I'm going out on a limb here as a new forum member.

I own 4 passive Penta's now. When I bought my first pair (second-hand) I was impreesed by the sound they produce. They've got a big soundstage and sound huge. But after longer listening I found them to be lacking in transparancy and timbre. After finding the specs of these speakers, iI found out that they only reach 20KHz at a -8 dB point. I took them to a speakershop and had them measured, and indeed the high's are tempered, and the bass is a bit boosted (40HZ measured in at +2 dB). That explains their huge sound. But i wanted them to be more precise, more neutral. To achieve this I examined the filter used in the Penta's, and after some calculations and experiments have found a very easy (and reversable!) way to make the Penta's sound more brilliant, sparkling, more balanced in frequency so to speak.

Inside the Penta's at the bottom, there are two PCB's containing the filter. One PCB is labeled No. 14 and the other No. 15. If you short circuit R3 on the PCB No.14 the tweeter in the Penta is no longer held back and the overall sound of the Penta's clears up! They sound much more neutral and livelier.

It's an easy and cheap way to influence the sound of the Penta and best of al. if you don't like the sound, remove the short-circuit and all is as it was.

Just wanted to share this with you

Welcome to the forum, Chasepoes!

You are not alone, the "muffled" high end of the unmodified Pentas has been discussed a number of times. Actually, that mod of yours is suggested in this thread (starts in German, but ends in English) among other improvements.

I believe it is a matter of taste if you like this additional treble or not - but I found the biggest improvement was when I replaced/upgraded all the caps on the crossovers with foil types (MKT). All the passive Pentas are so old now that the caps don't work up to spec anymore, and they weren't of the best quality to begin with.

How much would it cost to get my Pentas recapped? I would do it myself, but Im not too good with soldering or anything like that. They are the active pentas. 

Alex wrote:

Well I won't say 'never', but at present, there isn't really anything which'll consistently outperform them in all areas untill you start spending that amount...

 

EYEdROP wrote:

You mean like upgrading to icepower? 

 Also, my receiver is an older 2 channel 100w yamaha. I am running my Pentas through the pre-out. Im almost certain the L/R channel volume isnt matched. I have a macbook pro which has spdif. I was thinking of buying a modern receiver with optical inputs. Will this solve my channel balance problem? 

I'm not really convinced that 'upgrading' to ICEPower is the way to make Pentas sound better, or indeed any other speaker. ICEPower does sound very good, but only once you've implemented it correctly, and this is very difficult to do. Many mainstream electronics companies can't do it, so I have serious doubts that DIYers can do it too.

A good (very) powerful amplifier will do the trick. It's maybe worth looking on ebay or similar to see if you can get hold of a good quality powerful amplifier. Don't worry about an S/PDIF input, all that does is allow you to use the DAC built into the amplifier instead of the one in your MacBook Pro. I'd get a good quality external DAC instead - the ones built into most surround sound receivers aren't that good. I've just been given an old BBC (Sonic Solutions) DAC/ADC, and it sounds stunningly good - better than my CD7000 which is saying something.

How will a good amplifier do the trick when these are active? Arent the built in amps designed for the specific drivers?

You can pay all you want for various "high-end" caps, but I never was a believer in that magic... I used basic Intertechnik/Audyn MKT caps and I think the final parts list for my passive Pentas was a little over 100 euros. You can get by much cheaper with regular bipolar electrolytics (like the originals) but then you'll need to do it again in 15-20 years 😁

The active Pentas have room for other improvements as well in the amplifier section. I'll let somebody else talk about them.

I browsed through the german thread linked earlier. Im supposed to replace:  

C1 = 4.7 uf,

C2 = 4.7 uf  

C5 = 2.2 uf 

C25 = 10uF

IC2 = LF353  

correct?

 Im not interested in modifying the sound at all, and I intend on keeping original capacitor values. I just want them to sound like new again. Will the new caps clear up the midrange at all? Does anyone know what re-manufacturer B&O is going through for the 8 midrange replacements, or where to get them besides B&O? Also, is it true there are fake midranges for them?

When I recapped my penta's, a couple of years ago, it did show a definate clearing up in the midranges.
Most B&O drivers are rather specific and very hard to replace with generic ones

I don't know about re-manufactered midrange-units. In The Netherlands, the midrange-units can be had new from B&O and cost €32,-  a piece (price of last month), that's about 45 US Dollars. The replacemnt of the foam surrounds is fairly easy to do and rather cheap. I now refoamed 4 Penta's myself (so 16 drivers in all). Materialcosts for 8 drivers is somewhat shy of 40 Euro (55 US Dollar). Foam-surrounds can be found on E-bay and at various websites.