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-   -   Help with bass response on my first build... (http://www.diyaudio.com/forums/multi-way/236726-help-bass-response-my-first-build.html)

Shaolin23 28th May 2013 03:15 PM

Help with bass response on my first build...
 
Hello All,

I'm in the process of building my first speaker / amp project - a boombox based around a HelderHIFI T2024 MKV.

I used these woofers and these tweeters, with 2khz prebuilt crossovers. Using parts-express "optimum cabinet size" (sealed) I built enclosures at 0.79 feet cubed. The sound quality is quite good, although the bass is far less than I had hoped for, and drops off considerably outside of 1 foot away from the box. I should add that I'm using zobel networks on the woofers with a 10uf cap and a 10 Ohm resistor, plus an L-pad for the tweeters. I added some poly fill to each enclosure last night and didn't notice a huge difference.

Using the this speaker box enclosure designer I get a sealed box size of about 0.25 feet cubed - far less than what I've constructed. This discrepancy seems rather large...have I done some thing horribly wrong with my design? Am I expecting too much out of these cheapo woofers?

Any help would be greatly appreciated. Thanks in advance.

Cal Weldon 28th May 2013 04:37 PM

Moved to Speaker section.

1. The woofers aren't the problem.
2. Your choice of tweeter is suspect.
3. A premade XO is never a good choice, it won't do what you are hoping.

You should have brought this to us before you bought anything.

Shaolin23 28th May 2013 04:47 PM

Well, it's here now :)

Any helpful suggestions at this point would be appreciated.

Thanks.

Shaolin23 28th May 2013 04:53 PM

Well it's here now :)

Like I mentioned, it's my first build and I decided to jump in with both feet. Could you suggest a tweeter which would work better?

Thanks!

picowallspeaker 28th May 2013 04:57 PM

Quote:

Originally Posted by Cal Weldon (Post 3507001)
2. Your choice of tweeter is suspect.

:p:p
It's 100 dB/W/m
against a 88 dB/W/m woofer

You've got to loose 12 dB ( theory ) if not more ( electrical losses such as the coil before the woofer )
And in the end it's not even Hi-fi !

Shaolin23 28th May 2013 05:02 PM

Quote:

Originally Posted by picowallspeaker (Post 3507026)
:p:p
It's 100 dB/W/m
against a 88 dB/W/m woofer

You've got to loose 12 dB ( theory ) if not more ( electrical losses such as the coil before the woofer )
And in the end it's not even Hi-fi !

Perhaps I posted this in the wrong forum - Is there a "new to dyaudio" section where one may ask (arguably stupid) questions, and perhaps receive suggestions?

Thanks in advance.

Shaolin23 28th May 2013 05:23 PM

Would this tweeter be a better fit?


Pioneer FBDD69-51F


3/4" horn loaded dome tweeter.
Ferrofluid cooled

SPECIFICATIONS
Nominal Diameter: 4.0", 102mm
Nominal Impedance: 8 ohms
Power: 45 W rms
Freq. Response: 2 kHz-20 kHz
Sensitivity: 90 db 1w/1m
Magnet Weight: 2.4 oz, 68 grams
Voice Coil Diameter: 0.74", 19mm
Min. X-over: 2 kHz/12dB

boris81 28th May 2013 05:59 PM

There are many aspects to address in a successful speaker design, it's not as simple as connecting components together.

The first thing to match is the speaker sensitivity. However, woofers can lose up to 6dB depending on the box geometry and that needs to be addressed in the crossover as well as by selecting a less sensitive tweeter.
Crossovers a defined by slopes. A 4th order crossover means that your drivers must work for an octave beyond the crossover point. So for example a 4th order XO at 2kHz means that your woofer has to work till 4kHz and your tweeter to 1kHz.

Sadly, I don't think you can do much with what you have already. It's probably best to look at kits with pre-built crossovers and try to emulate the suggested boxes.

Speaker Kits in the Speaker Components Department at Parts Express | 286

Shaolin23 28th May 2013 06:09 PM

Thanks for the response. I'll do a little more reading before jumping in next time.

picowallspeaker 28th May 2013 06:17 PM

Quote:

Originally Posted by Shaolin23 (Post 3507066)
Would this tweeter be a better fit?


Pioneer FBDD69-51F


3/4" horn loaded dome tweeter.
Ferrofluid cooled

SPECIFICATIONS
Nominal Diameter: 4.0", 102mm
Nominal Impedance: 8 ohms
Power: 45 W rms
Freq. Response: 2 kHz-20 kHz
Sensitivity: 90 db 1w/1m
Magnet Weight: 2.4 oz, 68 grams
Voice Coil Diameter: 0.74", 19mm
Min. X-over: 2 kHz/12dB

The 90 dB sensitivity is a better match with the woofer.
The horn loading adds gain at the low end of the tweeter working band ( depending on mouth aperture and geometry of the horn) and as a plus it widens dispersion, which is important at croosver frequency, which dispersion (opposed to directivity, which is an 'issue' for high frequency ) has to meet woofer's own. Indeed, the most important thing is that at crossover frequency there are not abrupt changes with (from) the two different emissions of the two drivers. Me almost newbie :shhh:


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