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Multi-Way Conventional loudspeakers with crossovers

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Old 8th September 2011, 12:59 AM   #1
speedie is offline speedie  Australia
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Default disappointment

Disappointment

I have had an interest in speaker building for some time now ,which has progressed from buying kits to build then purchasing books on equations for box design, followed by bass box software and extensive reading from this and other forums
After designing the boxes in bass box checking that I had entered all parameters correctly studying the graphs was convinced that my design was sound

Contracted a cabinet maker and requested a quote for supply of said boxes cut from his CNC machine
Picked up all the parts in flat pack return to my workshop apply egg crate style foam onto the inner surfaces on the panels them glue all parts together and leave under compression as per most of the views that are seen here.

I bought some Danish oil then proceed to apply and hand polish the box which I must say is quite impressive

Yesterday I finished winding the last inductor for the cross over ,then proceeded to fabricate the boards for the rest of the components finally at about 6 pm I hooked up the first completed box and auditioned it to my complete displeasure it was flat and lacked any real bass response

So I unsoldered the driver connections pulled out the crossover card rechecked that my wiring connections were following the correct path and noted that I had placed a wire in the tweeter path that should not have been there

Thinking that this may be the cause of my disappointment quickly unsoldered and placed it where it should have been
This time instead of completely reassembling the box I dry wired the crossover and drivers
Must say the high end was infinitely improved but the bottom still flat no oomph

I tried the bass driver direct off the amp which seemed to lift the response but not excessively as compared to quickly swapping the input lead from the amp from through the crossover then straight onto the driver.

Finally in despair found an old factory bought 2way crossover and used that in a dry wire run which wasn’t too far from the same disappointment.
Too top off my disappointment when I arrived home my oldest daughter had her two bit Chinese JBHI iPod stereo on which has maybe 75mm cube sealed boxes that sounded much more basser that my Chinese built Danish vifa peerlees combination!

So I thought that I would post here and see if anyone has any advise on this matter

Box is a vented style with 22 litre volume port is 75mm tuned to 44Hz
Drivers are peerless nomex 830875 vifa XT25TG-30-04 crossover point is 2000Hz
Using link witz 2Nd order and reverse polarity on the tweeter input
Capacitors are poly bought through wes components
Cheers speedie
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Old 8th September 2011, 01:02 AM   #2
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Hate to state the obvious but reverse the polarity on one of the speakers and report back. Happens to persons even older than me.
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Old 8th September 2011, 01:32 AM   #3
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Default BSC?

You said you used equations, correct?

I'm betting you had no BSC in the design...

Later,
Wolf
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Old 8th September 2011, 01:53 AM   #4
lowpoke is offline lowpoke  Australia
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And let's see some pictures of these babies!
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Last edited by lowpoke; 8th September 2011 at 01:54 AM. Reason: Grammar
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Old 8th September 2011, 01:57 AM   #5
bbggg is offline bbggg  United States
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As far as I can tell, the OP has only put one speaker together, so there must be no polarity issue yet. Speedie, can you measure DC resistance across the LF arm of the crossover? If it is suitably small, as it should be, then maybe try to swap woofers and see what happens. Are you sure woofers and tweeters are level-matched properly? The tweeter should be attenuated by about 3 dB based on sensitivity alone, and then there is a baffle step and DC resistance in the bass section coils to consider. Also, some woofer suspensions often need a few hours of low-level, low bass to loosen up.
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Old 8th September 2011, 02:17 AM   #6
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Well, OK, how did you arrive at a box twice the recommended size and tuned a bit lower? That gives you a depression in the bass area and probably less punch than you want. I calculated using the published specs and got exactly the recommended size box of about .45 ft^3, tuned to 53 Hz. IMO, one should still measure their own drivers, but Peerless is usually very good about specifications. Nice drivers BTW, they remind me of the Dynaudio mid bass units I use for... mid bass. I've built very nice sounding speakers with the Dynaudio parts as the woofers, but in sealed boxes. Since you aren't going that low with that driver no matter what you do, a certain amount of bass peak is required for it to sound good, or build a sub to go with it. Don't be a purist about "flat" response. It's a pitfall to trap the innocent and mislead the faithful.
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Old 8th September 2011, 03:32 AM   #7
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Quote:
Originally Posted by Conrad Hoffman View Post
Don't be a purist about "flat" response. It's a pitfall to trap the innocent and mislead the faithful.
X2
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Old 8th September 2011, 03:57 AM   #8
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Quote:
Originally Posted by speedie View Post
I hooked up the first completed box and auditioned it to my complete displeasure it was flat and lacked any real bass response
Based on Peerless specs, looks like you're fine with 22L.

You won't get bass without some contouring. To get the bass up, insert an inductor and a resistor (see picture below - circled in red) before the crossover. 1.5mH and 4.7 ohms are the values for my SEAS ER18RNX. You will have to use values suitable for your speakers. My inductors range from 1.5mH, 2.0mH, 2.5mH and 3mH. Resistors up to 47 ohms (10 - 20 watts).

You can check out my 2-way at STARLING. It'll give you an idea of passive crossovers.

Quote:
Don't be a purist about "flat" response. It's a pitfall to trap the innocent and mislead the faithful.
Attached Images
File Type: jpg PEERLESS 830875.jpg (78.2 KB, 1950 views)
File Type: gif STARLING XO.gif (12.2 KB, 1926 views)
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Old 8th September 2011, 04:01 AM   #9
CLS is offline CLS  Taiwan
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None of the speaks I've built has a flat response. They tend to be slightly bass heavy by the measurements, which fit my ears better. Measured flat usually sounds too thin compared to the real things.

Oh, dissappointments are constantly happening in this hobby. It's normal. That's why we keep building...

Last edited by CLS; 8th September 2011 at 04:04 AM.
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Old 8th September 2011, 04:29 AM   #10
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Flat Response is for Recording Monitors. A Flat Line makes a perfect reference.

Our ears are not linear like microphones. We are a bit deaf on the treble and a lot more deaf on the bass. A Flat Response speaker will sound "thin" with music. Listen to the venerable Yamaha NS-10M and you'll know what I mean. Sounds awful with music.
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