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Phil Starr

1x12" Cab Design Diary

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Phil, thanks for your considered response. Think we can end the thread derail here!

Edited by funkle

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[quote name='funkle' timestamp='1405976609' post='2507229']
Phil, thanks for your considered response. Think we can end the thread derail here!
[/quote]

But the thing that I was wondering......

nah Funkle's right - lets hear more about this 1x12 :D

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[quote name='funkle' timestamp='1405971318' post='2507134']
Again, I'll ask though - in general - if you have a woofer which suits the job in hand, and enough power to drive it with, and it can take the power thermally and mechanically, but it isn't efficient, can applying extra power provide the extra volume to match another woofer with lower Xmax but higher efficiency?
[/quote]Perhaps. If you give up 3dB of sensitivity you need to increase excursion by 70% and double thermal power handling for equal output. Plus almost invariably the price of high xmax isn't just lower sensitivity, it's also less midrange. Changing driver parameters isn't like playing checkers, it's like playing 3 dimensional chess.

Edited by Bill Fitzmaurice

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[quote name='funkle' timestamp='1404387797' post='2492148']
Beyma SM212 specs - [url="http://www.beyma.com/uploads/ftp/Fichas_Tecnicas/000000730.PDF"]http://www.beyma.com...s/000000730.PDF[/url]

Interesting reading. The 98dB @ 1w/1m is an impressive figure. Not too heavy for a ferrite speaker. An apparently economical solution for a 2 or 3 way full range box. Vd of 382 cc and Xmax as you say 7mm.

I wonder if the Xmax of 7mm calculated in the same way that Eminence do their Xmax calculation?

The 3012LF, a high standard of comparison for Xmax in current bass cab drivers (apart from Alex Claber's proprietary 12" driver, where Vd is high - apparently 550cc - but we don't know how it is calculated) has bigger Xmax (9.1mm) and Vd (496cc) but much less efficiency at 1w/1m. I assume the 3012LF would really get going at higher power levels, and I note is rated for 450W RMS. Eminence specs - [url="http://www.eminence.com/pdf/Kappalite_3012LF.pdf"]http://www.eminence....lite_3012LF.pdf[/url]

I assume the Beyma SM212 is significantly cheaper than the 3012LF, and would lead to a simpler build? The Greenboy and Audiokinesis builds around the 3012LF are not cheap, I assume due to the extra parts, labour, crossovers, and additional drivers used to cover mid and higher ranges...
[/quote]In the UK the SM212 is lower than half the price of the 3012LF. In fact you could buy two and still buy us all a good drink.

Edited by Chienmortbb

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[quote name='Bill Fitzmaurice' timestamp='1405979350' post='2507282']
Changing driver parameters isn't like playing checkers, it's like playing 3 dimensional chess.
[/quote]

what a quote!

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[quote name='Bill Fitzmaurice' timestamp='1405979350' post='2507282']
Perhaps. If you give up 3dB of sensitivity you need to increase excursion by 70% and double thermal power handling for equal output. Plus almost invariably the price of high xmax isn't just lower sensitivity, it's also less midrange. Changing driver parameters isn't like playing checkers, it's like playing 3 dimensional chess.
[/quote]

Thanks Bill. That is exactly the sort of detail I was hoping for. 3 dimensional chess sounds about right!

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I still think the limits imposed by the shape of the LF transfer function on the bass end are being ignored, or at least not given much priority. The only practical way of making eg a Vanderkley sound like an Acme in the bass would be with DSP filtering, regardless of xmax/power limitations, because the EQ on even quite a flexible amp won't be able to sufficiently compensate for the difference in cabs to give a similar overall roll-off curve.
This is another reason to think carefully about tuning in the 40Hz versus the 50Hz regions, since tuning lower can give a curve that is easier to EQ within the range you actually care about using the EQ controls found on a typical amp (eg 12dB/oct shelving filters for the bass).

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My requirement is for a lightweight cab suitable for dub reggae, so I do not need much treble or upper midrange.
I currently use a small cab loaded with an Eminence 3015LF, which sounds good but it doesn't go as low as the new ACME 15" cab.
It would sound better in a larger box, but I don't want to do that.
Stevie suggested replacing the driver with a [color=#282828][font=helvetica, arial, sans-serif][size=4]3012LF, which would be better suited to the smaller box dimensions and sound deeper than the 3015LF.[/size][/font][/color]


[color=#282828][font=helvetica, arial, sans-serif][size=4]Would anyone else here care to comment on this idea, before I take the plunge?[/size][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][size=4]Specifically, what differences in tone and volume should I expect and is it a worthwhile modification, considering the work and cost?[/size][/font][/color]

[color=#282828][font=helvetica, arial, sans-serif][size=4]Apologies for the derailment.[/size][/font][/color]

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[quote name='redstriper' timestamp='1406038450' post='2507746']
My requirement is for a lightweight cab suitable for dub reggae, so I do not need much treble or upper midrange.
I currently use a small cab loaded with an Eminence 3015LF, which sounds good but it doesn't go as low as the new ACME 15" cab.
It would sound better in a larger box, but I don't want to do that.
Stevie suggested replacing the driver with a [color=#282828][font=helvetica, arial, sans-serif]3012LF, which would be better suited to the smaller box dimensions and sound deeper than the 3015LF.[/font][/color]


[color=#282828][font=helvetica, arial, sans-serif]Would anyone else here care to comment on this idea, before I take the plunge?[/font][/color]
[color=#282828][font=helvetica, arial, sans-serif]Specifically, what differences in tone and volume should I expect and is it a worthwhile modification, considering the work and cost?[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Apologies for the derailment.[/font][/color]
[/quote] ACME 15"? typo I would think?
Question - and not being fecicious - why not buy an ACME?

Edited by LukeFRC

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[quote name='LawrenceH' timestamp='1406036918' post='2507721']
I still think the limits imposed by the shape of the LF transfer function on the bass end are being ignored, or at least not given much priority. The only practical way of making eg a Vanderkley sound like an Acme in the bass would be with DSP filtering, regardless of xmax/power limitations, because the EQ on even quite a flexible amp won't be able to sufficiently compensate for the difference in cabs to give a similar overall roll-off curve.
This is another reason to think carefully about tuning in the 40Hz versus the 50Hz regions, since tuning lower can give a curve that is easier to EQ within the range you actually care about using the EQ controls found on a typical amp (eg 12dB/oct shelving filters for the bass).
[/quote]

The tuning frequency of a cabinet should be chosen to suit the driver. Most mid-bass drivers do not behave well when tuned too low. It can compromise the max power before XMAx is exceeded and so increase fartout. It also increases the very low frequency travel of the cone, increasing the boominess. Most shelving type bass comtrols make this worse.

If you need the extreme low end response ( and there are very good reason why you don't) you probanly should look at say the Eminenve Kappalite 3012LF, Precision Devices PD12SB40 or some of the Beyma & Faital Pro dedicated bass frequency drivers.

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[quote name='LawrenceH' timestamp='1406036918' post='2507721']
I still think the limits imposed by the shape of the LF transfer function on the bass end are being ignored, or at least not given much priority. The only practical way of making eg a Vanderkley sound like an Acme in the bass would be with DSP filtering, regardless of xmax/power limitations, because the EQ on even quite a flexible amp won't be able to sufficiently compensate for the difference in cabs to give a similar overall roll-off curve.
This is another reason to think carefully about tuning in the 40Hz versus the 50Hz regions, since tuning lower can give a curve that is easier to EQ within the range you actually care about using the EQ controls found on a typical amp (eg 12dB/oct shelving filters for the bass).
[/quote]
[quote name='Chienmortbb' timestamp='1406103815' post='2508272']
The tuning frequency of a cabinet should be chosen to suit the driver. Most mid-bass drivers do not behave well when tuned too low. It can compromise the max power before XMAx is exceeded and so increase fartout. It also increases the very low frequency travel of the cone, increasing the boominess. Most shelving type bass comtrols make this worse.

If you need the extreme low end response ( and there are very good reason why you don't) you probanly should look at say the Eminenve Kappalite 3012LF, Precision Devices PD12SB40 or some of the Beyma & Faital Pro dedicated bass frequency drivers.
[/quote]

Just in case people haven't been following this for all six pages :)

Lawrence is one of the people working on this design.

there is some flexibility in where to tune the cabinet and as you say it affects excursion and power handling in the bottom octave as well as frequency response. Fortunately it does this in ways which we fully understand (we as in anyone who can do the maths or run the software, I'm not claiming anything more than a rudimentary understanding of T/S) so we've modeled the SM212 in this cab at these frequencies. In fact the reason I'm keen on 40Hz is that it limits excursion more at 30Hz than the 50Hz tuning. I reckon someone is going to be foolish enough to connect up a 5string with no filter and pump 350W through it and i want to keep the speaker intact if possible. Stevie prefers to keep the tuning at 50Hz which keeps excursion down further up the frequency band and a slightly better response overall.

So don't just mess with tuning and think that it's OK, you need to run the models, and realise that designers are making compromises all the time to get a preferred balance of features.

We're actually going to resolve this by building both and listening to the differences and by running some high power tests with test signals.

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[quote name='redstriper' timestamp='1406038450' post='2507746']
My requirement is for a lightweight cab suitable for dub reggae, so I do not need much treble or upper midrange.
I currently use a small cab loaded with an Eminence 3015LF, which sounds good but it doesn't go as low as the new ACME 15" cab.
It would sound better in a larger box, but I don't want to do that.
Stevie suggested replacing the driver with a [color=#282828][font=helvetica, arial, sans-serif]3012LF, which would be better suited to the smaller box dimensions and sound deeper than the 3015LF.[/font][/color]


[color=#282828][font=helvetica, arial, sans-serif]Would anyone else here care to comment on this idea, before I take the plunge?[/font][/color]
[color=#282828][font=helvetica, arial, sans-serif]Specifically, what differences in tone and volume should I expect and is it a worthwhile modification, considering the work and cost?[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Apologies for the derailment.[/font][/color]
[/quote]

if you are serious about building a cab then there are plenty of people here who will have a go at helping you, why not start another thread and see what we come up with

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[quote name='LukeFRC' timestamp='1406071923' post='2508178']
ACME 15"? typo I would think?
Question - and not being fecicious - why not buy an ACME?
[/quote]

Sorry, it should have read ACME 12".
Why not buy an ACME? - Because they are too expensive and also much heavier than my current cabs.

[quote]if you are serious about building a cab then there are plenty of people here who will have a go at helping you, why not start another thread and see what we come up with [/quote]

I am not serious about building a cab - I am considering replacing the 3015LF in my current cab with a 3012LF as suggested above and I wondered if anyone here with experience of this driver may have any comments.

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To the three musketeers, My comments were not meant as a criticism just advice. I hope I did not upset anyone. I have found it a good idea to keep an open mind when it comes to design and i am learning a lot from what you guys are doing.

Much of what I have learnt is from guys like Bill, Alex and Duke, and much of that seemed counterintuitive at the time. Bill on particular continues to push the boundaries on enclosure design.

Keep up the good work.

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[quote name='Chienmortbb' timestamp='1406117220' post='2508451']
To the three musketeers, My comments were not meant as a criticism just advice. I hope I did not upset anyone. I have found it a good idea to keep an open mind when it comes to design and i am learning a lot from what you guys are doing.

Much of what I have learnt is from guys like Bill, Alex and Duke, and much of that seemed counterintuitive at the time. Bill on particular continues to push the boundaries on enclosure design.

Keep up the good work.
[/quote] well you just named it - 3 musketeers 112

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@redstriper

If you want to get a somewhat accurate idea of what to expect from swapping the drivers in your Flyte cabs, you'll need to pop the driver out of one of them and make accurate measurements of the internal dimensions, any volume lost to cab handles etc and an accurate measurement of the port length and cross sectional area - this will facilitate accurately modelling both your existing drivers and the proposed replacement, and give a pretty accurate idea of how the bass response of the cab will change if you made this mod.

Going by opinions of someone who has used the 3012LF is somewhat risky, because if they used it in a cab with different internal volume and porting it will perform differently to the way it will perform in your cab.

Just to illustrate, I have a MAG 1x15 combo, and a MAG 1x15 extension cab with (according to ashdown) identically performing drivers - the internal volumes of the two enclosures and the porting are however very different. If I alternate between running only the combo speaker or only the extension cab without touching the amp EQ, the timbre is a bit different, but the difference in bass response is very noticeable.

Based on external dimensions, my extension cab has a pack space of 120 litres, but after measuring the internal dimensions (84 litres)and subtracting the volumes of port/handles etc the volume of air the speaker actually sees is only 75 litres, so if you want to make a good model there is really no way around doing the measuring thoroughly.

Edited by SubsonicSimpleton

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[quote name='Chienmortbb' timestamp='1406117220' post='2508451']
To the three musketeers, My comments were not meant as a criticism just advice. I hope I did not upset anyone.
[/quote]

Not at all I'm sure - and I think we were in agreement anyway :)
I just wanted to spell out first that driver choice places limitations on flexibility of cab response unless you are able to use complex filters beyond any conventional bass amp, and second that this could actually matter even quite low down. Consider the difficulty of EQ-ing a typical EBS alignment design to flat with a simple filter, even within the nominal passband you will not do it and will typically get a lumpy response when boosting bass. This limits a lot of PA drivers that IMO would otherwise be great for bass guitar, and indeed probably still would be if you had suitable DSP. The nature of the transition to true 4th-order roll-off in a ported cab does matter and there are often advantages to doing it out of passband, which have to be weighed against potential efficiency losses. This isn't just a theoretical issue either, there are plenty of bass and PA cabs out there tuned with a noticeable 'knee' in the low response curve and this does make them more problematic to EQ to a room in my experience.

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[quote name='Chienmortbb' timestamp='1406117220' post='2508451']
To the three musketeers, My comments were not meant as a criticism just advice. I hope I did not upset anyone. I have found it a good idea to keep an open mind when it comes to design and i am learning a lot from what you guys are doing.

Much of what I have learnt is from guys like Bill, Alex and Duke, and much of that seemed counterintuitive at the time. Bill on particular continues to push the boundaries on enclosure design.

Keep up the good work.
[/quote]

No, we won't take offense and it is good to question everything. It's the only way to learn and we certainly don't get everything right, even though we try quite hard to distinguish between opinion and physics.

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[quote name='SubsonicSimpleton' timestamp='1406120368' post='2508501']
@redstriper

If you want to get a somewhat accurate idea of what to expect from swapping the drivers in your Flyte cabs, .........
[/quote]

I was just looking for a rough idea of what the difference would likely be :)[size=4] [/size]

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[quote name='LukeFRC' timestamp='1391642863' post='2359790']
interesting thread from the PA side. Looks a nice driver - I found a pre-fearful greenboy and bill fitzmaurice talking about that 12n630 over on talkbass, but they don't seem to have thomann in the us!
[/quote] The 12n630 seems to have a really nasty peak (12dB approx at 2KHz) and to me that means it is only useful in a 2 way or 3 way system.

Edited by Chienmortbb

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[quote name='redstriper' timestamp='1406149513' post='2508883']
I was just looking for a rough idea of what the difference would likely be :)
[/quote] measure the internal dimensions to get the volume and then plug all the info into WinISD to see what you get. With a new baffle and prosily new/modified ports it'll be a fair bit of work.
Out of interest what are Flyte cabs made of to be so light?

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[quote name='LukeFRC' timestamp='1406154713' post='2508957']
Out of interest what are Flyte cabs made of to be so light?
[/quote]

I suspect it's whatever material is left after Peavey and Trace Elliot have sucked all the heaviness out of it to include in their cabs.

Which reminds me, what sort of quality was the 12mm ply used in the prototype cab builds? B&Q quality or top quality Baltic ply with voids filled with unicorn tears?

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[quote name='LawrenceH' timestamp='1406036918' post='2507721']
This is another reason to think carefully about tuning in the 40Hz versus the 50Hz regions, since tuning lower can give a curve that is easier to EQ within the range you actually care about using the EQ controls found on a typical amp (eg 12dB/oct shelving filters for the bass).
[/quote]

How feasible would it be to have a cab that could be easily retuned, eg. by partially blocking a port if it's shelf-ported?

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[quote name='tauzero' timestamp='1406199885' post='2509219']
How feasible would it be to have a cab that could be easily retuned, eg. by partially blocking a port if it's shelf-ported?
[/quote]

Audiokinesis do this with their Thunderchild and Hathor cabs...round ports though. Fully blocked ports significantly shift the F3 etc upwards according to Duke for his TC cab.

I assume if the cab is designed for it then blocking ports is feasible. I'm sure the 3 musketeers will chip in shortly in regards to this design....

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