stevie

[quote name='redstriper' timestamp='1391554584' post='2358641'] Why does a cab have to be less sensitive to be more bassy? [/quote] Good question. It’s because there is a direct relationship between cabinet size, low frequency extension and efficiency - as summarised in Hoffman’s Iron Law, which was a forerunner of the Thiele & Small parameters upon which all cabinet design is now based. There is a mathematical formula for Hoffman’s Law – just google if you want to know what it is. The relationship of cabinet size with low frequency extension is fairly obvious. A 2 x 18” cabinet is going to go lower in the bass than your little transistor radio - and a double bass can produce more bottom end than a violin. The third variable, efficiency, is not quite as easy to grasp, but Hoffman’s Law says that if you want lower bass extension *without* changing the size of the box, the only way to do it is to sacrifice system efficiency. To compensate (and get back to the same sound pressure level as before) you will need a bigger amp and a drive unit that can move a lot of air. Alternatively, you can also increase bass extension by increasing the size of the cabinet (and using an appropriate driver). The easiest way to understand how this works is to look as some simulations. This is a simulation of the two 12" Kappalite drivers in the same 50-litre box. The Kappalite 3012LF (blue), a driver known for its good bass extension in this size of cabinet, has a sensitivity of about 94dB at one watt. The other is the KappaliteHO (white) - sensitivity (roughly) 98dB. The differences when you put them both in the same box are self-explanatory. We can go down even lower in the same cabinet if we drop the system efficiency still further. Here we see the Kappalite 12LF and the BMS 12n630 (red), which Luke mentioned, in the same cabinet. Despite the fact that the BMS is 4dB less sensitive than the Kappalite overall, the BMS is 8dB louder at 30Hz. Now, if we drop system efficiency *and* increase cabinet size, we get this (yellow): Which is a 12" Scan-Speak hi-fi driver. The white curve represents the other end of the scale and is the Eminence Kappalite 3012HO again. Maximum output and power handling are another matter.

Comparing the measurements in issue 8 of Bass Gear Magazine, the bass extension of the Fearful 12/6 - which uses the Kappalite 3012LF - is quite close to the Acme 12 - which uses a version of the Kappalite 12. So I reckon you would get fairly close. The Acme is tuned very low though, about 33Hz I think, which is about 15Hz lower than the Fearful. I'm not sure how much that contributes to what it does. We can give you some guidance on experimenting with cab tuning. I prefer to tune for power handling myself, whilst Lawrence seems to favour a shelf-type bottom end that reaches lower by tuning lower. There are various ways of reducing the sensitivity of a drive unit. A less powerful magnet, a more flexible suspension and a heavier cone are the main ones.

I can give you a list of the 12" drivers that are in our possession and that we may be trying out: Beyma SM212 Ciare 12.00NdW Celestion TF1225 Celestion TN1230 DAS Audio P12 Eminence Beta 12 Eminence DeltaLF Eminence Kappalite 3012LF. It's not a list of recommended drivers though. When we look more closely at these it will become apparent which ones are suitable and which are not - and why. This should help you choose your own drivers in the future. We can't test every potential driver out there - so our list of recommendations will necessarily be limited to what we can get our hands on. However, there are a couple of drivers that we would like to test but which we cannot really justify going out and buying. These are the Celestion BL12-200X and the Faital Pro PR300. If anyone has one of these and wouldn't mind lending it to us when we reach the measuring/testing phase, that would be great.

I sold my Rega 3 decades ago and have never regretted it.

When did they start putting bass amps in biscuit tins?

I'd be happier using one of these than the majority of commercial cabs on the market. Not sure I'd bother with the tweeter though.

Diablo, the ISA slot was still fitted to some motherboards using the Pentium 450MHz. So don't give up.

Al bought a speaker cab from me. He was very easy to deal with. Paid promptly and responded quickly to emails. Nice one!

[quote name='JapanAxe' timestamp='1390512714' post='2346361'] Jack socket speaker outs on a 500W head!? Man up and fit speakons! [/quote] A good sign that they are built down to a price.

I loved Dan's review, but this is what I think he really meant (no offense, Dan)... "I just got a Mi12 it joins a LB212 and a CL610. For less than £300 quid its a cracking cab." [i]I paid 300 smackers for it – so admitting that it’s rubbish would make me look like a pratt.[/i] "It has good smooth highs and its very punchy." [i]The highs are a bit rolled off.[/i] "It also has great tight low end." [i]Not much bottom end either.[/i] "It has a natural very smooth low mid hump which makes it cut through the mix very well." [i]It has an annoying honk in the lower mids.[/i] "Also testament to a decent designed crossover / tweeter it doesnt sound harsh with the valve Amp." [i]The tweeter's not very loud either.[/i] "Very pleased with it." [i]300 smackers pleased.[/i] "Two downsides its big, its is defo the biggest 1x12 I have seen." [i]What was I thinking? I should have bought a 15.[/i] "Its an easy one hand lift though." [i]Made of some cheap thin material I'll bet.[/i] "Other problem is the tolex on some of the cabs is a bit wonky. Not really an issue soundwise" [i]At least the wonky covering doesn't affect the sound. That's something, I suppose. [/i]

Roland Lumby is the man.

[quote name='ebenezer' timestamp='1390557034' post='2346686'] I swapped the 12 inch driver in my aguilar gs 112 for a eminence 3012 ho kappalite expecting good results!!.... all i can say is, i was unhappy with the sound(yes i know the stock driver is 4.8 xmax and 95db......3012 6.2 xmax and 100.5 db)...i found it only a small amount louder than stock driver.....sound wise,it did not mesh well with tweeter and crossover...too aggressive in the mids and the bottom end not that good.....3012 now back in the box! [/quote] I’ve run both of these drivers through my modelling program and can show you what happened when you changed your speakers. You'll notice that the difference between the two speakers is largely in the midrange, with the Delta 12LF looking fairly balanced throughout its frequency range and the Kappalite HO looking decidedly mid-prominent (the Kappalite is the green curve). The most interesting portion of the graph is below 100Hz. Here the drivers are very close – as you’d expect because this is where the cabinet dominates system performance. What this means in practice is that if you want to maintain sensitivity but get more bass extension you must increase the size of the cabinet. If you want to keep your existing cab you can only increase bass extension if you are prepared to accept a reduction in overall sensitivity (as Acme have done, for example). You can't simply fit a more sensitive driver and expect it to produce more bass. It is worth pointing out that the cabinet Phil is building will allow the use of a range of drivers, allowing you to choose the type of sound you want within reason. We will be modelling different drivers, verifying their published specifications and showing you how they measure in a finished cab.

In the spirit of the thread, I have a Dell mid-format Pentium IV motherboard, a Foxconn LS-36, available to a good home. I believe it came from a Dell Dimension PC. It's complete with processor but no heat sink or memory. 3GHz - so not that ancient. Shame to bin it, but I have too much stuff lying around.

[quote name='flyfisher' timestamp='1390228734' post='2342835'] Interesting. I know that the mobo PSU connectors have evolved over the years but I've always assumed that if it fits then it must be fully compatible. [/quote] Yes, ISA cards need a -5V connection, which was removed when 16-bit cards became obsolete. Not a lot of people know that ..... but why should they? Thanks for all your efforts.

Thanks guys. There aren't any local retail outlets near where I live. Photobox looked quite good - so I'm uploading to them now, or trying to anyway.....

[quote name='flyfisher' timestamp='1390226176' post='2342778'] You're still welcome to it but I appreciate you might want to change your mind! Let me know what you think. [/quote] That's very good of you but I think that I'd rather see if I can get a PC with a working power supply. The power supplies do seem to be the weak link on those. Unfortunately, you can't fit a new power supply - it has to be an original one capable of supplying the special voltage to the ISA card. I appreciate your looking anyway.

No screen needed, thanks. I gave my last CRTs away on Freecycle. Oh, and there's no rush on this, by the way. Please take your time.

Just bought a Markbass amp from Pete. Ultra-speedy service. It was in great condition and came in original box and documents. Very reasonable price, too. Definitely a recommended seller.

[quote name='flyfisher' timestamp='1389904975' post='2339471'] I'm pretty sure I've got a Dell XPS P2 333MHz and a Dell XPS T600r P3 600MHz somewhere. I presume they would have 8-bit ISA slots but you could probably check on the Dell website. I say 'pretty sure' because I scrapped a lot of stuff last year, but I think it was mainly CRT screens, and 'somewhere' because we moved last year and a lot of stuff is boxed up. Both were working when I stopped using them. The P2 box has Windows95 on it and the P3 box has Ubuntu. You're welcome to them if I can find them but I don't want to start searching high and low unless you're really serious. [/quote] I found the T600 on the web (http://www.geeks.com/details.asp?invtid=XPST600R-1B) but not the other one. According to that site, the T600r has an ISA slot, which makes it ideal for my purpose. I regularly use an old MS-Dos program based on a specific ISA sound card. If the P2 also has an ISA slot, I'd take that too. I'm happy to organize (or pay for) a carrier if you wouldn't mind digging it/them out and putting them in a box.

Anybody got an old Pentium II/III system with an ISA (8-bit) slot? I could use one of those.

I've finally bitten the bullet and sorted out the past 10 years of digital photos ready for printing. It was a major undertaking. I went online to look for a photoprinting company - but it's a minefield! Can anyone point me in the right direction? I have 380 photos to print - so I don't want to get it wrong. The range of prices is vast. How can you tell what kind of quality you're going to get? Which companies have easy-to-use websites? You're my last hope.

There's not much in the crossover but any faults should be visible (burning, frayed wires or bad connections). The L-pad may have gone - try adjusting it and listen for crackling and cutting out. A replacement is under £20 from the right place. You can also get replacement diaphragms for the HF unit for under £20 (from memory). £150 seems a bit steep to be honest. See if you can troubleshoot it yourself. If you locate the source of the problem, come back or pm me and I'll see if I can find a source for the spares. I had the same problem myself a while ago.

[quote name='6v6' timestamp='1389649952' post='2336649'] I had a look at the [url="http://profesional.beyma.com/pdf/8P300FeE.pdf"]Beyma 8P300[/url], do you have any thoughts on that for a compact bass cab? [/quote] It looks like a really nice driver. By the way, I've already plugged in my prototype mini-8 and it sounds surprisingly good. Lots of work still needed, of course.