Speaker Cabinet Designs- Questions

[silverfox]

I don't want to start a flame throwing contest here. Just asking some questions.

I've seen various discussions regarding the best designs and recently talked to someone in a car audio shop regarding speaker cabinet designs. Some of the information I got left me scratching my head as it was new but it also didn't seem to fit with my previous understandings. Particularly the variations in power handling capabilities when a speaker is mounted in a sealed-ported or sealed cabinet vs an open back cabinet.


What generally speaking, are the differences in power handling capabilities of the various cabinet designs related to the speaker? (I was told that different designs would degrade or increase the power handling capacity of a particular speaker).

Frequency response?

Mesa Thiele ported speaker cabinet with 1 12" speaker- (variation of closed back?)

4 12's sealed cabinet

4 12's open backed cabinet

4 12's closed Back cabinet

Does it make sense to build a cabinet that has ports that can be opened and closed?

I'm thinking a combination cabinet consisting of the top 2 12" speakers as a sealed set with the bottom 2 12's in a Mesa Thiele design with the 2 ports at the bottom might be a good combination.

Here is a link to the Thiele designs based on Electrovoice enclosures: http://www.instructables.com/id/Build-a-Ported-Guitar-Cabinet/?ALLSTEPS

I realize these are all highly subjective questions so I'm looking for a range of opinions. Not trying to reinvent the wheel either.

Silverfox.

[G._Hoffman]

It shouldn't change the power handling of the speakers, but it WILL change the efficiency of the speaker.  Basically, an infinite baffle speaker (i.e., closed back cabinet) will be quieter than the ported or open back cabinet.  My understanding, which PRR is sure to correct soon, is that this is to do with the build up of pressure inside the cabinet.  Since closed back cabinets also sound better to most people (including me), and guitar amps typically have vastly more volume than you really need, I don't spend much time worrying about it, and just make my cabinets with infinite baffles.



Gabriel

[silverfox]

Over the week end I removed a defective solid state chassis from a Behringer practice amp. That left a rectangular space of about 3x15 or so inches at the top of the cabinet and a 8-10 inch speaker in the cabinet. I then closed up the back of the cabinet.


This was connected to a Kustom 10 watt EL84 based amp with an added 3 tone stack. Previously, when plugged into a 4-12 sealed back cabinet, the Kustom was usable, the sound was tinny. With this cabinet there was a much fuller sound. To be fair, the coupling cap prior to the EL84 is: .022 and I intend at some point to change that to .1 to enhance the low frequencies in the output.

It must be the case. the sound out the reflex port is out of phase but, there was a noticeable, positive change in the quality of the sound. The intensity was reduced  but that must be due to the phase cancellations. The cabinet must have become a low frequency filter too.

Corrections please??

Silverfox.

[Ritchie200]

Hey Silverfox,

I am assuming that if it was originally an open backed cabinet, you added the port?  How big is it?  Did you use some calculation to figure size and length of tube (if any)?  What is the interior size of the cabinet?  You mentioned 8-10" speaker?  What size did you end up with?

"I've seen various discussions regarding the best designs and recently talked to someone in a car audio shop regarding speaker cabinet designs. Some of the information I got left me scratching my head as it was new but it also didn't seem to fit with my previous understandings. Particularly the variations in power handling capabilities when a speaker is mounted in a sealed-ported or sealed cabinet vs an open back cabinet. What generally speaking, are the differences in power handling capabilities of the various cabinet designs related to the speaker? (I was told that different designs would degrade or increase the power handling capacity of a particular speaker)."

I'm assuming the flame throwing contest you refer to is the friendly (at least on my part) disagreement I had with someone on a recent post about re working a 4x12 speaker cabinet.  One of the things I challenged him on was his improper application of subwoofer and low feq cabinet resonance to our much higher freq guitar reproduction.  Because of the extreme excursion of low freq speakers, a sealed cabinet can affect power handling.  That may be what your car audio guy was talking about.  In our case of reproducing a guitar it is not an issue and any power reduction is probably negligible.  Like I mentioned on that previous thread, there have been volumes written over the years about cabinet design dealing with reproduction, reinforcement, subwoofer, musical instrument, etc., etc...  Some subjects overlap and many contradict each other.  Gab brings up an excellent point.  Try it open and try it closed.  See what you like best?  Now we could get into the type-of-cabinet-wood discussion!

Jim

[Ritchie200]

It's bigger on the inside!  Or...is it smaller on the outside!

Jim
4th and only Doctor

[SILVERGUN]

There's a lot of guys that agree that this 2x12 ported design sounds good:
http://www.drzamps.com/products/z_best.html

I attached the EV plans for the Theile TL806 cab ......most of the links on the web take you to a page that doesn't exist anymore

when I get some time i'll probably just trust the thousnds of guys that say "this cab sounds great with this speaker",,,and be done with it,,,and build one

[Ritchie200]

I always tell folks that the recordings I post are sorta the blunt instrument approach.  Lots of volume and noise.  Over the years I've played through a lot of cabinets and a lot of different speakers.  Please bear with me, I don't want to sound like the old man saying he walked uphill 10 miles in waist deep snow to go to school.  Although there were times...  Anyway, I've also built a few cabinets over the years.  My crowning glory were two Altec Voice of the Theater A7's for my band's PA.  I'm sure that if you were trying to reproduce the subtle textures of an acoustic guitar or voice - cabinet construction would make a huge difference.  However, if you are going to be blasting away on the guitar, I guarantee that you will get loads more difference in tone and texture by trying different speakers in a cabinet you can move around and fit in your car - if need be.  I think that is what Gab was alluding to and why I thought is was a good point.  For example, I plugged my Marshall into one of those A7s and disconnected the horn.  It was loud as heck, but I liked the Celestions much much better for guitar.  I happen to like closed back cabinets, but that is from playing out on a stage or in the corner of some bar.  I know I'm not that deaf to not notice these differences or lack of them.  I guess what i'm saying is that in my very humble opinion, the speaker itself is the low hanging fruit.  I think there is much less to be gained with cabinet construction.  (Caveat being a cabinet that sounds good with a guitar, not some crazy thing tuned for 10hz)

Silvergun, when manufacturers use terms like "long throw design to get your sound to the back of the room", they have lost all credibility with me.  Define "long throw".  Define "back of the room".  I'm surprised they didn't mention the "acoustically transparent grill cloth".  Or the "extreme density cabinet wood packed with extra molecules to help reflect the sound out the port".  Is it a directional speaker? Fine, say that.  Is it a wide dispersal speaker? Fine, say that.  I just hate the wordsmith manure spreading.

Jim

[SILVERGUN]

I'm surprised they didn't mention the "acoustically transparent grill cloth"

C'mon now,,,I definitely prefer acoustically transparent grill cloth 

I actually have very little experience, because my 4x12 Celestion V30 cab never failed, and I used it for my entire "career"
Except I would supplement stereo gigs with two half open back cabs with Celes. 12-75s
But I always thought of myself as a tone guy,,,and I listened a lot
I am in no way prepared to have an intelligent conversation about this,,,I only know what I like.
I have to have thick huge bass to be happy, and with that,,,all of the sub 100hz harmonic density that can only come from extra molecules in the wood.....or a good ported cabinet
On stage that stuff just mushes together with the bass player anyway...

So I completely agree with Ritchie,,,, except about those 2 things mentioned (grill cloth and extra molecules)
 

[Slimtim]

That tl806 has a big port so be careful which speaker you put in it and how much power your driving it with.i'm in the camp of the bigger the port the less power it can handle.this mostly would apply to bass heavy deep chugging type riffage.i think this is why i see so many evm12l drivers on ebay needing rebuilt.because folks over power them in those ev and mesa theile cabs and open backs.yeah they're rated high power but put them in a open back or with a big port and they don't last powered by 100 watt amps.here is a good vid showing a bunch of 4x12 with different drivers and then a evm12l oval backed enclosure.most impressive in that big room they're in.Properly handled and cared for it will last a lifetime.https://www.youtube.com/watch?v=rRmAUzKef-w

[Slimtim]

Oh you want to do a combo 4x12 thingy.My bad didn't catch that.Maybe a 2x12 sealed that can sit on top of a 2x12 theile tl 806 cab would be the way to go.Trying to haul around a custom 4x12 with those 806s on bottom would be a little brutal.Plus you might not even like the way the theile sounds with your drivers and setup.maybe a single 12 test run before going all out.What drivers are you using with this idea?

[Ritchie200]

Slimtim, cool video.  Having done a lot of recording I would have to agree with the guy who posted about mic placement.  I would have rather they placed the mic in the middle of the room instead of willy nilly on the cone.  Angle and location can give you a whole range of tonal difference.  I actually liked the JBL best!  Although I spent most of my career playing through early 70's Celestion 30 4x12 cabinets.  Although not represented in the video, I also like the old Laney early 70's era Goodman 4x12's, you drive them hard and they get creamy smooth.  Same cab, much different result.  DEFINITELY for portability, build 2, 2x12 cabinets if you chose that route!!!  Your back will thank you!

The resonance freq of a speaker is tested for in free air as well as the power rating.  Maybe the EVM12 is just a crappy speaker!  Or, like you said, people may just be over powering them.

I have an old 4x12 Tube Works cabinet with jacks for mono or stereo.  I've run my Scholz/Boston SS stereo rig into it and it was just ok, so I now run it through two full range PA speakers that I can separate - much better.  The Tube Works cabinet can handle 300watts through some Eminence speakers supposedly built special for Tube Works.  I run my Major or Hughes & Kettner through it and it sounds fantastic.  I think it sounds as good as my old Marshall 100 cabinets.

Silvergun, I think you are dead on, you know what you like.  Silverfox, If you can check these different cabinets designs and speakers out in person at your local music store, perfect!  You might hate what I or someone else thinks sounds good.  The ear of the beholder!

Jim

[G._Hoffman]

Silvergun, when manufacturers use terms like "long throw design to get your sound to the back of the room", they have lost all credibility with me.  Define "long throw".  Define "back of the room".  I'm surprised they didn't mention the "acoustically transparent grill cloth".  Or the "extreme density cabinet wood packed with extra molecules to help reflect the sound out the port".  Is it a directional speaker? Fine, say that.  Is it a wide dispersal speaker? Fine, say that.  I just hate the wordsmith manure spreading.

Long throw horns have a narrower dispersion, so the power is concentrated along a tighter beam.  Yes, it goes in all directions, but a lot more of the power goes in that straight line.  That, of course, has nothing to do with guitar speakers, of course, but still, there is a legitimate thing as a "long throw" or "wide dispersion" speaker cabinet.  The Meyer UPA-1 and UPA-2 are an example, though they call them "narrow dispersion" and "wide dispersion."  And again, that is to do with the horn, and nothing at all to do with guitar cabinets.


Gabriel

[G._Hoffman]

It must be the case. the sound out the reflex port is out of phase but, there was a noticeable, positive change in the quality of the sound. The intensity was reduced  but that must be due to the phase cancellations. The cabinet must have become a low frequency filter too.

Phase relationships are more complex than that - there is a lot more than just "in-phase" or "out-of-phase."  There are 360 degrees of phase relationships, and they vary a lot with frequency.  At some frequencies they will be destructive, at others they will be constructive and will enhance the frequency.  That particular box must have added at frequencies you liked, and subtracted at frequencies you didn't like.  Every now and then, miracles happen. 


Gabriel

[G._Hoffman]

It's bigger on the inside!  Or...is it smaller on the outside!

Jim
4th and only Doctor

Tom Baker was great, but Matt Smith has been fantastic, and I'm really looking forward to Peter Capaldi's turn!!!  And I'm desperately hoping they bring back River Song so I can watch my 20 year old niece get all fan girl over a couple of 50+ year olds kissing!


Gabriel

[SILVERGUN]

Silverfox,
I don't think anyone who has had to carry a 4x12 cabinet by themselves would suggest building a 4x12 cab,,,,where is it gonna get used?

I think it would be very cool to do a 2x12 with a V front, similar to the old Fender Dual Professional amps,,,,but, with a port along the bottom edge, and maybe a little more angled "V"

Just 2 more of my cents 

[silverfox]

Silvergun: (I attached the EV plans for the Theile TL806 cab)
Thanks, I had searched out those plans and wasn't able to find them. Found several other builds though.

Ritchie200: (Regarding your comment on the Combo build you thought was my goal)-
It was just something I tried out since the amp was unusable. I wanted to cut the effects portion out but the way it's wired made it impossible for me to do without a Schematic so I chopped up the cabinet.

Regarding what purpose the sound system will be used for: I don't play out. Just for my own amusement. Might play out sometime if the right opportunity comes along.

Here's what I'm doing presently and it supports the reason so many professionals use this strategy. Including  psychonoodler, (You have a great tone and similar to the style I play. Better than me but keep practising, I'm nipping at your heals). Mixing amps and cabinets. It allows for construction of tone. Using a mixer allows for fine tuning the frequency response to the amp-cabinet combo.

I'm finding with the mixer approach the B-52 120 watt speakers in a sealed Carvin cabinet, (looks like Birch wood) are too Dark-Mushy- perhaps unresponsive. Perhaps they need to be driven with more like 20 watts before they come alive. At which point my eardrums would probably be ringing in the new year.

I studiously study these posts. They are improving my knowledge base of speaker design. Thanks everyone.

Onto the videos posted for review.

Silverfox.

[Ritchie200]

Going through an old guitar player from 2003 and saw an ad for this cabinet: Genz Benz GB212GFLEX.  Interesting in that it is ported to death.  It it also capable of stereo operation.  The "Flex" appears to be just a small horizontal "V" angle that the speakers are set on.  Looked at many reviews and they all are very favorable.  I tried to pull up some interior pics or plans but no dice.  I dont know if the interior is split or open.  The comments do say it is VERY heavy for a 2x12 so it must be split.  I like the handle design.  Anyway, just thought I would throw this out there for ideas.

Jim

http://www.genzbenz.com/?fa=detail&mid=1409&sid=419&cid=93

[silverfox]

I like it too. Depending on whether the ports are calculated or not- i.e. From what I've been told the diameter and even the length of the tube is fundamental to the bass frequency it outputs, this could be a very responsive cabinet.

Being stereo I too would expect it to be divided inside.

What about the phase of the compression coming out the tube vs the rarification being generated by the speaker cone? They would be out of phase and I would expect the air to rotate head over tails-tails over head, emanating from the cabinet.

On excursion, the front side of the cone would be pushing air while the port would be pulling air into the cabinet. Perhaps the air can't change phase that quickly and you instead get an algebraic sum in the transmitted pulse. Crazy??


as a silverfox.