EQ required?

ebag4 · « **Reply #20 on:** 7 Apr 2009, 10:55 pm »

Erling,
Thanks very much for the schematic. I agree, it does appear it would be a relativly simply matter to output stereo bass. I wonder why they would not do this in the first place?

Best,
Ed

Rudolf · « **Reply #21 on:** 8 Apr 2009, 09:05 am »

Quote from: irishpatrick33 on 5 Apr 2009, 12:29 pm

... But I have not gotten a defiinitive idea as to whether or not EQ is required? ... So is EQ required? Opinions? Pros cons?

You don´t want to hear a driver without EQ. Most drivers will sound horrible, because they have been designed to work with EQ.
Think about it: Even a plain baffle is an EQ. Boxes are monstrous EQs. The trouble is: Because of a lack of knowledge/understanding people believe caps and coils to be BAD EQ and baffle shapes or driver housings to be GOOD EQ.
Let me explain with a simple example - an Omnes L8 driver on an OB, equalized by electrical means and by acoustical means for (as good as possible and feasable) linear response on axis. I choose the L8 because it is the most OB-friendly wide range driver I know of.

Electrical EQ first - just a coil and a resistor:

Acoustical EQ second - changing the baffle width and horizontal driver position until a "flat" response is achieved:

You see that an almost linear response on axis can be achieved both ways. But with acoustical means only you have to compromise the off-axis response. Only with electrical EQ you will be able to get a linear response regardless of the listening angle (always within the constrains of the driver directivity of course).

You will have noticed that without electrical EQ efficiency is > 3 dB improved. That is the price you have to pay for a better controlled radiation pattern. Nevertheless peak loudness will be equal for both versions - you just need a bit more amplifier power for the first version.

Rudolf

irishpatrick33 · « **Reply #22 on:** 8 Apr 2009, 10:19 am »

Alright let's see if I have comprehended correctly. EQ is absolutely required. However EQ can include baffle design as well. Meaning a baffle with off center driver can compensate for the peak?

I'll explain a bit more of what I am doing. I was planning on building B200 open baffles, but have since abandoned the idea preferring smaller drivers (I'm selling brand new B200s on Ebay). It just worked out this way since I am moving to smaller space.

So I am planning on building EJ Jordan JX92S open baffles. Yes, I know the JX92S Qt is not as favorable as desired (I'm hoping the high X max will compensate 9mm). I am fixated on two flat designs, one circular and the other rectangular.

So for the circular(for example), I can mount the driver 4 inches off center on a baffle with 10 inch diameter and tame the peak enough to not need a seperate component or added circuitry? Likewise for the rectangular design.

Telstar · « **Reply #23 on:** 8 Apr 2009, 11:12 am »

Quote from: Rudolf on 8 Apr 2009, 09:05 am

The trouble is: Because of a lack of knowledge/understanding people believe caps and coils to be BAD EQ and baffle shapes or driver housings to be GOOD EQ.

It's not lack of knowledge nor understanding.
Caps and coils DO sound. Baffles don't. This is the biggest difference.

Obviously a poorly designed driver in a poorly designed baffle will sound better with any kind of EQ, than without because of the peaks and dips.

Rudolf · « **Reply #24 on:** 8 Apr 2009, 02:58 pm »

Quote from: irishpatrick33 on 8 Apr 2009, 10:19 am

Alright let's see if I have comprehended correctly. EQ is absolutely required. However EQ can include baffle design as well. Meaning a baffle with off center driver can compensate for the peak?

Yes, that's what I was saying, but: That way you can only level out the peak for ONE direction. At the same time you will make the peaks and dips worse for other directions. I hope my second example showed that.

Quote

So I am planning on building EJ Jordan JX92S open baffles. ... So for the circular(for example), I can mount the driver 4 inches off center on a baffle with 10 inch diameter and tame the peak enough to not need a seperate component or added circuitry? Likewise for the rectangular design.

Since the JX has an outer diameter of 5.5 inch, you probably will need a 13 inch baffle to mount the driver 4 inches off center. And yes, that should level out the dipole peak on axis sufficiently to 2 dB maximaly . You can simulate it with EDGE quite easily. But don't look to the off-axis response ...

Rudolf · « **Reply #25 on:** 8 Apr 2009, 03:19 pm »

Quote from: Telstar on 8 Apr 2009, 11:12 am

It's not lack of knowledge nor understanding.
Caps and coils DO sound. Baffles don't. This is the biggest difference.

OK, I got it. Just to make sure I understand you right: We both agree that changing baffle dimension/shape etc. and filtering with caps and coils is intended to change the frequency response (sound) of a loudspeaker. But apart from that intended sound "forging" you believe, know or have experienced that caps and coils add an individual sound component (could we call it distortion?), that is not part of the original drivers response.

In that case we will have to agree to disagree. I'm not at all saying that you are wrong. It's just that I never have experienced this. May be I'm plainly deaf to it. But if you hear it to an annoying extent, I certainly understand that you want to do without it.

Rudolf

Kevin Haskins · « **Reply #26 on:** 8 Apr 2009, 03:29 pm »

You can easily design them passive. It is still EQ, just after the amp rather than before it.

I've done it with a dipole design. You loose sensitivity, because you cannot boost (much) with a passive crossover. You can take the entire top-end down to the reference efficiency of the woofers on the baffle though. It is easily possible to do full-range dipole/OB system with passive crossovers that will play from 30Hz-20K. The reference efficiency will be low, set by the efficiency of the woofers on the baffle but the power requirements the same.

Telstar · « **Reply #27 on:** 8 Apr 2009, 03:43 pm »

Quote from: Rudolf on 8 Apr 2009, 03:19 pm

OK, I got it. Just to make sure I understand you right: We both agree that changing baffle dimension/shape etc. and filtering with caps and coils is intended to change the frequency response (sound) of a loudspeaker. But apart from that intended sound "forging" you believe, know or have experienced that caps and coils add an individual sound component (could we call it distortion?), that is not part of the original drivers response.

Yes, added distortion, coloration and depriving the signal of a lot of the carried information.
This is what I have experienced with passive components inserted between the amplifier and the driver (and also elsewhere).

And this is why, I prefer to live with a little edgy response rather than with a cap etc before my speakers.
EQ, If I have to do it, I'd rather do entirely in the digital domain, before the signal becomes analog. Exception being very low frequencies where the human ear (or at least mine) is not so sensitive.