Apogee Acoustics

Just wanted to share. I'm a fairly recent member here. Just got my Centaur Minor ribbons working and had my first listen this weekend. Compared to direct radiator speakers they are very open and clear. I'm using a lower powered tube amp that is extremely revealing and the ribbons really shine with this amp. The only downside is the sensitivity which limits the volume but it's really nice otherwise. I've made ribbons from scratch in the past so I'm familiar with the ribbon sound and I believe I'm going to really like these speakers.

If anyone has suggestions for placement, mods, anything at all, feel free to chime in.

Thank,
John

Hello and welcome,

i think good tube amps and Apogees are a match made in heaven. A friend of mine in the USA drives his Fullranges with tube amps (there are 2 actually) and i drive my Grands with tube amps as well. The crossover components could most likely be improved upon and i would recommend getting another set of tube amps and go active with them.

Hi TinyTim,

Thanks for the advice. I have several tube amps so I could give it a try. For biamping I'd have to rework the crossovers so each driver had separate binding posts, or as you suggest connecting the drivers direct for an active crossover. Since you've mentioned it, do you have some particular recommendations for crossover upgrades?

Thanks,
John

Hello John,

really great capacitors are the "True Copper" ones. Here is a link:

https://www.intertechnik.de/Shop/Cross- ... 68,en,6559

Something really cool would be a 2 way Marchand Tube Crossover.

http://www.marchandelec.com/xm26.html

The most low cost option would be a capacitor and coil upgrade and the ultimate upgrade would be a tube active crossover.

Have fun, and dont let anyone tell you that you need lots of power and transisotrs to make an Apogee sound good. This only, sort of, not really, applies to one model.

Hi,

I would say that active setup for Centaur Minors is really overkill, in fact I think active is overkill for most speakers, unless they are 3 or 4 way like your Grands Flo

The Centaur Minors are good speakers, but you are only going to hear so much improvement in what was essentially a budget Apogee, I don't mean any offence by this but they were I think they were the cheapest speaker Apogee sold along with the Centaur Monitors.

There is a port mod for the Minor to improve the bass - I have emailed you the files. Someone I spoke to recently said they were stuffed with wadding, he removed most of it and said it sounded considerably better for it. Makes sense with the port mod as the air will flow easier.

Upgrading the passive crossover would make quite an improvement and you don't have to spend fortunes. The caps you mentioned are really nice Flo, but would cost more than the Minors I think!

If you want to dip your foot in the water try buying Clarity Cap ESA 0.1uF as bypasses for the current capacitor banks, Madisound sell them (I have no affiliation btw)
http://www.madisoundspeakerstore.com/es ... lene-caps/
All you do is solder them in parallel to the existing capacitors. They alone will give a smoother cleaner sound and make the sound more 3-dimensional.
The Clarity Cap ESA range are about as good as you get for (nearly) sensible money, if you change all the caps for ESA's you will get a considerably richer cleaner sound and it will help the bass balance of the speaker.
Changing the inductors to foil types makes a very big difference also. Make sure to buy the same wire gauge as a step up or down can change the crossover slope.

Also remove the switch from the bass circuit by working out which wires should be directly connected and hard solder them together.
Talking about the wire, the solid core Apogee used is really not that great, worth replacing where you can as it tends to be brittle in feel and sound.

Jon

Jon, are the bypasses applied on both low and high capacitor banks?

Just the one you recommended is not available locally. I see listed the ClarityCap SA and also Mundorf Supreme and Jantzen Audio caps.

What do you think of these capacitor reviews: http://www.humblehomemadehifi.com/Cap.html

About the foil type inductors, what to look for? I'm not familiar with them.

And what internal wiring would be suitable according to you?


About the switches, I studied those before on my Centaur, I suppose the minors wouldn't be much different. For as much as I understand, they do nothing unless switched to Lo/Hi. If removing the ends of wire to the switches make a difference I can't tell.

Hi,

Bypasses are for high and low pass. If you can't get them locally you could buy them from http://www.hificollective.co.uk I don't think they would charge much postage. The SA's are good but I would say the ESA's are well worth the extra money.

The capacitor reviews are a good guide. I can't claim to have tried all the varieties he has, but I do think that the ESA's have a lower grading than they deserve. He talks about the ESA's not having the same openness as I think the Mundorfs, but he doesn't listen to ribbons, I know a couple of people who say the Mundorfs have too much treble, I would say the ESA's are close to flat response, maybe just slightly rich sounding.
I put ESA's in the mid and tweeter circuit of the Synergys and I have never heard such a truly perfect sound.
I have tried other 0.1uF bypasses including the Sonicaps he lists at the same score as the ESA's, and believe me on ribbons I would give ESA's 10 and Sonicaps at best 4.

For foil inductors there are a few manufacturers, I use Mundorf as they are easy to get for me again from http://www.hificollective.co.uk. They are infinitely better than any other type of inductor, swapping from even a good resin impregnated one to a foil just proves they are in another league sonically.

Wiring is tricky as you can pay extortionate amounts for wire, I would say something around 2mm squared stranded copper. I usually use 12 gauge silver plated stranded copper with ptfe insulation. You can buy small amounts from various places, search for 19 x 0.45mm stranded silver plated copper, or 19/0.45mm, it generally costs around £4 per linear meter, Chord use it for speaker cable http://www.chord.co.uk/product/chord-od ... ker-cable/

General quality copper wire is fine, I was just making the point that the stuff in the Centaurs is cheap solid core which has the effect of producing a brittle bass light sound compared to decent quality stranded.

I'm not sure about the switch circuit, but I can tell you if there are 6 contacts on the back:

When the switch is up it connects the middle pins to the bottom pins as vertical pairs
When the switch is down it connect the middle pins to the top pins as vertical pairs

Thanks a lot for your reply Jon. I am going to start with the caps and wiring.

What should I do best with those cable sockets? They look nasty to me. While I was inspecting the X/O filter one already has broken.

I disconnected and measured the switches and indeed they make the opposite connection from the switch position.

What do you think of adding those tiny Vishay caps?

By cable sockets do you mean binding posts?

If so if you are buying from hificollective these are good and sensibly priced and I am fairly sure the hole size is the same
http://www.hificollective.co.uk/catalog ... -4759.html
There are a few variations of these, but the silver ones do look nice!

Lesson in metallurgy - to get gold to stick to copper they normally have to be tin plated first, silver goes on directly so the conductivity is better.

I have tried the Vishays in addition to the ESA 0.1uF. It added a bit more finesse on cymbals and percussion instruments, but it was small, to the point where I don't think I could reliably tell the difference.

Jon I mean the cable eyes clamped on the wires like in the image:





I love how the Apogees render the cymbals. After I've done the ESA's and they are broken in I might just try the Vishay's.

Ah, forgot about those. They are only there for assembly convenience at Apogee, I would just hook the ends of the wires and solder them together, use heatshrink or tape to prevent a short.

I do have some 2.5mm square unused Oehlbach speaker wire. But I'll go try to find the silver plated stranded copper with ptfe insulation. Costs of around €5 per meter would be ok with me.

The caps have arrived and I fitted them in place. I haven't been able to locate the wire so far, but that's no problem. I want to do the upgrades step by step and evaluate and enjoy every increase of it.

About the caps, it is correct they are omnidirectional? I couldn't find any positive or negative indications.

My first impression is, this is a sound upgrade -pun intended. Well worth the effort. And as they break in, the caps should get even better?

Hey Poor guy,

http://www.partsconnexion.com/wire_hook ... ilver.html

This is where I got, and what I used in my Diva crossovers with good results. It does come in white or red even though the link is just for the white.

Give the caps about month to break in and to sound their best, but they will sound great immediately.

Good listening,
Z

Z, they do sound great indeed. More then I expected or could hope for. No careful listening for differences, no guessing for changes. It's right there, in the face.

I've had another look at the X/O, and removed the wires from the switches. This will disable use of the switches. All the switches do is connecting points A and B thus making a shortcut from the filtering components.

(right click, view image)

(right click, view image)


The 20mfd caps sem to have an unusual value. The Clarity Caps can be had as 22mfd but not as 20mfd.

I'm wondering what it would do if the 10mfd cap and the 1,5Ω resistor at about the center of the image are replaced?

And what about replacing the left 10mfd, the one under the row of 20mfd caps?

I do not understand exactly what a foil only resistor is, if someone could give a link to such, it would be of help.

The caps will get better over 100 hours or so, but they sound good from the start as you have experienced

The caps are not directional so don't worry.

You don't have to use the same cap values, just the correct total value, 1 or 2uF either way will not be audible. That way you can get the bigger value caps which are more cost effective, also will take up less space.
Multiple parallel caps do lower ESR (equivalent series resistance) but with better quality caps ESR is lower anyway.

I'm not sure that the 20uF and the 20ohm resistors are in circuit unless the switch is used, can you post or send me a pic of the whole crossover. I have the schematic but it's not that clear.

Jon

Jon, did you right click and selected view image? Here is the full screen pic: http://oi44.tinypic.com/2gucsc1.jpg
Or do you need another viewpoint?

They 22mfd ESA caps are 43 euro each so with 12 caps I'm afraid it's on the wishlist.

That's why I thought of replacing the 10mfd caps with ESA caps.

Sorry wasn't fully awake this morning, didn't click on the pic!

I think the switches are actually essentially out of circuit when you have them normal so they are not really a problem.

I think you must be looking at the 630V ESA caps from that price, you only need the 250V as listed here
http://www.hificollective.co.uk/catalog ... h298344us5

The main capacitor bank is 70uF, the most cost effective way is from a 68uF and a 6.8uF which would be around 55 euros per speaker.
You will get a benefit from just changing some of the caps, especially the 10uF next to the 1.5 ohm resistor as it controls the ribbons upper frequencies.
10uF is around 13 euros, I can save you an extra 10% on the listed prices but it would be plus postage from the UK.

Jon

630V is what the local internet dealer has on offer. The 10's are almost €25 each.
So you can get them for a lot less.
I'll send you a PM about this, see if we can work out something.

By the way, when the main capacitor bank totals 70mfd, wouldn't 68mfd + 2.2mfd be the best option?

Yep, you are right, had 75uF in my head from working on Divas!

A little downside of the improvement is, it is ruthlessly exposing the electronic gadgetry often applied to the vocals.

Apart from that, I'm still amazed by what more is revealed from the music and that the Centaur potential apparently has not been fully exploited.

What I'm curious about is, did Apogee build a crossover below their possibilities, or has the quality of parts increased so much since the Centaurs were build, or do the parts in the crossover degrade during 20 or more years?

By the way, this should be the Centaur XO:

Rather than replacing the (costly) inductors, just use transformer varnish or epoxy and pot the existing coils. The majority of degradation of sound caused by Apogee inductors is because they are loosely wound and the coils can move in response to the current thru them.

You will get 90% of the improvement from pricey replacements, without any risk of screwing up the tonal balance.

Thanks for the suggestion EldRick. I know this is a trick the installers are performing on upgrades, so it should be worth the trouble. I have to dig into it to find out if and how I can do it.

According to Jon the resistors are not that expensive. For a start, I want to replace only two of them.

EldRick about the potting, would this apply to all the coils, the ones on the image above and there's a big one in the case?
Is the epoxy fluid enough to sink into the depths of the coils?
I suppose it's not hard to do but I can't find any guide on the internet.

Vansloneker wrote:By the way, this should be the Centaur XO:

What is the point of the two 20 Ohms resistors bottom right on the image?
Isn't it so that when two resistors are placed in parallel, the effective value is half of the combined value of the two? So then why two 20 Ohms resistors and not one 10 Ohms resistor?

Anyway do I read correct from the drawing (right click, view image) these are only effective when the switch is set to 'Hi'? Or is it the other way?

Looking at the back of the Centaur, the woofer switch positions are 'Norm' and 'Lo', not 'Norm' and 'Hi' as is shown in the drawing.

It's only effective when set to "Norm" as part of the current then are paralleled with the bass and thus goes through the capacitor and the 2 resistors.

And yes, the 2 resistors will equal 10 Ohm but both will only have to take care of half of the current through them and does not need to have as high Watt ability as a single one would need to have.

Cheers!

Right now I'm working on potting the coils. In another topic EldRick posted a link to his work Duetta Signature Innards. He's writing about 'air core' coils which made me thinking. I went the hard way and took the coils all out, then put them in a mould and poured epoxy over them. Because of the considerable weight, and because at a later date I may want to move the X/O external, I bolted them into position.



No I'm having doubts, maybe the center of the coils should be free of epoxy? But if the coils are surrounded there's no air there, so what difference does it make?
And, maybe I should not have a large steel bolt going through the center of the coils?
I can drill away the center of the epoxy but then I'd have to glue the coils into position.

Use NON magnetic bolt!!! Or else You will get higher inductance.