Mark Audio Alpair 10.3/A10p MLTL

[Elmojo]

Thanks so much Scott. That's a wonderful explanation, and makes me feel far better about both the drivers and this DATS box.
I had no idea that FS numbers could vary that much. I assumed that they were controlled far more closely, at least on drivers from reputable brands, such as MarkAudio.
It's nice to know that things are operating as per normal, so to speak.
It doesn't explain the odd sound I'm getting from these speakers, but as has been noted previously, it's very likely that the problem is something with my build skills or the Amp/Room setup. At least I've eliminated the drivers themselves from suspicion.

So one question about that drive level thing... is there any benefit to generally increasing it from the default value for standard measurements, or should I leave things at "stock" and just run the numbers? I apologize for pulling this thread off topic. I'm happy to take this conversation elsewhere if that's better.
I'm trying to learn how to use this software, and how to understand what it tells me, and finding it a bit of an uphill slog.

 

[planet10]

Many T/S programs estimate the parameters from the impedance curve measured with a “chirp” or similar. Direct measure means ging in and actually finding the F_s (phase is zero) and then the F₁, F₂ where the voltage falls to half of the V at F_s. These numbers are then used to directly calulate the T/S parameters.

The voltage used to do the measures, the weather (temp & pressure in particular), and more will directly affect the numbers you get.

Smith + Larson WT2 is probably the best non-factory software for measuring T/S. It comes with its own small current amp and measures the actual F_s, F₁ F₂.

dave

 

[planet10]

I had no idea that FS numbers could vary that much.

I have measured mny drivers. And lots of batches of 20 or more. Well QCed drivers have a production variation of about +/- 15% or a bit more, the Mark Audio have been very close at +/- 10%, some brands are much worse, i have had a number were the parameters of 2 nominaly the same driver have been so different that they are not.

Add in the differences from where the T/S are taken off the curves and the differences can be much larger.

dave

 

[Elmojo]

That's good to know, thanks much Dave!

 

[polywine]

i have finally got the draft of the box design from the factory. They want to add a rectagular bracing support at the middle of the speaker, would it affect the design? I follow all dimension posted on page 1

 

[JC Fardo]

Avoid middle, simetrical bracing. Lower that some 3 ins.
and add a second 2 ins bellow the driver. So there's two bracing and no affecting. Cheers.

 

[Elmojo]

Don't forget to account for the volume of the braces in your total internal volume calcs as well.

 

[polywine]

thanks for you both suggestion. I will calculate

 

[polywine]

I am.asking the factory why he suggested to add the bracing. Will.update later. I think its not because of the construction issue. Probably he afraid the box will have unwanted vibration

 

[Elmojo]

What factory? Are you preparing these for mass production?
Presumably you've cleared this with Jim...
I'd be interested to see a prototype of the finished product.

 

[polywine]

Not for mass production. I should write workshop instead of factory. I cannot handle the wood work myself.

 

[JC Fardo]

I am.asking the factory why he suggested to add the bracing.

Hi
Bracing is suggested in post #65

 

[planet10]

The bracing should run vertically. Do not use “standard” window braces, they ar enot nearly as effective and tend to disturb the TL.

dave

 

[polywine]

I remember Jim also mentioned bracing is not really needed for 3/4 inches thick burchy ply wood. I cannot find out which post he mentioned that.

 

[planet10]

It is big enuff that bracing will help, particularly if the baffle & driver are braced against the back can make significant improvements in box performance despite what Jim has suggested.

dave

 

[JC Fardo]

Hi all. It's Just there in the post:

"I use 0.75" or 0.50" square hardwood dowels for braces in designs like this one. Typically I cut pieces of the dowel material so that I have a ring that links front to back and side to side of the box. The first internal brace should be located 1-2" below the driver cutout. This mitigates any excess pressure around the driver and is located near the top of the box as well."

Anyway thanks for clarification. It saves some extra work.

Cheers

 

[planet10]

Dowel helps but is inferior in terms of what is trying to be achieved vrs a brace that connects 3 or 4 panels (ref Tappan). ie push potential resonances up in frequency such that they are unlikely to ever be excited when you are playing music.

dave

 

[JC Fardo]

Fine. Thanks again.

 

[polywine]

I have calculated the port length. It should be like 5 inches in my case. What if i use a longer tube? Would it affect the overall balance? or it just produce a lower bass?

 

[planet10]

It will affect the balance.

dave