detuned cabinets

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lumox0013
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detuned cabinets

Post by lumox0013 »

has anyone tried kevin o'connors detuned speaker cabinets ? what did you think? thanxx for any input
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shoggoth
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Re: detuned cabinets

Post by shoggoth »

Yes, I built a detuned 2x12 with a pair of G12T-75's. It sounded very good when I put my Peavey 6505+ 112 combo through it, I was in love with the sound.

The H&K Coreblade in the picture sounds like a fizzy piece of crap through any speakers, I hate that amp (I had borrowed it from a friend).

Note that Kevin prefers a pair of detuned 1x12's to a 2x12, so he can position the speakers independently.

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Aurora
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Re: detuned cabinets

Post by Aurora »

I've been fiddlin' with speakers for ver 40 yrs now.... but a detuned speaker????
A speaker which is deliberately put in a wrong size cab, according to parameters???
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lumox0013
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detuned cab

Post by lumox0013 »

the idea is a detuned cabinet somewhat like a open back cab with the output all directed forward I am going to build one in an old 6x10 that I have but thought i would see if anyone around here had tried it first kevin is a super smart guy I have 4 of his books great stuff I think i will get the speaker cab book before I start this project. thanxx again for any input always love to see y"alls projects. cheers!!
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Turbojunkie
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Re: detuned cabinets

Post by Turbojunkie »

I really enjoy using detuned cabinets, gave it a try after reading a thread on the topic. I ended up getting KOC's book on speaker cabs. It's a nice little reference book...along with explaining the detuned concept, it's got some good detailed information on the carpentry involved in building cabs, phasing issues, resonant/non-resonant cabinet pros & cons, etc. ....Detuning works great for me, quite a few improvements over open and closed back cabs. Right now my favorite cabinet with my Rocket build is an old basket weave Marshall 4x12 with 2 alnico blues in it.

The extra bass response is great, both lower and louder, and the cabinet in general just sounds "bigger". To me, it's got the air that an open back cab has, but way more consistent....the problem of where to position a open-back cab in a room, (bass too thin in one place, or too boomy in another) is eliminated.

When compared to 2x12/4X12 closed back cabs, you only need half as many speakers, so it's less expensive & weighs less, along with the fact that a detuned cabinet with half the speakers is almost (or just) as loud as a fully loaded closed back 2x12 or 4x12, given the same speakers, or ones that are equally efficient. The only situation where a closed back cab is better is when you need a tight & punchy low end for chugging, palm-muted riffing stuff.

Lastly, although YMMV, it's such an easy, free and reversible mod to try, it's certainly worth checking out to see if it works for you.

Turbojunkie





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First 25 years of playing, I never got along with EL84's...Now I think, WHAT THE HELL WAS WRONG WITH ME????
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Aurora
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Re: detuned cabinets

Post by Aurora »

So - are you saying that the back is closed, and the rear wave is directed forward through a port, so in essence it is a sort of bass reflex??
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Turbojunkie
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Re: detuned cabinets

Post by Turbojunkie »

Yes, that's the idea. But instead of a cabinet & port being tuned to a small, specific frequency range, the port of a detuned cabinet is intended to affect a wider range of the frequencies that guitars produce.

A speaker sized cut-out ends up working well because it's large enough to affect a wide EQ range, but not so large that you end up having no speaker damping at higher volumes. The hole needs to be sized as if you were going to mount a speaker. For example, if using 12" speakers, the actual hole diameter would be 10 3/4"....

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First 25 years of playing, I never got along with EL84's...Now I think, WHAT THE HELL WAS WRONG WITH ME????
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Turbojunkie
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Re: detuned cabinets

Post by Turbojunkie »

Forgot to mention that most of the last post was paraphrased from the London Power "DIY Speaker Cabinets for Musical Instrument" booklet.
First 25 years of playing, I never got along with EL84's...Now I think, WHAT THE HELL WAS WRONG WITH ME????
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jaysg
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Re: detuned cabinets

Post by jaysg »

Turbojunkie wrote:Yes, that's the idea. But instead of a cabinet & port being tuned to a small, specific frequency range, the port of a detuned cabinet is intended to affect a wider range of the frequencies that guitars produce.

A speaker sized cut-out ends up working well because it's large enough to affect a wide EQ range, but not so large that you end up having no speaker damping at higher volumes. The hole needs to be sized as if you were going to mount a speaker. For example, if using 12" speakers, the actual hole diameter would be 10 3/4"....
In the late 80's and early 90's, both Mark Knopfler and Eric Clapton used 1960A cabinets with two EV-12L speakers. Two open holes and the backs on. They use other stuff now, but it's not unheard of.
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Aurora
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Re: detuned cabinets

Post by Aurora »

This sounds like the classical reflex formula from the early 50s.... the typical reflex opening was appx same area as the speaker, and no port or tunnel as we know it today..... I think some of the more popular open back cabs really operate on the same principle, only with the opening in front. If one applies modern speaker T/S parameters and reflex calculations, nothing fits for the old systems... :)
May very well sound good for guitar, but lower end bass will suffer...
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Cantplay
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Re: detuned cabinets

Post by Cantplay »

Doesn't the speaker need to load against air resistance to keep from bottoming at higher power/low frequency?

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Re: detuned cabinets

Post by Long Distance Call »

Standel made a cabinet based on a similar idea back in the late 1950's - early 1960's.

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Aurora
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Re: detuned cabinets

Post by Aurora »

Cantplay wrote:Doesn't the speaker need to load against air resistance to keep from bottoming at higher power/low frequency?

John
This is more of an urban myth than truth. Membrane excursion is really only based on supplied power vs magnet strength and voice coil gap and coil height. Usually a max excursion is also stated in the spec sheet.
Air spring damping is more of a case in closed cabs, as it will cooperate with the mechanical parameters of the speaker element. The Qt, the total Q value of the electrical and mechanical parameters tells a lot about possible behaviour and lower f response in different cabs. Values of about 0.6 and upwards usually describes a speaker element mostly suitable in open baffle, - in this context open back cabs. The problem with the more popular guitar speakers, is that no T/S parameters are given, as opposed to PA and HiFI speakers, where these are the basis of all qualified designs. Guitar speakers / cabs are a lot more based on tradition, and a hit or miss design from back then, maybe except for the socalled Thiele cabs, which seems to be based on modern T/S parameters, although I haven't tried to recalculate ny of these cabs.
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Re: detuned cabinets

Post by Colossal »

Turbojunkie wrote:Yes, that's the idea. But instead of a cabinet & port being tuned to a small, specific frequency range, the port of a detuned cabinet is intended to affect a wider range of the frequencies that guitars produce.

A speaker sized cut-out ends up working well because it's large enough to affect a wide EQ range, but not so large that you end up having no speaker damping at higher volumes. The hole needs to be sized as if you were going to mount a speaker. For example, if using 12" speakers, the actual hole diameter would be 10 3/4"....

Take Care,

Adam
Adam,

I don't have O'Connor's books (need to get them) but did some research on detuned cabinets a while back. I recall reading a thread on another forum which came up in a search where a gentlemen suggested that the port opening should actually be 1.618 times the speaker area, so, the Golden Mean is the multiplier, not using the same area as the speaker. I don't know if this idea is discussed in the book or not. Most everything I've read suggests just taking a 2x12 and removing a speaker and voila, your cabinet is now detuned.

Also, can you speak to the geometry of the port area? Should it be round like the speaker cutout or can it be other shapes so long as the port area is equivalent to the speaker area?
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Aurora
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Re: detuned cabinets

Post by Aurora »

The Golden Ratio pops up ever so here and there as a sort of magic touch in a lot of different areas, also in speakers from the late 40s and early 50s, and is still often used as WxDxH ratios in modern speaker cabs, but the figures you mention actually describes the rather haphazardly approach to the designs from back then. I think the first really scientific approach to speaker cabs was done by Harry F.Olsson and thoroughly described in the book "Musical Engineering" in the late 50s. Leo Beraneks "Acoustics" came later in the 60s, and these two more or less forms the fundamentals of modern loudspeaker technology. The T/S parameter regime was defined by Mr's Richard Small and Neville Thiele in the late 60s. Beranek and Thiele /Smalls work is math heavy. Other more modern books like Vance Dickasons "Loudspeaker Cook Book" is a very good but a ot more accessable, and gives very good descriptions og various forms of cabinets and tehre behaviour. It is of course mainly directed towards HiFi, but for better or worse, guitar speakers are subject to the same laws of physics. I have actually taken the job of proofing a few of the classical guitar speakers and cabs versus modern theory, but nothing fits.....
That has nothing to do with these cabs doing a good job for what they do - it merely confirms my suspicions of "More luck than knowledge" in these designs - or a cut and try approeach with a good result.
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