Just bought a pair of Max Pentivent 15" bass drivers. Qts 0,75, Fs 24Hz.
I will use these underneath my Goodmans 201's on an open "U" baffle.
What is the best way to break these in before mounting them? I've bolted them together facing each other on my bench and connected them to a 150W amp.. Do I drive them with white noise or a signal from my signal generator at Fs? I've read both opinions and I'm not clear. Also what volume should I use and for how long?
thanks
Kev
I will use these underneath my Goodmans 201's on an open "U" baffle.
What is the best way to break these in before mounting them? I've bolted them together facing each other on my bench and connected them to a 150W amp.. Do I drive them with white noise or a signal from my signal generator at Fs? I've read both opinions and I'm not clear. Also what volume should I use and for how long?
thanks
Kev
It was you put me on to Ian at Nightfire and he eventually persuaded me to give them a try? Nice bloke Ian and seems very knowledgable. He also sent me 2 pairs of tweeters on a sale or return basis but they're a bit pricey and if either don't really shine I'll probably go for the seas tweeter from Wilmslow audio.
I'll let you know in a week or 2.
Kev
I'll let you know in a week or 2.
Kev
i don´t think breaking in is really needed, but i´m not sure. it is said some surrounds need to move before they completely settle and get a constant stiffness.
A good way to run them in would be to place one unit on its magnet, and putting the other woofer on top of it, membranes face-to-face. Then connect one unit out of phase, and you won´t hear much.
A good way to run them in would be to place one unit on its magnet, and putting the other woofer on top of it, membranes face-to-face. Then connect one unit out of phase, and you won´t hear much.
If you are not measuring them to design a box for them, there is no need to break them in. Even if you wanted to measure them, there is little need to break them in for long periods.
Many experts say that a few seconds of exercise near xmax are all that is needed, DIYers will try to tell you that you need hours or days. Some claim to see large reductuions in Fs and increases in Vas, but I tend to question the measurement conditions. Fs and Vas can be very temperature dependant, and also signal level dependant.
Of the woofers I have measured, none have shown break in effects I would consider significant. One small 4" midwoofer pair I measured went from 85Hz to 77Hz Fs immediately after some exercise, then the next day the Fs was 85 again. My 12" woofers didn't change at all. Some measurement systems will spit out T/S parameters to 6 significant figures and make you think you are getting really accurate measurements. Well, I hate to say it, but T/S parameters are an approximation - frequently accurate to only ~5% or so.
Many experts say that a few seconds of exercise near xmax are all that is needed, DIYers will try to tell you that you need hours or days. Some claim to see large reductuions in Fs and increases in Vas, but I tend to question the measurement conditions. Fs and Vas can be very temperature dependant, and also signal level dependant.
Of the woofers I have measured, none have shown break in effects I would consider significant. One small 4" midwoofer pair I measured went from 85Hz to 77Hz Fs immediately after some exercise, then the next day the Fs was 85 again. My 12" woofers didn't change at all. Some measurement systems will spit out T/S parameters to 6 significant figures and make you think you are getting really accurate measurements. Well, I hate to say it, but T/S parameters are an approximation - frequently accurate to only ~5% or so.
I wouldn't rest them on their magnets to run them in for two reasons.
1. You will do a really good job of picking up any tiny metal (iron or steel) particles that are in the carpet or on the floor, some of which will be almost microscopic dust. This is unlikely to do any harm but why risk the chance of getting crap into the gap?
2. If your magnets have a vent hole in the rear, you shouldn't block it up as by doing so you will force the speaker to vent via the dust cap and where ever else it can.
In fact, when I was running my Vifa 8" drivers in (bolted vertically to a temporary jig well off the floor) before testing, using a signal generator set just a bit above Fs, I noticed a strange faint sound when using large excursions. I found that this was the air 'breathing' in and out of the vent going thought the magnet. It was not that loud that it would be heard out of the box, but if you put your cheek close to it there was a suprising amount of air bouncing in and out.
I too was a little uncertain if break in was necessary, but it made sense and so I gave them a good workout perhaps 10 - 20 hrs each just to make sure, before making my measurements. The change of parameters was pretty slight however.
1. You will do a really good job of picking up any tiny metal (iron or steel) particles that are in the carpet or on the floor, some of which will be almost microscopic dust. This is unlikely to do any harm but why risk the chance of getting crap into the gap?
2. If your magnets have a vent hole in the rear, you shouldn't block it up as by doing so you will force the speaker to vent via the dust cap and where ever else it can.
In fact, when I was running my Vifa 8" drivers in (bolted vertically to a temporary jig well off the floor) before testing, using a signal generator set just a bit above Fs, I noticed a strange faint sound when using large excursions. I found that this was the air 'breathing' in and out of the vent going thought the magnet. It was not that loud that it would be heard out of the box, but if you put your cheek close to it there was a suprising amount of air bouncing in and out.
I too was a little uncertain if break in was necessary, but it made sense and so I gave them a good workout perhaps 10 - 20 hrs each just to make sure, before making my measurements. The change of parameters was pretty slight however.
Ohms law is what matters here 
ie V = I x R
if you have 30V then I = V/R so I = 30/8 = 3.75A
P = IV so power = 30 x 3.75 = 112.5W
if you have 240V then I = 240/8 = 30A
p = 240 x 30 = 7200W = fried driver (not that your average 240V circuit can deliver 30A anyway but you get the picture.....
The impedance of the driver is what provides the current limiting based on the applied voltage
Tony.
ie V = I x R if you have 30V then I = V/R so I = 30/8 = 3.75A
P = IV so power = 30 x 3.75 = 112.5W
if you have 240V then I = 240/8 = 30A
p = 240 x 30 = 7200W = fried driver
(not that your average 240V circuit can deliver 30A anyway but you get the picture.....The impedance of the driver is what provides the current limiting based on the applied voltage
Tony.
Breaking in drivers have no significan impact on the design. If does effect sound though. However, there are two aspects of breaking in, the electrical break in, and the mechanical break in. Mechanical break in can be done just by exercising the drivers close to Xmax using a low frequency sine wave; electrical break in can be done using some of those test CDs that have a burn-in track.
Of course! I wasn't even thinking about step down xformers, just isolation units for some reason. Sigh....I'm losing it.
wintermute said:Ohms law is what matters here
if you have 30V then I = V/R so I = 30/8 = 3.75A
P = IV so power = 30 x 3.75 = 112.5W
if you have 240V then I = 240/8 = 30A
p = 240 x 30 = 7200W = fried driver
The impedance of the driver is what provides the current limiting based on the applied voltage
Tony.
1st impressions
Not at all what I expected. Completely and comprehensively exceeded my expectations. I've been missing serious bass for the last 20 years
Currently I'm using these on a lashup with the signal from the main amp OUTPUT, into my bass amps with "L" resisotrs for gain matching. Bass amps are a pair of old crimson 1100's I had in the attic. There is a 2nd order LP crossover using bits from my parts box, no eq, so altogether nowhere near optimised
and yet compulsive listening.
I have nothing to compare these to as I haven't heard a system with this level of bass before, so with your TL's your opinion may be different. There is good information in the bass, strings can be heard, drums can be felt and the impact of the drumstick can be clearly heard. Brass and orchestral strings now have a believable quality I hadn't realised was missing. There is no overhang with bass notes starting and stopping really crisply.
So far so good, now to get optimising them.
Kev
Nuuk said:
Yes, that's what I thought! He seems to genuinely want to help rather than just sell something! Standing by.
Not at all what I expected. Completely and comprehensively exceeded my expectations. I've been missing serious bass for the last 20 years
Currently I'm using these on a lashup with the signal from the main amp OUTPUT, into my bass amps with "L" resisotrs for gain matching. Bass amps are a pair of old crimson 1100's I had in the attic. There is a 2nd order LP crossover using bits from my parts box, no eq, so altogether nowhere near optimised
and yet compulsive listening.I have nothing to compare these to as I haven't heard a system with this level of bass before, so with your TL's your opinion may be different. There is good information in the bass, strings can be heard, drums can be felt and the impact of the drumstick can be clearly heard. Brass and orchestral strings now have a believable quality I hadn't realised was missing. There is no overhang with bass notes starting and stopping really crisply.
So far so good, now to get optimising them.
Kev
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.