harponica
45 posts
Jul 19, 2012
12:29 PM
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I have a newly built 25 watt harp specific tube amp.Original cabinet had two twelves.I made two reducer rings and amp now has two new Italian made Jensen P10R's.A certain video suggests upgrading a reissue bassman with two Jensen Jet Tornado's and leaving the other two P10R's .Jets are rated 100 watts each.Many options here,any suggestions?I am willing to change speaker brand and configuration."You gotta help me,I can't do it all by myself".
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spackle20
8 posts
Jul 19, 2012
12:40 PM
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General rule is you want to keep the impedance close to what the amp expects. With no load attached, voltages can rise (bad). With a dead short, your output transformer can take a beating.
If you need help calculating impedance, tell me the impedance of your speakers and how you have them connected (series / parallel).
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Since I learned to overblow, I don't use my car horn so much any more.
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Joe_L
1937 posts
Jul 19, 2012
1:05 PM
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David Barrett and Mark Overman both know good tone. I trust their judgement. If they recommend the Jensen Jets, I would try them. I wasn't a fan of the reissue P10R's in my reissue Bassman.
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The Blues Photo Gallery
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Rick Davis
536 posts
Jul 19, 2012
1:22 PM
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I agree with Joe_L.
Harponic, I'm not sure what you are asking... Are you looking for recommendations for 10-inch speakers with good tone in a 25-watt tube amp? If so, I would suggest you try one Eminence Lil' Buddy speaker. Hemp cone, big dark tone. I like it in both the VHT Special 6 and in the Bassman RI.
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-Rick Davis
Last Edited by on Jul 19, 2012 1:27 PM
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orphan
150 posts
Jul 19, 2012
1:23 PM
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Rick, are those eminence blue frames above the lil buddys?
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Rick Davis
537 posts
Jul 19, 2012
1:29 PM
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orphan, yes. They are original Fender Blue Alnico speakers, which are rebranded Eminence Legend 1028.
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-Rick Davis
Last Edited by on Jul 19, 2012 1:31 PM
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harponica
46 posts
Jul 19, 2012
1:48 PM
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Rick,Should I stay with one twelve and one ten,or two tens,should I mismatch the wattage outputs,should I go to webers,etc.I always have stayed with same wattage speakers,I don't really understand the theory of having different wattage speakers and having the threshold of feedback not the same in all speakers.
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Rick Davis
538 posts
Jul 19, 2012
2:19 PM
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harponica-
Hmmm, lots of questions there...
Many harp players (me included) like the sound of mismatched speakers in an amp: different sizes, magnet structures, impedance, and so on. It is often called speaker "blending."
There are very few rules. Try anything that you think might sound good. Tube amps can usually tolerate a 2:1 impedance imbalance, so you don't need to get too anal about that. If your total speaker load is, say, four ohms when your amp expects eight it is not likely to cause a problem.
Wattage rating on speakers are mostly meaningless.
What I mean is, you do not need to match the speaker wattage rating with the amp exactly.
One speaker spec that is important is efficiency or sensitivity... How many db of amplitude is generated by one watt of power measured at 1 meter from the amp. A bigger number -- such as 100db -- means the speaker will be louder with a given amount of power than a less efficient speaker. Weber and Jensen alnico speakers are less efficient: ~94db. The Eminence Lil Buddy is more efficient at 99.1db. It is a difference you can hear.
If it were my amp I would use a 10- and a 12-inch speaker. The 10-incher would be the Eminence Lil Buddy. For the 12-incher I'd try a Weber alnico Signature 12; it's only $45 and sounds good. Together, I think it would be killer tone for not much money.
But... speaker tone is VERY subjective and mysterious. I could sound like crap to you. Here's the secret: if it sounds good to you, it IS good, no matter what I or anybody else says.
Tinkering with amps is WAY fun. Have a blast, my friend. You will learn a lot.
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-Rick Davis
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harponica
47 posts
Jul 19, 2012
2:50 PM
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Rick,here's the scenario,two speakers in a cabinet with each having different weight magnets.The lighter magnet speaker will feed back before the heavier magnet when a mic is held with element side of mic facing speaker in close proximity.Therefore even though the heavier magnet speaker can take more wattage the lighter magnet speaker will not let the player do this because of the cone cry in the lighter magnet speaker.Apparently this result is desirable in a amp designed in this configuration.
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SuperBee
424 posts
Jul 19, 2012
4:56 PM
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Far out harponica, maybe that's true. But I dunno what it means. Where are you getting the information? Ive never considered feedback resistance or sensitivity to have any relationship with the speaker wattage rating. As far as I know it's about the sound going into the mic and being reamplified, setting up an oscillation. Related to the gain on the amp and the frequencies and volume hitting the mic. I wouldn't freak out about this speaker wattage stuff too much, but then again I'm probably displaying my ignorance. I have never heard the concept you discuss above.
If I have this right you are saying that, for a given amp/mic combination, a speaker of a higher wattage rating will have a lower tendency to cause feedback than a speaker of lower wattage? Where are you getting this info?
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Last Edited by on Jul 19, 2012 4:57 PM
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Rick Davis
539 posts
Jul 19, 2012
6:32 PM
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Not sure I agree...
A speaker with lower sensitivity will SEEM to feed back less since it is not as loud as other speakers, and a feedback loop is purely a function of amplitude.
And, what does cone cry have to do with it all, again?
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-Rick Davis
Last Edited by on Jul 19, 2012 6:33 PM
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Tuckster
1098 posts
Jul 19, 2012
6:42 PM
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I agree with Rick Davis. Differences in sensitivity is probably why the one speaker is feeding back sooner.
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SuperBee
427 posts
Jul 19, 2012
6:50 PM
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But practically the decibels at a given frequency are the same I suspect. It's not like you can get more volume before feedback by using a higher wattage or lower sensitivity speaker, just you might be able to turn the knob a tiny bit more.
For me, that's not gonna be a factor I'll consider much when selecting speakers
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Last Edited by on Jul 19, 2012 6:55 PM
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Tuckster
1100 posts
Jul 19, 2012
8:54 PM
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I was thinking about why someone would do that. Here's what I think: if you turn up enough, the lower wattage speakers will start to break up,but the higher wattage spkrs. will stay clean. The result would be some "dirt",but still have good detail or articulation. Just a theory. I could be completely off base.
Last Edited by on Jul 19, 2012 8:55 PM
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SuperBee
429 posts
Jul 19, 2012
9:23 PM
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I can understand that I think, but I don't know what it has to do with feedback.
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Tuckster
1101 posts
Jul 19, 2012
9:51 PM
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Yes, I don't either. I'd have to see the video O.P. was referring to.
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SuperBee
430 posts
Jul 19, 2012
10:00 PM
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i think it was a video from Bluesharmonica.com, where david barrett and mark overman were checking out different speakers and combinations of speakers in a Bassman RI. ive watched all those videos i think but i dont remember that bit!
Edit: No, i'm mistaken. i have no idea.
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Last Edited by on Jul 20, 2012 8:15 AM
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harponica
48 posts
Jul 20, 2012
9:42 AM
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I think leo Fender probably R&D'd this a while back about speaker configurations and thats why every Fender amp model has the same size speaker magnets.All of a sudden I'm seeing a harp specific theory that a heavier magnet affects tone.Of course a blend of different size speakers all with same wattage rating like a few early Gibsons I can agree with.There's alot of testing and measurement that goes in the design of speakers,and unless your an expert it is very had to have a in depth discussion,I'm just a backyard harplayer trying to throw a couple speakers in a custom made kick ass amp.
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harponica
49 posts
Jul 20, 2012
10:03 AM
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Here's the video about the 100 watt Jensen Jet Tornados.http://www.youtube.com/watch?v=Hkipkq09mNg
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