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Old 30th October 2007, 03:14 AM   #1
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Default Response 2.5 and 3.8 Clones

I think 2.5 is a great speaker. By far not the best speaker out there but then again, thereís no perfect loudspeaker yet. I canít evaluate it against the original ProAc 2.5 because I donít have anyone close owning a pair. They sound very involving and musical. I am redoing the boxes now in birds eye maple and designing a fancy base to house crossovers. I am curious is to how lower DCR component will affect the performance and if it will be audible at all. Btw, Iíve photographed every step of building a loudspeaker and can post it in a few weeks.
2.5 will probably my first and last clone. 3.8 may be harder to clone because there arenít too much out there in terms of info. I suspect that itís a two and a half way system similar to a Felini-Usher based system in the book by Ray Alden. Second woofer becomes progressively more active at lower frequencies. Itís achieved by adding a 1.5mhz inductor to it. Woofers are wired up in parallel and itís a Linkwitz-Riley 4th order. Without taking apart 3.8 or even sneaking up a look at the crossover topology, I wouldnít know where to start. Not to say that a similar speaker system that is just as good or better canít be build. Itís just not going to be (or may be it will unless of course ProAc decided to be different and used customized drivers again) the same thing. I would just design my own speaker at this point.
Need to save money for Linear X.
Regard, Roman.
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Old 30th October 2007, 01:19 PM   #2
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Hi Roman,

It is too bad you don't have any friends with the 2.5s so you can compare side by side! Did you use Scan-Speak drivers or buy the originals from ProAc? They are supposed to be different!

I guess they sound great! Are they lacking in bass? You mentioned building a Sub?

The 3.8 is a nice speaker but there is no info out there and it would be a shame to buy a pair to dissect them for measurements and build design!

I doubt ProAc would share that info too just yet, but they would sell you the drivers, crossovers, etc.

Well it seems you have done your homework and learned a lot so I understand you moving on from land of the "Clones." I just like when the R & D dollars are paid by someone else!

Have you ever heard the original 2.5s or 3.8s anywhere?

Regards//Keith
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Old 31st October 2007, 12:54 AM   #3
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Hi.
I've heard original 2.5 about 10 years ago, then I was shopping for the speakers. 2.5 was my second choice based on the price but I ended up getting Magnepan because I was mostly listening to solo Violin and Cello.
SS will not sell you customized drivers, they sold to Pro Ac. Nor did they ever published the specs on them. I don't think Pro Ac would sell the crossovers either. Troels has done more then plenty measurements on 2.5 and in the land of the clones it's a clear pass to building a very good sounding speaker. I am building 2.5 mainly for the shop and I will either sell them or give them to a friend of mine then I get tiered of them. I just finished a 5 speaker set up for HT and one of my friend talked me in to selling a pair to him , so may be 2.5 will replace them.
I don't think you would have to dissect 3.8 completely. Crossover should be behind one of the drivers, other wise how would a technician take it out for a repair if it would brake. Box volume could be calculated right there from the front and side wall thickness. Most importantly you would need a brave 3.8 owner who would not faint at the site of someone approaching to the speaker with the screwdriver in hand.
The sub is huge cylindrical enclosure close to 4.5ft3. It's predicted to go down to 14 hz at -6db. Not that anyone will ever hear it but it's just an experiment. It's a HT toy, none of the musical instruments will go that low.
And I am yet to save enough money for Linear X.

Roman
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Old 1st November 2007, 11:09 PM   #4
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If you want the drivers and/or crossovers from ProAc, I can ask the ProAc rep. After buying some new drivers for my monitors, I have gotten to the point with him, where he just might help!

If you come across anything about building the 3.8s please let me know!

Regards//Keith
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Old 2nd November 2007, 02:46 AM   #5
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Thanks Keith. I donít think itís necessary. If you really want that 3.8 may be between all the guys on this forum we could help you design an equally good speaker, possibly the same or very similar configuration. The drivers, used in 3.8 arenít the absolute best. There are other drivers out there that are just as good or better. It all comes down to $$$.
If you start with good drivers and we can all come up with the crossovers, half the battle is won. Thereís no magic to designing a good speaker, just lots of calculations. I have Bass box Pro and X-over Pro and can plug the numbers in. See if you have a friend with Linear X or Clio to measure and tweak the results. Itís not that difficult. Personally I enjoy this part of the process allot.
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Old 2nd November 2007, 09:54 AM   #6
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There is already a thread here on DIYAUDIO about the Response 3.8 with most of the info you're after.
Do a search.
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Old 3rd November 2007, 04:51 AM   #7
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Thank you Andrew!

I have searched on google (probably bad search phrasing) and didn't find much so I assumed there wasn't much here either... NOT!

When I get some other mods completed, I am going to have to hijack Roman's shop! Oh what a treat.

Regards//Keith
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Old 3rd November 2007, 07:24 AM   #8
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we did some investigation a while back here :

Proac response 3.8 crossover

but not much came of it.

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Old 3rd November 2007, 04:12 PM   #9
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Hi Andrew,

Thanks for the hyperlink! I found it yesterday when you suggested doing a search here! I found that and others too!

I would love to have a nice pair of used in mint condition but they seem to be going for $3200 to 3600 USD.

Building an EXACT replica with the ProAc drivers and maybe the crossover would be the next best thing or even better because it would be new. Unfortunately Scan-speak modded the speakers for ProAc specifically and the base model used doesn't sound exactly like it. This also means you cant send the ProAc drivers to Madisound to be rebuilt and get the same thing back even though they use SS parts and training to rebuild the driver. Maybe you can get better drivers these days but sometimes better parts don't mean a better end. Sometimes the recipe is just right with better than average parts and magic happens and the sum is greater, like 8 + 8 = 20!

Also, I wonder if the 3.8 could be improved with out losing any of the good parts, with a modification similar to the new D28. It has a downward facing bass port so a wall behind the speaker isn't required to make these sound balanced with nice bass.

Regards//Keith
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Old 4th November 2007, 06:21 AM   #10
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Really , unless you can order the correct OEM/Industrial drivers from ScanSpeak ( which could be difficult ) it won't be the same speaker.
I've heard the original ProAc 3.8s and they sound VERY NICE , thats why I wanted to clone them myself.......

but , as above...........
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