General Forum

Re: B&O Penta owners will want to bookmark this!

Dillen — Thu, 26 Aug 2010 17:21:19 GMT

I agree.
There's some serious filtering going on there.
Bang & Olufsen didn't mount all those expensive components just because
they've accidentally ordered too many.
Put a Penta speaker through a monitored frequency sweep, change a driver or
a filter component and see if you can make them any better.
I think, you'll be surprised.

The amplifier is one of the best from B&O. Discretely built and still housed
in that little box. Even the transformer has been fitted in there.
Technically, there's very little to improve, even with modern components and
todays techniques.
The signal path capacitors and operational (pre-)amplifiers can be replaced
with better modern types but that's about it. Not much for such an old construction.

I respect the Penta speakers very highly.
B&O managed to put a speaker together that sounds great, packs a fair
party punch while providing an almost completely flat frequency response.
Even the design is timeless.
Mainting the Penta's as you would anything else you like, and you'll have
superb speakers for a long time.
Neglect them and you will have speakers with dead amplifiers, dried out cross-over
capacitors and drivers with foam rot.
This is often the case when people put them down these days. What they are judging
are the owners level of maintenance rather than the engineers creations.

I feel that many owners simply forgot what they bought, what they sounded
like when new.
They are wonderful speakers but as everything else of this nature, they do require
a bit of attention from time to time.

Martin

Re: B&O Penta owners will want to bookmark this!

Jon — Thu, 26 Aug 2010 16:39:00 GMT

Dillen:

So this thread basically covers how Penta owners can get rid of

- The original amplifier
- The original drivers
- The original crossover design

But the Bang & Olufsen logo on them is pretty cool, huh ?

Martin

That's pretty good Martin.

Yeah, it was really late when I replied to this thread (way past bedtime), and I was going to say that I think it would be a mistake to alter the X-over in any way. There's definitely some complex response shaping going on here, and by arbitrarily deleting part of that, you're only going to mess things up.

Jon

Re: B&O Penta owners will want to bookmark this!

Dillen — Thu, 26 Aug 2010 06:58:42 GMT

So this thread basically covers how Penta owners can get rid of

- The original amplifier
- The original drivers
- The original crossover design

But the Bang & Olufsen logo on them is pretty cool, huh ?

Martin

Re: B&O Penta owners will want to bookmark this!

Jon — Thu, 26 Aug 2010 06:26:37 GMT

snoopy:

Can anyone explain the mid-range part of the crossover? It's very complex ...

In my judgement ??? :

L1, C1 does the basic filtering

R1 controls volume

L2, C2, gets rid of any minor left over signal

L3, C3, gets rid of any minor left over signal

C4, R2, L4, C5, matches impendence (zobel network)

Basically I'll be getting rid of the entire last part of the network for my new mid-range units. I'm wondering what else before the last part will colour the sound, that is, was stuck in to compensate for the original crap mid-range drivers.

Andrew

I know this is a year old...sorry.

Just a quick look at that crossover (and I'm by no means the best at reading schematics...) - looks like there's trap circuits and impedance compensation circuits in there.

Are you talking about getting rid of L5 and C8? Looks like some kind of bandpass filter.

My guess (without trying to figure the X-over out) is that the outer two units' response rolls off at a lower frequency than the inner two units. This is done to avoid comb-filtering artifacts in the response, when the wavelegths get to be smaller than the center-to-center spacing of the drive units.

That way you get the extra radiating area and, hence, efficiency in the lower range of the midrange's passband without the comb-filter cancellations higher in the response.

Jon

Re: B&O Penta owners will want to bookmark this!

EYEdROP — Fri, 28 Aug 2009 13:03:11 GMT

I could definitely use those drivers, but I live in the USA.

Re: B&O Penta owners will want to bookmark this!

snoopy — Sat, 25 Jul 2009 03:10:42 GMT

The procedure is complete. It required a bit of drill action (acting as a grinder) on the inside plastic to allow the huge magnets to fit, but it didn't compromise the enclosure.

At first the sound was more accurate but didn't have that "edge" the Penta's seem to be able to do.

Then I realised by removing the last part of the mid-range crossover I had shifted the phase 180 degrees. I reversed the polarity of the leads and ...

I would love to pitch these against some 5's now. I actually reckon they'd win!

I ended up going for the FRS8M's instead of the less sensitive model. The other ones have a real flat response, less power handling and would have fitted straight in, and my Penta 1's use a 3.3ohm reduction (the 2 & 3's use 2.2ohm) so the M's looked the better bet.

Incidently, the original mount brackets for fitting the original mid-ranges fit perfectly without modifcation. A nice surprise.

Re: B&O Penta owners will want to bookmark this!

cooldude — Tue, 21 Jul 2009 17:27:38 GMT

snoopy:

These are being raves about on diyaudio. They are very sensitive with a relatively flat response.

http://www.impactaudio.co.uk/product.asp?ref=921&session=a066a144c371c06b922752ca770e9472

I'm buying 8 of 'em and shall report back.

I have decided that the Rl140's do not sound as good as the Pentas even though the mid-range is better quality. They don't have the depth and the treble is overblown and inaccurate. Sonically the Pentas are significantly better. I'll be selling my converted Rl140's...

It is bit of an unfair comparison as the Redlines were never meant to be on the same level as the Penta's (not in bass, power, size, drivers and price).

I have used visaton drivers before with excellent results and I can recommend them.

Re: B&O Penta owners will want to bookmark this!

snoopy — Tue, 21 Jul 2009 15:44:56 GMT

Can anyone explain the mid-range part of the crossover? It's very complex ...

In my judgement ??? :

L1, C1 does the basic filtering

R1 controls volume

L2, C2, gets rid of any minor left over signal

L3, C3, gets rid of any minor left over signal

C4, R2, L4, C5, matches impendence (zobel network)

Basically I'll be getting rid of the entire last part of the network for my new mid-range units. I'm wondering what else before the last part will colour the sound, that is, was stuck in to compensate for the original crap mid-range drivers.

Andrew

Re: B&O Penta owners will want to bookmark this!

snoopy — Mon, 20 Jul 2009 06:05:21 GMT

These are being raves about on diyaudio. They are very sensitive with a relatively flat response.

http://www.impactaudio.co.uk/product.asp?ref=921&session=a066a144c371c06b922752ca770e9472

I'm buying 8 of 'em and shall report back.

I have decided that the Rl140's do not sound as good as the Pentas even though the mid-range is better quality. They don't have the depth and the treble is overblown and inaccurate. Sonically the Pentas are significantly better. I'll be selling my converted Rl140's...

Re: B&O Penta owners will want to bookmark this!

snoopy — Mon, 20 Jul 2009 05:49:09 GMT

I've just done research to find out some stats on the mid-ranges, finally found out ITT was sold to Nokia after 15mins, then read your last post - doh!

The RL140 mid-range is Nokia as well - it seems B&O used the same supplier for high/mid/bass, so perhaps finding out the bass wouldn't be too hard.

I have decided to get 4x 8ohm speakers and do series/parallel - I'll then modify the mid-range portion of the crossover to eliminate the 2-way section on the mid-range - I don't see the point in that arrangement (very odd imho).

Re: B&O Penta owners will want to bookmark this!

ouverture — Fri, 17 Jul 2009 14:37:10 GMT

Morel drivers are really good too

http://www.morelhifi.com/products/raw_drivers.html

specifically the model MDM 55, I have a friend in New York who replaced all 8 of his Nokia midrange drivers with Morel MDM 55 drivers, you have to remove the square flange to fit them into the Penta holes left by the Nokia units though

he went mad and bought more Morel, woofers and tweeters ( 18 new Morel drivers for his Penta's )

sounds absolutely fantastic though !

Re: B&O Penta owners will want to bookmark this!

ouverture — Fri, 17 Jul 2009 14:34:26 GMT

call Wilmslow Audio

http://tinyurl.com/kunaf7

they are really good suppliers for that sort of thing

Re: B&O Penta owners will want to bookmark this!

snoopy — Mon, 13 Jul 2009 14:13:32 GMT

Regarding replacement mid-range's has anyone done it? I can't find any 3" mid's in the UK and postage would be expensive. I found these, not sure if they'd fit because of the large back (I haven't checked the mid-range cover for the Penta).

http://www.madisound.com/catalog/product_info.php?cPath=45_228_255&products_id=8459

If I were to get one I'd wire two in series, two in series and parallel them to give 8ohm nominal. Unsure if this is correct ...

Re: B&O Penta owners will want to bookmark this!

EYEdROP — Mon, 01 Jun 2009 14:12:25 GMT

A word of advise to people running Pentas with the line-in pre/out on a non B&O receiver: Make sure you check out your receiver manual for the pre-out voltage. On the penta, you have switch III =1v, switch II= 1-1.4v, switch I=1.4-onward. My Yamaha receiver has 1v pre-out, but I had the switch set to the III when I should have set it to II.

Setting the switch correctly really cleared up the midrange and I hear less distortion. It seems like having the switch on the III position emphasized the upper midrange too much and added artifacts. On II, everything clears right up. These speakers sound fantastic.

Re: B&O Penta owners will want to bookmark this!

snoopy — Thu, 28 May 2009 04:43:14 GMT

My RL140's are up and running. Reforming the speakers was really easy. Three didn't need any adjustment with the form and could be glued right on. The other took a minute!

Still breaking the woofers in, but comparison to the Pentas (RL's on additional B&O stands) the bass is weaker. The mid-range is better and top is more sparkly however they don't sound as good, or should that be "refined" as the Penta.

Together the performance is magical, the RL's complement the Pentas weaker mid-range, the Pentas complement the RL's weaker bass.

Total cost... approx £1,000 for everything. Pictures coming up...