Bill Fitzmaurice

[quote name='SingleMalt' timestamp='1421272034' post='2659333'] Both have [b]stupid [/b]amounts of hum when the volume or gain are turned up. This is true with no bass plugged in at all [/quote]That's a defect. With no bass plugged in the input is shorted and any noise is self-generated.

[quote name='taunton-hobbit' timestamp='1421423388' post='2661058'] you will never hear the full break-in change with one of our cabs. [/quote]You'll never hear it with anyone's cabs, the change is too subtle and your ears are too insensitive to hear it. For that reason you'll see legions of those who deny that it happens at all, though none of them have ever measured the changes, which really do occur.

[quote name='Twincam' timestamp='1421237551' post='2658711'] A Jack Russell pissed through the grill onto the speaker. [/quote]You're lucky it wasn't a Great Dane.

There are two ways to choose a correct replacement driver. One is to find the T/S specs and frequency response of the original and match it. Since speaker companies won't divulge that information you'd have to measure those items yourself, which requires specialized gear and knowledge. The other is to reverse engineer the cab, using speaker modeling software to find that driver specs that will work best in it. That also calls for a high degree of knowledge. Option three, which is what you should probably do, is to sell your amp and buy one that meets your needs.

[quote name='1970' timestamp='1421153035' post='2657666'] One thing I've found useful lately is recording directly out of my GT200 DI output - would I be able to do the same thing out of the preamp/slave output in an OR120? [/quote]Yes, but only into a line level input. It would overload mic level.

[quote name='Dad3353' timestamp='1420642229' post='2651649'] there are many that use this mix with (apparent...) satisfaction. [/quote]That goes to a basic acoustical engineering tenet, which is that almost [i]any[/i] two cabs together will sound better than either one alone. Knowing what combination of cabs actually works best requires being able to test every permutation side by side, for instance, a stacked pair of 1x15, a stacked pair of 4x10, and a stacked 1x15/4x10. I've yet to see anyone report ever having actually done so. [quote]It's generally accepted these days that there is no direct correlation between the speaker diameter and its bass capacity. [/quote]There has not been since circa 1980.

[quote name='chrisasp' timestamp='1420639233' post='2651611'] Im wanting to buy the hartke 410bxl (400 watt at 8ohm) and the 115 bxl (200 watt at 8ohm). [/quote]Reconsider. First, a 1x15 doesn't go appreciably lower, if at all, than a 4x10, and it won't go as loud as a 4x10, so you don't gain anything, while half the power goes to the 115, even though it has only half the capacity of the 4x10. IMO the only worse configuration than the 4x10 is the pairing of a 4x10 with a 1x15. You should consider either a pair of 1x15 stacked vertically or a pair of 2x10 or 2x12 aligned vertically.

[quote name='6v6' timestamp='1420584883' post='2651086'] Ok, thanks all, trial and error I can do just wasn't sure if there was a more scientific method I could be applying. [/quote]There is, but it's way beyond an amateurs skill set.

Close your eyes, turn the knobs, wherever they sound best is where they should be. The numbers don't mean a thing.

Mixing cabs can work well, and it can be horrid. The problem is that it's difficult for even an expert to predict it in advance. With identical cabs you know what you're going to get.

[quote name='RJB280' timestamp='1420362623' post='2648332'] Thanks Bill, I understand where you are coming from ref drivers but surely the design of the enclosure would have a large part to play ? Ported versus sealed etc ? [/quote]Yes, but that has nothing to do with transient response, which is primarily seen above 500Hz, whereas the effects of the cabinet are primarily seen below 200Hz. [quote]making the cab a bit too small gives a bump in the low mids, which may or may not be a good thing depending on your preference[/quote] The effect of a too small cab is usually seen between 80-160Hz, which is technically midbass. A hump there is usually heard as 'boom'. It's pretty much the typical sound of inexpensive combos.

[quote name='Dan Dare' timestamp='1420322324' post='2648147'] Looking at the original question, I wonder if amp clipping may be to blame. Most combos will struggle once the master volume goes over the half way mark. [/quote]Perhaps, but it's a crapshoot with combos which will run out first, the amp headroom or the driver xmax. It's not unusual for combo drivers to run out of excursion capability with even 40 watts input.

There's precious little difference in the transient response of most electric bass drivers, even irrespective of size. Transient response is mainly limited by the driver voice coil inductance, T/S spec Le, which tends to be very low with most drivers. Those which do have high Le tend to be subwoofer drivers, where transient response is a non-issue anyway.

[quote name='Dan Dare' timestamp='1420317810' post='2648083'] A flat sheet of solid foam (especially hard foam) will, at least in part, reflect sound waves back at the cone [/quote]True, hard foam will do so. Acoustical foam isn't hard. Acoustical foam does have reflective properties where the wavelengths are short compared to the solid bits of the material that make up the foam matrix, but those wavelengths are far shorter than those produced by woofers. Even at 4kHz a wavelength is better than 3 inches/85mm.

[quote name='taunton-hobbit' timestamp='1420294424' post='2647651'] That'll be back to carpet felt underlay then............. [/quote]Felt underlay works well. On this side of the pond you can't find all you want for free if you're not adverse to dumpster diving for scraps at a carpet store.

[quote name='Dan Dare' timestamp='1420291390' post='2647566'] It ain't cheap, but proper contoured acoustic foam is best. [/quote]Actually, it isn't. The main benefit of the contouring of acoustic foam is visual. It looks like it should work better than plain foam, but it doesn't. Compared to an equal thickness of plain foam acoustical foam is a lot less foam, a lot more air, and air has no damping properties. The reason acoustical foam is made that way is to make it resemble diffraction grids, which serve a totally different purpose than damping foam. It's often called 'eggcrate foam', and in fact decades ago recording studios really were lined with pulp eggcrates. It's often assumed their purpose was damping or soundproofing, but their actual function was to scatter reflected waves. That's not what one wants to do inside a speaker enclosure. When the change was made in studios from low tech egg crates to high tech foam the shape of the crates was retained, but not the function, as foam doesn't scatter reflected waves the way that solid pulp does.

[quote name='Mr.T' timestamp='1420193488' post='2646462'] We are happy with the sound of our singer's Mackie SRM650's [/quote]Obviously, as you would have ditched them already were that not the case. That's where getting user recommendations is dodgy, because most people will recommend what they have, and who is going to keep something that they don't like?

[quote name='Lord Sausage' timestamp='1420037998' post='2645065'] Who is right? [/quote]Both and neither. Hi and low may refer to the output level of the instrument, usually active versus passive, but it also may refer to the gain applied to that input by the amp, hi gain for passives, low gain for actives. As a method of last resort, and at the risk of having your Man Card revoked, you might consider looking at your amp manual to find out which applies to your amp. Nah...

[quote name='DiMarco' timestamp='1419923660' post='2643931'] Bill, with the larger xmax but smaller surface area, isn't the 12" pushing less air harder and because of that having a radically different dispersion? Just wondering in which aspects (if any) this makes the smaller speaker behave in relation to room acoustics. [/quote]Twelves do have different dispersion than fifteens, it's wider, and that's better.

[quote name='DiMarco' timestamp='1419885381' post='2643659'] But the fact is the speaker surface is only about two thirds of that of a 4x10 and even less then that of a 2x15 [/quote]Moot. Speaker surface is only two dimensions. The third dimension is excursion, xmax, and that, combined with the surface area, Sd, gives you the all important spec: Displacement, Vd. The bad news is that most commercial cabs don't reveal the Vd of the drivers used, so you have no basis for comparison between them. If you can find out what drivers are used you can look up the Vd on the driver manufacturer spec sheets, but speaker manufacturers aren't forthcoming about the drivers that they employ either. For the most part that means having to try before you buy, to be sure that what you're considering meets your needs.

[quote name='Mr.T' timestamp='1419880594' post='2643580'] Am I missing the point of active speaker cabs? [/quote]They appeal to newbies, as they appear to be easier to set up and work with than separates. They're not. If anything they make setup more of a chore, requiring both a signal cable and a mains cable to each cab, as opposed to a speaker cable from an amp. A few years ago I went from a separate mixer/power amp rack to a powered mixer, as it has built in effects and EQ and four 400w amps in a 40kg package.

Ditch the fifteens. If you're only running vocals there's no need for them, and for that matter if running a full mix there's still no need for them, as you'd need subs for the lows anyway. I don't have any experience myself with self powered plastic PAs but from what I hear Mackie are among the worst of the lot, while RCF and QSC are among the best.

An undamped cab is a defective cab. There's no justification for any manufacturer saving two or three quid by not using damping, other than that they just don't give a flying f..k how it sounds, and telling the consumer "if you want a better amp, spend more money". But as for damping taming midbass boom, it won't. Midbass boom is caused by inexpensive drivers and/or a cab that's too small for them.

[quote name='Jus Lukin' timestamp='1419337086' post='2638840'] does the simultaneous cone movement equate to a 4mm Xmax in relation to the same signal? [/quote]It does.What you're really comparing is displacement, T/S spec Vd. If you use a single driver with 4mm xmax or four drivers with 1mm xmax the resulting system Vd, and therefore system displacement limited output, is the same.

[quote name='SingleMalt' timestamp='1419190353' post='2637444'] Pretty cool buying valves made in the 70s for the Russian Military.... [/quote]They probably were the best ever made, having to stand up to battle conditions. They kept valves long after everyone else, not only because they lacked the SS technology, but also because valves are immune to EMP.