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Post subject: 65 reissue twin reverb speakers question
Posted: Wed Sep 29, 2010 9:08 pm
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I have the opportunity to replaced the special design for fender eminence speakers on my twin reverb with Rola Celestion G12 80's. Does anyone here have any experience or feedback regarding these speakers? They are 15 ohm speakers, so would I have any issues with installing them in parallel for total impedance of 8 ohms? I saw that the twin calls for a 4 ohm load, I don't want to blow something.
Thanks in advance.

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Posted: Wed Sep 29, 2010 9:19 pm
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Your amp will not develop its full 85-watt output with a 7.5Ω load. Aside from that, you should expect no problems.

Arjay

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Post subject: 65 TRRI speaker
Posted: Wed Sep 29, 2010 10:12 pm
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Agree with Retroverbial, 7.5 ohm load, no problem. :) I just got an extension cab with a Celestion G12P-80 speaker, 8 ohm. Maybe they are similar, except the ohms? 15 ohms sounds unusual. The speaker is dark sounding compared to other speakers that I have, with great low end, but muted highs. The more amps that I try it with, the more I like it for it's driven sound. It does really well with a lot of drive/distortion, making it warmer and less harsh. To me it sounds too dark for the clean channels so far, but I've only had it for about a week. The speaker may loosen up after awhile, but I don't know if that will make the highs any better. :)

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Post subject: Re: 65 TRRI speaker
Posted: Thu Sep 30, 2010 7:15 am
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shimmilou wrote:
Agree with Retroverbial, 7.5 ohm load, no problem. :) I just got an extension cab with a Celestion G12P-80 speaker, 8 ohm. Maybe they are similar, except the ohms? 15 ohms sounds unusual. The speaker is dark sounding compared to other speakers that I have, with great low end, but muted highs. The more amps that I try it with, the more I like it for it's driven sound. It does really well with a lot of drive/distortion, making it warmer and less harsh. To me it sounds too dark for the clean channels so far, but I've only had it for about a week. The speaker may loosen up after awhile, but I don't know if that will make the highs any better. :)


Is your extension cab closed back? Do you think the speakers would be a bit brighter with less muted high end if installed in the twins open back configuartion? Just a thought.

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Posted: Thu Sep 30, 2010 7:21 am
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Retroverbial wrote:
Your amp will not develop its full 85-watt output with a 7.5Ω load. Aside from that, you should expect no problems.

Arjay


Arjay,
I dont think that I will ever use my twin to its full potential :cry: . I rarely have the volume knob set above 3. So not being able to utilize the full 85 watts is ok with me. Does this make sense? Also, would it make sense that this might be a solution to the infamous "my amp is too loud" scenerio? Not being able to utilize the entire 85w. :wink:

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Post subject: Re: 65 TRRI speaker
Posted: Thu Sep 30, 2010 7:44 am
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fender323 wrote:
Is your extension cab closed back? Do you think the speakers would be a bit brighter with less muted high end if installed in the twins open back configuration? Just a thought.


Yes, it is completely closed back. It is the Hot Rod Deluxe Extension Cab. You're right, it probably would sound brighter with the back off of it, I'll have to try it and see. Thanks! It might be awhile before I try removing the back panel, I am really getting some awesome tone using the BJr cranked wide open with this speaker. The smooth tone and sustaining feedback is absolutely amazing with my modified BJr. Maybe a little too amazing. While playing last night, the V1 12AX7 went microphonic on me (the speaker cab was 3 feet away from the amp!). I thought I heard an extra ringing noise while playing, so I turned the guitar vol down and could still hear the ringing, it slowly got louder on it's own and I could stop the ringing by grasping the V1 tube. Funny thing is, I already had 2 tube dampeners on it (put dampeners on all of the tubes). I replaced the tube and continued jamming til the wee hours. I promise to try the cab with the back off, but I'm sure that you are right about the open back sounding brighter. :)

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Post subject: Re: 65 TRRI speaker
Posted: Thu Sep 30, 2010 9:08 am
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shimmilou wrote:
but I'm sure that you are right about the open back sounding brighter. :)


Bass-reflex enclosures are typified by enhanced response at the lower end of the spectrum, which is why infinite-baffle cabs with their open-back design are seldom utilized for bass guitar. Bass reflex cabs are more directional though, with a significant drop-off in perceived volume when the off-axis angle exceeds roughly 40 degrees.

Arjay

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Post subject: Ext cab bass response
Posted: Thu Sep 30, 2010 9:22 am
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Retroverbial, I've considered a port for the cab on the back, as it would look good, but I'm not sure if that would be enough of an opening to enhance the highs or not. I used to build/rebuild speaker cabinets for home stereos, and we would almost always port the cabinets, using some forgotten calculations for length and diameter based on cabinet size, but haven't done that in years, kind of hazy..... Should I cut part of the panel off instead? Any advice on how much of an opening I need to bring out the highs? :)

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Posted: Thu Sep 30, 2010 10:32 am
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The size of the port would be contingent upon the internal volume of the cabinet and the free-air resonant frequency of the specific speaker. Consulting the data in Abe Cohen's handbook, the equation seems to work out to a baffle port some 2.25 inches in diameter, based on my estimation of a 3.5 cubic-foot enclosure and a speaker with a resonant frequency of 80 Hz. Bear in mind, the info in this book ("Hi-Fi Loudspeakers And Enclosures") is basically intended for stereo and PA systems. Thus, it may not directly correlate to the needs of the guitarist.

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Arjay

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Post subject: Twin Reverb speakers
Posted: Thu Sep 30, 2010 5:08 pm
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Well, as you probably guessed, I had to try the cab with the back off. It really balanced the sound and response of the Celestion speaker, bringing out the highs while still retaining a lot of low end. It still has a really rich smooth sound, but with noticeably better highs. The highs were definitely enhanced, but never got harsh. Now, turning up the treble on the amp actually helped give better highs. Before opening the cab up, the treble was at 12 and still sounded muted. The low end is not quite as tight as it was, it went from kidney-punching thump, to a looser, nut-tickling low.

The BJr still sounds great with this cab, just a little better on the highs when playing clean. The Celestion speaker is still richer and warmer than the stock Eminence in the BJr and the HRDlx, but opening the cabinet really helped bring out the highs. After playing the Celestion for a while with a few different amps, and getting the settings right, the Eminence almost sounds harsh in comparison, had to turn the treble back down with the stock speakers. With the back off of the cabinet, it is a much better compliment to the HRDlx speaker using them together, very much nicer than with the back on.

Retroverbial, that was a close estimation of the cabinet volume, I might try the port, but I think that I also might cut the lower 1/4 of the back panel, between the screws, keeping most of the panel on, giving me the option to put the piece back on to close the cabinet if needed. Overall, I'm much more satisfied with the speaker sound when the back is off of the cab. Definitely better highs. :D

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Posted: Thu Sep 30, 2010 6:01 pm
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I suspected that opening the cab a bit would enhance the mids and highs. You might give some thought to keeping the stock back panel intact (for resale purposes at a later date) and building an all-new one with an oval cut out of the center. Cabinets generally fare better during handling and transit if there is a rear panel to strengthen the corner joints, much like Avatar and some of the other custom enclosure companies favor.

Glad to hear you're getting the tone you need, rawk on.

Arjay

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Post subject: 65 TR speakers
Posted: Thu Sep 30, 2010 6:24 pm
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Good idea to keep the stock panel intact. I have some nice 1/2 inch plywood that I can use. I might even look for a solid piece of pine to use instead. I'll probably stain it walnut though, I really don't want to learn about/mess with gluing vinyl on. Or, black paint might look nice too. Looks like I have yet another project now. :D

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Posted: Thu Sep 30, 2010 6:35 pm
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Working with Tolex is actually pretty easy. But you have to buy it by the full linear or running yard. You're probably needing only five square feet or so. Bummer!

The plywood would probably be more resistant to damage from vibration or rough handling than solid pine.

Shoot some pics and post them as the work progresses.

Arjay

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