be large if one wants to go deep and loud without boom.

It's logical to assume that the air volume of the room is the main factor, especially as decibels measure the intensity of an acoustic pressure wave. But cabin gain is something else entirely. This will help: 

4 hours ago, uhuglue said:

Hi Folks. I am looking for an amp to pair with my Orange Cab but am unsure whether to go for a 200w (4 ohm) or 500w (4 ohm).

Anywhere between one half and twice the speaker rating is appropriate for the amp size. One half is usually enough to drive the speaker to its full mechanically limited output. More power gives more amp headroom, while too much power will cause distortion that will encourage a sensible person to turn it down. The mechanical limit of your Eminence Kappa 15 loaded Orange in the critical 50-80Hz range is 100 watts, so even a 200w amp has sufficient headroom.

13 hours ago, Dan Dare said:

Low frequency reproduction is, of course, "possible even in small volume" - my headphones tell me that. However, the tiny drivers in my cans only need to energise the minute amount of air between them and my eardrums.

What you've hit upon here is Pressure Vessel Gain, more commonly referred to in audio as Cabin Gain. It has to do not with the volume of air but the dimensions of the room. There is a sensitivity gain at a rate of up to 12dB per octave as frequency goes down below where the longest room dimension is one-half wavelength. In a living room that's 5 meters long cabin gain starts around 34Hz. In a car that's 2 meters long it starts at 85Hz. Cabin gain is what allows the silly high bass levels achieved in auto dB competitions. A club is too large to have any cabin gain, but in an ear canal it covers almost the entire audio range.

With isobarik the result of using two drivers is halved Vas, the volume of air having the same acoustic compliance as the driver suspension. This allows halving the internal volume of the cabinet, not counting the space taken up by the second driver and the air space between the two drivers, without any loss of low frequency response. As always there is a trade off. In this case since the cone area and excursion radiating to the outside air is that of only one driver the maximum output is the same as with one driver in the net doubled cab volume. One could stuff the chamber of an isobarik, with the same result as with a standard alignment, lowered Q.

Isobarik was a reasonable alternative to huge enclosures fifty years ago, when driver Vas was generally much larger than today. For instance, the fifteen inch Altec 421 8LF Vas was  600 liters. The modern equivalent Eminence 3015LF Vas is 159 liters.

15 minutes ago, itu said:

Adding volume by filling the cabinet with denser material, or making it "look" bigger to the element have not been as succesful as using bigger cubic volume.

That's because stuffing doesn't make the cab look bigger. It lowers the cab Q, which can tame a midbass hump. Making the box larger does that, but making the box larger also lowers the speaker cutoff frequency, stuffing does not. Some 25 years ago a well respected audio expert measured some data and made the conclusion that stuffing made a box act as if it was larger. His conclusion was erroneous, because he didn't measure enough data to reveal what actually occurred. He published his conclusion, and based on his reputation alone much of the professional audio engineering community accepted it at face value without testing to make sure it was true. In both audio and nuclear arms treaties you can trust but you also must verify. 😉

19 minutes ago, Dan Dare said:

 That's an iron rule, I'm afraid.

Hoffman's Iron Law, to be precise. It's not all that far off from what itu said. On the subject of small drivers they give better midrange dispersion, and can be used in multiples for adequate volume, if they're arranged vertically. When they're not, which is usually the case, you lose their advantage in the midrange dispersion and introduce comb filtering in the highs.

For guitar, sure. For bass, probably not. Bass speakers require much larger enclosures than guitar to go low. About the smallest you can go with a twelve for good low end is 60 liters. Their 12B is in the vicinity of 20 liters.

7 hours ago, gjones said:

I am playing at a venue, which has a terrible boomy stage, next month.

Weirdly, the boom could only be heard onstage. But was so bad it was drowning the guitar out.

That's room modes too, although in the opposite of the usual fashion. The more common result is cancellation of low frequencies on and near the stage when reflections off nearby walls and ceiling meet the original wave front 180 degrees out of phase. When you move away from the stage into the room the relative boundary positions shift, the cancellations cease and the lows return. This phenomenon is what gave rise to the myth of wave propagation, the notion that a wave won't be heard until one is far enough away for the wave to develop. Believers of this myth have no explanation as to how headphones work. 🙄

Whether the bass is too much on stage and not enough out front or the other way around the best solution is to adjust the bass amp for the stage tone and volume and the PA for out front. The problem lies when you don't have PA. I don't know about the UK but in the States it's always been the band's responsibility to provide the PA in most venues. We used to say that we played the gig for free, what we were paid for was providing the sound system.

40 minutes ago, Jaybeevee said:

just talk bass and other forums. Just punters putting in their two penneth

We've got a saying in the States about sphincters and opinions, I've got to assume you have a similar one on your side of the pond. That's especially true of Talk Bass. I had to leave there ten years ago lest I lose what was left of my sanity completely. 😳

I bought a Bassman 50 watt new, in 1966. Even by the standards of the day it was weak, especially in the lows. Not surprising, as it was a re-badged guitar amp. The 'deep' switch didn't make the tone deeper, it just muted the highs. A 30 watt Ampeg B-15 blew it away on all counts. That's when it began to dawn on me that watts don't mean much.

That's the room modes that I mentioned. Parametric is about the only cure for those, and not without cost. They manifest as a product of the positions of the room boundaries, the cab placement and the listener position. Move any one of those three and the result changes, so using a parametric to kill boom where you're standing can kill useful frequencies in the audience. That's why I always adjust my tone from well out front, and whatever that happens to give me on stage I just live with.

IMO sterile. I don't know where you've read that stuff, but from day one the sound of the electric bass was defined not just by the instrument but also by the amp and speaker, and they were anything but clean.

Isolation devices have no effect, because the boom isn't caused by mechanical conduction between the cab and stage, it's caused by the resonance of the space beneath the floor/stage and room modes.

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

http://ethanwiner.com/speaker_isolation.htm

One potential fix is to lift the cab a meter or so off the floor, which works as an acoustical notch filter. A full parametric EQ works best, allowing you to dial out the boom frequency. If the cause is the stage it tends to be one frequency, as the space below has only one resonant frequency. High pass filters can tame the boom, but they also tame the frequencies  below the boom frequency, which tends to be in the 100-200Hz octave.

Since you don't hear the pops and clicks through the speaker chances are they're happening in frequencies too high for the speaker to reproduce them. It wouldn't have anything to do with the Class D power amp, as the sends come from before the power amp. You should be able to adjust the EQ on the recording desk channel strip to get rid of those offending frequencies.

21 minutes ago, Downunderwonder said:

If it's not loud enough for you to hear yourself properly you should try raising it up before doing anything else.

+1. At the very least it should be tilted back so that you can hear the mids.

Quote

A BF 4x10 is capable of being pretty loud.

Yep. Even if one added a BF 2x10 loaded with the same drivers the increase in maximum output would be only 3dB, which isn't worth the bother of hauling the second cab.

That's a logical arrangement if the upper driver is high passed and is a driver with specs optimized for a sealed enclosure, perhaps a guitar driver. But there are two other issues with that cab design that make me hesitant to assume how well it's engineered. The port area is too small for a pair of tens, while the horizontally placed tweeters should be splayed inward in a cross-firing arrangement, not splayed outward. That's not to say that it doesn't sound good, but it could probably be better.

Even 2x15 mains don't get boundary loading when up on a pole, so what a 2x15 on a pole is capable of with lows a 1x15 on the floor next to a wall will do. The #1 mistake made by PA newbies is tops that at too large, subs that are too small, or non-existent. A pair of 1x10 tops and 2x15 subs is a well balanced system.

5 hours ago, police squad said:

What about playing outside Bill. I do a couple of gigs each year, outside, no stage. I've been using the subs either side of the playing area with the top cabs on top of the subs.

From this I think the top cabs should be higher on separate stands, should the subs be at the side, next to each other (they can't go in the centre)

Outdoors is a challenge due to the lack of walls. Typically it takes twice as many subs to reach the same levels as indoors. Tops don't have that problem as being directional they don't use boundary loading. The subs don't need to be centered, off to the side is fine, but they still should be clustered unless the venue size is so large that they, and the tops, are spread by at least 14 meters or so.

Because of the need for boundary loading with bass subs are a must with no backline. I'm not familiar with your subs, but most subs of that sort are pretty much the same. I can't imagine using only one. Don't worry about center clustering, it's not necessary. Just put them together close to a wall wherever they'll fit. Sub output is omni-directional and the wavelengths are too long for them to be directionally located, so they can go anywhere. They don't even need to be aimed into the room. Aiming them at a wall can improve the low end loading and filter out above pass band harmonic distortion that you don't want to hear anyway.

I'm not the person to recommend new gear, though. The last time I used speakers not of my own design and making was around 1973.