Who do I believe?

Lewis Moon · 28th October 2008, 01:29 PM

I am trying to design a small sub for my home stereo system to augment the satellite speakers and I have run into a dilemma:

When I get the specs from the Parts express site I get radically different numbers than I get from the manufacturer....leading to really different cab volumes.

These are for a sealed sub using the Dayton RSS210HF-4 driver:

Specs listed on PE:
Fs: 27 Hz
Qts: 0.40
Qes: 0.47
Vas: 1.22 cu. Ft

EBP = 57.5
Vb = 0.5744

Specs listed on the Dayton data sheet:
Fs: 28.3
Qts: 0.50
Qes: 0.60
Vas: 1.144

EBP = 47.2
Vb = 1.15

Thats a difference of roughly 50%!

The numbers from the manufacturer seem a bit more "believable" as the PE numbers would yeild a ~10" cube....which would be sweet but I just can't believe anything that small would work.....I guess not much bracing would be needed.....

richie00boy · 28th October 2008, 01:34 PM

Why don't you email Parts Express? Maybe they looked at the wrong data sheet when building the website. Or maybe they are an off-spec buyout.

Lewis Moon · 28th October 2008, 02:02 PM

I wonder if they are off spec...PE doesn't mention that but the RSS265HF-4 specs differ too.....and both are on sale.

I E-mailed them.

Lewis Moon · 28th October 2008, 03:09 PM

I got an answer from PE. They said that Dayton had recently retested and to use the PDF spec sheets from the Dayton site.

richie00boy · 28th October 2008, 04:25 PM

Now that's customer service!

Lewis Moon · 28th October 2008, 04:51 PM

Yes it was. I'll soon be giving them some money for their trouble.

HK26147 · 28th October 2008, 05:15 PM

Frankly I'd take manufacturers specs as a general, not an exact set of parms.
The only way to be totally sure is to measure the T/S parms. yourself. You will find that they can be off by 15% or more from published. Not so much a problem in a sealed cab, but much more significant in a tuned enclosure.
OEM drivers in general seem to have greater variance vs drivers from the top name drivers.

Lewis Moon · 28th October 2008, 08:10 PM

I'd love to have the means to tune a speaker to a room (objectively).....but that ain't gonna happen, so I'll just take the best data available.

HK26147 · 28th October 2008, 08:44 PM

Actually I was just suggesting running an impedance sweep and calculating the T/S specs.
Today the means to do so is much more reasonable than you may be aware.
I'm sure there are many veteran forum members here that can tell you how to convert a soundcard to a speaker tester. You would have to make a test jig.
Because I got tired of tuning my DIY efforts by ear a long time ago, I made a commitment to get quantitative.
I took the easy ( and more expensive ) route and bought a WTII, because I didn't want to go back to the old fashion chart recording of my youth.

As far as the room goes, the software is available to do RTA freq analysis for free or cheap - you would have to buy or build a capsule mic

28th October 2008, 01:29 PM	#1
Lewis Moon diyAudio Member Join Date: Sep 2008	Who do I believe? I am trying to design a small sub for my home stereo system to augment the satellite speakers and I have run into a dilemma: When I get the specs from the Parts express site I get radically different numbers than I get from the manufacturer....leading to really different cab volumes. These are for a sealed sub using the Dayton RSS210HF-4 driver: Specs listed on PE: Fs: 27 Hz Qts: 0.40 Qes: 0.47 Vas: 1.22 cu. Ft EBP = 57.5 Vb = 0.5744 Specs listed on the Dayton data sheet: Fs: 28.3 Qts: 0.50 Qes: 0.60 Vas: 1.144 EBP = 47.2 Vb = 1.15 Thats a difference of roughly 50%! The numbers from the manufacturer seem a bit more "believable" as the PE numbers would yeild a ~10" cube....which would be sweet but I just can't believe anything that small would work.....I guess not much bracing would be needed.....

28th October 2008, 01:34 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Why don't you email Parts Express? Maybe they looked at the wrong data sheet when building the website. Or maybe they are an off-spec buyout. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

28th October 2008, 04:25 PM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Now that's customer service! __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th October 2008, 02:02 PM	#3
Lewis Moon diyAudio Member Join Date: Sep 2008	I wonder if they are off spec...PE doesn't mention that but the RSS265HF-4 specs differ too.....and both are on sale. I E-mailed them.

28th October 2008, 03:09 PM	#4
Lewis Moon diyAudio Member Join Date: Sep 2008	I got an answer from PE. They said that Dayton had recently retested and to use the PDF spec sheets from the Dayton site.

28th October 2008, 04:51 PM	#6
Lewis Moon diyAudio Member Join Date: Sep 2008	Yes it was. I'll soon be giving them some money for their trouble.

28th October 2008, 05:15 PM	#7
HK26147 diyAudio Member Join Date: Jan 2008	Frankly I'd take manufacturers specs as a general, not an exact set of parms. The only way to be totally sure is to measure the T/S parms. yourself. You will find that they can be off by 15% or more from published. Not so much a problem in a sealed cab, but much more significant in a tuned enclosure. OEM drivers in general seem to have greater variance vs drivers from the top name drivers.

28th October 2008, 08:10 PM	#8
Lewis Moon diyAudio Member Join Date: Sep 2008	I'd love to have the means to tune a speaker to a room (objectively).....but that ain't gonna happen, so I'll just take the best data available.

28th October 2008, 08:44 PM	#9
HK26147 diyAudio Member Join Date: Jan 2008	Actually I was just suggesting running an impedance sweep and calculating the T/S specs. Today the means to do so is much more reasonable than you may be aware. I'm sure there are many veteran forum members here that can tell you how to convert a soundcard to a speaker tester. You would have to make a test jig. Because I got tired of tuning my DIY efforts by ear a long time ago, I made a commitment to get quantitative. I took the easy ( and more expensive ) route and bought a WTII, because I didn't want to go back to the old fashion chart recording of my youth. As far as the room goes, the software is available to do RTA freq analysis for free or cheap - you would have to buy or build a capsule mic

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)