Bill Fitzmaurice

There are no advantages or disadvantages. If you have am 8 ohm cab use the 8 ohm tap, if you have a 4 ohm cab use the 4 ohm tap. If you want to use two cabs then they'd have to both be 8 ohm, which when run together would go on the 4 ohm tap.

Mixed cab setups can sound fine. The question is whether or not a pair of mismatched cabs works better than a pair of matched cabs. The only way one can know that is to try A+B, A+A and B+B side by side. The sealed 4x8 may have better highs than the ported, but if it does it's not because it's sealed, it's because the drivers have better midrange response. Predicting if that's the case [i]should[/i] be a simple matter, you'd just look at the frequency response charts for the speakers. Unfortunately, manufacturers have a very low opinion of their customers, thinking them too daft to be able to make heads or tails of a frequency response chart, so they don't provide them.

What you'll end up with is a chain with a weak link. You may have seen it said that sealed cabs have more definition than ported. It's not true. Definition occurs in the midrange, and there's no difference in the response of sealed versus ported cabs in the mids. As for a 410 atop a 115, that's probably the worst possible cab configuration, nothing about it makes any sense.

[quote name='Lozz196' timestamp='1504387163' post='3364593'] On stage I don`t really notice the difference, but in a small rehearsal room I find rear-ported cabs seem a bit boomy [/quote]That has nothing to do with the port location. For the most part the reason cabs are rear ported is because there isn't room for them on the front. There isn't room because the cab is small. Small cabs tend to accentuate the midbass, which is the source of boom. Boom may be more noticeable in smaller rooms. [quote]What about side ported or bottom ported?[/quote]Radiation from ports is omni-directional. For that matter cone radiation in the lows and midbass is omni-directional as well. If you're able to stand behind behind your rig you'll notice that the highs are gone, and the midrange is muted, but the rest is unaffected.

[quote name='EBS_freak' timestamp='1504258093' post='3363682'] Bottom cab (assuming the impedance is the same) will get the same power as the top cab but its distributed between two speakers instead of 4. [/quote]If that's the case you want the 210 on top, so that you'll hear if it's distorting before the drivers are endangered. For equal power distribution the 410 impedance should be half that of the 210 impedance. However, in most cases they're both loaded with 8 ohm drivers, with the 410 impedance 8 ohms, the 210 impedance 4 ohms. The correct arrangement would be to have the 210 drivers series wired for 16 ohms, but that's seldom the case.

The symptoms are those of overheating.

The PJB wiring should be found in the owners manual.

What does the PJB show for connections?

Speakons can be wired more than one way. You have to make sure yours is wired correctly on both the amp and the speaker ends to function with the PJB.

On a technical note, the main reason why large PA systems use active (electronic) crossovers and multi-amping is they give much better protection to midrange and high frequency drivers than passive crossovers that use one amp to drive the entire audio range. Bass rigs don't need that kind of complexity. Dual-amping does make sense. The first time I heard it done was by Chris Squire on the first [i]Yes [/i]album. It took me 20 years to figure out how he got his tone, and then only because I read about it in an interview. You could never do it with a bass amp and pedal, because that affected the entire signal, not just above 100Hz or so with the guitar combo while leaving what was coming from the bass amp unaffected.

Bi-amping can work very well when done right, but where most bass rigs are concerned it's done wrong. The wrong way is using full range bass cabs for both amps. The right way is with an electronic crossover that sends the lows to a dedicated low frequency cab, say a 1x18 or 2x15, the mids and highs to a dedicated midrange/HF cab, loaded with six or eight inch midrange drivers. A variation is using a bass amp and bass cab for the lows and clean mids, a guitar combo for overdriven tones, but that's not bi-amping, it's dual amping.

[quote name='markstuk' timestamp='1503057017' post='3355356'] I feel a QI moment coming on [/quote]You have to bait a hook before you can set it. [quote]The issue is you cannot tell by just keeping the volume knob down.[/quote]+1. Besides, it's not power that trips protection circuits, it's current. You simply can't tell if you're pushing the current envelope until your amp shuts down. Having a big amp with lots of head room helps, but with today's typical puny power supplies you probably don't have as much headroom as the amp power spec would lead you to believe. Even if you really do have 10dB of headroom a hard transient can eat up that 10dB in a heartbeat.

[quote name='Happy Jack' timestamp='1503053982' post='3355335'] But with regard to all this, assuming that you're not driving your rig overly hard then does it actually "matter"? [/quote]It does. You may get away with too high an impedance load on a valve amp or too low an impedance load on an SS amp for brief periods but you still risk triggering the protection circuits of SS, and worse, damaging the output transformer and/or valves with a valve amp. [quote]I...never get anywhere near using half the power I have on tap[/quote]How do you know?

[quote name='Kevin Dean' timestamp='1502458939' post='3351636'] Greg Lake 20 plus cabs [/quote]I saw him some years back with 'only' two SVT cabs, and you couldn't hear a note from them anyway, it was all PA. Giant rigs are OK for impressing the kiddies, but that's about all they're good for.

Clamps aren't required. I use an external wood caul temporarily screwed to one panel to perfectly align the parts, isolated from the glue line with polyethylene sheet cut from a trash bag, with a few screws holding the joint secure until the adhesive sets. After the adhesive has cured all the screws are pulled, cauls removed, the screw holes filled with adhesive. Like so:

I wouldn't use either, both use too much material where it doesn't do anything useful. This picture compares typical 'window' bracing on the left with the better method on the right: The method on the right is more effective while using less material. I see you also have battens on the corner joints. They serve no purpose, other than adding dead weight, as that's the strongest part of the cabinet, requiring no reinforcement.

[quote name='geoff90guitar' timestamp='1500662124' post='3339518'] What blows a speaker then? [/quote]Too much power. The myth of under powering has as much basis in fact as the Yeti and The Honest Politician.

Distortion does no more harm to a bass driver than does water to a duck's back. Besides, the driver Bergantino uses has a mechanical limit around 200 watts.

I use felt specifically with very small cabs, where a thicker material won't fit well, as a half inch of felt is as effective as an inch and a half of foam or polyester batting. I never pay for felt, I get free scraps from carpet stores. Since it costs them money to have their scraps disposed of they happily give it away. There's no advantage to anything labeled as 'acoustic', other than to those who make and sell it, as that label enables them to charge more for it.

Most of the gigs I play can get away with not going through the PA, as far as the room goes, but I always run the guitar through it so I can hear him through the monitor. Small stages aren't a problem, they're why I designed small monitors. Besides, they have to be there to hear the vocals.

Read this. The same applies to bass cabs. http://www.prosoundweb.com/topics/sound_reinforcement/in_search_of_the_power_alley/ [quote]- neither the guitar or bass go through the PA.[/quote]They should, especially through the monitors, so that everyone can hear everyone else. You would high pass the bass so that nothing below 100Hz is in the monitors. With a stacked rig you can aim the bottom cab away from you to spread the mids and highs, but you'd usually aim it at the drummer, since he'd typically be beside, if not behind, your rig.

[quote name='Lozz196' timestamp='1499723480' post='3333220'] which is best for metal [/quote]Leather.

You can patch acrylic, you have to replace Tolex.

30 pounds.

It depends on how well it's braced. I specify 12mm in most of my designs, not for strength but for ease of construction, as most DIY builders would find jointing with less than 12mm difficult. However, if you've got the woodworking skills and the design is right you don't even need 9mm. My personal cab is a Jack 12 Lite, built from 3mm and 6mm.