Splitting an oldschool heavy 4x10 into two 2x10s - good idea or folly?

[SubsonicSimpleton]

I've noticed that there are many bargains to be had in the secondhand cab market, as many players are dumping older gear that they are no longer willing to store or move about - some of these old bulky and heavy cabs sound pretty decent, so I was considering buying one with the intention of repurposing the drivers into a pair of 2x10 cabs to make a modular 4x10 that would be more flexible in terms of pack space.

My cunning (or idiotic) plan would be to carefully measure the porting dimensions and internal volume of the original cab and then translate that into a pair of smaller braced ply cabs each with half the internal volume of the original, but I'm not sure whether I can get away with just halving the port cross sectional area and keeping the length the same.

Using the publicly available fearful plans as a reference point for the amount of bracing required on the 15/6 and 15sub designs, and weight data from wickes for sheet MDF/particleboard/hardwood ply, I reckon that a fairly major saving on cabinet weight would be possible (region of 30% conservatively based on similar construction to the ashdown 1x15 I have in my possession, much more in the case of trace MDF construction or thicker walled chipboard), coupled with halving the load would transform a single 100lb 4x10 into two ~30-40lb 2x10 which would be much easier to live with for loading, but retain the same character as the donor cab hopefully.

Aside from the risks of buying a donor cab that may have been mercilessly thrashed or stored badly resulting in drivers with low life expectancy, are there any other compelling reasons not to try this?

The amount of effort would be pretty much identical to building a pair of 1x12s using the Beyma SM-212s as per the [url="http://basschat.co.uk/topic/227904-1x12-cab-design-diary/"]1x12 design diary[/url], however the re-engineering approach would allow me(in theory at least) to hear what the end result will sound like before committing time and energy to the build, and save a decent chunk on drivers.

Any suggestions/warnings with regard to donor cabs welcomed.

[Balcro]

Before you start cutting and sawing, it's worthwhile having a look at the individual drive units and checking they're all the same impedance as well as the stated impedance (ohms) of the existing 4x10.

You will probably have to do a re-wiring job unless your amp has twin speaker outlets. Put those figures up here and no doubt some experienced basschatter re-wiring expert will let you know what's necessary.

Ballcro.

[JTUK]

My only thoughts to this idea is, if you are using an old cab for the speakers, are they worth using..?

Might be better to sell it, if you already have one, as start from scratch.
Old cabs tend to be pretty basic and they are heavy because they have used
traditional ideas like birch ply, which can be very strong and rigid with minimal
bracing and therefore cheaper to throw together.
If the chasis are a certain 'vintage', and/or come out of an old PV or TE, for example
then the units are also going to be pretty basic. None of this makes them
bad, but power ratings were down on older speakers and you don't always know what sort
of life they have had...
The thing about multiple speakers in a cab is if one goes... and the speakers aren't made anymore
and the cone kits aren't available, you end up in quite a chase for a comparable model
and have to replace all units..
So, all in all, sounds like a nice project but not one that will save you any money..??

[SubsonicSimpleton]

Point taken with regards to the risks of older drivers, and I haven't bought anything at this point. Looking at the retail costs of new off the shelf units, it is cheaper to buy a new http://www.thomann.de/gb/hartke_410_tp_bass_speaker.htm than buying 4 cheap celestion or eminence 10s from lean business or blue aran - if you look at s/h collection only items on ebay/gumtree etc you can pick cabs up for almost nothing - no shortage of PV 4x10s that all use the sheffield 1035 for very silly money.

The cab situation seems to be split between manufacturers that are making the same bulky and heavy designs forever and the new school of neo-driver ultralight wideband cabs - I'm really interested to see if there is a happy middle ground combining the cab/speaker voicing of more traditional offerings with the weight saving construction ethos of the more innovative builders.

Opinions on the newer tech seems mixed - I don't doubt that in terms of measurable performance, designs by the forward looking and knowledgeable speaker gurus are way better than old school staples such as the fridge, but in subjective terms it is quite obvious that the best solution for any given musician/band can't always be measured purely in technical terms. IIRC a fellow bc'er commented in a thread not so long back that they preferred the sound of the cheap transporter to their more expensive 4x10, so I'm interested more in evaluating from a "if it sounds good to me then it is good" perspective.

[Phil Starr]

As ever it is not possible to give a completely straight answer. It depends is the only honest response.

If there is a 4x10 you love but can't transport then it is certainly an option.

Similarly if you just want a fiddle/learning experience it is a low cost alternative for a bit of DIY. (ooh er)

You'll need to retune the cab so running winISD might be part of the learning, but someone here will help you out if you need that.

Splitting the cab won't give you exactly the same sound. Off axis the speakers interfere and effectively cut the treble so using a single 1x10 or vertically stacked 4x10 will give you a clearer sound. You could always eq the extra treble out if you like the old school thump.

It is a way of getting good quality speakers at a decent price. I like the PV Black Widows and you can pick up the BXBW 15's for peanuts. I bought one of these myself and built a more back friendly cab which I used for a couple of years. It's now in the rehearsal room. If you get the PV 2x15 (for around £100) with the metal domed BW's they sound quite nice and the drivers alone would cost £300. I guess similar sums would apply to the 4x10's.

That brings in the taste issue. I'm a speaker guy and the BW's are better quality than the sheffields but if you prefer the sound of the Sheffields then go for them or whatever else you like.

Impedance is a little bit of a problem. You'd naturally want a 2x10 to be 4ohms, so wire the two 8 ohm speakers in parallel. if you then plug in a second speaker you'd get 2ohms which most amps won't do. The alternative is to wire the two speakers in series and get a 16ohm 2x10 and then 8ohms when using a pair. That limits the sound levels with the single 16 ohm cab. You could use the two 4ohm cabs by wiring up a series lead but these aren't commercially available. OBBM perhaps?

IMO there is nothing technically wrong with a load of cheap speakers packed into a cab, the only downside is transporting the thing and dispersion. It was a great way of getting a loud sound when amplifier watts were expensive. Gigging with the 1x12 Beymas I personally roll off the bass quite severely, it's good to know it's there if I need it and the sound is nice and clean but we can get obsessed with the bottom octave from a technical point of view when in reality it is of peripheral importance to a good tight bass sound.

Four new 10" drivers are going to cost £160-200, 2x12" Beymas £165 so if you pick up a 4x10 for £80 you can play without much investment. The cabs will cost something like £50ea by the time you've paid for coverings and handles etc.

Edited July 18, 2014 by Phil Starr

[HowieBass]

A few BCers have rated the Harley Benton 210T cabs quite highly, 250W 8ohm with tweeter level control for a little over £100 plus shipping from Thomann - another option to consider rather than go down the DIY route if it's a matter of economics rather than a fun-to-do project... http://www.thomann.de/gb/harley_benton_bb210t.htm

[SubsonicSimpleton]

[quote name='Phil Starr' timestamp='1405669577' post='2504113']
Impedance is a little bit of a problem. You'd naturally want a 2x10 to be 4ohms, so wire the two 8 ohm speakers in parallel. if you then plug in a second speaker you'd get 2ohms which most amps won't do. The alternative is to wire the two speakers in series and get a 16ohm 2x10 and then 8ohms when using a pair. That limits the sound levels with the single 16 ohm cab. You could use the two 4ohm cabs by wiring up a series lead but these aren't commercially available. OBBM perhaps?
[/quote]
If I did try this, I wouldn't be attempting to use the 2x10 modules as standalone units in a rehearsal or gig situation - I would be inclined to parallel link the two cabs and then if the donor cab was wired with series/parallel pairs wire the drivers internally in series - in the event of a driver failing I would rather have the amp seeing a 16ohm load from the remaining cab than seeing 4ohms(or less if also using an 8ohm 1x15 in big stack) with the volume cranked.

I've played with winisd, and sussed out how to get the pro variant to accept t/s parameters without throwing errors, but the parameters are not available for all of the drivers that get used as OEM fitments, so even if the internal volume can be translated by straight split, if the port tuning is more complicated than simple division of the existing port cross section then maybe that is a real issue that kills this idea dead. I don't really understand all the nuances of port tuning, but from what I've read, if you get the tuning wrong, the best case is honking and the worst is that you unload the drivers and can kill them with overexcursion on low frequencies.

[Phil Starr]

The tuning of the cab is independent of the drivers. If you know the volume of the original cab and the port dimensions you can work out its tuning frequency. tune the 2x10's to the same frequency and you'll be fine, or at least no worse off than you were before. As I say someone will do this for you if you need that

[Mottlefeeder]

One of the issues with changing a port is that the air speed through it changes, and that can give you problems. You could try modelling a cab similar to the one you buy, and then model the half size version, and check that the tuning and port air speeds are as you want them. Having said that, if you are already playing with WinISD, you may already have considered this.

David

[SubsonicSimpleton]

[quote name='Phil Starr' timestamp='1405723376' post='2504829']
The tuning of the cab is independent of the drivers. If you know the volume of the original cab and the port dimensions you can work out its tuning frequency. tune the 2x10's to the same frequency and you'll be fine, or at least no worse off than you were before. As I say someone will do this for you if you need that
[/quote]
Just learnt something new playing with WinIsd, I didn't realise that it would calculate the cab tuning for me if I set the volume and then adjusted the port dimensions. I have an Ashdown MAG 1x15 combo and extension cab, so I'll give them both a careful measure up and see what I can learn. Everyday is a schoolday, advice much appreciated.