stevie

There's no standard formula for crossovers done properly. I've published quite a few on here and they've all been completely different. You have to use the components and circuits that work for the particular drivers and cabinet you're working with. It's like making a bespoke suit or designing a website. However, like most things in life, it's possible to bodge. The 2nd order LP and third order HP is based on the idea that you don't want two lossy inductors in the path to the woofer if you can help it, and you need to use a fast rolloff to protect the tweeter. There's a lot more to it than that.

1mm or 1.2 mm for the bass inductor. .7 or .8mm for the .5mH value and .6mm for the 1.1mH value inductor, although thicker wire won't do any harm if your choice is limited. Resistors should ideally be 20W. I'd also double up on the resistors in the LF circuit, i.e. 2 x 2.2 ohms for extra power handling. Don't bother with esoteric capacitors. They're a waste of money IMO. But do use film type caps and not electrolytics.

Inset handles are a good idea, as that existing handle makes it awkward to put an amp on top. I don't understand why you'd want one on the bottom though. You can indeed fit bracing retrospectively as Phil suggests, although you'll probably not need quite as much as in the Basschat design because you're working with heavier and thicker material. A central figure 8 brace is always a good idea to start with. Then it's suck it and see. I suspect you'll need a vertical brace on the back panel behind the driver and a vertical brace between the horn and the port on the baffle.

I'd advise against using carpet inside the cab. It's relatively heavy and not very effective. Carpet felt underlay is good - I use that for some things - or the usual BAF wadding, which is the kind of thing you find in duvets or sleeping bags. Don't put any within about six inches or so of the port. Looking good so far!

There are plenty of examples of commercial speakers that use a driver's natural rolloff as part of a crossover. I'd mention the Spendor BC1 as just one example. That used the natural rolloff of the Celestion HF1300 to *cross it over* to a Coles supertweeter. It wasn't very elegant, but it worked. As far as bass cabs are concerned, using a properly designed two-way crossover is a much better solution, but nobody does it because it costs money and doesn't add to the perceived value of the product for the average punter.

You can indeed buy ready-made crossovers but I'd compare them to having your hair cut with a pudding bowl. Yes, it's a haircut and some people might even like it - but nobody's should believe it's a proper haircut. A 'proper' crossover needs to be designed for the drivers (and cabinet) being used. Unfortunately, just about every bass guitar cab I've seen has a minimalist crossover like the one @Killed_by_Death showed earlier - because it's cheap and nobody seems to care anyway. The impedance the amp sees is a combination of the crossover and the driver. If you'd like a solution that's been tested and documented on this very forum, check out the Lockdown cab build thread. There, you'll find an inexpensive but very good compression driver/horn combination along with a cheap-to-build crossover that was originally designed for use with a Celestion 10 but won't be a million miles out if used with another bass driver.

Very good question. The answer is that you're quite likely to have impedance issues unless you know what you're doing. Here's an example of a commercial cab with serious problems in this area. It's not the first one I've seen either.

@Jolltax, .13mH will be OK.

I see Phil's answered your questions comprehensively. To save drilling holes (or using clamps) when you're assembling your cab, get yourself some self-drilling screws like those made by Reisser and others. Once the glue's dried, you can unscrew them if they're a bit close to an outside edge or if you'd like to reuse them. A matchstick (with wood glue) is about the right size to fill the holes. Then dab on some wood filler and sand flat.

It doesn't get much cheesier than this.

Interesting suggestion. If the cab originally had a port where the piezo currently is, that would explain a few things. Ashdown's literature says: "Handmade in the UK, Ashdown introduces the ABM-NEO-210 Combo and NEO-115 combo and now a C110 1 x 10 combo, both the 210 and 115 are fitted with Ashdown high-frequency horns and custom Italian Sica Neodymium drivers..." No mention of a tweeter on the 1x10. Unless they thought it best not to mention the piezo. The plot thickens. I can't find any photos of the cab with the grille off, but there are descriptions of the combo elsewhere on the internet that claim it has a horn. Mind you, that's all academic. Fitting a port to the cab will certainly improve its performance. And that's what matters to the OP.

I have to agree with the OP that cheap compressors are not up to much. I advanced from in-amp compression to a cheap Behringer then to a mid-priced Boss (forgotten the name) and didn't find either of them very useful. It was only when I got myself a Seymour Duncan Double Back VCA-based compressor that I was able to get the kind of 'thunk' I was looking for.

I've been wondering why Ashdown got the cabinet volume so wrong. It looks to me like they specified the width of the cab to match the width of the amp, which is logical. I suppose they specified the depth of the cab so that the amp would fit in there too. Makes sense. And then they specified the height of the cab so that a 10- inch driver would fit with enough space for the grille surround. So that's how the professionals do it! 😁 (Present company excepted, of course). The lack of a port remains a mystery. Especially as their published description claims it's ported.

I entered the Celestion Pulse 10 and the Sica driver into my modelling program and the Celestion performs marginally better in the 41-litre cab, but I'd persevere with the Sica rather than going out and buying a another driver. My software recommends a slightly longer port than @agedhorse. The standard length of the usual 100mm ports is 115mm. According to my software, that would tune your cab to around 52Hz, which would be fine.

Port midrange leakage, particularly of standing waves, is worst when you locate ports in the corner. They're OK for subs where you're not reproducing midrange frequencies. It's the same principle as locating your loudspeakers in the corner of a room. I avoid doing it.

Looks like a 4" port will fit. It should make a big difference. Keep it as far away from the corner as you can. Was there any damping material in the box when you looked inside? Ashdown don't normally bother to fit any. If not, it would be worth putting some in.

According to the Ashdown blurb, the C110H-400 combo is supposed to be ported. The Sica driver definitely belongs in a ported rather than a sealed box. Perhaps Ashdown forgot to put the port in the baffle.The only other explanation is that the tea boy designed the cab. The Sica driver is a decent budget driver and the Eminence would definitely be a downgrade. I think the OP's original idea was sensible. However, before anyone can advise on porting, we really do need accurate internal measurements in order to work out the cabinet volume. I doubt that it's 55-60 litres. Is there space on the front baffle for a 4-inch port?

What make is the cab?

Angling and raising a cab does work if you want to hear yourself better, but it doesn't actually do what's needed, which is improving your cab's dispersion at mid and high frequencies so that you - and your audience - can hear those vital midrange frequencies clearly. When you point your cab at your ears, you only hear those midrange frequencies when you're standing right in front of the cab, because the cab's still beaming above 1kHz or so. As soon as you step to the side, you go back the muffled sound that everyone else - the rest of your band and your audience - is hearing. The only solution is to have a cab with a decent power response. The only cabs I know of that deal with this issue properly are the Fearless 3-way designs - apart from the BCMkIII DIY design that @Chienmortbb referred to. Good quality PA cabs usually have a decent power response because their main job is reproducing midrange frequencies, although they have their own issues for bass guitar reproduction.

The crossover brings the level of the HF unit down to match the bass/mid driver and applies a high pass filter that matches the natural, upper rolloff of the bass driver. This is what virtually every bass cab manufacturer does. It's simple, it's easy and it's cheap. Both the compression driver and horn are usable down to 2.5kHz, and that's where the system could be improved. However, to get the two components to cross over at 2.5kHz, you'd need to filter the upper response of the bass driver, which means additional components. The circuit for the HF unit would also be more complex than it currently is. Chances are, you'd end up with three times as many components in the crossover, which was not the aim of the project.

The Design Diary progressed from a Beyma SM212 on its own to a Beyma SM212 with a Celestion CDX1-1445 and P.Audio PH-170 horn - all ceramic magnets. The crossover for that system disappeared from Basschat when a particular image hosting company closed down. Fortunately, chienmortbb has recently located the circuit in his files. So if anyone would like a copy - particularly @nekomatic - just ask. We then went all-neo with a Faital Pro 12 and the Celestion CDX1-1425 - again using the PH-170 horn. Using any other components would mean a complete crossover redesign. The Celestion 1415 could in theory be substituted for the 1425, as they are quite similar. However, their sensitivity is different and you'd need to account for that in the crossover. As far as inductors are concerned, there's an Ebay.uk seller who winds inductors to custom values in small quantities. The biggest European manufacturer of coils is a German company called Intertechnik, although I don't think they do custom values.

I don't doubt you in the slightest.

Man cannot live by in ears alone, grasshopper. 😁

If I were looking for a cab for slapping, I'd look very closely at the tweeter being used. Some makers - not very many - fit good quality tweeters to their cabs but most fit a generic cheapo Foster of P.Audio phenolic diagram bullet tweeter, which is awful and one of the reasons so many bass players turn them off. Sad to say, no bass cab manufacturer fits a genuinely high quality HF unit. If you want one of those, you need to be looking at a PA cab.