I was playing with several cabinet designs. Trying a very narrow tower (6 inch) which requires sharp edges as the driver is 5 3/4 inches. The baffle step was quite a challenge being almost 5 dB. When I added some width with a 3/4 radius round-over, of course the freq dropped as expected, but the step decreased several dB. I usually just am dealing with what is given, never played with it. Is this normal behavior? I have not seen anything talking about this is the texts.
This is often a stated reasons for going to wider baffles > > less to no BSC needed.
One could extrapolate this result from the fact that infinite baffles have no baffle step.
Perhaps this will help. Understanding Cabinet Diffraction ? Audioblog
One could extrapolate this result from the fact that infinite baffles have no baffle step.
Perhaps this will help. Understanding Cabinet Diffraction ? Audioblog
I measure several ways. Nearfield and 1 meter. If I know where it is going to be used, I will measure in the target location at the listening position. I use a "quick sweep" from True RTA, a pink, and an MLS using Sound easy. Every one gives somewhat different results as every one interacts with my office differently.
I finally built a router table so I can spin that 1 inch bit. It is high on my to do list after I work out my tweeter issues.
I finally built a router table so I can spin that 1 inch bit. It is high on my to do list after I work out my tweeter issues.
Allen,
You are quite right. None are gated to the extent I would wish them to be. Hence, the differing results. Gated measurements have their own issues. You may put in a narrow pulse and gate the recording so as to eliminate boundary issues but, even if your drive signal is a nice pretty mathematically pure pulse, drivers don't behave that way, so you get skewed measurements do to the acceleration delays of the driver. This is one of the properties that led me to getting a beginning understanding of amplifier design as the envelop varied with different amps.
My measurement system is not exactly portable, so setting up to measure in the driveway, ( single near boundary) or hanging from a tree is most inconvenient. Parts of the results are better, but the ambient noise where I live makes other parts worse. If Creative can'r gent my e-mu 1616 drivers to quit crashing, I will switch to a M-audio 610 and when I get around to a new laptop, I will be sure it has a firewire port. I don't have as basement to fill with old army surplus pads.
If I had the ability do build such a device: a fast sweep with a tracking notch filter and a control for distance/delay could possibly work. If someone would like to write that code, they could be a hero. I can do the system level design, but I don't code.
The end result is we still have to voice by hand in the intended listening position. All these measurements just help us to get close to start with, or to identify what may be wrong when we listen.
Wonder what those push-button systems do that show up in AVR's do? I don't like the results, but the measurement could be useful.
You are quite right. None are gated to the extent I would wish them to be. Hence, the differing results. Gated measurements have their own issues. You may put in a narrow pulse and gate the recording so as to eliminate boundary issues but, even if your drive signal is a nice pretty mathematically pure pulse, drivers don't behave that way, so you get skewed measurements do to the acceleration delays of the driver. This is one of the properties that led me to getting a beginning understanding of amplifier design as the envelop varied with different amps.
My measurement system is not exactly portable, so setting up to measure in the driveway, ( single near boundary) or hanging from a tree is most inconvenient. Parts of the results are better, but the ambient noise where I live makes other parts worse. If Creative can'r gent my e-mu 1616 drivers to quit crashing, I will switch to a M-audio 610 and when I get around to a new laptop, I will be sure it has a firewire port. I don't have as basement to fill with old army surplus pads.
If I had the ability do build such a device: a fast sweep with a tracking notch filter and a control for distance/delay could possibly work. If someone would like to write that code, they could be a hero. I can do the system level design, but I don't code.
The end result is we still have to voice by hand in the intended listening position. All these measurements just help us to get close to start with, or to identify what may be wrong when we listen.
Wonder what those push-button systems do that show up in AVR's do? I don't like the results, but the measurement could be useful.
Mathematically, a pure pulse is simply all frequencies at the same time. If your woofer doesn't trace the leading edge, what does it mean? It doesn't do 20kHz. No problem. Why not try HolmImpulse, Dr Geddes has vouched on its behalf regarding its measuring abilities.
I don't have much luck with pads. Some absorb, some reflect and some are just transparent despite what they look like. I can get clean down to the 200-300Hz region in a domestic room without pads and find that is sometimes enough.
What push button things in AVRs are you talking about, are they the deconvolution signals used to reverse engineer rooms on the fly? If so you'd probably find me walking the other way
I don't have much luck with pads. Some absorb, some reflect and some are just transparent despite what they look like. I can get clean down to the 200-300Hz region in a domestic room without pads and find that is sometimes enough.
What push button things in AVRs are you talking about, are they the deconvolution signals used to reverse engineer rooms on the fly? If so you'd probably find me walking the other way
It seem every brand has their own automatic frequency eq system Audissy or something. Don't know how they work, but the demo's I heard led me running, not walking away. Even when I measure a room for integrating the subs, I am never happy with the flat measured response once I put music through it. I prefer a lot less power than measured. Music or natural speaking reveals a lot more. Nothing beats a voice you know well.
I have had quite a bit of luck building absorption panels for room tuning using damaged fiberglass ceiling tiles. Joe DeApollito recommends old cotton army pads. There are various OEM products, but pretty expensive. The real ones will provide specifications. Not cheap of course. It should not be too difficult to build range specific panels for the step range, say 300 to 1K. Below that, the depth of absorbers gets very difficult.
PA,
Check out Linkwitz on open baffle design.
I have had quite a bit of luck building absorption panels for room tuning using damaged fiberglass ceiling tiles. Joe DeApollito recommends old cotton army pads. There are various OEM products, but pretty expensive. The real ones will provide specifications. Not cheap of course. It should not be too difficult to build range specific panels for the step range, say 300 to 1K. Below that, the depth of absorbers gets very difficult.
PA,
Check out Linkwitz on open baffle design.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.