 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
154.47.28.108
In Reply to: RE: $1,000 and even a $1200 Dollar 1.4 and 2" Compression Driver posted by B. Scarpia on May 06, 2023 at 08:55:35
Hi
I have measured both and use the B&C in a couple products at work which replaced the BMS coax driver (the originator of that design) .
The Celestion has a "good story", the B&C has en extended hf response and reaches 20K easily and the "off the shelf" crossover works much better than the BMS coax and stock crossover. These work well in CD horns which have a larger listening area, where the highs need to cover more seats. On a large enough horn, a high pass in the 300-500Hz range is easily accomplished. I use these where there isn't enough room for mid range cone horn drivers on Synergy horns.
The Celestion would be much more suited to a exponential (curved wall) style horns who's patterns get narrow up high, which can partially offsets the drivers acoustic power hf roll-off on axis and make a flatter on axis response albeit over a smaller area.
The pattern loss frequency can be estimated with Don Keele's thumb rule.
Pattern loss F=~ 10^6 / horn mouth angle / horn mouth width inches.
Tom
Follow Ups:
I assume that on these type of units, only the midrange can utilize different horn geometries and hi freq driver is single geometry?
Or can a different hi freq horn be attached to this drivet also ?
Hope that makes sense
Umm good question. The BMS coax driver has the hf section too far away in time to make a non-dsp crossover that acts like a single source. The B&C is different and doesn't have that issue, it acts like a synergy horn inside.
On the other hand the horn does two main things so far as this conversation, the horn increases the driver efficiency and increases the system's directivity and BOTH increase the SPL on axis for a given power..
The impedance transformation part has a "high pass" effect set by the rate the cross sectional area expands. For example, if one wanted a 30Hz bass horn, the exponential expansion dictates the area double no faster that about every 2 feet. A 60Hz horn would double every one foot and so on all the way up in frequency. For this part of a horns performance, the impedance transformation doesn't go on for ever, it stops when the horn is 1 WL in circumference. For a 30Hz horn in free space, that comes out to be about a 10 foot diameter. No need to make it bigger, no acoustic gain anyway...but.
The directivity but first consider the 1 inch exit hf driver and the rule above. At 20KHz, the wl is 5/8 inch and so ALL of the impedance transformation is done well before the sound reaches the driver exit and that inside the horn is a passage that continues the horn shape getting smaller as it gets to the radiator.
So this doesn't mean the horns job is done, no, the part of the horn past the end of the impedance transformation continues to direct the sound.
If you imagine a conical horn with the driver at the apex, what radiates away from the driver is a part of a spherical wavefront who's pressure front is perpendicular to the horn walls. As one goes down in frequency, the point where the horn no longer controls the radiation angle can be found / measured. Don Keele's thumb rule is quite good.
If one had a conical horn who's mouth was 10 inches and was a 60 degree angle, then pattern loss F is 10^6 / 60 degrees /10 inches = 1666Hz
Because the pattern control is the horn wall above that F, above that the radiation angle continues to be 60 degrees.
Well all the up to the where the throat dimension takes over pattern control. A 1 inch exit hf driver sitting face up with no horn, has an exit large enough to control the pattern up high.
That formula rearranged is pattern angle given the diameter and frequency
10^6 / diameter 1 inch / 20Khz = ~ 50 degrees so 10KHz = 100 degrees.
So, this was the long way to get to the point that your driver exit size also controls how wide a CD horn it can drive how high without diffraction inside the horn.
The older type horns (curved walled horns like exponential) are very useful where one has a smaller seating area.
The same pattern loss rules apply but now starting down low, as you go up in frequency, the part of the horn that controls pattern moved up the horn and because the horn walls angle is decreasing, the radiation angle also gets narrower and narrower. This changing directivity used to used to off set the naturally falling acoustic power from the hf driver, making if flat or near flat on axis where if mounted on a CD horn with a constant angle vs frequency it would show a typical 6dB/oct roll off of the real acoustic power.
Well a longer answer than i intended, hope it makes sense
Tom
I really appreciate the level of info you provide, takes some time to absorb.
Need to look up what range the B&C high freq ring radiator portion of coax is designed for (and xover) to more fully grasp what the integrated horn is influencing ( efficiency vs directivity ) over its range.
They have a crossover that does a good job, then you have 1 very wide bandwidth driver so far as the exit.
B&C has one perfect for that driver
https://www.bcspeakers.com/en/products/horn/1-4/0/ME464
At about $3200 a pair a person could spend a lot more for less. With active crossover to the woofer it's practically turnkey, Keeps all of the devices within 1/2 wavelength with a 15" woofer.
did you mean to say $1200 and not $3200 per pair?
Yes and the not obvious part is that particular combination can comfortably go frightfully loud. Since most everything loudspeakers do wrong or adds to the signal, increases faster with input level than the desired sound does.
The phrase "headroom is your friend" comes in to play very powerfully here. The loudest it would ever play in a living room is idling or lower.
Tom
How that horn would work with one of the Faital 1.4s?Here's what I get with the 140\142 combo. good for 600hz for low power use. Still close to 1/2 wavelength woofer interaction. The only aspect I don't like is the 60 degree horn and that's only my room interaction. Other rooms 60 degrees may be perfect.
RCF has some nice smaller, cheaper horns but won't make it to 300hz.
Edits: 05/08/23 05/08/23 05/08/23
"How that horn would work with one of the Faital 1.4s?"
It's polar pattern would be the same, the frequency response would likely be a little different. This horn is longer and will load the driver to a lower frequency than the 142 and it's larger size means it holds the pattern to a lower frequency.
Horns can give you a large "near field" where the direct sound is substantially louder than the late room sound. not only is there much less sound going to the rear but less to the sides too.
Position, imagine those horns one on each side with a little light where the driver (exit slot in this case) is.
Now imagine mirrors on your walls. You can move the speakers closer to your side walls than normal.. as long as the horn is toed in and you can't see the light bulb in the mirror on the side wall at the listening position. Your avoiding a side wall reflection where the horn has pattern control.
No driver has a flat power response so some EQ is normal and proper EQ corrects mag and phase at the same time.
Crystal clear worth more than an afternoon!
Rafaro
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
