stevie

7 hours ago, Obrienp said:

I wasn’t aware of that. I’ll have a look at them to see if the ports are different. I won’t be able to tell about the crossover, although I suppose I should be able to hear the difference. The horns look the same but that doesn’t necessarily mean they have the same compression model driver attached to them. It would be a bit too much hassle to remove the grills and take the drivers out to see if they are the same.

The port size was increased from 4" to 5" some time ago, while the lower crossover point is a recent development, made possible by the adoption of a more powerful compression driver. These are small, incremental improvements, which the average user is unlikely to notice. The sound of the cabs hasn't changed and the larger port will only make itself felt at extreme volumes. 

The changes from Silverstone to Silverstone II were enough to warrant renaming the cab. That's not the case with the Monza - or the Monaco for that matter, which has also benefited from incremental improvements over time.

The link doesn't work, @Phil Starr. I have some, limited experience of painting plastics, as I paint the ports on LFSys cabs. You can't apply normal paint directly; you need to use a special plastic primer. Fortunately, these are available for not much money at most DIY stores. A thin coating is fine. Once you've applied the (spray) primer, you can paint with whatever you like. An acrylic like Tuffcab is a good choice, as it dries quickly and doesn't give off nasty fumes.

I've not tried them myself, but there are a number of products available to fill chips and dents in ABS - the kind of thing the autobody guys use to fix bumpers.

Back to the matter in hand. As others have said, the OP not going to gain anything in terms of performance by swapping the QSCs for any of the cabs mentioned. As far as I can gather, the MK1 K12 used off-the-shelf Celestion drivers which are still available. So, as long as the amp doesn't give out, they have many years left in them.

If they were mine, I'd be tempted to refurbish them. A can of satin black paint will work wonders on the grilles, for example. 

13 hours ago, Jackroadkill said:

 I have the mesh grille and all the fixings, but the one 15" speaker I have won't fit in the hole in the baffle, annoyingly.  I'm not sure at present whether this is because the speaker's chassis is too big or the hole is undersized; I suspect some research may well be due.

 

Does your driver have a cast aluminium chassis? Drivers with a cast chassis tend to be larger in diameter than those with a pressed steel chassis. So, a replacement driver with a pressed steel chassis might fit. Check out the specs provided by the driver manufacturers, where the precise diameter is usually stated.

Please don't expect loads of reviews yet. The first Goodwood has gone out to a customer who has promised to report back, and some beta testers have tried the cabs and will no doubt chime in when they're ready. But shipping won't start in earnest for a month or so.

49 minutes ago, Al Krow said:

 

V. helpful A/B based on the spec sheets, although I guess the proof of the sound has got to be in the hearing?

 

Not sure about the power ratings you've suggested though - the 912A's are stated to be:

LOW FREQUENCIES: 1400 W Peak

HIGH FREQUENCIES: 700 W Peak

 

Which I reckon should translate to 700 + 350 = 1050W RMS per speaker, which is decent?

 

How rugged is plywood typically vs toughened plastic?

 

What matters for power handling is not what the amps are rated at, but what the drivers will take. Both the RCF and FBT drivers have 2.5-inch coils, which limits them to around 300 watts at most. Although some high-end components will handle more, a good 1.75" voice coil compression driver will handle about 50 watts. So, the 700W peak rating for high frequencies is, shall we say, optimistic.

I wouldn't say there's any difference in the roadworthiness of plastic and plywood cabs. What bothers me about plastic cabs is the sound. I appreciate I may be more sensitive than most to this because plenty of people on here are happy with their plastic cabs - and they sell by the bucketload.😀

I've had a look at the published specs of the RCF 912 and the FBT and they're fairly similar. Both bass drivers have 2.5" coils - so they're what you'd call 300W cabs in a non-hyped world. The RCF has a pressed steel chassis and ceramic magnet and I reckon the FBT is the same - otherwise they would mention it. This is budget PA, not high-end.

The FBT compression driver has a 1.4" coil, while the RCF has a 1.75" coil, which puts the RCF ahead on points. However, the horn is likely to make more of a difference than the HF units. RCF horns are normally excellent; I can't comment on the FBT horn, as I can't find any photos.

The kicker for me is that the FBT has a plywood cabinet, as @Phil Starr has pointed out. I can't stand the "boxy" sound of plastic cabs personally.

It looks like they're close. Price and weight are similar. The five-year warranty is another plus point for the FBT. I can't see any downsides for either cabs at the price, although the proof is always in the pudding.

The Seymour Duncan Convertible combo had the option of a solid state or tube rectifier, which may be what you remember, @Dood

49 minutes ago, Phil Starr said:

 

If you are combining two tweetered cabs then it is better to stack them vertically with the tweeters as close together as possible, so  as you say horn>woofer>horn>woofer is not good. There are two approaches, simply invert the top speaker so the horn is now on the bottom and in some cabs very close to the horn on the bottom cab, this approximates to a D'Appolito configuration giving a fairly coherent wavefront but you'll get some phase issues in the vertical plane due to the spacing between the horns.  You've now moved the two mid bass drivers further apart so you'll lower the point where the mids become directional and start beaming so this works best in speakers where the crossover is lower like the LFSys. Radiation in the horizontal plane should be good and a lot beter than a side by side arrangement.

The second method is to stack the speakers but on their sides with woofer above woofer and horn above horn in a classic line array. The problem with this is that the horns are on their side and typically they are designed to radiate a wide horizontal beam which will now be narrow and high. The audence may hear less detail in the bass guitar if they are off axis but the player will benefit from the extra height which will be giving more upper mids to their ears. If you were doing this regularly then you could rotate the horns. LFSys have the horns rotated already though to direct the mids to the bassists ears whilst in the conventional position.

 

Sometimes I bore myself

This is a very good summary of the stacking options available. Classic theory tells us that you should keep drivers as close together as possible, especially when they are reproducing the same frequencies. However, I suspect that a lot of players might be more concerned about having the grille badge sideways or upside-down when using one of these configurations.

Although normal vertical stacking of tweetered cabs isn't ideal because of comb filtering, it doesn't seem to be a problem in practice as long as the cabs are tonally similar.

16 hours ago, Ed_S said:

 

That's fair, I can see how that'd work from an engineering standpoint. I guess 'inferior' is a poor choice of word without a good deal more qualification, isn't it. Better to simply say I personally don't like them for a number of reasons, both practical and aesthetic, and much prefer my cabs to have metal corners and rubber feet.

 

Is your preference for the plastic all-in-ones such that you'd actively avoid metal/rubber?

My overall preference is for the plastic ones because they offer more protection for the corners and allow for easy stacking (in both portrait and landscape formats). There are some horrible plastic ones which look cheap, but I think the small, chevron types can look very smart. To answer your question, @Ed_S, I certainly wouldn't avoid metal corners and rubber feet, and I can understand your preference.

5 hours ago, Ed_S said:

Can only speak for myself, of course, but I think plastic stacking corners will always be a massively inferior solution to metal corners that don't break and rubber feet that give significant ground clearance.

Modern plastic feet/corners are quite tough, but subjected to enough force, they will crack. What may not be immediately obvious is that, by deforming, they act like a crumple zone to protect the cabinet corner - and they're cheap and easy to replace. Because they're more rigid, metal corners  transmit most of the force through to the corner.

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No problem at all acoustically, although you'll need to find a way of stopping your amp from falling off the top of the cab.

5 hours ago, Bill Fitzmaurice said:

Because the average horn loaded high frequency driver has 10dB higher sensitivity than the average woofer attenuation by one means or another is a necessity. It can be with a variable LPad, or with a fixed value LPad, or with DSP. Yes, the bass and preamp can reduce the treble, but their frequency passbands don't necessarily line up with that of the tweeter. Besides, there's nothing wrong with tweeter attenuation, we've been doing it for a hundred years, so why not?

John's not suggesting running high frequency drivers without any attentuation (obviously!). He's questioning the point of having an L-pad attenuator in the system at all. I had a three-way bass cab at one time with L-pads on the midrange driver and tweeter. I couldn't for the life of me figure out the best setting by ear and had to carry out measurements to find out what was happening. I ended up with something like twenty-to on the mids and quarter past on the HF. Many people assume that 12 o'clock is flat, but it rarely is.

IMO, the best solution is for the manufacturer to set a fixed attentuation level that balances the bass/mid and HF.

The Veyron is very good and exceptional value for money. Performance is in line with the popular lightweight heads from Markbass, Aguilar, Ashdown etc., all of which I've owned. I've no direct experience of EBS or Eich, but if you're using it as a backup, you can't go wrong.

Yes. I did a bit of digging and that's what I found for the 1516.

Oops! Sorry, @SimonK. My mistake.

You can't go wrong with either SB Acoustics or Scan-Speak.

As stated elsewhere, the clue that the seller doesn't know what they're doing lies in the inadequately sized port.

If the OP just wants four Trace 10-inch drivers, there's a set currently on Ebay for £60.

3 hours ago, Bill Fitzmaurice said:

You're getting all the width to the sound field as is possible already. The midrange drivers insure that the upper woofer doesn't go high enough to get beaming from it, bi-amping insures that the lower woofer doesn't go high enough to get beaming from it, and having the midranges vertical insures the widest possible dispersion from them. Plus the tweeter takes over where the midranges start to droop off-axis. The tweeter in the lower box should be shut off.

This is absolutely right - but only if the manufacturer has implemented the crossover properly so that each driver is operating in its own frequency band. I don't know for sure, but I believe all the drivers are run full range except for the tweeter.

On 10/03/2025 at 18:00, Chienmortbb said:

Aluminium dust cap was used in the late 60s by Fane on the original crescendo drivers and it did indeed extend the response considerably. 

Are you sure it extended the frequency response, or could it have just induced peaking, which might have sounded like it did?

On 13/03/2025 at 08:10, bremen said:

Excellent piece, Phil.

 

Here's how Tannoy attempt to reduce cone breakup:

It's probably a similar idea to what Scan-Speak have done with their slit cones, where they slice the paper cones and glue them back together again to control cone resonance. Here's the reponse of one of their seven-inch drivers showing how they've controlled serious cone break up until about 5kHz. Notice how smooth the off-axis response is right up to 7kHz.

It depends how you want to define it, @bremen. I think of it as a supplementary cone made of lighter weight material that's attached to the cone. They've fallen out of favour nowadays, as cheap whizzers are highly resonant, and there are better alternatives, i.e. coaxial drivers.

@Phil Starr is probably the person to explain this in a way that doesn't have you reaching for your dictionary. He'll probably be along soon. However, @Chienmortbb is right to say that the fall off in higher frequencies off axis is worse on a large diameter driver than a small one.

I'm fascinated to hear how you can extend the off-axis rolloff by an octave by manipulating the cone and dustcap, as I've never seen this in real life. A wizzer cone is a bit different, as it is a separate transducer attached to the voice coil.