# Detuned cabinet - WOW!



## mrmatt1972

So I've been struggling with my current low budget rig. I'm running a Peavey Rockmaster into a Tubeworks MV-962 power amp into a 2x12 cab that I salvaged from my Traynor YGL-3 (The Traynor twin) when it died. I made the old amp cab into a closed back cab that I can run stereo if I want or with only one speaker going in lower volume situations. This rig has it's moments, but I'de been getting annoyed by boomy bass and icepick highs coming from the old Eminence speakers. 

I have an old book by London Power guru Kevin O'Connor about cabinet construction that suggests "detuned" cabinets. Essentially they are cabs with the port on the front allowing the elimination of standing waves and increased volume with lower cost. I looked at Kevin's dimensions for a 1 x 12 detuned cab and my rig was almost spot on so I removed 1 speaker and gave it a try. 

All I can say is WOW! Incredible clarity, no icepick highs and increased volume. I never would have believed it until I tried it. Now I just need to find the perfect "do it all" speaker.

Matt:rockon2:


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## greco

mrmatt1972 said:


> I looked at Kevin's dimensions for a 1 x 12 detuned cab and my rig was almost spot on so I removed 1 speaker and gave it a try.
> Matt:rockon2:


Just to clarify, the port is the hole in the baffle from your other 12" speaker? That would seem like a large port....or did you cover that hole and put in a smaller port?

Main thing is that you are enjoying the cab now...congrats !!

Thanks

Dave


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## mrmatt1972

Yes, the port is the former mounting hole for the other speaker. These cabs are closed back by design. Apparently it is a happy accident that the mounting hole is exactly the right size mathematically for this to work.

I've played through it more now with my rack rig and with my Blackheart amp. All I can say again is WOW! Lots of volume (as much or more than with both speakers in), better clarity and note definition, no woofing bass and no icepick highs. Best DIY mod on the planet!

Matt:banana:


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## Budda

woofy bass and icepicky highs is also usually from running the bass and highs way too high at x volume vs the actual speaker/amp itself.

what speaker do you have in there now?


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## mrmatt1972

Budda said:


> woofy bass and icepicky highs is also usually from running the bass and highs way too high at x volume vs the actual speaker/amp itself.
> 
> what speaker do you have in there now?


I usually cut highs, they are never at more than 1/2 way up the knob. Bass is on 7 or so usually depending on the amp. As for volume, On the Blackheart it's at 5 -7 on the knob (only a 5 watt amp) and the rack rig is never more than 3/10 on the knob - It's a 40 watt SS amp, I also cut back on the presence knob on the rack rig. The speaker is the original '70s Eminence from the Traynor combo. I'm guessing the speaker is 50 watts.

I can generally sing over top of what I'm playing without a mic, but I bellow a little...

Regardless, with the "detuned" cab, my eq is more responsive and the sound quality is nothing short of phenomenal. However, I would like to buy a new, better, multi-purpose speaker that can go country clean to SRV or ZZtop overdrive. Any suggestions on that front?

Thanks, Matt


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## mhammer

Quite fortuitous that the cab met the needed specs!

It is common practice in hifi speaker systems to have what is called a "passive radiator". It is essentially a cone with no voice coil or magnet, and is often slightly weighted so that it favours the bass. The objective is to provide more cone surface at the disposal of the amp, but with several advantages:
1) smaller diameter cones can move faster and have better transient response.
2) smaller diameter cones add more surface area to move air but do not require the same design restrictions/requirements as using a single larger speaker (they are often seen in narrow column speakers).
3) they can have some of the same properties of tuned ports, in terms of making productive use of the energy created when the active speaker cone moves backwards.

I'm wondering if the tonal response of the cab might be profitably "tuned" by the use of a passive radiator of the required size.

Incidentally, it is worth noting that by omitting one speaker you may also change the tone of the amp by changing the load. Maybe.


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## greco

deleted post


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## rwe333

I built a couple of 1x12 cabs around the specs/speakers outlined in Kevin/London Power's book (buy it - very cool). 
They functioned as described and I mos def dug 'em. Will likely build another. Bit of a bear to mic...
Caveat: it is, of course, a bigger enclosure than your standard 1x12 configuration.


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## Budda

country cleans eh? makes me think of whatever they'd put in a fender twin, or perhaps even a Vox AC30.

cant say i have much experience on that front. email WGS, Celestion, Eminence and see what they suggest!


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## salv

mrmatt1972 said:


> So I've been struggling with my current low budget rig. I'm running a Peavey Rockmaster into a Tubeworks MV-962 power amp into a 2x12 cab that I salvaged from my Traynor YGL-3 (The Traynor twin) when it died. I made the old amp cab into a closed back cab that I can run stereo if I want or with only one speaker going in lower volume situations. This rig has it's moments, but I'de been getting annoyed by boomy bass and icepick highs coming from the old Eminence speakers.
> 
> I have an old book by London Power guru Kevin O'Connor about cabinet construction that suggests "detuned" cabinets. Essentially they are cabs with the port on the front allowing the elimination of standing waves and increased volume with lower cost. I looked at Kevin's dimensions for a 1 x 12 detuned cab and my rig was almost spot on so I removed 1 speaker and gave it a try.
> 
> All I can say is WOW! Incredible clarity, no icepick highs and increased volume. I never would have believed it until I tried it. Now I just need to find the perfect "do it all" speaker.
> 
> Matt:rockon2:


What size is your cab? Might give it a try if mine measures out to be the same.


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## mrmatt1972

salv said:


> What size is your cab? Might give it a try if mine measures out to be the same.


I'll post Kevin's dimensions later tonight if I get a chance. The 1x12 he recommends is slightly larger than the average 2x12. I't worked out that the old Traynor cab was longer than average and higher than average, so it worked out.


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## salv

mrmatt1972 said:


> I'll post Kevin's dimensions later tonight if I get a chance. The 1x12 he recommends is slightly larger than the average 2x12. I't worked out that the old Traynor cab was longer than average and higher than average, so it worked out.


That's why i'm asking is because I just picked up an old Traynor cab. If I could save myself the money, i'd rather just buy one new speaker instead of the two.


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## greco

I googled "detuned cab" and found this interesting thread:

http://www.thegearpage.net/board/archive/index.php/t-78737.html

Cheers

Dave


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## salv

I just tried it with the original speakers. WOW...i haven't had much time with this setup to begin with but it sounds alot more of what i've been looking for. The biggest difference in my opinion is clarity as mrmatt1972 mentioned earlier. I can only imagine what a speaker upgrade would sound like.


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## greco

salv said:


> I just tried it with the original speakers. WOW...i haven't had much time with this setup to begin with but it sounds alot more of what i've been looking for. The biggest difference in my opinion is clarity as mrmatt1972 mentioned earlier. I can only imagine what a speaker upgrade would sound like.


Do you notice any difference if the port is positioned on the top...or the reverse? If so which did you prefer?

I have a 2 x 12" closed back cab, but the dimensions are a bit small ...according to O'Connor's suggested size of 24" x 30" x 16" in this link:

http://www.londonpower.com/speakers.htm

I still might try it just for fun.

Dave


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## salv

This cab is a 24" x 32" x 13" 

I only tried with the port on the bottom. I always like having my amps a little off the ground so to me i just figured I should leave the top one in.


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## mrmatt1972

salv said:


> This cab is a 24" x 32" x 13"
> 
> I only tried with the port on the bottom. I always like having my amps a little off the ground so to me i just figured I should leave the top one in.


Glad you liked the change Salv, that's why i posted in the first place! I also have my speaker on top and port on the bottom. This was only because I had 2 different speakers in the cab and I kept my favourite one in place (ditched the Celestion 70/80). Kevin suggests the speaker go in the bottom, he claims that it helps bass response. I', going to move the feet on my cab before a jam tonight. I'm only taking my 5 watt blackheart amp to play with drums, bass and 2 other guitars. I'll let you know how it goes.

sdsre
Matt


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## greco

Thanks Matt...cool thread !!

Please keep us updated.

Cheers

Dave


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## mrmatt1972

Hi again. I'm just back from jam night so here's the update:

Still WOW.

I now have the speaker on the bottom and the port on the top. It is marginally better this way.

My Blackheart set to 5 watts and between 4 and 5 on the volume knob was as loud as the drums. The sound was beautiful, clear and "linear" if that makes sense. My leads, especially those with a good amount of OD sounded amazing (not the playing, just the tone :wink I think I'm just going to keep this old speaker for a while longer. I may try a Celestion Century once I recover from Christmas...

Matt


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## JSX/6505

mhammer said:


> Incidentally, it is worth noting that by omitting one speaker you may also change the tone of the amp by changing the load. Maybe.


This is exactly what I was thinking.


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## whammybar

Nice to hear the detuned cab thing worked! I bought the book years ago and could never afford the price of the wood to build it. Thanks again for the info. I'm also curious though about the load on the amp which must have changed rather dramaticaly. How many ohms are you running now with just the one speaker as opposed to how many you were running with both speakers?


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## mrmatt1972

I don't think it is a load changing thing as I plug the speaker into the appropriate speaker out. You _can _get subtly different tones by running an 8 ohm speaker in either the 4 or 16 ohm tap (but don't do it too loud or too long), but that is not what I am doing.

Matt


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## whammybar

So (bear with me I'm a little slow to catch on here) you have multiple outputs on the amp with different ohm ratings so you can match the speaker load? How did you manage that?


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## greco

Yes...*some* amps have speaker jacks/outputs for 4 ohm, 8 ohm and 16 ohm speakers. The output transformer is specifically tapped for these impedances.

...very handy:food-smiley-004:

Dave


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## mrmatt1972

*Cab Dimensions*

Better late than never... Here are the promised dimensions from Kevin O'Connor's Speaker book. I'm only going to post the _internal _dimensions and let interested parties either use their knowledge of cabs and woodworking to fill in the blanks, or buy the book. I don't want to infringe on any copyright (if that's even possible).

30" x 22-1/2" x 13 - 1/2" This yields an internal volume of 5.27 cu.ft.

The speakers holes are side by side. The cab stands on the 22.5" side. Speakers are 8" from edge of baffle to centre of speaker/port hole. It is meant to be a 1 x 12 cab.

Have fun. I'm going to make a pair this summer.

matt


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## rwe333

mrmatt1972 said:


> Better late than never... Here are the promised dimensions from Kevin O'Connor's Speaker book. I'm only going to post the _internal _dimensions and let interested parties either use their knowledge of cabs and woodworking to fill in the blanks, or buy the book. I don't want to infringe on any copyright (if that's even possible).
> 
> 30" x 22-1/2" x 13 - 1/2" This yields an internal volume of 5.27 cu.ft.
> 
> The speakers holes are side by side. The cab stands on the 22.5" side. Speakers are 8" from edge of baffle to centre of speaker/port hole. It is meant to be a 1 x 12 cab.
> 
> Have fun. I'm going to make a pair this summer.
> 
> matt


Yes, folks... Buy the book. Not expensive. Check here.


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## greco

mrmatt1972 said:


> Better late than never... Here are the promised dimensions from Kevin O'Connor's Speaker book. I'm only going to post the _internal _dimensions and let interested parties either use their knowledge of cabs and woodworking to fill in the blanks, or buy the book. I don't want to infringe on any copyright (if that's even possible).
> 
> 30" x 22-1/2" x 13 - 1/2" This yields an internal volume of 5.27 cu.ft.
> 
> The speakers holes are side by side. The cab stands on the 22.5" side. Speakers are 8" from edge of baffle to centre of speaker/port hole. It is meant to be a 1 x 12 cab.
> 
> Have fun. I'm going to make a pair this summer.
> 
> matt


This is an old thread...Matt...did you build these cabs?

Are you still into detuned cabs ? 

Anybody else using detuned cabs...what are your comments?

I'm about to try the detuned concept with a a 2 x 12 (not Kevin O'Connor's dimensions)

Cheers

Dave


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## mrmatt1972

greco said:


> This is an old thread...Matt...did you build these cabs?
> 
> Are you still into detuned cabs ?
> 
> Anybody else using detuned cabs...what are your comments?
> 
> I'm about to try the detuned concept with a a 2 x 12 (not Kevin O'Connor's dimensions)
> 
> Cheers
> 
> Dave


I have not built anything yet. the school year ends for me on June 19. After that i'm going to do it. Also, dave, I put a Weber speaker that i ordered for my windsor studio into that detuned cab of mine. As a 2x12 with the Weber it sounds great, but it doesn't have the "openness" of the detuned cab. I plan on making 2 1x12s as detailed above. I'll post in July when they are done.

matt


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## greco

Thanks Matt...looking forward to your post in July.

Hope they go together easily for you....(i.e., no major glitches)

Cheers

Dave


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## KapnKrunch

Couple of points to bring up from the book under discussion.

A passive radiator is... well, useless. No advantage over an open hole.

The postion of the open holes is irrelevant. Up or down makes no difference. In a 4x12 cab, remove any two speakers, up, down, sideways, diagonal.

Best part, there is NOTHING critical here.

For best results the cab should be at least 14" deep and a couple of inches wider than the speaker on all sides.

But any closed back cab will improve. And any speaker... "even a Celestion" jokes the author.


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