Alpair 10.2 break-in box?

[mctavish]

So I finally decided on the Alpair 10.2 over the new Seas FA22RCZ and I have a question about boxes. I am in the middle of an overseas move and I have about enough BB ply for two bookshelf sized boxes. I was thinking of just putting the drivers in a couple of 300mm tall x 220mm wide x 220mm deep boxes for the time being so I can start breaking them in. I will build the pensil's when I get settled in Europe. I Thought of putting in some of those Scan-Speak variovents from Madisound to ease the impedance a bit, can anyone comment on whether I am just wasting my time of is this idea OK? Thanks

[loninappleton]

Last break in job I did I used a small cardboard box and a white noise frequency generator (from a free program like Audacity) and ran the break-in unattended at a loud volume. Past tips here indicated that white noise breaks in the driver across frequencies and is not music dependent. So you could use one of your moving boxes like I did.

Alternative to using the computer is tuning in a radio to an unused frequency.

[markaudio]

Originally Posted by mctavish

So I finally decided on the Alpair 10.2 over the new Seas FA22RCZ and I have a question about boxes. I am in the middle of an overseas move and I have about enough BB ply for two bookshelf sized boxes. I was thinking of just putting the drivers in a couple of 300mm tall x 220mm wide x 220mm deep boxes for the time being so I can start breaking them in. I will build the pensil's when I get settled in Europe. I Thought of putting in some of those Scan-Speak variovents from Madisound to ease the impedance a bit, can anyone comment on whether I am just wasting my time of is this idea OK? Thanks

Hi Mctavish.
Thanks for investing in the 10.2's.
Making these boxes could be useful. From your sizes, looks like the box will be around 13 to 14 litres (not sure if you're quoting internal or external). These volumes are OK for running in purposes. Add some internal damping to minimise internal reflection on the rear of the cone. If you're really keen, add a port or vent, block it off for the first 50 hours, open it for the rest of the run-in.

Here's the run-in recommendations: (post 2)

Alpair 10 Gen. 2 introduction

Cheers

Mark.

[Woody1911a1]

funny , mine came with break in boxes

[mctavish]

Thanks for the replies guys. Part of the reason I wanted to build these is for break-in but also to get a bit of enjoyment from them while I wait to get settled and build some proper Pensil enclosures, ( a few months at the least). The dimensions would be external. I would add some polyfill as well and was considering the ScanSpeak Variovents as an alternative to ports or sealed to ease the imp. swings a bit, unless I am mis-informed. Mark, how do these great drivers of yours deal with breakup modes? Is it a function of the special cone profiles or coatings or a trade secret?

[doorman]

Keep us posted on your progress. I've got a pair of 10.2's coming my way soon too, probably going into a a pair of Onken style cabs ie: Mar-Ken 10's.
Best, Don

[markaudio]

Originally Posted by mctavish

Thanks for the replies guys. Part of the reason I wanted to build these is for break-in but also to get a bit of enjoyment from them while I wait to get settled and build some proper Pensil enclosures, ( a few months at the least). The dimensions would be external. I would add some polyfill as well and was considering the ScanSpeak Variovents as an alternative to ports or sealed to ease the imp. swings a bit, unless I am mis-informed. Mark, how do these great drivers of yours deal with breakup modes? Is it a function of the special cone profiles or coatings or a trade secret?

Hi Mc,
I'd be tempted to go vented. What amp(s) do you have? Source?

Interestingly, dealing with cone breakup......Several factors come into play. These include material grade (metal), fibre types (paper), treatments/coatings (paper), cone profiling and the forming process. These factors are usually at the top of the list, but (BIG BUT) there are other aspects that get close to being critical...........

.......For example: the Alpair 12. Cone stability on this driver replies on the rear suspension (spider). The front suspension is ubber compliant. Its so soft that it can't support the cone's mass. Why? Because I needed to reduce the bending moment on the outer profile of the Alp12 cone. In other words, the front suspension must be soft enough not to exert a force that could bend the edge of the cone backwards under mechanical load. From the mechanical point of view, the Alp12 is effectively a "single suspension" driver. As Scott once said to me, "its akin to being a giant ultra wide band tweeter".


I can tell you this, if I could earn just a few dollars for every hour I've spent on cone design, I'd have a descent retirement fund by now (I'm 53 years young).

I'm starting to cover cone design on these threads:

Next Gen 70-mm Markaudio paper cone

Wooden Cone

Cheers

Mark

[mctavish]

Thanks for the reply Mark, I think I speak for many of us when I say that we in the DIY community are truly indebted to you for the devotion you put towards your superior products that the average man can afford. I dont think this will be the last MA driver I buy, and lets face it, being able to ask questions and speak directly with the designer/manufacturer is quite rare these days. I have a TubelabSE with 45's, a P2P copy of a SimpleSE, and a few various other 6V6 and 6BQ5 single-ended amps that I use. Most of these have a highish output impedance and low damping factor. I almost always listen near-field unless company is over ( wife prefers whisper levels). Can you suggest a simple BR for me to knock-up while I wait for the chaos of my move to subside and can build the Pensils? Most of my tools are already on the slow-boat but I can still do a simple pair of small boxes. Thanks again for taking the time.

[planet10]

Originally Posted by markaudio

... looks like the box will be around 13 to 14 litres

13 litres turns out to be the volume choosen to be optimum for the Mar-Ken12. We have built both the Classic GR Mar-Ken12 (plans free on request) and the full-on miniOnken (in a new Trapezoid variation -- not free, not for the faint of heart, but some document beta testers needed)

Both these boxes sound superb.

dave

[markaudio]

Hi Mct,
Dave's Mar-Ken12 plan could be the best bet. I think Dave's ran the Alp10.2's in this box (Dave, can U post pics?).

Otherwise, for simplicity, your 300 X 220 X 220mm box would give you around 13.5 litres? (don't know your material thickness). So for a simple BR, a port say 4cm diameter would be around 11 cm long. The give you something a 1.5dB peak tuned to about 45Hz.......not too bad for a temporary box. Or just make a simple vent at the front/bottom. The letter box opening can go full width X 2cm high. The vent inside the box would be around 4cm long to include your front baffle thickness.

TubelabSE with 45's could sound very nice. Remind me whats its output.

Cheers

Mark.