I first thought you could put a resistor in series, (this will also change the behaviour in the low frequencies, if I am not mistaken), but then I thought about the following.
Now I may be making huge errors as I am far from the theoretical speaker guru, feel free to disagree with my reasoning:
You want to decrease with 3db, which in essence means that it should be half as loud.
To me this would mean that you need to put an 8 ohm resistor (when using an 8 ohm speaker) of ample wattage in series with the speaker to have this effect. Then (depending on the frequency) around half of the power would go to the speaker, the other half would warm up the resistor.
This is not efficient. I think it would be better to reduce this volume at the pre-amplifier side.
As I said, there may be big errors in my reasoning...
Now I may be making huge errors as I am far from the theoretical speaker guru, feel free to disagree with my reasoning:
You want to decrease with 3db, which in essence means that it should be half as loud.
To me this would mean that you need to put an 8 ohm resistor (when using an 8 ohm speaker) of ample wattage in series with the speaker to have this effect. Then (depending on the frequency) around half of the power would go to the speaker, the other half would warm up the resistor.
This is not efficient. I think it would be better to reduce this volume at the pre-amplifier side.
As I said, there may be big errors in my reasoning...
First I need to lay out that I am new at all this so my "theories" may be worthless but here goes. My system is at my computer desk and is fed to a USB DAC to a DIY tube pre and DIY 6V6 PP amp, my speaker cables are DIY CAT5 and WireLogic Audio 500 interconnects all hooked to Fostex FE127E's in a small ported bookshelf cabinet on stands. My speakers are about 7' apart and I sit about 2' in front of them with a slight toe in.
The Fostex are a bit bright for me so taming that would be nice but foremost it seems as my amp opens up a bit at a higher volume......so if I decrease the sensitivity I was hoping to hit that "sweet spot" on my amp. As it is to hit the sweet spot is far to loud......I'm not sure if any of that makes sense.
The Fostex are a bit bright for me so taming that would be nice but foremost it seems as my amp opens up a bit at a higher volume......so if I decrease the sensitivity I was hoping to hit that "sweet spot" on my amp. As it is to hit the sweet spot is far to loud......I'm not sure if any of that makes sense.
Guitarists do that with power resistors hooked up to their tube amps
They like the sound of tubes distorting at high levels so the resistor trick works well. They call them hot plates or dummy loads. Here is a link that goes through all the different ways to load down tube amps.
Grail Tone - Low Volume, Fat Tone
They like the sound of tubes distorting at high levels so the resistor trick works well. They call them hot plates or dummy loads. Here is a link that goes through all the different ways to load down tube amps.
Grail Tone - Low Volume, Fat Tone
"foremost it seems as my amp opens up a bit at a higher volume......so if I decrease the sensitivity I was hoping to hit that "sweet spot" on my amp. As it is to hit the sweet spot is far to loud......"
Your class AB (?) PP amp should be running in class A to well over 90db in the near field with the 127e's.
It sounds like you are experiencing the improved sound quality that comes with spl's above about 80db, allowing you to hear bass in-balance with the mids and highs (see: Fletcher?Munson curves - Wikipedia, the free encyclopedia). The best solution is line-level 'loudness' compensation. Baffle step compensation would also help.
BTW, nice computer room system!
Regards,
Bob
Your class AB (?) PP amp should be running in class A to well over 90db in the near field with the 127e's.
It sounds like you are experiencing the improved sound quality that comes with spl's above about 80db, allowing you to hear bass in-balance with the mids and highs (see: Fletcher?Munson curves - Wikipedia, the free encyclopedia). The best solution is line-level 'loudness' compensation. Baffle step compensation would also help.
BTW, nice computer room system!
Regards,
Bob
Um, yeah.
Put an 8ohm resistor in series with an 8ohm nominal driver, you get 1/2 current flow, and each component sees half the voltage. So you actually get 1/4 the power through: you lose 6dB.
Could it be that you're running the amplifier into distortion a little? Extra (2nd particularly) harmonics to the sound can sound "nice", if not strictly accurate...
Chris
Somewhat more pertinently, a large amount of series resistance will significantly raise effective Q with a ~voltage source (Qe, Qt rise, B*L, Re drop. Or if you prefer to look at it from the POV of the amplifier, the output impedance the driver 'sees' will be higher). So the cabinet / baffle / whatever alignment will change.
Last edited:
I think you made an error: it is THE SAME CURRENT that flows through the resistor and the driver if they are in series. Not half the current. But the voltage is halved, hence half the power, or -3db.
As Scott mentions (and I suggested) - a big series resistance will influence the response (not only making it more silent, but shifting its characteristics) which should be calculated.
For a constant voltage, doubling the series resistance will half the current flow.
For amusement, fire up winISD pro, look under the "signal" tab, you can add series resistance. Lets see how much alignments change...
Substantially is the short answer Chris. For example, using the factory parameters of an FE126E (they're fictional, but serve), Q rises from a nominal 0.247 to a rather more substantial 0.466. The effect upon the basic box alignment / FR in your favourite WinISD Pro Alpha is fairly obvious, as you can see in the attached.
Using the aforementioned FE126E with factory parameters, here's what started out as a 4th order (QB3 if you prefer) box alignment, shown in yellow, with the usual 0.1ohms series resistance WinISD assumes to account for wire, contact losses etc. Blue = 2ohms series resistance applied, pink = 4ohms, orange = 8ohms.
Using the aforementioned FE126E with factory parameters, here's what started out as a 4th order (QB3 if you prefer) box alignment, shown in yellow, with the usual 0.1ohms series resistance WinISD assumes to account for wire, contact losses etc. Blue = 2ohms series resistance applied, pink = 4ohms, orange = 8ohms.
Attachments
Last edited:
This is looking way more involved than I thought I was hoping for an easy "pop in" fix for now. I know this isn't ideal but it's really my only option....something costing a few dollars at most. I'm mainly looking to tame the 7k-10k peak but if I could ALSO decrease the efficiency that was a bonus.
You may be thinking why a few dollar fix on a moderate system. Well there is NO way I could afford this set up but bartered my way into it. My brain is riddled with tumors and I just wanted to get this done before I go in for surgery. Assuming I retain my hearing after the surgery I want to come home to a completed system as I will be laid up for quite some time after.....if it's not as simple as popping in a resistor I'm not sure I have the mind set right now to fiddle with it nor the funds to go all the way and build my cabinets......ahhh such is life. I do appreciate all the info and help guys!
You may be thinking why a few dollar fix on a moderate system. Well there is NO way I could afford this set up but bartered my way into it. My brain is riddled with tumors and I just wanted to get this done before I go in for surgery. Assuming I retain my hearing after the surgery I want to come home to a completed system as I will be laid up for quite some time after.....if it's not as simple as popping in a resistor I'm not sure I have the mind set right now to fiddle with it nor the funds to go all the way and build my cabinets......ahhh such is life. I do appreciate all the info and help guys!
Sorry to hear about the tumors. Highly inadequate I know, but FWIW. Hope all goes well with the surgery.
If it's the 7KHz breakup that's bothering you & you don't want to physically damp the cones then slapping a shelving network (BSC filter) onto it seems about the best solution, as you're effectively lowering efficiency (which you say you want), & it's only one more component, so it's simple (ditto).
If it's the 7KHz breakup that's bothering you & you don't want to physically damp the cones then slapping a shelving network (BSC filter) onto it seems about the best solution, as you're effectively lowering efficiency (which you say you want), & it's only one more component, so it's simple (ditto).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.