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Boombox Reprise
Built this last year without much attention to proper engineering practices or sound quality aspects. Just a Rat Rod Boombox for the garage.
I decided to upgrade the woofers from the $20 Goldwood 10's to Dayton RSS265HO-4 10", the math says they would work very well with the box volume for the woofers, which is currently 1.87 cu ft. The RSS265HO-4 10" are installed and the box has been vented with 8, 1" ports at 32.5Hz. Subs are driven with a 2x250W IRS2092, +/- 65.8 volt power supply guessing a 300-350 VA transformer it seems to have plenty of current for sane operation.
I was very surprised at the sound quality of these Dayton subs! I had no doubt they would have some punch to them, even relatively low power of the 2x250W IRS2092 feeding them but they SOUND good, not mushy or dull. This is the second time I have bought aluminum cone subs, first time was last year when building the AV subs for the house. Used Rockford Fosgate P2D2-12 this is one of the pair driven with a iNuke 1000 DPS. I think there is something about the use of aluminum for the cones that improves the accuracy of these beastly drivers. Love them but I digress :rolleyes:
During the Dayton RSS265HO-4 sub install I got it in my head to bi-amp this project. No, this is a TRI-AMP the project! (I had plenty of Sure class D boards I bought "just to see" after I was stunned by what the 8 pound iNuke 1000DPS offered up for $299. Still can't believe how light and cool running class D's are).
The mid ranges used are Pyle PDMW6 6-1/2" Mid-Woofers, driven with a 2x100W TDA7498 powered by a 35 volt psu. They are difficult to tame in this application. I say the Pyles are hard to tame because they need more cubic volume than is practical to quell a 5.5 dB spike at ~125Hz and I think I need them smother there to blend with the subs in fact I know I do.
Tweets are Dayton Softies powered by a 2x50W TDA7492 with a 30 vdc PSU. Love them they make me smile and take a pretty good beating. At one time the entire system was powered by the 2x250W IRS2092 and the softies where crossed at 3000 Hz 6dB/ so me thinks they have been scared more than a few times.:eek:
Both the 2x50W TDA7492 and 2x100W TDA7498 run off the same transformer that has two separate 24 v secondary windings, no idea the VA on it but it is pretty stout powers both amps with very little PSU sag. less than 2 vac each secondary.
Signal source is a Dual XR4115 USB/SD Media Receiver from PE that for the money ($45) is pretty good, the EQ is a Lanzar E540P VIBE In-Dash 5-Band Parametric EQ (again from PE) which is okay but the Subwoofer output have a huge hiss issue that did not change after an op-amp swap so for now I try to handle with a 1 uf cap on the output that cuts the hiss but not the answer I know.
I am using passive line level 12dB crossovers right now, the mid is crossed at 150 Hz and the highs cross at 4000Hz. (I tried to use a passive bandpass for the mid range but that was not working so hot so I have a 0.35mH coil on the mids, that has to go, I want nothing between the amps and the drivers.) The sub signal is from that noisy sub output
So that's what make this thing up now for what I don't like about it.
First it was build from 1/2" and 1/4" MDF, I think I am leaving a lot of low frequency energy on the table as it is. The box is sealed pretty well and there are no audible buzzes are rattles at low volume, who knows cranked up, none the less it is substandard for the RSS265HO-4 drivers. That 42" plasma will start walking at medium volume levels so it shakes pretty good right now.
Secondly the Pyle PDMW6 6-1/2" Mid-Woofers while not bad speakers, I have used them before in a couple of 2 way vented boxes and they sound pretty good, but they need cubic volume to accomplish that. So they have to go. (Part of my reasoning for this rebuild it shrinking the entire enclosure from the current 2.28 cubic feet total down to just under 2.0 cubic feet since I can get away with 0.65 cu ft for each RSS265HO-4, vented, 32Hz-34Hz tune.)
Thirdly I did a poor job (remember rat rod mind set here) reasoning though the placement of the unseen electronics, power supplies, soft start, power up / down sequence circuit, fuses. All the little junk I have added since the original build which turned has turned business end of this thing into a hot mess and a nightmare for servicing it. So that needs to change.
Now what I propose is the following changes to the rebuild:
Dispatch the Pyle midrange's and use some Dayton Audio PA130-8 5" Full Range PA Driver. I have four of them one hand and two in quick and dirty 0.3 cu ft boxes tuned to 76 Hz for testing. When crossed at 100Hz with a 18 dB active they blend much better with the subs then the Pyles'. The PA130-8 5" are rated at 50 watts and the 2x100W TDA7498 amp driving them gives 65 watts into 8 ohms (22.5 volts into 8.1 ohm dummy load) but can't see that being an issue. I toyed with the idea of picking up 8 Dayton Audio DS90-8 3" and using 4 per side for mids as they would pretty much match a single PA130-8 5" but I have the PA130-8 5" drivers already and the 3" x 4 pcs configuration take up extra real estate. Assuming the PA130-8 5" make the cut they will each be isolated in their own 0.3 cu ft enclosure tuned to 75 Hz and crossed around 100 Hz to 150Hz, 18dB/.
The same basic overall shape but shaving 4" off the width down to 40" wide, remove 2" of height down to 12" high and add 1.75" of depth to 12" deep. Made totally from 3/4" MDF each side will have 0.95 cu ft. 0.65 for the woofers and 0.3 cu ft for the mid's. Everyone should be happy.
Untangled the hidden electronics!
So far I have placed all the main power supplies (and the 12vdc for the radio and eq) on a single PC board which will help untangle things.
I built a variable speed cooling fan controller, actually two, one to monitor the amps and the other for the power supplies and transformers, those circuits will fit on the psu board and the power has to come from there anyway.
I played with the idea of putting the transformers inside the subwoofer enclosure(s) but I don't know how save that is -or- what it will do to the transformer's life span. They get the job done power wise but they do work hard doing it meaning they get pretty warm under sustained load. The subs will be vented so if someone wants to tell me they can go inside the enclosures please sound off now!
All this plus the radio and eq, two cooling 3" fans need to fit into the available 0.46 cu ft space left over and not look like a hot mess! Ditching the transformers inside would be great but I worry about the heat issue.
The current method of dividing the signal is caveman at best so since PE car audio selection is kind of lacking, I found on Amazon Clarion MCD360 2/3 Way Crossover It will give me what I need for a tri-amp setup plus a few extra buttons to push and knobs to spin. Of course that will also need to be fit into that already packed 0.46 cu ft of space but that's fine.
I have no idea what kind of finish will be applied, that always seems to come to me during the build but I did spy this spray paint that looks kinds of cool, a marble like finish. KRYLON Webbing Spray I found this picture,Webbing Spray, of it applied to a rifle stock. Looks cool enough to grab a couple cans and try it out.
That's all I got for right now. I'll add to the thread when I start making saw dust or have a significant emotional event about the build.
Any comments, suggestions would be great!
A good public mocking is always fun too. :D
Ciao