Isolation cabinet and speaker choice

[OsakaLoop]

I'm building two isolation cabinets based on the specs of the Randall boxes (outside dimensions 21" X 24" X 35"). I need to buy some suitable 12" speakers.

Question 1
I've heard two conflicting opinions on the kind of speakers that would be best to use. Some say that I should use speakers rated at least 50% more than the output of the power amp, while others say that if I use speakers rated lower, I will get better tone in isolation cabinets. What's the scoop?

Question 2
There were some older threads which dealt with isolation cabinet problems: lack of low end and boxy sound etc. None of the threads gave any indication if these problems were resolved by EQing or insulation material. Is anyone satisfied with the sound they are getting from their isolation boxes (speaker--not amp isolation boxes)? Does anyone have suggestions?

Background info:
My power amp is a groove tubes dual 75 (75 watts per channel). I'll be miking the cabinets with SM-57s going into a 1402VLZ. I play a broad range of music (Acoustic and AC/DC to old ZZ Top) so I want something as flexible as possible

I was considering something like the (Eminence) Texas Heat speakers. They are rated at 150 watts or so. Should I stick with lower output speakers like the Governors (75), or even go lower?

OsakaLoop

[CGibson]

I own the Randall Cab. and just love it.
I bought it when they first came out so it's loaded with a stock Randall speaker and not the celestion.
I've tried a few speakers in it and couldn't hear a noticeable difference in tone. The idea is to hold in all the sound and bombard the mic from every direction. This doesn't require much power at all to blast the mic.
I just kept the stock speaker in it since I couldn't decide what sounded best.

I've recorded hundreds of guitar players over the years using the Randall and every one of them just loved it.
Most of them said it was the best tone they've ever heard.
I primarily use it for a heavier rock sound; I don't care for it's clean tone or SRV brighter blues/funk tone.

It’s great to be able to record a guitar while people are able to talk in the same room.

I also have the bass unit but have never used it. Some day
I'll have to try it and give some feedback.

C

[grinder]

I built a iso cab, using Randalls' specs as a guide. I used a 25watt Celestion matched with my 100 watt Carvin head, because I like the sound of speaker distortion. I lined the inside with 2" acoustic foam to stop reflections and added a piece of 2" foam board in the top under the acoustic foam . It doesn't sound as good as a room miced cab, but it works well with some eqing. It's fairly quiet with and amp cranked and I can still get it to sustain/feedback.

[Imaduck]

To give my input on the answer to your first question, rating ratio is a bit up to you. If you want speaker distortion, you would be fine with buying speakers rated 0-25% above your amp rating. I would not go lower than your rating, however, as you run great risk of blowing your speakers (though, if you really love speaker distortion, using a lower rated speaker is possible). Also, using speakers closer to the amp rating will make them wear out faster, and you may find yourself replacing the speakers about once a year if you want some clean, good sound. If you need, loud, powerful, and undistorted sound, then going for speakers rated 50%+ over the amp would be my suggestion. Personally I prefer to have my speakers just reproduce my amp sound, ie little speaker distortion, so I've swithed to higher-rated speakers, but other people will swear by speaker distortion, so it's up to you.

I've heard a few players use those eminence's you mentioned and loved the tone. Also, I should mention that Celestions are probably by far some of the best speakers for obtaining speaker distortion if you go that route.

[OsakaLoop]

I'll see what I can find for speakers over here. The people who deal with Eminence in Japan haven't responded to my emails and not many people want to ship them over here, so I may end up using celestions, which are pretty easy to find here. I'll post back on how they work.

OLoop