60 Degree DIY Mid Hi - AKA PM60

Re: 60 Degree DIY Mid Hi

The B&C drivers are available in 16ohms. So I plan on getting them in that version and using the crossover to make it a simple 2way box that equates to 16ohm hf/vhf & 8ohm mids..
 
Re: 60 Degree DIY Mid Hi

If you have an amp to deliver around 1300w or more at 8 ohm then sure go for it. I would not call the box simple tho.. especially not with the recommended FIR filters
 
Re: 60 Degree DIY Mid Hi

Ok, what wattage do I want to supply the 4594 with? I am confused since they show 80w and 150w, yet if I use passive crossover, I am sending one amp supply to both the HF and VHF. And the b&c 12", what voltage limit should these be set at? I realize the posted numbers for these speakers should explain this to me, but when I built my Keystone subs, I learned to drop the voltage quite drastically to prevent blowing speakers with low sine waves of EDM music.
 
Re: 60 Degree DIY Mid Hi

If you play bass heavy edm, thermal power rating will probably be the limiting factor as you already pointed out.



The b&c 12" have a rms handling of 400, so if you limit them to 500w with music material(higher crest factor than sine wave) I think you are on the safe side. I could not find the minimum impedance figure for the 16 ohm but it's 6.2 ohm for the 8 ohm model, let's estimate 14,2 on the 16 ohm model.

14,2/2 (2 drivers in parallell)=7,1

84(volts)×84=7056

7056/7,1=993 Watts at Zmin

993/2 ~500w for each driver

Otoh I think the cabinet design has to be included in the total zmin measurement as it changes the parameters of the impedance IIRC.

I would limit to 80-84 ohms if I were in your situation (given the total box zmin won't differ to much from driver zmin and my estimation of the 16 ohm driver is right)

Can't help on the bms these different power figures confuse me.

I built keystones aswell! Will be interesting to hear your findings combining them with the diy.. my initial impression with the 18sw115-8 is very good
 
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Re: 60 Degree DIY Mid Hi

Ossian Ott said:
The b&c 12" have a rms handling of 400, so if you limit them to 500w with music material(higher crest factor than sine wave) I think you are on the safe side.
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Loudspeakers are not rated in sine wave "wattage". Shaped noise is the test source

Where you should limit is not just based on the voltage and impedance-but also what size amp is being used on the driver.

Different attack times and voltages should be used with different sized amps.

If you don't know anything else-I would go for a voltage equal to the continuous (incorrectly used RMS) rating with a attack time about equal to the period of the lowest freq that would be going though them.

Yes-I agree that these numbers can be moved around quite a bit-depending on a number of factors.

Part of it comes down to the question of "are you trying to be musical with the limiter or keep the drivers from tearing up?"

Those can often yield very different results/settings.

So this suggestion is simply a "starting point" and does NOT guarantee you will not tear up the drivers.
 
Re: 60 Degree DIY Mid Hi

I was under the impression rms value are tested/calculated from a 3 dB crest factor sine wave which is why I estimated the 500w rating with music signal. I agree these are merely rough starting points. Especially since I don't know the final Zmin with the driver/box combination.

The amp size I have not considered. I'm somewhat reluctant in using very strong amps and limit them to 20% of their capacity out of probably the reasons you state, I'm unsure how to power the drivers accordingly with that much juice on hand.
 
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Re: 60 Degree DIY Mid Hi

My mistake on the wording I used in my question. Instead of sine waves, I should have used crest factors. At this point, I am looking to supply the b&c 12's with 600 watts each, properly high and low passed. I still don't understand the BMS with the two different ratings and this is where I need the most help.
 
Re: 60 Degree DIY Mid Hi

Ossian Ott said:
I was under the impression rms value are tested/calculated from a 3 dB crest factor sine wave which is why I estimated the 500w rating with music signal. I agree these are merely rough starting points. Especially since I don't know the final Zmin with the driver/box combination.

The amp size I have not considered. I'm somewhat reluctant in using very strong amps and limit them to 20% of their capacity out of probably the reasons you state, I'm unsure how to power the drivers accordingly with that much juice on hand.
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Though, honestly, setting the limiters "ideally" is still fairly amplifier independent, if you assume some things about the signal you're sending through it.
 
Re: 60 Degree DIY Mid Hi

Ossian Ott said:
I was under the impression rms value are tested/calculated from a 3 dB crest factor sine wave which is why I estimated the 500w rating with music signal. I agree these are merely rough starting points. Especially since I don't know the final Zmin with the driver/box combination.

.
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If the drivers were rated with sine waves-they would be rated much lower. But a sine wave would only test the heating of the voice coils. Overexcursion is another problem with failures. The noise also stresses this.

The box/speaker is not a factor in the loudspeaker driver manufacturers specs. Those are tested in free space-since there is no way the manufacturer can possibly know what box a driver would be used in.

Some designs will have different ratings in different boxes. Some designs cool better than others.
 
Re: 60 Degree DIY Mid Hi

Jason Allen said:
My mistake on the wording I used in my question. Instead of sine waves, I should have used crest factors. At this point, I am looking to supply the b&c 12's with 600 watts each, properly high and low passed. I still don't understand the BMS with the two different ratings and this is where I need the most help.
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I always suggest that a real long term thermal limiter is set at 1/2 the AES power rating of the transducer. In this case, 200 W. A lot of users find that pretty hard to take, since they have an amplifier that can deliver 1-2KW and are pretty invested in the power handling of their woofer having something to do with its acoustic output. There's a connection, and in the short term you can put a lot more "power" in, but in the very long term you have to pretend you're powering a toaster, or a resistor... you just need to keep input below its thermal capacity. That's why these limiters have attack times in seconds, or even tens of seconds. Unfortunately we have decided to talk about loudspeaker power input in watts and then divorce that from any concept of wattage that a physicist or an electrician would understand. Actually an electrician would understand it just fine, if you look at the trip times for household circuit breakers. The wires in your walls can handle a certain amount of heat before they become a fire hazard, so your breakers are designed to limit them below that. A 12AWG wire can pass hundreds of amps for a few seconds before getting too hot, just like a 3" voice coil can pass thousands of watts for a few seconds. Long term, though, like half an hour long term, 1/2 AES is a limit that will keep your speaker from overheating.

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Re: 60 Degree DIY Mid Hi

Bennett , this is exactly what I was trying to ask in the first place . In the keystone thread it was mentioned limiting the B&C 18TBW100-4 to 50 volts. Which in my amateur sound life seemed like a head scratcher. The speaker is rated at 1200w rms and 2400w peak. It seemed I was leaving a lot on the table by only putting about 750 watts into this speaker . But when people like Art Welter said this is the way to run this speaker it's what I did. I know he knows far more than I ever will about speakers. This is where I am with this box. So I should run the 12NDL76's with a limit of about 200w each? And for the BMS, with the c8-8 crossover , limit this to 115w? Half the AES for both.
 
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Re: 60 Degree DIY Mid Hi

In the ideal situation you would have two limiters complement each other. One set to 98V (1200W) with a short attack and fast release to prevent the speaker in doing things beyond its mechanical capabilities (Xmax, Xvar). The other limiter should be set to 40V (200W) with a long attack and slow release in case the speakers becomes a ironing machine.
The first limiter will protect you when you mix a quiet band and somebody decides to slam the drums for a short while. The second limiter is there for DJ's who torture your system with minute-long sine-waves during breaks.
If you only have one limiter it depends on the usage; mixing bands at high SPL with people talking between songs? peak-limiter. DJ's with 12-hour continious music? slow limiter.
That's how I would do it.
 
Re: 60 Degree DIY Mid Hi

Jason Allen said:
Bennett , this is exactly what I was trying to ask in the first place . In the keystone thread it was mentioned limiting the B&C 18TBW100-4 to 50 volts. Which in my amateur sound life seemed like a head scratcher. The speaker is rated at 1200w rms and 2400w peak. It seemed I was leaving a lot on the table by only putting about 750 watts into this speaker . But when people like Art Welter said this is the way to run this speaker it's what I did. I know he knows far more than I ever will about speakers. This is where I am with this box. So I should run the 12NDL76's with a limit of about 200w each? And for the BMS, with the c8-8 crossover , limit this to 115w? Half the AES for both.
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As Bennett just suggested, I had told you to long term limit the B&C 18TBW100-4 to about half it's 1500 watt 6 dB crest factor A.E.S rating (don't know where you are getting 1200),"RMS" implies sine waves, a 3 dB crest factor, or 750 watts. The Keystone has a minimum impedance near the DCR of the speaker (3.2 ohms) at around 37 Hz (IIRC) so 50 volts results in about 781 watts at a frequency likely to contain heavy droning bass in EDM which may have as little as 3 dB crest factor. 750 watts at 3 dB crest factor is the equivalent average power of 1500 watts at 6 dB crest factor, or 3000 watts at 12 dB crest factor.

Long term limiting the BMS 4594 (or 4595) mid/high driver to 115 watts will not protect the mid driver rated for 150w AES (75 watts sine or "RMS") or the HF driver rated for 80 watts AES (40 watts sine or "RMS", just a bit over half the mid driver's rating).
That said, I have not (yet) heard reports of music with less than 6 dB crest factor in the HF (the crest factor of Metallica's latest recording...) , but if you work in hot, dry locations, the amount of HF boost required to compensate for HF air absorption (10 dB or more above 10kHz) could fry the HF diaphragm if set for more than 40 watts long term.

When using two differently rated drivers on one amp, the only way to protect both is using frequency dependent limiting.

Art
 
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Re: 60 Degree DIY Mid Hi

Art Welter said:
As Bennett just suggested, I had told you to long term limit the B&C 18TBW100-4 to about half it's 1500 watt 6 dB crest factor A.E.S rating (don't know where you are getting 1200),"RMS" implies sine waves, a 3 dB crest factor, or 750 watts. The Keystone has a minimum impedance near the DCR of the speaker (3.2 ohms) at around 37 Hz (IIRC) so 50 volts results in about 781 watts at a frequency likely to contain heavy droning bass in EDM which may have as little as 3 dB crest factor. 750 watts at 3 dB crest factor is the equivalent average power of 1500 watts at 6 dB crest factor, or 3000 watts at 12 dB crest factor.

Long term limiting the BMS 4594 (or 4595) mid/high driver to 115 watts will not protect the mid driver rated for 150w AES (75 watts sine or "RMS") or the HF driver rated for 80 watts AES (40 watts sine or "RMS", just a bit over half the mid driver's rating).
That said, I have not (yet) heard reports of music with less than 6 dB crest factor in the HF (the crest factor of Metallica's latest recording...) , but if you work in hot, dry locations, the amount of HF boost required to compensate for HF air absorption (10 dB or more above 10kHz) could fry the HF diaphragm if set for more than 40 watts long term.

When using two differently rated drivers on one amp, the only way to protect both is using frequency dependent limiting.

Art
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The AES measurement is an RMS measurement - http://diy-audio.narod.ru/litr/AES2-1984-r2003.pdf

As I understand some of the old RMS ratings / specifications were made at the minimum impedance which gave lower (RMS) power rating.
 
Re: 60 Degree DIY Mid Hi

Guys, I appreciate the advice and it's not falling on deaf ears. I am trying learn from you guys and sometimes it takes a few questions to understand . My main confusion with the 4594 was using the passive crossover and sending one amp signal to the 4594 and properly powering it. Since it states 150w and 80w. I could not understand the right way to supply both HF and MF with the proper power. I plan on using frequency limiters as you mentioned Art.
 
Re: 60 Degree DIY Mid Hi

Peter Morris said:
The AES measurement is an RMS measurement - http://diy-audio.narod.ru/litr/AES2-1984-r2003.pdf

As I understand some of the old RMS ratings / specifications were made at the minimum impedance which gave lower (RMS) power rating.
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The AES measurement we are talking about uses a peak-to-rms voltage ratio of 2:1, limiting the 12 dB crest factor pink noise to a 6 dB crest factor.
Back in the "olden days" (pre-1984), the "RMS watts" used to test speakers were sine waves (same as used for rating amplifiers) which have a crest factor of 3 dB.

I'm so old that if there is not a reference to AES I still assume a sine wave for "RMS" watts...
 
Re: 60 Degree DIY Mid Hi

Jelmer de Jong said:
In the ideal situation you would have two limiters complement each other. One set to 98V (1200W) with a short attack and fast release to prevent the speaker in doing things beyond its mechanical capabilities (Xmax, Xvar). The other limiter should be set to 40V (200W) with a long attack and slow release in case the speakers becomes a ironing machine.
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Screen Shot 2016-03-06 at 3.29.01 PM.pngIf you like. In a subwoofer attack and release times of 30 seconds or longer wouldn't be un-warranted, but that requires a lot of envelope tracking so the 5-10 seconds that most limiters allow gets the job done and sounds OK. I've attached a capture of the LSI power test data from one of our 18" woofers, as you can see it takes about 7 minutes for the coil to come to temperature - by which time it's about doubled in impedance (i.e. is now effectively 16Ω instead of 8Ω). This is with AES rated power input, which should be a long-term survivable power level if excursion is kept under control.

All that says nothing about mechanical constraints, these power tests are in free air. Add a cabinet and the limits of the woofer will not be the same. A basic thermal limiter will save your bacon in nearly all situations. Unfortunately, excursion cannot be limited with a simple peak limiter: your best bet is to use an appropriate high pass filter (e.g. 2nd order at the box tuning frequency for a normal direct radiator). In a reasonably designed box, between the thermal limiter and the high pass filter, it ought to be pretty difficult to exceed the capabilities of the woofer. More importantly, with such a system the first indication of distress will likely be given by the woofer so an experienced operator will know where the limit lies. Klippel have done some significant research recently into a method for reliably limiting excursion, primarily for small devices, but I have not yet seen a pro audio application of it. To my knowledge there is no widespread tool that will limit excursion directly.
 
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