shouldn't use my speakers with a tube amp?
- Thread starter brightpav
- Start date
targeteye
Super Member
ok.. but what do you use now to drive you woofers and why did you settle on it? and just to be clear... i'm talking aout the runs from the amp to the speakers as this may be of significant lenght to make a difference. ALso,, would you think inserting a .47 ohm resistor in series with your woofer could impact the ability of the amp to control it?
dnewma04
The Healer
I have somewhere around 14awg DIY wires currently made by braiding some wire I had laying around but will sometimes swap. I settled on them because I made them and they have really cool wood block cable "pants" I made that look sweet.
My midbass drivers are AE Speakers TD15M, 15" drivers driven by Bogen MO-100 amplifiers that have been highly modified, IcePower ASC200 modules, or a Sima SS amp.
I just have heard too many low damping factor amps sound great despite thinking they wouldn't and too many extremely high damping factor amps show no more "woofer control" than an amp with a DF of 20.
My midbass drivers are AE Speakers TD15M, 15" drivers driven by Bogen MO-100 amplifiers that have been highly modified, IcePower ASC200 modules, or a Sima SS amp.
I just have heard too many low damping factor amps sound great despite thinking they wouldn't and too many extremely high damping factor amps show no more "woofer control" than an amp with a DF of 20.
targeteye
Super Member
Perhaps thats when you were using the 32 Gauge cables
. Try the .47 ohm experiment and report back. Just remember to "crank it" to get the current demands up.Steve
targeteye
Super Member
Dave,
I like your math. I proves that in SS amps very high damping factors have little effect. However it does not include typical DFs that can be found in typical Tube amps.
Continuing on with your analysis lets look at a Mcintosh 275. Arguably one of the best tube amps out there with a DF of 20.
Total sytem DF=10 seems we are starting to seem some significant difference.
Dynaco ST-70 DF=15... total system DF=9. Getting pretty bad now.
Mcintosh MC30 DF=12 System 7.8.
All of those are respectible amps. You start to get lower on the totem poll they don't even publish specs that I can find.
I think that you math actually proves that once you get into the realm of DF rating for tube amps it does start to become a factor. I agree once you up in the 50 or higher range for a SS amp it becomes a moot point. I also respect your point about the crossover. A very reactive low impedance woofer had better have a matching very low impedance crossover elsewise as you point out the speaker could be negatively impacted.
Steve
I like your math. I proves that in SS amps very high damping factors have little effect. However it does not include typical DFs that can be found in typical Tube amps.
Continuing on with your analysis lets look at a Mcintosh 275. Arguably one of the best tube amps out there with a DF of 20.
Total sytem DF=10 seems we are starting to seem some significant difference.
Dynaco ST-70 DF=15... total system DF=9. Getting pretty bad now.
Mcintosh MC30 DF=12 System 7.8.
All of those are respectible amps. You start to get lower on the totem poll they don't even publish specs that I can find.
I think that you math actually proves that once you get into the realm of DF rating for tube amps it does start to become a factor. I agree once you up in the 50 or higher range for a SS amp it becomes a moot point. I also respect your point about the crossover. A very reactive low impedance woofer had better have a matching very low impedance crossover elsewise as you point out the speaker could be negatively impacted.
Steve
Last edited:
dnewma04
The Healer
Well, the next step in the math is determining the difference in damping at the speaker. What you'll find is that the increase or decrease in damping is roughly similar to adding or reducing the amount of stuffing in a sealed box or a small change in cabinet size.
I am too distracted to do the math for that right now, but in typical scenarios, we are talking about .2-/.4dB boosts in the bass and in worst case scenarios, it might even approach .67-.75 dB. Identifiable in the real world? Hard to say.
I've heard some amplifiers with DF of less than 5 that when paired up with the right speakers (in this case, critically damped sealed enclosures) that displayed better perceived woofer control than just about any other system I've ever heard.
I virtually ignore it as an important specification.
I am too distracted to do the math for that right now, but in typical scenarios, we are talking about .2-/.4dB boosts in the bass and in worst case scenarios, it might even approach .67-.75 dB. Identifiable in the real world? Hard to say.
I've heard some amplifiers with DF of less than 5 that when paired up with the right speakers (in this case, critically damped sealed enclosures) that displayed better perceived woofer control than just about any other system I've ever heard.
I virtually ignore it as an important specification.
dr*audio
Fish fingers and custard!
Dave,
The math is interesting, but I think your modeling is flawed when you use the DCR of the crossover. The amp is not driving the crossover at DC (we hope) and I think you want to use the impedance of the crossover at 20Hz - 2000Hz for a 2 way system. It will be 8 Ohms at the resonance point and drop below that frequency. Using 8 = 2 x pi x 2000 x L, I get .64mH for the value of the choke. Plug that back into the equation and you can calculate the impedance at any desired frequency. So lets pick a few frequencies of interest:
20 Hz = .08 Ohms
100Hz = .40 Ohms
400Hz = 1.61 Ohms
So for very low frequencies, the crossover should have negligible affect on the damping, but at 400 Hz, where your room boundary effect is, it pretty much nulls out any benefit from improved damping in the amp.
The take-away from this, I think, is that if you have speakers that are capable of producing 20 Hz, you may benefit from an amp with high damping ratio.
Therefore, those small bookshelf Mordaunt Short speakers probably don't go below 60Hz, and damping should have little effect on the sound.
The math is interesting, but I think your modeling is flawed when you use the DCR of the crossover. The amp is not driving the crossover at DC (we hope) and I think you want to use the impedance of the crossover at 20Hz - 2000Hz for a 2 way system. It will be 8 Ohms at the resonance point and drop below that frequency. Using 8 = 2 x pi x 2000 x L, I get .64mH for the value of the choke. Plug that back into the equation and you can calculate the impedance at any desired frequency. So lets pick a few frequencies of interest:
20 Hz = .08 Ohms
100Hz = .40 Ohms
400Hz = 1.61 Ohms
So for very low frequencies, the crossover should have negligible affect on the damping, but at 400 Hz, where your room boundary effect is, it pretty much nulls out any benefit from improved damping in the amp.
The take-away from this, I think, is that if you have speakers that are capable of producing 20 Hz, you may benefit from an amp with high damping ratio.
Therefore, those small bookshelf Mordaunt Short speakers probably don't go below 60Hz, and damping should have little effect on the sound.
targeteye
Super Member
Dave,
The topic at hand is not a speaker with a sealed enclosure. It's a ported speaker with an aluminum cone and has what is described as "piston like movement" at lower frequencies. I'm assuming Piston Like means very long excursion. In such a speaker the damping capability of the amp is much more important than in a aucoustic or surround dampened speaker wouldn't you agree? At certain frequencies the speaker is relying almost exclusively on the amplifier for dampening.
Steve
Last edited:
dnewma04
The Healer
There is more cone control, and significantly so, in a ported enclosure above tuning. Below tuning, the amplifier will not have any impact.
Can you describe what you mean by a "Surround dampened" speaker, I'm unfamiliar with the term. If you are talking about the mechanical damping properties, they are always signficantly out damped by the electrical damping provided by the motor.
Can you describe what you mean by a "Surround dampened" speaker, I'm unfamiliar with the term. If you are talking about the mechanical damping properties, they are always signficantly out damped by the electrical damping provided by the motor.
Last edited:
targeteye
Super Member
Not according to these curves. The port is like tunned LC circuit offering very high impedance at reasonance and very low impedance above and below resonance.
The refleced voice coil impedance is interensting.
Attachments
targeteye
Super Member
I guess i'm just making up terms now. It happens
.What i'm refering to is a speaker with a more Rigid surround. The surround itself is presenting a restoring force to the speaker cone. (and perhaps the spider itself to a lesser degree). Speakers relying on a low compliance suspension like this would be most often be vintage. I don't think anyone currently makes speakers like this (but I could be wrong).
Steve
dnewma04
The Healer
Compare the cone excursion of a sealed box to a ported box. A ported box, at tuning has very little movement. Above the tuning frequency, it will be lower than a sealed box up until about one octave above tuning where they will be essentially the same. Under the tuning frequency, ported speakers will unload.
dnewma04
The Healer
The overall damping of a speaker Qts is comprised of two components Qes (electrical damping) and Qms (mechanical damping). It's rare to find a speaker where the Qms will have a large affect on damping. The damping is always dominated by Qes. That's not to say that Qms is something that can be ignored, there are circumstances where it can be important, but in terms of overall damping, it plays a much less signficant role. The primary role of the spider and surround are to keep things centered.
targeteye
Super Member
Ok so I did some experimenting today. I disconnected the scott 299 (7189 amp) from my JBL L150a today. In its place I added a Marantz 170DC SS amp. Played some tunes. I immediately noticed the bass was a bit tighter than with the scott and overall the sound was more.. well.. "accurate". It just didn't have the same sound I was used to. Frankly.... I didn't like it. I guess my ears have just gotten used to the slight looseness the 299 was providing. So back to the shelf the Marantz went. Just my experience. could have been my immagination? Possibly.
Steve
Steve