Opamp requirements for Crossovers

[Anders_denmark]

Hi everyone!

I have been thinking about building a 3-way 4th order LR Crossover using the diagram from here:

http://sound.westhost.com/project09.htm

My question is regarding the opamps. I have about 20 opa627 but is it overkill to use this opamp for a crossover? Any opinions?

As an alternativ I would maybe use the OPA627's as buffers and find cheaper opamps for the actual crossover.

Any comment on the general crossover design will also be appreciated.

Best Regards
Anders

PS: Sorry if it is the wrong forum, but I guess: opamp = chip-amp

[pinkmouse]

Originally posted by Anders_denmark
... but I guess: opamp = chip-amp

Wrong! Thread moved.

[AndrewT]

Hi,
is the 627 unity gain stable?

Using existing stock is always cheaper than buying in new devices.

[parsecaudio]

AndrewT
the OPA 627 is unity gain stable and the OPA 637 is stable for a gain of five or greater.

My advice for high quality crossover op amp is the LT1028,very good but expensive...

[AndrewT]

Hi,
the ESP article is good.
Use the alternative connection for the bass low pass shown in Fig 1c.
Add output buffers and gain adjust to your most sensitive Amp/Driver combinations.

Be prepared to be disappointed. You may/will have to add equalisation and notch/boost filtering to get a smooth output from your drivers.
A digital xover may help with this part of the design process.

[preiter]

I made mine with OPA2134s, it sounds great.

[sletol]

No need to use expensive op amps in the low pass section, IMO.

[georgehifi]

Anders this is the circuit you are looking at with everything to build your own even to etch your own circuit board

http://www.siliconchip.com.au/cms/A_30278/article.html

I've used it as a two way and tried every concievable chip properly implemented for max performance now, and the best quad chip was the OPA4134 by far, but still after all that I ended up using the mids/highs passively.
After all the experimentation with the sound of opamps, nothing sounded better in the mids and highs as the passive network, good opamps seem to be well controled clean and articulate, but they loose all the timber and ambience and richness compared to passive networks, that why in the end I only used the active for the bass and drove the mids and highs with the good passive xover.
I'll proberly get ear bashed for this statement and I don't care because if you have a pair of good ears they will tell you the same.

Cheers George

[AndrewT]

Hi George,
is that telling us you have a low pass feeding the bass driver?

and that you are sending a wideband signal to the mid/treble amplifier which in turn is sending a wideband signal to the passive crossover?

What happens to the bass information in the wideband signal that gets into the mid driver?

Or have I mis-interpreted your statement?

On another note, your dissatisfaction with active crossovers for the mid and treble is almost certainly down to lack of equalisation for the upper drivers, which the "simple" passive crossover is doing. This is the voicing that the speaker designer builds into his crossover/driver combination that is very difficult/time consuming to replicate when going active.

[georgehifi]

No, active 24 db for the bass up to 125hz and passive for the for the 125hz up, and yes all the equalization for the ESL's was still on the ESL's whether passive was use or the active, and let me say the active robs the musicality from the music, it still has the same tonal balance, but it's sterile, has no body or ambience, passive is the only way for mid/treble. Opamps no matter how good, rob musicality! If I had my way the cd player would drive the speakers direct!

Cheers George