How to make 1x12 closed back speaker cab sound better?

[vibratoking]

I have a cheap Lopoline 1x2 closed back cabinet. It has always sounded boxy and closed. I have tried many different speakers in it and it always basically sounds dead. I was reading a thread where Glenn and Cliff said front ported 1x12s sound good - at least some of them.

I know nothing about porting a cab, so I am looking for information/advice about how to port the cab. Any useful reference material? Info on past experiences? Suggestions? Can this cab be rescued or is it doomed to sound like s*%t forever?

[Gibsonman63]

I have a Mashall 1x12 cabinet that is closed back. There is about a 3" port in the front. For the Marshall amps it sounds fine. My Express clone makes this cabinet spit out the speaker cable. I made some new back pieces for it with about an 8" strip removed from the middle, just behind the speaker. It seems to open it up. With an open back cabinet or semi open, the wall behind the speaker has a dramatic effect on sound as well as proximity to the wall.

[rooster]

Yeah Gibsonman makes a good point - open the back up. I know the Lopo box and it is very small, maybe too small to benefit from front porting. For front porting to work well, you need some surface area that is not within a few inches of the speaker edge, 3" is good for example. I don't think you have that kind of surface area.

Now, if you play at really low volumes you could give it a go, put some 2" holes in two corners with a hole cutter bit, but as the speaker starts to really work your sound will suffer. For what you have there, modifying the back is the way and typically a 1 to 1 ratio of air to cabinet back on a small cab like the Lopo. But start small with the hole, think 'Dumble cutout' here maybe. BTW, my fav speaker in a cab this size - when the back is opened up - is a Weber Silver Bell ceramic, light dope, 75 watter.

[rdjones]

I have a cheap Lopoline 1x2 closed back cabinet. It has always sounded boxy and closed. I have tried many different speakers in it and it always basically sounds dead. I was reading a thread where Glenn and Cliff said front ported 1x12s sound good - at least some of them.

I know nothing about porting a cab, so I am looking for information/advice about how to port the cab. Any useful reference material? Info on past experiences? Suggestions? Can this cab be rescued or is it doomed to sound like s*%t forever?

This has everything to do with matching a speaker to it's enclosure.
Less so with an open back, and more so with a ported design.

It you're going to port a cabinet it needs to be done properly using the speaker's Theile-Small parameters.
Get this part wrong and you will have a system that's boomy at one note and dead a few notes higher or lower.

A popular example of a tuned ported cabinet design is the ElectroVoice TL806 used with the EVM12L.
The design is copied by Mesa/Boogie and BoogaFunk and is intended to be used with the EVM12L.
Use another speaker that doesn't have the same T-S parameters (or very nearly same) and it's not going to sound right.

The fact that you have tried several speakers with the same result shows that either the cab is too small or you haven't tried the right speaker, ie a speaker with a loose enough cone to not be restricted by the small sealed cab.

How big is the cab ?
Does it have the removable back ?
Is there any treatment internally, such as reinforcing strip across the back or batting ?
The cab is still going to be relatively "dead" but you might be able to tune it a bit without cutting holes yet, and find a different kind of "dead".

One sealed 1x12 cabinet I have had good results with was probably a bit larger than the Lopo, had the mentioned internal treatment and had a great speaker in it, an original SRO12.

I think your cure is going to be opening up the back.

reddog Steve

[Cliff Schecht]

I have an Egnater Rebel 1x12 extension cab I got for cheap and pulled the stock Celestion out. I think the speaker is special made for this cab and it's not a bad high wattage ceramic speaker but the SRO just plain kicks ass for making any bright amp sound smooth. Part of my equation is just this speaker, it sounds good with whatever I throw at it.

The ported closed back nature of the cab helps everything from getting too muddy and dark like your typical unported small 1x12 box does. I think the big trick is having some appreciable cubic volume inside the cab. Go look at one of these Egnater cabs in person, they're deeper and wider than your typical cheapo cab. If the cab is too thin then the low end gets muffled IME and I don't think just adding a port will solve your problems.

With that said I agree that opening up the back should be able to make that cab sound better. I like the idea of a Dumble style hole in the back (I recently did this on a 2x12 and really dig the results). Too much will cause you to lose all of your bass response IME (kinda like running a speaker out of the cab) but you can start small and open the hole a little bit at a time until you are happy.

With open back cabs I tend to put a duct tape X right across the center of the grille (right over the dust cap) to try to disperse some of the highs. Things can sound beamy in general when the dust cap is at ear level and open back cabs (being brighter in nature) can make things very shrill and unpleasant for an audience. Actually I do this pretty much anytime a speaker will be at ear level and turned up, otherwise your sound goes to crap.

[UR12]

I posted this in the other thread but will copy and paste it here

Just a thought on ported cabs vs the so called Theile cabs. Any ported enclosure that is designed around a particular speaker's Theile / Small parameters is a Theile cab. It makes no difference if the cab has a round port, square, oval, rectangular port, port in the front, port in the back 2 ports, 4 ports. The internal volume of the cab and the area and legnth of the port is dictated by the speaker's parameters and the frequency you want to tune the port/cab to. If a cab has a big oval port in the back that has not been calculated in size along with the proper internal cab volume to tune the cab to a particular frequency for a particular speaker then it is just an open back cab not a ported cab. If you do use a ported /theile cab then not all speakers will work efficiently because it's Theile parameters may not match that cab. The tuned ported cab will have a loading effect on the speaker (just like a properly built sealed cab) and will accentuate the speaker's own frequency response. So you really need to look at the speaker that you are just throwing into one of these ported cabs in order to get it to work and sound well. A celestion may sound awesome in a closed back 4 x 12 cab but could sound like pure crap in a Theile cab designed for another type speaker. Or say an EV12L may sound like crap in a closed back cab designed for some other speaker and sound wonderful in a ported cab designed just for it. Of course that doesn't keep anyone from trying a different speaker in their cab but before you write off that speaker as sounding like crap give it a little thought about what the cab was designed for and check out the manufacturer's specs. It may not be the speaker that is flawed but just your implementation.

While the EV12L may have what some are refering to a lot of treble, The TL806 is ported and tuned to 80 hz and the low end from that cabinet / speaker combination may sound more balanced than it would in a closed back 4 x12.

Theile Small explained

http://www.speakerplans.com/page89.html

[nickt]

One thing many folks miss is the EV cabinets were designed to go with an active filter that changed the bottom end. Basically flattening the 80Hz tuning but keeping the phase consistent or something. They were not designed to take a guitar amp as input and produce a great guitar sound. If they do then that's a happy accident.

I have never heard a TL808/9/whatever (the 12" one) but have built and used a whole bunch of the 15" version both for PA and a friend's bass. Back in the 70's 2xEV15L was the standard bass stack for a while at least in Oz.

Bottom line is what sounds good sounds good. Personally I like the EV12L's and have used one in an open backed cabinet forever but that's my taste and style. I prefer open backed because you can hear them on stage rather than 15' into the audience.

[Bob Simpson]

Pull the speaker and stuff the cab with Hollo-fill ( or equivalent... )

Makes the speaker think the cab is bigger.

Have you checked with Lopo about how they would port it?

Bob Simpson

[Bob S]

I have 2 undersized 2 x 12 cabs - one with G12m/G12H. Open back & between 1 & 1.5" from the wall it sounds good at low,med & high lead guitar frequencies. The other has a G12M & a Celestion Blue with a partially open back - maybe 20%. I prefer the 12M / 12H mix.
The dynamics of air movement are complex.
I do like an oversize 4 x 12 closed back with JBL's.
I guess the type of speaker drives the cab choice.

[Aurora]

Speakers and cabs interacts in a rather intimate relationship. this goes for both reflex and closed cabs. As already said, "Thiele cabs" refers to cabs designed in accordance with the deisgn framework based on the so-called Thiele-Small parameters used to characterize loudspeaker elements these days.

The most important parameters are the Qt value, which depicts the mechanical suspension elasticity of the surround and rear suspension, which acts a set of parallelled springs with different characteristics. This value is slightly modified by the electrical characteristics of the voice coil and magnet, sometimes referred to as "motor strength" or BL. The other mostly important parameter is the Vas - equivalent air supensio volume - a theoretical "ideal" volume calculated from the other parameters. Free air resonant frequency - Fr- is the resonant frequency resulting from all these and some other parameters.

Cab type, as closed, reflex or open back, will mostly affect the range from low mid and upwards, - say from roughly 100 Hz and upwards in frequency. A2 is 110 Hz. From here and upwards, tone is mostly a character of the element itself, and little dependant of the cab type or size. Fully stuffing a cab is usually concidered no good, and is often said to dull the tone. Stuffing is usually done to supress internal reflections to interact with the membrane itself. The apparent increase in volume is mainly a side effect, due to the slowing down of the sound or air speed through the "stuffing".

The cab type along with Qt and the free air resonant frequency Fr, will determine the frequency response or roll off from roughly 80-100 Hz and downwards. Reflex type cabs usually have a better and extended low frequency or bass response compared to closed cabs, but this determined by the Qt and Vas values, and ultimately the actual cab volume.

The typical open back cabs used with guitar amps are somewhat of a step child in this context, as they really don't adherre to modern design parameters at all, - the length of the port or opening, usually the panel thickness, is to short to be used as a reflex port. If one inputs port length ( panel thickness - 3/4" ? ) and port area into the modern formulaes, it meakes no sense. A thickness variation of 0.1mm ( 0.004") shifts the tuning frequency almost a full octave. Add to that fact that the more popular elements for guitar, like Celestions, Eminence etc don't have published T/S parameters, and the few I have found indicates Qt values much higher ( 0.8-1.2) than normally usable for reflex cabs. This really puts then into the calss oof open baffle, or rather open back in this case. The math work indicates that elements with Qt values in the range of .2-.4 being mostly suited to reflex and Qt from roughly .4-0.6 are better suitreed to closed cab work. The large ported open back cabs seems to a reminicence og 50's loudspeaker ideas, where the reflex port were ususally set to the same area as the membrane area - typical values used with the large console radio and grammophone cabs from the 50s and 60s.
If there's more interest in this, I can elaborate further...

[leadfootdriver]

I had the small Lopo 1x12. It was unusable. I should have bought the large 1x12. On the other hand, I also bought a Lopo 2x12 vert slant, and it's great.

[img768]http://i258.photobucket.com/albums/hh26 ... G_0040.jpg[/img]

[vibratoking]

Thanks for all the information guys. This community always comes through with great ideas and information.

How big is the cab ?

15" high x 11" deep x 17"1/2 long and weighs 18 pounds.

Does it have the removable back ?

No

Is there any treatment internally, such as reinforcing strip across te back or batting ?

No internal batting. No reinforcement that I am aware. What would you specifically suggest. It appears there is mixed opinion on batting.

The cab is still going to be relatively "dead" but you might be able to tune it a bit without cutting holes yet, and find a different kind of "dead".

Yea, I'm just looking for a better version of dead at this point.

[M Fowler]

I have that Lopo slant 212 verticle cab myself loaded with Scumbacks sounds great.

Mark

[vibratoking]

That Lopo slant 2x12 sure sounds great...Sure guys, keep rubbing it in. My 1x12 don't sound that great. I need to get out the board stretcher.

[brewdude]

I have a small 1x12 open back Lopo cab loaded with a WGS V-30 clone. It sounds kind of boxy and boomy. I don't like it at all. I won't buy an undersized cab again.

I tried the same speaker in a much larger Dumble style 1x12 oval back cab and it had virtually no bass response. I have been led to believe that this speaker would be better suited to a much larger closed back cab.

Is there a speaker that is better suited for such a small cab? Closed back? Open back?