1x12" Cab Design Diary

[Chienmortbb]

The midpeak on the SM212 is less pronounced than either of the Kappalite 12" speakers. I wonder why is it so obvoius here? I can understndthat the 3012LF may be cossed over at 1-2KHz meaning the peak is missed or at least tamed. However the 3012HO peak is much closer to 1Khz and that has been used in a number of commercial cabs.

I understand that mids reflect off the rear of the cabinet and come through the cone but does that also mean that they bounce back through forward facing ports? I am sure I read that Audio Kinesis put their ports on the back because of this but I may be remembering incorrectly.
If so that is correct, might there be some reduction with a slot port?

Dood, can you compare this to any commercial cab you have reviewed or used?

Edited July 30, 2015 by Chienmortbb

[Chienmortbb]

Dood said "[color=#282828][font=helvetica, arial, sans-serif]Engaging the bright switch and setting the passive tone stack to that classic scoop setting (all controls pointing up) tamed the cabinet. A little bit of excess cone movement - but I think the Kilo has absolutely no subsonic filtering. "[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Do you think that and HPF should be fitted to al amps? The amp I am buiding has an adjustable one and the more learn about speakers, the more I am convinced they are vital.[/font][/color]

[Beer of the Bass]

Is it a 2KHz upper-mid peak that people are hearing, or does the mid-forward character happen lower down? Could it be down to the cab having a relatively even response, where the lack of a bump around 100Hz and the relatively well controlled upper-mids make the content around 4-500Hz seem more noticeable than on most cabs? Not having heard it this is just a guess.

[alexclaber]

The on-axis plot on the data sheet does suggest it'll sound moderately midrangey, based on how 12" drivers with that kind of construction behave off-axis. Likewise it won't sound hugely trebly. Considering the relatively low inductance voice coil I think the cone itself must be relatively soft yet heavily damped for a paper cone.

The other thing is the harmonic distortion - if compared to the norm it has more harmonic distortion in the mids than the lows then they'll sound more prominent, especially if it has more odd order distortion in the mids and less even order in the lows.

[Phil Starr]

[quote name='Chienmortbb' timestamp='1438288418' post='2833357']
Dood said "[color=#282828][font=helvetica, arial, sans-serif]Engaging the bright switch and setting the passive tone stack to that classic scoop setting (all controls pointing up) tamed the cabinet. A little bit of excess cone movement - but I think the Kilo has absolutely no subsonic filtering. "[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Do you think that and HPF should be fitted to al amps? The amp I am buiding has an adjustable one and the more learn about speakers, the more I am convinced they are vital.[/font][/color]
[/quote]

This is pretty much always sensible, the speakers excursion at frequencies below its resonance can exceed safe limits and distort heavily at a few 10's of watts.

[Phil Starr]

[quote name='alexclaber' timestamp='1438293691' post='2833425']
The on-axis plot on the data sheet does suggest it'll sound moderately midrangey, based on how 12" drivers with that kind of construction behave off-axis. Likewise it won't sound hugely trebly. Considering the relatively low inductance voice coil I think the cone itself must be relatively soft yet heavily damped for a paper cone.

The other thing is the harmonic distortion - if compared to the norm it has more harmonic distortion in the mids than the lows then they'll sound more prominent, especially if it has more odd order distortion in the mids and less even order in the lows.
[/quote]
Thanks Alex, you are right about the cone. I set out to look for something well damped but soft enough to have a decent output at the top end. The trade off for using a single speaker I guess.

You may be right about the distortion aspect, we simply haven't investigated as yet. The bass is very open sounding and with this tuning has no real upper bass hump. The 2kHz peak is fairly normal for most speakers and less pronounced than many Eminence units used for bass, at the top end this driver has more output between 3-5kHz than most of its competitors in the price range, something I saw as desirable. I wanted something which would give a flat response which would respond well to eq tweaks and sound good when used with amp modelling patches which people are increasingly using. At the same time I wanted to avoid a ruler flat response which without a tweeter would sound completely lifeless, as I discovered with an earlier design.


The sound isn't unpleasant, it's very open sounding and the bass seems effortless. The midrange character is there but not overwhelming in my eyes, but I practice with headphones a lot so I'm used to having all my little errors right out there Played live it rewards digging in and I'm getting some Martin Turner/Wishbone Ash tones out of my American Deluxe P bass which startled me the first time it happened. My main concern is to understand what is causing the comments so I can design this in and out with later cabs. My feeling is that the comments lie with the comparison most people will make with the commercial cabs they are used to, but you have given me something else to think about which is really helpful.

[quote name='Beer of the Bass' timestamp='1438292037' post='2833404']
Is it a 2KHz upper-mid peak that people are hearing, or does the mid-forward character happen lower down? Could it be down to the cab having a relatively even response, where the lack of a bump around 100Hz and the relatively well controlled upper-mids make the content around 4-500Hz seem more noticeable than on most cabs? Not having heard it this is just a guess.
[/quote]

Well this is my current theory, more or less. The cab sounds very much how I designed and expected it to sound with a flatter response than most commercial cabs which would open out the detail of what you play. With bass and top end resonances tamed in comparison to many cabs mids are bound to be more forward but I'm taking the comments seriously so I can make recommendations. Dood has agreed to try the 50Hz tuning which does have a bit of a 100Hz bump and we need to get back and take a few more measurements and experiment a bit more with eq.

Edited July 31, 2015 by Phil Starr

[Thunderpaws]

Hi Phil,

On a slightly different note, does the design have bracing to the back panel of the cabinet from the sides, or is it only that cross shaped structure to stop the sides of the cab moving in and out?

[Phil Starr]

The prototype back only has the 'vanes' shown in the photo, they line up with the other cross braces so could be braced against each other, but whilst prototyping I like to gain access through the back. Like all small cabs there isn't anywhere to brace to on the baffle as the speaker and ports take up most of the front

[Chienmortbb]

How much extra bracing will the slot port give. Will it make room on the baffle for more bracing?

[Phil Starr]

Not really, it slightly reduces the size of the baffle. It is intended to make it out of thicker ply to keep the construction simple. However Its up to constructors to add whatever bracing they want, that's the joy of home building. There's already enough data here for anyone to build the cab if they already have basic carpentry skills.

[Dood]

[quote name='Chienmortbb' timestamp='1438288418' post='2833357']
Dood said "[color=#282828][font=helvetica, arial, sans-serif]Engaging the bright switch and setting the passive tone stack to that classic scoop setting (all controls pointing up) tamed the cabinet. A little bit of excess cone movement - but I think the Kilo has absolutely no subsonic filtering. "[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Do you think that and HPF should be fitted to al amps? The amp I am buiding has an adjustable one and the more learn about speakers, the more I am convinced they are vital.[/font][/color]
[/quote]

I absolutely do yes - Whether or not it should be switchable is another question but certainly getting rid of everything under even 25Hz makes a difference to flappy cone syndrome! Maybe an adjustable filter for use with different cabinets? I used to filter a 2K amp running in to a 400W RMS hartke cabinet. The cones never flapped and I never blew anything even with a full band who were not..err.. volume conscious ha!

[Dood]

[quote name='Beer of the Bass' timestamp='1438292037' post='2833404']
Is it a 2KHz upper-mid peak that people are hearing, or does the mid-forward character happen lower down? Could it be down to the cab having a relatively even response, where the lack of a bump around 100Hz and the relatively well controlled upper-mids make the content around 4-500Hz seem more noticeable than on most cabs? Not having heard it this is just a guess.
[/quote]

I have to say that no, it's not 2Khz for me. I haven't tested with RTA or anything but using my knowledge of electronics test gear, experience in the studio and being an uber gear geek, I can say with certainty that the midrange peak that I was hearing was much lower. I'd actually say 2Khz is more in to the treble regions than even high mids.

I'd actually agree with what you are saying. Without the tweeter and a roll off of the lows, what is left is plenty of low mid range and mid range. It was less of a 'boxy' midrange sound though unlike some boxes I've tried.

[Dood]

[quote name='Chienmortbb' timestamp='1438287506' post='2833347']
Dood, can you compare this to any commercial cab you have reviewed or used?
[/quote]

There certainly are similarities with some cabinets I have used or reviewed in the past but it'd be an unfair comparison at this stage. Also, the cabinet I took with me to the studio of my own to run up my 'usual rig' would be an unfair comparison.

What I will say though and I appreciate what the point of this project in the first place is so possible outside the remit; If you are looking for a clear 'non-vintage' tone then I think the cabinet will need a midrange driver or a super-tweeter. If you are thinking of using lots of grit and want to make use of the speaker's natural roll off to soften the filth tone as not to sound brittle then this could work out pretty well! For me personally, I wouldn't apply cab sims (think Kemper / AxeFX / POSITIVE GRID) as the cabinet has a flavour of it's own that may give you unacceptable results - read as 'mushy'. Using distortion pedals and amplifier sims though I think this cabinet could do really well - especially in multiples stacked. Almost taking things from a guitarist view point who prefers to use his valve amp and cabinet configuration to create smooth distortion.

Edited August 1, 2015 by dood

[Chienmortbb]

So what do you consider a super tweeter. I am not asking for a particular technology rather what the frequency response of a good tweeter is. Also is there an argument for a Low Pass Filter before a tweeter?

I wi be honest, putting a tweeter in a bass cabinet that extends to way over 20KHz seems crazy to me even fior slapping. So any ideas on what the top -3dB point should be for a tweeter?

I have no real opinions myself, just trying to learn from other people.

[Dood]

[quote name='Chienmortbb' timestamp='1438454880' post='2834665']
So what do you consider a super tweeter. I am not asking for a particular technology rather what the frequency response of a good tweeter is. Also is there an argument for a Low Pass Filter before a tweeter?

I wi be honest, putting a tweeter in a bass cabinet that extends to way over 20KHz seems crazy to me even fior slapping. So any ideas on what the top -3dB point should be for a tweeter?

I have no real opinions myself, just trying to learn from other people.
[/quote]

I would suggest a tweeter that reaches downward to overlap the top end of the 12" driver rather than heading toward the stratosphere. A filter network can then be customised to better cross those points rather than a generic tweeter not being able to meet the 12" high output leaving a weird gap.

[Thunderpaws]

[quote name='Phil Starr' timestamp='1438354617' post='2833868']
Not really, it slightly reduces the size of the baffle. It is intended to make it out of thicker ply to keep the construction simple. However Its up to constructors to add whatever bracing they want, that's the joy of home building. There's already enough data here for anyone to build the cab if they already have basic carpentry skills.
[/quote]

Can anyone point me to the posts in the thread that explain correct dimensions for the cab? I am obviously blind. Silly me. Or if it's the volume of the can that counts and dimensions are min and max can someone put a summary up so it's really easy to find.

Thanks,

Garry

Edited August 2, 2015 by Thunderpaws

[Phil Starr]

Hi Garry, the dimensions are here somewhere but I couldn't find them amidst the hundreds of posts either. I'm down in Cornwall this week on holiday. Playing music with an old uni friend mainly so I don't have measurements with me, but I did bring paper and stuff to do some sketches for you. So long as there aren't too many music pubs in St Ives I should have an update soon.

[Thunderpaws]

Have a great break. Sketching on the beach?

[Chienmortbb]

post 349 gives the dimensions

[Thunderpaws]

Nice one.

[Phil Starr]

Quick update, just spent a couple of hours playing with speakers and basses with GrahamT of this parish. What a lovely guy.

Anyway amongst other things we compared the Basschat 12 with a Genz Benz focus 12, the first time I've been able to AB with a commercial cab. Volume levels were very similar. Surprisingly the Genz had a prominent upper mid compared to the Beyma loaded cab (with the tweeter turned off by the way) as well as a bass peak in the 100Hz region the Beyma going deeper and tracking the bass more accurately but the Genz having a pleasing warmth to it. The Beyma was much more even in sound across the strings and frets.

We tried the speakers with a Harke HA3500 and a Genz Streamliner 600 and the influences on the sound of the two cabs were pretty clear with both amps.

I'm not sure where this thing about the mid prominence of the Basschat design is coming from, I've heard it and so have Stevie and Dood but it doesn't show in the measurements and didn't show in this test either. I'm hoping to get back to the measurement room with Stevie to work out what we are looking at.

[Dood]

[quote name='Phil Starr' timestamp='1439986442' post='2847253']

I'm not sure where this thing about the mid prominence of the Basschat design is coming from, I've heard it and so have Stevie and Dood but it doesn't show in the measurements and didn't show in this test either. I'm hoping to get back to the measurement room with Stevie to work out what we are looking at.
[/quote]

I think - no, I am pretty sure I know what it is we are hearing. It's not 'mid peaks' we are hearing, more mid presence. Its a lack of deep (sub) lows and rounded off top end that gives the sense of a prominent mid range - especially when the lil' chap is placed on the floor and we stand over it. The effect I have found to be similar on the odd cabinet I have reviewed that allows the ability to turn off a tweeter. This appears to be less prominent on a cabinet that has a naturally baked in scooped tone (either through speaker, cabinet design or both.) So, I'd suggest that this speaker is actually doing a good job of reproducing frequencies throughout the mid lows, mid range and low mids, but it's natural roll off gives the impression of having a mid boost. This would seem to support my feeling that this speaker would be great as a mid-bass driver in a multi-driver set up. This is of course outside the remit of this project. Thumbs up for the sensitivity through the mid range though. I do like that this cabinet and speaker combination offers a really nice fatness all the way up the G string of my bass, rather than the notes disappearing in an EQ's scoop.

[Dood]

Free the BassChat 12!!

[Dood]

Sorry, just felt the need to say that.

[Phil Starr]

[quote name='dood' timestamp='1439987604' post='2847273']
Sorry, just felt the need to say that.
[/quote]