Jump to content
The Klipsch Audio Community
Sign in to follow this  
FranJ

Peavey FH-1 "la scala" and first order crossover issue

Recommended Posts

Hello,

 

to make the story short I used to have a pair of heavily modded LaScalas; they were a split pair, and my very last mod was to replace the LaScala bass bins with Peavey FH-1 bass bins.

 

I'm pleased with the results (I love the LaScala but my bins have seen better days with metal handles in the side walls and everything, and they were prone to rattle and make noise; I was thinking of bracing them but I found these Peavey bins for super cheap instead)

 

BUT

 

I'm using a first order crossover (ALK Universal). Because of that, there's too much mid frequencies coming trough the bass horn (the FH-1 doesn't have 90° bends and has corner reflectors, it goes higher in frequency... I didn'thave the problem with the LaScala bass bins, the shape of the horn reduces the bandwith. Klipsch Belle users might have the same problem as me when using 1st order crossovers. It's very obvious and annoying with some songs, much less with others, but I'd rather get rid of the problem.

 

I have two possibilities:

 

1) build a passive low-pass 12dB/octave filter for the woofer only and use instead of the ALK low pass section

 

2) use an active low-pass x-over and a second amp, and go semi-active: low pass 400Hz 24dB linkwitz-riley on the bass horns, the rest still connected full range on the ALk crossovers.

 

What do you guys thing would be my best option?

Share this post


Link to post
Share on other sites

I would go for the active. But you could try some simple steps to cut out some midrange

Mechanics.

1.Add some space in front of driver by adding a baffle the front chamber will add some low  pass.

2. Add som fiber wadding in front of driver

 

Crossover

3. Add a zobel link to the bass driver, it will improve the action of the coil

4. Add a cap to get a 12 dB action

Share this post


Link to post
Share on other sites

Why do you think there is too much HF coming from the bass horn? 

 

Did you change out the Peavey woofer?  It's a great heat sink, but below 100 Hz, it's distortion is high.  Below 70 Hz, distortion exceeds fundamental. 

 

The throat of my FH-1s was nasty with splinters and rough routing.  However, I ended up with a nice sounding system by crossing from a pair of KP-480s at 100 Hz.  Crossover to the 902/511B is 1k. 

 

 

511B Top2.jpg

MockSys1.jpg

  • Like 1

Share this post


Link to post
Share on other sites

John, it's very obvious there's too much midrange and high midrange coming from the bass horns: if I disconnect the mid drivers, but leave the tweeters on, a (very untrained) ear could believe the sound is still full range. It would be very bad speakers, but still, it still sounds full range. When everything is connected, on some voices, there's a "wah-wah" sound from frequencies that are not supposed to come out from down there, coming trough and - I suppose- interferencing with what comes out the midrange horn. But I guess the main problem I have isn't interferences, I guess it's just you cannot cleanly pass frequencies above a certain point trough a folded bass horn, it starts sounding like a ...(very bad) horn. It would be more than OK for PA, but my goal is high-fidelity.

 

I'm using klipsch K33E woofers.

 

Globally I condider the Peavey bass horn to be superior to the LaScala bass horn, but I need to adapt the low-pass filtering.

The fact that you were crossing yours at 1KHz says it all! Try to do that with LaScalas!

 

I'm gonna go active. yesterday I found a brand new car audio crossover with 24dB linkwitz-riley slopes, phase switch, a variable subsonic filter that goes up to <40Hz, everything I need! It used to be an item priced around 200$, but I guess the brand -Caliber- stopped (?) and you now find the device for around 40$ on various websites

 

the active filtering is gonna be on the low pass only. The rest will be full range on the ALK crossovers. I might add some passive filtering of what comes in the mid/high amplifier, to relieve it from some low frequencies.

 

 

Share this post


Link to post
Share on other sites

O.K., it sounds like you have identified Intermodulation (IM) distortion.  The only cures for that are cutting out the Lows or removing the highs from the woofer.  The ones I built were for PA/vocal use at my church and I may well have cured it with the electronic crossover to the subs.  I'm not sure I'm following your proposed use of the car audio crossover, but the ALK crossover will change its performance some, don't know if it's enough to matter, if the woofer section is not terminated with some sort of a load.  Al designed it based on each driver's impedance.  A 6 ohm resistor in place of the woofer will do.  If you are blocking all of the lows electronically, then the resistor won't have to be big, say 20 watt? 

Share this post


Link to post
Share on other sites
20 hours ago, John Albright said:

O.K., it sounds like you have identified Intermodulation (IM) distortion.  The only cures for that are cutting out the Lows or removing the highs from the woofer.  The ones I built were for PA/vocal use at my church and I may well have cured it with the electronic crossover to the subs.  I'm not sure I'm following your proposed use of the car audio crossover, but the ALK crossover will change its performance some, don't know if it's enough to matter, if the woofer section is not terminated with some sort of a load.  Al designed it based on each driver's impedance.  A 6 ohm resistor in place of the woofer will do.  If you are blocking all of the lows electronically, then the resistor won't have to be big, say 20 watt? 

 

Yeah I remember Al K. saying that if you want to disconnect the woofer from its Universal crossover, you need to place a resistor in place. My "main" amplifier - the one that will feed the mid and tweeters trough the ALK crossovers- is 2 x 10watts so I guess 20watts resistor is more than enough.

The electronic crossover will send all frequencies under 400Hz to a separate amp feeding the bass bins... as usual... :) the choice of a car-audio product is dictated by opportunity on a very very low price. I figure most entry-level analogic crossovers are based on the same opamps + a bunch or resistors, the fact that it's a car-audio product won't matter much in this case. At that price, I'm not taking much risk anyways - and the midrange and treble won't pass trough it, the signal for those will still come straight from the preamp to the main amp, to preserve signal integrity and transparency (my preamp has two pairs of main outputs).

 

I'm looking forward to receive it and install it, there's a (small) chance that I won't be satisfied with the result, but I will learn at least what good can bi-amping bring to the plate.

 

I'm thinking of getting some in-line passive crossovers (such as harrison labs proposals) to remove some lows from the main amplifier without having to pass trough the active circuitry of the car-audio crossover: even tho I listen at very reasonable levels, removing some unnecessary bass from the small main amplifier can only be beneficial. Seems stupid to send a completely full range signal to an amp that feeds midrange and treble only.

Share this post


Link to post
Share on other sites

I know you're doing this on the cheap, but I used those Harrison Lab crossover bits for a while in a previous system iteration.  I got a 20 dB rise in my response curve at the crossover point.  I suppose there was an impedance mismatch. 

Share this post


Link to post
Share on other sites
13 hours ago, John Albright said:

I know you're doing this on the cheap, but I used those Harrison Lab crossover bits for a while in a previous system iteration.  I got a 20 dB rise in my response curve at the crossover point.  I suppose there was an impedance mismatch. 

 I wouldn't use them just at the crossover frequency with the low pass. That crossover frequency is set by the ALK crossovers at 400Hz/6dB; what I'd like to do is get those harrison laps f-mods as a , say, 150Hz high-pass in front of the amplifier driving the mid and high range. I just wanna free that small amp from the burden of bass amplification. I guess since it's outside the band reproduced by the mid and treble, the "technical imprefection" of the f-mods won't be noticeable.... but it's just a wild guess. We will see. it's gonna be loads of trial and error, that's sure.

Share this post


Link to post
Share on other sites
On 8/14/2016 at 4:22 AM, FranJ said:

 but my goal is high-fidelity.

 

I'm using klipsch K33E woofers.

 

Globally I condider the Peavey bass horn to be superior to the LaScala bass horn, but I need to adapt the low-pass filtering.

The fact that you were crossing yours at 1KHz says it all! Try to do that with LaScalas!

 

I'm gonna go active. yesterday I found a brand new car audio crossover with 24dB linkwitz-riley slopes, phase switch, a variable subsonic filter that goes up to <40Hz, everything I need! It used to be an item priced around 200$, but I guess the brand -Caliber- stopped (?) and you now find the device for around 40$ on various websites

 

the active filtering is gonna be on the low pass only. The rest will be full range on the ALK crossovers. I might add some passive filtering of what comes in the mid/high amplifier, to relieve it from some low frequencies.

 

 

I had K-33's in my FH-1's (used to have 6). I went active with a Behringer 2496 Linkwitz-Riley at 500 Hz. to an EV940 horn with DH1A driver. That was one sweet sounding basement OFFICE system, that, surprisingly went down to 30 Hz. in that small room.

 

I have said for years, and mostly been ignored here, that the FH-1 (I called them Cheap Scalas) was a superior bass bin, in every way, to an old LaScala bin (had several of those also). Even when modeling both in Hornresp, the FH-1 is smoother, and, of course built like a tank too!

 

Looks to me like the active route is the way to go for you also. Using a 12V setup designed for a car is just fine because of the efficiency involved, you will never use more than about 5 Watts PEAK.

Share this post


Link to post
Share on other sites

I still have my good shape FH1 pair - in that room and for certain music, I prefer a Karlson 12 topped with a K-tube (that can hit surprisingly hard with a Kappa 12a type) - a kitten some years back managed to fry a Samson amp which evaporated the K55V and APT150 voice coils - no damage to the woofer and the event was inaudible. (ultrasonic ?)  - got so much that not much can be used anymore.  Is the ALK Universal network with 2.5mH inductor worth a go for the K-horn?  - currently I have a type B rewired to charge coupled Type A using MBGO caps and a single 9 volt battery..  

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...