Question re. ProAc 2.5 clone

[Dave Jones]

What kind of alignment is that? Compared with the vented alignments in the books I've got, the box is way big. Can the next gen from ProAc (D25) be classified as a MLTL?

http://www.audiophile.com.au/proac_specs/d25.html

How about the 2.5 with the port in the middle?

Here's a quote from the page about the D25:
[quote]
The original cabinet dimensions have been retained, but there the similarity ends. The cabinets themselves, handcrafted and finished in real wood veneers, are extremely rigid and heavily damped as before, but the introduction of a large flared port beneath the plinths gives better interaction with the listening room, making cabinet placement less critical.

[sreten]

Sealed for the driver = ~ 20 litres.
Reflexed / Vented = ~ 40 litres.

sreten.

[Dave Jones]

Originally posted by sreten
Sealed for the driver = ~ 20 litres.
Reflexed / Vented = ~ 40 litres.

sreten.

Could you elaborate? I don't get it. The cabinet appears to be about 56 liters, and it's vented.

[sreten]

Originally posted by Dave Jones

Could you elaborate? I don't get it. The cabinet appears to be about 56 liters, and it's vented.

A quick calculation indicated around 36 litres internal volume.

Another quick calculation indicated external volume is 57 litres.

What does your book tell you it should be ?

sreten.

[sreten]

Personally if building it I'd extend depth and go
for the mildly overdamped red line alignment.

sreten.

[Dave Jones]

Originally posted by sreten


A quick calculation indicated around 36 litres internal volume.

Another quick calculation indicated external volume is 57 litres.

What does your book tell you it should be ?

sreten.

Are your "quick calculations" figuring what the volume of the DIY cabinets actually are, based on the drawings, or are you calculating what some alignment tables tell you the volume of a ported system should be, based on the T/S parameters? -- or what? I am baffled (cough). Go ahead and squander a few words. Typing calms the soul.

The original question was, what kind of alignment is it? Do you know?

[tktran]

I don't know for sure, but I don't think the D25 is a TL.
I *suspect* it would be a QB3 vented box, albeit with the port facing the floor. A bit like subwoofers with downward facing ports.


However the Response 2.5 was a vented box. The internal volume is 34L, with port 75mm (internal diameter) x 140mm long.

[sreten]

Originally posted by Dave Jones


Are your "quick calculations" figuring what the volume of the DIY cabinets actually are, based on the drawings, or are you calculating what some alignment tables tell you the volume of a ported system should be, based on the T/S parameters? -- or what? I am baffled (cough). Go ahead and squander a few words. Typing calms the soul.

The original question was, what kind of alignment is it? Do you know?

20L sealed and 40L reflexed are from the units T/S parameters.

The quick calculations are based on the box sizes.

If its as Tktran says 34L and said port, not my kind of bass tuning.

sreten.

[sreten]

This is more like it IMO,

sreten.

[tktran]

yep one of the ways to extend the bass response of the 2.5 clones is to lengthen the port. gives deeper bass.

the 2.5 and clone has a port configuation that, as sreten correctly points out, gives bass lift from 100Hz to 50Hz, making it sound punchy, and perhaps the illusion of more bass than it really has. - The first time you listen to these speakers you're staring at what seems to be a single 6.5" woofer, playing 8" or 10" levels of bass! You can definitely leave the subwoofer off with this thing!

It's hard to say whether it's right or wrong but I look at it as a pro or con-

This configuations allows you to keep it clear of the front wall (1 metre minimum) thus minimizing early reflections from ruining clarity and imaging, whilst allowing a "muscular bass" presentation.

One of the flat (sretens' last post) or overdamped responses ( sreten's earlier red line alignment) may sound better if you find the bass a bit a little too prominent. I think this may also be of benefit if space or spouse dictates that the speaker must sit against a wall (allows for room gain additive effects).