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In Reply to: RE: What attributes make a driver a good match for a SET? posted by LewinskiH01 on May 17, 2017 at 18:28:13
The issue with SET's so far as the driver is concerned is that the bass response and to a degree elsewhere is adversely effected by having a significant "source impedance". That source impedance varies from model to model etc. In that way, the variable impedance can cause issues like it does with text book passive crossovers.
While SS and closed loop tube amps have a low output impedance and so are effectively a Voltage source, the Voltage at the speaker terminals will go up and down with frequency, changing the normal frequency response if there is a significant impedance in series. Where the loudspeaker has a low impedance, that will have reduced output, where there is a bump in the load impedance, there will be a rise in output, compared to Voltage driven.
What your would want then is an efficient speaker with the flattest impedance curve you can find -or- find an efficient speaker, measure it on your amplifier outdoors (no room effects) and eq it flat, then move inside -or- using software, design a conjugating network that tames the impedance while minimizing the sensitivity loss.
"using software, design a conjugating network that tames the impedance while minimizing the sensitivity loss".........Tomservo
Is this how you have tamed the SH-50?
Well no, i really didn't take any pains to keep the impedance constant as most, nearly all who use them have amplifiers that have a lower output impedance like SS, switching or closed loop tube amps.
I have looked at doing that however on other existing speakers and the process can be sped up immensely by using a program like lspcad.
I'll be designing an open baffle speaker using an 8" full range driver with super low inductance, coupled to twin Eminence Alphas and an Original Heil AMT tweeter. I can't afford LSPCAD right now, but I can get by without it.
I don't ever plan on going back to tubes (left those bias/tube replacment headaches behind in my 20's) but I have tried class AB, Single Ended FET Class A (with tube-like 2nd order distortion products), and soon to be Class D on my SH-50's. So I have none of those non-linear "dynamic voltage divider" issues that are prominently provided by single ended tube amplifications.
I have yet to try Rephase on a MiniDSP since I use a Yamaha Pre Pro for 6.2 and 2.2. BUT, the YPAO room correction does a great job of taming the abundant bass on the SH-50. It still blows my mind that so much bass can come out of such a small horn. In my room, I only need Sub bass below 40 Hz, with my "subtle" TH-50's.
This is still the best sound I've ever had, but I do find the 3D qualities of open baffle speakers to be interesting as a second setup to play with. We shall see.
That being said, I have heard 8" whizzer cone drivers on open baffle and they did sound very good with SET and other amps. Besides, I believe in Room EQ, which would go a long way to tame any frequency/impedance dependent anomalies anyhow.
Perhaps the SET amp lovers need to look to those solutions also.
If you can measure the SH-50's (or anything else) outdoors so you don't have room effects, RE-phase (and a mini dsp) can take you the last bit of the way.
The only measurements i have handy are an sh-50 in my living room at a meter with and without Re-phase's correction impulse.
If you want to try it, i can talk you through if there is a problem
Which miniDSP? Is it the "Open DRC" if so, I'm assuming we want the one that is full digital and no analog?
"I'll be designing an open baffle speaker using an 8" full range driver with super low inductance, coupled to twin Eminence Alphas and an Original Heil AMT tweeter."
There are drivers which a manufacturer or customer can call a "full range driver", but there is no such thing as a full range driver. We've covered this misnomer multiple times in the past. Even "TheTubeGuy1954" gets it now. Moving on...
You should consider using two (per channel) low frequency drivers, wired in-phase. This will give you essentially omni-directional LF output, without the front/back sound cancellation problems from the baffle.
Inmate #51 shall be set free, as he understands !
I don't plan on using it as a full range, but as a broadband midrange with a very light cone and a low hysteresis coil from 200-1200 Hz.(give or take after measurements).
The AMT tweeter is currently the one that is most copied, since the patents ran out...........for good reason. 21 square inches of diaphragm, controlled directivity front and back with low distortion AND transient response that rivals horns make it a great candidate for this.
On the bass side, the only bass I have heard that rivals horn bass is open baffle, since it is effectively, decoupled from the room. I regard the "cancellation" as a solution, and not a "problem" as you put it, for the twin 15" woofers I'll be using.
If I were to enclose woofers again, I would go back to my Quarter Pie Horn design, which I shared the the Klipsch Forum to over 50,000 views. It's been built all over the world with great success. Been there, done that, want to try other stuff for fun.
Klipsch Theater Horns with TAD drivers, Horn bass and, most recently all Danley tapped horn and synergy horn products are my reference standards, not the overpriced stuff at "high end" shows. I regard Open Baffle speakers as the antithesis to horn systems, so I want to hear both ends of the product spectrum. I'm pretty sure I will be giving up horn DYNAMIC IMPACT for 3 Dimensional depth, but it's a worthwhile experiment with cheap and used drivers and cheap lumber recycled from Cherry wood desks I got at Salvation Army for 40 bucks!
The loudspeaker cabinet.
This part is really a problematic component. It plays its very important role in
separating the sound
and backside of the units.
Any attempt to mix them, no
matter how, will result in wrong reproduction.
As far as I can see, the "expert by self proclamation and publication," to whom, you bow, is merely parroting the design philosophy of B&W, whose many designers have come up with clever ways to maximize their custom moving coil driver performance in various sealed/ported box configurations, including their "Matrix" box stiffening methods, which are technically sound......no pun intended.
Then you use this unpublished parrot writing whose author did not withstand the peer reviewed aspect of the Audio Engineering Society as a basis to criticize something that has been BUILT successfully by others who have, obviously, a broader band of knowledge regarding all speaker types, including the B&W offerings, which are more space heater than loudspeakers with their limited dynamic range and flammability when a 30 db watt amplifier is employed in an attempt to derive a single acoustic watt of output without gross IM distortion or burning the house down.
Inmate Claude shall remain locked up, for he exists in a non-reality:
"On the bass side, the only bass I have heard that rivals horn bass is open baffle, since it is effectively, decoupled from the room. I regard the "cancellation" as a solution, and not a "problem" as you put it, for the twin 15" woofers I'll be using."
Really ? bass cancellation is the solution to bass ?
(Is there a doctor in the house?)
Yes, that is how a 1/4 wave based, (Figure 8) pattern is created, like the H box as cited by Martin King's papers. The bass that is cancelled is the bass that would emanate on the sides, where it's not needed or wanted. By spacing the cabinet far away from the front and side walls, the rear bass arrives at the listener greater than 20 milliseconds in time. Open baffle speakers have a pleasant 3 Dimensonal presentation that is uncanny.
Go read the work of Sigfried Linkwitz, of Linkwitz-Riley filter fame on open baffle for technical details that required many years of work on his part.
Instead of criticizing something you have never tried, you might want to go and build one, then compare notes with those who have done it.
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