12" Cab Diary Continued

[Chienmortbb]

In my experience,  Duke is one of the good guys. He responds to messages and answers stupid questions without condescension. A bit like Stevie and passinwind.

[Chienmortbb]

On 05/02/2018 at 09:03, RichardH said:

Looking at the spec of the PR300 and PR320, the PR300 appears to be a touch more efficient (at 99dB rather than 97dB). I am assuming that the extra XMAX of the PR320 more than compensates for this difference - and I suspect that the measurement of efficiency is not such a clear cut thing as a single number suggests...

 

Richard, the efficiency of a driver is usually quoted at 1Khz. It is of little use in bass cabs. The art of bass cab design is squeezing every last ounce out of a driver in the bass area (down low) and a big Xmas is a great help. 

It is not the only thing though. I once described designing a bass cab as like squeezing a balloon. Push it in one area and it bulges in another. 

The Beyma used in my cab is exceptional in its price performance ratio and still has a higher Xmax than the Faital Pro drivers  you mention. It is also lighter than a number of 12” neos on the market. The Faital Pro 320 is close in spec to the Beyma SM212 and is lighter but it will be a compromise.

My cab also uses a Celestion Compression driver that, like the Beyma SM212 uses a Ceramic magnet, Stevie is investigation how much difference there is using the 320, a Neo 12” and a Neo compression driver. The aim is to maintain the performance but reduce the weight by a couple of Kg. 

He is currently still squeezing the balloon.

Edited February 6, 2018 by Chienmortbb

[stevie]

I was going to say exactly the same thing. Midrange efficiency, which is what everyone is talking about when they quote efficiency figures, doesn't really matter that much in a bass guitar cab. What matters is its efficiency at low frequencies - and cabinet size is a major factor in that. The PR320 gives up a couple of dBs of midrange efficiency compared with the PR300 but gains LF output potential.  Here's a comparison of the two in the cab we're using:

It's clear from this that the extra midrange efficiency of the PR300 doesn't contribute anything useful. It just (over-)emphasises the mids. To get a proper sound balance between bass and midrange , you'd probably want to cut the excess mids. In a mid-high PA cab, where you have subs, the PR300 would be the better choice because that's where you want good midrange efficiency and aren't too worried about excursion.

[RichardH]

As I suspected. I couldn't find a source to state at what frequency efficiency is measured, so thanks to the clarification.

[stevie]

At least the driver manufacturers provide a frequency response under known conditions (and TS parameters) so that you can get a good idea of what their products do. Comparing the datasheets for the two Faital divers is quite informative. Bass cab manufacturers could do something similar, but choose not to.

Edited February 6, 2018 by stevie

[Phil Starr]

   posted in the wrong thread

Edited April 10, 2018 by Phil Starr
posted in wrong thread

[stewblack]

Thank you so much for this Phil. Quick question, would this box be ok for a 10" driver? I know we had a quick chat on Sunday but value your written input so I thought I'd ask again. The speakers I have are Epifini 101218 with a 6.5 inch diameter magnet.

[Phil Starr]

Hi Stew, I put this on the wrong thread. I'll try again in an hour or so and get back to you then. 

[stewblack]

No rush mate. Enjoyed watching it but boy oh boy I wanted to hear it at the end!!!

 

[Phil Starr]

1 hour ago, stewblack said:

Thank you so much for this Phil. Quick question, would this box be ok for a 10" driver? I know we had a quick chat on Sunday but value your written input so I thought I'd ask again. The speakers I have are Epifini 101218 with a 6.5 inch diameter magnet.

I assume you mistyped. Epifani? anyway the only thing I got on a search was a Diego Epifani's Naples phone no! Who needs Cambridge Analytica

 

that's a big magnet which implies a well damped speaker. I looked on Friday at buiding a cab for a 10" speaker with a smaller magnet than that and the cab came out smaller than this cab. Without the details I can't be completely sure but my best guess is that your speaker would be better in a smaller cab. It might be worth your while contacting Epifani and seeing if they can give you an more details of the driver. If they'd let you have the Thiele Small characteristics we could design you something quite decent.

[stewblack]

1 hour ago, Phil Starr said:

I assume you mistyped. Epifani? anyway the only thing I got on a search was a Diego Epifani's Naples phone no! Who needs Cambridge Analytica

 

that's a big magnet which implies a well damped speaker. I looked on Friday at buiding a cab for a 10" speaker with a smaller magnet than that and the cab came out smaller than this cab. Without the details I can't be completely sure but my best guess is that your speaker would be better in a smaller cab. It might be worth your while contacting Epifani and seeing if they can give you an more details of the driver. If they'd let you have the Thiele Small characteristics we could design you something quite decent.

Sorry yes a typo. I'll see if Epifani can shed any light

[stevie]

If you're ever in the Dorchester area (you're not a million miles away) I can measure the T-S parameters of the Epifani driver for you.

By the way, this thread is still ongoing. We're working away in the background to finalise the lightweight version of our 12" cab. Watch this space.

[stewblack]

1 hour ago, stevie said:

If you're ever in the Dorchester area (you're not a million miles away) I can measure the T-S parameters of the Epifani driver for you.

By the way, this thread is still ongoing. We're working away in the background to finalise the lightweight version of our 12" cab. Watch this space.

Thank you Stevie, I shall take you up on that.

[stevie]

You're welcome. Just send me a PM when you're ready.

[stevie]

I know there hasn't been much activity on this thread recently, although there have been a few references to it in other threads. As previously explained, the next stage here is a lightweight design using neo drivers. As an interim step, I've just revised Chienmort's Beyma system by swapping out his Celestion ceramic compression driver for a neo one. The sound hasn't really changed, but we've saved about 1.5kg thanks to the new compression driver and simplified crossover.

Phil asked me how it measures, and the easiest way of showing him is to post the measurement here. So.....

I've been able to compare this cab with my own version fitted with the Faital Pro 12PR320 (and the same compression driver) and the Faital Pro cab is noticeably better in a number of areas. I'm therefore not going to publish any details of this interim system, but will go straight to the Faital Pro system once I have revisited the crossover to see if I can't make it a bit simpler.

As you can see from the frequency response curve, this design is as FRFR as you like.

[RichardH]

Look forward to seeing more details soon!

[LukeFRC]

16 hours ago, stevie said:

 

I've been able to compare this cab with my own version fitted with the Faital Pro 12PR320 (and the same compression driver) and the Faital Pro cab is noticeably better in a number of areas.

Intreaging ...

[Chienmortbb]

18 hours ago, stevie said:

I know there hasn't been much activity on this thread recently, although there have been a few references to it in other threads. As previously explained, the next stage here is a lightweight design using neo drivers. As an interim step, I've just revised Chienmort's Beyma system by swapping out his Celestion ceramic compression driver for a neo one. The sound hasn't really changed, but we've saved about 1.5kg thanks to the new compression driver and simplified crossover.

Phil asked me how it measures, and the easiest way of showing him is to post the measurement here. So.....

I've been able to compare this cab with my own version fitted with the Faital Pro 12PR320 (and the same compression driver) and the Faital Pro cab is noticeably better in a number of areas. I'm therefore not going to publish any details of this interim system, but will go straight to the Faital Pro system once I have revisited the crossover to see if I can't make it a bit simpler.

As you can see from the frequency response curve, this design is as FRFR as you like.

I hate you Stevie. Just when I am close to cabinet Nirvana you tell me there IS an Eight Heaven. Just off to get my Ruler calibrated to that plot.

[Jack]

So, no to flat packs? 😊

[Pea Turgh]

No likey words. Need see piccies.

[stevie]

I haven't given up on the flatpack idea entirely, Jack and I still have one or two avenues to explore. But let's get the final design up first.

I also need to contact Marco (Ghost_Bass) to see if he can finalise the drawings. I haven't seen him around for a while.

[stevie]

3 minutes ago, Pea Turgh said:

No likey words. Need see piccies.

I'll be resuming this thread in a couple of weeks, Peter - with plenty of piccies.

[Chienmortbb]

Stevie and I had our cabs cut to size from 15mm Italian Poplar Ply although we did change the bracing as Stevie found resonances in testing. There is no reason why there could not be a flat pack version. I cut the holes for the woofer with a router and Stevie had a circular hole saw for the port.. The horn is a slightly odd shape but not too hard to do.

We used Timbmet for the wood/cutting and they do have branches all over the country. They also offer a CNC service which may, or may not be worth using but would give accurate hole cutting. However as Stevie says, lets wait for the final design first then we can research the options.

[fleabag]

I'd be in a queue for a flat pack. 

[Pea Turgh]

#metoo