speaker break-up

firedude · Posted: Sat Dec 02, 2006 6:37 pm Post subject: speaker break-up

OK, so I put an Eminence Red Coat speaker in my Marshall MG 30 DFX. It is an 8 ohm speaker. The original is 4 ohm. When I turn it up I get lots of speaker break-up. So, is the break up from (a) the speaker is designed to break up? (b) the impedence mismatch? or (c) it's only 30 watts. I am looking for clean volume. I'm now thinking of building a separate cab using another 8 ohm speaker, wired in parallel to get 4 ohms. Thanks for any response.

Goes_To_Eleven · Hamster Joined: 07 Oct 2005 Posts: 87 Location: CT, USA

Solid-state amps will work with an impedance that is mismatched higher than the amp's rating, but you'll lose volume and gain undesirable distortion (as you have noted). For clean volume, your best bet it to match the impedance properly and buy a higher-wattage speaker along the lines of a Celestion Vintage 30 (60w) or GT12-75 (75w). Adding an external cab with another 8-ohm speaker in parallel will solve your impedance mismatch. If you like the Eminence speakers, go with 50 or 75-watters for more clean headroom as lower-wattage speakers break up and distort quicker.

By the way, you did replace the stock speaker with a 10" speaker, correct? I looked up the Redcoat and it's listed as a 12" speaker. Improper fit could also add unwanted vibrations and hurt your sound.

firedude · Posted: Sun Dec 03, 2006 7:24 am Post subject: speaker breakup

Yes, it is the 10 inch Ramrod speaker. It's rated at 75 watts. I think building a cab with two of these should sound pretty good. Whats the difference in tone with an open back or closed back cab? Thanks for the info. Having fun in South Texas...

Goes_To_Eleven · Hamster Joined: 07 Oct 2005 Posts: 87 Location: CT, USA

Okay then. Well, the fit is fine and the speaker handles enough wattage to give you headroom, so the impedance mismatch must be causing the unwanted distortion. Trying the extension cab may do the trick.

An open-back cabinet loses bottom end, and the lows that are there aren't as tight. Closed-back cabs increase lows and lend to a tighter sound. I've had both half-back and closed cabs, as well as combos, and prefer the closed design tremendously. Much tighter and punchier.

pizza8guy888 · Little Hamster Joined: 17 Jun 2005 Posts: 77 Location: NJ

I have an AVT50 and also replaced the speaker to an 8ohm I actually got a dramatic increase in volume due to nearly 6 decibels more efficiency (so even if the power was cut in half, i was still 3 decibeld louder then i originally was) anyways. The distortion isnt coming form the higher impedence. In my opinion i believe it is the speaker you chose (the redcoat line) is meant to have a more british sound and earlier breakup. Also since the amp is only 30 watts which is definately loud enough, but to get the volume you have to turn the knobs up pretty far and liek i said since it's a 30watter, it will tend to break up or overdrive the amp more quickly. Your idea of getting another speaker to make it 4ohms would in fact clean up your sound I believe, because it will bring back and give more power that will be available before it starts brekaing up. I know I explained that all pretty confusingly and bad, but bottom line if u put 2 speakers and make it 4ohms you should get some better clean headroom.

Goes_To_Eleven · Hamster Joined: 07 Oct 2005 Posts: 87 Location: CT, USA

That's incorrect. Higher-wattage speakers distort at a much slower rate that lower-wattage speakers. Mismatched impedance (it's mismatched lower at 4 ohms with an 8-ohm speaker, by the way) kills efficiency, which in turn kills the amp's ability to efficiently drive a speaker, resulting in undesirable distortion. A speaker's voicing won't cause off-color distortion. Damage to the cone would.

With proper impedance, a 30-watt amp can drive a 60 or 75-watt speaker without a problem, and the higher power rating of the speaker allows for more clean headroom as it takes longer for the speaker to drive into distortion. Impedances need to match for a reason, as more resistance than an amp expects results in a harder push and a less musical sound.

Add the second 8-ohm cab and you'll match. You'll also get a fuller sound.

firedude · Posted: Thu Dec 07, 2006 4:53 pm Post subject:

Thanks for all the input. I received my second speaker today from AMS. As soon as I get time I'll build a cab and let you know how it turned out. Right now I'm in the middle of a major remodel of my kitchen. (wife's idea), some fun. Thanks again.

bitingsound · Sea Monkey Joined: 26 Feb 2007 Posts: 10

Great info. Been meaning to ask the same question.

_______________________
McIntosh MA6900 Integrated Amplifier - Download the MA6900 Integrated Amplifier Catalog by McIntosh Laboratory, Inc.

firedude · Posted: Tue Mar 13, 2007 7:40 pm Post subject:

Well, I built my ext cab. I love it. It really sounds good, louder, and cleaner. I'm still working on the kitchen, believe it or not, but I really enjoyed building the cab. I might build some more just for fun. Might post some pics later.