Building a guitar cab , need help

[Ahmad_tbp]

hi everybody , i want to build a guitar cab for a friend of mine , the driver is Eminence patriot series , Black Powder guitar driver ,and it s on the way .
the main point is that, he s going to use this cab for recording , so i should get rid of any minimum freq resonance , i never design a cab , never worked with speakers parameters , so i hope i can build a suitable cab to have absolute original tone of speaker , with help of u guys .
if this help , i m goin to build a combo maybe ( like the pic i attached ) and the genre he s going to record with this cab is death metal , .and as i said this cab is for recording so he s goin to use it in door .
here s the link for speaker parameters : http://www.eminence.com/eminence/pag...iot/powder.htm
so wat s the best external diameter for cab section only ? ( the mdf thickness is 18 mm ) how much volume do i need ?
and here s sample of how it may be ( sure the amp section is completely seprated )
any idea for pre and amp is so wellcome too !!! ( i have a marshall jcm 800 tube pre with a solid state amp in mind ! )

[Nigel Goodwin]

A guitar cabinet is extremely non-critical, often open backed, with a poor frequency response - if you make it sound good he won't like it for guitar!.

Just look for a combo with a 1x12 in it, and make a box that size, leave it with a large opening at the rear, like the combo probably has!. As it's open backed the size and shape will make little difference.

Bass guitar is a VERY different affair, you need sealed or reflex cabinets to get the required low frequencies.

[Ahmad_tbp]

no it s for guitar not a bass guitar . and i saw lot s of combos that was sealed ! , and if i can put this speaker in any size of other 12" guitar cab , so wat bout t/s parameters ? wat if it resonance ?

[sreten]

Hi,

The application notes for the Black Powder indicate its for open backed use.

http://www.eminence.com/eminence/pag...tonalguide.htm

As Vas is not specified sealed use would be problematic to design.

/sreten.

[Ahmad_tbp]

thank u , so i have to go for a opened back , wat s ur suggest ?

[DrFrankenstein]

Actually guitar cabinets are where you get to have a bit of fun. I say don't build to specs, build based on the type of sound you want. I've built boxes to specs but with instruments, oversized always sound better to me.

Loose with broad volume and transparency?
Oversized cabinet with a partial or fully open back.

Tight and focused?
Smaller cabinet with a sealed or semi open back.

My most recent custom guitar cab consists of 4 10's and 2 broad range piezos. The bottom 10's are subs with a sealed back and partial divider between the speakers that leaves about a 3/4 inch gap in the back of the box. There is the slightest amount of cross talk between these 2 speakers which gives a mild mono effect that is very dark while still maintaining the stereo integrity. This is my favorite custom imrpovisation yet.

The top 10's are a couple of high wattage Jensen MOD's with a semi open back. A top panel extends down to about the middle of their magnets. They have a nice wide open sound but it's still nice and focused since they are 10's.

It's an oversized cabinet with a LOT of volume. I have a really open/wide yet focused sound. Sealed or open though, I always say go a little oversized with your cabinet regardless of specs. Oh and there is always the option of slapping some hinges on a panel so it can be open or sealed, another cool innovation I incorporated into a 4x12 cab.

[teemuk]

Originally posted by Nigel Goodwin
A guitar cabinet is extremely non-critical, often open backed, with a poor frequency response...

I wouldn't really mind about frequency response of a speaker cab - except for the low end. A guitar speaker with a cutoff frequency around 5kHz tends to be a quite limiting factor by itself already so they are not even intented to have "Hi-Fi" response. Still, Thiele-Small parameters and other design factors do affect on them and while especially open-back cabinets are lot more forgiving for bad designs one can't just mount the speaker into any box.

Where you really have to focus is the adequate size of the cabinet: I'm not experienced in cabinet building but i do know that open-backed cabinets which are too small will resonate quite annoyingly: Too small cabinet means a too small tunnel for airflow. When the tunnel is too small the air mass load is also too small and it won't lower the speaker's resonant frequency effectively enough. Anyway, most of the guitar cabinets intented for metal-style music are not open-backed since closed-back cabinets provide a tighter bass - which fits better for the genre.

If i would instruct you to copy a design from a combo amp that would be like saying: Copy a design which might be bad. Some combo amps tend to have too small cabinets since they are partially designed to impress with their compactiveness. I don't think it's reasonable to waste a lot of time and effort in building a cabinet that sounds mediocre or weak so you better spend more time on planning. Maybe you should enquire which cabinets are reputed of being good for the specific music genre you are after and then copy one of those designs.

[DrFrankenstein]

You want to hear the speaker more than you do the box, hence the poor design of most combo cabinets that have been used for easily the last 60 years

If you're reasonably experienced at building speaker cabinets in general, you can pretty much wing it as far as guitar cabinets are concered. The number one custom built musical instrument cabinet makers online don't use specs at all and tend to promote oversized cabinets.

I've built boxes to specs and off the basic dimensions of other guitar cabinets but have never been very impressed. You WANT a looser sound, this is music creation not music reproduction. You want a looser sound so it's more forgiving of the noises that surface in your playing. Something a cabinet built to specs with a very accurate focus is going to intensify.

When guys here talk about frequency response, they're really talking about resonation characteristics. What is said to be ideal based on measurements and meter readings doesn't in fact always sound that great no matter what type of cabinet you're building. I've heard a lot of different custom boxes and some of the best ones were thrown together with little calculations and based on mental imagry of how the sound is going to behave with certain compression and dampening characteristics of a boxes design.

In other words, don't over think it.
Find a design you like the sound of and base your cabinet off that. Oversized is better but since it's a single woofer, you definitely can't go overboard. Just read some dimensions online or in a guitar gear catalog, play through the speaker you have as a stand alone woofer and you should get a pretty good idea of the sound you will get out of it based on the cabinet designs you think up.

Trust me, specs are a lot of fooey anyways. You're basing a box off of analyzations rather than what simply sounds good to people's ears. You'll find more often than not, a cabinet with a bit of a looser feel will be favored by most listeners.
....Extreme focus and tight sound is for sh1tty pop music

[Ahmad_tbp]

thnx for replies ,
most of the one driver combos i seen , were sealed back ,.
I saw a marshall cab with one 12" driver , it was sealed back , and sounds good ...it was 520*400*275 mm , i like its sound , but i m afraidin if i use this diameters it rsonates the tone , or becomes too bassy ,.
wat do u think ?
and if i want to open the back how much should i open ?

[Ahmad_tbp]

hellllooo ...
so wat s ur idea bout these dmensions ?