G12H-75 Cream Thiele Small Parameters

[TheKman76]

I call bullshit on their bullshit.

I imagine this like a jigsaw puzzle. I may only have a handful of pieces and can't see the whole picture, but Celestion (and others) suggest we completely ignore 3/4 of the picture regardless. I like the sky bits.

No experience with Jensen, but, damn straight, Eminence make a great range of Hi-Fi gear and clearly appreciate that this data is valuable to everyone.

That said, I can certainly accept that the guitar speakers we know and love are *extremely* primitive and come with a vast array of exceptions to the Hi-Fi rules of design.

 

[mickeydg5]

I imagine this like a jigsaw puzzle. I may only have a handful of pieces and can't see the whole picture, but Celestion (and others) suggest we completely ignore 3/4 of the picture regardless. I like the sky bits.

No experience with Jensen, but, damn straight, Eminence make a great range of Hi-Fi gear and clearly appreciate that this data is valuable to everyone.

That said, I can certainly accept that the guitar speakers we know and love are *extremely* primitive and come with a vast array of exceptions to the Hi-Fi rules of design.

Sorry but you can use guitar speakers for hi-fi. It is all about mechanics. A speaker is a speaker and all are designed with a frequency range in mind.
I like to use them in my car audio as more of a full-range utilizing 12" and 15" speakers instead of dedicated bass/low frequency drivers.

 

[TheKman76]

@mickeydg5 I don't disagree, I just wouldn't personally.

Cars are a very different animal in H-Fi terms, they come with a whole new set of rules and exceptions. If you're able to get the result, power to you, sir! I think we're saying the same thing from different perspective, just do it and see if it works. A result is a result, good or bad.

 

[mickeydg5]

@mickeydg5 I don't disagree, I just wouldn't personally.

Cars are a very different animal in H-Fi terms, they come with a whole new set of rules and exceptions. If you're able to get the result, power to you, sir! I think we're saying the same thing from different perspective, just do it and see if it works. A result is a result, good or bad.

No, what I am saying is you need to be able to understand and discern the information.

What, you think I do not apply it to my open, convertible and closed back guitar cabinets?



Bottom line is this information can help discern what the reactions of a particular speaker will be in any type of cabinet. If anyone does not understand that then they have some learning to do.

 

[TheKman76]

I apologise if I've insulted you, that's not my intention. Maybe I'm not expressing myself well, but I'm agreeing with you.

If you manage to design a system that works and get a good result, that's all that matters. I'm gonna' apply all the principles I know to design a cabinet for guitar, rules be damned. If it's a good result, great. If not, I learn something, also great.

Sorry if I'm missing something, none of this is intended to challenge you.

 

[fitz]

When are you going to fire up the table saw?

 

[mickeydg5]

I apologise if I've insulted you, that's not my intention. Maybe I'm not expressing myself well, but I'm agreeing with you.

If you manage to design a system that works and get a good result, that's all that matters. I'm gonna' apply all the principles I know to design a cabinet for guitar, rules be damned. If it's a good result, great. If not, I learn something, also great.

Sorry if I'm missing something, none of this is intended to challenge you.

No worries, .

 

[TheKman76]

I have a Firebird on the bench which needs refinishing and refretting... Could be a little while.

Also need to find a spot to store all the gear currently houses on the table saw.

 

[TheKman76]

OK, now I'm really stuck. Having picked up a Blackstar HTV-112 last week and had a play with the big open back cab I've landed on a big problem. The Swamp Thang is currently housed in the DSL chassis and it sounds amazing. This leaves me with nothing but Celestions to play with in my experiments. Bugger.

I've been swapping speakers around all week and just taking mental notes about how they each sound and which ones shine in what enclosures. Every speaker I have (only four) has been in each of the Blackstar cab and the DSL. Based on a few educated guesses I believe the tuning frequency of the rear opening on the DSL with the Swamp Thang installed it around the 180-200Hz range. This apparently lends itself to some amazing clean tones and really sweet finger picking.

With the Blackstar cab also connected and the Creamback inside it the mids only really pop when drive is applied, all of the cleans are dominated by the Swamp Thang and I love it! I suppose I shouldn't be surprised, it was purchased specifically for it's clean output, not drive. The down side is the bass output from the combo isn't great.

So, back to square one. Anyone know where I might find T/S parameters for the Creamback? The alternative is to try and build as much flexibility into the experiment as possible, which will take much longer.

Thanks in advance.

Dave.

 

[JohnH]

There's a few different Creambacks. But I was looking at the 65W one and although T/S info is not around, I noted that many of the more basic key parameters aren't that different to a Greenback G12M. eg, same frequency response, resonant frequency, magnet weight. and similar efficiency. Plus it's a 12" Celestion. So although it is no doubt a bit different , if you used Greenback parameters to do any cab analysis, how different would the resulting cab be? And if you then tried a few other sets of data, will you get a different conclusion about what you design should be?

WGS publish TS data, and G12M and a few other Celestion such as Alnico Blue are easy to find.

It's a way to test the sensitivity of the design.

 

[TheKman76]

I hear the Creamback referred to as a higher-power Greenback a lot, but I can't say if this has any credence.

Thanks John.

 

[TheKman76]

Interestingly the Hughes & Kettner Black Spirit Combo used the G12H-75 Creamback in a ~50L ported enclosure.

EDIT: just found their 1x12 cab, more like 40L minus ports. Pretty small!

 

[TheKman76]

Clean table saw, apply nitro to Firebird and a couple of spare hours. Yay!

I've taken some educated guesses at T/S parameters for the Creamback based on what I could find around, but it looks like they're off by some way. I no longer have all the equipment to measure the parameters I need anymore, so it'll be more guess work.

Anyway, I closed up the back which brought the resonant frequency of the system to about 90-95Hz. This sounded pretty good.

I've also installed two rear ports hoping to produce a new resonant peak around the 70-80Hz range. In theory this should have lifted everything from about 150Hz on down to ~60, well below standard fundamental guitar frequencies. However, what actually resulted was a resonant peak around 45-55 Hz. Maybe I can use it for bass?

So based on these results I should be able to get a result by making the ports a little shorter. However, there may need to be a significant drop in enclosure volume before this works well. Maybe 50L.

When I can hone in on a working system I'll start taking real measurements. In the mean time it's all a bit of fun in the workshop.

 

[JohnH]

Sounds interesting. So what internal volume and what port dimensions do you have in place so far? I reckon with that info it'd be possible to predict how to change it.

 

[TheKman76]

The empty enclosure is almost exactly 70L. Minus driver and ports it's around 65L.
Two ports, 100 x 100 x 100mm.

Three ways forward:
One, reduce the port length to 60 - 70mm. In theory this should move the resonant peak to ~80Hz, but still narrowish.
Two, reduce the cab volume to as low as 45L. This will broaden and flatten the resonance affecting the range from 70Hz to around 300Hz.
Three, a little of both.

I'll start by reducing internal volume as this is easily reversable.

I've found a couple of ported cabs with a Creamback now and they all seem to have smaller volumes.
Might have got a better result by trying the Swamp Thang, so I'll give this a go tomorrow too. This was, of course, what this cab was intended for.

 

[JohnH]

I checked back into my 1x12 cab build. and its pretty much exactly the same volume as yours, about 69l minus driver and ports. My process led me to three ports 50mm diameter and 40mm long.

 

[fitz]

Clean table saw, apply nitro to Firebird and a couple of spare hours. Yay!

I've taken some educated guesses at T/S parameters for the Creamback based on what I could find around, but it looks like they're off by some way. I no longer have all the equipment to measure the parameters I need anymore, so it'll be more guess work.

Anyway, I closed up the back which brought the resonant frequency of the system to about 90-95Hz. This sounded pretty good.

I've also installed two rear ports hoping to produce a new resonant peak around the 70-80Hz range. In theory this should have lifted everything from about 150Hz on down to ~60, well below standard fundamental guitar frequencies. However, what actually resulted was a resonant peak around 45-55 Hz. Maybe I can use it for bass?

So based on these results I should be able to get a result by making the ports a little shorter. However, there may need to be a significant drop in enclosure volume before this works well. Maybe 50L.

When I can hone in on a working system I'll start taking real measurements. In the mean time it's all a bit of fun in the workshop.

 

[TheKman76]

@JohnH Remind me what driver you used?

Clearly my T/S parameters are all over the place. According to what I have your design *should* have almost the same outcome as I've just observed. This is obviously not the case or you'd have changed it, I'm sure.

What I'm really getting from this is just how useless some of my guestimates are. Tomorrow I'll start by verifying the design with the Swamp Thang, this should be very predictable. Then work out next steps.

Ok @fitz I'll also get you some pics tomorrow too.

 

[JohnH]

further on ports and volumes ect...

As I understand it, the resonance due to the ports is like a mass bouncing on a spring.

The mass comes from the mass of air in the ports, and yours is about 6.7 x mine. The spring comes from the squashiness of the air in the cab, increased by the compliance of the speaker cone (I reckon both our cabs are about the same there), x the cross section of the ports , and yours is 2.7 x mine.

So out of all that, and resonance frequency generally depended on sqrt of spring/ mass, I reckon your ports are currently tuned to a lower frequency than mine, maybe by a ratio of about sqrt(6.7/2.7) = 1.6

So thats in the same general direction as your conclusions, smaller volume or shorter ports. I think Id want to try shorter ports.

 

[JohnH]

mine is a V30, in the ported version which I finally decided on .