paulbuzz

With your proposed smaller port area and lower tuning, I see that the port velocity becomes very high at low frequencies. Also, with your lower tuning, if you go to the 'maximum power' item on the pulldown, you can see that there's a big dip in the power handling centred at 67Hz. Raising the cab tuning reduces this dip, whilst also reducing the port length required, but also increasingly producing a hump in the frequency response just above the cutoff frequency. So it's all a question of compromise! I'd be inclined to stick to the full width port (in order to keep the port velocity as low as possible). I'd probably start by initially making the port length nearly as long as you can before it starts reducing the port area by getting too close to the back of the cab. (So maybe reaching up to about 80mm from the inner rear wall of the cab?) Then tweak the tuning (port length) to get a satisfactory combination of frequency response (transfer function), port velocity, and maximum spl/power. And create a WinISD model of your existing Ashdown-combo-based setup for side-by-side performance comparison!

Your port will effectively start from the front of the baffle, so the thickness of the baffle is included in the overall port length. So for calculating the depth of the 'shelf' you'll add to give length to the port, yes, you would want to subtract the baffle thickness. If you reduce the cross-sectional area of the port, this will increase the velocity of the air moving in the port. If the port air velocity gets too high, it creates an audible effect known as 'chuffing'. The port air speed is modelled in WinISD, which you can see by going to the item 'Rear port - air velocity' in the pulldown menu. (The menu item that you currently have set to 'transfer function magnitude'). [ Since this only applies at higher amplifier powers, to see the correct port velocity you will need to set 'system input power' in the 'signal' section of WinISD to something like the max output power of your amp. ] Unhelpfully, opinions differ (as ever!) as to what a maximum acceptable port velocity is. Unfortunately I can't currently remember what sort of figures are regarded as ok! You might need to get input from someone more well-versed in these matters - eg Bill Fitzmaurice or Balcro or Phil Starr... fortunately this forum is filled with people more knowledgable and less gormless than me...! 😁

Yep, when initially setting up your WinISD project, the tuning frequency gets pre-set to create the default QB3 Quasi-butterworth alignment you mentioned in your original post. This represents tuning the cab to the lowest possible frequency with a smooth response before it starts rolling off. This is often a desirable cab tuning, but is certainly not the only possible choice - you might choose a different tuning for a different-but-lumpier bass response, or for increased power handling, or for other reasons - such as because you can't fit the optimal port into your cab...!

Ah, looking at your pics again, I see now that it seems the existing port has no 'length' as such - so just the thickness of the baffle... 18mm? So as SubSimp has suggested, you can create length in the port by fixing a shelf on top of the existing port braces; this could be any length you like, up to the limit imposed by the depth of the cab itself. (You obviously shouldn't bring it so close to the back of the cab that it restricts the area of the port!) As I posted above, you can model the results for any given port length by adjusting the box tuning frequency until you match your proposed port length.

If, in WinISD's 'Box' tab, you tweak the tuning frequency of the box, it will automatically alter the length of the suggested port. By trial and error, you could set this to match the length of the existing port of the box, and will then be able to see how much this has affected the properties of your cab - you may find that the results are acceptable without any port retuning being required! You could also use WinISD to model your existing setup with the Ashdown combo cab; then you would be able to see what differences you can expect from the TL606 box - or maybe you've done this already...?

Ok, just for fun and discussion, here's my proposition: The last hundred years (or thereabouts) of popular musical styles have been driven and guided by developments in amplification. Disclaimer: I'm certainly not claiming that any of this is original thought; I'm just putting it together in this form here for the fun of getting other people's thoughts and input on these ideas. It's entirely likely that, to paraphrase somebody or other, anything here that's true is probably not original, and anything that's original is probably not true... 😉 So anyway...: Before amplification was widely used in popular music, singers had to be loud to be heard. Various stylised foms of singing were developed that allowed for maximum volume; music hall, light opera, blues shouters, etc. When microphones and early amplification became available, vocalists were able sing much more quietly and naturalistically whilst still being audible over the band; hence the crooners and their intimate stylings. Now it was guitarists who were struggling for audibility against the blare of the big band, so following the lead of early adopters such as Charlie Christian, the guitar amplifier became popular. This allowed for the development of 'lead guitar', and onwards to small groups using guitars as the main instrumentation. Loud singing again frequently became necessary to compete with the rising beat of rock'n'roll... Guitarists increasingly found that there was something special and exciting about the distorted sound of a guitar amplifier pushed beyond its design limits. They experimented with larger and larger amplifiers, and new music arose based on those sounds, with Jimi Hendrix as its most visible pioneer. Now it was singers who were struggling again: trying to make vocals audible over the din of massive overdriven guitar stacks was a task largely beyond the capabilities of early 1970s vocal PAs. Singers were back to howling at maximum volume in an attempt to be heard; eg Robert Plant and the behemoths of 1970s heavy rock. This spurred great developments in PA systems, allowing much greater overall volume, and crucially, with the advent of effective subs and high powered amps, previously unthinkable levels of bass frequencies. This new capability led to the rise of bass-powered dance music in its many forms, from reggae through rave, d'n'b, dubstep and the panoply of other bass-driven styles that have dominated popular music until today. So... anyone for any elaboration, correction, rebuttal or just plain contradiction...? 😁

This pedal is a clone of the Tech21 Character Series 'Blonde' pedal, and thus a close relative of their VT Bass pedal which is of course widely known and well-loved around here. As a guitar pedal it's almost miraculously good for the dirt-cheap price. I can imagine it would work perfectly well as a bass pedal, though I haven't tried it myself. I think it gets a little noisy only if the character/'voice' knob is cranked very high; though this gives much higher gain too, so is perhaps inevitable. I do feel a bit guilty about the sales that Tech21 lose to these clone products after their work in developing the excellent originals, but there's really no point in rehashing the 'ethics-of-cloning' arguments yet again...

I took a different message from the article Bill, which I found interesting rather than reactionary. I felt that the author's main gripe was that following the widespread availability and installation of super-powerful subs in mainstream venues, the freshly-discovered option of creating very low frequencies at very high levels has encouraged sound-people to do just that, regardless of whether it's appropriate or not. This applied strongly to the author's acoustic duo, but I would say that it is also very much in line with my experience of the sound at rock music shows over the last several years, a number of which have been ruined for me by massive sub-bass levels swamping the rest of the music. This seems very annoying and completely unjustifiable to me, but I hope that I'm discerning rather than reactionary!

Fair enough, although I'd be surprised if your RCF745 can bang out the same volume levels as your EBS 4x10! (I could be wrong though - I haven't tried an RCF745!)

Dunno how old you are Al, but speaking from my own position of rapidly advancing decrepitude, hearing anything above 15 kHz is just a distant memory! 🤪

For me, the most convincing argument in favour of using a FRFR speaker (either active or passive) is that it makes it much easier to be sure that you're sending the right signal to the PA soundman. If your speaker has a pretty flat response, like (hopefully!) the PA system, then you can just tap off a DI signal to send to the PA, and know that that tone, amplified through the PA, should pretty much match the sound coming out of your on-stage gear. If not (ie your bass speaker is significantly coloured, like most speakers used for bass rigs), then you will previously have adjusted your amp EQ etc to sound good through your rig's speaker, compensating for its idiosyncracies. So how are you going to get the right signal to the PA? If you take a DI signal before your speaker, then it won't include whatever colouration your speaker is bringing to the party. If, for example, you have a tweeter-free cab and are using any overdrive/distortion effects, this is likely to sound dreadful when DI'd into the PA. So perhaps you'll mike the cab? Even if the soundman is willing (and they're often not keen...) he will need to take account of the huge bass boost caused by the proximity effect of the mic jammed up against your cab. Is the soundman on top of this? And, oh, does your bass cab have a tweeter? Perhaps even a separate mid-range driver?! Mike them up separately, you say? Good luck with that! A disadvantage of the FRFR approach is that a speaker that can produce high quality, clean, full range sound at volume levels equivalent to a traditional bass rig is a probably a much more expensive item than a decent traditional bass speaker. For this reason, amongst others, I have always stuck to the traditional route of using a normal kinda bass rig, sending a DI signal off to the PA, crossing my fingers and hoping/trusting that the soundman is sufficiently on top of the task to make something useful out of it! If you've applied a bit of sense to it this approach usually works out ok - after all, it's what pretty much everybody always did until recently...

Thanks for that Bill; it's getting weirder and weirder - we've moved on from American Football metaphors to dog fighting metaphors! I had a much better idea what was going on when we were just talking about speakers... 😜

Since I don't understand a single word of this, I don't have the faintest idea whether this is a wildly off-topic digression or part of an extended metaphor being deployed in an argument about driver sizes... 😁

I used to use this kind of a setup many years ago when I was young/strong/foolish enough to want to carry it around. It sounded great, so I fully endorse and encourage your plan! My setup used a Trace Elliot GP11 Mk4 Preamp as its front end, which had a built-in crossover with outputs which split the signal at 250 Hz. The high end went to a Marshall valve head driving a 2x10", and the low end went to a solid-state power amp driving two 1x15"s. The Trace preamp was a brilliant piece of gear - great sounding and ultra-reliable. They come up for sale fairly frequently and really cheap. Alternatively there are HPF pedals available such as this one from Broughton, who seem to be well-regarded: https://www.broughtonaudio.com/product-page/high-pass-filter But I think you can feel free to have a go at just cutting out the bass from the high-end side using the tone controls on the amp. Your ears will tell you if the cab is struggling. Good luck with your rig experiments - it's sure to be lots of fun!

If you're doing gigs with a PA that just has active 10" speakers and feel that the kick drum and bass guitar could do with a bit of a lift, I'd say that was an ideal set up to which to add one or two active subs. (I wouldn't even consider putting kick drum or bass into a PA that's just a pair of 10"s.) Were you intending to mic up any of the rest of the kit? If you think it's just the kick that's getting a bit lost, in my opinion it would be fine to add a bit of reinforcement to the kick drum only, but others would argue that if you're going to mic the kick, you really ought to add overhead and snare mics too as a minimum. At this point though, you're starting to add quite a bit of extra gear and complexity to your setup and soundcheck. There are loads of models of subs that are intended for exactly your kind of setup, at widely varying price points. I'll leave the recommendation of specific models to those that are more familiar with the currently available models...

Agree absolutely. Your anecdote about Greg Lake's bass sound is distressingly familiar. I don't know what's wrong with the people responsible for these mixes. It's as if they've somehow become persuaded that the spectral balance of electronic dance music is appropriate for all other forms of music too. Or is it just complying with what they think people expect from the sound at live gigs these days? Either way, it seems to have become a very common aesthetic for live sound mixes, with hugely detrimental effects on the entire mix, and the bass guitar in particular. Apologies to Al if I'm getting a bit off-topic here.

I think that in most cases the kick drum is the primary factor in determining whether your PA needs a sub or not. - Is the band attempting to perform at a volume at which the kick drum, unmiked, would be too quiet? YES: The PA needs a sub, and both the kick drum and the bass guitar should be in the PA's FOH mix. Hence no point in a bass backline sub. NO: The PA doesn't need a sub (and neither does the bass backline). I'm not up-to-date enough with currently available PA gear to have any meaningful opinion on which are the best value subs at various price/performance points.

Most bass backline equipment is pretty poor at reproducing the lowest frequencies, certainly at higher sound levels, so I think it's perfectly reasonable to wonder, as Al is doing, whether incorporating a subwoofer into your backline might be a good idea. The way I've always viewed it, though, is that if you're in a situation where you feel the bass guitar needs some subwoofer support, then it's almost certainly true that the kick drum does too. At this point it becomes a PA issue rather than a backline issue - ie your PA system needs a subwoofer, and if it's got one, then there's no benefit in also adding one to your backline. Also, as Bill points out, excess sub-bass frequencies are frequently a huge problem in contemporary live sound mixes. WWWWWWOOOOOOOOOOOOOOOOOOOOOOMMMMM! 😡

If you haven't already, I should think you almost certainly need to remove their nuts from the sides of the case...

You didn't mention the input/output sockets, but I imagine they're probably fixed to the board and attaching it to the case too...?

Another suggestion: the TC Rush Booster from their 'Smorgasbord of Tone' range. I really like the form factor of these pedals: since all the sockets are on the far end, they actually take up about the same width on your pedalboard as the usual 'mini' pedals (with right-angled jacks sticking out of each side), but are more stable because the box itself is wider. The Rush Booster is very simple: a single 'boost' control with up to 20dB of clean boost. Also very cheap: currently about £29 at all the usual big online shops. I haven't got one, but online reviews seem to be good. If what you want is purely a clean boost, there's perhaps less subjective judgement required than is the case with most other types of pedal?

Bill and Balcro: firstly, thanks very much for your carefully considered replies. Apologies for my slow response; I've been a bit tied up with other things, you know how it is...! Bill: Thanks, I did get as far as wondering what the published frequency response for drivers represented - when you say 'mounted in a wall', I guess this is what's referred to as an 'infinite baffle'? I'm imagining that this is essentially the same as an infinitely large sealed cabinet...? Re. needing sufficient amp power in order to benefit from a higher xmax: as discussed in the older part of the thread, I'm pretty certain that the currently installed (original) driver is this one: http://www.elderaudio.com/products/Loudspeakers/LowMiddle/2009/10LB075-U.html Having fiddled with this in WinISD, as far as I can tell with my sketchy understanding, this can't take the amp's full rated output (250W @ 8 ohms) at frequencies below 200Hz, and its handling falls to about 50W around 120Hz, so in this area presumably any of my three potential replacement drivers would be a significant improvement. I completely accept your point that earth-shaking bass is never going to come out of such a tiny cabinet! Balcro: Thanks again for doing all this calculating! In short, it seems that any of these three drivers would be an improvement on the original, and that the differences between the three would be comparatively minor... Re. weight: current driver is 5 kg; the potential replacements vary from 2.1kg to 2.7 kg, so potential saving of up to 2.9 kg - this could be quite worthwhile! In the end I guess whether the available improvements over the current driver are sufficient to justify the outlay is something of a moot point. So overall I'm still in two minds. Thanks again for all your input; if I finally do get a replacement I'll let you know how successful a change it is! 🙂 cheers, P