The Hundred-Buck Amp Challenge

[Printer2]

I myself am going for a sealed cabinet. The box is too small for an open back enclosure and I can push a little more low end out of the speaker than otherwise. Also the reason I could use a little more power.

[Wavebourn]

Do you mean it does not matter on which frequencies the speaker cab resonate, it is good?

[hunoz]

Originally Posted by tubelab.com

The cabinet does affect the sound.



BINGO! I made guitar cabinets a lot when I worked at an Olson electronics store and could get 12 inch Olson branded Utah speakers for $15 each. Make two identical cabinets one from plywood (or MDF) and the other from pine. Smack each one with a drum stick and listen to the difference. The MDF or plywood is dead it has no sound of its own. That's what you want for HiFi. A pine box will ring and resonate and yes size matters. Covering the pine box with thick material will deaden the sound. Look at the old Kustom cabinets. They were plywood covered with an inch of foam and a thick piece of Naugahyde. About as dead as a coffin. There is a reason why Tolex is thin.

I made box number 1 last week. As stated above it is about 12 by 14 inches and 9 inches deep. It will use an 8 inch cheap Peavey speaker. I will experiment with the back but unless the cabinet is dead or large you want it partially open with the hole near the center. A flat piece of pine behind the speaker and parallel to the front of the cabinet will send its sound right back through the speaker cone. This can create a uneven frequency response. I may use plywood for the back of my pine boxes. It's been over 40 years since I made guitar cabinets, so I just bought a bunch of cheap speakers and a lot of wood.

I am with you on the cabinets. I prefer 3/4" cedar or if needed to keep price down then pine. MDF, chipboard and plywood do not make good sounding speaker enclosures! Having said that the face can be made of MDF, chipboard or plywood without much change in sound if the box itself is made of cedar or pine.

I also agree on the effect on the sound of the covering materials used. So, choose what suits your preference for sound.

[tubelab.com]

Do you mean it does not matter on which frequencies the speaker cab resonate, it is good?

No, obviously it does affect the sound a lot. Back in 1970 when I made cabinets my brother and I tried a lot of stuff that didn't work. Mostly we just copied old amp cabinets. For some players a "dead" cabinet is desired.

Kustom sold a whole lot of amps in the early 70's. They are a big part of the unique sound that put Creedence Clearwater Revival on the top of the charts. Look for the shiny amps behind the lead singer with chrome ports in the cabinets. Note the Les Paul plugged directly into the amp with no processing. I used to have one of the same amps. They are solid state and very clean. Power amp circuit is a HiFi design right out of the 1969 RCA transistor manual.

‪Creedence Clearwater Revival - Bad Moon Rising (Live)‬‏ - YouTube

‪Creedence Clearwater Revival: Green River Live‬‏ - YouTube

Obviously that speaker cabinet is the result of endless hours of computer modeling.

I am sure many of the vintage amps we cherish were either hand tweaked, or "build it and try it". Computer modelling wasn't even a dream yet. Wait Computers weren't even a dream yet.

I started working in the Motorola plant in 1973. There was exactly 1 computer in the building. It was a giant IBM system that did payroll and other general business opreations. ALL engineering in this state of the art facillity was done by hand. PC board layout was tape on mylar and fancy photography. We had a totally awesome darkroom in house. It's a bit different now since my cell phone has more processing power than that IBM system did.

Note that most vintage combo amps were open back (for tube access) and many stand alone speaker cabinets were sealed. There was an Ampeg bass guitar system that used a quasi horn (V4B?). It launched the bass out into the audience. Bass was louder against the back wall of a large room than it was in the first row. The more popular SVT relied on 8 X 10 inch speakers and 400 watts.

[tubelab.com]

I love the smell of ferric chloride in the morning.

[Printer2]

Originally Posted by hunoz

I am with you on the cabinets. I prefer 3/4" cedar or if needed to keep price down then pine. MDF, chipboard and plywood do not make good sounding speaker enclosures! Having said that the face can be made of MDF, chipboard or plywood without much change in sound if the box itself is made of cedar or pine.

I also agree on the effect on the sound of the covering materials used. So, choose what suits your preference for sound.

Some owners replace the front baffles of newer amps because they were made from MDF and they feel the sound is too dead. Fender used to have their front baffle of their Tweed amps suspended by four screws, the baffle would continue to vibrate after the note started to decay.

On the topic of vibration and resonances, some acoustic feedback made its way back to the tubes in a combo. Depending on the tube there might be a fine line between enough or too much though.

[Fenris]

I prefer peroxide and HCl - it's less opaque, less staining, easier to procure, and (maybe?) less toxic.

[Michael Koster]

If the back opening of the cabinet is large enough vs it's internal volume to place the Helmholz resonance well below the lowest notes, then the enclosure should act like an open baffle and would be analyzed as such. There can be a lot of coloration depending on the 1/2 wave distance around the edge of the baffle. I would expect that and the driver characteristics to define the basic "sound" of the cabinet.

[Michael Koster]

Originally Posted by Wavebourn

Do you mean it does not matter on which frequencies the speaker cab resonate, it is good?

Hmm. The speaker cab response is not likely to be flat... Where it peaks and dips will create a sound that may or may not work with the instrument, player, and music being played. Sort of like a hollow body guitar. Clearly one doesn't want "wolf tones" or serious muffling of anything, but to some extent it just defines a unique sound, not good or bad.

One thing I have found is I can't predict what I will like from the response plot.

[simon7000]

The back of the cabinet has a top and bottom piece to act as braces! They have a bit of sonic effect, but without them the cases would break in rough use!