importance of flattening impedance in tube driven horn speaker

[AllenB]

Still not sure the point has been made.

I am using all active(MiniDSP) so no real problems with crossover interaction.

Are there any amplifiers involved, which have a significant output impedance, where there is a variation of the impedance of the driver from, say, the middle of its band, compared to its crossover end of its band?

I just wanted to quell any resonance in the passband

The box resonance is wanted. It is a normal manifestation of a rolloff. The amp doesn't have to do anything special, as long as the box and amp together can produce something useable.

 

[planet10]

T/S parameters are more variable than Brinkman describes.

T/S parameters are curves and the numbers one sees depending very much on where the numbers are pulled from the curves.

Parameters change with dynamics, weather at a minimum.

dave

 

[Brinkman]

Brinkman, yea, I'm aware of the small signal value of the T/S parameters. I was reading that you can use REW with the amp and some resistors...have you tried that? If so was it worth the time? Much difference?

No, I use DATS to generate T/S for the exact drivers I’m using and WinISD to get me in the ballpark enclosure-wise. You can adjust the drive level in DATS.

I might get flack for bringing this up, but for the tube amp / HF driver combo, you could flatten the impedance using an autotransformer with a swamping resistor in parallel between the amplifier and driver. The trade-off is wasting power heating a swamping resistor but you have at least 30 watts at your disposal so it’s really your call.

Since you’re using an active crossover upstream and no LF is present to saturate the autotransformer, you can get away with using an autotransformer with a relatively small core (making it inexpensive) which also lends itself to lower interwinding capacitance (less parasitics).

My $.02

 

[planet10]

A PP EL84 amplifier should not have that high an output impedance. I have had the Grant Fidelity version of the Yaqin thru here and i figured it was the best amp they had. Joe Rasmussu also has/is using it s. abasis for his modeified amp, so i would guess he judges the iron fine.

I am not a big fan of speakers with ugly impedance, but this amp should not have too great an issue with them.

A PP Pentode amp can be made into a current amp by removing feedback, but then you would need close to absolute flat (or an impedance curve that aids the FR at the extremes).

dave

 

[Brinkman]

Good points Dave.

Regarding drive level, would you just derive it by working backwards (using the rated sensitivity) from the average listening level at the main listening position plus baffle step compensation?

 

[brad944911]

Guys, thanks for all the advice here. I am trying to keep my inexperienced yap shut as to not confuse anything/anyone. I am absorbing and researching all points...rest assured.

 

[planet10]

Brinkman,

When designing a box i always start with the factory spec. I have only had to go back to the drawing board a few times.

I use WT2 from Smith + Larson for measuring… IMO the best SW for measuring parameters short of the pro stuff the factories use. I only use it for driver matching or drivers for which i have no data.

dave

 

[AllenB]

A PP EL84 amplifier should not have that high an output impedance.

I'd have thought so too. I would measure it, myself, but I'd expect it to be low.