Wharfedale have been making woofers with phase plugs for awhile now. Why?
I had a pair of Wharfedale Reva 4s a few years ago and the dedicated woofers had solid metal phase plugs (Not dust caps). It appears the new acclaimed EVO series speakers use the exact same drivers for the woofers as well. It seams to me to be highly flawed design. Did they just have a stock pile of these that were originally mid-range/woofers and they decided to use them up?
Is there any reason at all to use a phase plug on a dedicated woofer?
It always bothered me on the Revas. You technically get blow-by and/or chuffing from the air moving between the cone and the phase plug. PLUS, the phase plug represents a portion of surface area that could have been used to move more air had it been part of the cone. It is lost energy. No?
I had a pair of Wharfedale Reva 4s a few years ago and the dedicated woofers had solid metal phase plugs (Not dust caps). It appears the new acclaimed EVO series speakers use the exact same drivers for the woofers as well. It seams to me to be highly flawed design. Did they just have a stock pile of these that were originally mid-range/woofers and they decided to use them up?
Is there any reason at all to use a phase plug on a dedicated woofer?
It always bothered me on the Revas. You technically get blow-by and/or chuffing from the air moving between the cone and the phase plug. PLUS, the phase plug represents a portion of surface area that could have been used to move more air had it been part of the cone. It is lost energy. No?
Your query caught my attention because I have wondered about that for years, ever since seeing a woofer with a phase plug.
Before answering your query with a simple yes or no, let's look at some facts.
Since the Reva 4 uses two 6 inch woofers, (I had to google that) and the woofer is low pass filtered at 350hz, a wavelength of 39 inches. The effective piston area Sd of a 6 inch unit is about 18.4 in^2. Since it's safe to assume that the voice coil is about 1.5", we have a radiating area loss of 1.77 sq.in.
A piston ( loudspeaker diaphragm) radiating into 2 pi steradians (hemisphere) and mounted on a flat baffle of at least 23 ft on a side, if square or 23 ft in diameter if circular to prevent doublet action above 50hz, (cancellation of the pressure waves from the front and rear of the loudspeaker). Such a loudspeaker under the conditions described above would generate a pressure wave of 78.11dB. With the phase plug and reduced radiating area, this would drop to 77.234dB. a loss of 0.876dB, not worthy of concern.
Now, to answer your query as to the reason for the phase plug, I'd have to say cosmetics. As for the use of the same woofers in the EVO series, that's common practice especially given the physical similarity of the two systems regarding the bass section. A lot of product changes in style are touted as making improvements but analyses usually show that it's six of one and half a dozen of another. Consider automobiles. The difference between a Chevy and a Pontiac is mostly the name and a few style changes but the undercarriage is essentially the same. This is true for just about anything that is sold to consumers. It all has to do with the psychology of marketing.
I could go on ad nauseum on topics such as this but I'll show you mercy. Way back in the late seventies, Paul Klipsch said to me as he pinned a yellow 2 inch diameter disc which had one word printed on it onto my lapel, 'Ninety percent of what any audio dealer tells you is right here.' The word can be seen at the bottom of this page link so as not to violate any rules of this forum. THE EXPONENTIAL HORN - 1
Hope the above satisfies your query.
Robert
Before answering your query with a simple yes or no, let's look at some facts.
Since the Reva 4 uses two 6 inch woofers, (I had to google that) and the woofer is low pass filtered at 350hz, a wavelength of 39 inches. The effective piston area Sd of a 6 inch unit is about 18.4 in^2. Since it's safe to assume that the voice coil is about 1.5", we have a radiating area loss of 1.77 sq.in.
A piston ( loudspeaker diaphragm) radiating into 2 pi steradians (hemisphere) and mounted on a flat baffle of at least 23 ft on a side, if square or 23 ft in diameter if circular to prevent doublet action above 50hz, (cancellation of the pressure waves from the front and rear of the loudspeaker). Such a loudspeaker under the conditions described above would generate a pressure wave of 78.11dB. With the phase plug and reduced radiating area, this would drop to 77.234dB. a loss of 0.876dB, not worthy of concern.
Now, to answer your query as to the reason for the phase plug, I'd have to say cosmetics. As for the use of the same woofers in the EVO series, that's common practice especially given the physical similarity of the two systems regarding the bass section. A lot of product changes in style are touted as making improvements but analyses usually show that it's six of one and half a dozen of another. Consider automobiles. The difference between a Chevy and a Pontiac is mostly the name and a few style changes but the undercarriage is essentially the same. This is true for just about anything that is sold to consumers. It all has to do with the psychology of marketing.
I could go on ad nauseum on topics such as this but I'll show you mercy. Way back in the late seventies, Paul Klipsch said to me as he pinned a yellow 2 inch diameter disc which had one word printed on it onto my lapel, 'Ninety percent of what any audio dealer tells you is right here.' The word can be seen at the bottom of this page link so as not to violate any rules of this forum. THE EXPONENTIAL HORN - 1
Hope the above satisfies your query.
Robert
could be cosmetic but i'd venture it's more about thermal characteristics, a woofer that is able to vent to the outside should in effect aid in reducing "power compression" and adding mass to the magnet the same.
i remember the EV "Heat Wick" series of pro driver where some of the first drivers designed to address that problem.
only problem with no dust cap is dirt can get in there....
i remember the EV "Heat Wick" series of pro driver where some of the first drivers designed to address that problem.
only problem with no dust cap is dirt can get in there....
Last edited:
Important update:
Wharfedale have CHANGED the woofers they are using in the EVO series. They are now using faux phase plugs (Just dust caps) instead of real phase plugs. I assume the change was to save money. I just bought a pair to test out and they are indeed just dust caps, not solid metal phase plugs. I think this was a wise choice on their part, even if it was just to save money.
Wharfedale have CHANGED the woofers they are using in the EVO series. They are now using faux phase plugs (Just dust caps) instead of real phase plugs. I assume the change was to save money. I just bought a pair to test out and they are indeed just dust caps, not solid metal phase plugs. I think this was a wise choice on their part, even if it was just to save money.