Post Number: 2635
|Posted on Thursday, November 24, 2011 - 11:26 pm: |
I was having a play with my bi-amped rig yesterday as I haven't
got the big speakers out for a while.
Anyway I was reminded sonically when I put the Mesa 2x10 cab into the full range output that it;s speaker(s) had blown.
I can't really tell which of the two speakers have blown but will find out when I take the cab apart. I remember when it happened a good while ago but haven't had to use more than my 4x10 for gigs so it went out of mind.
Is it ok to just take the cab apart and individually disconnect the speakers to check or is there a simpler check?
Assuming the speaker has some problem, what is the best course of action.
(1) Get it repaired?
(2) Replace with a like for like speaker from Mesa Boogie
(3) Replace with a different (better) speaker. if this option is preferred will there be any problems sonically/loading by mixing two different speakers assuming one of the existing speakers are ok.
Post Number: 2154
|Posted on Friday, November 25, 2011 - 12:20 am: |
In an array of 10's or just 2X10's the drivers need to be identical in the same cabinet to meet design perimeters . I have two older Mesa "Road Ready 2X10's " and one 4X10 all the 10" drivers are EV's. I used to Biamp as well but recently have been playing full range in Stereo.
A simple check would be to listen at close range with reduced volume and slowly increase the volume as you play and listen for the tell tail distortion of the damaged driver and with keen ears try to tell which of the 2 is at fault .An audio signal generator is a great help for this process . Or , if one of the speakers is completely dead remove the speakers from the cabinet and apply a low gain signal to the terminals or a 9 volt battery intermittently and listen for a click and voice coil/ cone movement. If you have an OHM meter you can check to see if you get a reading ; a DC ohm meter will not read 8 ohms for an 8 ohm speaker but might indicate about 6 ohms or there about and a 16 ohm speaker 12 ohms or so. My 2 cents, I hope this helps and all the best to you . Mesa has used various drivers over the years so I do not know what might be in your cabinets but if you have cast frame speakers such as EV's it is worth a recone repair. If you can not get it reconed find an identical replacement and if you can not find an identical replacement replace both of the drivers to match.
Post Number: 1319
|Posted on Friday, November 25, 2011 - 3:19 pm: |
I blew up an EV speaker from my 2x10 (old Diesel type) and was told it couldn't be reconed to 16 ohm, after recone it would be 8 ohm...
I replaced it with a cheap Eminence speaker (this one) and it works fine for me for now.
I'm on the lookout for a 16 ohm EVM10 and until then will do with my quick solution (I hope) :-)
If you can get the new speaker reconed, it would be about 120 GBP I guess, new speaker from Mesa about twice that amount I think.
I've always wondered what kind of speakers Mesa uses today, could you take a picture?
The speakers in the Diesel cabinets were custom made (for Mesa) EVMs or Eden EC1060F, there are some pictures on my site: Click here (warning, lots of pictures, will take some time to load)
Hope you get it to work again soon!
Post Number: 2156
|Posted on Friday, November 25, 2011 - 6:33 pm: |
EBAY has some from time to time . I have had good luck with various sellers for the most part.http://www.ebay.com/itm/ElectroVoice-EVM10DLX-10-Loudspeaker-EV-10-300W-Made-USA-EVM-10DLX-Speaker-/250939836803?pt=Car_Speakers&hash=item3a6d2e0983#ht_500wt_1172
I purchased a NEW matched pair for spares a few months ago like these from another ebay seller . Mine are 16 ohms .
Post Number: 5
|Posted on Saturday, November 26, 2011 - 6:01 am: |
This may be of some help. I repaired my home stereo speakers by replacing the cones. Pretty easy procedure and suprisingly good sounding. Good Luck!
Post Number: 1779
|Posted on Saturday, November 26, 2011 - 6:36 am: |
I'd just take off the front grills and press on the cone part of the speaker (while not touching the dome in the middle): The good one should slide in/out smoothly, the bad one will probably make a sickening scraping sound and feel very scratchy as it moves.
Most 210 boxes are very similar in their size, venting, etc., so there's a lot of replacement speakers out there. And few manufacturers go to the expense of using totally different drivers for a 210, 410, 610, etc. I'd either recone or buy a new replacement to match the remaining OEM speaker, or I'd buy two new ones for this type of application. I would not begin, personally to mix and match and hope I'd get lucky tone wise, but that's me. As always, shop around for your best value.
J o e y
Post Number: 1083
|Posted on Tuesday, November 29, 2011 - 10:39 am: |
This probably a dumb question, but do speakers actually have the resistance values they seem to claim? That is, if I were to take a digital multimeter to the leads of a 16 ohm speaker, would it read 16 ohms? If so, does a blown 16 ohm speaker also read 16 ohms (it seems like it would), or is there something I'm missing?
Post Number: 2159
|Posted on Tuesday, November 29, 2011 - 11:11 am: |
AN 8 OHM speaker has a DCR (DC resistance) of aprox 6OHMS and like wise a 16 OHM will measure at aprox 12OHMS as I indicated in my above post #2154 If the Voice Coil burnt completely it will read opened or 0
Three things that affect speaker impedance:
1. Voice coil's electrical impedance (resistance, inductance, stray capacitance)
2. Driver's mechanical impedance (stiffness, mass, damping)
3. Driver's acoustic radiation impedance (resistance, reactance)
Obviously, because there are so many things that affect impedance of a driver, many manufacturers use conjugate techniques to accomplish a given "nominal" impedance. "Nominal" impedance is used to define an average impedance over the driver's frequency range. It is not a term recognized by the IEC. The IEC uses a concept called "rated value", which allows any "increase" above the rated value, but limits the "decrease". The standard does not allow the impedance to fall below the 80 % of the nominal value at any frequency, including DC.
Typically, you can guesstimate the nominal impedance of a driver by measuring the DC resistance and multiplying that value by 1.3. Example: Most 8 ohm drivers (<-nominal) will measure around 6 ohms DC. Not the most accurate method, but close and it doesn't require sophisticated equipment.
Post Number: 1712
|Posted on Tuesday, November 29, 2011 - 11:14 am: |
The speaker values are not resistance. They are for impedance. It can be a little confusing as both are measured in ohms. In layman's terms impedance is the AC equivalent to resistance in a DC circuit. The difference is impedance in AC requires the use of both resistance and reactance (a combination of capacitance and inductance).
When you use a multimeter you are measuring the DC resistance of the coil. This measurement will be less than the impedance for the speaker. For an 8 ohm speaker the resistance commonly falls around 6 ohms. For a 16 ohm speaker around 12 ohms. If you can measure resistance in these ranges it usually means the voice coil is intact (however not necessarily good). An infinite reading means the coil is bad. Zero ohms or a very low reading indicates a short (again not good).
Two common causes of blown bass speakers are over excursion and over heating. In both of these cases you may still be able to get a valid resistance reading from the voice coil although it is damaged. Generally the way you diagnose these is to gently push on the cone. The movement should feel smooth and you should not hear any scratching or scraping sounds.
(Message edited by keith_h on November 29, 2011)
Post Number: 1085
|Posted on Tuesday, November 29, 2011 - 11:15 am: |
Oops, reading failure. Thanks for the extensive info.
Post Number: 2160
|Posted on Tuesday, November 29, 2011 - 11:16 am: |
This is good to read for further comprehension of Resistance VS Impedance;http://www.physlink.com/education/askexperts/ae517.cfm
Post Number: 2161
|Posted on Tuesday, November 29, 2011 - 11:24 am: |
Yes Sir____ you betcha !, It is always my pleasure to serve my Brothers and Sisters with explanations and help if I can .
Post Number: 192
|Posted on Tuesday, November 29, 2011 - 3:12 pm: |
Note that when performing the "press on the cone" test it's important to apply relatively even pressure around the circumference of the voice coil. Uneven pressure can produce the dreaded scraping noise by moving the voice coil out of its normal path in the magnet gap. Speakers with very compliant suspensions are more subject to this.