capacitors parallel to speakers

[Tage]

I was wondering if it was possible to bypass some harsh high frequencies at the speakers. I have a pair of WGS G12C's, and they are uncomfortable bright, can I put a high voltage cap across the speaker to bypass highs? or am I gonna run into creating some sort of resonance due to the interaction of the capacitance and the speakers inductance...

[JoeM]

Hmm. I wouldnt do it. First of all how new are the speakers? They may just need more break-in time. What amp is this? It would better to roll off some highs in the the amp.

[Chuck H]

Speakers usually present a very high impedance at higher frequencies. The concept should be about the same as the primary OT circuit typically called a "conjuctive filter". Which is some kind of adopted name for a zobel shunt high pass filter. A cap in series with a resistor should be fine. The resistor should be valued a little higher than the load to be reasonably sure that the amp is playing into a safe impedance match. I play my amp into a resistive dummy load all the time. Which is a straight up 8 ohms at all frequencies on an 8 ohm secondary. Since a speaker may have 60 to 200 ohms impedance at higher frequencies, knocking that down to, say, 10 ohms for an 8 ohm secondary should have a significant effect. You could even make the resistance variable with a rheostat and dial in what sounds best.

FWIW, you may also find that the speakers just need to break in. Even the V30, which is notorious for being high mid and sometimes hashy, breaks in nice and mellow with enough play time IMHE.

[Tage]

Well the speakers belonged to my brother, who gave them to me in payment for some amp repairs I did. He had played them for around 50 hours, at gigs with his JCM800 and Ampeg V4, both of which sounded too bright. I took 2 of his 4 and use them in my test cab, and with a few different marshals and my AC4 they still have an annoying top end to them. although those are all admittedly brighter amps, except the V4.

I suppose I'll keep playing them, and more often, to try and see how they break in. I suppose I could try a very subtle zobel high pass filter.

[tedmich]

Some people like Weber Beam blockers to tame cone center high freq.
Weber Beam Blocker -- high frequency diffuser
and this breaks in speakers nicely over a long weekend (while you are away!)
http://www.hagtech.com/media/frybaby.mp3
its Hagtech's Frybaby and makes the most un-ignorable ringtone on my iPhone! Not safe for headphones, you have been warned!
(As Chuck states playing works fine too)

An inductor in series with the speaker forms a mellow 6db/octave low pass, with about 0.25 mH taming the obnoxious 5k peak many 8 ohm guitar speakers have.

[Tage]

I suspect that inductor would need a decent power rating to use a high powered amp with the speaker-inductor system?

[tedmich]

the inductors are usually air core to avoid any core saturation issues and the open geometry cools well, so an 18AWG wire coil can handle a true 300w RMS
a simple calculator here
Pronine Electronics Design - Multilayer Air Core Inductor Calculator
shows about 100 turns on a 1 " x 1" form gives a DCR of only 0.2 ohms at 0.25mH (careful on magnetic coupling with OT/PT!)
course PartsExpress has them for <$5
Jantzen 0.25mH 18 AWG Air Core Inductor 255-214

apologies ahead of time as instrument amp guys HATE crossovers!

[loudthud]

A Zobel really improves the effect of the inductor. For a 4 ohm load, halve the inductor and resistor, double the capacitor. For a 16 ohm load, double the inductor and resistor and halve the capacitor.

[Tage]

good stuff and thanks for the feedback, I think I will give this a go in a few weeks when I have a bit of time to mess around with it.

[trem]

Eq pedal perhaps.?
best

[Tage]

no it's not something that really goes away by rolling of the treble. It's just a characteristic of the speakers.

[Chuck H]

a DCR of only 0.2 ohms at 0.25mH

But doesn't that just increase the impedance at HF??? And aren't we supposed to avoid too high an impedance? Is it better than shunting the HF to the amps rated load? I'm not being difficult. I just wonder if there is an advantage to the inductor WRT the amp. The cap in series with a resistor seemed like a good safe bet to me.

Loudthuds circuit seems better because the speakers typically high HF impedance is no longer in series with the impedance the amp sees. The inductors impedance, plus ten ohms is what the amp sees. But what's wrong with just a resistor and capacitor?

[J M Fahey]

Or grab the bull by the horns, sell those V30 to a guy who loves them and get some similar Eminences but the PA version.
Jazz players *love* them because they are basically the same (same magnet, voice coil diameter, frame) but youŽll see that they do not have the typical "Rock" 8 or 10 dB presence peak ... which is exactly what's annoying you.
Download the datasheet PDF and compare the smooth curve of the Beta12A to, say, the Legend V128 which is a "British sounding" speaker.
I often get a whiteboard marker pen, those which can be erased with a piece of dry cloth , open one curve , trace it on the screen, and then open the other,,same magnification, to superimpose them.
*Many* small sound differences are immediately clear and easy to compare.
Unfortunately, Celestion and Eminence use very different graphs , which can't be superimposed.
Oh well.

[Chuck H]

And Celestion is often vague about specs.

The V30 is my favorite speaker. Great for getting up in your face when new. Much softer top end when broken in. I don't play that much. Maybe two hours a week. It took me over a year to break in a V30 with a 20W amp cranked into it. In case we're looking for data, that's 20W, plus whatever chaos an amp makes at full tilt, for about 120 hours to break in a 70W speaker. I really hope it lasts 'cause I'd hate to have to break in another.

A lot of guys like the EV sound. Which to me is sort of similar to the typical Eminence "legend" sound. Boxy. Sort of rolled off in the top and bottom. Focused more in the low mids. Not my thing. but definitely more of what most tone seekers seem to want. Muffled = good?!?

The OP's speakers are supposed to be like a Jensed C12N. WGS says they're "warmer" but it's a really bright speaker anyway. Definitely more suited to clean tones.

The beam blocker is probably the least subjective solution. Everything I've read reports that they work very well. Pick a blanket over the amp. If it sounds more correct, beam blockers might be an easy solution.

[tedmich]

Zobels are a better implementation on amps that are sensitive to driver impedance, but many a megabuck speaker system with passive crossovers omit them.

As to putting a blanket over speakers I have seen audiophile speaker reviewers who swear by judicious placement of Kleenex over the tweeters of +$10k speakers!

Rather than dealing with the odd response curves of guitar speakers and their very spotty QC/ individual driver variation, I have been using smaller "flat" speakers and dialing in the tone with a 3 band active (+/-15db) TS but I don't play stadiums, or very loud even!

I apologize for for suggesting crossing over a guitar speaker, I should know by now its just NOT done! You want different speaker sounds buy a few dozen different peaky, large and expensive 12" drivers using 1970's technology and mount them in open backed cabs designed solely for traveling robustly across the country.