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Speaker size increase...is it worth it??

Started by PoorOtis, March 18, 2015, 12:42:43 PM

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PoorOtis

I have a older Peavey Studio Plus 110/65watt..I think it does a good job..for what it is! My grandson is using the amp until he decides what he wants in a new amp. The other guys in his garage band want to "Mod" my amp by installing a larger 12 in speaker in it...something about "Fullness"...or what ever?? Being a 65 watt amp, it has enough power to push a larger speaker..but my question is would it be worth it to install a larger speaker or leave the old amp as is...???? Can a new speaker in a larger size make that much difference in the amps abilities or over-all tone??  Thanks.

Roly

Gawd, simple and well stated question that opens a real can of worms.


Quote from: PoorOtis...something about "Fullness"...
...
Can a new speaker in a larger size make that much difference in the amps abilities or over-all tone??

Well, ya know, that depends, ... but mainly ... um ... "bollocks".

I suspect that this is more about trying stuff and seeing what happens, and you may feel inclined to indulge this a bit, but as for "tone"...


So what has it got in it now?  A 10-inch?

A great deal of the tonality of an amp is tied to the case/speaker enclosure.  The combo style is practical, but normally quite a compromise as far as being a speaker cabinet is concerned.

Rather than changing the speaker you could borrow some other speaker cabs and try them out with the amp at practice sessions.  "Fullness" suggests to me a pair of 12's in a sealed enclosure.
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

it is a 1x10" combo amp.  I am not near my schematic files, or I'd look it up.

Fitting a 12" speaker into it might not even be feasible.  If it is a front mount, the hole will be too small, if it is a rear mount, the 12" would be playing through a 10" hole anyway.  The amp is rated only to 8 ohms, the internal speaker impedance, and there is no external/extension speaker jack.  I do not recommend adding an outboard speaker.  However one COULD disconnect the internal speaker and wire a jack so as to power some external cab.

A note about speaker size:  "enough power to push a larger speaker" shows you are not clear on speaker power needs.  There are 10" speakers that are rated for and can handle 500 watts, and there are 12" speakers that can handle no more than 25 watts.  EVery speaker has an efficiency rating - how loud it is for a given power input.  If you wedged a 12" into the amp, it could be either more or less efficient than that 10".  Or for that matter exactly the same.  A larger speaker, all else being equal, would move more air, but different efficiency could more than counter that.  After all a 50 watt Marshall head screams through a stack of 4x12 cabs.

Do 10 and 12 inch speakers sound different?  yes they do.  But it isn't some standard where we can say that aall 12s are so and so while all 10s are this and that.

If you disconnect the internal speaker and connect the amp to a cab, you will probably find it has a bigger sound.  Ever see those little battery amps the size of a cigarette pack?  Connect one of those to a 4x12 cab and anyone who hears it will be amazed.  This amp through a 4x12 will sound like a different amp.

But also, speakers are not generic.  If the boys have some specific 12" in mind, that is one thing, but just having some 12 laying about the garage is no guarantee the thing will sound good.  So much more goes into it.  One major difference is the cab itself.  AN open back cab sounds different from a closed back (sealed) cab.

Frankly I think the guys are full of baloney.  You have a nice little basic amp here, I see no reason to screw it up trying to cram an oversize speaker into it.  For the price of a new 12" speaker, someone could buy a reasonable used guitar amp complete, even one with a 12" speaker.

They want to experiment on your amp.  He is using it until he "decides what he wants" in an amp.  Ask how many amps he has actually played through and what about them he has so far found that he likes and dislikes.

Roly

{you're evil  8| }


Quote from: EnzoThey want to experiment on your amp.

Yup, and I don't think that's a good idea either.   ::)


Borrow and try some other cabs/amps.  If he wants to still use the Peavey as a front end with preamp, EQ and Fx then you can always patch the Fx Send to the Fx Return (or input) on a slave under test.

I'd be on the lookout for a sealed 2x12 that you can borrow to try out, either with its own head, or drive cobbled from the Peavey (but be very careful of output shorts - not for even a moment or you may kill the output stage.)




As a generality the bandwidth of a 12-inch will be slightly lower set than a 10-inch, go a little lower in frequency but also not quite as high, but as Enzo implies, there are exceptions to every speaker "rule" and the driver model manufacturers spec sheet is the final word.

The raw power rating of a driver is a measure of its robustness, and not much else.  While this relates to suspension and cone toughness, in high power drivers these days it mainly relates to how well the voice coil can get rid of waste heat before melting.

The sensitivity is an important parameter that often gets overlooked.  This is the number of dBSPL that the driver can deliver for one watt in, at 1m range on the centreline (in an anechoic environment, such as a large paddock.  ).  How good it is at converting electricity into sound.  This is given in dB/W and the higher the better.  95dB/W is pretty poor, 100dB/W is good, and 105dB/W is very good, so being a logarithmic measure it is a very sensitive function, every extra dB counts.




Why a "sealed 2x12"?

Keyword: "fullness".  Experience shows that a difference between an open-back combo and a sealed cab is that the combo tends to be brighter, and the sealed cab has less tops but more "body".

There are all sorts of reasons for this, back radiation and such, but basically an open-back combo enclosure has a passband that looks like the Swiss Alps, and that it has a fairly high low-end cutoff.

A sealed enclosure by contrast generally has a pretty smooth passband response, and will typically go a bit lower before it starts to roll off.

My last unsupported assertion is that more cone area is good.  Take just about any audio toy, 1W ciggi box amp, MP3 pod, &c&c, and hook it up to a big guitar cab like a Marshall stack, and be astonished.

{When I was churning out hand-held AM radios they sounded awful, until you plugged the bench speaker box into the headphone socket, and you had very respectable full bandwidth reproduction.  It's just that the inbuilt 2" speaker and tiny case just weren't up it.}
If you say theory and practice don't agree you haven't applied enough theory.

phatt

While you are on this subject and without derailing this much just a side Q if I may?

Re the deebee watts thang.
I've read that plus 3dB is x2 louder.
Q, From that rule of thumb, Would I be right in assuming that a speaker with a 103 dB is twice as loud as a speaker with a 100 dB rating?

Does that then imply a 106 dB is x4 louder than a 100 dB?

I feel as if I'm missing something here so any help would be most welcome as no matter which way I step in this forest of maths I'm always tripping over logs. (sorry, sad attempt at humor). :-X
Phil.

Roly

Quote from: joecool85For every 10db gain (double perceived volume) you need a 10x multiplication of wattage.  So a 100watt amp is only twice as loud as a 10watt amp.

...


Speaker sens. (1dB/W@1m) Required power (watts)
104db1
101db2
98db3
95db6
92db12
89db24
86db48
83db96
80db191
77db382
See: Watts vs Volume (db)

Quote from: http://www.gcaudio.com/resources/howtos/voltageloudness.html

                     
                       
                       
                       
                       
                       
                       
dB ChangeVoltagePowerLoudness
31.4X2X1.23X
62.04.01.52
103.16102
20101004
4010010,00016

If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

#6
Short answer: yes .

But there's a can of worms being opened.

a) the main one: HOW were those db's measured.

Everybody and his brother cheats and lies to begin with, the simplest way even by "honest" people being that they measure in a different way.

Personally I only believe the boring Engineering "classic" definition ... which does not yield the exciting numbers the Marketing guys want.

Which would be: feeding the speaker pink noise, bandwidth limited to the rated expected use (no sense in feeding 100 Hz to a tweeter or 10 kHz to a woofer) , sticking a calibrated microphone or SPL meter 1 meter away and reading the display.
READING_THE_DISPLAY? ..... has Juan gone MAD?  :lmao:

Practically nobody does that ;) for the above mentioned reasons.

Instead, they sweep the speaker, look at some peak here and there (speakers are bumpy spikey as h*ll)  and pick some which looks good.

Practical example, a very common Eminence speaker, the Legend 1258:

http://www.eminence.com/pdf/Legend_1258.pdf

the datasheet states, without blushing and looking at you straight in the eye:

QuoteEminence Legend 1258
Usable Frequency Range        80 Hz – 4.0 kHz
Sensitivity***                        100.1 dB

100.1dB my *ss !!!!  :loco

this is the actual frequency response, published by them:



to begin with:
* at 80 Hz they show just 92.5dB
* at 4kHz just 95 dB

so far , that can be forgiven, it's the rated frequency extreme both high and low, and it's implied that below or above them the speaker must no be used.
Fine.

But, over most of the frequency response , including very important lows and mids
it firmly stays way below 100dB  :o  , not an occasional dip here and there which can be forgiven but all over the place.

From 100Hz to 800Hz the average is around a much more reasonable 96dB, with a narrow peak of 101.5dB at 1 kHz and a very piercing and annoying 108 dB one at 2 kHz.

Granted, it will make the guitar heard, but it;s a narrow mid/highs peak, not representative of the whole frequency response.

To avoid endless arguments, best is to feed pink noise and let the speaker itself average it, so whatever you read is, at least, honest.

But here I don't even imagine why they chose 100.1 dB over any other point, specially since it's there only at 800Hz , 1400Hz and 3800Hz ; above only in 2 peaks and way below everywhere else.

b) how can they legally print this?

Well, look that the sensitivity rating is labelled with ***
QuoteSensitivity***
which in any contract tends to mean: "here I say something, but go read the small print which says something very different" .

to begin with, the first " *  " leads you to:
Quote
* See footnotes on page 2 for information regarding nominal impedance, power rating and sensitivity

Quote*** The average output across the usable frequency range when applying 1W/1m into the
nominal impedance. i.e: 2.83V/8Ω, 4V/16Ω.
Eminence response curves are measured
under the following conditions: All speakers are tested at 1W/1m using a variety of test
set-ups for the appropriate impedance | LMS using 0.25" supplied microphone (software
calibrated) mounted 1m from wall/baffle | 2 ft. x 2 ft. baffle is built into the wall with
the speaker mounted flush against a steel ring for minimum diffraction | Carver PM-120
amplifier | 2700 cu. ft. chamber with fiberglass on all six surfaces (three with custommade
wedges).

2700 cu Ft translates to a 14x14x14 ft room, not bad, but low frequency wavelengths are larger than the room itself !!!!!
That room can be trusted above 100 or 150Hz, but not below.

here's 3 tricks here:

a) they do not explain how they mathematically "average" (as I said before, the honest way is to feed pink noise and let the speaker average it, clearly not the case here because result would have been around 97dB)

b) they use the "nominal" impedance.
At important mid frequencies (around 400Hz) the speaker has less than 8 ohms , pulls more than 1 W from the driving amp, that inflates results.
Some speakers state both "1 (true) W 1m " and "2.83V/8 ohms" which is the "nominal" side.
FWIW both numbers do not match, the "nominal" one being always higher.

c) they use LMS System which often "massages" results into nicer looking numbers.

LMS is a not too expensive speaker measurement pack, composed of a calibrated microphone, a dedicated PC plug-in board and accompanying software.

They've dropped them now from the datasheets, since obviously could get away with it, but older Eminence datasheets showed 2 very important issues:

* measurements are *calculated*  rather than plain *measured*  (meaning that they apply some number crunching , yet don't explain the algorithm used).

* as literally written: "measurements are made in Pi space" which of course is basic Chinese to most everybody (substitute Basque or Quechua for our Chinese readers).

What this actually means, is that full space, all around the speaker or a cabinet, is mathematically "2 Pi space" .
Mids and highs in general go forward but bass tends to go all around.

Clearly demonstrated by standing behind a speaker cabinet: sound is muddy and rumbling, highs go forward; bass spreads all over the place (what weakens it) .

Now if you build a huge wall, or go to a mountain , get a cave, close its mouth with a sheet of plywood and mount the speaker there, bass can't sneak behind (behind is blocked)  and is forced to go forward.

Instant 3 dB boost in low mids and lows.

In the old days (think 40's JBL, Altec and EV or late 50's AR) building a proper anechoic chamber was expensive (it is still so today)  and unles of monster size (think a plane hangar or NY main railway station)  it is not really anechoic at low frequencies so an accepted substitute was to dig a large hole in the ground, close it with the proverbial plywood sheet, mount the speaker pointing at the sky and suspending the microphone from a wire hung between posta at a convenient altitude.

No kidding.

It had the additional advantage of adding "free" 3dB to lows or low mids.

LMS does not explain how they do it, and doubt Eminence has an open air chamber (in fact they state they do have a real anechoic chamber)  , but LMS offers a software calibrated "PI/halfspace" mode, which I guess plain adds 3dB to low frequency measurements and calls it a day.

Not actual cheating because they state how they measure ... but 99.99% Musicians just "read the number" on the front page and take it at face value.

FWIW in many Forums it's common now to read "Eminence ratings seem too good to be true" , "they are inflated" , etc. which is tested by Musicians in a very simple way: they put 2 speakers in a cabinet or side by side, play a couple chords with each, and clearly notice thet "100dB Eminence" and "100dB Celestion" are NOT the same, with Celestion being the clear winner.

Not dissing Eminence at all, they make excellent speakers and are the de facto Industry standard, just that now I derate any and all of them by 3 dB and that makes published numbers more realistic.

Peavey who are very honest and straightforward with their ratings got so fed up with this "numbers game" that they published a Paper, read it carefully and you'll open your eyes like breakfast plates:

http://peavey.com/support/technotes/concepts/THE_LOUDSPEAKER_SPEC_SHEET_GAME_2005.pdf

g1

Quote from: phatt on March 19, 2015, 04:57:14 AM
Re the deebee watts thang.
I've read that plus 3dB is x2 louder.
Q, From that rule of thumb, Would I be right in assuming that a speaker with a 103 dB is twice as loud as a speaker with a 100 dB rating?
10db is generally considered as sounding "twice as loud" to our ears.
I think maybe you read that a 3db gain was equivalent to having an amp of 2X the power?
That is true, doubling the power of  amp (ex.50w to 100w head) will give 3db increase, the equivalent of a speaker that has 3db better sensitivity.

Enzo

Right^^

Phatt, you have that backwards.  3db is not 2x louder.  2x the power is 3db louder, and that is very different.  a 3db increase in loudness is a small change, essentially enough to notice, but not a lot more.

The lesson is that power is not loudness.   So when someone asks how to double his output power so he will be louder on stage, he is not headed for success.

Roly

Great post JM!  Thank you for that in depth consideration.  I'm educated.

Quote from: J M Faheyan accepted substitute was to dig a large hole in the ground, close it with the proverbial plywood sheet, mount the speaker pointing at the sky and suspending the microphone from a wire hung between post at a convenient altitude.

There was a time when I had a rather large paddock next to my workshop at my disposal.   ;)

No kidding.


Quote from: EnzoThe lesson is that power is not loudness.   So when someone asks how to double his output power so he will be louder on stage, he is not headed for success.

Which I think is why I'm still so hung on horns - they are quite a magic trick.   <3)
If you say theory and practice don't agree you haven't applied enough theory.

QReuCk

Of course, I cannot add much than "read again and carefully what these guys said, they are very well versed in all those stuff", but there is some additional thing that always annoyed me regarding all these db and wattage things:
Rating are already not so perfect for 1W. Still all we have is a rating with a 1W program, while we are often feading them with way more than 1W.
And guess what: I see absolutely no reason why a 25W rated speaker would have the exact same efficiency at 1W and at, say, 20W. It's a well known fact that guitar speakers tend to distort when approaching their limits. It's even considered as an interesting effect by some and guitar speakers tend to be made so that this start of distortion is not destructive for the device. On an electro-mechanical device distortion always equates to lower efficiency. It might be a good thing, though: I suspect this lower efficiency at the limits might be partially linked with cone velocity and as such be more pronounced on those pesky high frequencies - especially with a heavier speaker cone.
So I would say the SPL rating should read nnn db AT 1W and not nnn db/W, and the curve itself should be taken with a big pinch of salt if you intend to use the speaker attached to a power amp that can output close to your speakers rating.
The values might be representative enough if you stay well bellow the maximum wattage the speaker can accept though, but I suspect at least the efficiency in highest frequencies is affected way before what most people have in mind.

I might be wrong though, so wait 'till those knowledgeable guys correct me before making your own conclusions.

phatt

Thanks g1 yes I get a lot of stuff like this back to front inside out and upside down. I think I started too late in life to take on the many intricate details of this intriguing hobby.

A prize for Enzo, who was able to decipher my mental scrabble and work out I said it backwards. Thanks Mate you are a Gem. :tu:

A big hug for JMF for going to so much trouble and I read the Peavey link,
Actually the last few lines were likely the most useful to a novice like me.
Obviously whatever the dB number on the data sheet,, it could be off by 10dB.
As you say a lot of massaging of numbers goes on to make things look better than they really are.

I actually got caught out when reading product numbers a while back,, I read 120dB as being the 1 Mtr/1 Watt test but finally realized they were talking music power Not speaker sensitivity. durh
Just the way product brochures are worded and presented can be very misleading/confusing.
Hey at least I had stored enough basic understanding over the years and alarm bells went off because 120dB was way above most other gear so I went back to the shop and reread the data. The guy in the shop had it wrong.

And big truck load of thanks Roly (who must wear out keyboards on a weekly basis) ;)
I read "Galen Carols page" Yes Datzit,, that is the chart I needed. :dbtu:
I'll print that little chart for the special interest folder I keep in the bottom draw.

And I hope this all helps Poorotis. :tu:
Phil.

Roly

QReuCk

"Power compression", voice coil heating, &c; I'm sure JMF has more observations...




phatt

I have a laundry and shed full of spare 'puter everythings.  In bulk.  :lmao:


(Gerald, the extra RAM)

My mom was a teacher and writer, so there was always a tripewriter around, but somewhere back about when the first 4004 microprocessor was hitting the streets (1971?) I wrote an article for the national Ham Radio mag titled "White Stones With Gold Legs", and later did a presentation to a large Ham radio club.



These guys were wetting themselves about a device called a UART ("you-art").  This is a computer system building block that manages serial RS-232 (pre-USB) communication to the outside world, such as a user terminal (screen+keyboard) or printer.

There was a whole Ham/tech community that was fixated on a single small ordinary Leggo brick, the UART, and ignoring the box full of system bits, the RAM, ROM, CTC's, IRQ's, DMA, but mainly the central engine of the whole works, the CPU, the "microprocessor".  They were missing the whole point!  This was a paradigm shift from wired logic systems to stored programme logic systems, and a lot was going to change for techs as a result.

And while writing this stuff on a MicroBee (to cassette storage, then CP-80 dot matrix printer), I had an epifin... upif... a sudden realisation that typing was going to be an important future skill for any technician.  So I got quick.

Since then I've completed more than twenty major software projects, where "major" means more than about 10k lines of code, which can mean months of coding and testing, all keyboard work.


I once had the privilege of playing a 1930's Gibson acoustic guitar.  It didn't look like much, dull finish, but when you picked it up it almost played itself, it tempted you to do things you wouldn't dream of attempting on your own guitar, and when you fluffed it you were forgiven.


Well by far the best QWERTY keyboard I've used was on a NEC APC-III, sat nicely on the lap, and dished perfectly for speed.


I've just had a very nice weekend houseminding a lovely little dog, a heated jacuzzi, and a Yamaha upright piano.  Now my Yammy DX-7 keyboard is plastic with no "feel", but it's solid and tolerable.  I have a couple of others that are worse, "plasticy".

So feeling the hammers under my fingers, the mechanism and linkage, not only fairly tight, but not really "played in" yet (with only kiddy practice), gave a feedback that caused me to go right off for a couple of hours extemporising.  Been a looong time.   <3)


...ahem ... yeah, well anyway ... movin' right along ...
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

Quote from: Roly on March 19, 2015, 09:16:45 PM
There was a time when I had a rather large paddock next to my workshop at my disposal.   ;)
Well, I was a little confused by your comment, so I asked Mr Google:
https://www.google.com.ar/search?client=firefox-a&hs=9ah&rls=org.mozilla%3Aen-US%3Aofficial&channel=rcs&biw=1024&bih=516&tbm=isch&sa=1&q=paddock&oq=paddock&gs_l=img.12...0.0.0.509444.0.0.0.0.0.0.0.0..0.0.msedr...0...1c..62.img..0.0.0.5fGHgiqvhAE
as you see, I searched for images related to the word *paddock* , no extra qualifications.

And what images did Mr Google show?
(check for yourself):









also you said you quit smoking, but Mr Google suggests:



of course I know you are an Ozzie and not a Kiwi, because in that case they suggested:






Roly

"Paddock" = the log dump of a shut-down sawmill.
-31.630487, 152.297325

If I'd had any of those in my paddock I would have been somewhat distracted from my mission.

doc: Do you smoke after sex?
blond: I don't know, I've never looked.

{Of course none of the above has anything to do with the gratuitous use of young women's' bodies to sell products.  Related to almost nothing, did you know that the advertising of tobacco products has been banned here for some years, they can only be sold from plain cabinets, and now have to be sold in "plain" packaging which is actually covered in health warnings and lurid pictures of sick peoples plumbing?  Smokers are now only 20% of the population and falling.}

Actually, I'm more into goats than sheep, just more interesting generally, good sense of humour, better conversationalists...




...I should get into town more often.   ::)
If you say theory and practice don't agree you haven't applied enough theory.