Dayton UM 18-22 clipping issue with sealed cabs and crown amps.

[TLS Guy]

Would adding more power in the form of another amp solve the clipping issue? Thanks for your time.

Yes, but probably blow up the drivers instead.

 

[lovinthehd]

Which miniDSP 2x4 unit do you have?

Appropriate output voltage set? You're just hitting clipping and/or thermal compression indicators? Gain on amps set where and how?

 

[TLS Guy]

Would adding more power in the form of another amp solve the clipping issue? Thanks for your time.

I'm going to amplify my remarks on this as it goes to the heart of the issue of power band response. As I have said so often it is not just a matter of how low it will go, but but how loud it will go that low.

Lets take a look at your driver. This is it FR in an optimal sealed enclosure.

So you see that the possible output at 18 Hz which you are trying to reproduce is a whole 10 db lower than the output above the F3 of 31 Hz.

Now lets take a look at power handling versus frequency.

So because of mechanical limits power that the driver will tolerate decreases with frequency and yet you need to apply boost to maintain a flat response below F3.

Now lets take a look at cone displacement.

You will not that cone displacement can not be increased below 25 Hz.

The bottom line is that in order to keep a flat response the power above boost has to be decreased. So adding power will do nothing except further deplete your bank account.

The bottom line is that this sub used conservatively will produce a very decent high quality bass under reasonable domestic conditions with a small foot print.

This is not a sub for high db at or below the last octave.

For what I think you are aiming for this is the sub you need to build. This one will produce close to 120 db 1 watt 1 meter with no boost. Members who have built this sub have been ecstatic about it.

That sub will produce the same acoustic output as your sub at 18 Hz with less than 100 watts drive.

So the solution to your clipping problem is a sub that can transform the pressure generated behind the cone into moving air much more efficiently. However the penalty is a much bigger box. That darn Hoffman's Iron Law again!

 

[NorCalRP]

To much attention is paid to solely how low will it go. The other side of the coin is how loud will it go at that frequency. At 25 Hz those drivers become limited in power output to 100 db 1 meter. If you have 2 of them then 103 db and 3 db for each one you have. Domestically for most that is pretty good. If you are a real "bass head" though probably not enough. Also people tend to set their subs far too loud in my opinion. That sort of sonic imbalance seems far too prevalent.

The other issue is that those drivers below 25 do not increase their power output with increased drive due to mechanical limitations.

If it were not for size factor no one would ever stuff a woofer in a sealed box. Basically it is a terrible idea and extremely crude.

At low frequencies a loudspeaker cone is horribly inefficient. I know generating sound is all about moving air, but a speaker cone does not move a lot of air. It takes pressure to move air.

That is where the concept of using an acoustic transformer comes in. The analogy is identical to an electric circuit. Voltage cause current to flow, the higher the voltage the high the current and the greater the power. Pressure is equivalent to voltage. Air movement equivalent to current. So we need pressure variation to move air.

That is what ported enclosures, pipes and horns do. The provide high pressure to the back of the cone. Much higher in fact than the restoring force of a sealed box. On top of that the rear radiation from the cone is totally adsorbed in the box and therefore wasted..

So good enclosures harness the power from the rear of the cone where there is very high pressure. This pressure then generates highly significant air displacement from the port, pipe or horn mouth. Of these the horn is by far the most efficient and the pipe close behind. A pipe closed at one end is the easiest to understand.

In a pipe where there is maximal pressure there in no air movement. Where there is no pressure there is maximal air movement. So at the closed end there can not be air movement only pressure change. The pressure is high, and therefore ideal for limiting cone movement and controlling it. At the open end these high pressures generated at the closed end result in large air movements from the open end.

In the ported enclosure the pressures are high and we have to make sure that the port has sufficient cross sectional area to not generate turbulence and noise. (chuffing).

A horn in front of the horn throat generates enormous pressure for high output at the horn mouth.

To cut to the bottom line, you never select a sealed solution for a sub if you have room for a bigger box. If it were not for the size issue we would not be talking about closed boxes ever.

So yes, my advice to you is to not go for a sealed solution if you have the space for something better.

The notion that sealed designs are inherently more musical is arrant nonsense.

Good points and thanks for the response. I like your power analogy. It made me thing back to my electrical theory classes in line school. I like that you use the word pressure as voltage is a measure of electromotive force, also called electromagnetic pressure.

Space is a concern for me. I was contemplating going to four PC-2000's. The idea of building and learning is very attractive to me.

Am I following that having 4 Ultimaxes would result in an output around 109dB at 20hz? I do personally feel that 100dB is a lot of output. What are your thoughts about Geddes' preference for sealed boxes?

 

[TLS Guy]

Good points and thanks for the response. I like your power analogy. It made me thing back to my electrical theory classes in line school. I like that you use the word pressure as voltage is a measure of electromotive force, also called electromagnetic pressure.

Space is a concern for me. I was contemplating going to four PC-2000's. The idea of building and learning is very attractive to me.

Am I following that having 4 Ultimaxes would result in an output around 109dB at 20hz? I do personally feel that 100dB is a lot of output. What are your thoughts about Geddes' preference for sealed boxes?

You are correct about everything you say. I would however use a 12 db per octave high pass filter at 25 Hz. What the graphs I posted illustrate among other things, is that those drivers hit the wall at 25 Hz and flogging them below that point does not make sense. So in any event they can not truly respond to the boost below that point.

As you say for sane domestic and properly balanced listening that is plenty of output. As I pointed out previously room gain will get you the rest of the way.

Good trouble free high quality listening is all about properly balancing trade offs by making the appropriate careful design choices for your situation

The wrong approach is to get hung up on a single parameter like for instance flat to 18 Hz. You really do want to invest in modelling and see what you results are likely to be in their totality.

I have come to realize recently that a lot of readers problems, and I suspect some professional designers do not pay enough attention to the power band response in different frequency bands. I have always had an eye for that even from my earliest years. To me it has been important to look at the power band requirements of the programs you are planing to enjoy and reproduce. Considering frequency response without coupling to an eye for power band responses in practice does not count for much. That probably contributes to people saying my designs have lots of ooomph.

Lastly there is a lot I disagree with Geddes about and a preference of sealed is just one of them.

 

[moves]

Appropriate output voltage set? You're just hitting clipping and/or thermal compression indicators? Gain on amps set where and how?

Yes it is set to .775 Vrms .. I think it is clipping... the red lights are flashing once in a blue moon on big scenes. Gain on the amp it turned to around 2 o'clock. I turned it with my hand haha.... not sure what you mean by how.

 

[moves]

I'm going to amplify my remarks on this as it goes to the heart of the issue of power band response. As I have said so often it is not just a matter of how low it will go, but but how loud it will go that low.

Lets take a look at your driver. This is it FR in an optimal sealed enclosure.




View attachment 30937

So you see that the possible output at 18 Hz which you are trying to reproduce is a whole 10 db lower than the output above the F3 of 31 Hz.

Now lets take a look at power handling versus frequency.

View attachment 30938

So because of mechanical limits power that the driver will tolerate decreases with frequency and yet you need to apply boost to maintain a flat response below F3.

Now lets take a look at cone displacement.




View attachment 30939

You will not that cone displacement can not be increased below 25 Hz.

The bottom line is that in order to keep a flat response the power above boost has to be decreased. So adding power will do nothing except further deplete your bank account.

The bottom line is that this sub used conservatively will produce a very decent high quality bass under reasonable domestic conditions with a small foot print.

This is not a sub for high db at or below the last octave.

For what I think you are aiming for this is the sub you need to build. This one will produce close to 120 db 1 watt 1 meter with no boost. Members who have built this sub have been ecstatic about it.

That sub will produce the same acoustic output as your sub at 18 Hz with less than 100 watts drive.

So the solution to your clipping problem is a sub that can transform the pressure generated behind the cone into moving air much more efficiently. However the penalty is a much bigger box. That darn Hoffman's Iron Law again!

Damn Hoffman..... I will try the 25hz high pass filter and see if I notice a difference.. I might not. I'll also check the scenes on some movies where the amps went into the red. Just wondering though.... if this driver isn't meant to put out a ton of bass, then why does Seaton use it in his box? If I am not mistaken, he also uses a 4000 watt amp with it. I think you can even by the amps separately with the F18 settings configured. Next time I build a sub, if ever, I will try the other design. If I do the 460HO, would my XLS 1502 do the job with the 460HO sub? If I can reuse the amps... then it wouldn't be that much of a hit to the bank account.

 

[Irvrobinson]

Yes it is set to .775 Vrms .. I think it is clipping... the red lights are flashing once in a blue moon on big scenes. Gain on the amp it turned to around 2 o'clock. I turned it with my hand haha.... not sure what you mean by how.

Just a few questions, out of curiosity, and I didn't see the information in the thread. Are you running the 1502s in bridged mode? Or is one 1502 channel connected to each 2 ohm voice coil? How are the amps cabled in the audio chain per channel after the DSP?

 

[lovinthehd]

Yes it is set to .775 Vrms .. I think it is clipping... the red lights are flashing once in a blue moon on big scenes. Gain on the amp it turned to around 2 o'clock. I turned it with my hand haha.... not sure what you mean by how.

Why is it set to that sensitivity setting particularly? Both red lights? Why did you choose the particular sensitivity setting as well as the gain/attenuation setting? What is the pre-out level involved? (I somewhat recall past conversations but since you've started a new thread....)

 

[TLS Guy]

Damn Hoffman..... I will try the 25hz high pass filter and see if I notice a difference.. I might not. I'll also check the scenes on some movies where the amps went into the red. Just wondering though.... if this driver isn't meant to put out a ton of bass, then why does Seaton use it in his box? If I am not mistaken, he also uses a 4000 watt amp with it. I think you can even by the amps separately with the F18 settings configured. Next time I build a sub, if ever, I will try the other design. If I do the 460HO, would my XLS 1502 do the job with the 460HO sub? If I can reuse the amps... then it wouldn't be that much of a hit to the bank account.

Yes your XLS1502 would have plenty of power to drive a couple 460HO drivers in a couple of the boxes I sighted in my link. Driving 2 of those subs you would get at least 118 db at 20 Hz, which is enough to damage your house. If you look at the graphs, you would see that the drivers would do this with under 6 mm cone excursion, because of the pressure controlling the cone. You could the forget all about DSP and transforms to 18 Hz. Just connect the amp to the subs and blow out your walls. With physics on your side life becomes simple.

 

[lovinthehd]

I'm going to amplify my remarks on this as it goes to the heart of the issue of power band response. As I have said so often it is not just a matter of how low it will go, but but how loud it will go that low.

Lets take a look at your driver. This is it FR in an optimal sealed enclosure.




View attachment 30937

So you see that the possible output at 18 Hz which you are trying to reproduce is a whole 10 db lower than the output above the F3 of 31 Hz.

Now lets take a look at power handling versus frequency.

View attachment 30938

So because of mechanical limits power that the driver will tolerate decreases with frequency and yet you need to apply boost to maintain a flat response below F3.

Now lets take a look at cone displacement.




View attachment 30939

You will not that cone displacement can not be increased below 25 Hz.

The bottom line is that in order to keep a flat response the power above boost has to be decreased. So adding power will do nothing except further deplete your bank account.

The bottom line is that this sub used conservatively will produce a very decent high quality bass under reasonable domestic conditions with a small foot print.

This is not a sub for high db at or below the last octave.

For what I think you are aiming for this is the sub you need to build. This one will produce close to 120 db 1 watt 1 meter with no boost. Members who have built this sub have been ecstatic about it.

That sub will produce the same acoustic output as your sub at 18 Hz with less than 100 watts drive.

So the solution to your clipping problem is a sub that can transform the pressure generated behind the cone into moving air much more efficiently. However the penalty is a much bigger box. That darn Hoffman's Iron Law again!

The OP has the UM-15 or 18?

 

[TLS Guy]

The OP has the UM-15 or 18?

Well spotted I clicked on the wrong file. However the results are similar. The units seem to have the same motor system. You have 1000 watts power handling. That and the larger cone give you another 3db. The curve flattens at 20 Hz rather then 25. So the OP could double his amp power. However the ported design I linked has a significantly higher output for much less power and no Eq. The Ultimax drivers can be ported but Qts is really too high and they really are optimized for a sealed alignment.

So the bottom line is that they make a very decent sub but like all sealed designs are power hungry and output limited by mechanical constraints compared to ported pipe or horn approaches.

 

[moves]

Just a few questions, out of curiosity, and I didn't see the information in the thread. Are you running the 1502s in bridged mode? Or is one 1502 channel connected to each 2 ohm voice coil? How are the amps cabled in the audio chain per channel after the DSP?

Hello - each channel is connected to a 2ohm coil. Channel 1 goes to one coil and channel 2 goes to another coil.

 

[moves]

Well spotted I clicked on the wrong file. However the results are similar. The units seem to have the same motor system. You have 1000 watts power handling. That and the larger cone give you another 3db. The curve flattens at 20 Hz rather then 25. So the OP could double his amp power. However the ported design I linked has a significantly higher output for much less power and no Eq. The Ultimax drivers can be ported but Qts is really too high and they really are optimized for a sealed alignment.

So the bottom line is that they make a very decent sub but like all sealed designs are power hungry and output limited by mechanical constraints compared to ported pipe or horn approaches.

Yes I have the 18.... So I should set the highpass at 20 and not 25 Hz?

 

[moves]

Why is it set to that sensitivity setting particularly? Both red lights? Why did you choose the particular sensitivity setting as well as the gain/attenuation setting? What is the pre-out level involved? (I somewhat recall past conversations but since you've started a new thread....)

I choose the .775 after talking with crown and them suggesting to use this setting to have Max power potential from the amp. I chose the gain by what sounds good to my ear. Not sure what you mean by what preout level involved? Yes both lights.

 

[Irvrobinson]

Hello - each channel is connected to a 2ohm coil. Channel 1 goes to one coil and channel 2 goes to another coil.

That's how I would do it, considering the design of the amp. I'm still puzzled by the clipping lights though. What are the dimensions of your room (LxWxH)? Have you measured the sound level at your listening seat when the clipping occurs? (If you don't have a sound level meter, there are inexpensive phone apps that will do for this type of problem.)

 

[TLS Guy]

I choose the .775 after talking with crown and them suggesting to use this setting to have Max power potential from the amp. I chose the gain by what sounds good to my ear. Not sure what you mean by what preout level involved? Yes both lights.

So that is a total of 1550 watts to a 1000 watt driver. It is excessive boost that is your problem. With those numbers you are past the point of diminishing returns. I think more will actually be less. That way you will free up more power where there is more meaningful program and the speaker is more sensitive. If you look at the power curves you can see sensitivity falling by 12 db per octave below 32 Hz. So that means it takes 10 times the amp power to produce the same acoustic output at 22 Hz than 32 Hz. So your whole bass program will sound better and cleaner by freeing up more power to the power bands where there is more program and actually more important program.

My last thought is that with all that power you might have damaged that driver already. I think you would be well advised to check the DC resistance of both voice coils and make sure they are in spec. If the DC resistance if either voice coil is below spec then you have a damaged voice coil or coils from over driving. If the DC resistance is going down from cooking the VC then the amp will clip earlier and earlier as the resistance and impedance of the coils drop.

You have been clipping that amp. 1550 watts produces serious heat. That is getting into space heater range!

 

[lovinthehd]

I choose the .775 after talking with crown and them suggesting to use this setting to have Max power potential from the amp. I chose the gain by what sounds good to my ear. Not sure what you mean by what preout level involved? Yes both lights.

I'd set gain to where it barely clipped at full output (e.g. the loudest you'll listen at, I use reference level), and I'd leave sensitivity at 1.4V unless I actually needed to move it to .775V. Pre-out level varies with pre-amp but looked back at your first post to get an answer, a Pioneer avr which likely has sufficient pre-out level for 1.4V setting in any case.

 

[moves]

That's how I would do it, considering the design of the amp. I'm still puzzled by the clipping lights though. What are the dimensions of your room (LxWxH)? Have you measured the sound level at your listening seat when the clipping occurs? (If you don't have a sound level meter, there are inexpensive phone apps that will do for this type of problem.)

I have the UMIK that I can use to test the sound level but I haven't tested it when clipping. The room is quote large... LWH = 30 X 13 X 7 feet.

 

[moves]

So that is a total of 1550 watts to a 1000 watt driver. It is excessive boost that is your problem. With those numbers you are past the point of diminishing returns. I think more will actually be less. That way you will free up more power where there is more meaningful program and the speaker is more sensitive. If you look at the power curves you can see sensitivity falling by 12 db per octave below 32 Hz. So that means it takes 10 times the amp power to produce the same acoustic output at 22 Hz than 32 Hz. So your whole bass program will sound better and cleaner by freeing up more power to the power bands where there is more program and actually more important program.

My last thought is that with all that power you might have damaged that driver already. I think you would be well advised to check the DC resistance of both voice coils and make sure they are in spec. If the DC resistance if either voice coil is below spec then you have a damaged voice coil or coils from over driving. If the DC resistance is going down from cooking the VC then the amp will clip earlier and earlier as the resistance and impedance of the coils drop.

You have been clipping that amp. 1550 watts produces serious heat. That is getting into space heater range!

Not that I don't trust you but not sure how I would damage the driver when Mark Seaton uses 4000 watt amps in his subs with the same driver. I checked the boost and it was raise to +5 db on the input level. I lowered back to zero to see.

Just want to clarify the High pass though... You quoted some info on the 15 inch driver but I have the 18. Should I set the highpass to 20 or 25 hz? Also do I use BW or LR 12db/octave ?