'LGT' Construction Diary

[Idefixes]

Hi ShinOBIWAN,
All pictures on Perceive v2.0 topics are down. Is there any place where we can take à look at all the pictures you have posted?

Marc

[Tenson]

I'm surprised you have gone for an 8" and a 5"... I think my choice might have been using maybe an 18cm or a 23cm C-Quenze from about 80Hz-1.5KHz instead of splitting it up. Did you not feel 2x 18cm drivers would have done the job okay for extending down to 80Hz?

Still it seems you have ordered now. Very nice design I have to say!

[ShinOBIWAN]

Originally posted by Idefixes
Hi ShinOBIWAN,
All pictures on Perceive v2.0 topics are down. Is there any place where we can take à look at all the pictures you have posted?

Marc

Hi Marc

I've bit the bullet and am paying for image hosting now. This will allow to host all images and not have to keep deleting older ones to make way for the new, you should find that the majority of the images in the Perceive 2 thread are working again. The early ones in that thread I can't fix because they where hosted on a different server but the rest should be OK from about page 30 onwards.

They're pretty spread out though because the thread is quite large. Here's a couple if you can't be bothered to hunt through:

[ShinOBIWAN]

Originally posted by Tenson
I'm surprised you have gone for an 8" and a 5"... I think my choice might have been using maybe an 18cm or a 23cm C-Quenze from about 80Hz-1.5KHz instead of splitting it up. Did you not feel 2x 18cm drivers would have done the job okay for extending down to 80Hz?

Still it seems you have ordered now. Very nice design I have to say!

Hey Simon

A 5" cone covering that range perhaps doesn't have the right weight so you lose some of the slam and impact. Likewise using an 8" crossed to a good ribbon like the RAAL might not offer the same integration that a 5" would with its much light cone mass and higher acceleration factor. I've aimed for effectively targeting each range with a compromise between cone mass and radiating area for greater dynamics, lower distortion and greater headroom. Moving the XO point upto 200hz for the little C-Quenze mid will quite significantly reduce IMD and THD and the pair of larger 8" will be happy running down to 40-50hz. I also wouldn't like to use a side firing sub upto 80hz vs. a pair of 8" rolling off naturally and the sub covering the very bottom.

I've tried to design a full range speaker that still has the virtues of a floorstander such as weigh and solidity through the bass region and also a standmount with its midrange and imaging strengths as well as a subwoofer. I had to weigh this up against the usual problem of size as well as try to best optimise for lower distortion. Whether that will be the case when they're finished is another matter but for now its making sense.

[Idefixes]

Thanks!!!!!

Marc

[ALDO]

absolutely enormous!

[ShinOBIWAN]

Originally posted by ALDO
absolutely enormous!

They did go on a slimfast diet but gave up after someone offered a Mars bar.

[ALDO]

[ShinOBIWAN]

I've been trying to get my head around TS theory and calculations so as to tailor an 8" Flex unit driver specifically for the 40-200hz range. Ideally with a modelled F3 of around 50hz in a 20ltr sealed enclosure. Those are the constraint I have to work with.

I don't want to approach Per with my order until I have something that is actually feasible otherwise I'll just end up looking like an idiot

What I've come up with so far is:

Qts: 3.29
Qes: 0.4
Qms: 1.85
Fs: 25hz
VAS: 40ltrs
Mms: 70g

With this I get the box and driver resonances below 50hz and the impedance phase is smooth from 50hz to 200hz. Its also -3dB at 50hz in a sealed 20ltr box with an over system Q of 0.6.

The other approach was to forget the keeping the box resonance out of the passband and go with something geared for a little more effeciency and lighter mms:

Qts: 3.81
Qms: 1.6
Qes: 0.5
Fs: 33hz
VAS: 40ltrs
Mms: 40g

Any thoughts?

I guess I should really just pick Per brain about this but at least wanted to have something valid to work from.

[richie00boy]

You've either got your Qes, Qms and Qts all mixed up or there's something wrong. Box Q can never be lower than Qts.

I would aim for Qts around 0.35-0.45. Qms and Qes will have to be juggled according to motor and suspension requirements/constraints. It might also be worth specifying a target BL range, I feel a highish (>8) BL gives more slam and control to the sound which is what I think you're after.

As you know your box volume you can then work back to what Vas would give you the desired box Q.

The trouble is a lot of parameters interact. For instance Vas will be influenced by Fs.