stevie

It would be interesting to know what the crossover is supposed to be. The picture of the x-over earlier in the thread shows four 100uF 40V *polarized* electrolytics and two diodes. That's a weird configuration. I wonder if somebody has changed the caps at some time (from bipolar).

Yes, thanks Keith for all your efforts. I do hope this has now developed into an annual bash.

I've upgraded most of the parts on my BB1100S over the years. Its main problem was being neck heavy, which I fixed with a set of Hipshot lightweight tuners. I've never looked back. It's also got a Schaller bridge, a Duncan Vintage P-Bass and a Duncan Musicman pickup. I've never felt the need to change the preamp. Your mileage may vary on the pickups. The Schaller bridge looks a lot better and is nice to adjust but probably doesn't change the sound one iota. However, if your bass is a bit neck-heavy, I strongly recommend lightweight tuners, as they will make your bass so much more comfortable to play.

I remember the original Brightbox speakers having rubber, not foam, surrounds. They were purely midrange drivers with a phase plug in the middle. They stopped making them last century. I expect any decent quality 5" PA midrange would do a similar job. Bass/midrange or hi-fi drivers are unlikely to be sensitive enough. Edit: I obviously missed the photo of the original drivers on the previous page.

Don't forget the Major's amazing contribution to this site: <http://basschat.co.uk/topic/74284-the-majors-bass-boot-camp-session-index-1-36/>

I'd like to thank all of who who brought and set up their rigs for us to try. They all sounded great in their own ways - not a dud amongst them. I certainly learned a lot.

We did, thank you. Just arrived back in Dorchester.

I think it's a Stingray. If my memory serves, it featured strongly in a thread on here about "The worst bass amp you've ever played" - or something like that. Found it for you: <http://basschat.co.uk/topic/198205-worst-amp-you-have-owned-or-had-the-luck-to-use/> Described by one experienced contributor as ".... the most toneless, lifeless waste of components I have ever had the misery of hearing. I hated the bloody thing." I suspect this wasn't the answer you were looking for.

Looks like I'll be able to make it too. I'd be interested in having a look at the Fearful, Jim. I'm not sure what to bring though - all my gear is heavily customized. Anyone interested in trying out a Seymour Duncan Double Back compressor?

[quote name='dannybuoy' timestamp='1392397618' post='2368257'] Must be a good amp if Gandalf uses it. [/quote] Yeah. Dolly Parton appears on their Artists web page. Must be good.....

You guys must have extremely good memories, that's all I can say. Thanks for the chord sheet, ambient - brilliant! Now I'll see if I can fudge a walking bass line.

[quote name='owen' timestamp='1391880854' post='2362286'] I would love a cab engineered for the increased LF extension (fully accepting the efficiency trade-off) that my ACME offers. Would that be an option? I am also a huge fan of DSP as evidenced in all the grownup PA systems as well as the Berg IP series. There was a thread on TB looking at DIY DSP [url="http://www.talkbass.com/forum/f36/diy-line-mixer-crossover-eq-high-pass-filter-749884/"]http://www.talkbass....-filter-749884/[/url] which would be great to slot into a nice 12" cab. [/quote] A cab engineered for LF extension (with the trade-offs that entails) is certainly on the cards but it will have to be based on drivers that are easily available to the DIY'er. DSP is a fascinating field (and I'm discovering that the eq available from the current crop of bass amplifiers is not capable of properly equalising compact cabinets) but is beyond the scope of this project.

Not much more to say, really. If you have a transcription or midi file of Is You Is Or Is You Ain't My Baby, I would love a copy. Thanks. Not too hopeful but still......

The main problem with those drivers is that the manufacturer's specifications are likely to be wildly inaccurate. WinISD won't do you any good at all unless you have reliable T/S parameters. As to excursion and power handling, the specs are probably very optimistic. The frequency response of driver 2 looks fine to me but I doubt that it's accurate. It certainly looks the most promising of the trio. Try the 12s in a 50-litre box, tune to 50Hz and see what you've got.

[quote name='redstriper' timestamp='1391711743' post='2360542'] Thanks Chris, that doesn't sound too bad, does it take account of the inset handle and the quite thick walls? [/quote] Exactly. It depends on how thick the walls are, Steve, but the internal volume of the Flite cab is probably around 55 litres. Have a look at the yellow curve in the diagram I posted for the 3015LF - that's how much bass you are losing because of the small cab. The Ashdown MAG cabs are around 85 litres internal volume - still not big enough for your particular needs and they have a problem with inadequate porting which limits maximum output (porting is a subject that the three of us have discussed at length and that Phil will talk about in detail later on in this thread). If you could modify the Flite cab to take a 12 you would get better results. I don't know of a sound reinforcement 15" speaker that will produce reggae-style bass in a 55-litre cab.

The 3015 will produce prodigious amounts of low end but it needs a cab between 100 and 120 litres to work properly. If you put it in a smaller one it will still work but you will lose quite a bit of output between 40 and 80Hz - exactly where the fundamentals of the bass guitar are. It's good old Hoffman up to his old tricks again. Here are curves showing the 3015LF in 60, 90 and 120 litres. Notice how the bass efficiency drops as you reduce the size of the cab with the same driver. There is a point with every driver where you don't get much more bass by increasing the cabinet size and it's around 120 litres with that 15. [IMG]http://i60.tinypic.com/2l6v6t.jpg[/IMG]

Really nice styling and clearly not by the same industrial designer who gave us the jolly green amps. It could be a serious contender. Two criticisms. First, there is no excuse for a single Speakon on a 500w amp. It's penny pinching. Yes, I know Mark Bass and others are guilty too. Second. Nobody uses the sub bass harmonics generator. (We'll now hear from the two people on the forum who do). Otherwise, I like it a lot.

[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.