Nightmare situation, your speaker is blown, and you need a replacement. Pop online and all you have to do is pick another one the right size that matches your budget. Sadly this isn’t the case – it can be whole lot more complicated than it seems, and this guide is intended to take you through the basics.

After thousands of phone conversations helping customer through this process over the years, we thought it was about time to write a short guide to help you through this process. Along the way we will aim to dispel a few myths, and help you make an educated decision yourself. If you cant work it out – we are still here to help, but you will at least know what information we need to help you.

First thing to realise is that there are thousands of different models of speakers out there, some current, some discontinued, and most manufacturers don’t make product data publicly available. Any information we have has been gathered from customer feedback, and our own experiences of doing repairs/upgrades which covers just a small fraction of the speakers our there. Our website has a compatibility database programmed into the search function. The quick way to check if we have a match is to just type into the search box any model numbers or product codes you have, and if we can find a match, any suitable options will appear in the search results:

You can access the dedicated parts search function here: https://www.bluearan.co.uk/index.php?partsearch – we discussed this previously in an older blog post: https://blog.bluearan.co.uk/speaker-parts-compatibility-database/

If you don’t get a result, all is not lost- but please don’t just pick up the phone and call us. We don’t have a secret hidden database of parts that we’ll only divulge over then phone, all we can do is search the same data you can search yourself, and if it’s not in the list the process of selecting alternatives can be quite involved and time consuming, and we need more information from you which is best sent to us via email: sales@bluearan.co.uk

Please include the following information:

a. Make/model of the speaker cabinet and/or drivers you want to replace

b. Dimensions of your current parts, ideally BCD, and baffle cut out diameter (see the guide below)

c. A few images of the parts you need to replace (front and back) as we can sometimes identify manufacturer by appearance.

d. Driver Impedance (if you have this information)

If you want to get going and find a replacement yourself, we’ve written a quick guide to help you along your way – click the links below to read more.

1. Check dimensions of your current parts
2. Power rating and impedance for the replacement
3. Check suitability for the cabinet type.

If you don’t have time to read all of this, just take away one piece of information from reading this, and I can not emphasize this enough. YOU SHOULD NOT BE SELECTING A REPLACEMENT SPEAKER PURELY BY LOOKING AT POWER RATING. Power rating tells you nothing about the performance, it’s a bit like choosing a vehicle based on engine size. The only thing you can measure is how much fuel you will use, it doesn’t tell you if it will do the job right. You could buy a sports car with a 2.0 litre engine, an SUV with a 2.0 litre engine, and a big van with a 2.0 litre engine – they don’t all do the same job in the same way, but the engine size is the same. You wouldn’t buy a big van as a speedy little runaround, and you wouldn’t buy a sports car for driving off road.

First step is to determine the size of the woofer. Woofers are generally grouped by nominal overall diameter, which is easy enough to measure. You just measure edge to edge of the outside of the chassis, and round down to the nearest inch. This works for most sizes, except around 5″-6″ where some manufacturers will state 5.25″ or 6.5″ rather than rounding off to the nearest inch. The speaker below has an outside diameter of 460mm, which is 18.1 inches – and for purposes of selecting a replacement, we consider this to be an 18″ woofer. When it comes to fitting a replacement with minimal hassle, a second measurement is also quite critical, the bolt circle diameter, or BCD. Whilst this tends to be fairly standard, it can vary by a few millimetres, particularly between pressed steel and cast alloy chassis, and can vary enough for the bolt holes to not line up. If you bolt holes don’t line up, replacing the driver ends up being a lot more work. The BCD is measured from the middle of the hole on one side to the middle of the hole on the opposite side, and ideally you want the BCD to be within around 2-3mm to avoid issues with fitment of the driver. Most manufacturers tend to follow a similar bolt pattern, but over the years one or two manufacturers have opted for non-standard bolt hole configurations, so this is well worth checking to save yourself a lot of hassle.

Thankfully most cast alloy chassis tend to have similar BCD, as do most pressed steel chassis. So the times you are most likely to encounter issues would be if you try to replace a pressed steel chassis driver with a cast alloy driver, or vice versa. The two different type of chassis are easy to distinguish, pressed steel chassis are generally sheet steel of around 1-2mm thickness that has been pressed into shape. Cast alloy chassis are thicker, sometimes 3-4mm or more around the edge of the driver, and thicker on the legs. For purposes of doing a drop in replacement, its generally much simpler to stick with the same type of chassis, as you have a much higher chance of everything lining up nicely with no modifications required.

Cast alloy chassis	Pressed Steel chassis

We’re nearly done on dimensions, a couple of final things to check are the hole cut-out size, and the overall depth. You are most likely to have issues with the hole cut out size if you switch from cast alloy chassis to pressed steel chassis, as the hole cutout (the hole in the cabinet) can vary by 3-5mm. If you upgrade from a pressed steel chassis to a cast alloy chassis, there is a good chance the hole cutout might be a little bit too small, and you may need to enlarge it. The other way around, from cast alloy to pressed steel may present bigger issues, as the hole may be too big, not leaving sufficient material around the driver for mounting screws. Most manufacturers specify the baffle cutout diameter in their specifications, so this is relatively easy to check.

The overall depth often isn’t something you need to worry about , however, if you are looking for a woofer for front loaded horn, rear loaded horn (scoop) or a bandpass design you may find the cabinet has been designed to accommodate a specific driver, and if you are upgrading to a modern driver, particularly a long excursion neodymium magnet woofer – its quite possible the magnet may be too long to fit the space – so please check the depth before committing to a purchase. If you are looking for drivers for specialist applications, this needs a lot more research than a standard design.

Once you have BCD, and baffle cut-out sizes, you can move on to the next stage: https://blog.bluearan.co.uk/selecting-a-replacement-speaker-part-2-power-handling-and-impedance/