Modifying an existing 800Hz crossover to 1000Hz

[Chayla]

I built a bass cabinet using an Eminence Kappalite 3015LF Neo 15" Driver and an Eminence LA8-CNMBA Neo 8" Midrange crossed over at 800Hz with an Eminence PXB2:800 2-Way Crossover Board 800 Hz. I first tried the cab crossover at 500Hz but too much bottom end was getting to the mid.

I find that even at 800Hz I’m sending too much bass to the mid, so I’d like to modify the PXB2:800 to about 1,000Hz or maybe even 1,200Hz. Can this be done by removing a cap on the board and soldering in one with a different value, or maybe adding another cap in parallel with the cap on the board now?

Or can I simply add a cap in series between the midrange and the crossover midrange output or will this completely alter the midrange crossover point?

I can't seem to find a high power 2-way crossover at 1000Hz.

Any help with this would be appreciated.

[Bill Fitzmaurice]

The problem is that you have to change all of the components, on both the high and low pass sections. In other words, an entirely new crossover.

[Chayla]

The problem is that you have to change all of the components, on both the high and low pass sections. In other words, an entirely new crossover.

OK thanks. I thought it might be easier than that. What about just putting another cap in series with the midrange, between the crossover's output and the speaker?

[Bill Fitzmaurice]

What about just putting another cap in series with the midrange, between the crossover's output and the speaker?

What about the woofer? Its low pass frequency must also be raised. Besides, going from 800 to 1kHz will have only a slight effect. I don't know why you think there's too much low end in the LA8 driver, as it's quite happy down to 200Hz, but if there really is move the knee by an octave. That does reduce the LA8s bandwidth to only an octave, but to tell the truth you should probably have used a dedicated midrange driver.

[Chayla]

What about just putting another cap in series with the midrange, between the crossover's output and the speaker?

What about the woofer? Its low pass frequency must also be raised. Besides, going from 800 to 1kHz will have only a slight effect. I don't know why you think there's too much low end in the LA8 driver, as it's quite happy down to 200Hz, but if there really is move the knee by an octave. That does reduce the LA8s bandwidth to only an octave, but to tell the truth you should probably have used a dedicated midrange driver.

It's a bass guitar cabinet and I'm hearing a bit of distortion coming from the midrange when playing the lower notes on the E string. Other than that it sounds great. Not sure what you mean by moving the knee by an octave. What sort of dedicated midrange driver are you referring to? Is the LA8 not a dedicated mid?

[LelandCrooks]

The knee is where the response rolls off, it looks like a knee.

Check your xover for loose connections, and that it's securely held. Experience of other users found what you're describing coming from a solder joint, board rattling in the box, or midrange not sealed tightly to the cab.

[Chayla]

The knee is where the response rolls off, it looks like a knee.

Check your xover for loose connections, and that it's securely held. Experience of other users found what you're describing coming from a solder joint, board rattling in the box, or midrange not sealed tightly to the cab.

OK I'll check the connections on the crossover. All of them are spade lug connectors - nothing has been soldered. I'll also check the screws on the midrange to make sure they're all tight.

Is the Eminence LA8-CNMBA Neo 8" Midrange considered a dedicated midrange driver?

[Bill Fitzmaurice]

Is the LA8 not a dedicated mid?

It is not. We use them in DR200 for full range operation. The Alpha 8 MRA is a dedicated midrange driver.

I'm hearing a bit of distortion coming from the midrange when playing the lower notes on the E string.

You shouldn't, not even with a 300Hz high pass. Is the driver in a separate sealed compartment?

[Chayla]

Is the LA8 not a dedicated mid?

It is not. We use them in DR200 for full range operation. The Alpha 8 MRA is a dedicated midrange driver.

I'm hearing a bit of distortion coming from the midrange when playing the lower notes on the E string.

You shouldn't, not even with a 300Hz high pass. Is the driver in a separate sealed compartment?

I wonder why Eminence would say that the LA8 is a midrange if it's not a midrange. Yes the LA8 is in it's own sealed chamber in the cabinet. I went with the LA8 because it had twice the power handling of the Alpha 8 MRS (it was also a HECK of lot more expensive). I am running a 350 watt QSC GX3 power amp into the cabinet, so I wanted the extra wattage on the mid.

Should I remove all the spade lug connectors and solder all the crossover connections?

[Rune Bivrin]

There's a substantial chance the distortion you're hearing is present in the signal to the speaker, and that the midrange exposes something which was always there.

I'd start by disconnecting the mid. It should then be completely quiet. If it isn't you have a leak.

Next step is to check all connections. I wouldn't go so far as to solder everything that's connected with spaces. Just use the old wiggle test to see if something is amiss.

If you have the option try another full range speaker - possibly with a series resistor to keep power down - to see if the distortion is present even then.

[Bill Fitzmaurice]

I wonder why Eminence would say that the LA8 is a midrange if it's not a midrange.

They don't. The call it a mid/bass, which means good from 100Hz. Midrange drivers are generally good only to 400Hz, and have higher sensitivity and midrange extension than mid/bass drivers.

I went with the LA8 because it had twice the power handling of the Alpha 8 MRS

Moot. What counts is sensitivity. The A8MR crushes the LA8 in that respect, and therefore also in actual output capacity. The higher power capacity of the LA8 is only there to handle the higher power demand if it's run to its full bandwidth. You only want to use the LA8 to take advantage of its high xmax. Above 400Hz that xmax is not an advantage, while the lower sensitivity and reduced HF extension is a distinct disadvantage.

You can't reach the displacement limit of the LA8 with even a 500Hz highpass without exceeding its thermal capacity, so any distortion must be coming from the signal chain, not the driver.

[Chayla]

I wonder why Eminence would say that the LA8 is a midrange if it's not a midrange.

They don't. The call it a mid/bass, which means good from 100Hz. Midrange drivers are generally good only to 400Hz, and have higher sensitivity and midrange extension than mid/bass drivers.

I went with the LA8 because it had twice the power handling of the Alpha 8 MRS

Moot. What counts is sensitivity. The A8MR crushes the LA8 in that respect, and therefore also in actual output capacity. The higher power capacity of the LA8 is only there to handle the higher power demand if it's run to its full bandwidth. You only want to use the LA8 to take advantage of its high xmax. Above 400Hz that xmax is not an advantage, while the lower sensitivity and reduced HF extension is a distinct disadvantage.

You can't reach the displacement limit of the LA8 with even a 500Hz highpass without exceeding its thermal capacity, so any distortion must be coming from the signal chain, not the driver.

I'm going to order the Alpha 8MR from Parts Express today. Hopefully it will fit into the sealed enclosure that I made for the LA8. It's only $37 so it won't break the bank to switch it up. Do you think the crossover may be sending a distorted signal to the mid? I can't see it being the brand new QSC amp or my brand new Sansamp bass preamp. Can a passive crossover distort the signal?
When I play the same signal into my other cabinet with a two Delta 10's and an 18 inch Selenium I don't hear the distortion. This cabinet has no crossover whatsoever. The two 10's are 16 ohm speakers wired in parallel, and that circuit is wired in parallel with the 8 ohm Selenium to create a 4 ohm load.

[Bruce Weldy]

Often what you hear as distortion is actually something rattling in the box. Get it "distorting", then start putting pressure on the various components - you might be surprised what it loose and rattling.

It's certainly worth a try before spending money or digging into the electronics.

[Chayla]

Often what you hear as distortion is actually something rattling in the box. Get it "distorting", then start putting pressure on the various components - you might be surprised what it loose and rattling.

It's certainly worth a try before spending money or digging into the electronics.

OK, I'll start by checking to see if everything is 100% tight in the cabinet. It should be as I have glued and screwed everything together. except the front baffle which is screwed in.

[Bruce Weldy]

It can be something as small as a speaker wire rattling on the cone or against the cabinet. Hopefully, that's all it is.