1x12" Cab Design Diary

[Chienmortbb]

[quote name='tauzero' timestamp='1406199467' post='2509215']


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?
[/quote]B&Q only do baltic birch in 19mm. That is quite heavy ( think MDF on a diet). I don't know but I suspect that it is bog standard 12mm exterior ply.

The Baltic Birch 19 mm is about £75 for a 2440 x 1220 (8x4) sheet. The exterior ply about 1/3 that.

[The fasting showman]

[quote name='tauzero' timestamp='1406199467' post='2509215']
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?
[/quote]Mr Tauzero, not answering your question but I mention this as you are local; the Lichfield branch of Travis Perkins supplied me with an 8x4 sheet with very accurate saw cuts (table saw not vertical) of 12mm birch ply for around £50. That made a 1x15 cab approx the size of a Trace 1153. Hope that is of some use. Prices as of May 2013.
Martin

Edited July 24, 2014 by The fasting showman

[redstriper]

[quote name='LukeFRC' timestamp='1406154713' post='2508957']
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?
[/quote]

Thanks but I won't do WinISD because I don't understand graphs and I have no time to learn.
The internal dimensions are very small, since it is basically the tiniest cab you could possibly squeeze a 15" driver into.
I just wanted a rough idea of what the difference would be if I changed the 3015LF for a 3012LF.
Stevie suggested I should expect more low end and I wondered if there were any other considerations and whether it would be worth the effort and expense.

The Flite cabs are made of a composite material, I'm not sure of the details but I think it's foam sandwiched between thin ply.
They are very light, under 10kg loaded with the 3015LF and having got used to such lightweight, I am loathe to change them.
They also sound better than any other 15" cab that I've tried, which is quite a few, but I've been advised that they are too small to get the best from the 3015LF.

[Chienmortbb]

[quote name='redstriper' timestamp='1406217414' post='2509442']
Thanks but I won't do WinISD because I don't understand graphs and I have no time to learn.
The internal dimensions are very small, since it is basically the tiniest cab you could possibly squeeze a 15" driver into.
I just wanted a rough idea of what the difference would be if I changed the 3015LF for a 3012LF.
Stevie suggested I should expect more low end and I wondered if there were any other considerations and whether it would be worth the effort and expense.

The Flite cabs are made of a composite material, I'm not sure of the details but I think it's foam sandwiched between thin ply.
They are very light, under 10kg loaded with the 3015LF and having got used to such lightweight, I am loathe to change them.
They also sound better than any other 15" cab that I've tried, which is quite a few, but I've been advised that they are too small to get the best from the 3015LF.
[/quote]Give us the inside measurements of the cab and I will model it for you.

[redstriper]

[quote name='Chienmortbb' timestamp='1406227332' post='2509610']
Give us the inside measurements of the cab and I will model it for you.
[/quote]

Thanks a lot, it's 42x42x30 mms, less the space the driver and handle take up.

Please reply by PM so we don't take over this thread

[attachment=167502:Flite cab.jpg]

Edited July 24, 2014 by redstriper

[Phil Starr]

[quote name='redstriper' timestamp='1406217414' post='2509442']


The Flite cabs are made of a composite material, I'm not sure of the details but I think it's foam sandwiched between thin ply.
They are very light, under 10kg loaded with the 3015LF and having got used to such lightweight, I am loathe to change them.
[b]They also sound better than any other 15" cab that I've tried, which is quite a few, but I've been advised that they are too small to get the best from the 3015LF.[/b]
[/quote]

This is kind of what we are saying, all designs are compromises, you like the sound of your cabs because the compromises work for you. Just relax about the cab and enjoy playing bass. Don't worry about the little bit of extra bass that theory tells you you might have had. Our cab has exactly the same compromise.

[redstriper]

[quote name='Phil Starr' timestamp='1406290004' post='2510210']
Just relax........
[/quote]

Thanks Phil, I will take your advice - it's much easier to leave things as they are and I am happier with my rig than I ever have been, after 35 years of trial and error.
It is all about compromise as you say and I've found a compromise that suits me, whilst not being 100% perfect.

It was just people saying that the 3015LF is completely unsuited to the box and that it could even be damaged, that got me thinking.
But it would need to be a considerable improvement to be worthwhile and not just a [color=#282828][font=helvetica, arial, sans-serif][size=4]little bit of extra bass.[/size][/font][/color]

[color=#282828][font=helvetica, arial, sans-serif][size=4]I never push the cabs to distortion and they sound great, despite the science saying they shouldn't.[/size][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][size=4]Only t[/size][/font][/color][color=#282828][font=helvetica, arial, sans-serif][size=4]he ACME 12" sounds better to my ears and I will buy one, if it ever becomes available in a lighter box and produced in this country.[/size][/font][/color]

[Chienmortbb]

OK I have modelled the two Kappalites and there is no doubt that the box you are using is far from ideal for the Kappalite 3015LF.

Your box is less that 50 litres internally and that is ideal for the 12" but the 15" prefers a much bigger box. As is you probably have a small peak at about 100 -120Hz an a steady roll off from sbout 90. In the same cabinet, and with the right porting the same cabinet cold give an extra 6dB around the 40-60Hz area, the area that the Acme's are strong. Ironically the current thread would probably give you better results than the cab/speaker combination you have.

On the plus side, the cabinet you have is small, neat and if it works for you, keep it. I don't think you could install a 12 in this cab without major surgery and I am not sure where you would put the ports.

Are there any ports on the back?

Edited July 28, 2014 by Chienmortbb

[charic]

Chien, if you're trying to post up the results using HTML you're onto a losing battle against the software I'm afraid

Tables don't work in these 'ere parts

[Chienmortbb]

[quote name='charic' timestamp='1406621298' post='2512987']
Chien, if you're trying to post up the results using HTML you're onto a losing battle against the software I'm afraid

Tables don't work in these 'ere parts
[/quote] Ha Ha I have just found that out. I will convert to a jpg and post them later.

[redstriper]

[quote name='Chienmortbb' timestamp='1406458251' post='2511552']
OK I have modelled the two Kappalites and there is no doubt that the box you are using is far from ideal for the Kappalite 3015LF.

Your box is less that 50 litres internally and that is ideal for the 12" but the 15" prefers a much bigger box. As is you probably have a small peak at about 100 -120Hz an a steady roll off from sbout 90. In the same cabinet, and with the right porting the same cabinet cold give an extra 6dB around the 40-60Hz area, the area that the Acme's are strong. Ironically the current thread would probably give you better results than the cab/speaker combination you have.

On the plus side, the cabinet you have is small, neat and if it works for you, keep it. I don't think you could install a 12 in this cab without major surgery and I am not sure where you would put the ports.

Are there any ports on the back?
[/quote]

Thanks very much for doing this for me [size=4] [/size]

[size=4]It seems like you agree that it isn't worth changing the driver for the 12" version, although [/size][color=#282828][font=helvetica, arial, sans-serif][size=4]an extra 6dB around the 40-60Hz area sounds considerable - would that be significant in real life?[/size][/font][/color]

[size=4]​Stevie provided fairly s[/size][size=4]traightforward[/size][size=4] instructions for swapping drivers in this thread:[/size]
[url="http://basschat.co.uk/topic/236510-can-i-improve-my-cabs-at-all-again/page__pid__2447061#entry2447061"]http://basschat.co.uk/topic/236510-can-i-improve-my-cabs-at-all-again/page__pid__2447061#entry2447061[/url]
[size=4]There are no ports on the back and I'm nervous of cutting into the composite construction, but it is a possibility.[/size]

I have 2 identical cabs and it would be very interesting to compare them, loaded with the 3015LF and 3012LF.
[size=4]Apologies again for derailing - perhaps any replies should go on the other thread, here:[/size]
[url="http://basschat.co.uk/topic/236510-can-i-improve-my-cabs-at-all-again/page__pid__2447061#entry2447061"][size=4]http://basschat.co.uk/topic/236510-can-i-improve-my-cabs-at-all-again/page__pid__2447061#entry2447061[/size][/url]

[Chienmortbb]

I have to agree that 3012 might improve matters but I feel the whole cabinet could be compromised. They look good and you like the sound so stay with that for now. Without a lot of work you will not get the results you required and could spoil the cabinets.

[redstriper]

Sound advice Chien, thanks again [size=4] [/size]

[Chienmortbb]

I have just reread the thread about 3 times and apart from realising what a pompous ass I sound, it has been very informative. Firstly the Beyma SM212 driver. I don't know how I missed this driver when searching before but it is a gem, it models really well and I am struggling not to order one now. I will wait until the end of the project though.

Secondly, the choice of 12mm Ply for the cab. This clearly means more work for the three musketeers, but will end up with us all learning more. As the concept is that you can get your wood cut at B & Q, can you confirm what plywood you are using? The standard stuff at B&Q is a fairly medium grade Exterior Ply although they do do Birch and Spruce in 19mm thicknesses only. My first PA speakers were built by my Dad from 12 MM exterior play and properly braced they are great.

Also what wood adhesive?

On the prototype cabs there are a lot of screws around the baffle. The fearful build are screwless, relying on the strength of the adhesive. Why so many screws? Will the design be screwless or is that not part of the design criteria? Hmm just rethoughtthis and realised that you have to have full acces to the interior to play about with bracing.

Edited August 2, 2014 by Chienmortbb

[Chienmortbb]

Ports.

Flared ports supposedly give you an extra 3dB so this should mean you could work with an air velocity of 30+ and not suffer the turbulence we hear as chuffing. However there is only so far you can take this as you cannot fight physics. Precision ports would put about £30 on the project price and that seems to to defeat the low cost of the driver.

Duke Le Jeune recommends a diagonal 45 degree cut on the inner end of a straight port to give a larger area at the port entrance. This adds one port radius (ie 37.5 mm for a 75mm diameter port) to the length of the por but as the air move both ways, this may not be as effective as the correct sized port. At least with a slot port you only have one large round hole to cut.

Edited August 2, 2014 by Chienmortbb

[Bill Fitzmaurice]

[quote name='Chienmortbb' timestamp='1406969848' post='2516273']
Flared ports supposedly give you an extra 3dB
[/quote]They don't. An undersized port can cost you 3dB. By using a flare you can recoup some, if not all, of that loss, but it won't give you 3dB more than a port that's correctly sized to begin with.

[Chienmortbb]

[quote name='Bill Fitzmaurice' timestamp='1406985707' post='2516449']
They don't. An undersized port can cost you 3dB. By using a flare you can recoup some, if not all, of that loss, but it won't give you 3dB more than a port that's correctly sized to begin with.
[/quote]I was paraphrasing the blurb on the Precision Ports site Bill and my worry always was that, as in plumbing, the flow is dictated by the smallest bore in the system. Whilst turbulance may be reduced, the air velocity and c the pressure is still high. So is this treating the sympton rather than the disease?

Edited August 2, 2014 by Chienmortbb

[Bill Fitzmaurice]

[quote name='Chienmortbb' timestamp='1406988177' post='2516470']
I was paraphrasing the blurb on the Precision Ports site Bill and my worry always was that, as in plumbing, the flow is dictated by the smallest bore in the system. Whilst turbulance may be reduced, the air velocity and c the pressure is still high. So is this treating the sympton rather than the disease?
[/quote]When the port is too small there are friction losses; that's what will result in reduced output. That friction, coupled with higher velocity of the air mass vibration than in a correctly sized port, causes chuffing noise. By flaring the port you reduce the friction in that section, and allow a transition from high velocity within the smaller diameter of the port to lower velocity within the flare section, which reduces dB losses and chuffing noise. But if you simply make the port the right size to begin with there are no losses or noise. The obvious question is [i]'why would one make the port too small', [/i]the answer is to reduce cab size. It's the classic clash between what size cab the consumer wants, versus how low and loud he wants it to go.

[Phil Starr]

All good questions. The port issue is really the outstanding detail we need to sort before publishing the design. Exactly the discussions you are having here are going on between us with one extra problem. I'll re read the discussions we have been having and may come back on this but in essence the debate is 'how big a port is big enough?'. More than one formula and more than one target maximum port velocity have been suggested to avoid power compression and port noises. Stevie in particular is keen on flared ports and they do have advantages but I am reluctant to add to the cost and problems of sourcing all the bits and pieces.

The other issues are practical ones. If you make the ports too big they are also too long to fit the cab. Since ease of build is high on the design spec I really don't want to have to fold the port and prefer to use a shelf port. The prototype has round ports because this enables me to vary port area and tuning easily. As you suggest the front and rear panels are removable for prototyping purposes.

Since this is a home build project and an open source design it is a simple matter for people to adapt the construction to their own taste and pockets. We will give enough information for people to go for the ports they prefer and the construction techniques they prefer. My experience is that using screws and glue is more likely to have a positive result where people are working without extensive woodworking tools so i am going to recommend they use screws. I use Titebond aliphatic woodworking adhesives because that's what my local woodworking shop Axminster Power Tools sells, but I also use ordinary white woodworking PVA. I've never had a joint leak or break.

[Chienmortbb]

Thanks for that Phil.One more question then I'll leave you three to finish the design.

Have you tried any other driver in the cabinet? The reason I ask is that modelling them in WinISD Pro Alpha, the Beyma seems to win on almost every criteria. Will that be the defintive driver?

BTW what software is Stevie using for modelling?

[Phil Starr]

I've tried the Eminence delta because I had one laying around, I wouldn't recommend it. We are going to try the Eminence beta 12A-2 which is a much better driver than the old 12A and I hope to get hold of a 3012HO to try. I've cut a load of spare baffles and the speakers are just clamped in so we can swap them really easily so if anyone wants to volunteer a speaker to try.....

having said that the Beyma models well and sounds just how it models so is likely to be what we recommend.

Stevie has three modelling programs, WinISD, one which uses the same engine that Eminence use and another that I'm not familiar with. I'll let him reply. Interestingly they don't agree with each other all the time.

[Chienmortbb]

I know Alex at Barefaced used the 3012HO in some of his earlier designs so it is a good speaker, but whether it is worth the extra £100 over the Beyma, I am not sure. I think the Beyma will have the edge The weight is about 1.3kg lower than the Beyma but at under 15Kg, the Beyma loaded cab is no heavyweight and looks favourite to me. Now I will shut up...maybe!

Edited August 4, 2014 by Chienmortbb

[Chienmortbb]

I did say maybe...... I am just wondering about the power requirements and sensitivity. Phil, what is the amp or amps you have been using in testing? My calcs suggest about 250 watts to achieve 120 dB SPL.
So would you recommend 250W into 8R for one cab and 500W into 8R? I am going to build my own amp soon and may do a similar build diary.

Edited August 10, 2014 by Chienmortbb

[Phil Starr]

For testing I use a PA amp to get a flat response. Usually a Peavey IPR1600. I've been gigging the cabs with my Hartke 3500. My drummer complained that he couldn't hear his snare when I turned it up so I don't think sound levels are a problem.

[Chienmortbb]

I don't think sound levels are a problem Phil but I wanted to be sure I specify my amp at a level that will do the cabs justice.

So judging by your Hartke amp spec 350W into 4R is a good starting point.

Incidentally I have the Sound Check 2 disc and meter that you can borrow if it is worthwhile.

Details here http://www.canford.co.uk/Products/25-244_SOUNDCHECK-2-TEST-AND-DEMONSTRATION-CD-Alan-Parsons

This shows the one without the response analyser but mine has the response analyser included. PM me if interested.

Edited August 10, 2014 by Chienmortbb