front vs center channel speaker sensitivity

GranteedEV

GranteedEV

Audioholic Ninja
what about someting like a Summa? Shouldn't that be a good center channel because of its dispersion characteristics?
 
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TLS Guy

TLS Guy

Seriously, I have no life.
what about someting like a Summa? Shouldn't that be a good center channel because of its dispersion characteristics?
I think for a good center you need to avoid crossing over spaced drivers in te speech discrimination band.
 
T

Theresa

Junior Audioholic
Huh? While different manufacturers may measure differently, the reported sensitivity of a speaker is far from marketing hype.
I cannot believe that almost all speakers have a sensitivity of 90db with 2.83 volts at one meter or for efficiency 90db at 1watt at one meter. This is especially true if they have baffle step compensation which lowers the sensitivity/efficiency by 4 to 6 db. Another factor is that I have looked at a lot of driver specs and their sensitivity varies widely mostly quite a bit under 90db. I think more expensive speaker systems tend to be more accurate in this but companies such as Polk advertise all of their speakers as having 90db efficiency/sensitivity. People look at the 90db rating and if they see one that is more accurately rated at 85db they will choose the 90 as it is supposed to be "louder." But then again, I've been wrong many times before, I can be wrong again. It really is of no consequence to me as I build my own.
 
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TLS Guy

TLS Guy

Seriously, I have no life.
I cannot believe that almost all speakers have a sensitivity of 90db with 2.83 volts at one meter or for efficiency 90db at 1watt at one meter. This is especially true if they have baffle step compensation which lowers the sensitivity/efficiency by 4 to 6 db. Another factor is that I have looked at a lot of driver specs and their sensitivity varies widely usually quite a bit mostly quite a bit under 90db. I think more expensive speaker systems tend to be more accurate in this but companies such as Polk advertise all of their speakers as having 90db efficiency/sensitivity. People look at the 90db rating and if they see one that is more accurately rated at 85db they will choose the 90 as it is supposed to be "louder." But then again, I've been wrong many times before, I can be wrong again. It really is of no consequence to me as I build my own.
It would not surprise me if the manufacturers lie. They fabricate lots of things.

It is true that most 5 to 7 inch drivers have sensitivities in the 89 db range. By the time you add crossover losses and step loss compensation it would probably put most bookshelves in the 84 db range. However if two woofers are used that would put the sensitivity back around 89 to 90 db.

What speakers have you built? We have quite a few sub builders here, but I think I'm one of the few total speaker system builders here.

Do you have some pictures?
 
Z

zumbo

Audioholic Spartan
It is true that most 5 to 7 inch drivers have sensitivities in the 89 db range. By the time you add crossover losses and step loss compensation it would probably put most bookshelves in the 84 db range. However if two woofers are used that would put the sensitivity back around 89 to 90 db.
Very, very interesting. Had to go look.:D

German Maestro bookshelf(2-way): 85dB

German Maestro floorstander(2.5-way): 89dB
 
J

Jacksmyname

Audioholic
I have the Energy RC-70's for mains, and the RC-LCR center.
Side and rear surrounds are Mirage Omnican 6 in-ceilings.
Subs are a Mirage Omni S10 stacked on a Mirage Omni S12.
The 70's are rated @92 (anechoic) and 95 (2 speakers in a typical room).
The LCR is rated @89 (anechoic).
These numbers are from Energy's web site.
My receiver (Yamaha RX-V3800) set the LCR at +3.5 above the mains during auto-setup.
System rocks. :)
 
T

Theresa

Junior Audioholic
no sense not actively crossing over center

To me, the center, if you have one, will benefit from an active crossover just as much as the L/Rs. It carries most of the dialog. I actively crossover all my fronts and it sound wonderful. As a previous poster mentioned, placement can be a problem. I have my center above my screen, more than a foot and a half higher than the other fronts. I've tweaked it so it sounds almost identical to the LRs and they use different drivers from different manufacturers!
 
J

jostenmeat

Audioholic Spartan
To me, the center, if you have one, will benefit from an active crossover just as much as the L/Rs.
Theresa, I am just starting to educate myself about DIY speakers, and while a build wouldn't happen for a while (if ever), I'd like to learn more about active implementations. Do you have any resources or sites to recommend in finding out more? Thanks.
 
lsiberian

lsiberian

Audioholic Overlord
Theresa, I am just starting to educate myself about DIY speakers, and while a build wouldn't happen for a while (if ever), I'd like to learn more about active implementations. Do you have any resources or sites to recommend in finding out more? Thanks.
I have gone back and forth between active and passive proposals myself. It is not an easy choice and passive crossovers are currently a budget creation because we lack good modular amplifiers to implement active ones. Though there are some out there currently.
 
J

jostenmeat

Audioholic Spartan
Thanks, particularly for the first link.

I have gone back and forth between active and passive proposals myself. It is not an easy choice and passive crossovers are currently a budget creation because we lack good modular amplifiers to implement active ones. Though there are some out there currently.
I don't know what the true definition of a modular amp is, but I don't really feel the need to install amplifiers into or on the back of the speaker itself, if that's what you're implying. I could see perhaps installing an amp for each tweeter (only due to the number of amp channels I currently have in possession). However, mch amps aren't so terribly expensive, and I rather send long runs of speaker wire than interconnects. Well, I suppose if I had access to balanced XLRs . . . but I don't.

I just recently received and started reading a speaker building book by Alden (recommended by Swerd), and next time I pick it up, I'll see if there is an active section I could beeline to for the moment.

Thanks guys.
 
TLS Guy

TLS Guy

Seriously, I have no life.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-300

is a modular amp. It is supposed to be quite nice, but I need a reliable 3 channel one. Mounted with a power supply I could make my speakers independent.

I will probably give it a go at some point.
Those units were tested and reported in Audio x-press a couple of years ago, before they were easily obtainable here. They came up a little short of the mark, but having said that good value for money.
 
J

jostenmeat

Audioholic Spartan
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-300

is a modular amp. It is supposed to be quite nice, but I need a reliable 3 channel one. Mounted with a power supply I could make my speakers independent.

I will probably give it a go at some point.
Those units were tested and reported in Audio x-press a couple of years ago, before they were easily obtainable here. They came up a little short of the mark, but having said that good value for money.
Now that is cheap!

Hm. Now, D class amps are best suited to bass drivers, correct? I know 50w would be plenty for say a tweeter, but for a bass driver? I suppose this amp is designed for a 2way bookshelf ideally? Hm. *scratches head*
 
GranteedEV

GranteedEV

Audioholic Ninja
Now that is cheap!

Hm. Now, D class amps are best suited to bass drivers, correct? I know 50w would be plenty for say a tweeter, but for a bass driver? I suppose this amp is designed for a 2way bookshelf ideally? Hm. *scratches head*
I don't know a thing about tripath stuff but I do know hypex ucd and B&O icepower are both perfectly fine with high frequencies.
 
GranteedEV

GranteedEV

Audioholic Ninja
I think for a good center you need to avoid crossing over spaced drivers in te speech discrimination band.
Interestingly, the crossover point seems very intentional

Geddes said:
I designed these systems arround the critical 1000 - 8000 Hz band where, if this band isn't right then the sound won't be right. This required NO crossovers in this band since crossovers - at best - don't work very well. Thus a crossover at 1 kHz is dictated. Its also important that the HF region be fairly narrow directivity to avoid the very early room reflections. Quickly you can see that the response at 1000 Hz is going to be narrow and that for the LF driver to match the waveguide at 1000 Hz it too has to have a narrow response. A little calculation will show that for a 90 degree pattern at 1 kHz one needs a LF driver no smaller than 12" and 15" is better.
 
Teetertotter?

Teetertotter?

Full Audioholic
My center channel was matched with the mains[ELAC], and recently went back to PSB Imagine XC. The PSB has better dialog clarity to MY ears, along with overall performance.
 
Teetertotter?

Teetertotter?

Full Audioholic
My center channel was matched with the mains[ELAC], and recently went back to PSB Imagine XC. The PSB has better dialog clarity to MY ears, along with overall performance.
RETRACTED, I went back to the ELAC Ctr channel, yesterday. All is better............
 
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