Hello. This is my first post in the subwoofer section. Be gentle.
Even though this isn't a 'subwoofer', I believe ya'll have a great understanding of my goal.
This is not a home theater application. 2 channel music. Sub 20Hz is not important.
One of my speakers uses the TD15H+ in a slot port configuration. I absolutely love it.
Next speaker will use passive radiators. Options?
1) single TD15H with dual 12" pr's.
2) single TD15H with dual 15" pr's.
3) dual TD15H's. One front firing, one back firing, out of phase (I don't believe Isobarik applies. There is no 'sealed' woofer), dual 18" pr's.
I've read a bit on passive radiators, so have a basic understanding.
~ can each passive radiator be tuned to a different frequency?, or should they be identical?
~ since this isn't an Isobarik, will the box volume be massive?
~you may have noticed I use tube amplification. Wiring in parallel results in a 4 ohm impedance. Not good for tubes. Bi-amping is not an option.
No doubt many more questions will arise.
Even though this isn't a 'subwoofer', I believe ya'll have a great understanding of my goal.
This is not a home theater application. 2 channel music. Sub 20Hz is not important.
One of my speakers uses the TD15H+ in a slot port configuration. I absolutely love it.
Next speaker will use passive radiators. Options?
1) single TD15H with dual 12" pr's.
2) single TD15H with dual 15" pr's.
3) dual TD15H's. One front firing, one back firing, out of phase (I don't believe Isobarik applies. There is no 'sealed' woofer), dual 18" pr's.
I've read a bit on passive radiators, so have a basic understanding.
~ can each passive radiator be tuned to a different frequency?, or should they be identical?
~ since this isn't an Isobarik, will the box volume be massive?
~you may have noticed I use tube amplification. Wiring in parallel results in a 4 ohm impedance. Not good for tubes. Bi-amping is not an option.
No doubt many more questions will arise.
Attachments
Option 2 works. PRs need to be capable of moving 2x the air of the main driver.
- PR tuning should be the same for both. There's a thread about that around here somewhere.
- Cabinet volume will be 2x that of a single driver. You'll need 4x 15" PRs or similar. Up to you if that's "massive" or not.
- When it comes to simulations, make sure you account for the output impedance of your amplifier.
Since this is a dedicated subwoofer, I really think you should use a seperate amp for it. Doing a passive crossover <100Hz needs some big and expensive components, and still won't be as good as an active crossover.
Chris
- PR tuning should be the same for both. There's a thread about that around here somewhere.
- Cabinet volume will be 2x that of a single driver. You'll need 4x 15" PRs or similar. Up to you if that's "massive" or not.
- When it comes to simulations, make sure you account for the output impedance of your amplifier.
Since this is a dedicated subwoofer, I really think you should use a seperate amp for it. Doing a passive crossover <100Hz needs some big and expensive components, and still won't be as good as an active crossover.
Chris
Thank you Chris.
Here is a bit more information;
The above speaker has a frequency dip. It is centered around 240Hz. My first assumption is floor bounce from the mid woofer. After inverting the top three driver section, the dip didn't change. This leads me to a woofer issue.
I can read all I want. For me, trial and error is the fun part of this hobby.
Question; how do dual side firing passive radiators affect overall frequency response?
Here's another problem:
The next speaker will use a slightly more efficient midrange and tweeter. I don't like the sound of resistors, so padding them down is not an option. I need more output.
The next speaker will likely have two mid-base drivers. D'Apollito? TD6m's or TD8m's.
Question; will dual TD15H's, one front firing, one back firing, give me +3dB of output?
Here is a bit more information;
The above speaker has a frequency dip. It is centered around 240Hz. My first assumption is floor bounce from the mid woofer. After inverting the top three driver section, the dip didn't change. This leads me to a woofer issue.
I can read all I want. For me, trial and error is the fun part of this hobby.
Question; how do dual side firing passive radiators affect overall frequency response?
Here's another problem:
The next speaker will use a slightly more efficient midrange and tweeter. I don't like the sound of resistors, so padding them down is not an option. I need more output.
The next speaker will likely have two mid-base drivers. D'Apollito? TD6m's or TD8m's.
Question; will dual TD15H's, one front firing, one back firing, give me +3dB of output?
Passive radiators act like a port, except they don't have the out-of-band resonances that ported boxes usually do.
Have you tried stuffing the port in your current cabinets to see if the 240Hz dip disappears?
With regards to your allergy of resistors, I'd politely suggest that you get over it. There are a staggering number of resistors that signal must pass through before it even gets recorded anywhere. I'm talking about the mixing desk at the studio end. I promise you they're not using "audiophile" resistors, either. 1/4-watt carbon film, probably. Tens or hundreds of them, depending on whether the mixing was all-analogue, or done in a computer as is often the case these days.
Resistors between the amp and speaker will have some non-linear effects, sure, but nothing that can't be worked out with proper application of LCR and Zobel filters. Edit - except at low frequencies, where the components can get very large. This is where bi-amping comes into its own.
Adding another driver in parallel adds +6dB, assuming the amplifier can supply the extra current. Put them in series, and gain will be 0dB, although the amp will be supplying half the current as the impedance at the terminals has doubled.
NB - this assumes an amp that's a pure voltage source. Valve amps aren't always that.
That only works when the drivers are within 1/4 wavelength of each other at the listening position. With one driver firing forwards and the other backwards, that will depend heavily on your crossover frequency. Below 100Hz, it'll be fine.
Chris
Have you tried stuffing the port in your current cabinets to see if the 240Hz dip disappears?
With regards to your allergy of resistors, I'd politely suggest that you get over it. There are a staggering number of resistors that signal must pass through before it even gets recorded anywhere. I'm talking about the mixing desk at the studio end. I promise you they're not using "audiophile" resistors, either. 1/4-watt carbon film, probably. Tens or hundreds of them, depending on whether the mixing was all-analogue, or done in a computer as is often the case these days.
Resistors between the amp and speaker will have some non-linear effects, sure, but nothing that can't be worked out with proper application of LCR and Zobel filters. Edit - except at low frequencies, where the components can get very large. This is where bi-amping comes into its own.
Adding another driver in parallel adds +6dB, assuming the amplifier can supply the extra current. Put them in series, and gain will be 0dB, although the amp will be supplying half the current as the impedance at the terminals has doubled.
NB - this assumes an amp that's a pure voltage source. Valve amps aren't always that.
That only works when the drivers are within 1/4 wavelength of each other at the listening position. With one driver firing forwards and the other backwards, that will depend heavily on your crossover frequency. Below 100Hz, it'll be fine.
Chris
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