ProAc 2.5 Clones - A Couple of Q's

[Blast!]

I have read through the various threads on the ProAc 2.5 clones, as well as the geocities and Troel's web pages and associated papers. I'm ready to tackle this design (my first DIY), but I have a few questions which, I believe, have not been answered elsewhere.

1. In regards to the crossover. I wish to start with a design as close to the original ProAc as possible, and then working from there is I want to tweak the sound. So, my question is - is it the original Chinese crossover that is closer to the original, or the Chinese crossover with Jacq's modifications? It seems clear that Troel's design takes the speaker in a different direction, which I am trying to avoid at the moment.

2. On the geocities DIY site, the CAD .PDF lists the top and bottom of the cabinet as being 25mm thick, whereas the description of construction says 18mm - which is it?

3. Only one dimension is given on the CAD drawing - 189mm, I assume the other dimension is 205mm?

4. Is there any consensus as to where the connector terminal should be located? Closer to the drivers to minimize cabling, or closer to the bottom to avoid interference from driver magnets?


I think I remembered all my questions. Thanks in advance for any advice, and thanks for such a great resource...this forum is a tremendous help!

[tktran]

A1. The Geocities website shows 2 crossovers, and I think it is the one shown at the bottom of the page that's aimed at giving
a sound that is the closest to the commercial ProAc Response 2.5.

This is the Jacques crossover, and includes an optional notch filter to reduce the 2Khz peak.

Is is the same crossover that Troels refers to as the Version 1 crossover in his clone paper, and inclusion of the notch filter makes it the Version 2 crossover. The only differences here is that Troels uses a 7.4uF capacitor instead of the 7uF, but there no other differences.

It must be noted that the recommended crossover is not the same one that was found in the commercial product. It was developed by Jacques. And IFAIK, the "chinese" crossover was found published in a Hong Kong audio magazine, and no one has been able to confirm if a commercial 2.5 actually uses it.

A2. Only front and back panels are 25mm. All others are 18mm

A3. Correct

A4. No real consensus. ProAc places it right behind the woofer , and I suspect, mounts the crossover board directly onto the terminals. IMO it is a question of practicality vs. (real or perceived) performance differences.

[Al.M]

Mr Blast,

With all due respect I must express my frustration at Question 1 because the clone website crossover appears quite explicit to me (yes, I may have written it and are naturally biased) but it says after the 1st paragraph........."here is the Hong Kong magazine crossover" .....and then at the bottom of the page this is the modified Jacq crossover with Troel's optional notch filter. The website needs to be updated as Troel's notch filter is no longer preferred even by Troels himself, Nadir and myself (see the rest of the thread as to why).

With all due respect to the fantastic amount of work done by Troels, myself and several core website creators remain unconvinced of the true sonic value of the various modifications except Jacq's modifications with the standard 8535 & 8515 drivers. Troels various modifications are valid for other DIYers who would have never liked the original commercial 2.5 in the first place. The website will need to be amended to reflect these views and create less confusion for DIYers. Apart from general laziness in correcting the website details, its good that we have waited this long to see the final orbit of Troels papers.

Q 2: The website states that you must recheck the CAD drawing as it contains some minor errors, otherwise what TKtran said is correct. If you used 25mm MDF instead of 18mm (0.5 litres volume) it would make no sonic difference. The humidity in the icy Canadian atmosphere compared to the deserts of Australia might be more important - solution.....a humidity control audio room! - problem, how do we all agree on a humidity %?

Q 3: Not sure exactly what you mean, but the other dimension is 205mm. Are your drawing interpretation skills in order?

Q 4: Crossover behind the woofer is best to shorten cable length. If you position the crossover board here and use 4 long cable terminal connectors (2 for tweeter & 2 for woofer) you punch through and can bolt them securely and directly. Thieves wishing to only steal your personalised diamond studded beautifully hand made crossover, while leaving the rest of the speaker, will be surely cursed. Unless you have arms like an orangutan you will not be able to reach the base of the long cabinet or simply create an access panel near the base, so thats another reason.

Please read the site again, and again and maybe once more to be more sure. I know the website may not be perfect in every last detail, but remember its free and all up to you to make it work. Put your mental energy where it counts. Otherwise enjoy.

TKtran;

You wrote - "It must be noted that the recommended crossover is not the same one that was found in the commercial product. It was developed by Jacques. And IFAIK, the "chinese" crossover was found published in a Hong Kong audio magazine, and no one has been able to confirm if a commercial 2.5 actually uses it."

I am sure everyone will appreciate the sensitivity of this question but the statement is not intirely correct. In the early months of the website creation many real Proac 2.5 owners confirmed the Chinese crossover is the same as the commercial speakers for models around 1998 to 2001 or later. People have only been reporting some minor differences in the woofer capacitor value (8 to 8.5uf) and other speculations about customised and non-customised drivers in real commercial Proacs, which can be found in early discussions elsewhere perhaps still in Madisound.com forum archives 2 years ago, this forum or in Troels' papers.

[tktran]

re. Q4- sorry my mistake. as you can see i was also supposed to write AFAIK (As Far As I Know), not IFAIK.

[Blast!]

Thank-you for the responses.

Al.M

Please don't take my post as a criticism of your site...it is an invaluable resource and much appreciated. The site is explicit as to which crossover is which, however, after re-reading the text twice, it is not clear on which crossover, the original or the one with Jacq's modifications, comes closer to the original sound of the 2.5. I remember reading somewhere on one of the 2.5 threads that the original ProAc had such a peak at 2KHz, which Jacq's modification aims to reduce a bit. Given that it apparently makes little sonic difference, I probably won't worry about it too much.

Thanks for all the other information as well, and once again I will express appreciation for all the hard work done on this design!

[DaHos]

".....and then at the bottom of the page this is the modified Jacq crossover with Troel's optional notch filter. The website needs to be updated as Troel's notch filter is no longer preferred even by Troels himself, Nadir and myself "

Great ! I have been posting on various forums on what x-over is most current and liked......now your telling me that this is not ..........now that I just had it built !!!

Oh.......my head hurts........I sure am glad I mounted the x-over externally..

Well I guess if anything Ill have some extra parts when this is said and done...................

No disrespect but you too have noticed the inconsistancies in the design noted on the site as I also have had to do a few work arounds................

Again I do thank you for keeping the site alive but it would be nice to clear up of few of these "issues"

And also what is the measurment to centerline of the tweeter from edge of cabenit. 74.38mm or 84mm or ?????????????.

Later
D.....

[Al.M]

DaHos,

The website dimension page says about the error on the CAD.....

"Tweeter positioned 50mm from top of cabinet and off set 35mm from side edge (Note: CAD drawing mistake should read 84mm from side of cabinet not 74mm), with 10mm gap between drivers. Woofer located 25mm from side edges or centred in middle of cabinet, 160mm from top. Both drivers are recessed into the cabinet."

The best crossover is at the bottom of the page as I said before, without the notch filter. Troels various modifications have taken it very far away from the original sound so the DIY website does not recognise this, otherwise we would not be able to call it a clone anymore.

[DaHos]

Yep, read it one more time........Well the x-overs and drivers showed up today and the holes are now cut. So I guess Ill know by this weekend........................