Subwoofer Speaker Level High-Pass Filter � Questions about setup and possible sound issues.

[aguaazul]

Hi Klipsch Community, Long time Klipsch fan, 1^st

time Klipsch owner and 1^st time Klipsch Community Forum post.

I have

a Stock Dynaco PAS3 Tube Preamp & ST-70 Tube Amp that was tested / repaired to Spec by

Joe Curcio (Dynaco Doctor) and I just picked up a pair of 1984 Heresy’s to play

with this system just for music only. They lack bottom so I would like to connect up

my powered sub, an M&K VX-7.

The

sub has speaker in / out connections that run thru a speaker level high-pass

filter.

I don’t

know what happens to the signal except for the Low Bass Frequencies less than

80 HZ are filtered out from the Heresy’s.

My

question is will the Tube Sound from the Amp be degraded in the above 80 HZ

range running this setup?

Thanks

for your time and info!

[Dennie]

Welcome to the Klipsch Family Aguaazul, we're glad you're here! [<)]

I don't think it matters what type of amp you're using, it just takes the Lower Freq. Info and passes the rest on to the speakers.

I think you'll be okay. Remember PLACEMENT and your ROOM have more to do with it than the amp.

How do you have the speakers set up? Small room? Big Room? Are they against a wall? Do you have any room treatments? Lots of furniture? Etc...

Dennie

[mustang guy]

Hi Klipsch Community, Long time Klipsch fan, 1^st

time Klipsch owner and 1^st time Klipsch Community Forum post.

I have

a Stock Dynaco PAS3 Tube Preamp & ST-70 Tube Amp that was tested / repaired to Spec by

Joe Curcio (Dynaco Doctor) and I just picked up a pair of 1984 Heresys to play

with this system just for music only. They lack bottom so I would like to connect up

my powered sub, an M&K VX-7.

The

sub has speaker in / out connections that run thru a speaker level high-pass

filter.

I dont

know what happens to the signal except for the Low Bass Frequencies less than

80 HZ are filtered out from the Heresys.

My

question is will the Tube Sound from the Amp be degraded in the above 80 HZ

range running this setup?

Thanks

for your time and info!

Excellent question! I tend to think that if you are using the high power outs of the sub and they indeed have a built in HPF, then there may be degraded performance. Let your ears be your guide. If they do, you could always send the entire signal to the speakers by running two sets of speaker wires from the amp, one set to the sub, and one to the speakers.

[Guest " "]

yes it will degrade it....what about using the low level input instead...the RCA looking things?

[CECAA850]

I'll ask the same question here I asked elsewhere. Instead of using the high level outputs of the sub amp after running wires to the sub amp, why can't you run your speakers and sub anp input parallel? The amp can't offer too much in the way of resistance can it?

[aguaazul]

Thanks

for the warm welcome! I’ll try to respond to all responses in proper thread

order even though it is against my nature to be proper in other ways ;-)

I’m

hoping it will be a smooth addition. As far as the room, the Stereo listening

space is mixed within the home theater area. With a 17 month old son (Beau) running the

house, I took one of those 8 sided outdoor baby cage and created a rock and roll

style barrier between my equipment and people (Beau). Room size is 18’ wide

where the speakers fire toward and only 14’ deep. Across the back side of the 18’

span is a huge sectional couch. The Heresy’s

are 6’ apart measuring from their centers and my listening position is 9’ back

dead center. There is the 42” Flat Panel mounted freely on a post type TV stand

with glass shelves topping out at Heresy height level. Between them and outside

of the Heresy’s are the Home Theater Mains, Polk Audio Monitor70 Series II.

These are kinda tall next to the Hersey’s. The fronts of the speakers are 30”

from the back wall.

I

have not delved into the room treatment realm yet as funds are going towards the

Crites Crossover rebuilds (E-2), Dynaco Upgrades and Tube Rolling…

In the following replies I will delve into the Impedance

limitations of the Stock PAS3.

Room placement is limited due to Beau & Family. I’ll try

to post some pictures of the room as time allows. Thanks Dennie!

[aguaazul]

Hey

Mustang Guy… cars, horses, guitars… either way, Mustangs are pretty cool…

It’s

the degraded performance that I am worried about. I have dabbled in the sound engineering

arena as a fun summer job in the past and feel I can trust my ears. I will

indeed let my ears be my guide. I have been lucky enough to be able to confer

with Ken Kreisel himself, the inventor of

the subwoofer, the designer of the sub in question and sound engineer master regarding this.

I see

that in the owner’s manual that it is possible to run the sub and the speakers

from the same amplifier tap, the Dynaco ST-70 has 4, 8 & 16 ohm

connections. If I remember Ohms Law correctly, I would connect them up to the 4

Ohm Tap.

I have

another connectivity possibility coming up next…

[aguaazul]

Hey speakerfritz… I wish I had a second set of outputs on the

PAS3. It was this connection possibility (RCA thingies) that I procured an M&K VF-100. It

has a stereo input from the Pre to a

Stereo Output to the Amp and Stereo output to the Subwoofer plate amp of the

M&K VX-7 (or any other amp for that matter). I then contacted the inventor

of the subwoofer and designer of the sub that I own (Mr. Ken Kreisel) and he

was gracious enough to send me a very detailed hypothesis on this type of

connection. The M&K VF-100 is basically a 'Y' connector

that will show enough _output_ impedance to the amplifier. So I won't blow up

my amp.

But… If the _input_ impedance of the

M&K VF-100 was too low, it will cause the response of the PAS3 to roll off

in the low frequencies. This is why I posted this issue to all of you good

people. Ken was unable to give me _input_ impedance specs.

Another option is to install the Dynaco Doctor

PAS3 Mod board and then be able to run multiple amps off of the PAS3 single

output. It's a planned upgrade... as funds allow.

Ken has offered me instructions on

how measure the frequency responses of each different connection scenario with a

volt meter and a signal generator or a test disc. What a generous person… like

yourselves.

This is getting pretty thick... thanks for helping me work this out!

[djk]

The input impedance of the sub amp is probably too low for the PAS3.

If you driver the sub through the speaker level inputs the speaker out to the Klipsch will go through a large electrolytic cap which will degrade the sound a bit.

To remedy this you can install a small value polypropylen cap in paralle with it, 4.7µF is probably big enough.

You need not open up the sub amp, you can just run one cap per channel from the amplifier input red terminal to the speaker output red terminal. The mids and highs will sound much cleaner this way.

Alternately you can do a quasi bi-amp mode. This involves a cap between the PAS3 and the ST-70 to cause the bass to roll off below 80hz or so. Then the speaker outputs to the ST-70 driver the RCA inputs on the sub amp through a resistor and a cap. This method eliminates the electrolytic from the signal path to the Klipsch entirely. It also gives the amplifier more headroom by removing the deep bass. This is the basic method Vandersteen and Bag End use for their subs.

http://www.vandersteen.com/pages/Pdffiles/2wlit.pdf

[aguaazul]

The quasi bi-amp mode interests me. I wonder if just modifying the VF-100C would work. The M&K VF-100C
is basically a ‘Y’ connector with a .015
uF +/- 5% 100VDC cap between. I opened it up, inside is:

Channel 1: From the Input from Preamp there is
a direct line to the Sub output. From the Sub Output the cap is soldered
to the Amp output.

Channel 2: From the Input from Preamp there is
a direct line to the Sub output. From the Pre input the cap is soldered to the Amp
output.

Ken suggested that up the value of the cap inside of it to get the proper cutoff frequency. Ken States: “The ST-70 input impedance is 470k ohms, the VF-100 cutoff frequency is around 20Hz (into 470k ohms) which I estimated as the chart only goes to 200k ohm impedance. So, I am not sure if the VF-100 will do much to roll-off the Klipsch's. You might want to consider changing the capacitor value of the two capacitors inside the VF-100 if you want a higher cutoff frequency.”

I guess what I am looking for now is a way to calculate the larger Line level cap.